ArticleLiterature Review

A review of methionine dependency and the role of methionine restriction in cancer growth control and life-span extension

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... Methionine cycle and one-carbon metabolism: linking carbon flux to nutrient status Methionine is an essential amino acid for protein synthesis as well as many biochemical reactions required for cell viability and growth ( Figure 1). S-adenosylmethionine (SAM) is the universal methyl donor for RNA, DNA, and chromatin methylation, and is synthesized from methionine via methionine adenosyltransferase (MAT) in the first step of the methionine cycle ( Figure 2A) [1,2]. MAT I (a tetramer) and MAT III (a dimer) are generally expressed in the liver, where high SAM synthesis occurs, and are encoded by MAT1A, while MAT II (a dimer) is expressed in most other cell types and is encoded by MAT2A [3][4][5]. ...
... SAM is then converted to S-adenosylhomocysteine (SAH) through various transmethylation reactions. SAH is hydrolyzed to homocysteine by SAH hydrolase (AHCY or SAHH), which can then be re-methylated to methionine by methionine synthase (5-methyltetrahydrofolate-homocysteine meth-yltransferase; MTR or MS) or betaine-homocysteine methyltransferase (BHMT) to complete the methionine cycle [1,2]. Alternatively, homocysteine can be diverted into the transsulfuration pathway by cystathionine-β-synthase (CBS) to become cystathionine, which is then converted to cysteine by cystathionase (CTH) for use in glutathione production and maintenance of redox homeostasis [1,3]. ...
... SAH is hydrolyzed to homocysteine by SAH hydrolase (AHCY or SAHH), which can then be re-methylated to methionine by methionine synthase (5-methyltetrahydrofolate-homocysteine meth-yltransferase; MTR or MS) or betaine-homocysteine methyltransferase (BHMT) to complete the methionine cycle [1,2]. Alternatively, homocysteine can be diverted into the transsulfuration pathway by cystathionine-β-synthase (CBS) to become cystathionine, which is then converted to cysteine by cystathionase (CTH) for use in glutathione production and maintenance of redox homeostasis [1,3]. Additionally, SAM is utilized for polyamine synthesis, which produces S-methyl-5'-thioadenosine (MTA) as a byproduct that can then be recycled back to methionine in the methionine salvage pathway [1,3]. ...
Article
Methionine is the initiator amino acid for protein synthesis, the methyl source for most nucleotide, chromatin, and protein methylation, and the carbon backbone for various aspects of the cellular antioxidant response and nucleotide biosynthesis. Methionine is provided in the diet and serum methionine levels fluctuate based on dietary methionine content. Within the cell, methionine is recycled from homocysteine via the methionine cycle, which is linked to nutrient status via one-carbon metabolism. Unlike normal cells, many cancer cells, both in vitro and in vivo, show high methionine cycle activity and are dependent on exogenous methionine for continued growth. However, the molecular mechanisms underlying the methionine dependence of diverse malignancies are poorly understood. Methionine deprivation initiates widespread metabolic alterations in cancer cells that enable them to survive despite limited methionine availability, and these adaptive alterations can be specifically targeted to enhance the activity of methionine deprivation, a strategy we have termed "metabolic priming". Chemotherapy-resistant cell populations such as cancer stem cells, which drive treatment-resistance, are also sensitive to methionine deprivation, suggesting dietary methionine restriction may inhibit metastasis and recurrence. Several clinical trials in cancer are investigating methionine restriction in combination with other agents. This review will explore new insights into the mechanisms of methionine dependence in cancer and therapeutic efforts to translate these insights into enhanced clinical activity of methionine restriction in cancer.
... These defective cancer cells are unable to regenerate methionine via these pathways. 21 A byproduct of polyamine synthesis is methylthioadenosine (MTA). MTA is broken down by the enzyme, methylthioadenosine phosphorylase (MTAP) and is a step in the salvage of methionine. ...
... 25 Loss of MTAP expression is observed in many cell lines including TNBC 26 and MTAP is involved in polyamine synthesis from methionine. 21 The MTAP gene encodes an enzyme involved in polyamine metabolism. Cancers that lose MTAP expression need methionine and fail to grow when deprived of it. ...
... [26][27][28] Loss of MTAP expression from the methionine salvage pathway is a major factor of methionine dependence in cancer and MTAP itself may act as a tumor suppressor. 21 A RNA sequencing study of 17 breast cancer patients (6 TNBC), found one of the most commonly expressed genetic variation (single nucleotide polymorphism or novel SNP) to be a novel missense variant in previously linked breast cancer gene, MTAP (p.K71R). 29 A study using fresh human breast tumors found the more aggressive TNBC has less MTAP expression than Luminal -A hormone positive breast tumours 30 and the authors concluded; "the observation suggests that this class of patients could benefit from treatment with antimetabolites." ...
Article
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We reviewed the research into the mechanisms of growth of triple negative breast cancer (TNBC) based on laboratory pre-clinical studies that have shaped understanding of the disease over the past decade. In response to these findings, we propose an approach to potentially prevent cancer metabolic adaptation and recurrence. This paper collates pre-clinical results, first to determine the tumor’s mechanisms of growth and then to source natural substances that could potentially suppress those mechanisms. The results from in vivo and in vitro studies of TNBC were combined first to select 10 primary mechanisms (Hypoxia-inducible factor 1α, Hedgehog, MAPK, MTAP, NF-κ B, Notch, P13K, STAT3, and Wnt signaling pathways plus p53 and POL2A gene expression) that promote TNBC growth, and second to propose a treatment array of 21 natural compounds that suppress laboratory models of TNBC via these mechanisms. We included BRCA mutations in the review process, but only pathways with the most preclinical studies utilizing natural products were included. Then we outlined potential biomarkers to assess the changes in the micro-environment and monitor biochemical pathway suppression. This suppression-centric aim targets these mechanisms of growth with the goal of potentially halting tumor growth and preventing cancer cell metabolic adaptation. We chose TNBC to demonstrate this 5-step strategy of supplementary therapy, which may be replicated for other tumor types.
... However, tumour cells and immortalized cells often show so-called methionine dependency. These cells have lost the ability to regenerate methionine and consequently cysteine from intermediates and are dependent on extracellular supply [23,24]. For this reason, the L929 cell line was analysed for its potential to compensate for the missing amino acids using the precursors DL-homocysteine, SAM, and D-and L-homoserine under MetR and CysR by self-synthesis. ...
... This type of analysis was performed for amino acids (except cysteine), the urea cycle, the TCA cycle, carbohydrates, pyrimidines, and purines in both cell extracts ( Figure 2a) and media ( Figure 2b). quently cysteine from intermediates and are dependent on extracellular supply [23,24]. For this reason, the L929 cell line was analysed for its potential to compensate for the missing amino acids using the precursors DL-homocysteine, SAM, and D-and L-homoserine under MetR and CysR by self-synthesis. ...
... In the next experiment, we analysed the potentials of homocysteine and SAM to compensate for the corresponding AR. In some cases, tumour cells offer the advantage that they lose the ability to regenerate methionine from homocysteine and thus become more vulnerable [23,33]. The reverse synthesis of methionine from cysteine/homoserine in the human organism is described in the literature as fundamentally not possible [18]. ...
Article
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Methionine restriction (MetR) is an efficient method of amino acid restriction (AR) in cells and organisms that induces low energy metabolism (LEM) similar to caloric restriction (CR). The implementation of MetR as a therapy for cancer or other diseases is not simple since the elimination of a single amino acid in the diet is difficult. However, the in vivo turnover rate of cysteine is usually higher than the rate of intake through food. For this reason, every cell can enzymatically synthesize cysteine from methionine, which enables the use of specific enzymatic inhibitors. In this work, we analysed the potential of cysteine restriction (CysR) in the murine cell line L929. This study determined metabolic fingerprints using mass spectrometry (LC/MS). The profiles were compared with profiles created in an earlier work under MetR. The study was supplemented by proliferation studies using D-amino acid analogues and inhibitors of intracellular cysteine synthesis. CysR showed a proliferation inhibition potential comparable to that of MetR. However, the metabolic footprints differed significantly and showed that CysR does not induce classic LEM at the metabolic level. Nevertheless, CysR offers great potential as an alternative for decisive interventions in general and tumour metabolism at the metabolic level.
... We observed that participants with higher levels of serum methionine, methioninesulfoxide, and TCA were at increased risk for developing HCC. Methionine is an essential amino acid that plays a role in several key pathways such as protein synthesis and DNA methylation [27]. In normal everyday processes, methionine is either used for protein synthesis or converted to S-adenosylmethionine (SAM) where it is further used for DNA methylation, protein methylation, or as a component of homocysteine, cysteine, taurine, and adenosine monophosphate [27]. ...
... Methionine is an essential amino acid that plays a role in several key pathways such as protein synthesis and DNA methylation [27]. In normal everyday processes, methionine is either used for protein synthesis or converted to S-adenosylmethionine (SAM) where it is further used for DNA methylation, protein methylation, or as a component of homocysteine, cysteine, taurine, and adenosine monophosphate [27]. Several cancer types have been shown to be dependent on methionine or have deficiency in methionine conversion. ...
... Several cancer types have been shown to be dependent on methionine or have deficiency in methionine conversion. Cancer cells that are deficient in these pathways are unable to regenerate methionine in either the de novo or salvage pathways, making them dependent on methionine [27]. Several animal studies have shown a diet that is restricted in methionine is protective against cancer growth [28]. ...
Article
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Background Hepatocellular carcinoma (HCC) is rapidly increasing in the U.S. and is a leading cause of mortality for patients with cirrhosis. Discovering novel biomarkers for risk stratification of HCC is paramount. We examined biomarkers of the gut-liver axis in a prospective multicenter cohort.Methods Patients with cirrhosis without a history of HCC were recruited between May 2015 and March 2020 and prospectively followed at 3 tertiary care hospitals in Los Angeles. Microbiome analysis was performed on duodenal biopsies and metabolomic analysis was performed on serum samples, collected at the time of enrollment. Optimal microbiome-based survival analysis and Cox proportional hazards regression analysis were used to determine microbiota and metabolite associations with HCC development, respectively.ResultsA total of 227 participants with liver cirrhosis contributed a total of 459.58 person-years of follow-up, with 14 incident HCC diagnoses. Male sex (HR = 7.06, 95% CI = 1.02–54.86) and baseline hepatic encephalopathy (HE, HR = 4.65, 95% CI = 1.60–13.52) were associated with developing HCC over follow-up. Adjusting for age, sex, baseline HE, and alkaline phosphatase, an increased risk of HCC were observed for participants with the highest versus lowest three quartiles for duodenal Alloprevotella (HR = 3.22, 95% CI = 1.06–9.73) and serum taurocholic acid (HR = 6.87, 95% CI = 2.32–20.27), methionine (HR = 9.97, 95% CI = 3.02–32.94), and methioninesulfoxide (HR = 5.60, 95% CI = 1.84–17.10). Being in the highest quartile for Alloprevotella or methionine had a sensitivity and specificity for developing HCC of 85.71% and 60.56%, respectively, with an odds ratio of 10.92 (95% CI = 2.23–53.48).Conclusion Alloprevotella and methionine, methioninesulfoxide, and taurocholic acid predicted future HCC development in a high-risk population of participants with liver cirrhosis.
... DNA methylation requires S-adenosyl methionine (SAM) as a methyl donor for which methionine represents the immediate metabolic precursor. Dependency to methionine, also called methionine dependency, is a metabolic adaptation that occurs in association with cancerous transformation, and its interaction with epigenetic modifications is increasingly recognized as a driver of tumorigenesis [2,4,[6][7][8]. In this context, epigenetic modifications have been hypothesized as key drivers for tumor aggressiveness, with resistant phenotype to conventional chemo-and radiotherapy and an ability to develop metastases [5]. ...
... Moreover, no work has systematically evaluated the impact of IRs at a nucleotide resolution level using a standardized protocol of fractionated irradiation using multiple cancerous cell lines. In addition, no data have been reported regarding specific epigenome signatures, considering the methionine dependency phenotype, which represents a hallmark of metabolic adaptation in cancer [6][7][8]. ...
... Second, we developed the EpiMet project to assess the influence of the methionine dependency phenotype on the effect of IRs on the DNA methylome landscape. Methionine dependency is defined as the 'inability of cells to grow when methionine is replaced in culture medium by its metabolic precursor homocysteine' [6]. According to this definition, establishing a methionine dependency phenotype is possible through in vitro testing using cell culture models and methionine-free culture media. ...
