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Tubulin-binding anticancer polysulfides induce cell death via mitotic arrest and autophagic interference in colorectal cancer
Abstract
Polysulfanes show chemopreventive effects against gastrointestinal tumors. We identified diallyl tetrasulfide and its derivative, dibenzyl tetrasulfide (DBTTS), to be mitotic inhibitors and apoptosis inducers. Here, we translate their application in colorectal cancer (CRC). MALDI-TOF-MS analysis identified both compounds as reversible tubulin binders, validated by in cellulo α-tubulin degradation. BRAF(V600E)-mutated HT-29 cells were resistant to DBTTS, as evidenced by mitotic arrest for 48 h prior to apoptosis induction compared to KRAS(G12V)-mutated SW480/620 cells, which committed to death earlier. The prolonged mitotic block correlated with autophagy impairment and p62 protein accumulation in HT-29 but not in SW480/620 cells, whereas siRNA-mediated p62 inhibition sensitized HT-29 cells to death. In silico analysis with 484 colorectal cancer patients associated higher p62 expression and reduced autophagic flux with greater overall survival. Accordingly, we hypothesized that DBTTS targets CRC survival/death through autophagy interference in cell types with differential autophagic capacities. We confirmed the therapeutic potential of DBTTS by the inhibition of spheroid and colony formation capacities in CRC cells, as well as in HT-29 zebrafish xenografts in vivo.
... This interaction seems to be dependent on the number of sulfur atoms (Hosono et al. 2005). Similarly, in our laboratory, we showed that diallyl tetrasulfide (DATTS) inhibits tubulin polymerization in vitro (Kelkel et al. 2012) and that its hemi-synthetic derivative dibenzyl tetrasulfide (DBTTS) inhibits tubulin polymerization in colorectal cancer cells, thereby preventing the formation of normal spindle microtubules and inducing cell cycle arrest followed by apoptosis (Yagdi Efe et al. 2017). We also showed by spectrometry analysis that DATTS and DBTTS are two reversible tubulin binders (Yagdi Efe et al. 2017), explaining the anti-proliferative property of garlicderived OSCs. ...
... Similarly, in our laboratory, we showed that diallyl tetrasulfide (DATTS) inhibits tubulin polymerization in vitro (Kelkel et al. 2012) and that its hemi-synthetic derivative dibenzyl tetrasulfide (DBTTS) inhibits tubulin polymerization in colorectal cancer cells, thereby preventing the formation of normal spindle microtubules and inducing cell cycle arrest followed by apoptosis (Yagdi Efe et al. 2017). We also showed by spectrometry analysis that DATTS and DBTTS are two reversible tubulin binders (Yagdi Efe et al. 2017), explaining the anti-proliferative property of garlicderived OSCs. ...
... DBTTS was identified as the most active and stable derivative of DATTS (Czepukojc et al. 2014). Comparison of the effects of DATTS and DBTTS showed that DBTTS was more effective than DATTS in colorectal cancer (Yagdi Efe et al. 2017). ...
Garlic has been used as a medicinal food for centuries. The biological activity of garlic relies on the presence of highly reactive sulfur compounds. Widespread in vitro and in vivo studies have reported the mechanism of action of the anticancer activity of garlic-derived organosulfur compounds (OSCs) in a wide range of cancer types. Moreover, epidemiological studies support an inverse correlation between garlic intake and cancer risk. More recently, several studies have reported the ability of garlic-derived OSCs to release hydrogen sulfide (H2S) and to affect H2S biosynthesis by altering specific H2S enzyme activity, such as cystathionine-beta-synthase or cystathionine-gamma-lyase. Paradoxically, some studies have reported that overexpression of H2S-producing enzymes is associated with ovarian and colon cancer progression. In this review, we aimed to provide a critical analysis of garlic anticancer activity by documenting our current understanding of the anticancer activity of garlic-derived OSCs. We propose here to raise a mechanistic gap in garlic-mediated anticancer activity by documenting our current knowledge of the role of H2S in cancer biology.
... Generally recognized as inducers of mitotic arrest and cell death, yet their activities appear broad, without specific intracellular targets. Here we suggest their potential as targeted agents and cancer types as suitable responders, taking the garlic-derived diallyl tetrasulfides (DATTS) and its most effective hemi-synthetic derivative di-benzyl tetrasulfide (DBTTS) as lead compounds [1][2][3][4]. We discovered DATTS/DBTTS as reversible tubulin binders, via redox modulation of the tubulin thiols. ...
... Translating our investigations to cellular models, we selected cancer types of the gastrointestinal tract (colorectal cancer, CRC) and the blood (acute forms of leukemia), being both highly proliferating and exposed in vivo to appropriate and stable concentrations of sulfur compounds. In both cell types, DATTS/DBTTS binding compromises the microtubule machinery, thereby inducing mitotic arrest and apoptosis [1][2][3][4]. Of note, a higher expression of genes coding specific tubulin isoforms in KRAS-mutated CRC SW480 and SW620 correlates with faster cell proliferation and the increased susceptibility to these compounds vs. the most resistant BRAFmutated HT-29 [1]. ...
... In both cell types, DATTS/DBTTS binding compromises the microtubule machinery, thereby inducing mitotic arrest and apoptosis [1][2][3][4]. Of note, a higher expression of genes coding specific tubulin isoforms in KRAS-mutated CRC SW480 and SW620 correlates with faster cell proliferation and the increased susceptibility to these compounds vs. the most resistant BRAFmutated HT-29 [1]. The resistance in HT-29 associated with the impairment of the autophagic flux concomitant with the prolonged mitotic block and characterized by p62 protein accumulation. ...
Diallyl polysulfides from edible plants have been widely investigated in cancer research holding the promise of a translational application. Generally recognized as inducers of mitotic arrest and cell death, yet their activities appear broad, without specific intracellular targets. Here we suggest their potential as targeted agents and cancer types as suitable responders, taking the garlic-derived diallyl tetrasulfides (DATTS) and its most effective hemi-synthetic derivative di-benzyl tetrasulfide (DBTTS) as lead compounds [1-4]. We discovered DATTS/DBTTS as reversible tubulin binders, via redox modulation of the tubulin thiols. Translating our investigations to cellular models, we selected cancer types of the gastrointestinal tract (colorectal cancer, CRC) and the blood (acute forms of leukemia), being both highly proliferating and exposed in vivo to appropriate and stable concentrations of sulfur compounds. In both cell types, DATTS/DBTTS binding compromises the microtubule machinery, thereby inducing mitotic arrest and apoptosis [1-4]. Of note, a higher expression of genes coding specific tubulin isoforms in KRAS-mutated CRC SW480 and SW620 correlates with faster cell proliferation and the increased susceptibility to these compounds vs. the most resistant BRAF-mutated HT-29 [1]. The resistance in HT-29 associated with the impairment of the autophagic flux concomitant with the prolonged mitotic block and characterized by p62 protein accumulation. Genetic p62 inhibition restores sensitivity. We confirmed the translational potential of DBTTS in 3D CRC models (in vitro: spheroids and colony formation assay; and in vivo: zebrafish xenografts) [1]. In both cell types, anti-apoptotic Bcl-2 protein members undergo phospho-modulation. In hematological cancer, Bcl-2 proteolysis/inhibition promotes cell death [2-4]. In line, Bcl-2 over-expression makes the cells more resistant; vice versa, isogenic cell lines expressing Bcl-2 mutated in the phosphorylable residues are again sensitized to the treatment, suggesting Bcl-2 proteins as critical stress sensors and transducers. Overall, we recommend components of the microtubule network, differential autophagic capacities, and Bcl-2 proteins modulation as essential factors of vulnerabilities to prioritize DATTS/DBTTS treatment.
... OSCs contain various sulfur functional groups such as CeS double and triple bonds, thioethers, disulfides, polysulfides, sulfonic acids, esters, amides, sulfuranes, and persulfuranes (Yagdi Efe et al., 2017). Diallyl polysulfides represent one of the major sulfur functional groups investigated. ...
... In vitro tubulin polymerization assay showed a direct ability of DATS/DATTS to inhibit tubulin polymerization, which was reversed by incubation with a thiol donor such as N-acetyl cysteine (NAC) (Kelkel et al., 2012). Recently, DATTS and another potent derivative DBTTS have been proved to be direct and reversible tubulin binders by MALDI-TOMFS-MS (Yagdi Efe et al., 2017). Additional mediators involved in cell proliferation and induction of cell death are critically controlled via redox modulation involving modification of their thiols. ...
The diversity of natural compounds is essential for their mechanism of action. The source, structures and struc- ture activity relationship of natural compounds contributed to the development of new classes of chemotherapy agents for over 40years. The availability of combinatorial chemistry and high-throughput screening has fueled the challenge to identify novel compounds that mimic nature's chemistry and to predict their macromolecular targets. Combining conventional and targeted therapies helped to successfully overcome drug resistance and prolong disease-free survival. Here, we aim to provide an overview of preclinical investigated natural compounds alone and in combination to further improve personalization of cancer treatment.
... Therefore, the accumulation of p62 represents a decrease in autophagic flux. One group has shown that the expression of p62 is associated with the prognosis of CRC [46,47]. Increased autophagy leads to decreased p62 expression, which enables GATA4 to evade autophagic degradation, enhance NF-κB function, and drive the antioxidant reaction to support CRC survival [48]. ...
