[Show abstract][Hide abstract]ABSTRACT: Although muscle wasting is the obvious manifestation of cancer cachexia that impacts on patient quality of life, the loss of lipid reserves and metabolic imbalance in adipose tissue also contribute to the devastating impact of cachexia. Depletion of fat depots in cancer patients is more pronounced than loss of muscle and often precedes, or even occurs in the absence of, reduced lean body mass. Rapid mobilization of triglycerides stored within adipocytes to supply the body with fatty acids in periods of high-energy demand is normally mediated through a well-defined process of lipolysis involving the lipases ATGL, HSL and MGL. Studies into how these lipases contribute to fat loss in cancer cachexia have revealed the prominent role for ATGL in initiating lipolysis during adipose tissue atrophy, together with links between tumour-derived factors and the signaling pathways that control lipid flux within fat cells. The recent findings of increased thermogenesis in brown fat during cancer cachexia indicates that metabolically active adipose tissue contributes to the imbalance in energy homeostasis involved in catabolic wasting. Such energetically futile use of fatty acids liberated from adipose tissue to generate heat represents a maladaptive response in conjunction with anorexia experienced by cancer patients. As IL-6 release by tumours provokes lipolysis and activates the thermogenic program in brown fat, this review explores the overlap in dysregulated metabolic processes due to inflammatory mediators in cancer cachexia and other disease states characterized by elevated cytokines such as obesity and diabetes.
Full-text · Article · Nov 2015 · Seminars in Cell and Developmental Biology
[Show abstract][Hide abstract]ABSTRACT: Cancer-associated cachexia (CAC) is a wasting syndrome characterized by systemic inflammation, body weight loss, atrophy of white adipose tissue (WAT) and skeletal muscle. Limited therapeutic options are available and the underlying mechanisms are poorly defined. Here we show that a phenotypic switch from WAT to brown fat, a phenomenon termed WAT browning, takes place in the initial stages of CAC, before skeletal muscle atrophy. WAT browning is associated with increased expression of uncoupling protein 1 (UCP1), which uncouples mitochondrial respiration toward thermogenesis instead of ATP synthesis, leading to increased lipid mobilization and energy expenditure in cachectic mice. Chronic inflammation and the cytokine interleukin-6 increase UCP1 expression in WAT, and treatments that reduce inflammation or β-adrenergic blockade reduce WAT browning and ameliorate the severity of cachexia. Importantly, UCP1 staining is observed in WAT from CAC patients. Thus, inhibition of WAT browning represents a promising approach to ameliorate cachexia in cancer patients.
[Show abstract][Hide abstract]ABSTRACT: Involuntary weight loss in patients with cancer is the hallmark of cancer cachexia. The etiology of cachexia is multifactorial involving loss of skeletal muscle and adipose tissue associated with high systemic levels of acute phase proteins and inflammatory cytokines. While muscle wasting overtly impacts on cancer patient quality of life, loss of lipid depots represents a sustained energy imbalance. In this study fat depletion was examined in Colon-26 model of cancer cachexia, which is a widely used rodent model of this syndrome. We investigated diurnal expression of circadian rhythm regulators as well as key mediators of energy metabolism and cytokine signaling. Mice bearing the C26 tumour exhibited reduced adipose mass, elevated adipose tissue lipolysis and a 5-fold increase in plasma levels of free fatty acids. These changes were associated with activated IL-6 signaling in WAT through a 3-fold increase in phosphorylated STAT3 and high SOCS3 gene expression levels. In addition perturbations in circadian regulation of lipid metabolism were also observed. Lipid catabolism did not appear to be influenced by the classical PKA pathway activating the lipase HSL. ATGL protein levels were elevated 2-fold in cachectic mice while 4-fold increase phosphorylated ACC and a 2-fold decrease in phosphorylated 4EBP1 was observed indicating that lipid metabolism is modulated by the ATGL & AMPK/mTOR pathways. This study provides evidence for activation of cytokine signaling and concomitant alterations in circadian rhythm and regulators of lipid metabolism in WAT of cachectic animals.
[Show abstract][Hide abstract]ABSTRACT: Purpose:
In many cancer patients, the malignancy causes reduced hepatic drug clearance leading to potentially serious complications from the use of anticancer drugs. The mechanisms underlying this phenomenon are poorly understood. We aimed to identify tumor-associated inflammatory pathways that alter drug response and enhance chemotherapy-associated toxicity.
