Warburg Effect In Cancer Research Articles

Understanding the Warburg Effect in Cancer.

Rapidly proliferating cells, including cancer cells, adapt metabolism to meet the increased energetic and biosynthetic demands of cell growth and division. Many rapidly proliferating cells exhibit increased glucose consumption and fermentation regardless of oxygen availability, a phenotype termed aerobic glycolysis or the Warburg effect in cancer. Several explanations for why cells engage in aerobic glycolysis and how it supports proliferation have been proposed, but none can fully explain all conditions and data where aerobic glycolysis is observed. Nevertheless, there is convincing evidence that the Warburg effect is important for the proliferation of many cancers, and that inhibiting either glucose uptake or fermentation can impair tumor growth. Here, we discuss what is known about metabolism associated with aerobic glycolysis and the evidence supporting various explanations for why aerobic glycolysis may be important in cancer and other contexts.

PRMT1 promotes Warburg effect by regulating the PKM2/PKM1 ratio in non-small cell lung cancer

Abnormal epigenetic modifications are involved in the regulation of Warburg effect in tumor cells. Protein arginine methyltransferases (PRMTs) mediate arginine methylation and have critical functions in cellular responses. PRMTs are deregulated in a variety of cancers, but their precise roles in Warburg effect in cancer is largely unknown. Experiments from the current study showed that PRMT1 was highly expressed under conditions of glucose sufficiency. PRMT1 induced an increase in the PKM2/PKM1 ratio through upregulation of PTBP1, in turn, promoting aerobic glycolysis in non-small cell lung cancer (NSCLC). The PRMT1 level in p53-deficient and p53-mutated NSCLC remained relatively unchanged while the expression was reduced in p53 wild-type NSCLC under conditions of glucose insufficiency. Notably, p53 activation under glucose-deficient conditions could suppress USP7 and further accelerate the polyubiquitin-dependent degradation of PRMT1. Melatonin, a hormone that inhibits glucose intake, markedly suppressed cell proliferation of p53 wild-type NSCLC, while a combination of melatonin and the USP7 inhibitor P5091 enhanced the anticancer activity in p53-deficient NSCLC. Our collective findings support a role of PRMT1 in the regulation of Warburg effect in NSCLC. Moreover, combination treatment with melatonin and the USP7 inhibitor showed good efficacy, providing a rationale for the development of PRMT1-based therapy to improve p53-deficient NSCLC outcomes.

Targeting the Warburg Effect in Cancer: Where Do We Stand?

The Warburg effect, characterized by the preferential conversion of glucose to lactate even in the presence of oxygen and functional mitochondria, is a prominent metabolic hallmark of cancer cells and has emerged as a promising therapeutic target for cancer therapy. Elevated lactate levels and acidic pH within the tumor microenvironment (TME) resulting from glycolytic profoundly impact various cellular populations, including macrophage reprogramming and impairment of T-cell functionality. Altogether, the Warburg effect has been shown to promote tumor progression and immunosuppression through multiple mechanisms. This review provides an overview of the current understanding of the Warburg effect in cancer and its implications. We summarize recent pharmacological strategies aimed at targeting glycolytic enzymes, highlighting the challenges encountered in achieving therapeutic efficacy. Additionally, we examine the utility of the Warburg effect as an early diagnostic tool. Finally, we discuss the multifaceted roles of lactate within the TME, emphasizing its potential as a therapeutic target to disrupt metabolic interactions between tumor and immune cells, thereby enhancing anti-tumor immunity.

Novel Antineoplastic Inducers of Mitochondrial Apoptosis in Human Cancer Cells.

