Clinical impact of the Warburg effect in gastrointestinal cancer (review)

DDQN-based optimal targeted therapy with reversible inhibitors to combat the Warburg effect

We cover the Warburg effect with a three-component evolutionary model, where each component represents a different metabolic strategy. In this context, a scenario involving cells expressing three different phenotypes is presented. One tumour phenotype exhibits glycolytic metabolism through glucose uptake and lactate secretion. Lactate is used by a second malignant phenotype to proliferate. The third phenotype represents healthy cells, which performs oxidative phosphorylation. The purpose of this model is to gain a better understanding of the metabolic alterations associated with the Warburg effect. It is suitable to reproduce some of the clinical trials obtained in colorectal cancer and other even more aggressive tumours. It shows that lactate is an indicator of poor prognosis, since it favours the setting of polymorphic tumour equilibria that complicates its treatment. This model is also used to train a reinforcement learning algorithm, known as Double Deep Q-networks, in order to provide the first optimal targeted therapy based on experimental tumour growth inhibitors as genistein and AR-C155858. Our in silico solution includes the optimal therapy for all the tumour state space and also ensures the best possible quality of life for the patients, by considering the duration of treatment, the use of low-dose medications and the existence of possible contraindications. Optimal therapies obtained with Double Deep Q-networks are validated with the solutions of the Hamilton-Jacobi-Bellman equation.

Enhanced chemotherapeutic efficacy of docetaxel in human lung cancer cell line via GLUT1 inhibitor

The dose-dependent adverse effects of anticancer agents need new methods with lesser toxicity. The objective of the current research was to evaluate the efficacy of GLUT1 inhibitor, as an inhibitor of glucose consumption in cancer cells, in augmenting the efficiency of docetaxel with respect to cytotoxicity and apoptosis. Cell cytotoxicity was assessed by using methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay. Annexin V/PI double staining was employed to evaluate apoptosis percentage. Quantitative real-time polymerase chain reaction (RT-PCR) analysis was accomplished to detect the expression of genes involved in the apoptosis pathway. The IC50 values for docetaxel and BAY-876 were 3.7 ± 0.81 and 34.1 ± 3.4 nM, respectively. The severity of synergistic mutual effects of these agents on each other was calculated by synergy finder application. It showed that the percentage of apoptotic cells following co-administration of docetaxel and BAY-876 increased to 48.1 ± 2.8%. In comparison without GLUT1 co-administration, the combined therapy decreased significantly the transcriptome levels of the Bcl-2 and Ki-67 and a remarkable increase in the level of the Bax as proapoptotic protein(p < 0.05). Co-treatment of BAY-876 and docetaxel depicted a synergistic effect which was calculated using the synergy finder highest single agent (HSA) method (HSA synergy score: 28.055). These findings recommend that the combination of GLUT-1 inhibitor and docetaxel can be considered as a promising therapeutic approach for the treatment of patients with lung cancer.

Purinergic receptors are a key bottleneck in tumor metabolic reprogramming: The prime suspect in cancer therapeutic resistance

ATP and other nucleoside phosphates have specific receptors named purinergic receptors. Purinergic receptors and ectonucleotidases regulate various signaling pathways that play a role in physiological and pathological processes. Extracellular ATP in the tumor microenvironment (TME) has a higher level than in normal tissues and plays a role in cancer cell growth, survival, angiogenesis, metastasis, and drug resistance. In this review, we investigated the role of purinergic receptors in the development of resistance to therapy through changes in tumor cell metabolism. When a cell transforms to neoplasia, its metabolic processes change. The metabolic reprogramming modified metabolic feature of the TME, that can cause impeding immune surveillance and promote cancer growth. The purinergic receptors contribute to therapy resistance by modifying cancer cells' glucose, lipid, and amino acid metabolism. Limiting the energy supply of cancer cells is one approach to overcoming resistance. Glycolysis inhibitors which reduce intracellular ATP levels may make cancer cells more susceptible to anti-cancer therapies. The loss of the P2X7R through glucose intolerance and decreased fatty acid metabolism reduces therapeutic resistance. Potential metabolic blockers that can be employed in combination with other therapies will aid in the discovery of new anti-cancer immunotherapy to overcome therapy resistance. Therefore, therapeutic interventions that are considered to inhibit cancer cell metabolism and purinergic receptors simultaneously can potentially reduce resistance to treatment.