We studied inflammatory pathways involved in extra-hepatic tumor mediated repression of CYP3A, a major hepatic drug metabolizing cytochrome P450 subfamily, using a murine Engelbreth-Holm-Swarm sarcoma model. Studies in IL-6 knockout mice determined the source of elevated IL-6 in tumor-bearing animals and monoclonal antibodies against IL-6 were used to intervene in this inflammatory pathway.
Our studies confirm elevated plasma IL-6 levels and reveal activation of Jak/Stat and Mapk signalling pathways and acute phase proteins in livers of tumor-bearing mice. Circulating IL-6 was predominantly produced by the tumor xenograft, rather than being host derived. Anti IL-6 antibody intervention partially reversed tumor-mediated inflammation and Cyp3a gene repression.
IL-6 is an important player in cancer-related repression of CYP3A-mediated drug metabolism and activation of the acute phase response. Targeting IL-6 in cancer patients may prove an effective approach to alleviating cancer-related phenomena, such as adverse drug-related outcomes commonly associated with cancer chemotherapy.
No preview · Article · Apr 2013 · Pharmaceutical Research
[Show abstract][Hide abstract]ABSTRACT: Cachexia has a devastating impact on survival and quality of life for many cancer patients. A better understanding of the underlying mechanisms leading to the complex metabolic defects of cachexia, coupled with effective treatment options, will improve management of wasting in cancer patients. The growing appreciation that cancer cachexia results from the spillover effects of cytokine production by tumors on the integrated regulation of energy balance in different organs identifies potential therapeutic options. However, targeting such tumorkines requires a comprehensive understanding of their normal as well as pathophysiological functions, especially the crosstalk between inflammatory signaling and metabolic dysregulation. Recent advances in characterizing the surprising parallels between obesity and cancer cachexia provide new insights into these apparently divergent syndromes.
Full-text · Article · Nov 2012 · Trends in Endocrinology and Metabolism
[Show abstract][Hide abstract]ABSTRACT: Cancer cachexia/anorexia is a complex syndrome that involves profound metabolic imbalances and is directly implicated as a cause of death in at least 20% to 30% of all cancers. Brown adipose tissue (BAT) plays a key role in thermogenesis and energy balance and potentially contributes to the physiologic perturbations associated with cachexia. In this study, we investigated the impact of cachexia-inducing colorectal tumor on BAT in mice. We found that brown adipocytes were smaller and exhibited profound delipidation in cachectic tumor-bearing mice. Diurnal expression profiling of key regulators of lipid accumulation and fatty acid β-oxidation and their corresponding target genes revealed dramatic molecular changes indicative of active BAT. Increased Ucp1, Pbe, and Cpt1α expression at specific points coincided with higher BAT temperatures during the dark cycle, suggestive of a temporal stimulation of thermogenesis in cachexia. These changes persisted when cachectic mice were acclimatized to 28°C confirming inappropriate stimulation of BAT despite thermoneutrality. Evidence of inflammatory signaling also was observed in the BAT as an energetically wasteful and maladaptive response to anorexia during the development of cachexia.
[Show abstract][Hide abstract]ABSTRACT: This study examined the association between overall survival and Glutathione S-transferase Pi (GST Pi) expression and genetic polymorphism in stage C colon cancer patients after resection alone versus resection plus 5-fluourouracil-based adjuvant chemotherapy.
Patients were drawn from a hospital registry of colorectal cancer resections. Those receiving chemotherapy after it was introduced in 1992 were compared with an age and sex matched control group from the preceding period. GST Pi expression was assessed by immunohistochemistry. Overall survival was analysed by the Kaplan-Meier method and Cox regression.
From an initial 104 patients treated with chemotherapy and 104 matched controls, 26 were excluded because of non-informative immunohistochemistry, leaving 95 in the treated group and 87 controls. Survival did not differ significantly among patients with low GST Pi who did or did not receive chemotherapy and those with high GST Pi who received chemotherapy (lowest pair-wise p = 0.11) whereas patients with high GST Pi who did not receive chemotherapy experienced markedly poorer survival than any of the other three groups (all pair-wise p <0.01). This result was unaffected by GST Pi genotype.
