Dysregulated glycolysis as an oncogenic event

Mechanism study of lncRNA RMRP regulating esophageal squamous cell carcinoma through miR-580-3p/ATP13A3 axis

OBJECTIVE

It is well-known that lncRNAs regulate energy metabolism in tumors. This study focused on the action of RMRP on esophageal squamous cell carcinoma (ESCC) cell proliferation, apoptosis, and glycolysis.

METHODS

In the resected ESCC tissues and adjacent tissues from patients, RMRP/miR-580-3p/ATP13A3 expressions were evaluated. ESCC cell proliferation rates and apoptotic rates were measured by CCK-8 and flow cytometry, respectively. Apoptosis related markers were examined by Western blot. Moreover, glucose uptake, lactic acid, and ATP were measured by commercial kits, whereas HK2 and PKM2 were evaluated by Western blot to study ESCC cell glycolysis. Finally, the editing program of RMRP/miR-580-3p/ATP13A3 was translated by luciferase reporter assay and RIP analysis.

RESULTS

RMRP and ATP13A3 were induced, while miR-580-3p was reduced in their expression in ESCC tissues. Silencing RMRP reduced proliferation, glycolysis, and anti-apoptosis ability of ESCC cells. RMRP sequestered miR-580-3p to target ATP13A3. Silenced ATP13A3 or overexpressed miR-580-3p rescued overexpressed RMRP-mediated promotion of proliferation, glycolysis, and anti-apoptosis of ESCC cells.

CONCLUSION

RMRP accelerates ESCC progression through the miR-580-3p/ATP13A3 axis, renewing a reference for lncRNA-based therapies for tumors.

The transcription factor ChREBP Orchestrates liver carcinogenesis by coordinating the PI3K/AKT signaling and cancer metabolism

Cancer cells integrate multiple biosynthetic demands to drive unrestricted proliferation. How these cellular processes crosstalk to fuel cancer cell growth is still not fully understood. Here, we uncover the mechanisms by which the transcription factor Carbohydrate responsive element binding protein (ChREBP) functions as an oncogene during hepatocellular carcinoma (HCC) development. Mechanistically, ChREBP triggers the expression of the PI3K regulatory subunit p85α, to sustain the activity of the pro-oncogenic PI3K/AKT signaling pathway in HCC. In parallel, increased ChREBP activity reroutes glucose and glutamine metabolic fluxes into fatty acid and nucleic acid synthesis to support PI3K/AKT-mediated HCC growth. Thus, HCC cells have a ChREBP-driven circuitry that ensures balanced coordination between PI3K/AKT signaling and appropriate cell anabolism to support HCC development. Finally, pharmacological inhibition of ChREBP by SBI-993 significantly suppresses in vivo HCC tumor growth. Overall, we show that targeting ChREBP with specific inhibitors provides an attractive therapeutic window for HCC treatment.

Metabolism-regulating non-coding RNAs in breast cancer: roles, mechanisms and clinical applications

Breast cancer is one of the most common malignancies that pose a serious threat to women's health. Reprogramming of energy metabolism is a major feature of the malignant transformation of breast cancer. Compared to normal cells, tumor cells reprogram metabolic processes more efficiently, converting nutrient supplies into glucose, amino acid and lipid required for malignant proliferation and progression. Non-coding RNAs(ncRNAs) are a class of functional RNA molecules that are not translated into proteins but regulate the expression of target genes. NcRNAs have been demonstrated to be involved in various aspects of energy metabolism, including glycolysis, glutaminolysis, and fatty acid synthesis. This review focuses on the metabolic regulatory mechanisms and clinical applications of metabolism-regulating ncRNAs involved in breast cancer. We summarize the vital roles played by metabolism-regulating ncRNAs for endocrine therapy, targeted therapy, chemotherapy, immunotherapy, and radiotherapy resistance in breast cancer, as well as their potential as therapeutic targets and biomarkers. Difficulties and perspectives of current targeted metabolism and non-coding RNA therapeutic strategies are discussed.