Esophageal cancer (EC) is one of the most common digestive system malignancies in the world. The combined modality treatment of EC is usually surgery and radiation therapy, however, its clinical efficacy for advanced patients is relatively limited. Ferroptosis, a new type of iron-dependent programmed cell death, is different from apoptosis, necrosis and autophagy. In recent years, many studies have further enlightened that ferroptosis plays an essential role in the occurrence, development and metastasis of tumors. Targeting ferroptosis stimulates a new direction for further exploration of oncologic treatment regimens. Furthermore, ferroptosis has a critical role in the immune microenvironment of tumors. This paper reviews the mechanism of ferroptosis and the ferroptosis research progress in the treatment of EC. We further elaborate the interaction between ferroptosis and immunotherapy, and the related mechanisms of ferroptosis participation in the immunotherapy of EC, so as to provide new directions and ideas for the treatment of EC.
... Although the available therapeutic options for treating CRC have improved greatly over the last few decades, the prognosis for patients diagnosed with advanced-stage CRC remains dismal [1,2]. Blocking mitotic progression by targeting the microtubules of proliferating tumour cells is a consolidated strategy, and mitotic inhibitors are widely used in combination treatments for various types of tumours [3]. Therefore, the development of novel tubulin inhibitors is urgently required in order to offer more effective treatments for patients with CRC and other tumour types. ...
In this study, 2-benzyl-10a-(1H-pyrrol-2-yl)-2,3-dihydropyrazino[1,2-a]indole-1,4,10(10aH)-trione (DHPITO), a previously identified inhibitor against hepatocellular carcinoma cells, is shown to exert its cytotoxic effects by suppressing the proliferation and growth of CRC cells. An investigation of its molecular mechanism confirmed that the cytotoxic activity of DHPITO is mediated through the targeting of microtubules with the promotion of subsequent microtubule polymerisation. With its microtubule‑stabilising ability, DHPITO also consistently arrested the cell cycle of the CRC cells at the G2/M phase by promoting the phosphorylation of histone 3 and the accumulation of EB1 at the cell equator, reduced the levels of CRC cell migration and invasion, and induced cellular apoptosis. Furthermore, the compound could suppress both tumour size and tumour weight in a CRC xenograft model without any obvious side effects. Taken together, the findings of the present study reveal the antiproliferative and antitumour mechanisms through which DHPITO exerts its activity, indicating its potential as a putative chemotherapeutic agent and lead compound with a novel structure.
... Moreover, diallyl sulfide (DAS), diallyl disulfide (DADS) and diallyl trisulfide (DATS) could promote the expression of multidrug-resistant genes in colo 205 human colon cancer cells [145]. In addition, dibenzyl tetrasulfide, a derivative of diallyl tetrasulfide, was also identified as a mitogenic inhibitor and apoptosis inducer in colon cancer cells and induced cell type-dependent autophagic damage involving p62 [146]. ...
Hydrogen sulfide (H2S) is an important signaling molecule in colorectal cancer (CRC). It is produced in the colon by the catalytic synthesis of the colonocytes' enzymatic systems and the release of intestinal microbes, and is oxidatively metabolized in the colonocytes' mitochondria. Both endogenous H2S in colonic epithelial cells and exogenous H2S in intestinal lumen contribute to the onset and progression of CRC. The up-regulation of endogenous synthetases is thought to be the cause of the elevated H2S levels in CRC cells. Different diagnostic probes and combination therapies, as well as tumor treatment approaches through H2S modulation, have been developed in recent years and have become active area of investigation for the diagnosis and treatment of CRC. In this review, we focus on the specific mechanisms of H2S production and oxidative metabolism as well as the function of H2S in the occurrence, progression, diagnosis, and treatment of CRC. We also discuss the present challenges and provide insights into the future research of this burgeoning field.
... The decreased cell killing effect, observed when autophagosome formation was inhibited by 3MA, demonstrated that blockage of autophagosome traffic and the accumulation of autophagosomes promotes paclitaxel-induced cancer cell death [144]. In line with these findings, several new tubulin binding agents have been shown to activate apoptosis as a result of autophagic flux inhibition in cancer cells [145][146][147][148]. It could be envisaged that induction of autophagosome formation in response to prolonged mitotic arrest and/or mitotic slippage, together with the reduction of autophagosome turnover by flux blockage, could result in the accumulation of autophagosomes, the intracellular persistence of toxic substances and/or damaged organelles, the production of oxygen reactive species, and cytotoxicity [149]. ...
Microtubules are key components of the cytoskeleton of eukaryotic cells. Microtubule dynamic instability together with the “tubulin code” generated by the choice of different α- and β- tubulin isoforms and tubulin post-translational modifications have essential roles in the control of a variety of cellular processes, such as cell shape, cell motility, and intracellular trafficking, that are deregulated in cancer. In this review, we will discuss available evidence that highlights the crucial role of the tubulin code in determining different cancer phenotypes, including metastatic cell migration, drug resistance, and tumor vascularization, and the influence of modulating tubulin-modifying enzymes on cancer cell survival and aggressiveness. We will also discuss the role of post-translationally modified microtubules in autophagy—the lysosomal-mediated cellular degradation pathway—that exerts a dual role in many cancer types, either promoting or suppressing cancer growth. We will give particular emphasis to the role of tubulin post-translational modifications and their regulating enzymes in controlling the different stages of the autophagic process in cancer cells, and consider how the experimental modulation of tubulin-modifying enzymes influences the autophagic process in cancer cells and impacts on cancer cell survival and thereby represents a new and fruitful avenue in cancer therapy.
... The complex protein-ligand is analyzed by Mass Spectrometry and the direct detection of the ligand reflects its potential inhibition activity against the target. Screening tests have already been developed for the ligands of tubulin [2,3], dihydroxyfolate reductase (DHFR) [4] and recently for reversible and irreversible ligands of CDC25 phosphatases (isoforms A et C) [5]. This approach demonstrates its effectiveness with Madagascar periwinkle for tubulin, with Colchicum and green tea for DHFR and some promising plants are currently evaluated on CDC25s. ...
Oxidative reactions are vital but also cause important stresses and cellular damages resulting in cancers, cardiovascular or neurodegenerative diseases. Antioxidant secondary metabolites from plant can be mobilized for the cell defense and their main source is precisely the food intake such as vegetables, fruits or beverages. Screening natural active metabolites in plants requires different analytical techniques among which mass spectrometry became one of the most popular, not just because of its ability to provide structural information on involved molecules but also because this technique belongs to the arsenal of diagnostic tool for the determination of biological activities.
... Compounds such as allicin and polysulfides found in many Allium plants, for instance, can interact with the "cellular thiolstat" [4]. Such agents are moderately reactive, affect numerous cellular processes, exhibit pronounced antioxidant and also cyto-toxic activities and, therefore, have been linked to certain preventive or even therapeutic actions [5][6][7][8][9][10]. Together, a balanced cocktail of such biologically active nutritional components may provide a promising and also more applicable alternative to extensive medication. ...
Numerous secondary metabolites found in edible plants modulate intracellular redox processes and are suggested to prevent certain diseases, especially in ageing organisms. Since such nutraceuticals provide the basis for new and innovative designer diets and therapies, extracting these substances and their potential from plants has become a focus of research, with nanotechnology and natural nanoparticles at the centre of some of these developments.
... Although additional experiments are needed to determine whether p21 is in the cytosol or the nucleus during mitotic phase arrest, CPT-induced p21 might act in the cytosol to trigger the cell survival signal, and free, CPT-induced cyclin B1-Cdk1 complexes may monitor mitotic phase progression. Yagdi Efe et al. (2017) recently suggested that cell cycle progression and apoptosis may be closely linked, and thus, cell cycle checkpoint molecules are prerequisites for apoptosis; in particular, during mitotic phase arrest, apoptosis appears to be restrained. We previously found that apoptosis does not occur in response to CPT treatment by activating endoplasmic reticulum stress-mediated autophagy (Jayasooriya et al., 2018), thus promoting endoreduplication. ...
Camptothecin (CPT) is a popular therapeutic agent that targets topoisomerase I. Our findings demonstrated that CPT-induced microtubule polymerization results in markedly increased histone H3 phosphorylation. CPT also enhanced interactions between the mitotic checkpoint proteins, Mad2 and Cdc20, and thereby increased mitotic arrest. Transient knockdown of Mad2 completely restored cell cycle progression from CPT-induced mitotic arrest, while simultaneously reduced cyclin B1 and Cdk1 expression. Moreover, we found that c-Jun N-terminal kinase (JNK) acts upstream of Sp1, which upregulates p21-mediated mitotic arrest in response to CPT; furthermore, knockdown of p21 restored cell cycle progression, while inhibition of Cdks completely restored cell cycle progression from CPT-induced mitotic arrest. We hypothesized that, during mitotic arrest in response to CPT, cell survival signaling blocks apoptosis, thereby enhancing mitotic arrest. As expected, a caspase-9 inhibitor, z-LEHD-FMK, and an autophagy inhibitor, 3-methyladenine (3 MA), significantly diminished CPT-induced mitotic arrest. On the other hand, when Mad2 was depleted, z-LEHD-FMK and 3 MA markedly increased apoptosis, and restored cell cycle progression. Taken together, these results suggest that CPT decodes the action of topoisomerase I-mediated tubulin targeting drugs, leading to mitotic arrest by upregulating Mad2 through the JNK-mediated Sp1 pathway and autophagy formation from tubulin polymerization.
