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.

CircFOXK2 promotes hepatocellular carcinoma progression and leads to a poor clinical prognosis via regulating the Warburg effect

BACKGROUND

The Warburg effect is well-established to be essential for tumor progression and accounts for the poor clinical outcomes of hepatocellular carcinoma (HCC) patients. An increasing body of literature suggests that circular RNAs (circRNAs) are important regulators for HCC. However, few circRNAs involved in the Warburg effect of HCC have hitherto been investigated. Herein, we aimed to explore the contribution of circFOXK2 to glucose metabolism reprogramming in HCC.

METHODS

In the present study, different primers were designed to identify 14 circRNAs originating from the FOXK2 gene, and their differential expression between HCC and adjacent liver tissues was screened. Ultimately, circFOXK2 (hsa_circ_0000817) was selected for further research. Next, the clinical significance of circFOXK2 was evaluated. We then assessed the pro-oncogenic activity of circFOXK2 and its impact on the Warburg effect in both HCC cell lines and animal xenografts. Finally, the molecular mechanisms of how circFOXK2 regulates the Warburg effect of HCC were explored.

RESULTS

CircFOXK2 was aberrantly upregulated in HCC tissues and positively correlated with poor clinical outcomes in patients that underwent radical hepatectomy. Silencing of circFOXK2 significantly suppressed HCC progression both in vitro and in vivo. Mechanistically, circFOXK2 upregulated the expression of protein FOXK2-142aa to promote LDHA phosphorylation and led to mitochondrial fission by regulating the miR-484/Fis1 pathway, ultimately activating the Warburg effect in HCC.

CONCLUSIONS

CircFOXK2 is a prognostic biomarker of HCC that promotes the Warburg effect by promoting the expression of proteins and miRNA sponges that lead to tumor progression. Overall, circFOXK2 has huge prospects as a potential therapeutic target for patients with HCC.

LOC101929709 promotes gastric cancer progression by aiding LIN28B to stabilize c-MYC mRNA

BACKGROUND

LIN28B plays a critical role in the Warburg effect. However, its underlying mechanism remains elusive. Recently, it has been reported that LIN28B could collaborate with IGF2BP3, which can bind to m6A-modified c-MYC transcripts. Therefore, this study investigated if LIN28B recognises methylated c-MYC mRNA to promote the Warburg effect in gastric cancer.

METHODS

Effects of LIN28B on gastric cancer were confirmed in vitro and in vivo. On the basis of bioinformatics analysis, the association between LIN28B and c-MYC mRNA was shown using RNA immunoprecipitation (RIP) and luciferase reporter assays. The role of m6A was identified by RNA pull-down assays. We further performed RIP-seq to search for long non-coding RNAs (lncRNAs) participating in the LIN28B binding process. Chromatin immunoprecipitation was used to show the impact of c-MYC on transcription of LIN28B and lncRNAs.

RESULTS

LIN28B was identified to stabilize c-MYC mRNA by recognizing m6A. Furthermore, the interaction between c-MYC mRNA and LIN28B is speculated to be supported by LOC101929709, which binds to both LIN28B and IGF2BP3. Functional experiments revealed that LOC101929709 promotes the proliferation, migration and glycolysis of gastric cancer. Mechanistically, LOC101929709 enriched in the cytoplasm helps LIN28B stabilize c-MYC mRNA. Moreover, c-MYC promoted the transcription of both LOC101929709 and LIN28B. Additionally, LOC101929709 also activated the PI3K/AKT pathway.

CONCLUSIONS

The c-MYC/LOC101929709/LIN28B axis promotes aerobic glycolysis and tumour progression. Thus, LOC101929709 can be a novel potential target for gastric cancer treatment.

Dihydroartemisinin inhibited the Warburg effect through YAP1/SLC2A1 pathway in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) was the third most common cause of cancer death. But it has only limited therapeutic options, aggressive nature, and very low overall survival. Dihydroartemisinin (DHA), an anti-malarial drug approved by the Food and Drug Administration (FDA), inhibited cell growth in HCC. The Warburg effect was one of the ten new hallmarks of cancer. Solute carrier family 2 member 1 (SLC2A1) was a crucial carrier for glucose to enter target cells in the Warburg effect. Yes-associated transcriptional regulator 1 (YAP1), an effector molecule of the hippo pathway, played a crucial role in promoting the development of HCC. This study sought to determine the role of DHA in the SLC2A1 mediated Warburg effect in HCC. In this study, DHA inhibited the Warburg effect and SLC2A1 in HepG2215 cells and mice with liver tumors in situ. Meanwhile, DHA inhibited YAP1 expression by inhibiting YAP1 promoter binding protein GA binding protein transcription factor subunit beta 1 (GABPB1) and cAMP responsive element binding protein 1 (CREB1). Further, YAP1 knockdown/knockout reduced the Warburg effect and SLC2A1 expression by shYAP1-HepG2215 cells and Yap1^LKO mice with liver tumors. Taken together, our data indicated that YAP1 knockdown/knockout reduced the SLC2A1 mediated Warburg effect by shYAP1-HepG2215 cells and Yap1^LKO mice with liver tumors induced by DEN/TCPOBOP. DHA, as a potential YAP1 inhibitor, suppressed the SLC2A1 mediated Warburg effect in HCC.