I propose a new strategy to suppress human cancer completely with two entirely new drug compounds exploiting cancer's Warburg effect characterized by a defective mitochondrial aerobic respiration, substituted by cytosolic aerobic fermentation/glycolysis of D-(+)-glucose into L-(+)-lactic acid. The two essentially new drugs, compound 1 [P(op)T(est)162] and compound 3 (PT167), represent new highly symmetric, four-bladed propeller-shaped polyammonium cations. The in vitro antineoplastic highly efficacious drug compound 3 represents a covalent combination of compound 1 and compound 2 (PT166). The intermediate drug compound 2 is an entirely new colchic(in)oid derivative synthesized from colchicine. Compound 2's structure was determined using X-ray crystallography. Compound 1 and compound 3 were active in vitro versus 60 human cancer cell lines of the National Cancer Institute (NCI) Developmental Therapeutics Program (DTP) 60-cancer cell testing. Compound 1 and compound 3 not only stop the growth of cancer cells to ±0% (cancerostatic effect) but completely kill nearly all 60 cancer cells to a level of almost -100% (tumoricidal effect). Compound 1 and compound 3 induce mitochondrial apoptosis (under cytochrome c release) in all cancer cells tested by (re)activating (in most cancers impaired) p53 function, which results in a decrease in cancer's dysregulated cyclin D1 and an induction of the cell cycle-halting cyclin-dependent kinase inhibitor p21Waf1/p21Cip1.

Metabolic Signature of Warburg Effect in Cancer: An Effective and Obligatory Interplay between Nutrient Transporters and Catabolic/Anabolic Pathways to Promote Tumor Growth.

Aerobic glycolysis in cancer cells, originally observed by Warburg 100 years ago, which involves the production of lactate as the end product of glucose breakdown even in the presence of adequate oxygen, is the foundation for the current interest in the cancer-cell-specific reprograming of metabolic pathways. The renewed interest in cancer cell metabolism has now gone well beyond the original Warburg effect related to glycolysis to other metabolic pathways that include amino acid metabolism, one-carbon metabolism, the pentose phosphate pathway, nucleotide synthesis, antioxidant machinery, etc. Since glucose and amino acids constitute the primary nutrients that fuel the altered metabolic pathways in cancer cells, the transporters that mediate the transfer of these nutrients and their metabolites not only across the plasma membrane but also across the mitochondrial and lysosomal membranes have become an integral component of the expansion of the Warburg effect. In this review, we focus on the interplay between these transporters and metabolic pathways that facilitates metabolic reprogramming, which has become a hallmark of cancer cells. The beneficial outcome of this recent understanding of the unique metabolic signature surrounding the Warburg effect is the identification of novel drug targets for the development of a new generation of therapeutics to treat cancer.

Exploring the clinical utility of DPP-IV and SGLT2 inhibitors in papillary thyroid cancer: a literature review.

In the realm of clinical management, Papillary Thyroid Cancer (PTC) stands out as a prevalent thyroid malignancy, characterized by significant metabolic challenges, particularly in the context of carbohydrate metabolism. Recent studies have unveiled promising applications of Dipeptidyl Peptidase-IV (DPP-IV) and Sodium-Glucose Cotransporter 2 (SGLT2) inhibitors, which are conventionally employed in the treatment of type 2 diabetes mellitus (T2DM), as potential adjuncts in anticancer therapy. DPP-IV and SGLT2 inhibitors can be imply to counteract the Warburg effect in cancer, with a specific focus on PTC, owing to their potential metabolic advantages and their influence on the tumor microenvironment, achieved by imposing restrictions on glucose accessibility. Consequently, a comprehensive review has been undertaken, involving meticulous examination of the existing body of evidence pertaining to the utilization of DPP-IV and SGLT2 inhibitors in the context of PTC. The mechanisms of action inherent to these inhibitors have been thoroughly explored, drawing upon insights derived from preclinical investigations. Furthermore, this review initiates discussions concerning the implications for future research directions and the formulation of innovative therapeutic strategies for PTC. As the intricate interplay between carbohydrate metabolism, the Warburg effect, and cancer progression garners increasing attention, attaining a comprehensive understanding of the roles played by DPP-IV and SGLT2 inhibitors in PTC management may serve as the cornerstone for novel approaches aimed at enhancing patient care and broadening the spectrum of available therapeutic modalities.

Association Between 18F-Fluorodeoxyglucose Uptake and Mutation Status of Epidermal Growth Factor Receptor in Sinonasal Tract Cancer.