... Since not all cysteine proteins are equally exposed or prone to oxidation, and their reactivity towards different oxidative stressors may differ, the cellular thiolstat describes a complicated and at the same time sophisticated cellular network whose individual players and their equally individual thermodynamic and kinetic Bproneness^towards oxidation are currently being explored by a range of cell-based and in vitro Fig. 2 The concept of the Bcellular thiolstat^which explains some of the cellular responses triggered by internal and externally induced changes to the intracellular redox equilibrium. Please note that this concept is a working hypothesis in need of careful analysis and is also prone to continuous refinement and expansion, for instance in the context of metal binding s t u d i e s a n d m e a s u r e m e n t s ( s e e t h e s e c t i o n on BProteomics, chemogenetic phenotype profiling and intracellular diagnostics^) [38][39][40][41][42]. ...
Purpose of Review
The article describes how recent advances in chalcogen Redox Biology shape the future of nutrition, drug design, agriculture, and environmental management.
Recent Findings
Since the turn of the Millennium, the biological chemistry of redox active sulfur species has witnessed various significant developments, with cysteine side-chains in proteins and enzymes emerging as centers of redox signaling and control and inspiring new concepts, such as the sulfur redoxome, the sulfenome, and the cellular thiolstat. Since then, it has emerged that redox sensitive cysteine residues are preferred targets of Reactive Sulfur Species (RSS), certain metal ions, and the emerging class of Reactive Selenium Species (RSeS). In addition, the cellular redoxome provides the basis for targeted redox modulation, for instance via nutritional intervention in the sick and elderly; it paves the way for highly selective catalytic sensor/effector agents active against a spectrum of redox-related diseases and lightens up possible avenues leading towards green phyto-protectants, often in cahoots with modern nanotechnology. Whilst the activity of redox-active food ingredients and multifunctional redox-modulating compounds on and in cells is complicated, modern techniques such as redox proteomics and chemogenetic phenotype profiling in combination with fluorescent-based “intracellular diagnostics” can be employed to illuminate certain changes, pathways, and eventually, also mode(s) of action.
Summary
Undoubtedly, chalcogen-based redox systems will shape future research and development in nutrition, drug design, cosmetics, green agriculture, and waste management.
... The upregulated genes were predominantly enriched in 'cell cycle' (hsa04110), 'RNA transport' (hsa03013) and 'DNA replication' (hsa03030) pathways, which is consistent with the findings of a previous study investigating gene involvement in tumor pathogenesis (21). The mammalian cell cycle is highly organized and regulated to ensure the correct functioning of cell division and other biological activities (22). The four phases of the cell cycle (G0/G1, S, G2 and M), are regulated by numerous cyclin-dependent kinases (CDKs) (23). ...
To identify biologically relevant genes associated with the pathogenesis of colorectal cancer (CRC), genome wide expression profiles of 17 pairs of CRC tumor and adjacent tissues, previously published in a DNA microarray study, were analyzed. Cytoscape, String tools and DAVID tools were used to investigate the biological pathways encoded by the genes identified as being either upregulated or downregulated in CRC, to determine protein‑protein interactions and to identify potential hub genes associated with CRC. As a result, a total of 3,264 genes were identified as being differentially expressed in CRC and adjacent tissues, including 1,594 downregulated and 1,670 upregulated genes. Furthermore, 306 genes were revealed to be clustered in a complex interaction network, and the top 20 hub genes in this network were determined by application of the Matthews Correlation Coefficient algorithm. In addition, the patterns of the expression levels of the 20 hub genes were investigated using reverse transcription‑quantitative polymerase chain reaction. Gene Ontology analysis revealed that four of the 20 hub genes encoded small subunit processome components (UTP3 small subunit processome component; UTP14 small subunit processome component; UTP 18 small subunit processome component; and UTP20 small subunit processome component) and a further four encoded WD repeat domains (WD repeat‑containing protein 3, WD repeat domain 12, WD repeat‑containing protein 43 and WD repeat‑containing protein 75). In conclusion, the present DNA microarray study identified genes involved in the pathogenesis of CRC. Furthermore, it was revealed that hub genes identified from among the total identified upregulated and downregulated genes in CRC encoding subunit processome components and WD repeat domains may represent novel target molecules for future treatments of CRC.
... First of all, the catalysts are not selective for just one protein, for instance, one particular receptor or enzyme, and hence differ from the kind of classic inhibitors mentioned in the Introduction. Similar to the cytotoxic transition metal complexes discussed in Section 3, such quinone and chalcogen-based catalysts are rather indiscriminate and simultaneously target numerous proteins as their perceived substrate(s), usually but not always particularly redox sensitive cysteine proteins with cysteine accessible for modification, such as β-tubulin [119]. Yet in clear contrast to the noble metal catalysts developed by Sadler and colleagues at Warwick, chalcogen-based catalysts do not simply deplete the cell of its fuel or GSH, or poison the cell with ROS or unnatural products. ...
Catalysts are employed in many areas of research and development where they combine high efficiency with often astonishing selectivity for their respective substrates. In biology, biocatalysts are omnipresent. Enzymes facilitate highly controlled, sophisticated cellular processes, such as metabolic conversions, sensing and signalling, and are prominent targets in drug development. In contrast, the therapeutic use of catalysts per se is still rather limited. Recent research has shown that small molecule catalytic agents able to modulate the redox state of the target cell bear considerable promise, particularly in the context of inflammatory and infectious diseases, stroke, ageing and even cancer. Rather than being “active” on their own in a more traditional sense, such agents develop their activity by initiating, promoting, enhancing or redirecting reactions between biomolecules already present in the cell, and their activity therefore depends critically on the predisposition of the target cell itself. Redox catalysts, for instance, preferably target cells with a distinct sensitivity towards changes in an already disturbed redox balance and/or increased levels of reactive oxygen species. Indeed, certain transition metal, chalcogen and quinone agents may activate an antioxidant response in normal cells whilst at the same time triggering apoptosis in cancer cells with a different pre-existing “biochemical redox signature” and closer to the internal redox threshold. In pharmacy, catalysts therefore stand out as promising lead structures, as sensor/effector agents which are highly effective, fairly selective, active in catalytic, i.e., often nanomolar concentrations and also very flexible in their structural design.
Purpose
The aim of this review is to highlight the potential of garlic phytoconstituents as antitumor agents in colorectal cancer management based on their molecular mechanisms of action, while asking if their consumption, as part of the human diet, might contribute to the prevention of colorectal cancer.
Methods
To gather information on appropriate in vitro, in vivo and human observational studies on this topic, the keywords “Allium sativum”, “garlic”, “colorectal cancer”, “antitumor effect”, “in vitro”, “in vivo”, “garlic consumption” and “colorectal cancer risk” were searched in different combinations in the international databases ScienceDirect, PubMed and Google Scholar. After duplicate and reviews removal, 61 research articles and meta-analyses published between 2000 and 2022 in peer-reviewed journals were found and included in this review.
Results
Garlic (Allium sativum) proves to be a rich source of compounds with antitumor potential. Garlic-derived extracts and several of its individual constituents, especially organosulfur compounds such as allicin, diallyl sulfide, diallyl disulfide, diallyl trisulfide, diallyl tetrasulfide, allylmethylsulfide, S-allylmercaptocysteine, Z-ajoene, thiacremonone and Se-methyl-L-selenocysteine were found to possess cytotoxic, cytostatic, antiangiogenic and antimetastatic activities in different in vitro and in vivo models of colorectal cancer. The molecular mechanisms for their antitumor effects are associated with the modulation of several well-known signaling pathways involved in cell cycle progression, especially G1-S and G2-M transitions, as well as both the intrinsic and extrinsic apoptotic pathways. However, even though in various animal models some of these compounds have chemopreventive effects, based on different human observational studies, a diet rich in garlic is not consistently associated with a lower risk of developing colorectal cancer.
Conclusion
Independent of the impact of garlic consumption on colorectal cancer initiation and promotion in humans, its constituents might be good candidates for future conventional and/or complementary therapies, based on their diverse mechanisms of action.
Plant‐derived natural products (NPs) with electrophilic functional groups engage various subsets of the proteome via covalent modification of nucleophilic cysteine residues. This electrophile‐nucleophile interaction can change protein conformation, alter protein function, and modulate their biological action. The biological significance of these covalent protein modifications in health and disease has been increasingly recognized. One way to understand covalent NP‐protein interactions is to utilize traditional proteomics and modern mass spectrometry (MS)‐based proteomic strategies. These strategies have proven effective in uncovering specific NP protein targets and are critical first steps that allow for a much deeper understanding of the ability of NPs to modulate cellular processes. Here, we review plant‐derived NPs that covalently modify proteins, the biological significance of these covalent modifications, and the different proteomic strategies that have been employed to study these NP‐protein interactions.