PIM2 Promotes the Development of Ovarian Endometriosis by Enhancing Glycolysis and Fibrosis

Endometriosis is a common gynecological disorder characterized by the presence of the endometrial glands and the stroma outside the uterine cavity. The disease affects reproductive function and quality of life in women of reproductive age. Endometriosis is similar to tumors in some characteristics, such as glycolysis. PIM2 can promote the development of tumors, but the mechanism of PIM2 in endometriosis is still unclear. Therefore, our goal is to study the mechanism of PIM2 in endometriosis. Through immunohistochemistry, we found PIM2, HK2, PKM2, SMH (smooth muscle myosin heavy chain), Desmin, and α-SMA (α-smooth muscle actin) were strongly expressed in the ovarian endometriosis. In endometriotic cells, PIM2 enhanced glycolysis and fibrosis via upregulating the expression of PKM2. Moreover, the PIM2 inhibitor SMI-4a inhibited the development of endometriosis. And we established a PIM2 knockout mouse model of endometriosis to demonstrate the role of PIM2 in vivo. In summary, our study indicates that PIM2 promotes the development of endometriosis. PIM2 may serve as a promising therapeutic target for endometriosis.

Sp1 promotes tumour progression by remodelling the mitochondrial network in cervical cancer

BACKGROUND

Cervical cancer remains one of the most prevalent cancers worldwide. Accumulating evidence suggests that specificity protein 1 (Sp1) plays a pivotal role in tumour progression. The underlying role and mechanism of Sp1 in tumour progression remain unclear.

METHODS

The protein level of Sp1 in tumour tissues was determined by immunohistochemistry. The effect of Sp1 expression on the biological characteristics of cervical cancer cells was assessed by colony, wound healing, transwell formation, EdU, and TUNEL assays. Finally, the underlying mechanisms and effects of Sp1 on the mitochondrial network and metabolism of cervical cancer were analysed both in vitro and in vivo.

RESULTS

Sp1 expression was upregulated in cervical cancer. Sp1 knockdown suppressed cell proliferation both in vitro and in vivo, while overexpression of Sp1 had the opposite effects. Mechanistically, Sp1 facilitated mitochondrial remodelling by regulating mitofusin 1/2 (Mfn1/2), OPA1 mitochondrial dynamin-like GTPase (Opa1), and dynamin 1-like (Drp1). Additionally, the Sp1-mediated reprogramming of glucose metabolism played a critical role in the progression of cervical cancer cells.

CONCLUSIONS

Our study demonstrates that Sp1 plays a vital role in cervical tumorigenesis by regulating the mitochondrial network and reprogramming glucose metabolism. Targeting Sp1 could be an effective strategy for the treatment of cervical cancer.

The functions and molecular mechanisms of Tribbles homolog 3 (TRIB3) implicated in the pathophysiology of cancer

Currently, cancer ranks as the second leading cause of death worldwide, and at the same time, the burden of cancer continues to increase. The underlying molecular pathways involved in the initiation and development of cancer are the subject of considerable research worldwide. Further understanding of these pathways may lead to new cancer treatments. Growing data suggest that Tribble's homolog 3 (TRIB3) is essential in oncogenesis in many types of cancer. The mammalian tribbles family's proteins regulate various cellular and physiological functions, such as the cell cycle, stress response, signal transduction, propagation, development, differentiation, immunity, inflammatory processes, and metabolism. To exert their activities, Tribbles proteins must alter key signaling pathways, including the mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3 kinase (PI3K)/AKT pathways. Recent evidence supports that TRIB3 dysregulation has been linked to various diseases, including tumor development and chemoresistance. It has been speculated that TRIB3 may either promote or inhibit the onset and development of cancer. However, it is still unclear how TRIB3 performs this dual function in cancer. In this review, we present and discuss the most recent data on the role of TRIB3 in cancer pathophysiology and chemoresistance. Furthermore, we describe in detail the molecular mechanism TRIB3 regulates in cancer.

Circular RNAs: Emerging regulators of glucose metabolism in cancer

Aberrant glucose metabolism is one of the most striking characteristics of metabolic reprogramming in cancer. Thus, clarifying the regulatory mechanism of glucose metabolism is crucial to understanding tumor progression and developing novel therapeutic strategies for cancer patients. Recent developments in circular RNAs have explained the regulatory mechanism of glucose metabolism from a new dimension. In this review, we briefly summarize the recent advances in circRNA research on cancer glucose metabolism and emphasize the different regulatory mechanisms, including acting as miRNA sponges, interacting with proteins and being translated into proteins. Additionally, we discuss the future research directions of circular RNAs in the field of glucose metabolism.