Novel possibility for cutaneous melanoma treatment by means of rosmarinic acid action on purinergic signaling

Cancer cases have increased significantly in Brazil and worldwide, with cutaneous melanoma (CM) being responsible for nearly 57,000 deaths in the world. Thus, this review article aims at exploring and proposed hypotheses with respect to the possibility that RA can be a promising and alternative compound to be used as an adjuvant in melanoma treatment, acting on purinergic signaling. The scarcity of articles evidencing the action of this compound in this signaling pathway requires further studies. Considering diverse evidence found in the literature, we hypothesize that RA can be an effective candidate for the treatment of CM acting as a modulating molecule of purinergic cellular pathway through P2X7 blocking, mitigating the Warburg effect, and as antagonic molecule of the P2Y12 receptor, reducing the formation of adhesive molecules that prevent adherence in tumor cells. In this way, our proposals for CM treatment based on targeting purinergic signaling permeate the integral practice, going from intracell to extracell. Undoubtedly, much is still to be discovered and elucidated about this promising compound, this paper being an interesting work baseline to support more research studies.

Refractory Hyperlactatemia and Hypoglycemia in an Adult with Non-Hodgkin's Lymphoma: A Case Report and Review of the Warburg Effect

Lactate is a byproduct of anaerobic glycolysis, and hyperlactatemia is commonly seen in critically ill patients. We report a case of an elderly male presenting with undifferentiated constitutional symptoms, anemia, thrombocytopenia, severe lactic acidosis, refractory hypoglycemia, and a newly detected abdominal mass. A dedicated workup ruled out infectious etiologies and revealed metastatic non-Hodgkin's lymphoma. This study explores etiologies of type B lactic acidosis in oncology patients, with a focus on Warburg's effect, and its potential for prognostication.

Melatonin and hyperbaric oxygen therapies suppress colorectal carcinogenesis through pleiotropic effects and multifaceted mechanisms

Colorectal cancer (CRC) is the third most common cancer worldwide. Colorectal carcinogenesis is frequently induced by hypoxia to trigger the reprogramming of cellular metabolism and gain of malignant phenotypes. Previously, hyperbaric oxygen (HBO) therapy and melatonin have been reported to alter the hypoxic microenvironment, resulting in inhibiting cancer cell survival. Accordingly, this study tested the hypothesis whether HBO and melatonin effectively inhibited CRC carcinogenesis. In vitro results indicated that melatonin therapy significantly suppressed the malignant phenotypes, including colony formation, growth, invasion, migration and cancer stemness with dose-dependent manners in CRC cell lines through multifaceted mechanisms. Similar to in vitro study, in vivo findings further demonstrated the melatonin, HBO and combined treatments effectively promoted apoptosis (cleaved-caspase 3/ cleaved-PARP) and arrested tumor proliferation, followed by inhibiting colorectal tumorigenesis in CRC xenograft tumor model. Moreover, melatonin, HBO and combined treatments modulated multifaceted mechanisms, including decreasing HIF-1α expression, alleviating AKT activation, repressing glycolytic metabolism (HK-2/PFK1/PKM2/LDH), restraining cancer stemness pathway (TGF-β/p-Smad3/Oct4/Nanog), reducing inflammation (p-NFκB/ COX-2), diminishing immune escape (PD-L1), and reversing expression of epithelial mesenchymal transition (E-cadherin/N-cadherin/MMP9). In conclusion, melatonin and HBO therapies suppressed colorectal carcinogenesis through the pleiotropic effects and multifaceted mechanisms, suggesting melatonin and HBO treatments could be novel therapeutic strategies for CRC treatment.

