Butyrate elicits a metabolic switch in human colon cancer cells by targeting the pyruvate dehydrogenase complex

Butyrate, a short‐chain fatty acid produced by the colonic bacterial fermentation is able to induce cell growth inhibition and differentiation in colon cancer cells at least partially through its capacity to inhibit histone deacetylases. Since butyrate is expected to impact cellular metabolic pathways in colon cancer cells, we hypothesize that it could exert its antiproliferative properties by altering cellular metabolism. We show that although Caco2 colon cancer cells oxidized both butyrate and glucose into CO₂, they displayed a higher oxidation rate with butyrate as substrate than with glucose. Furthermore, butyrate pretreatment led to an increase cell capacity to oxidize butyrate and a decreased capacity to oxidize glucose, suggesting that colon cancer cells, which are initially highly glycolytic, can switch to a butyrate utilizing phenotype, and preferentially oxidize butyrate instead of glucose as energy source to produce acetyl coA. Butyrate pretreated cells displayed a modulation of glutamine metabolism characterized by an increased incorporation of carbons derived from glutamine into lipids and a reduced lactate production. The butyrate‐stimulated glutamine utilization is linked to pyruvate dehydrogenase complex since dichloroacetate reverses this effect. Furthermore, butyrate positively regulates gene expression of pyruvate dehydrogenase kinases and this effect involves a hyperacetylation of histones at PDK4 gene promoter level. Our data suggest that butyrate exerts two distinct effects to ensure the regulation of glutamine metabolism: it provides acetyl coA needed for fatty acid synthesis, and it also plays a role in the control of the expression of genes involved in glucose utilization leading to the inactivation of PDC.     

Acid production in glycolysis-impaired tumors provides new insights into tumor metabolism.

PURPOSE: Low extracellular pH is a hallmark of solid tumors. It has long been thought that this acidity is mainly attributable to the production of lactic acid. In this study, we tested the hypothesis that lactate is not the only source of acidification in solid tumors and explored the potential mechanisms underlying these often-observed high rates of acid production. EXPERIMENTAL DESIGN: We compared the metabolic profiles of glycolysis-impaired (phosphoglucose isomerase-deficient) and parental cells in both in vitro and two in vivo models (dorsal skinfold chamber and Gullino chamber). RESULTS: We demonstrated that CO(2), in addition to lactic acid, was a significant source of acidity in tumors. We also found evidence supporting the hypothesis that tumor cells rely on glutaminolysis for energy production and that the pentose phosphate pathway is highly active within tumor cells. Our results also suggest that the tricarboxylic acid cycle is saturable and that different metabolic pathways are activated to provide for energy production and biosynthesis. CONCLUSIONS: These results are consistent with the paradigm that tumor metabolism is determined mainly by substrate availability and not by the metabolic demand of tumor cells per se. In particular, it appears that the local glucose and oxygen availabilities each independently affect tumor acidity. These findings have significant implications for cancer treatment.     

Altered glycolysis results in drug-resistant in clinical tumor therapy

Cancer cells undergo metabolic reprogramming, including increased glucose metabolism, fatty acid synthesis and glutamine metabolic rates. These enhancements to three major metabolic pathways are closely associated with glycolysis, which is considered the central component of cancer cell metabolism. Increasing evidence suggests that dysfunctional glycolysis is commonly associated with drug resistance in cancer treatment, and aberrant glycolysis plays a significant role in drug-resistant cancer cells. Studies on the development of drugs targeting these abnormalities have led to improvements in the efficacy of tumor treatment. The present review discusses the changes in glycolysis targets that cause drug resistance in cancer cells, including hexokinase, pyruvate kinase, pyruvate dehydrogenase complex, glucose transporters, and lactate, as well the underlying molecular mechanisms and corresponding novel therapeutic strategies. In addition, the association between increased oxidative phosphorylation and drug resistance is introduced, which is caused by metabolic plasticity. Given that aberrant glycolysis has been identified as a common metabolic feature of drug-resistant tumor cells, targeting glycolysis may be a novel strategy to develop new drugs to benefit patients with drug-resistance.     