Reprogramming of glycolysis by chemical carcinogens during tumor development

Indiscriminate usage and mismanagement of chemicals in the agricultural and industrial sectors have contaminated different environmental compartments. Exposure to these persistent and hazardous pollutants like heavy metals, endocrine disruptors, aromatic hydrocarbons, and pesticides can result in various health adversities, including cancer. Chemical carcinogens follow a similar pattern of carcinogenesis, like oxidative stress, chromosomal aberration, DNA double-strand break, mismatch repair, and misregulation of oncogenic and/or tumor suppressors. Out of several cancer-associated endpoints, cellular metabolic homeostasis is the commonest to be deregulated upon chemical exposure. Chemical carcinogens hamper glycolytic reprogramming to fuel the malignant transformation of the cells and/or promote cancer progression. Several regulators like Akt, ERK, Ras, c-Myc, HIF-1α, and p53 regulate glycolysis in chemical-induced carcinogenesis. However, the deregulation of the anabolic biochemistry of glucose during chemical-induced carcinogenesis remains to be uncovered. This review comprehensively covers the environmental chemical-induced glycolytic shift during carcinogenesis and its mechanism. The focus is also to fill the major gaps associated with understanding the fairy tale between environmental carcinogens and metabolic reprogramming. Although evidence from studies regarding glycolytic reprogramming in chemical carcinogenesis provides valuable insights into cancer therapy, exposure to a mixture of toxicants and their mechanism of inducing carcinogenesis still needs to be studied.

Metabolic Pathways, Enzymes, and Metabolites: Opportunities in Cancer Therapy

Metabolic reprogramming enables cancer cells to proliferate and produce tumor biomass under a nutrient-deficient microenvironment and the stress of metabolic waste. A cancer cell adeptly undergoes a variety of adaptations in metabolic pathways and differential expression of metabolic enzyme genes. Metabolic adaptation is mainly determined by the physiological demands of the cancer cell of origin and the host tissue. Numerous metabolic regulators that assist cancer cell proliferation include uncontrolled anabolism/catabolism of glucose metabolism, fatty acids, amino acids metabolism, nucleotide metabolism, tumor suppressor genes, microRNAs, and many regulatory enzymes and genes. Using this paradigm, we review the current understanding of metabolic reprogramming in tumors and discuss the new strategies of cancer metabolomics that can be tapped into for cancer therapeutics.

Long non-coding RNA VAL facilitates PKM2 enzymatic activity to promote glycolysis and malignancy of gastric cancer

BACKGROUND

Gastric cancer (GC) is one of the most common types of cancer worldwide, which leads to more than 10% of cancer-related deaths. Metabolism reprogramming presents as a pivotal event in cancer initiation and progression through enhancing aerobic glycolysis and anabolic metabolism. However, the underlying regulatory mechanisms in GC remain unknown.

METHODS

VAL was identified by bioinformatics analyses in GC. Cell-based assays and mouse model illustrate the role of VAL in GC. RNA pull-down, immunoprecipitation assay and Western blot elucidate the interaction between VAL and PKM2. Pyruvate kinase activity, ECAR and OCR were measured to validate aerobic glycolysis of GC cells.

RESULTS

Long non-coding RNA (lncRNA) VAL is significantly upregulated in GCs and indicates poor prognosis. Functional assays showed that VAL promotes GC malignant progression. Mechanistically, VAL strengthens the enzymatic activity of PKM2 and aerobic glycolysis of GC cells through directly binding with PKM2 to abrogate the PKM2-Parkin interaction, and to suppress Parkin-induced polyubiquitination of PKM2. In addition, glucose starvation induces VAL expression to enhance this process.

CONCLUSIONS

Our study provides an insight into an lncRNA-dependent regulation on the enzymatic activity of PKM2, and suggests a potential of targeting VAL or PKM2 as promising biomarkers in GC diagnosis and treatment.