Isovitexin Suppresses Stemness of Lung Cancer Stem-Like Cells through Blockage of MnSOD/CaMKII/AMPK Signaling and Glycolysis Inhibition

BACKGROUND

Manganese superoxide dismutase (MnSOD) has been reported to promote stemness of lung cancer stem-like cells (LCSLCs) which had higher glycolytic rates compared with non-CSLCs. Isovitexin exhibited an inhibitory effect on the stemness of hepatocellular carcinoma cells. However, whether isovitexin could inhibit the promotion of stemness of LCSLCs mediated by MnSOD through glycolysis remains unclear.

OBJECTIVE

Our study was aimed at investigating whether isovitexin inhibits lung cancer stem-like cells (LCSLCs) through MnSOD signaling blockage and glycolysis suppression.

METHODS

Sphere formation and soft agar assays were conducted to determine self-renewal ability. The migration and invasion of LCSLCs were determined by wound healing and transwell assay. The glycolytic activity was assessed by determination of L-lactate metabolism rate. The influences of isovitexin on MnSOD, CaMKII, and AMPK activations as well as the metabolic shift to glycolysis were determined by manipulating MnSOD expression.

RESULTS

It was found that MnSOD and glycolysis enhanced simultaneously in LCSLCs compared with parental H460 cells. Overexpression of MnSOD activated CaMKII/AMPK signaling and glycolysis in LCSLCs with increased self-renewal, migration, invasion, and expression of stemness-associated markers in vitro and elevated carcinogenicity in vivo. Knockdown of MnSOD induced an inverse effect in LCSLCs. Isovitexin blocked MnSOD/CaMKII/AMPK signaling axis and suppressed glycolysis in LCSLCs, resulting in inhibition of stemness features in LCSLCs. The knockdown of MnSOD significantly augmented isovitexin-associated inhibition of CaMKII/AMPK signaling, glycolysis, and stemness in LCSLCs. However, the overexpression of MnSOD could attenuate the inhibition of isovitexin on LCSLCs. Importantly, isovitexin notably suppressed tumor growth in nude mice bearing LCSLCs by downregulation of MnSOD expression.

CONCLUSION

MnSOD promotion of stemness of LCSLCs derived from H460 cell line is involved in the activation of the CaMKII/AMPK pathway and induction of glycolysis. Isovitexin-associated inhibition of stemness in LCSLCs is partly dependent on blockage of the MnSOD/CaMKII/AMPK signaling axis and glycolysis suppression.

Involvement of Long Non-Coding RNAs in Glucose Metabolism in Cancer

The rapid and uncontrolled proliferation of cancer cells is supported by metabolic reprogramming. Altered glucose metabolism supports cancer growth and progression. Compared with normal cells, cancer cells show increased glucose uptake, aerobic glycolysis and lactate production. Byproducts of adjusted glucose metabolism provide additional benefits supporting hallmark capabilities of cancer cells. Long non-coding RNAs (lncRNAs) are a heterogeneous group of transcripts of more than 200 nucleotides in length. They regulate numerous cellular processes, primarily through physical interaction with other molecules. Dysregulated lncRNAs are involved in all hallmarks of cancer including metabolic alterations. They may upregulate metabolic enzymes, modulate the expression of oncogenic or tumor-suppressive genes and disturb metabolic signaling pathways favoring cancer progression. Thus, lncRNAs are not only potential clinical biomarkers for cancer diagnostics and prediction but also possible therapeutic targets. This review summarizes the lncRNAs involved in cancer glucose metabolism and highlights their underlying molecular mechanisms.

Potential pathways of zinc deficiency-promoted tumorigenesis

Zinc (Zn) is the second most abundant necessary trace element in the human body. It is reported that zinc deficiency (ZD) promotes many types of cancer progression through multiple signal pathways. It is well known that oxidative stress, DNA damage, DNA repair, cell cycle, cell apoptosis, metabolic alterations, microRNAs abnormal expression, and inflammation level are closely related to cancer development. Cumulative evidence suggests that ZD influences these biological functions. This review explores the latest advances in understanding the role of ZD in tumorigenesis. Fully comprehending the potential mechanisms of ZD-induced tumors may provide novel clues for prevention and clinical treatment of cancers.