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Akt, a crucial protein involved in a variety of signaling pathways in cancer, acts as an important regulator of survival in hepatocellular carcinoma (HCC), and provides curative option for the related drugs development. We have found an active phenanthroindolizidine alkaloid, (13aR,14R)-9,11,12,13,13a,14-hexahydro-3,6,7-trimethoxydibenzo[f,h]pyrrolo[1,2-b]isoquinolin-14-ol (HTBPI), is a promising Akt inhibitor effective in the suppression of HCC cells proliferation through stimulating apoptotic and autophagic capability in vivo and in vitro. Treatment of HTBPI combined with a classical autophagy-lysosomal inhibitor (bafilomycin A1), could enhance stimulation effects of apoptosis on HCC cell lines. In addition, we confirmed HTBPI targeting Akt, occupied the kinase binding domain (Thr 308) of Akt to inactivate its function by CETSA and DARTS assay. In contrast, ectopic Akt-induced overexpression significantly abrogated inhibitory effects of HTBPI on cell viability and proliferation. Furthermore, high p-Akt (Thr 308) expression is collated with liver tumor formation and poor survival in HCC patients. In conclusions, HTBPI impeded HCC progress through regulation of apoptosis and autophagy machinery via interaction with p-Akt (Thr 308). This may provide potential molecular candidate by targeting Akt for the therapy of HCC patients. © 2020 Federation of American Societies for Experimental Biology
Significance:
Sulfur has a critical role in protein structure/function and redox status/signaling in all living organisms. Although hydrogen sulfide (H2S) and sulfane sulfur (SS) are now recognized as central players in physiology and pathophysiology, the full scope and depth of sulfur metabolome's impact on human health and healthy longevity has been vastly underestimated and is only starting to be grasped. Since many pathological conditions have been related to abnormally low levels of H2S/SS in blood and/or tissues, and are amenable to treatment by H2S supplementation, development of safe and efficacious H2S donors deserves to be undertaken with a sense of urgency; these prodrugs also hold the promise of becoming widely used for disease prevention and as antiaging agents.
Recent Advances:
Supramolecular tuning of the properties of well-known molecules comprising chains of sulfur atoms (diallyl trisulfide [DATS], S8) was shown to lead to improved donors such as DATS-loaded polymeric nanoparticles and SG1002. Encouraging results in animal models have been obtained with SG1002 in heart failure, atherosclerosis, ischemic damage, and Duchenne muscular dystrophy; with TC-2153 in Alzheimer's disease, schizophrenia, age-related memory decline, fragile X syndrome, and cocaine addiction; and with DATS in brain, colon, gastric, and breast cancer.
Critical Issues:
Mode-of-action studies on allyl polysulfides, benzyl polysulfides, ajoene, and 12 ring-substituted organic disulfides and thiosulfonates led several groups of researchers to conclude that the anticancer effect of these compounds is not mediated by H2S and is only modulated by reactive oxygen species, and that their central model of action is selective protein S-thiolation.
Future Directions:
SG1002 is likely to emerge as the H2S donor of choice for acquiring knowledge on this gasotransmitter's effects in animal models, on account of its unique ability to efficiently generate H2S without byproducts and in a slow and sustained mode that is dose independent and enzyme independent. Efficient tuning of H2S donation characteristics of DATS, dibenzyl trisulfide, and other hydrophobic H2S prodrugs for both oral and parenteral administration will be achieved not only by conventional structural modification of a lead molecule but also through the new "supramolecular tuning" paradigm.
Accurate and sensitive identification of DNA mutations in tumor cells is critical to the diagnosis, prognosis and personalized therapy of cancer. Conventional polymerase chain reaction (PCR)-based methods are limited by the complicated amplification process. Herein, an amplification-free surface enhanced Raman spectroscopy (SERS) approach which directly detects point mutations in cancer cells has been proposed. A highly sensitive and uniform SERS substrate was fabricated using gold@silver core-shell nanorods, achieving an enhancement factor of 1.85×106. By combining the SERS-active nanosubstrate with molecular beacon probes, the limit of detection reached down to 50 fM. To enable parallel analysis and automated operation, the SERS sensor was integrated into a microfluidic chip. This novel chip-based assay was able to differentiate between mutated and wild-type KRAS genes among a variety of other nucleic acids from cancer cells in 40 min. Owing to the simple operation and fast analysis, the SERS-based DNA assay chip could potentially provide insights into clinical cancer theranostics in an easy and inexpensive manner at the point of care.
Le cancer colorectal est une cause majeure de morbidité et de mortalité dans le monde entier. Des études épidémiologiques révèlent une corrélation inverse entre le risque de développer un cancer du côlon et un régime alimentaire riche en ail. De nombreux travaux scientifiques rapportent l'activité anti-cancéreuse des polysulfures de diallyle (PSDA) dérivés de l'ail dans divers types de cancer in vitro et in vivo. Le mécanisme d'action le mieux connu repose sur l'induction de l'arrêt mitotique suivi de l'apoptose. La tubuline est identifiée comme nouvelle cible thérapeutique des PSDA. La tubuline est fondamental dans la progression de l'autophagie, source nutritionnelle essentielle pour le développement du cancer au stade avancé, et l'activation de l'autophagie joue un rôle de chimiorésistance dans le traitement du cancer du côlon. L'hypothèse de ce projet est que les PSDA dérivés de l'ail interagissent avec la tubuline pour altérer l'organisation du réseau microtubulaire responsable de l'inhibition de la prolifération cellulaire et de la modulation de l'autophagie dans le cancer du côlon. Dans un premier temps, nous avons analysé l'impact du TTSDA/TTSDB sur le réseau microtubulaire. Nous avons montré que le TTSDA/TTSDB interagissait avec la tubuline par spectrométrie en masse. Nous avons montré que l'organisation microtubulaire est altérée dans les trois lignées cellulaires : HT-29 (mutées BRAF), SW480 (mutées KRAS) et SW620 (mutées KRAS, métastatiques), plus sensibles au TTSDB que le TTSDA. Dans un deuxième temps, nous avons étudié le rôle anticancéreux du TTSDB dans le cancer du côlon. Nous avons montré que le TTSDB induisait un arrêt mitotique suivi de la mort cellulaire dans toutes lignées confondues. Son activité antiproliférative est validée dans un système de culture 3D et in vivo. Nous avons aussi montré que l'effet du TTSDB est comparable aux agents altérant les microtubules. Dans un troisième temps, nous avons évalué l'impact du TTSDB dans l'autophagie. L'inhibition de l'autophagie est accompagnée par l'accumulation de la protéine p62, qui joue un rôle de survie dans les cellules HT-29 uniquement. Ensemble, nous avons identifié l'autophagie comme mécanisme de survie lors de l'arrêt mitotique prolongé en fonction du type cellulaire. Cette étude permettra d'envisager un ciblage thérapeutique selon le profil génétique du cancer du côlon
The ubiquitin–proteasome system (UPS) and autophagy are two distinct and interacting proteolytic systems. They play critical roles in cell survival under normal conditions and during stress. An increasing body of evidence indicates that ubiquitinated cargoes are important markers of degradation. p62, a classical receptor of autophagy, is a multifunctional protein located throughout the cell and involved in many signal transduction pathways, including the Keap1–Nrf2 pathway. It is involved in the proteasomal degradation of ubiquitinated proteins. When the cellular p62 level is manipulated, the quantity and location pattern of ubiquitinated proteins change with a considerable impact on cell survival. Altered p62 levels can even lead to some diseases. The proteotoxic stress imposed by proteasome inhibition can activate autophagy through p62 phosphorylation. A deficiency in autophagy may compromise the ubiquitin–proteasome system, since overabundant p62 delays delivery of the proteasomal substrate to the proteasome despite proteasomal catalytic activity being unchanged. In addition, p62 and the proteasome can modulate the activity of HDAC6 deacetylase, thus influencing the autophagic degradation.
Resistance to apoptotic cell death1 owing to overexpression of anti-apoptotic Bcl-2 family proteins including Bcl-2, Bcl-xL or Mcl-1 is considered an interesting druggable target for the treatment of hematological malignancies including acute myeloid leukemia. In fact, BH3 mimetics2 like ABT-199 (venetoclax)3 reverse the inhibitory function of anti-apoptotic Bcl-2 proteins.4 Dependency on Bcl-2 family protein expression requests BH3 profiling to efficiently stratify patients potentially benefiting from ABT-199 therapy.5 Most often, Mcl-1 is considered a main resistance factor2 and recently a first class of selective Mcl-1 inhibitors was characterized.6 As an alternative to functional inhibitors, we previously described proteasome-dependent downregulation of Mcl-1 expression7,8 by cardiac glycoside UNBS1450.8–10 We hypothesize here that a combination of UNBS1450 with a BH3 mimetic would affect acute myeloid leukemia (AML) subtypes especially ‘addicted’ to Mcl-1. To provide a targeted therapeutic approach, we describe the synergistic antileukemic effect of ABT-199 with UNBS1450 in cell lines, colony formation assays, zebrafish xenografts and validate results in primary cells from 23 de novo AML patients.