Stage C colon cancer patients with low GST Pi did not benefit from 5-fluourouracil-based adjuvant chemotherapy whereas those with high GST Pi did.
[Show abstract][Hide abstract]ABSTRACT: S100A4, a multifunctional protein, has been linked to the invasive growth and metastases of several human cancers. This study investigated the association between S100A4 and overall survival and other clinicopathological features in patients with stage C colonic cancer.
Clinical and pathological data were obtained from a prospective hospital registry of 409 patients who had a resection for stage C colonic cancer. Tissue microarrays for immunohistochemistry were constructed from archived tissue. S100A4 staining intensity and percentage of stained cells were assessed in nuclei and cytoplasm for both the central part of the tumour and at the advancing front. Overall survival was analysed by the Kaplan-Meier method and Cox regression.
Only a high percentage of cells with S100A4 cytoplasmic staining in frontal tissue was associated with poor survival (hazard ratio, 1.6; 95 % CI 1.1-2.2; p = 0.008) after adjustment for other prognostic variables. There was no association between frontal cytoplasmic S100A4 expression and any of 13 other clinicopathological variables.
High expression of S100A4 in cytoplasm at the advancing front of stage C colonic tumours indicates a poor prognosis. Whether S100A4 can predict response to adjuvant chemotherapy remains to be investigated in a randomised clinical trial.
No preview · Article · May 2012 · International Journal of Colorectal Disease
[Show abstract][Hide abstract]ABSTRACT: Cancer cachexia is a highly debilitating paraneoplastic disease observed in more than 50% of patients with advanced cancers and directly contributes to 20% of cancer deaths. Loss of skeletal muscle is a defining characteristic of patients with cancer cachexia and is associated with poor survival. The present study reveals the involvement of a myogenic transcription factor Myocyte Enhancer Factor (MEF) 2C in cancer-induced skeletal muscle wasting. Increased skeletal muscle mRNA expression of Suppressor of Cytokine Signaling (Socs) 3 and the IL-6 receptor indicative of active IL-6 signaling was seen in skeletal muscle of mice bearing the Colon 26 (C26) carcinoma. Loss of skeletal muscle structural integrity and distorted mitochondria were also observed using electron microscopy. Gene and protein expression of MEF2C was significantly downregulated in skeletal muscle from C26-bearing mice. MEF2C gene targets myozenin and myoglobin as well as myokinase were also altered during cachexia, suggesting dysregulated oxygen transport capacity and ATP regeneration in addition to distorted structural integrity. In addition, reduced expression of calcineurin was observed which suggested a potential pathway of MEF2C dysregulation. Together, these effects may limit sarcomeric contractile ability and also predispose skeletal muscle to structural instability; associated with muscle wasting and fatigue in cachexia.
[Show abstract][Hide abstract]ABSTRACT: Src tyrosine kinase has long been implicated in colon cancer but much remains to be learned about its substrates. The nuclear receptor hepatocyte nuclear factor 4α (HNF4α) has just recently been implicated in colon cancer but its role is poorly defined. Here we show that c-Src phosphorylates human HNF4α on three tyrosines in an interdependent and isoform-specific fashion. The initial phosphorylation site is a Tyr residue (Y14) present in the N-terminal A/B domain of P1- but not P2-driven HNF4α. Phospho-Y14 interacts with the Src SH2 domain, leading to the phosphorylation of two additional tyrosines in the ligand binding domain (LBD) in P1-HNF4α. Phosphomimetic mutants in the LBD decrease P1-HNF4α protein stability, nuclear localization and transactivation function. Immunohistochemical analysis of approximately 450 human colon cancer specimens (Stage III) reveals that P1-HNF4α is either lost or localized in the cytoplasm in approximately 80% of tumors, and that staining for active Src correlates with those events in a subset of samples. Finally, three SNPs in the human HNF4α protein, two of which are in the HNF4α F domain that interacts with the Src SH3 domain, increase phosphorylation by Src and decrease HNF4α protein stability and function, suggesting that individuals with those variants may be more susceptible to Src-mediated effects. This newly identified interaction between Src kinase and HNF4α has important implications for colon and other cancers.
Full-text · Article · Feb 2012 · Proceedings of the National Academy of Sciences
[Show abstract][Hide abstract]ABSTRACT: This study investigated the association between glutathione S-transferase Pi (GST Pi) expression, histopathology and overall survival in 468 patients after resection of stage C colonic adenocarcinoma.
