Glutaminolysis and glycolysis regulation by troglitazone in breast cancer cells: Relationship to mitochondrial membrane potential

The troglitazone derivative EP13 disrupts energy metabolism through respiratory chain complex I inhibition in breast cancer cells and potentiates the antiproliferative effect of glycolysis inhibitors

BACKGROUND

The metabolism of cancer cells generally differs from that of normal cells. Indeed, most cancer cells have a high rate of glycolysis, even at normal oxygen concentrations. These metabolic properties can potentially be exploited for therapeutic intervention. In this context, we have developed troglitazone derivatives to treat hormone-sensitive and triple-negative breast cancers, which currently lack therapeutic targets, have an aggressive phenotype, and often have a worse prognosis than other subtypes. Here, we studied the metabolic impact of the EP13 compound, a desulfured derivative of Δ2-troglitazone that we synthetized and is more potent than its parent compounds.

METHODS

EP13 was tested on two triple-negative breast cancer cell lines, MDA-MB-231 and Hs578T, and on the luminal cell line MCF-7. The oxygen consumption rate (OCR) of the treated cell lines, Hs578T mammospheres and isolated mitochondria was measured using the XFe24 Seahorse analyser. ROS production was quantified using the MitoSOX fluorescent probe. Glycolytic activity was evaluated through measurement of the extracellular acidification rate (ECAR), glucose consumption and lactate production in extracellular medium. The synergistic effect of EP13 with glycolysis inhibitors (oxamate and 2-deoxyglucose) on cell cytotoxicity was established using the Chou-Talalay method.

RESULTS

After exposure to EP13, we observed a decrease in the mitochondrial oxygen consumption rate in MCF7, MDA-MB-231 and Hs578T cells. EP13 also modified the maximal OCR of Hs578T spheroids. EP13 reduced the OCR through inhibition of respiratory chain complex I. After 24 h, ATP levels in EP13-treated cells were not altered compared with those in untreated cells, suggesting compensation by glycolysis activity, as shown by the increase in ECAR, the glucose consumption and lactate production. Finally, we performed co-treatments with EP13 and glycolysis inhibitors (oxamate and 2-DG) and observed that EP13 potentiated their cytotoxic effects.

CONCLUSION

This study demonstrates that EP13 inhibits OXPHOS in breast cancer cells and potentiates the effect of glycolysis inhibitors.

Association of AST/ALT ratio with 90-day outcomes in patients with acute exacerbation of chronic liver disease: a prospective multicenter cohort study in China

Background and aim

A high aspartate aminotransferase/alanine aminotransferase (AST/ALT) ratio is associated with liver injury in liver disease; however, no data exist regarding its relationship with 90-day prognosis in patients with acute exacerbation of chronic liver disease.

Methods

In this study, 3,758 participants (955 with advanced fibrosis and 2,803 with cirrhosis) from the CATCH-LIFE cohort in China were included. The relationships between different AST/ALT ratios and the risk of adverse 90-day outcomes (death or liver transplantation) were determined in patients with cirrhosis or hepatitis B virus (HBV)-associated advanced fibrosis, respectively.

Results

In the patients with HBV-associated advanced fibrosis, the risk of 90-day adverse outcomes increased with AST/ALT ratio; after adjusting for all confounding factors, the risk of adverse 90-day outcomes was the highest when AST/ALT ratio was more than 1.08 (OR = 6.91 [95% CI = 1.789-26.721], p = 0.005), and the AST/ALT ratio of >1.9 accelerated the development of adverse outcomes. In patients with cirrhosis, an AST/ALT ratio > 1.38 increased the risk of adverse 90-day outcomes in all univariables (OR = 1.551 [95% CI = 1.216-1.983], p < 0.001) and multivariable-adjusted analyses (OR = 1.847 [95% CI = 1.361-2.514], p < 0.001), and an elevated AST/ALT ratio (<2.65) accelerated the incidence of 90-day adverse outcomes. An AST/ALT ratio of >1.38 corresponded with a more than 20% incidence of adverse outcomes in patients with cirrhosis.

Conclusion

The AST/ALT ratio is an independent risk factor for adverse 90-day outcomes in patients with cirrhosis and HBV-associated advanced fibrosis. The cutoff values of the AST/ALT ratio could help clinicians monitor the condition of patients when making clinical decisions.