Purinergic Signaling in the Hallmarks of Cancer

Cancer is a complex expression of an altered state of cellular differentiation associated with severe clinical repercussions. The effort to characterize this pathological entity to understand its underlying mechanisms and visualize potential therapeutic strategies has been constant. In this context, some cellular (enhanced duplication, immunological evasion), metabolic (aerobic glycolysis, failure in DNA repair mechanisms) and physiological (circadian disruption) parameters have been considered as cancer hallmarks. The list of these hallmarks has been growing in recent years, since it has been demonstrated that various physiological systems misfunction in well-characterized ways upon the onset and establishment of the carcinogenic process. This is the case with the purinergic system, a signaling pathway formed by nucleotides/nucleosides (mainly adenosine triphosphate (ATP), adenosine (ADO) and uridine triphosphate (UTP)) with their corresponding membrane receptors and defined transduction mechanisms. The dynamic equilibrium between ATP and ADO, which is accomplished by the presence and regulation of a set of ectonucleotidases, defines the pro-carcinogenic or anti-cancerous final outline in tumors and cancer cell lines. So far, the purinergic system has been recognized as a potential therapeutic target in cancerous and tumoral ailments.

Targeting cancer stem cells from a metabolic perspective

The process of cancer development and progression is driven by distinct subsets of cancer stem cells (CSCs) that contribute the self-renewal capacity as the major impetus to the metastatic dissemination and main impediments in cancer treatment. Given that CSCs are so scarce in the tumor mass, there are debatable points on the metabolic signatures of CSCs. As opposed to differentiated tumor progenies, CSCs display exquisite patterns of metabolism that, depending on the type of cancer, predominately rely on glycolysis, oxidative metabolism of glutamine, fatty acids, or amino acids for ATP production. Metabolic heterogeneity of CSCs, which attributes to differences in type and microenvironment of tumors, confers CSCs to have the plasticity to cope with the endogenous mitochondrial stress and exogenous microenvironment. In essence, CSCs and normal stem cells are like mirror images of each other in terms of metabolism. To achieve reprogramming, CSCs not only need to upregulate their metabolic engine for self-renewal and defense mechanism, but also expedite the antioxidant defense to sustain the redox homeostasis. In the context of these pathways, this review portrays the connection between the metabolic features of CSCs and cancer stemness. Identification of the metabolic features in conferring resistance to anticancer treatment dictated by CSCs can enhance the opportunity to open up a new therapeutic dimension, which might not only improve the effectiveness of cancer therapies but also annihilate the whole tumor without recurrence. Henceforth, we highlight current findings of potential therapeutic targets for the design of alternative strategies to compromise the growth, drug resistance, and metastasis of CSCs by altering their metabolic phenotypes. Perturbing the versatile skills of CSCs by barricading metabolic signaling might bring about plentiful approaches to discover novel therapeutic targets for clinical application in cancer treatments.

Impact statement

This minireview highlights the current evidence on the mechanisms of pivotal metabolic pathways that attribute to cancer stem cells (CSCs) with a special focus on developing metabolic strategies of anticancer treatment that can be exploited in preclinical and clinical settings. Specific metabolic inhibitors that can overwhelm the properties of CSCs may impede tumor recurrence and metastasis, and potentially achieve a permanent cure of cancer patients.

Involvement of increased p53 expression in the decrease of mitochondrial DNA copy number and increase of SUVmax of FDG-PET scan in esophageal squamous cell carcinoma

We appraised Warburg effect through analysis of mitochondrial DNA (mtDNA) copy number and maximum standard uptake value (SUV_max) of ¹⁸F-fluorodeoxyglucose positron emission tomography (FDG-PET) scan and their alterations in esophageal squamous cell carcinoma (ESCC). Later T-status and longer longitudinal tumor length were associated with lower mtDNA^ESCC copy number (p < .05) but higher SUV_max-ESCC (p < .05), respectively. Lower mtDNA^ESCC copy number correlated with higher SUV_max-ESCC, reciprocally (p < .05). ESCCs expressing mutant p53 protein had lower mtDNA^ESCC copy number (p = .056) but higher SUV_max-ESCC (p = .046). We conclude that mutant p53 protein may be involved in the Warburg effect of ESCC.