BMP4 augments the survival of hepatocellular carcinoma (HCC) cells under hypoxia and hypoglycemia conditions by promoting the glycolysis pathway

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer death worldwide although its pathogenic mechanism remains to be fully understood. Unlike normal cells, most cancer cells rely on aerobic glycolysis and are more adaptable to the microenvironment of hypoxia and hypoglycemia. Bone Morphogenetic Protein 4 (BMP4) plays important roles in regulating proliferation, differentiation, invasion and migration of HCC cells. We have recently shown that BMP4 plays an important role in regulating glucose metabolism although the effect of BMP4 on glucose metabolic reprogramming of HCC is poorly understood. In this study, we found that BMP4 was highly expressed in HCC tumor tissues, as well as HCC cell lines that were tolerant to hypoxia and hypoglycemia. Mechanistically, we demonstrated that BMP4 protected HCC cells from hypoxia and hypoglycemia by promoting glycolysis since BMP4 up-regulated glucose uptake, the lactic acid production, the ATP level, and the activities of rate limiting enzymes of glycolysis (including HK2, PFK and PK). Furthermore, we demonstrated that BMP4 up-regulated HK2, PFKFB3 and PKM2 through the canonical Smad signal pathway as SMAD5 directly bound to the promoter of PKM. Collectively, our findings shown that BMP4 may play an important role in regulating glycolysis of HCC cells under hypoxia and hypoglycemia condition, indicating that novel therapeutics may be developed to target BMP4-regulated glucose metabolic reprogramming in HCC.     

Glutamine at focus: versatile roles in cancer

During the past decade, a heightened understanding of metabolic pathways in cancer has significantly increased. It is recognized that many tumor cells are genetically programmed and have involved an abnormal metabolic state. Interestingly, this increased metabolic autonomy generates dependence on various nutrients such as glucose and glutamine. Both of these components participate in various facets of metabolic activity that allow for energy production, synthesis of biomass, antioxidant defense, and the regulation of cell signaling. Here, we outline the emerging data on glutamine metabolism and address the molecular mechanisms underlying glutamine-induced cell survival. We also discuss novel therapeutic strategies to exploit glutamine addiction of certain cancer cell lines.     

La tumeur cancéreuse : un parasite métabolique ?

Cancer cells activate glycolysis, glutaminolysis and β-oxidation to promote their biosynthesis. The low activity of pyruvate kinase, reexpressed in its embryonic isoform PKM2, generates a bottleneck at the end of glycolysis, which reorients glucose catabolism towards formation of molecules implied in numerous synthesis: ribose for nucleic acids, glycerol for lipid synthesis, etc. However, a part of glucose is transformed in pyruvate, which also comes from aminoacids catabolism. Due to the inhibition of pyruvate dehydrogenase, pyruvate is preferentially transformed into lactate, either in the presence of oxygen (Warburg effect). Lactate dehydrogenase reaction furnishes lactic acid, which acidifies the tumoral microenvironment, a process which favors the cellular growth and regenerates NAD⁺, a crucial cofactor for the functioning of various metabolic pathways (glycolysis, DNA synthesis and repair…). Cancer cells consume a lot of glutamine, which replenish Krebs cycle (coupled with ATP production), and/or furnishes aspartate for nucleotides synthesis. This particular metabolism is sustained by activation of oncogenes (Myc, AKT, etc.) and suppressors inactivation (P53, PTEN…). Like a parasite, cells draw on reserves of the host to supply their own biosynthesis, while they secrete waste products (NO, polyamines, ammonia, lactate…) that promote cellular growth. A “symbiotic” cooperation could be established between tumor cells themselves, and/or with environmental cells, to maximize ATP production in relation with resources and oxygen concentration.     

脂代谢重编程在前列腺癌中的研究进展

代谢重编程在肿瘤的发生发展过程中扮演着重要角色,为肿瘤细胞的生命活动提供了必要的物质基础,并对肿瘤的生物学行为起促进作用。代谢重编程可引起肿瘤细胞中氨基酸、葡萄糖和脂肪酸的代谢模式发生改变,是肿瘤的标志性特征之一。目前发现大多数肿瘤倾向利用糖酵解产生的Warburg效应为自身供能,而研究表明前列腺癌细胞更依赖脂肪酸氧化途径进行代谢重编程获取能量物质。因此,深度掌握脂质代谢关键酶和相关调控基因间的关系,对前列腺癌早期诊断、精准靶向治疗及获得更好的疾病预后具有重要意义。     

Glutaminase: A Hot Spot For Regulation Of Cancer Cell Metabolism?