Targeting glutaminase is therapeutically effective in ibrutinib-resistant mantle cell lymphoma

Mantle cell lymphoma (MCL) is an incurable B-cell non-Hodgkin lymphoma characterized by frequent relapses. The development of resistance to ibrutinib therapy remains a major challenge in MCL. We previously showed that glutaminolysis is associated with resistance to ibrutinib. In this study, we confirmed that glutaminase (GLS), the first enzyme in glutaminolysis, is overexpressed in ibrutinib-resistant MCL cells, and that its expression correlates well with elevated glutamine dependency and glutaminolysis. Furthermore, we discovered that GLS expression correlates with MYC expression and the functioning of the glutamine transporter ASCT2. Depletion of glutamine or GLS significantly reduced cell growth, while GLS overexpression enhanced glutamine dependency and ibrutinib resistance. Consistent with this, GLS inhibition by its specific inhibitor telaglenastat suppressed MCL cell growth both in vitro and in vivo. Moreover, telaglenastat showed anti-MCL synergy when combined with ibrutinib or venetoclax in vitro, which was confirmed using an MCL patient-derived xenograft model. Our study provides the first evidence that targeting GLS with telaglenastat, alone or in combination with ibrutinib or venetoclax, is a promising strategy to overcome ibrutinib resistance in MCL.

SIRT5 stabilizes mitochondrial glutaminase and supports breast cancer tumorigenesis

The mitochondrial enzyme glutaminase (GLS) is frequently up-regulated during tumorigenesis and is being evaluated as a target for cancer therapy. GLS catalyzes the hydrolysis of glutamine to glutamate, which then supplies diverse metabolic pathways with carbon and/or nitrogen. Here, we report that SIRT5, a mitochondrial NAD⁺-dependent lysine deacylase, plays a key role in stabilizing GLS. In transformed cells, SIRT5 regulates glutamine metabolism by desuccinylating GLS and thereby protecting it from ubiquitin-mediated degradation. Moreover, we show that SIRT5 is up-regulated during cellular transformation and supports proliferation and tumorigenesis. Elevated SIRT5 expression in human breast tumors correlates with poor patient prognosis. These findings reveal a mechanism for increasing GLS expression in cancer cells and establish a role for SIRT5 in metabolic reprogramming and mammary tumorigenesis.

Prognostic value of aspartate transaminase to alanine transaminase (De Ritis) ratio in solid tumors: a pooled analysis of 9,400 patients

BACKGROUND

Numerous studies have reported the association between pretreatment serum aspartate transaminase to alanine transaminase (AST/ALT) ratio and prognosis in multiple cancers. However, the results remain controversial and no consensus has been reached. Thus, we conducted this meta-analysis to quantitatively assess the prognostic value of pretreatment AST/ALT ratio in solid tumors.

METHODS

A systematic literature search was conducted by using PubMed, EMBASE, Web of Science, Cochrane Library, and Wanfang databases, as well as several trial registry platforms, including ClinicalTrials.gov, WHO International Clinical Trials Registry Platform, and Chinese Clinical Trial Registry, up to April 5, 2019. HR and 95% CI for overall survival (OS), cancer-specific survival (CSS), and recurrence-free survival (RFS) were calculated to estimate the effect size.

RESULTS

A total of 18 studies with 9,400 patients were included. Overall, a high level of pretreatment AST/ALT ratio was significantly associated with worse OS (pooled HR=1.70, 95% CI=1.38-2.09). The statistical significance was observed in all cancer types, including renal cell carcinoma (pooled HR=1.64, 95% CI=1.30-2.05), liver cancer (pooled HR=1.16, 95% CI=1.04-1.29), urinary tract urothelial carcinoma (pooled HR=1.96, 95% CI=1.53-2.51), bladder cancer (pooled HR =2.66, 95% CI=1.69-4.20), and other cancers (pooled HR=1.44, 95% CI=1.18-1.76). Moreover, an increased level of serum AST/ALT ratio predicted unfavorable CSS (pooled HR=2.07, 95% CI=1.74-2.46) and RFS (pooled HR=1.51, 95% CI=1.15-1.99).

CONCLUSION

Elevated level of serum AST/ALT ratio before treatment is significantly associated with poor clinical outcomes of OS, CSS, and RFS in patients with solid tumors. Pretreatment AST/ALT ratio can serve as a useful prognostic predictor for malignant patients.

Advances in metabolomics of thyroid cancer diagnosis and metabolic regulation

Thyroid cancers (TCs) are the most frequent endocrine malignancy with an unpredictable fast-growing incidence, especially in females all over the world. Fine-needle aspiration biopsy (FNAB) analysis is an accurate diagnostic method for detecting thyroid nodules and classification of TC. Though simplicity, safety, and accuracy of FNAB, 15-30% of cases are indeterminate, and it is not possible to determine the exact cytology of the specimen. This demands the need for innovative methods capable to find crucial biomarkers with adequate sensitivity for diagnosis and prediction in TC researches. Cancer-based metabolomics is a vast emerging field focused on the detection of a large set of metabolites extracted from biofluids or tissues. Using analytical chemistry procedures allows for the potential recognition of cancer-based metabolites for the purposes of advancing the era of personalized medicine. Nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS) coupled with separation techniques e.g., gas chromatography (GC) and liquid chromatography (LC) are the main approaches for metabolic studies in cancers. The immense metabolite profiling has provided a chance to discover novel biomarkers for early detection of thyroid cancer and reduce unnecessary aggressive surgery. In this review, we recapitulate the recent advances and developed methods of diverse metabolomics tools and metabolic phenotypes of thyroid cancer, following a brief discussion of recent challenges in the thyroid cancer diagnosis.