Metastases cause recurrence and mortality for patients with colorectal carcinomas (CRC). In present study, we evaluated heterogeneity on drug resistance and its underlying mechanism between metastatic and primary CRC. Immunohistochemical results from clinical tissue microarray (TMA) suggested that the expression concordance rates of cancer stem cells (CSCs) and drug resistance relative proteins between lymph-node metastatic and primary CRC foci were low. The apoptotic and proliferation indexes in metastasis CRC specimens were decreased compared with primary. In vitro experimental results indicated that the migration and invasion abilities were upregulated in metastatic cells SW620 compared with primary cells SW480, the cellular efflux ability and WNT/β-catenin activity were also upregulated in SW620 cells. After 5-fluorouracil (5-Fu) treatment, the reduction in the proportion of cell apoptosis, CD133 and TERT expression levels in SW620 were lower than that in SW480 cells. Bioinformatics analysis in whole-genome transcriptional profiling results between metastatic and primary CRC cells suggested that differentially expressed genes were mainly centered on well-characterized signaling pathways including WNT/β-catenin, cell cycle and cell junction. Collectively, heterogeneity of drug resistant was present between metastatic and primary CRC specimens and cell lines, the abnormal activation of WNT/β-catenin signaling pathway could be a potential molecular leading to drug resistant ability enhancing in metastatic CRC cells.
limma is an R/Bioconductor software package that provides an integrated solution for analysing data from gene expression experiments. It contains rich features for handling complex experimental designs and for information borrowing to overcome the problem of small sample sizes. Over the past decade, limma has been a popular choice for gene discovery through differential expression analyses of microarray and high-throughput PCR data. The package contains particularly strong facilities for reading, normalizing and exploring such data. Recently, the capabilities of limma have been significantly expanded in two important directions. First, the package can now perform both differential expression and differential splicing analyses of RNA sequencing (RNA-seq) data. All the downstream analysis tools previously restricted to microarray data are now available for RNA-seq as well. These capabilities allow users to analyse both RNA-seq and microarray data with very similar pipelines. Second, the package is now able to go past the traditional gene-wise expression analyses in a variety of ways, analysing expression profiles in terms of co-regulated sets of genes or in terms of higher-order expression signatures. This provides enhanced possibilities for biological interpretation of gene expression differences. This article reviews the philosophy and design of the limma package, summarizing both new and historical features, with an emphasis on recent enhancements and features that have not been previously described.
© The Author(s) 2015. Published by Oxford University Press on behalf of Nucleic Acids Research.
Autophagy is crucial for cellular homeostasis and plays important roles in tumorigenesis. FIP200 (FAK family-interacting protein of 200 kDa) is an essential autophagy gene required for autophagy induction, functioning in the ULK1-ATG13-FIP200 complex. Our previous studies showed that conditional knockout of FIP200 significantly suppressed mammary tumorigenesis, which was accompanied by accumulation of p62 in tumor cells. However, it is not clear whether FIP200 is also required for maintaining tumor growth and how the increased p62 level affects the growth in autophagy-deficient FIP200-null tumors in vivo. Here, we describe a new system to delete FIP200 in transformed mouse embryonic fibroblasts as well as mammary tumor cells following their transplantation and show that ablation of FIP200 significantly reduced growth of established tumors in vivo. Using similar strategies, we further showed that either p62 knockdown or p62 deficiency in established FIP200-null tumors dramatically impaired tumor growth. The stimulation of tumor growth by p62 accumulation in FIP200-null tumors is associated with the up-regulated activation of the NF-κB pathway by p62. Last, we showed that overexpression of the autophagy master regulator TFEB(S142A) increased the growth of established tumors, which correlated with the increased autophagy of the tumor cells. Together, our studies demonstrate that p62 and autophagy synergize to promote tumor growth, suggesting that inhibition of both pathways could be more effective than targeting either alone for cancer therapy.
Both at a basal level and after induction (especially in response to nutrient starvation), the function of autophagy is to allow cells to degrade and recycle damaged organelles, proteins and other biological constituents. Here, we focus on the role microtubules have in autophagosome formation, autophagosome transport across the cytoplasm and in the formation of autolysosomes. Recent insights into the exact relationship between autophagy and microtubules now point to the importance of microtubule dynamics, tubulin post-translational modifications and microtubule motors in the autophagy process. Such factors regulate signaling pathways that converge to stimulate autophagosome formation. They also orchestrate the movements of pre-autophagosomal structures and autophagosomes or more globally organize and localize immature and mature autophagosomes and lysosomes. Most of the factors that now appear to link microtubules to autophagosome formation or to autophagosome dynamics and fate were identified initially without the notion that sequestration, recruitment and/or interaction with microtubules contribute to their function. Spatial and temporal coordination of many stages in the life of autophagosomes thus underlines the integrative role of microtubules and progressively reveals hidden parts of the autophagy machinery.
Background:
Mutations in the Kirsten Ras (KRAS) oncogene are common in colorectal cancer (CRC). The role of KRAS-mutation status as a prognostic factor, however, is unclear. We evaluated the relationship between KRAS-mutation status and CRC survival, considering heterogeneity in this association by tumour and patient characteristics.
Methods:
The population-based study included individuals diagnosed with CRC between 1998–2007 in Western Washington State. Tumour specimens were tested for KRAS exon 2 mutations, the BRAF p.V600E mutation, and microsatellite instability (MSI). We used Cox regression to estimate hazard ratios (HR) and 95% confidence intervals (CI) for the association between KRAS-mutation status and disease-specific and overall survival. Stratified analyses were conducted by age, sex, tumour site, stage, and MSI. We conducted additional analyses combining KRAS-mutation, BRAF-mutation, and MSI status.
Results:
Among 1989 cases, 31% had KRAS-mutated CRC. Kirsten Ras (KRAS)-mutated CRC was associated with poorer disease-specific survival (HR=1.37, 95% CI: 1.13–1.66). This association was not evident in cases who presented with distant-stage CRC. Cases with KRAS-wild-type/BRAF-wild-type/MSI-high CRC had the most favourable prognosis; those with CRC exhibiting a KRAS- or BRAF-mutation and no MSI had the poorest prognosis. Patterns were similar for overall survival.
Conclusion:
Kirsten Ras (KRAS)-mutated CRC was associated with statistically significantly poorer survival after diagnosis than KRAS-wild-type CRC.
Although p62/SQSTM1 was initially identified as an essential mediator of NFκB signaling, several recent studies have also highlighted its important role at the crossroad between the mTOR or MAPK signaling pathways and selective autophagy. The p62 structure containing important interaction domains attests to the ability of this protein to regulate and modulate the activation of these signaling pathways during tumor formation and propagation. The second very important function of this protein is to act as a molecular adaptor between the autophagic machinery and its substrates. Consequently, p62 is degraded following an increase in autophagic flux for which this protein currently serves as an indicator. However, the measurement of p62 expression strictly as a marker of autophagic flux is still controversial and can be misinterpreted mainly because this protein is subject to complex regulation at both the transcriptional and post-translational levels. Finally, because p62 is an autophagic substrate, it acts as a molecular link between cancer and autophagy by conferring a high level of selectivity through the degradation of important signaling molecules.
The common approach to the multiplicity problem calls for controlling the familywise error rate (FWER). This approach, though, has faults, and we point out a few. A different approach to problems of multiple significance testing is presented. It calls for controlling the expected proportion of falsely rejected hypotheses – the false discovery rate. This error rate is equivalent to the FWER when all hypotheses are true but is smaller otherwise. Therefore, in problems where the control of the false discovery rate rather than that of the FWER is desired, there is potential for a gain in power. A simple sequential Bonferroni-type procedure is proved to control the false discovery rate for independent test statistics, and a simulation study shows that the gain in power is substantial. The use of the new procedure and the appropriateness of the criterion are illustrated with examples.
In mice, the mdr1a and mdr1b genes encode drug-transporting proteins that can cause multidrug resistance in tumor cells by lowering intracellular drug levels. These P-glycoproteins are also found in various normal tissues such as the intestine. Because mdr1b P-glycoprotein is not detectable in the intestine, mice with a homozygously disrupted mdr1a gene [mdr1a(-/-) mice] do not contain functional P-glycoprotein in this organ. We have used these mdr1a(-/-) mice to study the effect of gut P-glycoprotein on the pharmacokinetics of paclitaxel. The area under the plasma concentration-time curves was 2- and 6-fold higher in mdr1a(-/-) mice than in wild-type (wt) mice after i.v. and oral drug administration, respectively. Consequently, the oral bioavailability in mice receiving 10 mg paclitaxel per kg body weight increased from only 11% in wt mice to 35% in mdr1a(-/-) mice. The cumulative fecal excretion (0-96 hr) was markedly reduced from 40% (after i.v. administration) and 87% (after oral administration) of the administered dose in wt mice to below 3% in mdr1a(-/-) mice. Biliary excretion was not significantly different in wt and mdr1a(-/-) mice. Interestingly, after i.v. drug administration of paclitaxel (10 mg/kg) to mice with a cannulated gall bladder, 11% of the dose was recovered within 90 min in the intestinal contents of wt mice vs. <3% in mdr1a(-/-) mice. We conclude that P-glycoprotein limits the oral uptake of paclitaxel and mediates direct excretion of the drug from the systemic circulation into the intestinal lumen.
Statistical methods are used to test for the differential expression of genes in microarray experiments. The most widely used methods successfully test whether the true differential expression is different from zero, but give no assurance that the differences found are large enough to be biologically meaningful.
We present a method, t-tests relative to a threshold (TREAT), that allows researchers to test formally the hypothesis (with associated p-values) that the differential expression in a microarray experiment is greater than a given (biologically meaningful) threshold. We have evaluated the method using simulated data, a dataset from a quality control experiment for microarrays and data from a biological experiment investigating histone deacetylase inhibitors. When the magnitude of differential expression is taken into account, TREAT improves upon the false discovery rate of existing methods and identifies more biologically relevant genes.
R code implementing our methods is contributed to the software package limma available at http://www.bioconductor.org.