The Warburg effect of cancer has been applied to detect various carcinomas though the 18F-fluorodeoxyglucose (18F-FDG) uptake on positron emission tomography with computed tomography (PET/CT). 18F-FDG-PET/CT in lung cancer predicted the mutation status of epidermoid growth factor receptor (EGFR). This study aimed to investigate whether 18F-FDG uptake parameters were significantly related to EGFR mutation status in patients with sinonasal tract squamous cell carcinoma (STSCC). Twenty-nine tumor specimens of primary STSCC from patients with definitive treatment were collected. The 18F-FDG uptake from primary tumors was not different between mutant- and wild-status of EGFR on either Mann-Whitney U-test or the receiver operating curve. A metabolic tumor volume of ≥25 with the minimum p-value from the log-rank test for STSCC-specific survival was associated with a significantly shorter STSCC-specific, disease-free, local recurrence-free survival on the univariate and multivariate analyses adjusted for the clinical stage, treatment, and EGFR status. 18F-FDG-PET/CT did not predict mutation of the EGFR status in STSCC.

NUSAP1-LDHA-Glycolysis-Lactate feedforward loop promotes Warburg effect and metastasis in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is characterized by hypoxia and hypovascular tumor microenvironment. Nucleolar and spindle associated protein 1 (NUSAP1) is a microtubule-associated protein that is known to be involved in cancer biology. Our study aimed to investigate the role of NUSAP1 in glycolytic metabolism and metastasis in PDAC. Expression and prognostic value of NUSAP1 in PDAC and common gastrointestinal tumors was evaluated. The function of NUSAP1 in PDAC progression was clarified by single-cell RNA-seq and further experiments in vitro, xenograft mouse model, spontaneous PDAC mice model and human tissue microarray. The downstream genes and signaling pathways regulated by NUSAP1 were explored by RNA-Seq. And the regulation of NUSAP1 on Lactate dehydrogenase A (LDHA)-mediated glycolysis and its underlying mechanism was further clarified by CHIP-seq. NUSAP1 was an independent unfavorable predictor of PDAC prognosis that playing a critical role in metastasis of PDAC by regulating LDHA-mediated glycolysis. Mechanically, NUSAP1 could bind to c-Myc and HIF-1α that forming a transcription regulatory complex localized to LDHA promoter region and enhanced its expression. Intriguingly, lactate upregulated NUSAP1 expression by inhibiting NUSAP1 protein degradation through lysine lactylated (Kla) modification, thus forming a NUSAP1-LDHA-glycolysis-lactate feedforward loop. The NUSAP1-LDHA-glycolysis-lactate feedforward loop is one of the underlying mechanisms to explain the metastasis and glycolytic metabolic potential in PDAC, which also provides a novel insights to understand the Warburg effect in cancer. Targeting NUSAP1 would be an attractive paradigm for PDAC treatment.

PTEN loss promotes Warburg effect and prostate cancer cell growth by inducing FBP1 degradation.

RationaleFructose-1,6-bisphosphatase (FBP1) is a tumor suppressor and a key enzyme negatively regulating Warburg effect in cancer. However, regulation of FBP1 protein expression and its exact role in prostate cancer (PCa) is largely unclear. Phosphatase and tensin homolog (PTEN) is one of the most frequently deleted tumor suppressor genes in human PCa. However, the role of PTEN loss in aberrant Warburg effect in cancer remains poorly understood.MethodsExpression of PTEN and FBP1 was analyzed in several PCa cell lines and prostate tumor tissues in mice. Western blot (WB) and RT-PCR approaches were used to examine how PTEN regulates FBP1 expression. Co-immunoprecipitation (co-IP) and in vivo ubiquitination assays were used to define the regulatory mechanisms. A PCa xenograft model was employed to determine the impact of PTEN regulation of FBP1 on PCa growth in vivo.ResultWe demonstrated that in a manner dependent of PI3K/AKT signal pathway PTEN regulated FBP1 expression in various PCa cell lines and tumors in mice. We confirmed that this regulation took place at the protein level and was mediated by SKP2 E3 ubiquitin ligase. Mechanistically, we showed that serine 271 phosphorylation of FBP1 by cyclin-dependent kinases (CDKs) was essential for SKP2-mediated degradation of FBP1 protein induced by PTEN loss. Most importantly, we further showed that loss of PTEN expression enhanced Warburg effect and PCa growth in mice in a manner dependent, at least partially on FBP1 protein degradation.ConclusionsOur results reveal a novel tumor-suppressive feature of PTEN in restraining FBP1 degradation and the Warburg effect. These results also suggest that prohibiting FBP1 protein degradation could be a viable therapeutic strategy for PTEN-deficient PCa.