Using Machine Learning to Measure Relatedness Between Genes: A Multi-Features Model

Measuring conditional relatedness between a pair of genes is a fundamental technique and still a significant challenge in computational biology. Such relatedness can be assessed by gene expression similarities while suffering high false discovery rates. Meanwhile, other types of features, e.g., prior-knowledge based similarities, is only viable for measuring global relatedness. In this paper, we propose a novel machine learning model, named Multi-Features Relatedness (MFR), for accurately measuring conditional relatedness between a pair of genes by incorporating expression similarities with prior-knowledge based similarities in an assessment criterion. MFR is used to predict gene-gene interactions extracted from the COXPRESdb, KEGG, HPRD, and TRRUST databases by the 10-fold cross validation and test verification, and to identify gene-gene interactions collected from the GeneFriends and DIP databases for further verification. The results show that MFR achieves the highest area under curve (AUC) values for identifying gene-gene interactions in the development, test, and DIP datasets. Specifically, it obtains an improvement of 1.1% on average of precision for detecting gene pairs with both high expression similarities and high prior-knowledge based similarities in all datasets, comparing to other linear models and coexpression analysis methods. Regarding cancer gene networks construction and gene function prediction, MFR also obtains the results with more biological significances and higher average prediction accuracy, than other compared models and methods. A website of the MFR model and relevant datasets can be accessed from http://bmbl.sdstate.edu/MFR.

Novel role of miR-133a-3p in repressing gastric cancer growth and metastasis via blocking autophagy-mediated glutaminolysis

BACKGROUND

Autophagy plays a crucial role in sustaining the homeostasis in various malignant diseases. It has also been reported to promote tumor development in multiple cancers. Glutaminolysis instead of Warburg Effect produce adequate ATP and provide nitrogen and carbon to replenish the TCA cycle which has been discovered to be a new energy source for tumor cells recently. By means of degrading intracellular particles including amino acids, nucleotides, fatty acids, sugars and aged organisms, autophagy can recycle the aforementioned particles into bioenergetics and biosynthesis pathways, finally favoring tumor cells. MicroRNA is a kind of noncoding RNA that regulates the targeting gene expression mostly at post-transcription level. Among these miRNAs, microRNA-133a-3p is reported to be a tumor suppressor in numerous cancers.

METHODS

We characterized the down-regulated expression level of microRNA-133a-3p in gastric cancer via TCGA database. Subsequently, we verified the tumor suppressor role of microRNA-133a-3p in gastric cancer cells through a series biological function assay. We used immunofluorescence and transmission electron microscope to observe the negative effect of microRNA-133a-3p on autophagy and used dual-luciferase report assay to identify the candidate gene GABARAPL1 of microRNA-133A-3p.Then we used high performance liquid phase mass spectrometry and seahorse analysis to detect whether miR-133a-3p could block the glutaminolysis metabolism through autophagy. At last, we confirmed the tumor suppressor role of microRNA-133a-3p in vivo on PDX mice model.

RESULTS

We demonstrated that microRNA-133a-3p overexpression could block the activation of autophagy to ruin the abnormal glutaminolysis and further inhibit the growth and metastasis of gastric cancer cells. We successfully proved gastric cancer cells can replenish glutaminolysis via autophagy and microRNA-133a-3p could block aforementioned pathway by targeting core autophagy participants GABARAPL1 and ATG13.We then verified the negative function of microRNA-133a-3p on autophagy-mediated glutaminolysis both in PDX model and human gastric cancer organoid model.

CONCLUSIONS

MicroRNA-133a-3p targets GABARAPL1 to block autophagy-mediated glutaminolysis, further repressing gastric cancer growth and metastasis.

Blood and Tissue Enzymatic Activities of GDH and LDH, Index of Glutathione, and Oxidative Stress among Breast Cancer Patients Attending Referral Hospitals of Addis Ababa, Ethiopia: Hospital-Based Comparative Cross-Sectional Study