Article
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Background Although radiation therapy represents a core cancer treatment modality, its efficacy is hampered by radioresistance. The effect of ionizing radiations (IRs) is well known regarding their ability to induce genetic alterations; however, their impact on the epigenome landscape in cancer, notably at the CpG dinucleotide resolution, remains to be further deciphered. In addition, no evidence is available regarding the effect of IRs on the DNA methylome profile according to the methionine dependency phenotype, which represents a hallmark of metabolic adaptation in cancer. Methods We used a case–control study design with a fractionated irradiation regimen on four cancerous cell lines representative of HCC (HepG2), melanoma (MeWo and MeWo-LC1, which exhibit opposed methionine dependency phenotypes), and glioblastoma (U251). We performed high-resolution genome-wide DNA methylome profiling using the MethylationEPIC BeadChip on baseline conditions, irradiated cell lines (cumulative dose of 10 Gy), and non-irradiated counterparts. We performed epigenome-wide association studies to assess the effect of IRs and methionine-dependency-oriented analysis by carrying out epigenome-wide conditional logistic regression. We looked for epigenome signatures at the locus and single-probe (CpG dinucleotide) levels and through enrichment analyses of gene ontologies (GO). The EpiMet project was registered under the ID#AAP-BMS_003_211. Results EWASs revealed shared GO annotation pathways associated with increased methylation signatures for several biological processes in response to IRs, including blood circulation, plasma membrane-bounded cell projection organization, cell projection organization, multicellular organismal process, developmental process, and animal organ morphogenesis. Epigenome-wide conditional logistic regression analysis on the methionine dependency phenotype highlighted several epigenome signatures related to cell cycle and division and responses to IR and ultraviolet light. Conclusions IRs generated a variation in the methylation level of a high number of CpG probes with shared biological pathways, including those associated with cell cycle and division, responses to IRs, sustained angiogenesis, tissue invasion, and metastasis. These results provide insight on shared adaptive mechanisms of the epigenome in cancerous cell lines in response to IR. Future experiments should focus on the tryptic association between IRs, the initiation of a radioresistance phenotype, and their interaction with methionine dependency as a hallmark of metabolic adaptation in cancer. Graphical abstract
... But normal human cells can survive under methionine restriction. In the case of methionine deficiency, 50% homocysteine is converted to methionine by the enzyme methionine synthase using vitamin B12 (methylcobalamin) and 5methyltetrahydrofolate (5-MTHF) as cofactors (Cavuoto & Fenech, 2012;Chaturvedi et al., 2018). Homocysteine can be converted to methionine in the liver by Betaine-homocysteine Smethyltransferase (Cavuoto & Fenech, 2012;Chaturvedi et al., 2018;Sunden et. ...
... In the case of methionine deficiency, 50% homocysteine is converted to methionine by the enzyme methionine synthase using vitamin B12 (methylcobalamin) and 5methyltetrahydrofolate (5-MTHF) as cofactors (Cavuoto & Fenech, 2012;Chaturvedi et al., 2018). Homocysteine can be converted to methionine in the liver by Betaine-homocysteine Smethyltransferase (Cavuoto & Fenech, 2012;Chaturvedi et al., 2018;Sunden et. al., 1997). ...
... Methionine restricted diet provides quick and cost-effective way to decrease methionine level in the body. Vegan diet provides relatively lowmethionine foods including plant based proteins, vegetables, fruits etc. Cancer patients must avoid animal based foods, especially egg, meat, milk and dairy products (Cavuoto and Fenech, 2012). Maintaining vegan diet may be successful strategy for selectively killing cancer cells. ...
Conference Paper
Methionine is an essential amino acid obtained through diet. Methionine addiction of cancer cells provides promising treatment methods. When plasma methionine levels drop, methionine-dependent cancer cells can no longer survive and eventually die or proliferation slows down. Normal body cells can produce their own methionine with the enzyme methionine synthase during methionine deficiency. This enzyme converts homocysteine to methionine using vitamin B12 and 5-methyltetrahydrofolate as cofactors. Homocysteine can also be converted to methionine in the liver. However, cancer cells have metabolic failure to convert homocysteine to methionine. Therefore, cancer cells always have to take methionine from the blood plasma. This metabolic disorder is called as the "Hoffmann effect". For cancer patients, a methionine-restricted diet can reduce methionine levels in the body and help the death of methionine-dependent cancer cells or slow proliferation of them. It may also help keep cancer cells more responsive to chemotherapy, radiotherapy, or other treatments. Vegan meals have low levels of methionine amino acids. Combining a methionine-restricted diet with other cancer treatments may be beneficial in clinical settings. In this study it was aimed to reveal the efficacy of methionine-restricted diet in cancer treatment by literature research.
... Although methionine is essential per se, individual body cells can regenerate the required methionine via different metabolic pathways, e.g., from SAM or homocysteine. Tumours have often lost this ability and are therefore dependent on an external (extracellular) supply of methionine, which describes another advantage of MetR as a therapeutic approach [17,18]. ...
... An increase in SAM could indicate the general storage of more or less methionine. SAM is so important that it can be converted into various metabolic forms, including methionine [17]. The presence of creatinine might indicate an increased recovery of ATP from oxidative phosphorylation. ...
Article
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Since Otto Warburg reported in 1924 that cancer cells address their increased energy requirement through a massive intake of glucose, the cellular energy level has offered a therapeutic anticancer strategy. Methionine restriction (MetR) is one of the most effective approaches for inducing low-energy metabolism (LEM) due to the central position in metabolism of this amino acid. However, no simple in vitro system for the rapid analysis of MetR is currently available, and this study establishes the murine cell line L929 as such a model system. L929 cells react rapidly and efficiently to MetR, and the analysis of more than 150 different metabolites belonging to different classes (amino acids, urea and tricarboxylic acid cycle (TCA) cycles, carbohydrates, etc.) by liquid chromatography/mass spectrometry (LC/MS) defines a metabolic fingerprint and enables the identification of specific metabolites representing normal or MetR conditions. The system facilitates the rapid and efficient testing of potential cancer therapeutic metabolic targets. To date, MS studies of MetR have been performed using organisms and yeast, and the current LC/MS analysis of the intra- and extracellular metabolites in the murine cell line L929 over a period of 5 days thus provides new insights into the effects of MetR at the cellular metabolic level.
... Beyond this function, methionine also contributes to essential metabolic pathways including polyamine synthesis, maintenance of the redox status and control of protein synthesis [34]. Interestingly, while untransformed tissues are able to sustain exogenous methionine depletion, tumor cells can become dependent on methionine availability [35]. Taking advantage of this therapeutic window, several approaches targeting methionine metabolism are under investigation, for instance by altering the dietary methionine intake [34,35]. ...
... Interestingly, while untransformed tissues are able to sustain exogenous methionine depletion, tumor cells can become dependent on methionine availability [35]. Taking advantage of this therapeutic window, several approaches targeting methionine metabolism are under investigation, for instance by altering the dietary methionine intake [34,35]. Dietary methionine restriction has been also suggested to increase sensitivity to certain cytotoxic agents, such as cisplatin and doxorubicin [36]. ...
Article
Tumor cells typically enhance their metabolic capacity to sustain their higher rate of growth and proliferation. One way to elevate the nutrient intake into cancer cells is to increase the expression of genes encoding amino acid transporters, which may represent targetable vulnerabilities. Here, we study the regulation and function of the broad amino acid transporter SLC6A14 in combination with metabolic stress, providing insights into an uncharacterized aspect of the transporter activity. We analyze the pattern of transcriptional changes in a panel of breast cancer cell lines upon metabolic stress and found that SLC6A14 expression levels are increased in the absence of methionine. Methionine deprivation, which can be achieved via modulation of dietary methionine intake in tumor cells, in turn leads to a heightened activation of the AMP-activated kinase (AMPK) in SLC6A14-deficient cells. While SLC6A14 genetic deficiency does not have a major impact on cell proliferation, combined depletion of AMPK and SLC6A14 leads to an increase in apoptosis upon methionine starvation, suggesting that combined targeting of SLC6A14 and AMPK can be exploited as a therapeutic approach to starve tumor cells.
... Methionine metabolism has been connected to cancer at several levels and indeed numerous studies have revealed that while normal cells do not suffer from methionine deficiency since they possess the ability to grow on homocysteine, one of methionine metabolic precursor, in the same conditions, most cancer cells cannot proliferate [58]. Methionine dependence is a general metabolic defect of cancer and has been attributed to a combination of molecular events, including deletions, polymorphisms or alterations in the expression of genes in the methionine de novo and salvage pathways [58,59]. These observations have highlighted methionine depletion as a tumor-specific therapeutic strategy. ...
... In vivo experi-ments proved the efficacy of MGL, alone or in combination with other chemotherapeutics like vincristine, 5fluorouracil, and cisplatin, as a molecule with great potential for cancer therapy of numerous tumors (i.e. glioblastoma, neuroblastoma, melanoma, colon cancer, lung cancer, brain cancer and prostate cancer) [59,[65][66][67][68]. With the aim to improve the therapeutic properties of the enzyme, MGL from C. freundii was engineered by site-saturation mutagenesis. ...
Article
The development of safe and efficacious enzyme-based human therapies has increased greatly in the last decades, thanks to remarkable advances in the understanding of the molecular mechanisms responsible for different diseases, and the characterization of the catalytic activity of relevant exogenous enzymes that may play a remedial effect in the treatment of such pathologies. Several enzyme-based biotherapeutics have been approved by FDA (the U.S. Food and Drug Administration) and EMA (the European Medicines Agency) and many are undergoing clinical trials. Apart from enzyme replacement therapy in human genetic diseases, which is not discussed in this review, approved enzymes for human therapy find applications in several fields, from cancer therapy to thrombolysis and the treatment, e.g., of clotting disorders, cystic fibrosis, lactose intolerance and collagen-based disorders. The majority of therapeutic enzymes are of microbial origin, the most convenient source due to fast, simple and cost-effective production and manipulation. The use of microbial recombinant enzymes has broadened prospects for human therapy but some hurdles such as high immunogenicity, protein instability, short half-life and low substrate affinity, still need to be tackled. Alternative sources of enzymes, with reduced side effects and improved activity, as well as genetic modification of the enzymes and novel delivery systems are constantly searched. Chemical modification strategies, targeted- and/or nanocarrier-mediated delivery, directed evolution and site-specific mutagenesis, fusion proteins generated by genetic manipulation are the most explored tools to reduce toxicity and improve bioavailability and cellular targeting. This review provides a description of exogenous enzymes that are presently employed for the therapeutic management of human diseases with their current FDA/EMA-approved status, along with those already experimented at the clinical level and potential promising candidates.
... According to the literature, such processes occur in methionine-dependent tumors, including prostate cancer, lung cancer, fibrosarcoma, melanoma [21], breast cancer [44]. In listed above tumor cells, that are sensitive to Lmethionine deficiency, the reduced level of MS and MTAP expression [45], as well as disrupted folate metabolism is observed. The methionine dependence was also found in the primary culture of tumors taken from patients [46,47]. ...
... But most cancer cells cannot proliferate when methionine is replaced with homocysteine, while non-cancer Cell Biochemistry and Biophysics cells are indifferent to such replacement. The inability of tumor cells to maintain a sufficient level of methylation in a methionine-free homocysteine-enriched medium proves the need for exogenous methionine [45]. It indicates that methionine and folate restriction may inhibit cancer cell growth and may enhance the efficacy of chemotherapeutic agents. ...
Article
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This paper investigates the redistribution of metabolic fluxes in the cell with altered activity of S-adenosylmethionine decarboxylase (SAMdc, EC: 4.1.1.50), the key enzyme of the polyamine cycle and the common target for antitumor therapy. To address these goals, a stoichiometric metabolic model was developed that includes five metabolic pathways: polyamine, methionine, methionine salvage cycles, folic acid cycle, and the pathway of glutathione and taurine synthesis. The model is based on 51 reactions involving 57 metabolites, 31 of which are internal metabolites. All calculations were performed using the method of Flux Balance Analysis. The outcome indicates that the inactivation of SAMdc results in a significant increase in fluxes through the methionine, the taurine and glutathione synthesis, and the folate cycles. Therefore, when using therapeutic agents inactivating SAMdc, it is necessary to consider the possibility of cellular tumor metabolism reprogramming. S-adenosylmethionine affects serine methylation and activates serine-dependent de novo ATP synthesis. Methionine-depleted cell becomes methionine-dependent, searching for new sources of methionine. Inactivation of SAMdc enhances the transformation of S-adenosylmethionine to homocysteine and then to methionine. It also intensifies the transsulfuration process activating the synthesis of glutathione and taurine. Keywords: metabolic flux; S-adenosylmethionine decarboxylase; stoichiometric model; polyamine metabolism; flux balance analysis; cancer cell. Full-text view-only version: https://rdcu.be/b8nAS
... 9,10 Some recent studies have suggested that a low-methionine diet may help starve cancer cells and may also extend a healthy lifespan. 9,11 Although methionine deficiency can produce unpleasant symptoms, consuming excessive levels of amino acids can produce adverse consequences as well. 2,10 Reports on methionine-containing compounds are scarce in the literature. ...
Article
A quinoline-based Schiff base sensor, 6-methyl-2-oxo-1,2-dihydro-quinoline-3-carboxaldehyde-4(N)-phenylsemicarbazone (6MPS), has been developed for selective sensing of methionine and aspartic acid in aqueous medium through "on-off-on" type selective detection of copper ion. Fluorescence imaging of 6MPS, 6MPSC, 6MPSCN, 6MPSC-met, 6MPSCN-met, 6MPSC-asp and 6MPSCN-asp has been successfully demonstrated, in which the sensing probes 6MPSC-met, 6MPSCN-met, 6MPSC-asp and 6MPSCN-asp displayed bright green fluorescence in both in vitro and in vivo live cells.
... In the process of layering on HNT, the acidic agent of Met binds to the NH 2 group of APTES molecule, which grafted on the surface of HNT, and the resulting nanocomposite will have a positive effect on drug loading and release of PHT. The use of amino acids, such as Met, is a novel approach to modifying HNT surfaces [38]. ...