KAT2A affects tumor metabolic reprogramming in colon cancer progression through epigenetic activation of E2F1

Lysine acetyltransferase 2 A (KAT2A) has been implicated in tumorigenesis; nevertheless, the mechanism underlying its tumor-initiating effect remains elusive. In the present study, we aimed to identify the possible role of KAT2A in regulating metabolic reprogramming, a hallmark of cancer, in colon cancer (CC). KAT2A was found to be overexpressed in CC and correlated with metastases. KAT2A induced proliferation, migration, invasion, and epithelial-mesenchymal transition of CC cells, along with elevated cellular glycolytic capacity and mitochondrial stress. Functional enrichment analyses predicted and ChIP assays verified that KAT2A activated E2F transcription factor 1 (E2F1) by modifying the acetylation of H3K9. Rescue experiments revealed that E2F1 downregulation inhibited cellular activity, aerobic glycolysis and mitochondrial respiration in CC in the presence of KAT2A. Moreover, KAT2A/E2F1 promoted tumorigenic activity and lung metastases of CC cells in mice. Taken together, our findings demonstrate the substantial role of KAT2A in the modulation of post-translational modifications of E2F1 in CC, suggesting that knockdown of KAT2A may be a potential strategy for CC treatment.

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.

A small-molecule pan-class I glucose transporter inhibitor reduces cancer cell proliferation in vitro and tumor growth in vivo by targeting glucose-based metabolism

BACKGROUND

Cancer cells drastically increase the uptake of glucose and glucose metabolism by overexpressing class I glucose transporters (GLUT1-4) to meet their energy and biomass synthesis needs and are very sensitive and vulnerable to glucose deprivation. Although targeting glucose uptake via GLUTs has been an attractive anticancer strategy, the relative anticancer efficacy of multi-GLUT targeting or single GLUT targeting is unclear. Here, we report DRB18, a synthetic small molecule, is a potent anticancer compound whose pan-class I GLUT inhibition is superior to single GLUT targeting.

METHODS

Glucose uptake and MTT/resazurin assays were used to measure DRB18's inhibitory activities of glucose transport and cell viability/proliferation in human lung cancer and other cancer cell lines. Four HEK293 cell lines expressing GLUT1-4 individually were used to determine the IC₅₀ values of DRB18's inhibitory activity of glucose transport. Docking studies were performed to investigate the potential direct interaction of DRB18 with GLUT1-4. Metabolomics analysis was performed to identify metabolite changes in A549 lung cancer cells treated with DRB18. DRB18 was used to treat A549 tumor-bearing nude mice. The GLUT1 gene was knocked out to determine how the KO of the gene affected tumor growth.

RESULTS

DRB18 reduced glucose uptake mediated via each of GLUT1-4 with different IC₅₀s, which match with the docking glidescores with a correlation coefficient of 0.858. Metabolomics analysis revealed that DRB18 altered energy-related metabolism in A549 cells by changing the abundance of metabolites in glucose-related pathways in vitro and in vivo. DRB18 eventually led to G1/S phase arrest and increased oxidative stress and necrotic cell death. IP injection of DRB18 in A549 tumor-bearing nude mice at 10 mg/kg body weight thrice a week led to a significant reduction in the tumor volume compared with mock-treated tumors. In contrast, the knockout of the GLUT1 gene did not reduce tumor volume.

CONCLUSIONS

DRB18 is a potent pan-class I GLUT inhibitor in vitro and in vivo in cancer cells. Mechanistically, it is likely to bind the outward open conformation of GLUT1-4, reducing tumor growth through inhibiting GLUT1-4-mediated glucose transport and metabolisms. Pan-class I GLUT inhibition is a better strategy than single GLUT targeting for inhibiting tumor growth.