The exact cause of breast cancer is unknown; it is a multifactorial disease. It is the most diagnosed and the second killer cancer among women. Breast cancer can be originated from tissues of breast or secondary from other organs via metastasis. Generally, cancer cells show aberrant metabolism and oxidative stress when compared to noncancerous tissues of breast cancer patients. The current study aims at evaluating glutamate and glucose metabolism through GDH and LDH enzyme activities, oxidant, and antioxidative status among breast cancer patients attending referral hospitals of Addis Ababa, Ethiopia. Result. Catalytic activities of glutamate dehydrogenase, lactate dehydrogenase, and oxidative stress index were significantly increased in both serum (4.2 mU/ml, 78.6 mU/ml, and 3.3 : 1, resp.) and cancerous tissues (1.4 mU/ml, 111.7 mU/ml, and 2.15 : 1, resp.) of breast cancer patients as compared to those in serum of control group (3.15 mU/ml, 30.4 mU/ml, and 2.05 : 1, resp.) and noncancerous tissues of breast cancer patients (0.92 mU/ml, 70.5 mU/ml, and 1.1 : 1, resp.) (P ≤ 0.05). Correspondingly, ratios of reduced to oxidized glutathione were significantly decreased in both serum (20 : 1) and cancerous tissues (23.5 : 1) of breast cancer patients when compared to those in serum of control group (104.5 : 1) and noncancerous tissues of breast cancer patients (70.9 : 1) (P ≤ 0.05). Conclusion. Catalytic activities of GDH and LDH, ratios of GSH to GSSG, and concentration of TOS among breast cancer patients were significantly higher than were those among control group and noncancerous tissues of breast cancer patients, while TAC of breast cancer patients is significantly lower than that of control group and normal tissues of breast cancer patients.

Mapping metabolic changes by noninvasive, multiparametric, high-resolution imaging using endogenous contrast

Monitoring subcellular functional and structural changes associated with metabolism is essential for understanding healthy tissue development and the progression of numerous diseases, including cancer, diabetes, and cardiovascular and neurodegenerative disorders. Unfortunately, established methods for this purpose either are destructive or require the use of exogenous agents. Recent work has highlighted the potential of endogenous two-photon excited fluorescence (TPEF) as a method to monitor subtle metabolic changes; however, mechanistic understanding of the connections between the detected optical signal and the underlying metabolic pathways has been lacking. We present a quantitative approach to detecting both functional and structural metabolic biomarkers noninvasively, relying on endogenous TPEF from two coenzymes, NADH (reduced form of nicotinamide adenine dinucleotide) and FAD (flavin adenine dinucleotide). We perform multiparametric analysis of three optical biomarkers within intact, living cells and three-dimensional tissues: cellular redox state, NADH fluorescence lifetime, and mitochondrial clustering. We monitor the biomarkers in cells and tissues subjected to metabolic perturbations that trigger changes in distinct metabolic processes, including glycolysis and glutaminolysis, extrinsic and intrinsic mitochondrial uncoupling, and fatty acid oxidation and synthesis. We demonstrate that these optical biomarkers provide complementary insights into the underlying biological mechanisms. Thus, when used in combination, these biomarkers can serve as a valuable tool for sensitive, label-free identification of changes in specific metabolic pathways and characterization of the heterogeneity of the elicited responses with single-cell resolution.

Expression of glutamine metabolism-related proteins in thyroid cancer

PURPOSE

This study aimed to investigate the expression of glutamine metabolism-related protein in tumor and stromal compartments among the histologic subtypes of thyroid cancer.

RESULTS

GLS1 and GDH expression in tumor and stromal compartments were the highest in AC than in other subtypes. Tumoral ASCT2 expression was higher in MC but lower in FC (p < 0.001). In PTC, tumoral GLS1 and tumoral GDH expression was higher in the conventional type than in the follicular variant (p = 0.043 and 0.001, respectively), and in PTC with BRAF V600E mutation than in PTC without BRAF V600E mutation (p<0.001). Stromal GDH positivity was the independent factor associated with short overall survival (hazard ratio: 21.48, 95% confidence interval: 2.178-211.8, p = 0.009).

METHODS

We performed tissue microarrays with 557 thyroid cancer cases (papillary thyroid carcinoma [PTC]: 344, follicular carcinoma [FC]: 112, medullary carcinoma [MC]: 70, poorly differentiated carcinoma [PDC]: 23, and anaplastic carcinoma [AC]: 8) and 152 follicular adenoma (FA) cases. We performed immunohistochemical staining of glutaminolysis-related proteins (glutaminase 1 [GLS1], glutamate dehydrogenase [GDH], and amino acid transporter-2 [ASCT-2]).

CONCLUSION

Glutamine metabolism-related protein expression differed among the histologic subtypes of thyroid cancer.

Protective effect of salusin-α and salusin-β against ethanol-induced gastric ulcer in rats

BACKGROUND

Alcohol consumption has been found to be associated with gastric ulcers, including gastric mucosal lesions. Salusin-α and salusin-β are bioactive peptides having 28 and 20 amino acids, respectively. Salusin-α and salusin-β immunoreactivity has been detected in the stomach and in the intestines. It has been reported that the salusins regulate the cytokine levels and decrease the infarct area in the heart tissue after ischemia. In this study, we investigated the effects of the salusins in the gastric injury formed with ethanol.