Article
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In this study, a novel promising approach for the fabrication of Halloysite nanotube (HNT) nanocomposites, based on the amino acid named Methionine (Met), was investigated. For this purpose, Met layered on the outer silane functionalized surface of HNT for controlled release of Phenytoin sodium (PHT). The resulting nanocomposite (MNT-g-Met) was characterized by FTIR, XRD, Zeta potential, TGA, TEM and FE-SEM. The FT-IR results showed APTES and Met peaks, which proved the modification of the HNTs. The zeta-potential results showed the interaction between APTES (+53.30) and Met (+38.80) on the HNTs (−30.92). The FE-SEM micrographs have displayed the grafting of Met on the modified HNTs due to the nanotube conversion to a rough and indistinguishable form. The amount of encapsulation efficiency (EE) and loading efficiency (LE) of MNT-g-Met was 74.48% and 37.24%, while pure HNT was 57.5%, and 28.75%, respectively. In-vitro studies showed that HNT had a burst release (70% in 6 h) in phosphate buffer while MNT-g-Met has more controlled release profile (30.05 in 6 h) and it was found to be fitted with the Korsmeyer-Peppas model. Due to the loading efficiency and controlled release profile, the nanocomposite promote a good potential for drug delivery of PHT.
... Methionine dependency of tumor cells might result from diminished histone methylation, antioxidant mechanisms and altered epigenetic modifications of tumor cells. Enzymatic depletion of methionine in various cancers like primary ductal carcinoma, melanoma, glioma, osteosarcoma, ALL, non-small lung cancer and glioblastoma was seen to cause cell cycle arrest in late S/G2 phase (Cavuoto and Fenech, 2012). Methioninase is present in Eubacteria like Aeromonas sp., Clostridium sporogenes, Pseudomonas putida, Brevibacterium linens, as well as in Archaebacteria, fungi, protists and plants. ...
Article
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Biopharmaceuticals is a rapidly emerging field that explores and employs biological organisms and their products for therapeutic applications. Enzymes are remarkable biocatalysts that accelerate the rate of biochemical reactions manifold. They possess several extraordinary features like immense catalytic potential, high substrate specificity as well as pH and temperature optima. Due to these extraordinary attributes, they find diverse clinical applications. They are being increasingly employed for the treatment of a wide spectrum of diseases, either alone or in combination with other therapies. Functional enzymes can be isolated from plants, animals or microorganisms. Enzymes originally isolated from microbes offer diverse advantages including ease of isolation, high consistency, higher yields, economic feasibility, high stability and candid production via recombinant DNA technology using microbes as host cells. Also the processes of product modification as well as optimization are easier for microbial enzymes as compared to those obtained from animals and plants. Thus microbial enzymes display enthralling features and opportunities, and form an important subclass of modern biopharmaceuticals. In this review, we focus on the curative potential of microbial enzymes including enzybiotics, digestive aids, anti-inflammatory, anti-cancer and fibrinolytic agents. This information will help to highlight and further explore their therapeutic potential which is fast gaining popularity and assisting healthcare.
... This dual role is thought to be attributable to folate's function of providing methyl-groups for the biosynthesis of nucleotides (purines and thymidylate) required for DNA synthesis in rapidly proliferating tissues [37,38]. Given their high proliferation rate, cancer cells might also have a large demand for choline, which is a precursor for the synthesis of cell membrane phospholipids [39,40], and methionine for protein synthesis [41]; both mechanisms are essential for cell development and functioning. Therefore, the amount and timing of intake could be crucial in cancer development. ...
Article
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(1) Background: Methyl-group donors (MGDs), including folate, choline, betaine, and methionine, may influence breast cancer (BC) risk through their role in one-carbon metabolism; (2) Methods: We studied the relationship between dietary intakes of MGDs and BC risk, adopting data from the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort; (3) Results: 318,686 pre- and postmenopausal women were followed between enrolment in 1992–2000 and December 2013–December 2015. Dietary MGD intakes were estimated at baseline through food-frequency questionnaires. Multivariable Cox proportional hazards regression models were used to quantify the association between dietary intake of MGDs, measured both as a calculated score based on their sum and individually, and BC risk. Subgroup analyses were performed by hormone receptor status, menopausal status, and level of alcohol intake. During a mean follow-up time of 14.1 years, 13,320 women with malignant BC were identified. No associations were found between dietary intakes of the MGD score or individual MGDs and BC risk. However, a potential U-shaped relationship was observed between dietary folate intake and overall BC risk, suggesting an inverse association for intakes up to 350 µg/day compared to a reference intake of 205 µg/day. No statistically significant differences in the associations were observed by hormone receptor status, menopausal status, or level of alcohol intake; (4) Conclusions: There was no strong evidence for an association between MGDs involved in one-carbon metabolism and BC risk. However, a potential U-shaped trend was suggested for dietary folate intake and BC risk. Further research is needed to clarify this association.
... Down-regulation of methionine may indicate increased protein biosynthesis in cancer cells. Since methionine also plays a role in DNA methylation by providing methyl groups, overconsumption of methionine for protein biosynthesis may cause overall DNA hypomethylation, which could reduce DNA stability and trigger CRC development [37,38]. Compared to the non-neoplastic controls, CRC patients normally have lower methionine levels both in serum [28] and urine [25], but higher levels in tissues [21]. ...
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Background: Metabolomics has demonstrated its potential in the early diagnosis, drug safety evaluation and personalized toxicology research of various cancers. Objectives: We aim to screen for potential diagnostic and capecitabine-related adverse effect (CRAE) biomarkers from urinary endogenous metabolites in Chinese colorectal cancer (CRC) patients. Methods: The metabolic profiles of 139 CRC patients and 50 non-neoplastic controls were analyzed using ultra-high-performance liquid chromatography combined with quadrupole time-of-flight mass spectrometry. Results: There were 41 metabolites identified between the CRC patients and the non-neoplastic controls, and 19 metabolites were identified between CRC patients with and without CRAE. Based on these identified metabolites, bioinformatic analysis and prediction model construction were completed. Most of these differential metabolites have important roles in cell proliferation and differentiation and the immune system. Based on binary logistic regression, a CRC prediction model, composed of 3-methylhistidine, N-heptanoylglycine, N1,N12-diacetylspermine and hippurate, was established, with an area under curve (AUC) of 0.980 (95% CI: 0.953-1.000; sensitivity: 94.3%; specificity: 92.0%) in the training set, and an AUC of 0.968 (95% CI: 0.933-1.000; sensitivity: 89.9%; specificity: 92.0%) in the testing set. In addition, methionine and 4-pyridoxic acid can be combined to predict hand foot syndrome, with an AUC of 0.884; ubiquinone-1 and 4-pyridoxic acid can be combined to predict anemia, with an AUC of 0.889; and 5-acetamidovalerate and 3,4-methylenesebacic acid can be combined to predict neutropenia, with an AUC of 0.882. Conclusion: The profiling of urine polar metabolites has great potential in the early detection of CRC and the prediction of CRAE.
... Here, we found an increase in glycolysis and a decrease in the superpathway of methionine degradation in KCNK3-knockdown hPAECs, indicating that the loss of expression of KNCK3 facilitates the glycolysis metabolic shift of hPAECs. In most cancers, enzymes responsible for the Methionine (Met) cycle are altered [48]. Met is also crucial for RNA and protein synthesis, and polyamine [49]. ...
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The physiopathology of pulmonary arterial hypertension (PAH) is characterized by pulmonary artery smooth muscle cell (PASMC) and endothelial cell (PAEC) dysfunction, contributing to pulmonary arterial obstruction and PAH progression. KCNK3 loss of function mutations are responsible for the first channelopathy identified in PAH. Loss of KCNK3 function/expression is a hallmark of PAH. However, the molecular mechanisms involved in KCNK3 dysfunction are mostly unknown. To identify the pathological molecular mechanisms downstream of KCNK3 in human PASMCs (hPASMCs) and human PAECs (hPAECs), we used a Liquid Chromatography-Tandem Mass Spectrometry-based proteomic approach to identify the molecular pathways regulated by KCNK3. KCNK3 loss of expression was induced in control hPASMCs or hPAECs by specific siRNA targeting KCNK3. We found that the loss of KCNK3 expression in hPAECs and hPASMCs leads to 326 and 222 proteins differentially expressed, respectively. Among them, 53 proteins were common to hPAECs and hPASMCs. The specific proteome remodeling in hPAECs in absence of KCNK3 was mostly related to the activation of glycolysis, the superpathway of methionine degradation, and the mTOR signaling pathways, and to a reduction in EIF2 signaling pathways. In hPASMCs, we found an activation of the PI3K/AKT signaling pathways and a reduction in EIF2 signaling and the Purine Nucleotides De Novo Biosynthesis II and IL-8 signaling pathways. Common to hPAECs and hPASMCs, we found that the loss of KCNK3 expression leads to the activation of the NRF2-mediated oxidative stress response and a reduction in the interferon pathway. In the hPAECs and hPASMCs, we found an increased expression of HO-1 (heme oxygenase-1) and a decreased IFIT3 (interferon-induced proteins with tetratricopeptide repeats 3) (confirmed by Western blotting), allowing us to identify these axes to understand the consequences of KCNK3 dysfunction. Our experiments, based on the loss of KCNK3 expression by a specific siRNA strategy in control hPAECs and hPASMCs, allow us to identify Int. Int. J. Mol. Sci. 2020, 21, 7400 2 of 21 differences in the activation of several signaling pathways, indicating the key role played by KCNK3 dysfunction in the development of PAH. Altogether, these results allow us to better understand the consequences of KCNK3 dysfunction and suggest that KCNK3 loss of expression acts in favor of the proliferation and migration of hPASMCs and promotes the metabolic shift and apoptosis resistance of hPAECs.
... The pathways involving methionine and cysteine metabolism, C5-branched dibasic acid metabolism, fatty acid biosynthesis and glycosyltransferases were depleted in patients with malignant disease. Intriguingly, methionine dependence is a common metabolic defect in many cancers and it has been proposed that cancer progression can be reversed by depleting methionine with a methionine-restricted diet or methioninase [36,37]. Thus, the results indicated that the breast microbiota may also be involved in breast carcinogenesis by modulating the biological pathways of the host. ...
Preprint
One in eight women will be diagnosed with breast cancer (BC) in their lifetime, resulting in over 2 million cases annually. BC is the most common cancer among women. Unfortunately, the etiology of majority of cases remains unknown. Recently, evidence has shown that the human microbiota plays an important role in health and disease. Intriguingly, studies have revealed the presence of microorganisms in human breast tissue, which was previously presumed to be sterile. Next-generation sequencing technologies have paved way for the investigation of breast microbiota, uncovering bacterial signatures that are associated with BC. Some of the bacterial species were found to possess pro-carcinogenic and/or anti-carcinogenic properties, suggesting that the breast microbiota has potentially crucial roles in maintenance of breast health. In this review, we summarize the recent findings on breast tissue microbiota and its interplay with BC. Bacterial signatures identified via next-generation sequencing as well as their impact on breast carcinogenesis and cancer therapies are reviewed. Correlation of breast tissue microbiota and other factors, such as geographical and racial differences, in BC is discussed. Additionally, we discuss the future directions of research on breast microbiota as well as its potential role in prevention, diagnosis and treatment of BC.
... Hormesis elucidates that high doses of antioxidants do not retard ageing owing to the feedback mechanism signaling downregulation of antioxidant production. When compared to non-vegetarian diets, a vegetarian diet provides more plant-based proteins and lower methionine content, aiding in lifespan and health enhacement (McCarty, Barroso-Aranda & Contreras, 2009;Cavuoto & Fenech, 2012). Thus vegetarian diets are associated with reduced all-cause mortality. ...
Chapter
In retrospect to the rise in the occurrence of ageing related disorders and the everlasting desire to overcome ageing, exploring the causes, mechanisms and therapies to curb ageing becomes relevant. Reactive Oxygen Species (ROS) are commonly generated during normal growth and development. However abiotic and biotic stresses enhance the level of ROS which in turn pose the threat of oxidative stress. Ability to perceive ROS and to speedily commence antioxidant defenses is crucial for the survival as well as longevity of living cells. Therefore living organisms are bestowed with antioxidants to combat the damages caused by oxidative stress. This chapter aims to elucidate an overview of the process of ageing, generation and enhancement of reactive oxygen species, damages incurred by oxidative stress, its amelioration strategies, therapeutic and biotechnological potentials of antioxidants and various sources of bioactive compounds significant in retardation of aging process.
... [2][3][4]7,8 Methionine dependence in tumor cells has been extensively reported and restriction of dietary methionine is considered as a valuable strategy in limiting cancer growth. [9][10][11][12] Tumor cells shows an accelerated demand of methionine for trans-methylation, transsulfuration, re-methylation, aminopropylation, salvage, and protein synthesis. [13][14][15][16][17] Methionine is transported across cell membrane mainly through L-type amino acid transporters (LAT1), which are consistently expressed at high levels in proliferating tumors such as breast cancer, cervical cancer etc. thus making methionine as a targeting ligand for transport into cancer cells. ...