Cancer cells re-program their metabolic machinery in order to satisfy their bioenergetic and biosynthetic requirements. A critical aspect of the re-programming of cancer cell metabolism involves changes in the glycolytic pathway (referred to as the "Warburg effect"). As an outcome of these changes, much of the pyruvate generated via the glycolytic pathway is converted to lactic acid, rather than being used to produce acetyl-CoA and ultimately, the citrate which enters the citric acid cycle. In order to compensate for these changes and to help maintain a functioning citric acid cycle, cancer cells often rely on elevated glutamine metabolism. Recently, we have found that this is achieved through a marked elevation of glutaminase activity in cancer cells. Here we further consider these findings and the possible mechanisms by which this important metabolic activity is regulated.     

有氧糖酵解促进肿瘤转移及干性的研究进展

癌症已成为全球第二大死亡原因,是危害严重的全球健康问题。虽然医学发展迅速,治疗方法也在不断改进,可是由于肿瘤复发和远端转移的存在,目前肿瘤患者仍然预后不良,生存率无法提高。近期肿瘤细胞中的“代谢重编程”给我们提供了新的思路,肿瘤细胞中从氧化磷酸化到糖酵解的代谢转换可以影响肿瘤细胞干性,参与调节肿瘤的侵袭与远端转移。本文总结了近年来关于肿瘤细胞有氧糖酵解的相关研究,就肿瘤细胞中的糖代谢重编程、糖酵解对肿瘤细胞转移及干性的影响,以及潜在机制几方面进行综述,探讨靶向糖酵解联合治疗的可行性,希望有助于肿瘤细胞糖代谢后续的研究,为肿瘤治疗提供新的策略。     

靶向谷氨酰胺代谢途径提高放疗疗效研究进展

放疗是恶性肿瘤治疗的重要手段。放疗抵抗是影响放疗疗效的主要障碍。细胞代谢重编程是癌症的主要特征之一,对放疗疗效可能产生重要的影响。谷氨酰胺与肿瘤细胞生物合成和生长密切相关,并通过分解产生抗氧化剂影响放疗敏感度。另外,谷氨酰胺的两种同工酶谷氨酰胺酶(GLS)和谷氨酰胺酶2(GLS2)的表达和功能不同,对放疗敏感度存在重要影响。利用肿瘤微环境中的谷氨酰胺代谢来提高放疗疗效具有重要的研究价值。本文主要综述恶性肿瘤的谷氨酰胺代谢特征以及谷氨酰胺酶抑制剂对放疗的增敏效应。     

The amino acid metabolism is essential for evading physical plasma-induced tumour cell death

Background Recent studies have emphasised the important role of amino acids in cancer metabolism. Cold physical plasma is an evolving technology employed to target tumour cells by introducing reactive oxygen species (ROS). However, limited understanding is available on the role of metabolic reprogramming in tumour cells fostering or reducing plasma-induced cancer cell death.Methods The utilisation and impact of major metabolic substrates of fatty acid, amino acid and TCA pathways were investigated in several tumour cell lines following plasma exposure by qPCR, immunoblotting and cell death analysis.Results Metabolic substrates were utilised in Panc-1 and HeLa but not in OVCAR3 and SK-MEL-28 cells following plasma treatment. Among the key genes governing these pathways, ASCT2 and SLC3A2 were consistently upregulated in Panc-1, Miapaca2GR, HeLa and MeWo cells. siRNA-mediated knockdown of ASCT2, glutamine depletion and pharmacological inhibition with V9302 sensitised HeLa cells to the plasma-induced cell death. Exogenous supplementation of glutamine, valine or tyrosine led to improved metabolism and viability of tumour cells following plasma treatment.Conclusion These data suggest the amino acid influx driving metabolic reprogramming in tumour cells exposed to physical plasma, governing the extent of cell death. This pathway could be targeted in combination with existing anti-tumour agents.Subject terms: Physics, Cancer metabolism     

肝肿瘤细胞干性与糖代谢特点的相关性研究

背景与目的：肝细胞肝癌是致死率第三的恶性肿瘤,肿瘤干细胞则被认为是肿瘤复发的种子,而温伯格效应指肿瘤细胞有氧糖酵解的代谢特点。旨在探究肝肿瘤细胞干性与细胞糖代谢特点的相关性。方法：利用流式细胞术分选肝肿瘤细胞系Huh-7、MHCC97H中干性标志物高表达的肿瘤细胞进行无血清悬浮培养,观察其形态变化并对其干性标志物、糖代谢酶的表达进行检测,随后对这两种细胞的葡萄糖摄取能力、乳酸生成能力进行对比。结果：肝肿瘤干细胞在无血清悬浮培养的体系中成球,相比非干性的肿瘤细胞,成球细胞的糖酵解关键酶和干性标志物的表达有明显的升高（P<0.05）,对葡萄糖的摄取能力及乳酸的生成能力也有明显的增强（P<0.05）,肿瘤细胞的干性与其糖酵解的活跃程度有相关性。结论：无血清悬浮培养技术可用于富集肝肿瘤干细胞;相比非干性肿瘤细胞,肝肿瘤干细胞的糖酵解转化程度更高,肿瘤细胞的干性和肿瘤细胞的糖酵解有相关性。     