Data were drawn from a prospective hospital registry of consecutive bowel cancer resections with a minimum follow-up of 5 years. Nuclear and cytoplasmic GST Pi expression, assessed by both intensity of staining and percentage of stained cells at both the central part of the tumour and the invasive tumour front, were evaluated retrospectively by tissue microarray immunohistochemistry on archival specimens. The most effective measure of GST Pi expression was the percentage of immunostained nuclei in central tumour tissue, where >40% stained was associated significantly with high grade, invasion beyond the muscularis propria, involvement of a free serosal surface or apical node, and invasion into an adjacent organ or structure. After adjustment of other predictors, GST Pi expression remained independently prognostic for reduced overall survival (hazard ratio 1.4, P = 0.002).
In patients with clinicopathological stage C colonic cancer, GST Pi expression is associated with features of tumour aggressiveness and with reduced overall survival. Further appropriately designed studies should aim to discover whether GST Pi can predict response to adjuvant chemotherapy.
[Show abstract][Hide abstract]ABSTRACT: The inherent cytotoxic nature of many anti-cancer drugs is a major challenge in oncology as excessive toxicity due to variable drug clearance is a common cause of treatment failure. The inability to predict individual cancer patient’s metabolism and transport of drugs can lead to delay, termination or even death due to adverse toxicities in normal tissues. Systemic inflammation associated with tumours is represses hepatic drug clearance - in particular CYP3A4 responsible for metabolism of the majority of anti-cancer drugs. Elevated inflammatory markers coupled with tumour-derived cytokines such as IL-6 are also significant features of the metabolic imbalance underlying tissue wasting in cachectic cancer patients. We hypothesized that disrupted drug clearance and aberrant regulation of metabolic pathways may be part of the same process and in combination impact on treatment outcome and quality of life for many cancer sufferers. We have made use of mouse tumour models of cachexia to characterize the alterations in drug metabolizing enzymes & transporters as well as to explore the interplay of cytokine signaling cascades with nuclear receptors and other key regulators of drug clearance and general metabolic pathways. Transcriptional repression of a human CYP3A4 transgene in tumour-bearing mice was accompanied by increased IL-6 and increased hepatic expression of many acute phase proteins. Extensive gene expression analysis using microarrays and MS-based proteomic profiling showed that all 3 phases of hepatic drug metabolism and transport are altered in tumour-bearing mice. The underlying mechanism involves disrupted action of RXRa, the heterodimeric partner of PXR and CAR that regulate drug clearance. In addition to repression of murine Cyp3a genes we found that Cyp1a2 was markedly reduced in livers of tumour-bearing mice leading to increased zoxazolamine sleep time. As CYP1A enzymes also contribute to caffeine metabolism we carried out pharmacokinetic studies in tumour-bearing mice as a prelude to clinical trials to test the value of caffeine as a predictive marker of repressed drug clearance pathways in cancer patients. The expression of drug transporters such as Bcrp and mrp2 are altered in kidney as well as liver indicating that biodistribution of drugs in several organs may be affected in the presence of cancer. CONCLUSION. Systemic inflammation associated with tumour-derived cytokines is an important factor in clearance of anticancer drugs. The ability to predict patients at risk of excessive toxicity and normalizing drug clearance pathways by targeting specific cytokines may lead to safer and more effective use of chemotherapy.
[Show abstract][Hide abstract]ABSTRACT: Quantitative mass spectrometry using iTRAQ was used to identify differentially expressed proteins from 16 colorectal cancer (CRC) tumours compared to patient-paired adjacent normal mucosa. Over 1400 proteins were identified and quantitated, with 118 determined as differentially expressed by >1.3-fold, with false discovery rate < 0.05. Gene Ontology analysis indicated that proteins with increased expression levels in CRC tumours include those associated with glycolysis, calcium binding, and protease inhibition. Proteins with reduced levels in CRC tumours were associated with loss of ATP production through: (i) reduced β-oxidation of fatty acids, (ii) reduced NADH production by the tricarboxylic acid cycle and (iii) decreased oxidative phosphorylation activity. Additionally, biosyntheses of glycosaminoglycans and proteoglycans were significantly reduced in tumour samples. Validation experiments using immunoblotting and immunohistochemistry (IHC) showed strong concordance with iTRAQ data suggesting that this workflow is suitable for identifying biomarker candidates. We discuss the uses and challenges of this approach to generate biomarker leads for patient prognostication.