Article
Methionine-gold nanoparticles (MGNs) was synthesized by conjugating methionine via dithiocarbamate linkage to gold nanoparticles (GNPs), prepared simultaneously by one pot modified Burst method. Formation of MGNs was confirmed by UV-visible spectroscopy and appearance of new IR bands in the range of 934 cm⁻¹ to 1086 cm⁻¹ and shifting of N-C,S-S and S-C-S stretching, confirms the involvement of ‘-S-C-S-’ group of methionine dithiocarbamate with GNPs. The presence of Au in MGNs was confirmed by EDXA spectrum, whereas TEM, SAED and XRD revealed that MGNs are nanocrystalline (~13 nm) and have face-centered cubic structure. MGNs was labeled with 99mTc (TMGNs) with radiolabeling efficiency greater than 99% using 300 μg of stannous chloride, pH 7 and 90.6 MBq of 99mTcO4. The stability data showed that the conjugate will remain infrangible in systemic circulation and in acidic microenvironment of tumor. The blood kinetic profile of TMGN in rabbits and biodistribution studies in EAT tumor bearing balb/c mice showed longer in vivo circulation and slow clearance compared to radiolabeled methionine (TM). TMGN demonstrated nearly three-fold higher tumor accumulation (3.9 ± 0.35% ID/g), 2-fold lower tumor saturation dose (1.0 μg/kg) and higher tumor retention compared with TM. Data showed that the TMGN tumor: blood ratio (1.05) is nearly 2.5-fold higher than TM (0.44), whereas TMGN tumor: muscle ratio (97.5) is nearly 8-fold higher than TM (11.6). In conclusion, TMGN showed excellent tumor targeting and has promising prospects as a SPECT-radiopharmaceutical for imaging tumors.
... Methionine is an important sulfur-containing amino acid that plays essential roles in multiple biological processes, such as DNA methylation, protein structure, and polyamine synthesis (Brosnan et al., 2007;Cavuoto and Fenech, 2012). Methionine could be transformed into S-adenosylmethionine (SAM) by the catalysis of SAM synthetase (EC 2.5.1.6) ...
Article
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Amino acid metabolism could exert regulatory effects on Monascus pigments (MPs) biosynthesis. In this work, MPs biosynthesis regulated by methionine and S-adenosylmethionine (SAM) was investigated in Monascus purpureus RP2. The results indicated that the addition of methionine in fermentation significantly reduced MPs production by 60–70%, and it induced a higher expression of SAM synthetase Mon2A2272 and consequently led to SAM accumulation. However, the addition of SAM in fermentation promoted MPs production by a maximum of 35%, while over-expression of the gene Mon2A2272 led to a decrease in MPs yield, suggesting that SAM synthetase and SAM were likely to play different regulatory roles in MPs biosynthesis. Furthermore, the gene transcription profile indicated that SAM synthetase expression led to a higher expression of the transcriptional regulatory protein of the MPs biosynthesis gene cluster, while the addition of SAM gave rise to a higher expression of MPs biosynthesis activator and the global regulator LaeA, which probably accounted for changes in MPs production and the mycelium colony morphology of M. purpureus RP2 triggered by methionine and SAM. This work proposed a possible regulation mechanism of MPs biosynthesis by SAM metabolism from methionine. The findings provided a new perspective for a deep understanding of MPs biosynthesis regulation in M. purpureus.
... Interestingly, decreased levels of inosine could also be due to the microbiota itself, since it has been reported that Lactobacillus reuteri impacts inosine levels [22]. As for methionine, several studies showed that methionine restriction also inhibits aging-related disease processes in mice and inhibits colon carcinogenesis in rats [23] and in humans, methionine restriction could be achieved through a plantbased diet [24]. In conclusion, these data suggest a role for DCA on tumor environment and more studies are needed in order to understand whether DCA supplementation could be supportive as synergistic approach to enhance the e cacy of existing cancer treatments in pancreatic cancer patients. ...
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Objective: Despite recent advances in treatment options, pancreatic cancer remains the most deadly major cancer. Targeting metabolism represents an emerging anti-cancer strategy. Results: Metagenomic 16S analysis was employed to explore the effect of Dichloroacetate (DCA) on the composition of the fecal microbiota and metabolomic profile was assessed on in vivo pancreatic cancer mouse xenograft model. Pancreatic cancer xenograft mice displayed a shift of microbiota’ profile as compared to control mice without DCA treatment and a significant decrease of the purine bases inosine xanthine together with their metabolically-related compound hypoxanthine were observed in the DCA treated group as compared to the control group. Two aminoacids methionine and aspartic acid resulted decreased and increased respectively. DCA affects tumor environment and studies are needed in order to understand whether DCA supplementation could be supportive as synergistic approach to enhance the efficacy of existing cancer treatments in pancreatic cancer patients.
... Interestingly, decreased levels of inosine could also be due to the microbiota itself, since it has been reported that Lactobacillus reuteri impacts inosine levels [22]. As for methionine, several studies showed that methionine restriction also inhibits aging-related disease processes in mice and inhibits colon carcinogenesis in rats [23] and in humans, methionine restriction could be achieved through a plant-based diet [24]. In conclusion, these data suggest a role for DCA on tumor environment and more studies are needed in order to understand whether DCA supplementation could be supportive as synergistic approach to enhance the efficacy of existing cancer treatments in pancreatic cancer patients. ...
Article
Full-text available
Objective Despite recent advances in treatment options, pancreatic cancer remains the most deadly major cancer. Targeting metabolism represents an emerging anti-cancer strategy. Results Metagenomic 16S analysis was employed to explore the effect of Dichloroacetate (DCA) on the composition of the fecal microbiota and metabolomic profile was assessed on in vivo pancreatic cancer mouse xenograft model. Pancreatic cancer xenograft mice displayed a shift of microbiota’ profile as compared to control mice without DCA treatment and a significant decrease of the purine bases inosine xanthine together with their metabolically-related compound hypoxanthine were observed in the DCA treated group as compared to the control group. Two aminoacids methionine and aspartic acid resulted decreased and increased respectively. DCA affects tumor environment and studies are needed in order to understand whether DCA supplementation could be supportive as synergistic approach to enhance the efficacy of existing cancer treatments in pancreatic cancer patients.
... 48 In tumours, methionine metabolism is particularly relevant because cancer cells tend to have an abnormally high requirement for methionine. 16,49 The competition for methionine between tumour and immune cells in the tumour microenvironment has been linked to highly variable, altered epigenetic patterns, and decreased T-cell immunity. 50 Methionine dependency in tumour cells is particularly pronounced when the MTAP gene is deleted, which encodes an enzyme in the methionine salvage pathway. ...
Article
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Methionine is an amino acid that humans and farm animals must derive from food. This metabolite, a tightly regulated resource in ecosystems, has become a mass commodity in the global economy, with well over 1 million tons being produced annually from petroleum to fortify livestock feed. Viewed from the standpoint of planetary health, anthropogenic methionine synthesis is an important enabler of low-cost animal protein production, with interdependent but unexamined effects on human health and ecosystems. At a time when agrochemical engineering is shifting the way sulphur is assimilated and moves up our food chain, research suggests that dietary methionine restriction alone captures many healthspan benefits noted with calorie restriction. As such, methionine synthesis is an excellent exemplar of planetary scale anthropogenic activity that manifests at the molecular scale of cellular metabolism, with potential systemic effects on human health. In this Personal View we establish the scale and historical trajectory of the methionine industry and provide a preliminary model for tracing this amino acid through the food supply into the human body. We draw together insights across disparate publications of applied animal agriculture, human nutrition, and biomedical research to call for cross-disciplinary dialogue on responsible use of methionine-augmentation technologies.
... We have also validated the mechanistic connection between methionine, H3K79me2, and STAT5 in human and mouse tumour-infiltrating T cells. Notably, as substantial methionine is required for abnormal tumour cell proliferation and metabolism 35 , the effects of dietary methionine restriction on tumour growth have been tested in immune-deficient systems 36 . Our work indicates that both human and mouse effector T cells are sensitive to methionine. ...
Article
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Abnormal epigenetic patterns correlate with effector T cell malfunction in tumours 1–4 , but the cause of this link is unknown. Here we show that tumour cells disrupt methionine metabolism in CD8 + T cells, thereby lowering intracellular levels of methionine and the methyl donor S-adenosylmethionine (SAM) and resulting in loss of dimethylation at lysine 79 of histone H3 (H3K79me2). Loss of H3K79me2 led to low expression of STAT5 and impaired T cell immunity. Mechanistically, tumour cells avidly consumed methionine and outcompeted T cells for methionine by expressing high levels of the methionine transporter SLC43A2. Genetic and biochemical inhibition of tumour SLC43A2 restored H3K79me2 in T cells, thereby boosting spontaneous and checkpoint-induced tumour immunity. Moreover, methionine supplementation improved the expression of H3K79me2 and STAT5 in T cells, and this was accompanied by increased T cell immunity in tumour-bearing mice and patients with colon cancer. Clinically, tumour SLC43A2 correlated negatively with T cell histone methylation and functional gene signatures. Our results identify a mechanistic connection between methionine metabolism, histone patterns, and T cell immunity in the tumour microenvironment. Thus, cancer methionine consumption is an immune evasion mechanism, and targeting cancer methionine signalling may provide an immunotherapeutic approach.
... It is worth noting that decreased SLC7A11 level is related to increased methionine dependence of breast cancer cells and drug resistance of gastric cancer [19,50]. Methionine dependence is vital to repress tumor growth and can affect progression of multiple tumors, such as PCa, breast cancer, and colorectal cancer [51,52]. Mavrakis et al. [53] reported that in MTAP/CDKN2A-deleted cancers, metabolic disorder of methionine leads to PRMT5 dependence of cancer cells. ...
Article
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In recent years, morbidity and mortality of prostate cancer (PCa) have increased dramatically, while mechanistic understanding of its onset and progression remains unmet. LncRNA SNHG3 has been proved to stimulate malignant progression of multiple cancers, whereas its functional mechanism in PCa needs to be deciphered. In this study, our analysis in the TCGA database revealed high SNHG3 expression in PCa tissue. Further analysis in starBase, TargetScan, and mirDIP databases identified the SNHG3/miR-152-3p/SLC7A11 regulatory axis. FISH was conducted to assess the distribution of SNHG3 in PCa tissue. Dual-luciferase reporter gene and RIP assays confirmed the relationship among the three objects. Next, qRT-PCR and western blot were conducted to measure expression levels of SNHG3, miR-152-3p, and SLC7A11. CCK-8, colony formation, Transwell, and flow cytometry were carried out to assess proliferation, migration, invasion, methionine dependence, apoptosis, and the cell cycle. It was noted that SNHG3 as a molecular sponge of miR-152-3p stimulated proliferation, migration, and invasion, restrained methionine dependence and apoptosis, and affected the cell cycle of PCa cells via targeting SLC7A11. Additionally, we constructed xenograft tumor models in nude mice and confirmed that knockdown of SNHG3 could restrain PCa tumor growth and elevate methionine dependence in vivo. In conclusion, our investigation improved understanding of the molecular mechanism of SNHG3 modulating PCa progression, thereby generating novel insights into clinical therapy for PCa.
... Certain cancer cells exhibit methionine auxotrophy. Thus, MetR represents an intervention that can extend lifespan with a complementary effect of delaying tumor growth (60). In addition to suppressing tumor growth and extending lifespan, MetR in rodents also prevents visceral fat mass accumulation and from the negative effects of a high-fat diet (16,(61)(62)(63). ...
Article
Loss of metabolic homeostasis is a hallmark of aging and is characterized by dramatic metabolic reprogramming. To analyze how the fate of labeled methionine is altered during aging, we applied ¹³ C5-Methionine labeling to Drosophila and demonstrated significant changes in the activity of different branches of the methionine metabolism as flies age. We further tested whether targeted degradation of methionine metabolism components would “reset” methionine metabolism flux and extend the fly lifespan. Specifically, we created transgenic flies with inducible expression of Methioninase , a bacterial enzyme capable of degrading methionine and revealed methionine requirements for normal maintenance of lifespan. We also demonstrated that microbiota-derived methionine is an alternative and important source in addition to food-derived methionine. In this genetic model of methionine restriction (MetR), we also demonstrate that either whole-body or tissue-specific Methioninase expression can dramatically extend Drosophila health- and lifespan and exerts physiological effects associated with MetR. Interestingly, while previous dietary MetR extended lifespan in flies only in low amino acid conditions, MetR from Methioninase expression extends lifespan independently of amino acid levels in the food. Finally, because impairment of the methionine metabolism has been previously associated with the development of Alzheimer’s disease, we compared methionine metabolism reprogramming between aging flies and a Drosophila model relevant to Alzheimer’s disease, and found that overexpression of human Tau caused methionine metabolism flux reprogramming similar to the changes found in aged flies. Altogether, our study highlights Methioninase as a potential agent for health- and lifespan extension.
... Similarly, the treatment of acute lymphocytic leukemia with asparaginase, the asparagine-degrading enzyme, exploits the strong dependence on asparagine of cancer cells (Tallal et al., 1970;Aslanian and Kilberg, 2001), which led this enzyme to be approved by the FDA as a therapeutic agent (Cioni et al., 2021). Diets low in methionine or in combination with low intake of glucose have been applied for reduction of tumor growth, obtaining significant results in the mouse model (Breillout et al., 1987;Cavuoto and Fenech, 2012;Gao et al., 2019). An alternative strategy for decreasing methionine concentration in biological fluids, thus reducing its supply to cancer cells, is an enzyme-based supplementation therapy (Hoffman, 2015;Cioni et al., 2021). ...