Glucose transporter 1 regulates the proliferation and cisplatin sensitivity of esophageal cancer

Glucose transporter 1 (GLUT1) expression is a prognostic marker for esophageal squamous cell carcinoma (ESCC). Recent work on GLUT1 and development of specific inhibitors supports the feasibility of GLUT1 inhibition as a treatment for various cancers. The anti–proliferative effects of GLUT1‐specific small interfering RNA (siRNA) and a GLUT1 inhibitor were evaluated in ESCC cell lines. Expression of pro–proliferative and anti–proliferative signaling and effector molecules was examined by western blotting and quantitative RT‐PCR. GLUT1 expression in pretreatment clinical biopsy samples was measured by immunohistochemistry and correlated with various clinicopathological parameters and response to chemotherapy. The reduction in standardized uptake value (SUV) of ¹⁸F‐fluoro‐deoxyglucose was calculated using the formula: ([pretreatment SUV_max – posttreatment SUV_max]/pretreatment SUV_max) × 100. GLUT1‐specific siRNA expression in ESCC cells inhibited their proliferation, increased expression of p27kip, and decreased expression of cyclin‐dependent kinase 6, pyruvate kinase muscle isozyme M2, lactate dehydrogenase A and phospho‐ERK1/2. Suppression of GLUT1 by siRNA increased low‐dose cisplatin‐induced inhibition of proliferation of TE‐11 ESCC cells, which express high GLUT1 levels. Similarly, BAY‐876, a GLUT1 inhibitor, enhanced cisplatin‐mediated inhibition of ESCC cell proliferation. GLUT1 expression in pretreatment biopsy samples was associated with the response to chemotherapy as well as the pathological tumor stage and histological response grade after esophagectomy. Finally, GLUT1‐negative tumors showed a significantly larger reduction in SUV_max (61.2% ± 4.5%) compared with GLUT1‐positive tumors (46.2% ± 4.4%). GLUT1 expression may be a surrogate marker of response to chemotherapy, and inhibition of GLUT1 may be a potential novel therapy for ESCC patients.

Obesity and the Risk of Gastrointestinal Cancers

Obesity is a risk factor for all major gastrointestinal cancers. With the rapid increase in the prevalence of obesity worldwide, this link could lead to an elevated burden of cancers of the digestive system. Currently, three main mechanisms explaining the link between excess adiposity and gastrointestinal cancer risk are being considered, including altered insulin signaling, obesity-associated chronic low-grade inflammation, and altered sex hormone metabolism, although new potential mechanisms emerge. This review is aimed to present our current knowledge on biological mechanisms involved in adiposity-related gastrointestinal carcinogenesis supported by results collected in epidemiological studies.

Energy balance and gastrointestinal cancer: risk, interventions, outcomes and mechanisms

Obesity increases the risk of multiple gastrointestinal cancers and worsens disease outcomes. Conversely, strong inverse associations have emerged between physical activity and colon cancer and possibly other gastrointestinal malignancies. The effect of weight loss interventions - such as modifications of diet and/or physical activity or bariatric surgery - remains unclear in patients who are obese and have gastrointestinal cancer, although large clinical trials are underway. Human intervention studies have already shed light on potential mechanisms underlying the energy balance-cancer relationship, with preclinical models supporting emerging pathway effects. Central to interventions that reduce obesity or increase physical activity are pluripotent cancer-preventive effects (including reduced systemic and adipose tissue inflammation and angiogenesis, altered adipokine levels and improved insulin resistance) that directly interface with the hallmarks of cancer. Other mechanisms, such as DNA repair, oxidative stress and telomere length, immune function, effects on cancer stem cells and the microbiome, could also contribute to energy balance effects on gastrointestinal cancers. Although some mechanisms are well understood (for instance, systemic effects on inflammation and insulin signalling), other areas remain unclear. The current state of knowledge supports the need to better integrate mechanistic approaches with preclinical and human studies to develop effective, personalized diet and exercise interventions to reduce the burden of obesity on gastrointestinal cancer.