METHODS

Thirty-two sprague Dawley male rats were randomly divided into four groups, including eight rats in each group as follows: Group 1: control; Group 2: ethanol 5 mL/kg; Group 3: ethanol 5 mL/kg+5 nmol/kg salusin-α; Group 4: ethanol 5 mL/kg+5 nmol/kg salusin-β.

RESULTS

The salusin-α level increased at a significant level in the ulcer group formed with ethanol (p<0.001); the change in the salusin-β level is not significant. As for malondialdehyde (p<0.05) and myeloperoxidase (p<0.001), when compared with the control group, tumor necrosis factor-α (p<0.05) levels increased in the group to which ethanol was applied and decreased significantly with the application of salusins. Levels of GSH and IL-1β did not change at a significant level. In addition, histopathologic analysis demonstrated that, in salusin-administered groups, mucosal injury and caspase-3 expressions were reduced.

CONCLUSIONS

The suppression of salusin-α and salusin-β on caspase-3 expression by means of their effects on oxidative injury and TNF-α levels shows that these two hormones could serve as anti-ulcerative agents.

The Glutamate Dehydrogenase Pathway and Its Roles in Cell and Tissue Biology in Health and Disease

Glutamate dehydrogenase (GDH) is a hexameric enzyme that catalyzes the reversible conversion of glutamate to α-ketoglutarate and ammonia while reducing NAD(P)⁺ to NAD(P)H. It is found in all living organisms serving both catabolic and anabolic reactions. In mammalian tissues, oxidative deamination of glutamate via GDH generates α-ketoglutarate, which is metabolized by the Krebs cycle, leading to the synthesis of ATP. In addition, the GDH pathway is linked to diverse cellular processes, including ammonia metabolism, acid-base equilibrium, redox homeostasis (via formation of fumarate), lipid biosynthesis (via oxidative generation of citrate), and lactate production. While most mammals possess a single GDH1 protein (hGDH1 in the human) that is highly expressed in the liver, humans and other primates have acquired, via duplication, an hGDH2 isoenzyme with distinct functional properties and tissue expression profile. The novel hGDH2 underwent rapid evolutionary adaptation, acquiring unique properties that enable enhanced enzyme function under conditions inhibitory to its ancestor hGDH1. These are thought to provide a biological advantage to humans with hGDH2 evolution occurring concomitantly with human brain development. hGDH2 is co-expressed with hGDH1 in human brain, kidney, testis and steroidogenic organs, but not in the liver. In human cerebral cortex, hGDH1 and hGDH2 are expressed in astrocytes, the cells responsible for removing and metabolizing transmitter glutamate, and for supplying neurons with glutamine and lactate. In human testis, hGDH2 (but not hGDH1) is densely expressed in the Sertoli cells, known to provide the spermatids with lactate and other nutrients. In steroid producing cells, hGDH1/2 is thought to generate reducing equivalents (NADPH) in the mitochondria for the biosynthesis of steroidal hormones. Lastly, up-regulation of hGDH1/2 expression occurs in cancer, permitting neoplastic cells to utilize glutamine/glutamate for their growth. In addition, deregulation of hGDH1/2 is implicated in the pathogenesis of several human disorders.

Glutaminolysis as a target for cancer therapy

Cancer cells display an altered metabolic circuitry that is directly regulated by oncogenic mutations and loss of tumor suppressors. Mounting evidence indicates that altered glutamine metabolism in cancer cells has critical roles in supporting macromolecule biosynthesis, regulating signaling pathways, and maintaining redox homeostasis, all of which contribute to cancer cell proliferation and survival. Thus, intervention in these metabolic processes could provide novel approaches to improve cancer treatment. This review summarizes current findings on the role of glutaminolytic enzymes in human cancers and provides an update on the development of small molecule inhibitors to target glutaminolysis for cancer therapy.

Grainyhead-like 2 Reverses the Metabolic Changes Induced by the Oncogenic Epithelial-Mesenchymal Transition: Effects on Anoikis

Resistance to anoikis is a prerequisite for tumor metastasis. The epithelial-to-mesenchymal transition (EMT) allows tumor cells to evade anoikis. The wound-healing regulatory transcription factor Grainyhead-like 2 (GRHL2) suppresses/reverses EMT, accompanied by suppression of the cancer stem cell (CSC) phenotype and by resensitization to anoikis. Here, the effects of GRHL2 upon intracellular metabolism in the context of reversion of the EMT/CSC phenotype, with a view toward understanding how these effects promote anoikis sensitivity, were investigated. EMT enhanced mitochondrial oxidative metabolism. Although this was accompanied by higher accumulation of superoxide, the overall level of reactive oxygen species (ROS) declined, due to decreased hydrogen peroxide. Glutamate dehydrogenase 1 (GLUD1) expression increased in EMT, and this increase, via the product α-ketoglutarate (α-KG), was important for suppressing hydrogen peroxide and protecting against anoikis. GRHL2 suppressed GLUD1 gene expression, decreased α-KG, increased ROS, and sensitized cells to anoikis.