Article
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Methionine is an essential amino acid used, beyond protein synthesis, for polyamine formation and DNA/RNA/protein methylation. Cancer cells require particularly high methionine supply for their homeostasis. A successful approach for decreasing methionine concentration is based on the systemic delivery of methionine γ-lyase (MGL), with in vitro and in vivo studies demonstrating its efficacy in cancer therapy. However, the mechanisms explaining how cancer cells suffer from the absence of methionine more significantly than non-malignant cells are still unclear. We analyzed the outcome of the human colorectal adenocarcinoma cancer cell line HT29 to the exposure of MGL for up to 72 h by monitoring cell viability, proteome expression, histone post-translational modifications, and presence of spurious transcription. The rationale of this study was to verify whether reduced methionine supply would affect chromatin decondensation by changing the levels of histone methylation and therefore increasing genomic instability. MGL treatment showed a time-dependent cytotoxic effect on HT29 cancer cells, with an IC50 of 30 µg/ml, while Hs27 normal cells were less affected, with an IC50 of >460 µg/ml. Although the levels of total histone methylation were not altered, a loss of the silencing histone mark H3K9me2 was observed, as well as a decrease in H4K20me3. Since H3K9me2/3 decorate repetitive DNA elements, we proved by qRT-PCR that MGL treatment leads to an increased expression of major satellite units. Our data indicate that selected histone methylation marks may play major roles in the mechanism of methionine starvation in cancer cells, proving that MGL treatment directly impacts chromatin homeostasis.
... Zudem sind einige Tumore Methionin-abhängig und können nicht wie normale Körperzellen benötigtes Methionin selbst zum Beispiel aus Homocystein regenerieren. Dadurch könnte der Einfluss einer Therapie, die auf einer Methionin-Restriktion basiert, zusätzlich verstärkt werden (Cavuoto andFenech, 2012, Chaturvedi et al., 2018). Auf Grund der erfolgsversprechenden Ergebnisse ist es von großer Bedeutung, die Methionin-Restriktion auch auf molekularer Ebene im Detail zu verstehen, um so künftig eine zielgerichtete Therapie zu ermöglichen. ...
Thesis
Die Krebstherapie und Behandlung von Tumoren stellt für die moderne Medizin auch in Zukunft eine enorme Herausforderung dar. Trotz intensiver Forschung konnten in den letzten Jahrzehnten zwar zunehmend Fortschritte erzielt werden, allerdings muss das Spektrum an neuen Therapieformen und Möglichkeiten kontinuierlich erweitert werden. In den letzten Jahren haben die Kalorienrestriktion sowie die Aminosäuren- und Proteinrestriktion zunehmend an Bedeutung gewonnen, da sie einen erheblichen positiven Einfluss auf die Entstehung von altersassoziierten Erkrankungen wie z.B. Krebs haben. Allen Formen gemeinsam ist die Induktion eines Low-Energy-Metabolismus, der die Zellen in einen antiproliferativen und selbst-regenerierenden Zustand versetzt. In dieser Arbeit sollte untersucht werden, ob die Methionin-Restriktion als eine Form der Aminosäurerestriktion sich grundsätzlich als Therapieform im Plattenepithelkarzinom (HNSCC) eignet. Zusätzlich sollte ein einfaches zelluläres Modellsystem etabliert werden, das auf metaboler Ebene die Charakterisierung und Analyse des Low-Energy-Metabolismus ermöglicht. Es konnte aufgezeigt werden, dass die Methionin-Restriktion eine effektive Methode ist, um die Proliferation ausgesuchter Zelllinien des HNSCC zu inhibieren. Des Weiteren konnte aufgezeigt werden, dass der Einsatz von Aminosäure-Analoga eine weitere Möglichkeit darstellt, auf die Proliferation von Tumorzellen Einfluss zu nehmen. Die massenspektrometrische Analyse der murinen Zelllinie L929 mittels LC/MS lieferte über einen Zeitraum von 5 Tagen ein detailliertes Bild des Stoffwechsels von mehr als 150 Metaboliten unter Methionin-Restriktion. Durch die Definition eines charakteristischen Fingerabdrucks nach 48 h und eines nur wenige Metabolite umfassenden Fußabdrucks konnte ein murines Modellsystem etabliert werden, dass die Analyse von potentiellen Wirkstoffen, u.a. sogenannten caloric restriction mimetics, ermöglicht.
... Dietary restriction of Met may be a main strategy to control cancer growth (Cavuoto & Fenech, 2012). Furthermore, Met restriction resulted in killing Met-dependent cancer cells co-cultured with normal cells. ...
Article
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Background Colorectal cancer is the third most commonly diagnosed cancer. Natural compounds, administered together with conventional chemotherapeutic agent(s) and/or radiotherapy, may be a novel element in the combination therapy of this cancer. Considering the anticancer properties of compounds derived from different tissues of various snail species confirmed earlier, the purpose of the present research was to evaluate the effect of extracts from eggs of Helix aspera maxima and Helix aspersa aspersa snails, and fractions of extracts containing particles of different molecular weights on Caco-2 human epithelial colorectal adenocarcinoma cells. Methods The extracts and fractions were analyzed for antioxidant activity, phenols and total carbohydrates using colorimetric methods. Lipid peroxidation products and glutathione in eggs were also examined using these methods. Crude protein and fat in eggs were determined. Molecular weights of egg proteins and glycoproteins were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Astaxanthin, selected vitamins and amino acids in eggs were measured using liquid chromatography methods, and minerals by emission spectroscopy, mass spectrometry or X-ray fluorescence. The action of extracts on the cell viability was determined by the MTT (methylthiazolyldiphenyl-tetrazolium bromide) test, based on the mitochondrial oxidative activity, after 24 and 72 h of treatment. The influence of fractions on the cell viability was assayed after 24 h. The effect of extracts on the percentage of live and dead cells was evaluated by the trypan blue assay, in which live cells exclude trypan blue, while dead cells take up this dye, after 12, 24, 48 and 72 h of treatment. Their influence on the integrity of cell membranes was determined based on the activity of LDH (lactate dehydrogenase), released from damaged cells, after 24 and 72 h of treatment. Then, the effect of extracts on the content of lipid peroxidation products in cells was examined using colorimetric method, after 24 h of treatment. Their influence on types of cell death was determined by flow cytometry, after this time. Results The extracts and their fractions containing molecules <3 kDa decreased the cell viability, after 24 h of treatment. The extracts reduced the percentage of live cells (also after 48 h), increased the degree of cell membrane damage and the amount of lipid peroxidation products, induced apoptosis and reduced necrosis. Conclusions Antioxidants, phenols, lipid peroxidation products, anticancer peptides, restriction of methionine, appropriate ratio of essential amino acids to non-essential amino acids, vitamin D 3 , Ca, Mg, S, Cu, Mn, Zn, Se and other bioactive compounds comprised in the extracts and their additive and synergistic effects may have influenced Caco-2 cells. Natural extracts or the chemical compounds contained in them might be used in the combination therapy of colorectal cancer, which requires further research.
... The elevated serine concentration in our data implied HBV infection may change T cell expansion. Accordingly, phenylalanine, tyrosine, and methionine as key elements for protein synthesis [70,71], and the increase in their concentrations suggested that HBV accelerates protein synthesis in the spleen [40]. Moreover, uridine deficiency can reduce the ability of spleen cells to secrete interleukin-2, reduce the activity of natural killer cells, and even affect the humoral immune response to T cell-dependent antigens [72]. ...
Article
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Hepatitis B virus (HBV) infection is a worldwide health burden. Metabolomics analysis has revealed HBV-induced metabolism dysregulation in liver tissues and hepatocytes. However, as an infectious disease, the tissue-specific landscape of metabolic profiles of HBV infection remains unclear. To fill this gap, we applied untargeted nuclear magnetic resonance (NMR) metabolomic analysis of the heart, liver, spleen, lung, kidney, pancreas, and intestine (duodenum, jejunum, ileum) in HBV-transgenic mice and their wild-type littermates. Strikingly, we found systemic metabolic alterations induced by HBV in liver and extrahepatic organs. Significant changes in metabolites have been observed in most tissues of HBV-transgenic mice, except for ileum. The metabolic changes may provide novel therapeutic targets for the treatment of HBV infection. Moreover, tissue-specific metabolic profiles could speed up the study of HBV induced systemic metabolic reprogramming, which could help follow the progression of HBV infection and explain the underlying pathogenesis.
... For example, in Met restriction, most plant proteins contain too low Met. In humans, dietary Met restriction may be achieved with a predominately vegan diet [170], as vegetarianism is considered to be a "mild" form of Met restriction. Met degradation with methionase (METase) is found to be another strategy. ...
Article
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Background Obesity develops due to an imbalance in energy homeostasis, wherein energy intake exceeds energy expenditure. Increasing evidence shows that manipulations of dietary protein and their component amino acids affect the energy balance, resulting in changes in fat mass and body weight. Amino acids are not only the building blocks of proteins but also serve as signals regulating multiple biological pathways. Scope of review We present the current available knowledge regarding the effects of dietary alterations of a single essential amino acid (EAA) on energy balance and relevant signaling mechanisms at both the central and peripheral levels. We also summarize the association between EAAs and obesity in humans and the clinical use of modifying the dietary EAA composition for therapeutic intervention in obesity. Finally, we describe similar mechanisms underlying diets varying in protein levels and diets altered of a single EAA. This review will expand the understanding of the contribution of protein and amino acids to energy balance control, which could be helpful in the discovery of new therapeutic approaches for obesity and related diseases. Major conclusions Changes in circulating EAA levels, particularly increased branched-chain amino acids (BCAAs), have been observed in obese human and animal models. Alterations in dietary EAA intake can lead to improvements in fat and weight loss in rodents, and each has its distinct mechanism. For example, leucine deprivation increases energy expenditure and reduces food intake and fat mass, primarily through regulation of the general control nonderepressible 2 (GCN2) and mammalian target of rapamycin (mTOR) signaling. Methionine restriction by 80 % decreases fat mass and body weight while developing hyperphagia, mainly via fibroblast growth factor (FGF) 21 signaling. Some effects of diets with different protein levels on energy homeostasis are mediated by similar mechanisms. However, reports on the effects and underlying mechanisms of dietary EAA imbalances on human body weight are few, and more investigations are needed.
... Methionine: Methionine is critical for tumor cell growth, and a medium lacking methionine inhibits tumor growth in vitro (Cavuoto and Fenech, 2012). Dietary supplementation with restricted methionine inhibited tumor growth and produced antitumor therapeutic effects in a mouse model . ...
Article
The changes associated with malignancy are not only in cancer cells but also in environment in which cancer cells live. Metabolic reprogramming supports tumor cell high demand of biogenesis for their rapid proliferation, and helps tumor cell to survive under certain genetic or environmental stresses. Emerging evidence suggests that metabolic alteration is ultimately and tightly associated with genetic changes, in particular the dysregulation of key oncogenic and tumor suppressive signaling pathways. Cancer cells activate HIF signaling even in the presence of oxygen and in the absence of growth factor stimulation. This cancer metabolic phenotype, described firstly by German physiologist Otto Warburg, insures enhanced glycolytic metabolism for the biosynthesis of macromolecules. The conception of metabolite signaling, i.e., metabolites are regulators of cell signaling, provides novel insights into how reactive oxygen species (ROS) and other metabolites deregulation may regulate redox homeostasis, epigenetics, and proliferation of cancer cells. Moreover, the unveiling of noncanonical functions of metabolic enzymes, such as the moonlighting functions of phosphoglycerate kinase 1 (PGK1), reassures the importance of metabolism in cancer development. The metabolic, microRNAs, and ncRNAs alterations in cancer cells can be sorted and delivered either to intercellular matrix or to cancer adjacent cells to shape cancer microenvironment via media such as exosome. Among them, cancer microenvironmental cells are immune cells which exert profound effects on cancer cells. Understanding of all these processes is a prerequisite for the development of a more effective strategy to contain cancers.
... Moreover, we found a high activation degree of "methionine de novo and salvage" pathway ( Figures 3H and S19C,D). The survival and proliferation of cancer cells were shown to be dependent on methionine levels [65]. Finally, we found that microtubule organization differed between LGG and GBM ( Figures 3D and 4C,D). ...
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... Whole PB and insect foods provide dietary fibre and a diverse range of vitamins and minerals, providing beneficial health effects, alone or in combination with traditional protein sources. A further benefit in reducing animal protein intake is the lower intake of the amino acid methionine, which is associated with a protective effect against a range of cancers (and cancer recurrence), reduced DNA damage, and enhanced longevity [140]. ...
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Methionine is an essential amino acid involved in many physiological and pathological processes. Methionine starvation caused by methionine decarboxylase ( MetDC) degradation becomes a promising strategy for cancer treatment. Multistep colorimetric method, the present approach to monitor the MetDC activity, possesses drawbacks of the complicated process, low accuracy, and poor anti‐interference due to indirect detecting. Herein, we report a facile and easy‐to‐use supramolecular tandem assay (STA) with cucurbit[7]uril and acridine orange reporter pair for the direct and real‐time monitoring of MetDC activity. The applicability of this strategy for measuring enzyme‐kinetic parameters and screening of inhibitors are also demonstrated. The STA for MetDC activity detection not only provides a feasible method for methionine‐related disease diagnosing but also opens a perspective for cancer therapy.