Mitochondrial fragmentation in liver cancer: Emerging player and promising therapeutic opportunities

Hepatocellular carcinoma (HCC) is the leading cause of cancer-related death worldwide. Enhanced mitochondrial fragmentation (MF) is associated with poor prognosis in HCC patients. However, its molecular mechanism in HCC remains elusive. Although enhanced MF activates effector T cells and dendritic cells, it induces immunoescape by decreasing the number and cytotoxicity of natural killer cells in the HCC immune microenvironment. Therefore, the influence of MF on the activity of different immune cells is a great challenge. Enhanced MF contributes to maintaining stemness by promoting the asymmetric division of liver cancer stem cells (LCSCs), suggesting that MF may become a potential target for HCC recurrence, metastasis, and chemotherapy resistance. Moreover, mechanistic studies suggest that MF may promote tumour progression through autophagy, oxidative stress, and metabolic reprogramming. Human-induced hepatocyte organoids are a recently developed system that can be genetically manipulated to mimic cancer initiation and identify potential preventive treatments. We can use it to screen MF-related candidate inhibitors of HCC progression and further explore the role of MF in hepatocarcinogenesis. We herein describe the mechanisms by which MF contributes to HCC development, discuss potential therapeutic approaches, and highlight the possibility that MF modulation has a synergistic effect with immunotherapy.

Revisited Metabolic Control and Reprogramming Cancers by Means of the Warburg Effect in Tumor Cells

Aerobic glycolysis is an emerging hallmark of many human cancers, as cancer cells are defined as a “metabolically abnormal system”. Carbohydrates are metabolically reprogrammed by its metabolizing and catabolizing enzymes in such abnormal cancer cells. Normal cells acquire their energy from oxidative phosphorylation, while cancer cells acquire their energy from oxidative glycolysis, known as the “Warburg effect”. Energy–metabolic differences are easily found in the growth, invasion, immune escape and anti-tumor drug resistance of cancer cells. The glycolysis pathway is carried out in multiple enzymatic steps and yields two pyruvate molecules from one glucose (Glc) molecule by orchestral reaction of enzymes. Uncontrolled glycolysis or abnormally activated glycolysis is easily observed in the metabolism of cancer cells with enhanced levels of glycolytic proteins and enzymatic activities. In the “Warburg effect”, tumor cells utilize energy supplied from lactic acid-based fermentative glycolysis operated by glycolysis-specific enzymes of hexokinase (HK), keto-HK-A, Glc-6-phosphate isomerase, 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase, phosphofructokinase (PFK), phosphor-Glc isomerase (PGI), fructose-bisphosphate aldolase, phosphoglycerate (PG) kinase (PGK)1, triose phosphate isomerase, PG mutase (PGAM), glyceraldehyde-3-phosphate dehydrogenase, enolase, pyruvate kinase isozyme type M2 (PKM2), pyruvate dehydrogenase (PDH), PDH kinase and lactate dehydrogenase. They are related to glycolytic flux. The key enzymes involved in glycolysis are directly linked to oncogenesis and drug resistance. Among the metabolic enzymes, PKM2, PGK1, HK, keto-HK-A and nucleoside diphosphate kinase also have protein kinase activities. Because glycolysis-generated energy is not enough, the cancer cell-favored glycolysis to produce low ATP level seems to be non-efficient for cancer growth and self-protection. Thus, the Warburg effect is still an attractive phenomenon to understand the metabolic glycolysis favored in cancer. If the basic properties of the Warburg effect, including genetic mutations and signaling shifts are considered, anti-cancer therapeutic targets can be raised. Specific therapeutics targeting metabolic enzymes in aerobic glycolysis and hypoxic microenvironments have been developed to kill tumor cells. The present review deals with the tumor-specific Warburg effect with the revisited viewpoint of recent progress.

The emerging role of noncoding RNAs in the Hedgehog signaling pathway in cancer

Hedgehog (HH), a conserved signaling pathway, is involved in embryo development, organogenesis, and other biological functions. Dysregulation and abnormal activation of HH are involved in tumorigenesis and tumor progression. With the emergence of interest in noncoding RNAs, studies on their involvement in abnormal regulation of biological processes in tumors have been published one after another. In this review, we focus on the crosstalk between noncoding RNAs and the HH pathway in tumors and elaborate the mechanisms by which long noncoding RNAs and microRNAs regulate or are regulated by HH signaling in cancer. We also discuss the interaction between noncoding RNAs and the HH pathway from the perspective of cancer hallmarks, presenting this complex network as concisely as possible and organizing ideas for cancer diagnosis and treatment.