Low concentrations of FA exhibits the Hormesis effect by affecting cell division and the Warburg effect

Formaldehyde (FA), a ubiquitous indoor environmental pollutant, has been classified as a carcinogen. There are many studies showed that low levels of FA could promote cell proliferation, however, little is known about the signal pathways. To determine the potential molecular mechanisms, human chronic myeloid leukemia cells (K562 cells) and human bronchial epithelial cells (16HBE cells) were exposed to different concentrations of FA. The data showed that FA at 0-125 μM or 0-60 μM promoted the proliferation of K562 cells or 16HBE cells respectively, indicating that FA did have the Hormesis effect. FA at 75 μM (K562 cells) and 40 μM (16HBE cells) significantly promoted cell proliferation, increased intracellular reactive oxygen species (ROS) levels, and decreased glutathione (GSH) content. At the same time, FA treatment induced a marked increase in the key molecules of cell division like CyclinD-cdk4 and E2F1. In addition, pyruvate kinase isozyme M2 (PKM2), glucose, glucose transporter 1 (GLUT1), lactic acid and lactate dehydrogenase A (LDHA) content in the Warburg effect were increased. Administering Vitamin E (VE), significantly disrupted cell division and disturbed the Warburg effect, effectively indicating the decrease of cell activity. Conclusively, these findings suggested that low concentrations of FA could promote cell proliferation by accelerating cell division process or enhancing the Warburg effect to embody the Hormesis effect.

Transcriptional activation of SIRT6 via FKHRL1/FOXO3a inhibits the Warburg effect in glioblastoma cells

Glioblastoma (GBM) is the most aggressive and malignant form of brain tumors. However, its molecular mechanisms of tumorigenesis and cancer development remains to elucidate. Here, we reported FKHRL1, also called as FOXO3a, was an anti-cancer factor that inhibited the Warburg effect in GBM. Clinical data analysis revealed that FKHRL1 expression was positively correlated with the prognosis of patients with GBM. FKHRL1 silencing promoted glycolysis and cell growth of HEB gliocytes. Besides, FKHRL1 expression was tightly correlated with the expression of SIRT6 and a cluster of glycolytic genes that controlling the Warburg effect in glioma samples. Interestingly, the expression of SIRT6 was reduced after FKHRL1 knockdown, while its expression was upregulated when FKHRL1 was overexpressed in human U251 GBM cell line. In addition, SIRT6 restoration recovered the upregulated aerobic glycolysis induced by FKHRL1 knockdown. Meanwhile, SIRT6 knockdown also rescued the decrease of glucose metabolism induced by FKHRL1 overexpression. Luciferase assay and chromatin immunoprecipitation (ChIP) assay revealed that FKHRL1 bound to the promoter region of SIRT6 and enhanced its expression. Both in vitro and in vivo experiments further confirmed that FKHRL1-SIRT6 axis played a pivotal role in cell metabolism and tumor growth. Our results indicate that FKHRL1-SIRT6 axis regulates cell metabolism and may provide clues for GBM treatment.

The Warburg effect in human pancreatic cancer cells triggers cachexia in athymic mice carrying the cancer cells

Background

Cancer cachexia is a cancer-induced metabolic disorder and a major cause of cancer-induced death. The constituents of cancer cachexia include an increase in energy expenditure, hepatic gluconeogenesis, fat lipolysis, and skeletal-muscle proteolysis and a decrease in body weight. The aetiology of cancer cachexia is unclear and may involve cancer-cell metabolism and secretion. In this study, we investigated whether the high glycolysis in cancer cells (the Warburg effect) triggers cachexia in athymic mice carrying pancreatic cancer cells.

Methods

First, we examined five human pancreatic cancer cell lines for glycolysis and cachectic-cytokine secretion. Consequently, MiaPaCa2 and AsPC1 cells were selected for the present study, because the glycolysis in MiaPaCa2 cells was typically high and that in AsPC1 cells was exceptionally low. In addition, both MiaPaCa2 and AsPC1 cells were competent in the secretion of examined cytokines. Next, we transplanted MiaPaCa2 and AsPC1 cells subcutaneously in different athymic mice for 8 weeks, using intact athymic mice for control. In another experiment, we treated normal mice with the supernatants of MiaPaCa2 or AsPC1 cells for 7 days, using vehicle-treated mice for control. In both models, we measured food intake and body weight, assayed plasma glucose, triglycerides, and TNF-α and used Western blot to determine the proteins that regulated hepatic gluconeogenesis, fat lipolysis, and skeletal-muscle proteolysis in the corresponding tissues. We also studied the effect of MiaPaCa2-cell supernatants on the proteolysis of C2C12 skeletal-muscle cells in vitro.

Results

The athymic mice carrying high-glycolytic MiaPaCa2 cells had anorexia and also showed evidence for cachexia, including increased hepatic gluconeogenesis, fat lipolysis and skeletal-muscle proteolysis and decreased body weight. The athymic mice carrying low-glycolytic AsPC1 cells had anorexia but did not show the above-mentioned evidence for cachexia. When normal mice were treated with the supernatants of MiaPaCa2 or AsPC1 cells, their energy homeostasis was largely normal. Thus, the cachexia in the athymic mice carrying MiaPaCa2 cells may not result from humeral factors released by the cancer cells. In vitro, MiaPaCa2-cell supernatants did not induce proteolysis in C2C12 cells.