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The last decades have seen the identification of a number of drugs targeting oncogene pathways, therefore contributing to moving the cancer therapy field toward precision medicine. However, existing and acquired resistance to targeted therapies represent major obstacles against their long-term effectiveness. In fact, the initial efficacy of targeted therapies is often limited to a portion of the patient population and is frequently followed by the acquisition of drug-resistant disease. Molecular profiling of the resistant tissues can shed light on how cancer cells are rewiring to acquire resistance and lead to the identification of secondary targets, although even combination therapy rarely results in cancer eradication.
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The microbiota is recognized as one of the major players in human malignancies, including breast cancer (BC). Beside the role that microbiota plays in immune modulation and metabolism, affecting chronic inflammation and other drivers of cancer, specific gut bacterial genes (estrobolome) influence the sexual hormonal balance and subsequently may affect the onset, progression and treatment of hormonal dependent cancers. Moreover, specific microbes display unique features in a number of extraintestinal body sites, including the breast tissue, which can result in an increased risk of cancer, even though a clear link between microbiota composition and BC genesis is still to be confirmed. Based on these premises, in a new “oncobiotic” perspective, the individual microbiome is becoming a predictive tool and a potential target, in order to better tailor antitumoral treatments as well as to lower their toxicity.
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Dietary energy restriction has been a widely used means of experimentally extending mammalian life span. We report here that lifelong reduction in the concentration of a single dietary component, the essential amino acid L-methionine, from 0.86 to 0.17% of the diet results in a 30% longer life span of male Fischer 344 rats. Methionine restriction completely abolished growth, although food intake was actually greater on a body weight basis. Studies of energy consumption in early life indicated that the energy intake of 0.17% methionine-fed animals was near normal for animals of their size, although consumption per animal was below that of the much larger 0.86% methionine-fed rats. Increasing the energy intake of rats fed 0.17% methionine failed to increase their rate of growth, whereas restricting 0.85% methionine-fed rats to the food intake of 0.17% methionine-fed animals did not materially reduce growth, indicating that food restriction was not a factor in life span extension in these experiments. The biochemically well-defined pathways of methionine metabolism and utilization offer the potential for uncovering the precise mechanism(s) underlying this specific dietary restriction-related extension of life span.
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The S-adenosylmethionine (AdoMet) salvage enzyme 5′-methylthioadenosine phosphorylase (MTAP) has been implicated as both a cancer target and a tumor suppressor. We tested these hypotheses in mouse xenografts of human lung cancers. AdoMet recycling from 5′-methylthioadenosine (MTA) was blocked by inhibition of MTAP with methylthio-DADMe-Immucillin-A (MTDIA), an orally available, nontoxic, picomolar transition state analogue. Blood, urine, and tumor levels of MTA increased in response to MTDIA treatment. MTDIA treatment inhibited A549 (human non-small cell lung carcinoma) and H358 (human bronchioloalveolar non-small cell lung carcinoma cells) xenograft tumor growth in immunodeficient Rag2−/−γC−/− and NCr-nu mice. Systemic MTA accumulation is implicated as the tumor-suppressive metabolite because MTDIA is effective for in vivo treatment of A549 MTAP−/− and H358 MTAP+/+ tumors. Tumors from treated mice showed increased MTA and decreased polyamines but little alteration in AdoMet, methionine, or adenine levels. Gene expression profiles of A549 tumors from treated and untreated mice revealed only modest alterations with 62 up-regulated and 63 down-regulated mRNAs (≥3-fold). MTDIA antitumor activity in xenografts supports MTAP as a target for lung cancer therapy.
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DNA damage at the base-sequence, epigenome and chromosome level is a fundamental cause of developmental and degenerative diseases. Multiple micronutrients and their interactions with the inherited and/or acquired genome determine DNA damage and genomic instability rates. The challenge is to identify for each individual the combination of micronutrients and their doses (i.e. the nutriome) that optimises genome stability and DNA repair. In this paper I describe and propose the use of high-throughput nutrient array systems with high content analysis diagnostics of DNA damage, cell death and cell growth for defining, on an individual basis, the optimal nutriome for DNA damage prevention and cancer growth control.
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Recent research has shown that mesenchymal stem cells (MSCs) which were cultured for long time could transform malignantly, the transformation mechanism is not clear yet, it might be associated with the activation of oncogenes and inactivation of tumor suppressor genes. In our initial investigation, we found that the cells arising from human embryonic muscle could spontaneously transform into malignancy in vitro and we obtained 6 immortalized cell lines. In this study, polymerase chain reaction (PCR) was used to assay several tumor suppressor genes of these cell lines, and homozygous deletions within chromosomal band 9p2l including MTAP (methylthioadenosine phosphorylase), p16 and p15 were detected. PCR products of p53 exons 7 and 8 of these novel tumor cell lines were assayed by sequencing, and the results showed high prevalence of mutations in these regions, the mutation rate reached as high as 8% in exon 7 and 14% in exon 8, and all of them were point mutations, the intron 7 changed more significantly, including piece deletion, insertion, frameshift and point mutation, it showed almost no similarity to that of the wt p53 sequence, that was totally different from other p53 mutation data published. All the mutation sequences were identical in 6 cell lines, this suggest that there may be a common mutation mechanism and strong selective advantage in these novel tumor cell lines over long-term culture. In conclusion, our research shows that the inactivation of tumor suppressor genes may play an important role in the process of malignant transformation of embryonic muscle cells in vitro.
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We report an investigation of gene dosage at 9p21.3 and mutations in BRAF and NRAS, as predictors of relapse and histological markers of poor melanoma prognosis. Formalin-fixed primary melanomas from 74 relapsed and 42 nonrelapsed patients were sequenced for common BRAF and NRAS mutations (N = 71 results) and gene dosage at 9p21.3 including the genes CDKN2A (which encodes CDKN2A and P14ARF), CDKN2B (CDKN2B), and MTAP was measured using multiplexed ligation-dependant probe amplification (MLPA), (N = 75 results). BRAF/NRAS mutations were detected in 77% of relapsers and 58% of nonrelapsers (Fisher's exact P = 0.17), and did not predict ulceration or mitotic rate. There was no relationship between BRAF/NRAS mutations and gene dosage at 9p21.3. Reduced gene dosage at MTAP showed a borderline association with BRAF mutation (P = 0.04) and reduced gene dosage at the interferon gene cluster was borderline associated with wild type NRAS (P = 0.05). Reduced gene dosage in the CDKN2A regions coding for CDKN2A was associated with an increased risk of relapse (P = 0.03). Reduced gene dosage across 9p21.3 was associated with increased tumor thickness, mitotic rate, and ulceration (P = 0.02, 0.02, and 0.002, respectively), specifically in coding regions impacting on CDKN2B and P14ARF and CDKN2A. Loss at MTAP (P = 0.05) and the interferon gene cluster (P = 0.03) on 9p21 was also associated with tumor ulceration. There was no association between reduced gene dosage at 9p21.3 and subtype or site of tumor. This study presents supportive evidence that CDKN2B, P14ARF, and CDKN2A may all play a tumor suppressor role in melanoma progression.
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Eighty percent dietary methionine restriction (MetR) in rodents (without calorie restriction), like dietary restriction (DR), increases maximum longevity and strongly decreases mitochondrial reactive oxygen species (ROS) production and oxidative stress. Eighty percent MetR also lowers the degree of membrane fatty acid unsaturation in rat liver. Mitochondrial ROS generation and the degree of fatty acid unsaturation are the only two known factors linking oxidative stress with longevity in vertebrates. However, it is unknown whether 40% MetR, the relevant methionine restriction degree to clarify the mechanisms of action of standard (40%) DR can reproduce these effects in mitochondria from vital tissues of strong relevance for aging. Here we study the effect of 40% MetR on ROS production and oxidative stress in rat brain and kidney mitochondria. Male Wistar rats were fed during 7 weeks semipurified diets differing only in their methionine content: control or 40% MetR diets. It was found that 40% MetR decreases mitochondrial ROS production and percent free radical leak (by 62-71%) at complex I during forward (but not during reverse) electron flow in both brain and kidney mitochondria, increases the oxidative phosphorylation capacity of brain mitochondria, lowers oxidative damage to kidney mitochondrial DNA, and decreases specific markers of mitochondrial protein oxidation, lipoxidation, and glycoxidation in both tissues. Forty percent MetR also decreased the amount of respiratory complexes I, III, and IV and apoptosis-inducing factor (AIF) in brain mitochondria and complex IV in kidney mitochondria, without changing the degree of mitochondrial membrane fatty acid unsaturation. Forty percent MetR, differing from 80% MetR, did not inhibit the increase in rat body weight. These changes are very similar to the ones previously found during dietary and protein restriction in rats. We conclude that methionine is the only dietary factor responsible for the decrease in mitochondrial ROS production and oxidative stress, and likely for part of the longevity extension effect, occurring in DR.
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The gene for methylthioadenosine phosphorylase (MTAP) lies on 9p21, close to the gene CDKN2A that encodes the tumor suppressor proteins p16 and p14ARF. MTAP and CDKN2A are homozygously co-deleted, with a frequency of 35 to 70%, in lung and pancreatic cancer, glioblastoma, osteosarcoma, soft-tissue sarcoma, mesothelioma, and T-cell acute lymphoblastic leukemia. In normal cells, but not in tumor cells lacking MTAP, MTAP cleaves the natural substrate, 5'-deoxy-5'-methylthioadenosine (MTA), to adenine and 5-methylthioribose-1-phosphate (MTR-1-P), which are then converted to adenine nucleotides and methionine. This distinct difference between normal MTAP-positive cells and tumor MTAP-negative cells led to several proposals for therapy. We offer a novel strategy in which both MTA and a toxic adenine analog, such as 2,6-diaminopurine (DAP), 6-methylpurine (MeP), or 2-fluoroadenine (F-Ade), are administered. In MTAP-positive cells, abundant adenine, generated from supplied MTA, competitively blocks the conversion of an analog, by adenine phosphoribosyltransferase (APRT), to its active nucleotide form. In MTAP-negative tumor cells, the supplied MTA cannot generate adenine; hence conversion of the analog is not blocked. We show that this combination treatment--adenine analog plus MTA--kills MTAP-negative A549 lung tumor cells, while MTAP-positive human fibroblasts (HF) are protected. In co-cultures of the breast tumor cell line, MCF-7, and HF cells, MCF-7 is inhibited or killed, while HF cells proliferate robustly. 5-Fluorouracil (5-FU) and 6-thioguanine (6-TG) may also be used with our strategy. Though neither analog is activated by APRT, in MTAP-positive cells, adenine produced from supplied MTA blocks conversion of 5-FU and 6-TG to their toxic nucleotide forms by competing for 5-phosphoribosyl-1-pyrophosphate (PRPP). The combination of MTA with 5-FU or 6-TG, in the treatment of MTAP-negative tumors, may produce a significantly improved therapeutic index. We describe a selective strategy to kill tumor cells lacking MTAP.
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Single nucleotide polymorphisms (SNPs) in genes that control folate uptake and metabolism may have an important effect on chromosomal stability. The present study investigated the effect of common SNPs in some of these critical genes on frequency of lymphocytes with micronuclei, a biomarker of chromosome breakage or loss. 164 individuals (94 males and 70 females) of different age ranging from 18 to 73 years participated in this study. Polymorphisms in GCPII (C1561T), RFC (G80A), MTR (A2756G), MTRR (A66G and C524T), TS (tandem repeats, 6bp deletion in 3'-UTR region) and MTHFR (C677T and A1298C) were detected using PCR-based methods. Frequency of binucleated (BN) lymphocytes containing one or more micronuclei (BN-MN) was determined using the cytokinesis-block micronucleus (CBMN) assay and adjusted for the effects of age and gender. We did not find any significant association between BN-MN frequency and the common SNPs in GCPII, MTRR, TS and MTHFR genes. BN-MN frequency in individuals who carried at least one copy of the rarer G allele for MTR (A2756G) or were homozygotes for the more common G allele for RFC (G80A) had a 14% or 19% lower BN-MN frequency compared to the alternative genotypes for that SNP respectively. It was evident from genotype combination analyses that BN-MN frequency per 1000 BN cells was highest in those with the combined MTR (2756) AA and RFC (80) GA or AA genotype (13.6 per thousand) and lowest in those with the combined MTR (2756) AG or GG and RFC (80) GG genotypes (9.5 per thousand) (P trend=0.015). The RFC G80A and MTR A2756G polymorphisms and their combinations may be important variables that substantially affect lymphocyte BN-MN frequency in this South Australian cohort.