Although apoptosis can be induced by the enforced expression of exogenously introduced c-myc genes, it is not clear whether overexpression resulting from the amplification of the resident c-myc gene in tumor cells is sufficient to induce apoptosis. We have investigated the relationship between c-myc gene amplification and the propensity of tumor cells to undergo apoptosis, using the SW613-12A1 and SW613-B3 cell lines, which are representatives, respectively, of tumorigenic and non-tumorigenic clones isolated from the SW613-S human colon carcinoma cell line. Tumorigenic clones are characterized by a high level of amplification and expression of the c-myc gene, whereas cells of non-tumorigenic clones have a small number of copies and a lower level of expression of this gene. Analysis of c-myc mRNA level in cells cultured under low serum conditions indicated that the expression of the gene is tightly regulated by serum growth factors in non-tumorigenic B3 cells, whereas it is poorly regulated in tumorigenic 12A1 cells, the level of mRNAs remaining relatively high in serum-starved 12A1 cells. Under these conditions, 12A1 cells showed clear evidence of apoptosis, whereas B3 cells were completely refractory to the induction of apoptosis. Moreover, the study of cell lines derived from non-tumorigenic apoptosis-resistant clones following the introduction by transfection of exogenous c-myc gene copies showed that they have acquired an apoptosisprone phenotype. Altogether, our results strongly suggest that deregulated c-myc expression due to high-level amplification confers an apoptosis-prone phenotype to tumor cells. The possible consequences of these observations for cancer therapy are discussed.
Unlabelled:
Microarray technology has become a standard molecular biology tool. Experimental data have been generated on a huge number of organisms, tissue types, treatment conditions and disease states. The Gene Expression Omnibus (Barrett et al., 2005), developed by the National Center for Bioinformatics (NCBI) at the National Institutes of Health is a repository of nearly 140,000 gene expression experiments. The BioConductor project (Gentleman et al., 2004) is an open-source and open-development software project built in the R statistical programming environment (R Development core Team, 2005) for the analysis and comprehension of genomic data. The tools contained in the BioConductor project represent many state-of-the-art methods for the analysis of microarray and genomics data. We have developed a software tool that allows access to the wealth of information within GEO directly from BioConductor, eliminating many the formatting and parsing problems that have made such analyses labor-intensive in the past. The software, called GEOquery, effectively establishes a bridge between GEO and BioConductor. Easy access to GEO data from BioConductor will likely lead to new analyses of GEO data using novel and rigorous statistical and bioinformatic tools. Facilitating analyses and meta-analyses of microarray data will increase the efficiency with which biologically important conclusions can be drawn from published genomic data.
Availability:
GEOquery is available as part of the BioConductor project.
Cardiac glycosides (CGs), prescribed to treat cardiovascular alterations, display potent anti-cancer activities. Despite their well-established target, the sodium/potassium (Na(+)/K(+))-ATPase, downstream mechanisms remain poorly elucidated. UNBS1450 is a hemi-synthetic cardenolide derived from 2″-oxovorusharin extracted from the plant Calotropis procera, which is effective against various cancer cell types with an excellent differential toxicity. By comparing adherent and non-adherent cancer cell types, we validated Mcl-1 as a general and early target of UNBS1450. A panel of CGs including cardenolides ouabain, digitoxin and digoxin as well as bufadienolides cinobufagin and proscillaridin A allowed us to generalize our findings. Our results show that Mcl-1, but not Bcl-xL nor Bcl-2, is rapidly downregulated prior to induction of apoptosis. From a mechanistic point of view, we exclude an effect on transcription and demonstrate involvement of a pathway affecting protein stability and requiring the proteasome in the early CG-induced Mcl-1 downregulation, without the involvement of caspases or the BH3-only protein NOXA. Strategies aiming at preventing UNBS1450-induced Mcl-1 downregulation by overexpression of a mutated, non-ubiquitinable form of the protein or the use of the proteasome inhibitor MG132 inhibited the compound's ability to induce apoptosis. Altogether our results point at Mcl-1 as a ubiquitous factor, downregulated by CGs, whose modulation is essential to achieve cell death.
Introduction.- Estimating the Survival and Hazard Functions.- The Cox Model.- Residuals.- Functional Form.- Testing Proportional Hazards.- Influence.- Multiple Events per Subject.- Frailty Models.- Expected Survival.
Glioblastoma multiforme (GBM) is the most common and lethal type of brain cancer. Proteasome inhibitors are emerging as a new class of anti-glioma agents; however, the mechanisms of their killing malignant cells are still unclear. We treated U87MG cells with the proteasome inhibitor MG132 and found that cell death correlated with caspase-8 activation and autophagy protein p62/SQSTM1.To explore the role of autophagy and p62/SQSTM1 in MG132-induced cancer cell death, we measured the alteration of MG132's cytotoxicity by autophagy inhibition, autophagy induction or variation of p62/SQSTM1 gene expression. Autophagy was activated upon MG132 treatment for short periods, while inhibition of autophagy aggravated MG132-induced cell death followed by high levels of p62/SQSTM1 and active caspase-8 (p18). Moreover, U87MG cell death was dependent on p62/SQSTM1, and its function required its C-terminus UBA domain to attenuate the MG132-induced cell death. The results suggest that p62/SQSTM1 is a potential contributor in determining the fate of U87MG cells deficient in proteolytic activity.
Natural compounds that target microtubules and disrupt the normal function of the mitotic spindle have proven to be one of the best classes of cancer chemotherapeutic drugs available in clinics to date. There is increasing evidence showing that even minor alteration of microtubule dynamics can engage the spindle checkpoint, arresting cell-cycle progression at mitosis and subsequently leading to cell death. Our improved understanding of tumor biology and our continued appreciation for what the microtubule targeting agents (MTAs) can do have helped pave the way for a new era in the treatment of cancer. The effectiveness of these agents for cancer therapy has been impaired, however, by various side effects and drug resistance. Several new MTAs have shown potent activity against the proliferation of various cancer cells, including resistance to the existing MTAs. Sustained investigation of the mechanisms of action of MTAs, development and discovery of new drugs, and exploring new treatment strategies that reduce side effects and circumvent drug resistance could provide more effective therapeutic options for patients with cancer. This review focuses on the successful cancer chemotherapy from natural compounds in clinical settings and the challenges that may abort their usefulness. Mol Cancer Ther; 1-10. ©2014 AACR.
Garlic-derived organosulfur compounds including diallyl polysulfides are well known for various health-beneficial properties and recent reports even point to a potential role of diallyl polysulfides as chemopreventive and therapeutic agents in cancer treatment due to their selective antiproliferative effects. In this respect, diallyl tri- and tetrasulfide are reported as strong inducers of an early mitotic arrest and subsequent apoptosis, but the underlying molecular mechanisms and the link between these two events are not yet fully elucidated. Our data revealed that diallyl tetrasulfide acts independently of reactive oxygen species and tubulin represents one of its major cellular targets. Tubulin depolymerization prevents the formation of normal spindle microtubules, thereby leading to G2/M arrest. Here, we provide evidence that c-jun N-terminal kinase, which is activated early in response to diallyl tetrasulfide treatment, mediates multisite phosphorylation and subsequent proteolysis of the anti-apoptotic protein B-cell lymphoma 2. As the latter event occurs concomitantly with the onset of apoptosis and the chemical c-jun N-terminal kinase inhibitor SP600125 not only prevented B-cell lymphoma 2 phosphorylation and proteolysis but also apoptosis following diallyl tetrasulfide treatment, we suggest that these c-jun N-terminal kinase-mediated modulations of B-cell lymphoma 2 represent the missing link connecting early microtubule inactivation to the induction of apoptosis.
Studies of cell-cell cohesion and cell-substratum adhesion have historically been performed on monolayer cultures adherent to rigid substrates. Cells within a tissue, however, are typically encased within a closely packed tissue mass in which cells establish intimate connections with many near-neighbors and with extracellular matrix components. Accordingly, the chemical milieu and physical forces experienced by cells within a 3D tissue are fundamentally different than those experienced by cells grown in monolayer culture. This has been shown to markedly impact cellular morphology and signaling. Several methods have been devised to generate 3D cell cultures including encapsulation of cells in collagen gels or in biomaterial scaffolds. Such methods, while useful, do not recapitulate the intimate direct cell-cell adhesion architecture found in normal tissues. Rather, they more closely approximate culture systems in which single cells are loosely dispersed within a 3D meshwork of ECM products. Here, we describe a simple method in which cells are placed in hanging drop culture and incubated under physiological conditions until they form true 3D spheroids in which cells are in direct contact with each other and with extracellular matrix components. The method requires no specialized equipment and can be adapted to include addition of any biological agent in very small quantities that may be of interest in elucidating effects on cell-cell or cell-ECM interaction. The method can also be used to co-culture two (or more) different cell populations so as to elucidate the role of cell-cell or cell-ECM interactions in specifying spatial relationships between cells. Cell-cell cohesion and cell-ECM adhesion are the cornerstones of studies of embryonic development, tumor-stromal cell interaction in malignant invasion, wound healing, and for applications to tissue engineering. This simple method will provide a means of generating tissue-like cellular aggregates for measurement of biomechanical properties or for molecular and biochemical analysis in a physiologically relevant model.