IMPLICATIONS

These results demonstrate a mechanistic role for GRHL2 in promoting anoikis through metabolic alterations. Mol Cancer Res; 14(6); 528-38. ©2016 AACR.

Troglitazone suppresses glutamine metabolism through a PPAR-independent mechanism

Enhanced glutamine metabolism is required for tumor cell growth and survival, which suggests that agents targeting glutaminolysis may have utility within anti-cancer therapies. Troglitazone, a PPARγ agonist, exhibits significant anti-tumor activity and can alter glutamine metabolism in multiple cell types. Therefore, we examined whether troglitazone would disrupt glutamine metabolism in tumor cells and whether its action was reliant on PPARγ activity. We found that troglitazone treatment suppressed glutamine uptake and the expression of the glutamine transporter, ASCT2, and glutaminase. In addition, troglitazone reduced 13C-glutamine incorporation into the TCA cycle, decreased [ATP], and resulted in an increase in reactive oxygen species (ROS). Further, troglitazone treatment decreased tumor cell growth, which was partially rescued with the addition of the TCA-intermediate, α-ketoglutarate, or the antioxidant N-acetylcysteine. Importantly, troglitazone's effects on glutamine uptake or viable cell number were found to be PPARγ-independent. In contrast, troglitazone caused a decrease in c-Myc levels, while the proteasomal inhibitor, MG132, rescued c-Myc, ASCT2 and GLS1 expression, as well as glutamine uptake and cell number. Lastly, combinatorial treatment of troglitazone and metformin resulted in a synergistic decrease in cell number. Therefore, characterizing new anti-tumor properties of previously approved FDA therapies supports the potential for repurposing of these agents.

Energy metabolic dysfunction as a carcinogenic factor in cancer cells

Cancer, as a leading cause of death, has attracted enormous public attention. Reprogramming of cellular energy metabolism is deemed to be one of the principal hallmarks of cancer. In this article, we reviewed the mutual relationships among environmental pollution factors, energy metabolic dysfunction, and various cancers. We found that most environmental pollution factors could induce cancers mainly by disturbing the energy metabolism. By triggering microenvironment alteration, energy metabolic dysfunction can be treated as a factor in carcinogenesis. Thus, we put forward that energy metabolism might be as a key point for studying carcinogenesis and tumor development to propose new methods for cancer prevention and therapy.

Nutrient depletion and metabolic profiles in breast carcinoma cell lines measured with a label-free platform

The response of two well-characterized human breast cancer cell lines (MCF-7 and MDA-MB-231) to a series of nutrient deficiencies is investigated with a label-free cell assay platform. The motivation of the research is to analyze adaptive responses of tumor cell metabolism and to find limiting conditions for cell survival. The platform measures extracellular values of pH and dissolved oxygen saturation to provide data of extracellular acidification rates and oxygen uptake rates. Additional electric cell substrate impedance sensing and bright-field cell imaging supports the data interpretation by providing information about cell morphological parameters. A sequential administration of nutrient depletions does not cause metabolic reprogramming, since the ratios of oxygen uptake to acidification return to their basal values. While the extracellular acidification drops sharply upon reduction of glucose and glutamine, the oxygen uptake is not affected. In contrast to other published data, cell death is not observed when both glucose and glutamine are depleted and cell proliferation is not inhibited, at least in MCF-7 cultures. It is assumed that residual concentrations of nutrients from the serum component are able to maintain cell viability when delivered regularly by active flow like in the cell assay platform, and, in a similar way, under physiological conditions.

Glutamate dehydrogenase 1 signals through antioxidant glutathione peroxidase 1 to regulate redox homeostasis and tumor growth

How mitochondrial glutaminolysis contributes to redox homeostasis in cancer cells remains unclear. Here we report that the mitochondrial enzyme glutamate dehydrogenase 1 (GDH1) is commonly upregulated in human cancers. GDH1 is important for redox homeostasis in cancer cells by controlling the intracellular levels of its product alpha-ketoglutarate and subsequent metabolite fumarate. Mechanistically, fumarate binds to and activates a reactive oxygen species scavenging enzyme glutathione peroxidase 1. Targeting GDH1 by shRNA or a small molecule inhibitor R162 resulted in imbalanced redox homeostasis, leading to attenuated cancer cell proliferation and tumor growth.

Targeting tumor microenvironment: crossing tumor interstitial fluid by multifunctional nanomedicines

Introduction: The genesis of cancer appears to be a complex matter, which is not simply based upon few genetic abnormalities/alteration. In fact, irregular microvasculature and aberrant interstitium of solid tumors impose significant pathophysiologic barrier functions against cancer treatment modalities, hence novel strategies should holistically target bioelements of tumor microenvironment (TME). In this study, we provide some overview and insights on TME and important strategies used to control the impacts of such pathophysiologic barriers.