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Several studies have determined that dietary intake of B vitamins may be associated with breast cancer risk as a result of interactions between 5,10-methylenetetrahydrofolate reductase (MTHFR) and methionine synthase (MTR) in the one-carbon metabolism pathway. However, the association between B vitamin intake and breast cancer risk in Brazilian women in particular has not yet been investigated. A case-control study was conducted in São Paulo, Brazil, with 458 age-matched pairs of Brazilian women. Energy-adjusted intakes of folate, vitamin B6, and vitamin B12 were derived from a validated Food Frequency Questionnaire (FFQ). Genotyping was completed for MTHFR A1298C and C677T, and MTR A2756G polymorphisms. A logistical regression model was used to calculate odds ratios (ORs) and 95% confidence intervals (95% CIs). Neither dietary intake of folate, vitamin B6, or vitamin B12 nor MTHFR polymorphisms were independently associated with breast cancer risk. Analysis stratified by menopausal status showed a significant association between placement in the highest tertile of folate intake and risk of breast cancer in premenopausal women (OR = 2.17, 95% CI: 1.23-3.83; P trend = 0.010). The MTR 2756GG genotype was associated with a higher risk of breast cancer than the 2756AA genotype (OR = 1.99, 95% CI = 1.01-3.92; P trend = 0.801), and statistically significant interactions with regard to risk were observed between the MTHFR A1298C polymorphism and folate (P = 0.024) or vitamin B6 (P = 0.043), and between the MTHFR C677T polymorphism and folate (P = 0.043) or vitamin B12 (P = 0.022). MTHFR polymorphisms and dietary intake of folate, vitamin B6, and vitamin B12 had no overall association with breast cancer risk. However, increased risk was observed in total women with the MTR 2756GG genotype and in premenopausal women with high folate intake. These findings, as well as significant interactions between MTHFR polymorphisms and B vitamins, warrant further investigation.
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Methionine-dependence phenotype (MDP) refers to the reduced ability of cells to proliferate when methionine is restricted and/or replaced by its immediate precursor homocysteine. MDP is a characteristic of human tumors in vivo, human tumor cell lines, and normal somatic tissue in some individuals. It was hypothesized that MDP is a risk factor for developing breast cancer in BRCA (BRCA1 and BRCA2) germline mutation carriers. To test the hypothesis, human peripheral blood lymphocytes of BRCA carriers with and without breast cancer and healthy non-carrier relatives (controls) were cultured for 9 days in medium containing either 0.1 mmol/L L-methionine or 0.2 mmol/L D,L-homocysteine, with the ratio of viable cell growth in both types of medium after 9 days used to calculate the methionine-dependence index (MDI), a measure of MDP. We also tested whether MDP was associated with common polymorphisms in methionine metabolism. Viable cell growth, MDI, and polymorphism frequency in MTRR (A66G and C524T) and MTHFR (A1298C and A1793G) did not differ among the study groups; however, MDI tended to be higher in BRCA carriers with breast cancer than those without and was significantly increased in MTHFR 677T allele carriers relative to wild-type carriers (P=0.017). The presence of MTR A2756G mutant allele and MTHFR C677T mutant allele in carriers was associated with increased breast cancer risk [odds ration, 3.2 (P=0.16; 95% confidence interval, 0.76-13.9) and 3.9 (P=0.09; 95% confidence interval, 0.93-16.3), respectively]. The results of this study support the hypothesis that defects in methionine metabolism may be associated with breast cancer risk in BRCA carriers.
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Unlike normal cells, malignant rat and two simian virus 40-transformed human cell lines can neither grow nor survive in B12-and folate-supplemented media in which methionine is replaced by homocysteine. Yet three lines of evidence indicate that the malignant and transformed cells synthesize large amounts of methionine endogenously through the reaction catalyzed by 5-methyltetrahydropteroyl-L-glutamate; L-homocysteine S-methyltransferase (EC 2.1.1.13). (1) The activities of this methyltransferase were comparable in extracts of malignant and normal cells. (2) The uptake of radioactive label from [5-14C]methyltetrahydropteroyl-L-glutamic acid (5-Me-H4PteGlu) was at least as great in the malignant cells as in the normals and was nearly totally dependent on the addition of homocysteine, the methyl acceptor; furthermore, 59-84% of the label incorporated by cells was recovered as methionine.
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Many transformed and malignant cells, unlike normal cells, do not grow when methionine in the growth medium is replaced by its immediate precursor homocysteine [Chello, P. & Bertino, J. (1973) Cancer Res. 33, 1898-1904 and Hoffman, R. & Erbe, R. (1976) Proc. Natl. Acad. Sci. USA 73, 1523-1527]. Rare cells from those populations revert to methionine independence [Hoffman, R., Jacobsen, S. & Erbe, R. (1978) Biochem. Biophys. Res. Commun. 82, 228-234]. We report here that methionine-independent revertants of both human fibroblasts transformed by simian virus 40 and malignant rat fibroblasts concomitantly revert for some of the properties associated with the transformed state. Of the 13 methionine-independent revertants described here, 5 showed increased anchorage dependence as reflected by reduced cloning efficiences in methylcellulose; 8 showed an increased serum requirement for optimal growth; 8 showed decreased cell density in medium containing high serum; and 3 altered their cell morphology significantly. Eight of the 13 have increased chromosome numbers. All lines tested contained immunologically identifiable tumor antigen of simian virus 40. Thus by selecting for methionine independence it is possible to select for heterogeneous transformation revertants, indicating further a relationship between altered methionine metabolism and oncogenic transformation. Therefore a positive metabolic method to select for transformation revertants has been developed, and its use has resulted in selection of human transformation revertants.
Article
Identifying the various genetic alterations that contribute to lymphomagenesis is key to our improved understanding of the biological behavior of the disease. Recently, we and others have defined a tumor suppressor region on the short arm of chromosome 9 harboring a cluster of genes, including MTAP, CDKN2A(p16INK4a), and CDKN2B(p15INK4B), which is frequently deleted in a variety of tumor types. To determine whether this region is involved in a particular subset of malignant lymphomas, we have examined 16 cases of diffuse large‐cell lymphoma (DLCL) (including three cases that evolved from low‐grade non‐Hodgkin lymphoma (NHL) (transformed DLCL)), and nine cases of low‐grade NHL that had subpopulations of large cells with a diffuse growth pattern (seven follicular NHL, one chronic lymphocytic leukemia, one mycosis fungoides). Interphase fluorescence in situ hybridization was performed on these samples using a 250‐kb cosmid contig (COSp16), which encompasses MTAP, CDKN2A, and CDKN2B. Six of the 16 DLCLs and one of nine low‐grade NHLs had deletions of COSp16. COSp16 was homozygously deleted in four cases; two cases had hemizygous deletions, and one case had a partial homozygous deletion of the cosmid contig. Three of 13 cases of de novo DLCL, all three transformed DLCLs, and one of nine low‐grade NHL had COSp16 deletions. Although the numbers are small, COSp16 deletion was associated with transformed DLCL in contrast to de novo DLCL (P < 0.04, Fisher's exact test) or low‐grade NHL (P < 0.02). The COSp16 deletion was mostly submicroscopic and was not observed in association with any specific recurring cytogenetic abnormalities. These results suggest that targeted deletion of the CDKN2A region occurs in a subset of non‐Hodgkin's lymphomas, and may be associated with transformed lymphomas. Genes Chromosomes Cancer 22:72–78, 1998. © 1998 Wiley‐Liss, Inc.
Article
When diets devoid of a single essential amino acid are fed to rats or mice bearing malignant tumors, tumor growth is inhibited, but host weight is also markedly depressed. Recently, diets containing low but nutritionally adequate levels of phenylalanine and tyrosine were reported to inhibit tumor growth without adversely affecting the host. In the present study, diets containing decreasing levels of each essential amino acid were used to study the growth requirements of normal mice and the effect of single essential amino acid restriction on tumor-bearing mice and on the growth of their tumors. Amino acids required by these mice expressed as percentage of diet, in general were quantitatively similar to the maintenance requirements of the rat. Dietary levels of tryptophan, threonine, leucine, or methionine which significantly inhibited tumor growth, significantly depressed host weight as well. Reducing dietary levels of phenylalanine, valine, or isoleucine significantly inhibited tumor weight without affecting host weight. Lysine restriction had no effect on weight gain or tumor growth. Findings with valine, isoleucine, and leucine suggest that amino acid interrelations previously described in intact animals exist in tumor-bearing animals and may offer an approach to tumor inhibition.
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Adult T-cell leukemia (ATL) is a retrovirus-associated leukemia with poor prognosis and often has deletions of the p16(INK4a) and p15(INK4b) genes on chromosome 9p21. The gene for methylthioadenosine phosphorylase (MTAP), a purine and methionine metabolic enzyme, resides approximately 100 Kb telomeric to the p16(INK4a) gene and is frequently co-deleted with the tumor suppressor gene in a variety of cancers. This enzyme deficiency can be exploited for selective chemotherapy with de novo purine synthesis inhibitors and/or methionine depletion. To determine whether ATL can be a candidate for selective chemotherapy based on genetic alterations on chromosome 9p21, we analyzed the MTAP gene in 41 samples from ATL patients (27 acute type and 14 chronic type ATL) and 3 cell lines established from ATL patients. Five samples from the acute type had deletions of the MTAP gene (4 total deletions and 1 partial deletion of exons 6-8). The MTAP gene was always co-deleted with P16(INK4a). No deletion of the MTAP gene was detected in samples from the chronic type. Of 3 cell lines, 2 showed partial deletions of exons 5-8 of the MTAP gene, and 1 lost all exons. The p16(INK4a) gene was deleted in all cell lines. In conclusion, deletions of the MTAP gene were found in 5 of 27 acute type ATL samples. Acute type ATL with MTAP deficiency can be a good candidate for selective chemotherapy by depleting purines and/or methionine. (C) 1998 Wiley-Liss, Inc.
Conference Paper
Glutathione (GSH; gamma-glutamylcysteinylglycine) is ubiquitous in mammalian and other living cells. It has several important functions, including protection against oxidative stress. It is synthesized from its constituent amino acids by the consecutive actions of gamma-glutamylcysteine synthetase and GSH synthetase. gamma-Glutamylcysteine synthetase activity is modulated by its light subunit and by feedback inhibition of the end product, GSH. Treatment with an inhibitor, buthionine sulfoximine (BSO), of gamma-glutamylcysteine synthetase leads to decreased cellular GSH levels, and its application can provide a useful experimental model of GSH deficiency. Cellular levels of GSH may be increased by supplying substrates and GSH delivery compounds. Increasing cellular GSH may be therapeutically useful.
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We have prepared antibodies against porcine liver BHMT, and recently cloned cDNAs encoding the porcine and human enzyme. Porcine tissues were tested for BHMT expression by enzyme activity measurements, and Western analysis. Porcine liver and kidney were the only organs that had immune-detectable levels of BHMT protein, and expressed high levels of enzyme activity. Porcine pancreas, brain, heart, lung, and spleen were essentially devoid of enzyme activity and had no immuno-detectable protein. Both BHMT activity measurements and Western analysis indicate that BHMT is expressed in porcine kidney cortex, and not the medulla. Human tissues were tested for BHMT expression by Northern analysis. Human liver and kidney were the only organs that expressed BHMT mRNA. Human pancreas, brain, heart, skeletal muscle, spleen, and placenta were devoid of BHMT mRNA. BHMT was mapped to human chromosome 5 by PCR amplification using human BHMT-specific primers and chromosome specific human-rodent somatic cell hybrid panels. Refinement of the physical localization of the gene was obtained by screening a yeast artificial chromosome library. Funded by AHA (IL affiliate), and ILSI (N. America).
Book
During the last 15 years the research on homocysteine and the vitamins involved in its metabolism has become very dynamic. About 1,500 publications on the subject are now published each year. The research has long mainly focused on the association between homocysteine and cardiovascular disease, but also pregnancy complications/ fetal malformations. There is, however, an increasing interest in the connection between the homocysteine metabolism and neuropsychiatric disease with a steeply increasing number of publications. In particular, the association between homocysteine metabolism and cognitive decline/dementia attracts much interest. If simple, non-toxic homocysteine-lowering treatment with vitamins can reduce the incidence of, or delay the onset of dementia, it would have an enormous impact in societies with a rapidly increasing number of elderly at risk for dementia. This book summarises the research within the neuropsychiatric field, but also gives an overview of the underlying biochemistry and of diagnostic aspects. About 1,000 references are given. Christina Bolander-Gouaille, a pharmacist, has for over 10 years specialised in writing reviews/monographs on homocysteine and related vitamins. This is her third book in a series edited by Springer Verlag. This book, however, is written in collaboration with Teodoro Bottiglieri, who is director of neuropharmacology and senior research scientist at Baylor University, Institute for Metabolic Diseases in Dallas, USA.