KRAS mutation occurs in 30% to 50% of colorectal cancers (CRCs) and has been suggested to be associated with proliferation and decreased apoptosis. In this study, we analyzed KRAS in 198 CRCs and compared the clinicopathologic variables between KRAS-mutated and wild-type CRCs. Also, a subset of 90 and 66 CRCs from this cohort underwent microsatellite instability testing and histomorphologic evaluation, and the frequency of microsatellite instability-high (MSI-H) and histomorphologic variables were compared between KRAS-mutated and wild-type CRCs. Clinicopathologic features (age, sex, and tumor site, depth, size, grade, and metastasis) were not different between KRAS-mutated and wild-type CRCs. Compared with wild-type KRAS CRCs, KRAS-mutated CRCs had a lower frequency of MSI-H (15% vs 42%; P = .015), a higher chance of having brisk mitosis (77% vs 43%, P = .022) and apoptosis (77% vs 28%; P = .00012), and a greater mean of mitotic figures (P = .0002) and apoptotic cells (P = .0008). KRAS mutation was associated with higher tumor cell turnover.
It is becoming increasingly clear that there is crosstalk between the apoptotic and autophagic pathways, with autophagy helping to contribute to cell death by providing energy to allow the energy-requiring programmed cell death process to complete, as well as degrading cellular material in its own right. Recent evidence has suggested that Atg proteins can themselves be targets of caspases, providing potential regulation of autophagy as well as uncovering novel functions for fragments derived from Atg proteins. However, to date there has not been a detailed examination of which Atg proteins may be the targets of which death proteases. We show that the majority of human Atg (hAtg) proteins can be cleaved by calpain 1, which is activated in some apoptotic paradigms, as well as other forms of death. We also show that hAtg3 is cleaved by caspases-3, -6 and -8, hAtg6 (Beclin 1) is cleaved by caspase-3 and -6, while hAtg9, hAtg7 and the hAtg4 homologues can be cleaved by caspase-3. Cleavage of Beclin 1 was also seen in apoptosis of HeLa cells induced by staurosporine and TRAIL, along with cleavage of Atg3 and Atg4C. There were subtle effects of caspase inhibition on GFP-LC3 lipidation but more marked effects on the formation of GFP-LC3 puncta (a marker of autophagosome formation) and p62 degradation, indicating that caspase cleavage of autophagy-related proteins can affect the autophagic process. Notably we show that p62 is a target for caspase-6 and -8 cleavage.
In addition to its demethylating properties, 2'-deoxy-5-azacytidine (DAC) induces cell cycle arrest, differentiation, cell sensitization to chemotherapy, and cell death. However, the mechanisms by which DAC induces antiproliferation via these processes and how they are interconnected remain unclear. In this study, we found that a clinically relevant concentration of DAC triggered erythroid and megakaryocytic differentiation in the human chronic myeloid leukemia (CML) K-562 and MEG-01 cell lines, respectively. In addition, cells showed a marked increase in cell size in both cell lines and a more adhesive cell profile for MEG-01. Furthermore, DAC treatment induced cellular senescence and autophagy as shown by β-galactosidase staining and by autophagosome formation, respectively. After prolonged DAC treatment, phosphatidyl serine exposure, nuclear morphology analysis, and caspase cleavage revealed an activation of mitochondrial-dependent apoptosis in CML cells. This activation was accompanied by a decrease of anti-apoptotic proteins and an increase of calpain activity. Finally, we showed that combinatory treatment of relatively resistant CML with DAC and either conventional apoptotic inducers or with an histone deacetylase inhibitor increased synergistically apoptosis. We therefore conclude that induction of differentiation, senescence, and autophagy in CML are a key in cell sensitization and DAC-induced apoptosis.
The standard treatment of patients with locally advanced rectal cancers comprises preoperative 5-fluorouracil-based chemoradiotherapy followed by standardized surgery. However, tumor response to multimodal treatment has varied greatly, ranging from complete resistance to complete pathologic regression. The prediction of the response is, therefore, an important clinical need.
To establish in vitro models for studying the molecular basis of this heterogeneous tumor response, we exposed 12 colorectal cancer cell lines to 3 μM of 5-fluorouracil and 2 Gy of radiation. The differences in treatment sensitivity were then correlated with the pretherapeutic gene expression profiles of these cell lines.
We observed a heterogeneous response, with surviving fractions ranging from 0.28 to 0.81, closely recapitulating clinical reality. Using a linear model analysis, we identified 4,796 features whose expression levels correlated significantly with the sensitivity to chemoradiotherapy (Q <.05), including many genes involved in the mitogen-activated protein kinase signaling pathway or cell cycle genes. These data have suggested a potential relevance of the insulin and Wnt signaling pathways for treatment response, and we identified STAT3, RASSF1, DOK3, and ERBB2 as potential therapeutic targets. The microarray measurements were independently validated for a subset of these genes using real-time polymerase chain reactions.
We are the first to report a gene expression signature for the in vitro chemoradiosensitivity of colorectal cancer cells. We anticipate that this analysis will unveil molecular biomarkers predictive of the response of rectal cancers to chemoradiotherapy and enable the identification of genes that could serve as targets to sensitize a priori resistant primary tumors.
The acquisition of genomic instability is a crucial feature in tumor development and there are at least 3 distinct pathways in colorectal cancer pathogenesis: the chromosomal instability (CIN), microsatellite instability, and CpG island methylator phenotype pathways. Most cases of colorectal cancer arise through the CIN pathway, which is characterized by widespread imbalances in chromosome number (aneuploidy) and loss of heterozygosity. It can result from defects in chromosomal segregation, telomere stability, and the DNA damage response, although the full complement of genes underlying CIN remains incompletely described. Coupled with the karyotypic abnormalities observed in CIN tumors are the accumulation of a characteristic set of mutations in specific tumor suppressor genes and oncogenes that activate pathways critical for colorectal cancer initiation and progression. Whether CIN creates the appropriate milieu for the accumulation of these mutations or vice versa remains a provocative and unanswered question. The goal of this review is to provide an updated perspective on the mechanisms that lead to CIN and the key mutations that are acquired in this pathway.
Impaired selective turnover of p62 by autophagy causes severe liver injury accompanied by the formation of p62-positive inclusions and upregulation of detoxifying enzymes. These phenotypes correspond closely to the pathological conditions seen in human liver diseases, including alcoholic hepatitis and hepatocellular carcinoma. However, the molecular mechanisms and pathophysiological processes in these events are still unknown. Here we report the identification of a novel regulatory mechanism by p62 of the transcription factor Nrf2, whose target genes include antioxidant proteins and detoxification enzymes. p62 interacts with the Nrf2-binding site on Keap1, a component of Cullin-3-type ubiquitin ligase for Nrf2. Thus, an overproduction of p62 or a deficiency in autophagy competes with the interaction between Nrf2 and Keap1, resulting in stabilization of Nrf2 and transcriptional activation of Nrf2 target genes. Our findings indicate that the pathological process associated with p62 accumulation results in hyperactivation of Nrf2 and delineates unexpected roles of selective autophagy in controlling the transcription of cellular defence enzyme genes.
Allelic loss of the essential autophagy gene beclin1 occurs in human cancers and renders mice tumor-prone suggesting that autophagy is a tumor-suppression mechanism. While tumor cells utilize autophagy to survive metabolic stress, autophagy also mitigates the resulting cellular damage that may limit tumorigenesis. In response to stress, autophagy-defective tumor cells preferentially accumulated p62/SQSTM1 (p62), endoplasmic reticulum (ER) chaperones, damaged mitochondria, reactive oxygen species (ROS), and genome damage. Moreover, suppressing ROS or p62 accumulation prevented damage resulting from autophagy defects indicating that failure to regulate p62 caused oxidative stress. Importantly, sustained p62 expression resulting from autophagy defects was sufficient to alter NF-kappaB regulation and gene expression and to promote tumorigenesis. Thus, defective autophagy is a mechanism for p62 upregulation commonly observed in human tumors that contributes directly to tumorigenesis likely by perturbing the signal transduction adaptor function of p62-controlling pathways critical for oncogenesis.
Naturally occurring organic sulfur compounds (OSCs), such as linear allylsulfides from Allium species, are attracting attention in cancer research, since several OSCs were shown to act beneficially both in chemoprevention and in chemotherapy, while hardly exerting any harmful side effects. Hence, we investigated the possible role of different OSCs in the treatment of leukemia. Thereby, we found that the compounds tested in this study induced apoptosis in U937 cells, with an efficiency depending on the number of sulfides, and selected the most promising candidate, diallyltetrasulfide (Al2S4), for detailed mechanistic studies. Here we show that Al2S4 induced an accumulation of cells in early mitosis (G2/M phase), followed by the activation of caspase-dependent apoptosis. The compound counteracted different anti-apoptotic Bcl-2 family members (Bcl-xL, phospho-Bad and Bcl-2), promoted activation of Bax and Bak and induced the release of cytochrome c into the cytoplasm. Treatment by Al2S4 let to the identification of early apoptotic events including Bcl-xL degradation, Bak activation and release of cytochrome c followed by late events including Bcl-2 proteolysis, Bax activation, Bad dephosphorylation, caspase activation, nuclear fragmentation and phosphatidylserine exposure.
The p62 protein, also called sequestosome 1 (SQSTM1), is a ubiquitin-binding scaffold protein that colocalizes with ubiquitinated protein aggregates in many neurodegenerative diseases and proteinopathies of the liver. The protein is able to polymerize via an N-terminal PB1 domain and can interact with ubiquitinated proteins via the C-terminal UBA domain. Also, p62/SQSTM1 binds directly to LC3 and GABARAP family proteins via a specific sequence motif. The protein is itself degraded by autophagy and may serve to link ubiquitinated proteins to the autophagic machinery to enable their degradation in the lysosome. Since p62 accumulates when autophagy is inhibited, and decreased levels can be observed when autophagy is induced, p62 may be used as a marker to study autophagic flux. Here, we present several protocols for monitoring autophagy-mediated degradation of p62 using Western blots, pulse-chase measurement of p62 half-life, immunofluorescence and immuno-electron microscopy, as well as live cell imaging with a pH-sensitive mCherry-GFP double tag. We also present data on species-specificity and map the epitopes recognized by several commercially available anti-p62 antibodies.