Dichloroacetate improves immune dysfunction caused by tumor‐secreted lactic acid and increases antitumor immunoreactivity

The activation of oncogenic signaling pathways induces the reprogramming of glucose metabolism in tumor cells and increases lactic acid secretion into the tumor microenvironment. This is a well‐known characteristic of tumor cells, termed the Warburg effect, and is a candidate target for antitumor therapy. Previous reports show that lactic acid secreted by tumor cells is a proinflammatory mediator that activates the IL‐23/IL‐17 pathway, thereby inducing inflammation, angiogenesis and tissue remodeling. Here, we show that lactic acid, or more specifically the acidification it causes, increases arginase I (ARG1) expression in macrophages to inhibit T‐cell proliferation and activation. Accordingly, we hypothesized that counteraction of the immune effects by lactic acid might suppress tumor development. We show that dichloroacetate (DCA), an inhibitor of pyruvate dehydrogenase kinases, targets macrophages to suppress activation of the IL‐23/IL‐17 pathway and the expression of ARG1 by lactic acid. Furthermore, lactic acid‐pretreated macrophages inhibited CD8⁺ T‐cell proliferation, but CD8⁺ T‐cell proliferation was restored when macrophages were pretreated with lactic acid and DCA. DCA treatment decreased ARG1 expression in tumor‐infiltrating immune cells and increased the number of IFN‐γ‐producing CD8⁺ T cells and NK cells in tumor‐bearing mouse spleen. Although DCA treatment alone did not suppress tumor growth, it increased antitumor immunotherapeutic activity of Poly(IC) in both CD8⁺ T cell‐ and NK cell‐sensitive tumor models. Therefore, DCA acts not only on tumor cells to suppress glycolysis but also on immune cells to improve the immune status modulated by lactic acid and to increase the effectiveness of antitumor immunotherapy.     

四种肝（癌）细胞系糖代谢的流量解析

 目的 分析人正常肝细胞（HL-7702）、不同转移潜能的肝细胞癌细胞系（SMMC-7721、HCCLM3）以及肝癌门静脉癌栓细胞系（CSQT2）的糖代谢流量及相关基因表达。方法 利用稳定同位素13C标记的葡萄糖与谷氨酰胺作为营养源，结合酶活实验，对四种细胞进行糖代谢流量解析。结果 MTT与Transwell实验证实了HL-7702、SMMC-7721、HCCLM3、CSQT2细胞的增殖与迁移能力依次增加。酶活实验与标记实验结果均显示，糖酵解与三羧酸循环的代谢活性在四种细胞中依次增加，具体表现为葡萄糖消耗与乳酸产生的增加，代谢流量比率在多种糖代谢产物中的上升，尤其是在CSQT2细胞中达到最高。结论 随着肝癌细胞的恶性程度及转移能力的增加，糖酵解与三羧酸循环的代谢活性增加。代谢流量分析可能用以判断肝癌的发生发展与转移。     

脂肪酸从头合成代谢重编程与肿瘤的发生发展

肿瘤细胞代谢重编程是肿瘤发生发展过程中最显著的特征之一,是对肿瘤有氧糖酵解（即Warburg效应）内涵的进一步扩展。细胞癌变过程的代谢模式发生显著变化,涉及到糖酵解、氧化磷酸化、氨基酸代谢、脂肪酸代谢和核酸代谢等诸多方面,其中脂肪酸代谢在肿瘤细胞的能量存储、细胞增殖及重要信号分子合成等方面起到重要作用。研究脂肪酸从头合成代谢的机制与肿瘤发生发展的关系,利用、干预和修正代谢通路上关键酶的异常,正成为肿瘤诊断、预防和治疗的新思路。本文就脂肪酸从头合成代谢重编程与肿瘤发生发展的关系做一综述。      

Metabolic reprogramming in glioblastoma: the influence of cancer metabolism on epigenetics and unanswered questions

A defining hallmark of glioblastoma is altered tumor metabolism. The metabolic shift towards aerobic glycolysis with reprogramming of mitochondrial oxidative phosphorylation, regardless of oxygen availability, is a phenomenon known as the Warburg effect. In addition to the Warburg effect, glioblastoma tumor cells also utilize the tricarboxylic acid cycle/oxidative phosphorylation in a different capacity than normal tissue. Altered metabolic enzymes and their metabolites are oncogenic and not simply a product of tumor proliferation. Here we highlight the advantages of why tumor cells, including glioblastoma cells, require metabolic reprogramming and how tumor metabolism can converge on tumor epigenetics and unanswered questions in the field.     