Conclusion

The Warburg effect in pancreatic cancer cells is an independent aetiological factor for pancreatic cancer-induced cachexia.

Interdependence of GLO I and PKM2 in the Metabolic shift to escape apoptosis in GLO I-dependent cancer cells

Many cancer cells undergo metabolic reprogramming known as the Warburg effect, which is characterized by a greater dependence on glycolysis for ATP generation, even under normoxic conditions. Glyoxalase I (GLO I) is a rate-limiting enzyme involved in the detoxification of cytotoxic methylglyoxal formed in glycolysis and which is known to be highly expressed in many cancer cells. Thus, specific inhibitors of GLO I are expected to be effective anticancer drugs. We previously discovered a novel GLO I inhibitor named TLSC702. Although the strong inhibitory activity of TLSC702 was observed in the in vitro enzyme assay, higher concentrations were required to induce apoptosis at the cellular level. One of the proposed reasons for this difference is that cancer cells alter the energy metabolism leading them to become more dependent on mitochondrial respiration than glycolysis (Metabolic shift) to avoid apoptosis induction. Thus, we assumed that combination of TLSC702 with shikonin-a specific inhibitor of pyruvate kinase M2 (PKM2) that acts as a driver of TCA cycle by supplying pyruvate and which is known to be specifically expressed in cancer cells-would have anticancer effects. We herein show the anticancer effects of combination treatment with TLSC702 and shikonin, and a possible anticancer mechanism.

PKM2 promotes reductive glutamine metabolism

Objective:

Pyruvate kinases M (PKM), including the PKM1 and PKM2 isoforms, are critical factors in glucose metabolism. PKM2 promotes aerobic glycolysis, a phenomenon known as " the Warburg effect”. The purpose of this study was to identify the roles of PKM2 in regulating cellular metabolism.

Methods:

The CRISPR/Cas9 system was used to generate the PKM-knockout cell model to evaluate the role of PKM in cellular metabolism. Lactate levels were measured by the Vitros LAC slide method on an autoanalyzer and glucose levels were measured by the autoanalyzer AU5800. The metabolism of ¹³C₆-glucose or ¹³C₅-glutamine was evaluated by liquid chromatography/mass spectrometry analyses. The effects of PKM on tumor growth were detected in vivo in a tumor-bearing mouse model.

Results:

We found that both PKM1 and PKM2 enabled aerobic glycolysis, but PKM2 converted glucose to lactate much more efficiently than PKM1. As a result, PKM2 reduced glucose levels reserved for intracellular utilization, particularly for the production of citrate, and thus increased the α-ketoglutarate/citrate ratio to promote the generation of glutamine-derived acetyl-coenzyme A through the reductive pathway. Furthermore, reductive glutamine metabolism facilitated cell proliferation under hypoxia conditions, which supports in vivo tumor growth. In addition, PKM-deletion induced a reverse Warburg effect in tumor-associated stromal cells.

Conclusions:

PKM2 plays a critical role in promoting reductive glutamine metabolism and maintaining proton homeostasis. This study is helpful to increase the understanding of the physiological role of PKM2 in cancer cells.

Targeting aberrant cancer metabolism - The role of sirtuins

Cancer cells, as opposed to normal cells, generate energy by increasing aerobic glycolysis, which is a phenomenon called "the Warburg effect". An altered energy metabolism supporting continuous cell growth and proliferation was pointed to as the new "hallmark" of cancer cells. Several hypotheses have been proposed to explain the maintenance of this seemingly wasteful catabolic state. The epigenetic mechanisms which depend on the covalent modifications of both DNA and histones have recently emerged as important players in the regulation of glucose metabolism. The sirtuin family of histone deacetylases has emerged as important regulators of diverse physiological and pathological events, including cancer metabolism. Sirtuins 1-7 (SIRT1-7) belong to class III of histone deacetylase enzymes which are dependent on NAD(+) for activity. It was recently demonstrated that SIRT6 is a tumor suppressor that modulates aerobic glycolysis by repressing HIF1 transcription. Members of this family of enzymes are considered promising pharmaceutical targets for cancer treatment. This review highlights the major functions of sirtuins in relation to cancer metabolism and the possibilities of their activation and inhibition by small molecule drugs.

Regulation and function of pyruvate kinase M2 in cancer

Altered metabolism is fundamental to the growth and survival of cancer cells. Pyruvate kinase M2 (PKM2), a key enzyme in cancer metabolism, has been demonstrated to play a central role not only in metabolic reprogramming but also in direct regulation of gene expression and subsequent cell cycle progression. This review outlines the current understanding of PKM2 protein kinase activity and regulatory mechanisms underlying PKM2 expression, enzymatic activity, and nuclear localization, thus highlighting PKM2 as a potential therapeutic target.