The class of antimetabolite chemotherapeutical agents has been used to treat cancers in humans for almost 50 years and gives significant results by binding dihydrofolate reductase (DHFR), a key enzyme in DNA synthesis. Therefore, finding new active compounds inhibiting DNA synthesis through their binding to DHFR is of prime interest. The aim of this work is to describe a protocol designed to study the binding of compounds to DHFR. This screening protocol involves matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) detection of target-bound compounds. Firstly, a screening protocol is developed and proves to be a simple, fast, and specific method to characterize the binding capability of a compound. Secondly, the possibility of determining the relative affinities of DHFR-binding compounds by comparing MALDI-TOFMS data is discussed. A ratio is calculated for a compound X such as R(X) = A.I.(denaturation)(X)/A.I.(direct)(X) (where AI(direct) and AI(denaturation) are the average absolute intensities of a binding compound X before and after denaturation of DHFR). It is shown that by using this protocol, one can characterize the strength of the binding of different compounds. These two strategies are then applied to screen green tea (Camellia sinensis) extracts for DHFR-binding compounds, and epigallocatechin gallate is shown to be an active compound with a relative affinity between those of pyrimethamine and methotrexate.
Docetaxel (Taxotere) is prepared from a noncytotoxic precursor extracted from the needles of the Taxus baccata. Preclinical investigations have demonstrated that docetaxel is very active in colon adenocarcinoma murine models. Phase I studies revealed granulocytopenia to be the dose-limiting toxicity. Initial clinical trials also demonstrated docetaxel's activity in ovarian, breast, and non-small cell lung cancer. Because of this encouraging preclinical and clinical activity, we initiated a phase II study of docetaxel in patients with metastatic colorectal carcinoma.
Docetaxel, 100 mg/m2, was administered as a 1-hour intravenous infusion every 21 days. Nineteen patients were entered on the trial. All patients had measurable disease and had not received prior chemotherapy for metastatic disease.
No complete or partial responses were observed. Granulocytopenia was the dose-limiting toxic effect. Seventeen patients had grade 4 granulocytopenia; 8 of these patients received antibiotics for neutropenic fevers. Twelve patients experienced hypersensitivity reactions, and 15 patients experienced cutaneous toxic reactions. One patient demonstrated evidence of fluid retention.
Administered at the stated dose and schedule, docetaxel has little activity against metastatic colorectal carcinomas. The toxicity profile, consisting of granulocytopenia, hypersensitivity reactions, cutaneous reactions, and edema, has been previously described in patients receiving docetaxel.
This chapter presents a detailed discussion of the energetics of interactions between Vinca rosea L. (vinca) alkaloids, antimitotic chemotherapeutic agents, and tubulin, the major protein constituent of microtubules and the mitotic spindle. Vinca alkaloids induce tubulin to form indefinite spirals and ordered paracrystals that compete with microtubule formation. Drug binding is known to be thermodynamically linked to spiral formation. In vivo, vinca alkaloids cause mitotic arrest at substoichiometric concentrations by acting at the ends of microtubules to diminish dynamic instability in mitotic spindles. It obtains a full thermodynamic description of the energetics of vinca alkaloid-induced tubulin self-association over a range of temperature and buffer conditions for a group of vinca alkaloid congeners. The chapter describes the use of sedimentation velocity, the quantitative fitting of weight average sedimentation coefficient data, and its applicability to extracting the energetics of vinca alkaloid-tubulin interactions. Sedimentation velocity has proven to be the best method for determining vinca alkaloid binding affinities and drug-induced tubulin spiralling potential. It compares results obtained with four clinically useful vinca alkaloid congeners. There is a quantitative description of the impact of allosteric effectors such as guanine nucleotides, pH, salt, and divalent cations on the system. The chapter relates these energetic findings to the structure of tubulin, the structure and dynamics of microtubules, and the implications for antimitotic and antineoplastic effectiveness with specific emphasis on tubulin isotype effects.
Multidrug resistance (MDR) mediated by the overexpression of drug efflux protein P-glycoprotein (P-gp) is one of the major obstacles to successful cancer chemotherapy. P-gp acts as an energy-dependent drug efflux pump, reducing the intracellular concentration of structurally unrelated drugs. Modulators of P-gp function can restore the sensitivity of multidrug-resistant cells to such drugs. In the present study, we evaluated the P-gp modulatory potential of diallyl sulfide (DAS), a volatile organosulfur compound present in garlic, known to possess many medicinal properties, including antimutagenic and anticarcinogenic activities. For in vitro studies, K562 leukemic cells were made resistant (K562/R) to the cytotoxicity of vinblastine (VBL) by progressive adaptation of the sensitive K562 parental cells to VBL. Cross-resistance of K562/R was found between vincristine (VCR), doxorubicin and other antineoplastic agents. A non-toxic concentration of DAS (8.75 x 10(-3) M) enhanced the cytotoxic effects of VBL and another vinca alkaloid, VCR, time dependently in VBL-resistant human leukemia (K562/R10) cells but had no effect on the parent (K562/S) cells. The results show that DAS decreased the induced levels of P-gp in resistant cells back to the normal levels as analyzed both qualitatively and quantitatively by western blotting and immunocytochemistry. Furthermore, in vivo combination studies showed that DAS effectively inhibited vinca alkaloid-induced P-gp overexpression in mouse hepatocytes. Quantitation of immunostained tissue sections with image analysis showed that the reduction in P-gp levels was up to 73% for VBL- and 65% for VCR-induced drug resistance. The above features thus indicate that DAS can serve as a novel, non-toxic modulator of MDR and can be used as a dietary adjuvant.
Despite a large amount of drugs available to treat cancer, none is totally satisfactory with respect to its tolerance or side effects. It is very important to discover new compounds that exhibit specific features such as binding to proteic targets. Given the clinical successes of the poisons of the mitotic spindle chemotherapeutic agent class, it is often considered that tubulin represents one of the best cancer targets identified so far, and it seems likely that discovering new drugs of this class will significantly improve the range of active chemotherapeutic agents. The aim of this work is to present the new screening test that has been developed in our laboratory in order to study the binding of compounds to tubulin. We have developed a screening protocol involving three sampling strategies before the MALDI-TOFMS analysis. The three strategies give very accurate and reproducible results and could therefore possibly be used in screening campaigns. We have also proved that no unspecific binding can provide a loss of specificity of the test. Our protocol presents all the requirements for being a useful tool to screen the binding of compounds to tubulin.
Inactivation of constitutive autophagy results in formation of cytoplasmic protein inclusions and leads to liver injury and neurodegeneration, but the details of abnormalities related to impaired autophagy are largely unknown. Here we used mouse genetic analyses to define the roles of autophagy in the aforementioned events. We report that the ubiquitin- and LC3-binding protein "p62" regulates the formation of protein aggregates and is removed by autophagy. Thus, genetic ablation of p62 suppressed the appearance of ubiquitin-positive protein aggregates in hepatocytes and neurons, indicating that p62 plays an important role in inclusion body formation. Moreover, loss of p62 markedly attenuated liver injury caused by autophagy deficiency, whereas it had little effect on neuronal degeneration. Our findings highlight the unexpected role of homeostatic level of p62, which is regulated by autophagy, in controlling intracellular inclusion body formation, and indicate that the pathologic process associated with autophagic deficiency is cell-type specific.
BRAF kinase is a downstream target of KRAS and activates the MAPK pathway. These two molecules are prone to mutations in sporadic microsatellite unstable (MSI) colorectal carcinomas (CRC) and BRAF V600E mutations are inversely associated with oncogenic KRAS mutations. The biological significance of BRAF V600E oncogenic activation is not well established in this type of tumour. We aimed to study proliferation and survival effects induced by BRAF inhibition in MSI CRC cell lines harbouring distinct genetic backgrounds (BRAF V600E or KRAS G13D). Suppression of BRAF in BRAF V600E MSI CRC cell lines by RNA interference significantly inhibited proliferation and induced apoptosis, as demonstrated by BrdU incorporation and TUNEL assay, respectively. No significant differences were seen in proliferation and apoptosis, in cell lines harbouring KRAS G13D, after BRAF inhibition. We further analysed proliferation-associated molecules (pERK1/2, cyclin D1, p27 Kip1) and apoptosis-associated molecules (Bcl-2, Bax, pAkt, pBad, XIAP) in all cell lines. After BRAF down-regulation, we found a more pronounced decrease in ERK1/2 phosphorylation and cyclin D1 expression levels in BRAF-mutated cell lines in comparison to KRAS mutated cells. Upon BRAF inhibition, we also found an increase in p27(Kip1) levels and a more pronounced decrease in the levels of anti-apoptotic protein Bcl-2, specifically in cell lines with BRAF V600E. In conclusion, we have shown that MSI KRAS and BRAF mutant CRC cell lines respond differently to BRAF knockdown. This report provides evidence supporting BRAF as a good target for therapeutic intervention in patients with sporadic MSI CRC harbouring activating mutations in BRAF but not in KRAS.
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