Metabolic rewiring of pancreatic ductal adenocarcinoma: New routes to follow within the maze

Pancreatic ductal adenocarcinoma (PDAC) is a debilitating and almost universally fatal malignancy. Despite advances in understanding of the oncogenetics of the disease, very few clinical benefits have been shown. One of the main characteristics of PDAC is the tumor architecture where tumor cells are surrounded by a firm desmoplasia. By reducing vascularization, thus both oxygen and nutrients delivery to the tumor, this stroma causes the appearance of hypoxic zones driving metabolic adaptation in surviving tumor cells in order to cope with challenging conditions. This metabolic reprogramming promoted by environmental constraints enhances PDAC aggressiveness. In this review, we provide a brief overview of previous works regarding the importance of glucose and glutamine addiction of PDAC cells. In particular we aim to highlight the need for exploring the impact of metabolites other than glucose and glutamine, such as non‐essential amino acids and oncometabolites, to find new treatments. We also discuss the need for progress in methodology for metabolites detection. The overall purpose of our review is to emphasize the need to look beyond what is currently known, with a focus on amino acid availability, in order to improve our understanding of PDAC biology.     

Cibler le métabolisme tumoral : efficacité et perspectives

Metabolic reprogramming is a hallmark of cancer which will provide tumor cells with all metabolites needed for growth and proliferation. Numerous oncogenes are responsible for a cellular metabolic reprogramming as part of their transforming role which illustrates the potential therapeutic advantage of targeting cancer metabolism. Anti-metabolites drugs, such as methotrexate or L-asparignase, have proven to be effective in many cancers and brought the proof of concept of cancer metabolism targeting. This justifies the development of new agents in this domain. When developing such molecules, many challenges are faced: to avoid toxicity linked to metabolism inhibition of normal cells, to anticipate redundancy of metabolic pathways which could abrogate efficacy, and to identify new targets and biomarkers. Therefore, cancer metabolism targeting is part of oncologic personalized medicine. Clinical and mostly pre-clinical researches are ongoing for glucose, glutamine, fatty acids, amino acids metabolism, and TCA cycle targeting. Genome scale Metabolic Modeling (GSMM) has been proven to be effective in identifying new metabolic targets. Cancer metabolism targeting is a promising way to treat cancer which has already proven efficacy with anti-metabolite drugs. At the moment, most of the data are preclinical but clinical trial of such agents will undoubtedly be set in the future.     

Transglutaminase 2 reprogramming of glucose metabolism in mammary epithelial cells via activation of inflammatory signaling pathways

Aberrant glucose metabolism characterized by high levels of glycolysis, even in the presence of oxygen, is an important hallmark of cancer. This metabolic reprogramming referred to as the Warburg effect is essential to the survival of tumor cells and provides them with substrates required for biomass generation. Molecular mechanisms responsible for this shift in glucose metabolism remain elusive. As described herein, we found that aberrant expression of the proinflammatory protein transglutaminase 2 (TG2) is an important regulator of the Warburg effect in mammary epithelial cells. Mechanistically, TG2 regulated metabolic reprogramming by constitutively activating nuclear factor (NF)‐κB, which binds to the hypoxia‐inducible factor (HIF)?1α promoter and induces its expression even under normoxic conditions. TG2/NF‐κB‐induced increase in HIF‐1α expression was associated with increased glucose uptake, increased lactate production and decreased oxygen consumption by mitochondria. Experimental suppression of TG2 attenuated HIF‐1α expression and reversed downstream events in mammary epithelial cells. Moreover, downregulation of p65/RelA or HIF‐1α expression in these cells restored normal glucose uptake, lactate production, mitochondrial respiration and glycolytic protein expression. Our results suggest that aberrant expression of TG2 is a master regulator of metabolic reprogramming and facilitates metabolic alterations in epithelial cells even under normoxic conditions. A TG2‐induced shift in glucose metabolism helps breast cancer cells to survive under stressful conditions and promotes their metastatic competence.