Methods: We reviewed all relevant literature for the impacts of tumor interstitium and microvasculature within the TME as well as the significance of the implemented strategies.

Results: While tumorigenesis initiation seems to be in close relation with an emergence of hypoxia and alterations in epigenetic/genetic materials, large panoplies of molecular events emerge as intricate networks during oncogenesis to form unique lenient TME in favor of tumor progression. Within such irregular interstitium, immune system displays defective surveillance functionalities against malignant cells. Solid tumors show multifacial traits with coadaptation and self-regulation potentials, which bestow profound resistance against the currently used conventional chemotherapy and immunotherapy agents that target solely one face of the disease.

Conclusion: The cancerous cells attain unique abilities to form its permissive microenvironment, wherein (a) extracellular pH is dysregulated towards acidification, (b) extracellular matrix (ECM) is deformed, (c) stromal cells are cooperative with cancer cells, (d) immune system mechanisms are defective, (e) non-integrated irregular microvasculature with pores (120-1200 nm) are formed, and (h) interstitial fluid pressure is high. All these phenomena are against cancer treatment modalities. As a result, to control such abnormal pathophysiologic traits, novel cancer therapy strategies need to be devised using multifunctional nanomedicines and theranostics.

Acetaldehyde is an oxidative stressor for gastric epithelial cells

Alcohol drinking and smoking contain the risk of a carcinogenesis. Acetaldehyde is content in cigarette smoke and an ethanol metabolite. However the clear evidence for reactive oxygen species (ROS) generation by acetaldehyde in gastric cells in vitro is none. In this study, we elucidated acetaldehyde is an oxidative stress inducer on rat gastric epithelial cells by electron paramagnetic resonance measurement in living cells. We also confirmed whether acetaldehyde-induced cellular ROS was derived from mitochondria or not. The results of cellular ROS determination showed that an increment of cellular ROS was shown for 15 min in living cells from exposing 0.1% (v/v) acetaldehyde. Lipid peroxidation in cellular membrane also induced by 0.1% ethanol and the tendency is same in the results of cellular ROS determination. JC-1 stained showed the decrement of mitochondrial membrane potential. These results indicated that acetaldehyde is not merely a necrotizing factor for gastric epithelial cells, but also an oxidative stress inducer via injured mitochondria.

Alcohol is an oxidative stressor for gastric epithelial cells: detection of superoxide in living cells

Alcohol/ethanol has been reported to derived necrosis and apoptosis with an oxidative stress in gastric mucosal cells. However the clear evidence for reactive oxygen species (ROS) generation by alcohol in gastric cells in vitro is none. In this study, we elucidated ethanol is an oxidative stress inducer on rat gastric epithelial cells by electron paramagnetic resonance measurement in living cells. We also confirmed whether ethanol-induced cellular ROS was derived from mitochondria or not. The results of cellular ROS determination showed that an increment of cellular ROS was shown for 15 min from exposing 1% (v/v) ethanol. Lipid peroxidation in cellular membrane also induced by 1% ethanol and the tendency is same in the results of cellular ROS determination. JC-1 stained showed the decrement of mitochondrial membrane potential. Additionally the localization of cellular ROS coincided with mitochondria. These results indicated that ethanol is not merely a necrotizing factor for gastric epithelial cells, but also an oxidative stress inducer via injured mitochondria.

Expression of glutamine metabolism-related proteins according to molecular subtype of breast cancer

The aim of this study was to investigate the expression of glutamine metabolism-related proteins to determine whether glutamine is metabolized differently according to breast cancer molecular subtype. We generated a tissue microarray of 702 breast cancer patients and performed immunohistochemical staining for glutamine metabolism-related proteins, including glutaminase 1 (GLS1 (GLS)), glutamate dehydrogenase (GDH (H6PD)), and amino acid transporter-2 (ASCT2 (SLC1A5)), which were separately evaluated in tumor and stroma compartments and then analyzed by breast cancer molecular subtypes. Breast cancers were classified as follows: 293 luminal A (41.7%), 166 luminal B (23.6%), 67 HER2 type (9.6%), and 176 TNBC (25.1%). HER2 type showed the highest stromal GLS1 (P=0.001), tumoral GDH (P=0.001), stromal GDH (P<0.001), and tumoral ASCT (P<0.001) expression. We identified differential expression of glutamine metabolism-related proteins according to molecular subtype of breast cancer. The highest glutamine metabolic activity was seen in HER2-type breast cancer.