Probiotic Lactobacillus brevis CLB3 prevents azoxymethane/dextran sulfate sodium-induced colon carcinogenesis in mice by reducing amino acid transport and IL-17A levels and repressing the IL-6/AKT/p-STAT3 signaling pathway

Abstract Amino acid intake plays a crucial role in the Warburg effect of cancer. Gut microbes can regulate intestinal amino acid metabolism. However, it is still unknown whether probiotic therapy can protect the host from intestinal tumor invasion by reducing amino acid intake. With in vitro methods, three acid-tolerant strains from fermented pickles were screened out. Using azoxymethane/dextran sulfate sodium-induced colon cancer models, we evaluated the therapeutic effects of Lactobacillus brevis CLB3, Lactobacillus plantarum XLP, and Lactobacillus johnsonii CM on model mice. Their functional mechanisms were further explained through anatomy section, quantitative reverse transcrip­tion polymerase chain reaction (qRT-PCR), Western blot, and immunohistochemical staining analyses as well as database mining and gut culturomics. The Lactobacillus brevis (L. brevis) CLB3 treatment significantly improved the clinical signs and symptoms of colon cancer, alleviated colon damage, and inhibited colon carcinogenesis in mice. In addition, this treatment significantly increased gut cultivable Lactobacillus abundance, inhibited the expression and translation levels of the tumor metabolism-related solute carrier (SLC) amino acid transporter including SLC7A5 and SLC7A11, lowered circulating interleukin-6 (IL-6) and interleukin-17A (IL-17A) levels, and improved the accumulation of tumor-infiltrating lymphocytes and cancer proliferation factors. These findings suggest that L. brevis CLB3 can reduce amino acid transport, inhibit mammalian target of rapamycin (mTOR) signaling and enhance intestinal anti-tumor immune responses, which provides a potential targeting amino acid transporter strategy for preventing colorectal cancer.

Two transition states of the glycogen shunt and two steady states of gene expression support metabolic flexibility and the Warburg effect in cancer.

Previously we suggested that the early Warburg effect can be explained by the use by cancer cells the glycogen shunt during a rapid increase in glucose concentration. In analogy to the Crabtree effect in yeast, the shunt plays a critical role in maintaining homeostasis of glycolytic intermediate levels during these transitions. We extend this analysis here, and propose that the recently appreciated flexibility of cancer cell glucose and glycogen metabolism involves 4 metabolic states that we recently identified in metabolic control analysis studies of yeast. Under stable conditions of low glucose and normal O2 yeast, and by analogy cancer, cells are in the Respiration State in which through gene expression for oxidizing non glucose substrates. When their environment changes to high glucose with reduced O2 levels, such as occur in tumors, they transition to the Glycolysis State due to gene expression of new glycolytic enzyme isoforms such as PKM2. These isoforms optimize metabolism to sustain the Warburg effect. When the changes in glucose and O2 levels are rapid there may be insufficient time for gene expression to adapt. The metabolic flexibility conferred by 2 states of the glycogen shunt allow the cells to survive these transitions. The model explains experimental observations in cancer such as the function of the glycogen shunt and the frequent expression of PKM2 in cells undergoing the Warburg Effect. A surprising conclusion is that the function of PKM2 is to maintain glycolytic intermediate homeostasis rather than controlling the glycolytic flux. The glycogen shunt may also have an important role in cancer metabolic reprogramming by allowing cancer cells to survive large glucose and oxygen changes during the selection of mutations that lead to the Warburg phenotype

Endogenous Fructose Metabolism Could Explain the Warburg Effect and the Protection of SGLT2 Inhibitors in Chronic Kidney Disease.