Human colorectal cancer initiation is bidirectional, and cell growth, metabolic genes and transporter genes are early drivers of tumorigenesis

The role of stem cells in the development of solid tumors remains controversial. In colorectal cancers (CRC), this is complicated by the conflicting "top-down" or "bottom-up" hypotheses of cancer initiation. We profiled the expressions of genes from the top (T) and bottom (B) crypt fractions of normal-appearing human colonic mucosa (M) at least 20 cm away from the tumor as a baseline and compared this to the genes of matched mucosa adjacent to tumors (M_T) in twenty-three sporadic CRC patients. In thirteen patients, the genetic distance (M-M_T) between the B fractions is smaller than the distance between the T fractions, indicating that the expressions diverge further in the top fractions (B < T). In the remaining patients, the reverse effect is observed (B > T). Assuming that a greater genetic divergence in the top or bottom fractions indicates that position as the initiation site, it is thus equally likely that human CRC initiates from 'top-down' via de-differentiated colonocytes or 'bottom-up' via dysregulated intestinal stem cells. Dysregulated genes that persist until tumor stage are not limited to tumor suppressors or oncogenes but include metabolic and transporter genes such as CA7, PHLPP2, and AQP8.

Nrf2 promotes oesophageal cancer cell proliferation via metabolic reprogramming and detoxification of reactive oxygen species

Cancer cells consume a large amount of energy and maintain high levels of anabolism to promote cell proliferation via metabolic reprogramming. Nuclear factor erythroid 2-related factor 2 (Nrf2; NFE2L2) is a master transcription regulator of stress responses and promotes metabolic reprogramming to support cell proliferation in various types of cancer. As oesophageal cancer is one of the most aggressive gastrointestinal cancers, we aimed to clarify the effect of Nrf2 on metabolic reprogramming in oesophageal cancer. The relationship between Nrf2 expression and clinical outcome was evaluated using a database comprising 201 oesophageal cancers. Using in vitro assays and metabolome analysis, we examined the mechanism by which Nrf2 affects malignant phenotype. High-level immunohistochemical expression of Nrf2 was significantly associated with poor recurrence-free survival (HR = 2.67, p = 0.0004) and overall survival (HR = 2.90, p < 0.0001) in oesophageal cancer patients. In an in vitro assay with siRNA in TE-11 cells, which showed high Nrf2 expression, Nrf2 depletion significantly decreased cell growth and enhanced G1 cell cycle arrest and apoptosis. In addition, reactive oxygen species (ROS) were not removed by detoxification via the Nrf2 pathway, with concomitant induction of the p38 mitogen-activated protein kinase pathway. The metabolome analysis showed that Nrf2 strongly promoted metabolic reprogramming to glutathione metabolism, which synthesizes the essential fuels for cancer progression. Furthermore, metabolome analysis using oesophageal cancer specimens confirmed that samples displaying high Nrf2 expression promoted glutathione synthesis. Metabolic reprogramming to glutathione metabolism, and ROS detoxification by activation of Nrf2, enhanced cancer progression and led to a poor clinical outcome in oesophageal cancer patients. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Cancer stem cell metabolism: a potential target for cancer therapy

Cancer Stem cells (CSCs) are a unipotent cell population present within the tumour cell mass. CSCs are known to be highly chemo-resistant, and in recent years, they have gained intense interest as key tumour initiating cells that may also play an integral role in tumour recurrence following chemotherapy. Cancer cells have the ability to alter their metabolism in order to fulfil bio-energetic and biosynthetic requirements. They are largely dependent on aerobic glycolysis for their energy production and also are associated with increased fatty acid synthesis and increased rates of glutamine utilisation. Emerging evidence has shown that therapeutic resistance to cancer treatment may arise due to dysregulation in glucose metabolism, fatty acid synthesis, and glutaminolysis. To propagate their lethal effects and maintain survival, tumour cells alter their metabolic requirements to ensure optimal nutrient use for their survival, evasion from host immune attack, and proliferation. It is now evident that cancer cells metabolise glutamine to grow rapidly because it provides the metabolic stimulus for required energy and precursors for synthesis of proteins, lipids, and nucleic acids. It can also regulate the activities of some of the signalling pathways that control the proliferation of cancer cells.

This review describes the key metabolic pathways required by CSCs to maintain a survival advantage and highlights how a combined approach of targeting cellular metabolism in conjunction with the use of chemotherapeutic drugs may provide a promising strategy to overcome therapeutic resistance and therefore aid in cancer therapy.