The expression of glutamine-metabolism-related proteins in breast phyllodes tumors

The aim of this study was to investigate the expression of glutamine-metabolism-related proteins according to the histologic grade of phyllodes tumors (PTs) and to assess its clinical implication. We generated tissue microarrays of 224 PTs and performed immunohistochemical staining and western blot analysis of glutamine-metabolism-related molecules, including GLS1, GDH, and ASCT2. The associations between immunohistochemical results and clinicopathologic parameters were evaluated. The expression of GLS1 (p < 0.001), GDH (p < 0.001), and ASCT2 (p = 0.005) in stromal components significantly increased with worsening PT histological grade. GDH expression in epithelial components significantly increased in high-grade PT (p = 0.026). In western blot, stromal expression of GLS1, GDH, and ASCT2 increased as histologic grade increased. By univariate analysis, stromal GLS1 expression (p = 0.022) and stromal GDH expression (p = 0.009) were independent predictors of shorter DFS. Stromal GLS1 expression (p < 0.001) and stromal GDH expression (p < 0.001) were independent predictors of shorter OS. This study demonstrated that the stromal expression of the glutamine-metabolism-related proteins GLS1, GDH, ASCT2 increases with worsening histological PT grade.

Wnt/β-catenin signaling pathway and thioredoxin-interacting protein (TXNIP) mediate the "glucose sensor" mechanism in metastatic breast cancer-derived cells MDA-MB-231

In this study we investigated the effect of glucose on GSK3β and β-catenin expression and the involvement of the N-linked glycosylation and hexosamine pathways in the Wnt canonical pathway in response to in vitro conditions resembling normoglycemia (5  mmol) and hyperglycemia (20  mmol) in the metastatic breast cancer-derived cell line MDA-MB-231. We also investigated the relationship between this circuitry and the thioredoxin-interacting protein (TXNIP) regulation that seems to be related. MDA-MB-231 cells were grown either in 5 or 20  mM glucose chronically prior to plating. For glucose shift (5/20), cells were plated in 5  mM glucose and shifted to 20  mM at time 0. Both protein and mRNA levels for GSK3β but only the protein expression for β-catenin, were increased in response to high glucose. Furthermore, we assessed the response of GSK3β, β-catenin, and TXNIP to inhibition of the N-linked glycosylation, hexosamine, and Wnt pathways. Wnt signaling pathway activation was validated by specific reporter assay. We show that high levels of glucose regulate mRNA and protein expression of GSK3β, and consequently higher levels of activated β-catenin protein, which locates to the nucleus and is associated with increased levels of cyclin D1 expression. This event coincides with increased level of N-terminal Ser 9 phosphorylation of GSK3β protein. The inhibition of both the hexosamine pathway and N-linked glycosylation along with Wnt signaling pathway by sFRP1 and DKK1 is associated with significant decrease of the protein levels of GSK3β, β-catenin, and TXNIP RNA. Our work illuminates a novel and never described before function of this signaling pathway that relates glucose metabolism with redox regulation mechanism.

Metformin and thiazolidinediones are associated with improved breast cancer-specific survival of diabetic women with HER2+ breast cancer

BACKGROUND

Insulin/insulin-like growth factor-I (IGF-I) signaling is a mechanism mediating the promoting effect of type 2 diabetes (DM2) on cancer. Human epidermal growth factor receptor (HER2), insulin receptor and IGF-I receptor involve the same PI3K/AKT/mTOR signaling, and different antidiabetic pharmacotherapy may differentially affect this pathway, leading to different prognoses of HER2+ breast cancer.

METHODS

We reviewed 1983 consecutive patients with HER2+ breast cancer treated between 1 January 1998 and 30 September 2010. The overall survival, breast cancer-specific death rate, age, race, nuclear grade, stage, menopausal status, estrogen and progesterone receptor status, body mass index and classes of antidiabetic pharmacotherapy were analyzed.

RESULTS

A Cox regression analysis showed that DM2 [P=0.026, hazard ratio (HR)=1.42, 95 % confidence interval (95 % CI) 1.04-1.94] predicted poor survival of stage≥2 HER2+ breast cancer. In Kaplan-Meier analysis, metformin predicted lengthened survival and so did thiazolidinediones. Analyzing only the diabetics, Cox regression showed that metformin (P=0.041, HR=0.52, 95 % CI 0.28-0.97) and thiazolidinediones (P=0.036; HR=0.41, 95% CI 0.18-0.93) predicted lengthened survival, and competing risk analysis showed that metformin and thiazolidinediones were associated with decreased breast cancer-specific mortality (P=0.023, HR=0.47, 95% CI 0.24-0.90 and P=0.044, HR=0.42, 95 % CI 0.18-0.98, respectively).

CONCLUSIONS

Thiazolidinediones and metformin users are associated with better clinical outcomes than nonusers in diabetics with stage≥2 HER2+ breast cancer. The choice of antidiabetic pharmacotherapy may influence prognosis of this group.