Chronic low-grade inflammation underlies the pathogenesis of non-communicable diseases, including chronic kidney diseases (CKD). Inflammation is a biologically active process accompanied with biochemical changes involving energy, amino acid, lipid and nucleotides. Recently, glycolysis has been observed to be increased in several inflammatory disorders, including several types of kidney disease. However, the factors initiating glycolysis remains unclear. Added sugars containing fructose are present in nearly 70 percent of processed foods and have been implicated in the etiology of many non-communicable diseases. In the kidney, fructose is transported into the proximal tubules via several transporters to mediate pathophysiological processes. Fructose can be generated in the kidney during glucose reabsorption (such as in diabetes) as well as from intra-renal hypoxia that occurs in CKD. Fructose metabolism also provides biosynthetic precursors for inflammation by switching the intracellular metabolic profile from mitochondrial oxidative phosphorylation to glycolysis despite the availability of oxygen, which is similar to the Warburg effect in cancer. Importantly, uric acid, a byproduct of fructose metabolism, likely plays a key role in favoring glycolysis by stimulating inflammation and suppressing aconitase in the tricarboxylic acid cycle. A consequent accumulation of glycolytic intermediates connects to the production of biosynthetic precursors, proteins, lipids, and nucleic acids, to meet the increased energy demand for the local inflammation. Here, we discuss the possibility of fructose and uric acid may mediate a metabolic switch toward glycolysis in CKD. We also suggest that sodium-glucose cotransporter 2 (SGLT2) inhibitors may slow the progression of CKD by reducing intrarenal glucose, and subsequently fructose levels.

Tumor-selective, antigen-independent delivery of a pH sensitive peptide-topoisomerase inhibitor conjugate suppresses tumor growth without systemic toxicity.

Topoisomerase inhibitors are potent DNA damaging agents which are widely used in oncology, and they demonstrate robust synergistic tumor cell killing in combination with DNA repair inhibitors, including poly(ADP)-ribose polymerase (PARP) inhibitors. However, their use has been severely limited by the inability to achieve a favorable therapeutic index due to severe systemic toxicities. Antibody-drug conjugates address this issue via antigen-dependent targeting and delivery of their payloads, but this approach requires specific antigens and yet still suffers from off-target toxicities. There is a high unmet need for a more universal tumor targeting technology to broaden the application of cytotoxic payloads. Acidification of the extracellular milieu arises from metabolic adaptions associated with the Warburg effect in cancer. Here we report the development of a pH-sensitive peptide-drug conjugate to deliver the topoisomerase inhibitor, exatecan, selectively to tumors in an antigen-independent manner. Using this approach, we demonstrate potent in vivo cytotoxicity, complete suppression of tumor growth across multiple human tumor models, and synergistic interactions with a PARP inhibitor. These data highlight the identification of a peptide-topoisomerase inhibitor conjugate for cancer therapy that provides a high therapeutic index, and is applicable to all types of human solid tumors in an antigen-independent manner.

Pathogens Hijack Host Cell Metabolism: Intracellular Infection as a Driver of the Warburg Effect in Cancer and Other Chronic Inflammatory Conditions

Abstract The Warburg effect refers to a metabolic state in which cells preferentially use aerobic glycolysis rather than oxidative phosphorylation to generate ATP and macromolecules. A number of chronic inflammatory conditions are characterized by host cells that adopt a sustained, pathological Warburg-like metabolism. In cancer, previously healthy cells shift into a Warburg state centered on rapid energy production and increased cell proliferation that drives tumor formation. Macrophage in atherosclerotic plaque and in sarcoidosis granuloma can also harbor a Warburg-like phenotype that promotes an inflammatory milieu. The question of why host cells in patients with cancer and other chronic inflammatory conditions adapt a pathological Warburg-like metabolism is a matter of debate. This review/hypothesis piece explores how intracellular infection can contribute to this Warburg metabolism or related pathological metabolic states. We detail molecular mechanisms by which viral, bacterial, and protozoan intracellular pathogens can induce, or contribute to, a Warburg-like metabolism in infected host cells in order to meet their own replication and nutritional needs. We also discuss how host defense towards infection may impact cellular metabolic changes. We then provide examples of how many of these same intracellular pathogens have been identified in tumors, atherosclerotic lesions, granuloma, and other tissues containing cells with a Warburg or altered metabolism. Last, we examine further trends associated with infection and host cell metabolism, including how pathogen-driven hijacking of host cell lipid metabolism can support viral, bacterial, and parasite survival and replication.