Pyruvate dehydrogenase kinase regulates hepatitis C virus replication

During replication, hepatitis C virus (HCV) utilizes macromolecules produced by its host cell. This process requires host cellular metabolic reprogramming to favor elevated levels of aerobic glycolysis. Therefore, we evaluated whether pyruvate dehydrogenase kinase (PDK), a mitochondrial enzyme that promotes aerobic glycolysis, can regulate HCV replication. Levels of c-Myc, hypoxia-inducible factor-1α (HIF-1α), PDK1, PDK3, glucokinase, and serine biosynthetic enzymes were compared between HCV-infected and uninfected human liver and Huh-7.5 cells infected with or without HCV. Protein and mRNA expression of c-Myc, HIF-1α, and glycolytic enzymes were significantly higher in HCV-infected human liver and hepatocytes than in uninfected controls. This increase was accompanied by upregulation of serine biosynthetic enzymes, suggesting cellular metabolism was altered toward facilitated nucleotide synthesis essential for HCV replication. JQ1, a c-Myc inhibitor, and dichloroacetate (DCA), a PDK inhibitor, decreased the expression of glycolytic and serine synthetic enzymes in HCV-infected hepatocytes, resulting in suppressed viral replication. Furthermore, when co-administered with IFN-α or ribavirin, DCA further inhibited viral replication. In summary, HCV reprograms host cell metabolism to favor glycolysis and serine biosynthesis; this is mediated, at least in part, by increased PDK activity, which provides a surplus of nucleotide precursors. Therefore, blocking PDK activity might have therapeutic benefits against HCV replication.

Long-term High Fat Ketogenic Diet Promotes Renal Tumor Growth in a Rat Model of Tuberous Sclerosis

Nutritional imbalance underlies many disease processes but can be very beneficial in certain cases; for instance, the antiepileptic action of a high fat and low carbohydrate ketogenic diet. Besides this therapeutic feature it is not clear how this abundant fat supply may affect homeostasis, leading to side effects. A ketogenic diet is used as anti-seizure therapy i.a. in tuberous sclerosis patients, but its impact on concomitant tumor growth is not known. To examine this we have evaluated the growth of renal lesions in Eker rats (Tsc2+/−) subjected to a ketogenic diet for 4, 6 and 8 months. In spite of existing opinions about the anticancer actions of a ketogenic diet, we have shown that this anti-seizure therapy, especially in its long term usage, leads to excessive tumor growth. Prolonged feeding of a ketogenic diet promotes the growth of renal tumors by recruiting ERK1/2 and mTOR which are associated with the accumulation of oleic acid and the overproduction of growth hormone. Simultaneously, we observed that Nrf2, p53 and 8-oxoguanine glycosylase α dependent antitumor mechanisms were launched by the ketogenic diet. However, the pro-cancerous mechanisms finally took the ascendency by boosting tumor growth.

MicroRNA-144 mediates metabolic shift in ovarian cancer cells by directly targeting Glut1

Warburg effect is characterized by an increased utilization of glucose via glycolysis in cancer cells, even when enough oxygen is present to properly respire. Recent studies demonstrate that deregulation of microRNAs contributes to the Warburg effect. In the present study, we show that miR-144 is downregulated while glucose transporter 1 (Glut1) is upregulated in ovarian cancers. In vitro studies further showed that miR-144 inhibits Glut1 expression through targeting its 3'-untranslated region. As a result, cells overexpressing miR-144 exhibited a metabolic shift, including enhanced glucose uptake and lactate production. The altered glucose metabolism induced by miR-144 also leads to a rapid growth of ovarian cancer cells. Taken together, our results indicate that miR-144 may serve as a molecular switch to regulate glycolysis in ovarian cancer by targeting the expression of Glut1.

Anti-Warburg effect of rosmarinic acid via miR-155 in gastric cancer cells

BACKGROUND

The Warburg effect refers to glycolytic production of adenosine triphosphate under aerobic conditions, and is a universal property of most cancer cells. Chronic inflammation is a key factor promoting the Warburg effect. This study aimed to determine whether rosmarinic acid (RA) has an anti-Warburg effect in gastric carcinoma in vitro and in vivo. The mechanism for the anti-Warburg effect was also investigated.