No preview · Article · Aug 2011 · Molecular BioSystems
[Show abstract][Hide abstract]ABSTRACT: To determine the mechanisms by which tumors situated in extrahepatic sites can cause profound changes in hepatic drug clearance, contributing to altered drug response and chemotherapy resistance.
We studied in wild-type or transgenic CYP3A4 reporter mice implanted with the murine Engelbreth-Holm-Swarm sarcoma changes in nuclear receptor and hepatic transcription factor expression and/or function, particularly related to CYP3A gene regulation.
Repression of hepatic CYP3A induction was dramatic and associated with reduced levels of C/EBPβ isoforms, impaired pregnane X receptor, and constitutive androstane receptor function. Unexpectedly, extrahepatic tumors strongly reduced nuclear accumulation of retinoid X receptor alpha (RXRα) in hepatocytes, providing a potential explanation for impaired function of nuclear receptors that rely on RXRα dimerization. Profiling revealed 38 nuclear receptors were expressed in liver with 14 showing between 1.5- and four-fold reduction in expression in livers of tumor-bearing animals, including Car, Trβ, Lxrβ, Pparα, Errα/β, Reverbα/β, and Shp. Altered Pparα and γ induction of target genes provided additional evidence of perturbed hepatic metabolic control elicited by extrahepatic tumors.
Extrahepatic malignancy can affect hepatic drug metabolism by nuclear receptor relocalization and decreased receptor expression and function. These findings could aid the design of intervention strategies to normalize drug clearance and metabolic pathways in cancer patients at risk of chemotherapy-induced toxicity or cancer cachexia.
Full-text · Article · May 2011 · Clinical Cancer Research
[Show abstract][Hide abstract]ABSTRACT: Molecular expression patterns have often been used for patient classification in oncology in an effort to improve prognostic prediction and treatment compatibility. This effort is, however, hampered by the highly heterogeneous data often seen in the molecular analysis of cancer. The lack of overall similarity between expression profiles makes it difficult to partition data using conventional data mining tools. In this chapter, the authors introduce a bioinformatics protocol that uses REACTOME pathways and patient-protein network structure (also called topology) as the basis for patient classification.
Full-text · Article · Jan 2011 · Methods in molecular biology (Clifton, N.J.)
[Show abstract][Hide abstract]ABSTRACT: The orphan nuclear receptor pregnane X receptor regulates enzymes and transport proteins involved in the detoxification and clearance of numerous endobiotic and xenobiotic compounds, including pharmaceutical agents. Multiple alternatively spliced pregnane X receptor isoforms have been identified which are significantly expressed in humans and mice (up to 30% of the total pregnane X receptor transcript), however, little is known about their biological action. We explored functional differences between the major mouse pregnane X receptor isoforms mPXR(431) and mPXR(Delta171-211) that lacks 41 amino acids adjacent to the ligand-binding pocket. Transient transfection assays showed that mPXR(Delta171-211) reduced the basal transcription of cytochrome P450 3A4 and the drug transporter P-glycoprotein/Multi Drug Resistance Protein 1 and directly repressed the regulatory effects of mPXR(431) on these genes. Replacement of the mPXR(Delta171-211) DNA-binding domain with that of GAL4 showed mPXR(Delta171-211) retained its repressive role independent of binding to PXR responsive elements located within the cytochrome P450 3A4 and Multi Drug Resistance Protein 1 regulatory regions. Use of the histone deacetylase inhibitor, trichostatin A, demonstrated that the repressive function of mPXR(Delta171-211) acts independently of histone acetylation state. Protein interaction assays revealed mPXR(Delta171-211) and mPXR(431) differentially bind the obligatory heterodimer partner retinoid X receptor. Furthermore, mPXR(431) and mPXR(Delta171-211) proteins could heterodimerize. These studies demonstrate that the variant mouse PXR isoform, mPXR(Delta171-211), has a distinct repressive function from mPXR(431) in regulating genes encoding important drug metabolizing enzymes and transport proteins.
No preview · Article · May 2010 · The international journal of biochemistry & cell biology