N6-methyladenosine (m6A) methyltransferase WTAP accelerates the Warburg effect of gastric cancer through regulating HK2 stability

N6-methyladenosine (m6A) is one of the most abundant messenger RNAs modification. Increasing evidence illustrates its critical role on gastric cancer. Here, present research focuses on the potential function of m6A methyltransferase Wilms’ tumour 1-associated protein (WTAP) in gastric cancer tumorigenesis. Firstly, m6A immunoprecipitation sequencing analysis (MeRIP-Seq) analysis demonstrated the m6A profile in gastric cancer cells. Both WTAP and the m6A expression were up-regulated in gastric cancer tissue and cells. The high-expression of WTAP was closely correlated with poor prognosis of gastric cancer patients. Functional experiments illustrated that WTAP promoted the proliferation and glycolytic capacity (glucose uptake, lactate production and extracellular acidification rate) in vitro, and the knockdown of WTAP suppressed the tumor growth in vivo. Mechanistically, HK2 was identified to be the target of WTAP using MeRIP-Seq and MeRIP-qPCR. WTAP enhanced the stability of HK2 mRNA through binding with the 3’-UTR m6A site. In conclusion, our results demonstrate the oncogenic role of WTAP and its m6A-mediated regulation on gastric cancer Warburg effect, providing a novel approach and therapeutic target in gastric cancer.

Cancer and Alzheimer's disease: intracellular pH scales the metabolic disorders.

Alzheimer's disease (AD) and cancer have much in common than previously recognized. These pathologies share common risk factors (inflammation and aging), with similar epidemiological and biochemical features such as impaired mitochondria. Metabolic reprogramming occurs during aging and inflammation. We assume that inflammation is directly responsible of the Warburg effect in cancer cells, with a decreased oxidative phosphorylation and a compensatory highthroughput glycolysis (HTG). Similarly, the Warburg effect in cancer is thought to support an alkaline intracellular pH (pHi), a key component of unrelenting cell growth. In the brain, inflammation results in increased secretion of lactate by astrocytes. The increased uptake of lactic acid by neurons results in the inverse Warburg effect, such as seen in AD. The neuronal activity is dampened by a fall of pHi. Pronounced cytosol acidification results in decreased mitochondrial energy yield as well as apoptotic cell death. The link between AD and cancer is reinforced by the fact that treatment aiming at restoring the mitochondrial activity have been experimentally shown to be effective in both diseases. Low carb diet, lipoic acid, and/or methylene blue could then appear promising in both sets of these clinically diverse diseases.

Lactic acidosis induces resistance to the pan-Akt inhibitor uprosertib in colon cancer cells

BackgroundAkt signalling regulates glycolysis and drives the Warburg effect in cancer, thus decreased glucose utilisation is a pharmacodynamic marker of Akt inhibition. However, cancer cells can utilise alternative nutrients to glucose for energy such as lactate, which is often elevated in tumours together with increased acidity. We therefore hypothesised that lactic acidosis may confer resistance to Akt inhibition.MethodsThe effect of the pan-Akt inhibitor uprosertib (GSK2141795), on HCT116 and LS174T colon cancer cells was evaluated in the presence and absence of lactic acid in vitro. Expression of downstream Akt signalling proteins was determined using a phosphokinase array and immunoblotting. Metabolism was assessed using 1H nuclear magnetic resonance spectroscopy, stable isotope labelling and gas chromatography-mass spectrometry.ResultsLactic acid-induced resistance to uprosertib was characterised by increased cell survival and reduced apoptosis. Uprosertib treatment reduced Akt signalling and glucose uptake irrespective of lactic acid supplementation. However, incorporation of lactate carbon and enhanced respiration was maintained in the presence of uprosertib and lactic acid. Inhibiting lactate transport or oxidative phosphorylation was sufficient to potentiate apoptosis in the presence of uprosertib.ConclusionsLactic acidosis confers resistance to uprosertib, which can be reversed by inhibiting lactate transport or oxidative metabolism.

O-GlcNAcylation of SIX1 enhances its stability and promotes Hepatocellular Carcinoma Proliferation.