Article
Pancreatic carcinoma cells lines are known to have a high incidence of homozygous deletion of the candidate tumor suppressor gene p16 (MTS1/CDKN2), which resides in the chromosome 9p21 region. Here we: (a)examined a series of these cell lines for the incidence of codeletion of genes located near p16, in particular, the gene for the enzyme 5'-deoxy-5'-methylthioadenosine phosphorylase (MTAP) and the genes of the IFN-alpha and -beta cluster (IFNs); and (b) investigated whether therapeutic strategies could be developed that target malignant cells that have undergone the codeletion of such genes. Five of the eight pancreatic carcinoma cell lines were p16(-), MTAP was codeleted in all five cases. Because MTAP phosphorolyzes 5'-deoxy-5'-methylthioadenosine (MTA), generated as a byproduct of polyamine synthesis, to the salvageable purine base adenine, loss of this pathway in p16(-), MTAP(-) cells might sensitize these cells to methotrexate (MTX), the mechanism of action of which involves, in part, an inhibition of purine de novo synthesis. MTAP(+) normal keratinocytes and pancreatic carcinoma lines had relatively poor sensitivity, in terms of efficacy, to the purine nucleotide-starving actions of MTX. This may be in part due to the MTAP-dependent salvage of adenine moieties from endogenously generated MTA, because the MTAP inhibitor 5'-chloro-5'-de- oxyformycin A potentiates the antipurine actions of MTX in some of these MTAP(+) lines. Also, exogenous MTA (10 microM) reverses the growth-inhibitory actions of MTX in these lines. In contrast, MTAP(-) cell lines, which cannot recycle purines from endogenous MTA, have a relatively high sensitivity to the antipurine actions of MTX, which is not modulated by 5'-chloro-5'-deoxyformycin A or exogenous MTA. Thus the MTAP loss in malignant cells may be an example of gene deletion chemoselectivity, in which genetic deletions that occur as part of the oncogenic process render these cells more sensitive to particular anticancer agents than normal cells, which have not undergone such deletions. We also examined whether the loss of IFN genes sensitize cells to the growth-inhibitory actions of these cytokines. Three of the five p16(-) cell lines bore homozygous deletions of IFNA1 and IFNB1 genes, representing each end of the IFN-alpha,-beta gene cluster; one cell line bore a codeletion of the IFNA1 gene but retained the IFNB1 locus. Whereas the cell lines that were most sensitive to the growth-inhibitory effects of IFN-beta or IFN-alpha(2b), tended to be those with IFN deletions, there were enough exceptions to this pattern to indicate that the IFN genotype does not reliably predict IFN responsiveness.
Article
Recent research has shown that mesenchymal stem cells (MSCs) which were cultured for long time could transform malignantly, the transformation mechanism is not clear yet, it might be associated with the activation of oncogenes and inactivation of tumor suppressor genes. In our initial investigation, we found that the cells arising from human embryonic muscle could spontaneously transform into malignancy in vitro and we obtained 6 immortalized cell lines. In this study, polymerase chain reaction (PCR) was used to assay several tumor suppressor genes of these cell lines, and homozygous deletions within chromosomal band 9p21 including MTAP (methylthioadenosine phosphorylase), p16 and p15 were detected. PCR products of p53 exons 7 and 8 of these novel tumor cell lines were assayed by sequencing, and the results showed high prevalence of mutations in these regions, the mutation rate reached as high as 8% in exon 7 and 14% in exon 8, and all of them were point mutations, the intron 7 changed more significantly, including piece deletion, insertion, frameshift and point mutation, it showed almost no similarity to that of the wt p53 sequence, that was totally different from other p53 mutation data published. All the mutation sequences were identical in 6 cell lines, this suggest that there may be a common mutation mechanism and strong selective advantage in these novel tumor cell lines over long-term culture. In conclusion, our research shows that the inactivation of tumor suppressor genes may play an important role in the process of malignant transformation of embryonic muscle cells in vitro.
Article
The gene that encodes methylthioadenosine phosphorylase (MTAP), an enzyme involved in adenine and methionine salvage pathways, is located on chromosome 9p21 telomeric to the p16INK4A/CDKN2A tumor suppressor gene. Inactivation of the p16INK4A/CDKN2A gene occurs by three different mechanisms: hypermethylation of the gene promoter, intragenic mutation coupled with loss of the second allele, and homozygous deletion. Immunohistochemical labeling for the p16INK4A/CDKN2A gene product parallels gene status but does not elucidate the mechanism of gene inactivation. Since the MTAP gene is often co-deleted with p16INK4A/CDKN2A, concurrent immunolabeling for both proteins can identify cases with homozygous p16INK4A/CDKN2A gene deletion. MTAP loss itself has therapeutic implications since it may confer selective sensitivity to inhibitors of de novo purine biosynthesis, such as L-alanosine. Twelve tissue microarrays were constructed from 92 cases of Barrett-associated adenocarcinomas and precursor lesions and 112 cases of gastric adenocarcinoma and precursor lesions comprising 1161 individual cores. Multiple cores were arrayed from any given case, and when available, included the entire histologic spectrum of intestinal metaplasia-dysplasia-carcinoma. Tissue microarrays were labeled with monoclonal antibodies against MTAP protein (clone 6.9, Salmedix, Inc) and p16 (clone 16P07, Neomarkers). Complete loss of labeling was considered negative, while any labeling (p16: nuclear; MTAP: cytoplasmic and nuclear) was considered positive. Loss of MTAP labeling occurred exclusively in conjunction with loss of p16 labeling, confirming that the previous findings from this group that concurrent loss of MTAP and p16 labeling is a surrogate marker of 9p21 homozygous deletions. Complete loss of MTAP and p16 was seen in 4 of 25 (16%) patients with Barrett's esophagus, 4 of 18 (22%) with low-grade dysplasia, 5 of 39 (13%) with high-grade dysplasia, 17 of 78 (22%) with invasive adenocarcinoma, and 8 of 36 (22%) of metastases. There were 7 cases of esophageal adenocarcinoma with loss of both MTAP and p16 for which precursor lesions were available. In 6 on these 7 cases (85%), the precursor lesion(s) had loss of both MTAP and p16. Lack of MTAP and p16 expression was seen in 11 of 106 (10%) cases of gastric adenocarcinoma. All metaplastic (30 biopsies from 20 cases) and dysplastic (15 biopsies from 13 cases) gastric tissues had both intact MTAP and p16INK4A/CDKN2A gene products. No precursor lesions were available from the gastric cancers that had loss of both MTAP and p16. Two benign gastric hyperplastic polyps also had intact p16 and MTAP. Concurrent MTAP and p16 loss detected by immunohistochemistry can serve as a convenient surrogate for p16INK4A/CDKN2A gene homozygous deletion in archival tissues. Inactivation of p16INK4A/CDKN2A by homozygous deletion appears to be an early event in Barrett carcinogenesis, occurring in noninvasive precursor lesions, including nondysplastic Barrett mucosa, in subsets of cases. In the absence of MTAP, cells depend exclusively on the de novo synthesis pathway for production of adenosine. This loss of MTAP during 9p21 homozygous deletion might be exploited therapeutically using de novo purine synthesis antimetabolites to treat a subset of invasive gastroesophageal adenocarcinomas and esophageal precursor lesions.
Article
Pharmacokinetics, methionine depletion, antigenicity, and toxicity of recombinant methioninase (rMETase), which has shown efficacy in achieving cell kill in a broad range of human tumor models, were examined in macaque monkeys. Dose-ranging studies at 1000, 2000, and 4000 units/kg i.v. identified the 4000 units/kg dose as able to reduce plasma methionine to an undetectable level (less than 0.5 μm) by 30 min, and the level so remained for 8 h. Pharmacokinetic analysis showed that rMETase was eliminated with a T1/2 of 2.49 h. A 2-week i.v. administration of 4000 units/kg every 8 h/day for 2 weeks resulted in a steady-state depletion of plasma methionine to less than 2 μm. The only manifest toxicity was decreased food intake and slight weight loss. Serum albumin and red cell values declined transiently during treatment, which may be related to extensive blood sampling. Re-challenge on day 28 resulted in anaphylactic shock and death in one animal. Subsequent pretreatment with hydrocortisone prevented the anaphylactic reaction, although vomiting was frequently observed. Re-challenge was carried out at days 66, 86, and 116. Anti-rMETase antibodies (at 10⁻³) were found after the first challenge, and these increased to 10⁻⁶ after the fourth challenge and decreased to 10⁻² by 2 months post therapy. The main rMETase antibody was IgG, and although it has some in vitro features of being a neutralizing antibody, each challenge dose was effective in depleting plasma methionine levels. Thus, rMETase was able to effectively deplete plasma methionine levels with minimal toxicity in a primate model. These data provide the bases for alteration by polyethyleneglycol conjugation (PEGylation) of the enzyme to increase its duration of effect and reduce its immunogenicity.
Article
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Article
Previous studies have suggested that structural abnormalities involving the short arm of chromosome 9 are frequently associated with gliomas. The a-, 0-, and u-interferon (IFNA, IFNB1, and IFNW, respectively) and the methylthioadenosine phosphorylase (Ml.II') genes have been mapped to the short arm of chromosome 9, band p22. Homozygous deletions of these genes have been reported in many leukemia- and glioma-derived cell lines. In this report, we present a detailed analysis of partial and complete homozygous or hemizygous deletions of DNA sequences on 9p in human cell lines and primary tumor samples of glioma patients. Ten of 15 (67%) glioma-derived cell lines had hemizygous or homozygousdeletion of / / \ genes or rearrangement of sequences around these genes, while 13 of 35 (37%) primary glioma tumor samples had hemizygous (8 tumors) or homozygous (5 tumors) deletion of the lf'\ genes. The shortest region of overlap of these deletions maps in the interval between the centramene end of the II \ gene cluster and the MI AT gene. In the cell lines and primary tumors examined, these gross genomic alterations were seen only in association with high grade or recurrent gliomas. Our observations confirm that loss of DNA sequences on 9p, particularly the II \ genes, occurs at a significant frequency in gliomas, and may represent an important step in the progression of these tumors. These results are consistent with a model of tumorigenesis in which the development or progression of cancer involves the loss or inactivation of a gene or several genes that normally act to suppress tumorigenesis. One such gene may be located on 9p; this gene may be closely linked to the IFN genes. Nevertheless, loss of the /F7Vgenes, when it occurs, may play an additional role in the progression of these tumors.
Article
Methionine-depleting total parenteral nutrition (Met-depleting TPN), infusing AO-90 amino acid solution (lacking both L-methionine and L-cysteine) as a sole nitrogen source, showed synergistic effects with 5-fluorouracil (5-FU) in tumor-bearing rats and in clinical trials with gastrointestinal tract cancers. In this study, the effect of Met-depleting TPN with 5-FU upon thymidylate synthase (TS) activity was examined, and the histological effect of this treatment on human gastric cancer was evaluated. Fourteen preoperative advanced gastric cancer patients were divided randomly into two groups. Seven cases were given Met-depleting TPN for 7 days before surgery with continuous intravenous administration of 5-FU (500 mg/body per day; total 4.0 g/body) (AO-90 group). The other 7 received conventional L-methionine-containing TPN with 5-FU (control group). All patients underwent gastrectomy without complications due to these treatments. Resected materials were examined for TS kinetics, and the anti-cancer effect was also assessed histopathologically. The specimens in the AO-90 group showed marked degeneration of cancer, while almost no effect was seen in the control group. The free TS activity of carcinoma tissue in the AO-90 group was decreased and the TS inhibition rate was increased in comparison with the control group (P= 0.0165 and P= 0.0243, respectively). Met-depleting TPN appears to play a role as a biomodulator of 5-FU in human gastric cancer.
Article
In a study of a diverse set of human tumor cell lines previously shown to all have a defect in methionine metabolism (Stern, P. H., Wallace, C. D. and Hoffman, R. M. J. Cellular Physiology119, 29–34, 1984), we demonstrate in this report that all have enhanced overall rates of transmethylation compared to normal human fibroblasts. Transmethylation rates were measured by blocking S-adenosylhomocysteine hydrolase and measuring the AdoHcy which accumulates as a result of transmethylation. The enhanced transmethylation rates may be the basis of the above-mentioned defects in methionine metabolism previously reported in human tumor cells, including the basis of the inability of the majority of the tumor cells to grow when methionine is replaced by homocysteine. The excess and unbalanced tRNA methylation observed for the last 25 years in many types of cancer may be at least in part explained by our results of elevated rates of overall transmethylation in cancer cells. The alteration of such a fundamental process as transmethylation in cancer may be indicative of its importance in the oncogenic process.
Article
Deletions on the short arm of chromosome 9 (9p21 region) have been reported in a number of hematopoietic and solid tumors. These aberrations on 9p have been previously associated with the loss of the interferon gene cluster and the gene for methylthioadenosine phosphorylase (MTAP), localized to the 9p21-22 region. Recently, two putative tumor suppressor gene(s) CDKN2 and MTS2 have been mapped to the 9p21 region, and shown to be deleted in a large number of tumors including leukemias, melanomas, bladder cancers and brain tumors. We have previously reported a similar 9p21 abnormality and deletions of the CDKN2 and MTS2 genes in a myxoid chondrosarcoma cell line and its subclones. In this study we report consistent abnormalities of chromosome 9 in additional chondrosarcomas examined by a detailed cytogenetic and molecular analysis. Seven chondrosarcoma cell lines, one primary chondrosarcoma, and a benign chondroma were examined. Four of the seven tumor cell lines examined showed grossly visible aberrations of chromosome 9. Molecular analysis of these chondrosarcoma cell lines revealed hemizygous deletions of the interferon genes, and the absence of the MTAP gene, protein or activity. In addition, four of the seven chondrosarcoma cell lines also showed deletions of the CDKN2 and/or MTS2 putative tumor suppressor genes, or the absence of the CDKN2 protein product. No such chromosome 9 related aberrations were detected in the benign chondroma. These data suggest that chromosome 9p21 abnormality, and deletions of the CDKN2 and MTS2 tumor suppressor genes may be a significant event in the development of chondrosareomas.