METHODS

An MTT assay was used to examine MKN45 cell growth in vitro. An enzyme-linked immunosorbent assay was used to detect proinflammatory cytokines. Real-time polymerase chain reaction was used to evaluate levels of microRNA expression in cells. Protein expression was determined by Western blotting assay. Mouse xenograft models were established using MKN45 cells to assess the anti-Warburg effect in gastric carcinoma in vivo.

RESULTS

RA suppressed glucose uptake and lactate production. It also inhibited expression of transcription factor hypoxia-inducible factor-1α, which affects the glycolytic pathway. Inflammation promoted the Warburg effect in cancer cells. As expected, RA inhibited proinflammatory cytokines and microRNAs related to inflammation, suggesting that RA may suppress the Warburg effect via an inflammatory pathway, such as that involving interleukin (IL)-6/signal transducer and activator of transcription-3 (STAT3). miR-155 was found to be an important mediator in the relationship between inflammation and tumorigenesis. We further showed that miR-155 was the target gene regulating the Warburg effect via inactivation of the IL-6/STAT3 pathway. Moreover, we found that RA suppressed the Warburg effect in vivo.

CONCLUSION

RA might potentially be a therapeutic agent for suppressing the Warburg effect in gastric carcinoma.

Mitochondrial uncoupling protein 2 and pancreatic cancer: A new potential target therapy

Overall 5-years survival of pancreatic cancer patients is nearly 5%, making this cancer type one of the most lethal neoplasia. Furthermore, the incidence rate of pancreatic cancer has a growing trend that determines a constant increase in the number of deceases caused by this pathology. The poor prognosis of pancreatic cancer is mainly caused by delayed diagnosis, early metastasis of tumor, and resistance to almost all tested cytotoxic drugs. In this respect, the identification of novel potential targets for new and efficient therapies should be strongly encouraged in order to improve the clinical management of pancreatic cancer. Some studies have shown that the mitochondrial uncoupling protein 2 (UCP2) is over-expressed in pancreatic cancer as compared to adjacent normal tissues. In addition, recent discoveries established a key role of UCP2 in protecting cancer cells from an excessive production of mitochondrial superoxide ions and in the promotion of cancer cell metabolic reprogramming, including aerobic glycolysis stimulation, promotion of cancer progression. These observations together with the demonstration that UCP2 repression can synergize with standard chemotherapy to inhibit pancreatic cancer cell growth provide the molecular rationale to consider UCP2 as a potential therapeutic target for pancreatic cancer. In this editorial, recent advances describing the relationship between cancer development and mitochondrial UCP2 activity are critically provided.

Ginsenoside 20(S)‑Rg3 inhibits the Warburg effect through STAT3 pathways in ovarian cancer cells

Cancer cells prefer to metabolize glucose through aerobic glycolysis, known as the Warburg effect. It plays a crucial role in proliferation and progression of cancer cells. However, the complete mechanism remains elusive. In recent studies, the signal transducer and activator of transcription 3 (STAT3) signaling has been discovered to have roles in cancer‑associated changes in metabolism. In this study, we find that the ginsenoside 20(S)‑Rg3, a pharmacologically active component of the traditional Chinese herb Panax ginseng, inhibits glycolysis in ovarian cancer cells by regulating hexokinase 2 (HK2) and pyruvate kinase M2 (PKM2). We also show that 20(S)‑Rg3 regulates HK2 through downregulation of p‑STAT3 (Tyr705). Furthermore, overexpression of STAT3 in ovarian cancer cells weakened the suppression of Warburg effect induced by 20(S)‑Rg3. Importantly, 20(S)‑Rg3 treatment represses HK2 expression in nude mouse xenograft models of ovarian cancer. Taken together, our results show that 20(S)‑Rg3 inhibits the Warburg effect by targeting STAT3/HK2 pathway in ovarian cancer cells, highlighting the potentiality of 20(S)‑Rg3 to be used as a therapeutic agent for ovarian cancer.