It is universally accepted that aberrant metabolism facilitates tumor growth. However, how cancer cells coordinate glucose metabolism and tumor proliferation is largely unknown. Sine oculis homeobox homolog 1 (SIX1) is a transcription factor that belongs to the SIX family and is believed to play an important role in the regulation of the Warburg effect in tumors. However, whether the role of SIX1 and the molecular mechanisms that regulate its activity are similar in hepatocellular carcinoma (HCC) still needs further investigation.Methods: Western blotting was performed to determine the levels of SIX1 and O-linked β-N-acetylglucosaminylation (O-GlcNAcylation) in HCC tissues. Cell Counting Kit 8 (CCK8), colony formation and mouse tumor model assays were used to establish the role of SIX1 and O-GlcNAcylation in HCC processes. Mass spectrometry, immunoprecipitation and site-directed mutagenesis were performed to confirm the O-GlcNAcylation of SIX1.Results: Here, we demonstrated that SIX1, the key transcription factor regulating the Warburg effect in cancer, promotes HCC growth in vitro and in vivo. Furthermore, we revealed that SIX1 could also enhance the levels of a posttranslational modification called O-GlcNAcylation. Importantly, we found that SIX1 was also highly modified by O-GlcNAcylation and that O-GlcNAcylation inhibited the ubiquitination degradation of SIX1. In addition, site-directed mutagenesis at position 276 (T276A) decreased the O-GlcNAcylation level and reversed the protumor effect of SIX1.Conclusions: We conclude that O-GlcNAcylation of SIX1 enhances its stability and promotes HCC proliferation. Our findings illustrate a novel feedback loop of SIX1 and O-GlcNAcylation and show that O-GlcNAcylation of SIX1 is an important way to coordinate glucose metabolism and tumor progression.

Sirtuin 6 and metabolic genes interplay in Warburg effect in cancers.

Under oxygen availability, normal cells undergo mitochondrial oxidative phosphorylation to metabolize glucose and yield up to 36 ATPs per glucose molecule for cellular functions, and undergo non-oxidative metabolism (glycolysis) under hypoxic and proliferating conditions to yield 2 ATP per glucose. These cells metabolize glucose to pyruvate via glycolysis followed by conversion of pyruvate to lactate via lactate dehydrogenase. However, cancer cells have the ability to undergo glycolysis and ferment glucose to lactate regardless of oxygen availability; a phenomenon first addressed by Otto Warburg and called, "Warburg effect". Numerous glycolytic genes/proteins have been identified in tumors; that include glucose transporter 1 (GLUT1), hexokinase 2 (HK2), pyruvate kinase-M2 splice isoform (PKM2), and lactate dehydrogenase (LDH-A). Histone deacetylase sirtuin 6 (SIRT6), an epigenetic regulator, is highly expressed in various cancers. SIRT6 plays an important role in Warburg effect by regulating many glycolytic genes. Loss of SIRT6 enhances tumor growth via enhancing glycolysis. This review is mainly concerned with exploring the most recent advances in understanding the roles of the metabolic genes (GLUT1, HK2, PKM2, and LDH-A) and the epigenetic regulator SIRT6 in cancer metabolism and how SIRT6 can modulate these metabolic genes expression and its possible use as a therapeutic target for cancer treatment.

P07.02 Enhanced glycolysis in glioblastomas is associated with tumor cells migration

Abstract BACKGROUND Glioblastoma is the most common primary brain tumor. Its prognosis remains poor even with the standard treatment - the Stupp protocol.The classic Warburg effect in cancers leads to increased glycolysis which causes acidification of the tumor environment. This phenomenon may favor migration of tumor cells as already reported in pancreatic ductal adenocarcinoma. We therefore hypothesized that enhanced glycolysis in glioblastomas could favor the tumor cell migration. MATERIAL AND METHODS We measured glycolysis by the extracellular acidification rate (ECAR) of several human glioblastomas cell lines (LN229, LN18, T98-G, U87-MG, U373-MG, U118-MG) with the Seahorse Analyzer. To confirm these results, we also measured the intracellular cAMP rates using the Cayman’s Elisa kit and we analyzed by RT-PCR the expression of the main genes coding for enzymes involved in glycolysis in these glioblastomas cell lines. Cell migration was measured with a scratch wound healing assay during 24 hours. RESULTS U118-MG was the glioblastoma cell line with the highest glycolysis rate, the highest production of cAMP and showed a strong expression of glycolysis-associated genes. LN229 was the glioblastoma cell line with the less important glycolysis rate, the lower production of cAMP and showed a weaker expression of glycolysis-associated genes. According to the scratch wound healing assay, U118-MG cells showed a more important migration than LN229 cells at 24 hours. CONCLUSION Glycolysis may be an attractive target to prevent effectively tumor cell migration in glioblastomas. Coupling the evaluation of glycolysis with histomolecular characterization of glioblastomas, could help to identify patients to whom adjuvant therapies that inhibit glycolysis such as fenofibrate could be proposed.