Riluzole regulates pancreatic cancer cell metabolism by suppressing the Wnt-β-catenin pathway

Most cancer cells rely on aerobic glycolysis to support uncontrolled proliferation and evade apoptosis. However, pancreatic cancer cells switch to glutamine metabolism to survive under hypoxic conditions. Activation of the Wnt/β-catenin pathway induces aerobic glycolysis by activating enzymes required for glucose metabolism and regulating the expression of glutamate transporter and glutamine synthetase. The results demonstrate that riluzole inhibits pancreatic cancer cell growth and has no effect on human pancreatic normal ductal epithelial cells. RNA-seq experiments identified the involvement of Wnt and metabolic pathways by riluzole. Inhibition of Wnt-β-catenin/TCF-LEF pathway by riluzole suppresses the expression of PDK, MCT1, cMyc, AXIN, and CyclinD1. Riluzole inhibits glucose transporter 2 expression, glucose uptake, lactate dehydrogenase A expression, and NAD + level. Furthermore, riluzole inhibits glutamate release and glutathione levels, and elevates reactive oxygen species. Riluzole disrupts mitochondrial homeostasis by inhibiting Bcl-2 and upregulating Bax expression, resulting in a drop of mitochondrial membrane potential. Finally, riluzole inhibits pancreatic cancer growth in KPC (Pdx1-Cre, LSL-Trp53R172H, and LSL-KrasG12D) mice. In conclusion, riluzole can inhibit pancreatic cancer growth by regulating glucose and glutamine metabolisms and can be used to treat pancreatic cancer.

Decabromodiphenyl ether induces male reproductive toxicity by activating mitochondrial apoptotic pathway through glycolipid metabolism dysbiosis

Decabromodiphenyl ether (BDE-209), an extensively used flame retardant, exists widely in the environment. Although male reproductive toxicity induced by BDE-209 has been reported, its mechanisms remain unclear. To explore the role of glycolipid metabolism in male reproductive toxicity and the potential mechanisms, forty male SD rats were divided into four groups and given gavage with BDE-209 at 0, 5, 50, and 500 mg/kg/d for 28 days. In vitro, the spermatogenic cell lines GC-2spd cells were divided into four groups: the control group, 32 μg/mL BDE-209 group, 32 μg/mL BDE-209 + 0.4 μM Fatostatin (the inhibitor of SREBP-1) group, and 0.4 μM Fatostatin group. Our results showed that BDE-209 decreased sperm quality and quantity, which was correlated with glycolipid metabolism dysbiosis of testis. The levels of glucose, triglyceride, and total cholesterol were negatively correlated with sperm concentration, and triglyceride and total cholesterol levels were negatively correlated with sperm motility, while positively correlated with the sperm malformation rate. Moreover, BDE-209 exposure activated the glycolipid metabolism pathways (PPARγ/RXRα/SCAP/SREBP-1) and mitochondrial apoptotic pathway, thereby inducing the apoptosis of spermatogenic cells. In vitro, BDE-209 caused triglyceride and total cholesterol disorder and apoptosis of GC-2spd cells, the lipid metabolism pathways inhibitor fatostain downregulated the elevation of triglyceride and total cholesterol concentrations, and suppressed apoptosis and the activation of the mitochondrial apoptotic pathway in GC-2spd cells caused by BDE-209. Our results indicated that BDE-209 induced male reproductive toxicity by causing glycolipid metabolism dysbiosis of testis resulting in activating of the mitochondrial apoptotic pathway in spermatogenic cells. The study provides new insight into the mechanisms of male reproductive toxicity caused by BDE-209.

BORIS/CTCFL expression activates the TGFβ signaling cascade and induces Drp1 mediated mitochondrial fission in neuroblastoma

The cancer-testis antigen CTCFL/BORIS (Brother of Regulator of Imprinted Sites) also known, as a paralog of CTCF -the "master weaver of the genome" is a key transcriptional regulator. Both CTCF and BORIS can bind to the same promoter sequence and recruit diverse proteins. BORIS is also known to be associated with actively translating ribosomes suggesting new roles of BORIS in gene expression. Various studies have attempted to elucidate the role of BORIS in different cell types for the development of targeted therapy depending on molecular signatures and genetic aberrations associated with the disease type. The current study is focused on its role in neuroblastoma. Here, we have deciphered the role of BORIS on TGFβ1 pathway which is highly affected by embryonic CTCFL expression. BORIS stabilized the SMAD3 and SMAD4 transcripts leading to prolonged TGFβ activation. Further, loss of BORIS abrogated both the canonical and non-canonical TGFβ signaling suggesting the dependency of TGFβ on BORIS. The effect on the metabolic profile of the neuroblastoma cells were analyzed with change in BORIS expression levels. Also, ectopic expression of BORIS leads to Drp1 phosphorylation (Ser616) enhancing mitochondrial fission followed by a switch in cellular metabolism towards glycolysis. This cellular metabolism switch was in turn supported with a reduction in oxygen consumption rate upon BORIS expression. Interestingly methylome analysis revealed patterns of global histone methylation, a mechanism that regulate important signaling pathways in neuroblastoma. This study analyzes the consequence of BORIS expression in neuroblastoma cells and thereby elucidate its downstream targets, which could help in designing effective therapeutic for treating neuroblastoma. Similar results were obtained in both MYCN amplified and non-MYCN neuroblastoma cell lines, indicating a common mechanism of BORIS/CTCFL action in neuroblastoma.

Melatonin and Pathological Cell Interactions: Mitochondrial Glucose Processing in Cancer Cells

Melatonin is synthesized in the pineal gland at night. Since melatonin is produced in the mitochondria of all other cells in a non-circadian manner, the amount synthesized by the pineal gland is less than 5% of the total. Melatonin produced in mitochondria influences glucose metabolism in all cells. Many pathological cells adopt aerobic glycolysis (Warburg effect) in which pyruvate is excluded from the mitochondria and remains in the cytosol where it is metabolized to lactate. The entrance of pyruvate into the mitochondria of healthy cells allows it to be irreversibly decarboxylated by pyruvate dehydrogenase (PDH) to acetyl coenzyme A (acetyl-CoA). The exclusion of pyruvate from the mitochondria in pathological cells prevents the generation of acetyl-CoA from pyruvate. This is relevant to mitochondrial melatonin production, as acetyl-CoA is a required co-substrate/co-factor for melatonin synthesis. When PDH is inhibited during aerobic glycolysis or during intracellular hypoxia, the deficiency of acetyl-CoA likely prevents mitochondrial melatonin synthesis. When cells experiencing aerobic glycolysis or hypoxia with a diminished level of acetyl-CoA are supplemented with melatonin or receive it from another endogenous source (pineal-derived), pathological cells convert to a more normal phenotype and support the transport of pyruvate into the mitochondria, thereby re-establishing a healthier mitochondrial metabolic physiology.

Follicle-stimulating hormone regulates glycolysis of water buffalo follicular granulosa cells through AMPK/SIRT1 signalling pathway

Glycolysis in follicular granulosa cells (GCs) is the primary source of energy metabolism substrate of oocytes and is closely related to follicular development in mammals. Many physiological functions of GCs are regulated by follicle-stimulating hormone (FSH). In contrast, whether FSH regulates the glycolysis of GCs and its mechanism remains unclear. This study explored the correlation between FSH concentration and glycolysis level of GCs from different diameters of water buffalo follicles, and further explored the mechanism of FSH regulation in glycolysis in vitro cultured GCs. Results showed the variation trend of lactic acid concentration in follicular fluid and the expression level of glycolysis-related genes in GCs were consistent with the variation trend of FSH concentration in follicular fluid from follicles with different diameters. When GCs were treated with FSH in vitro, the expression level of glycolysis-related genes, lactate production and glucose uptake increased correspondingly (p < .05). Furthermore, we found that expression trend of AMPK/Sirtuin1 (SIRT1) pathway-related genes in GCs was consistent with the expression trend of glycolysis-related genes and was positively correlated with FSH concentrations in vivo or cultured in vitro. Activation of SIRT1 increased the expression level of glycolytic key proteins and lactic acid production in GCs, while inhibition of SIRT1 showed the opposite effect. In general, glycolysis in water buffalo GCs in vivo or cultured in vitro was positively correlated with FSH concentration. AMPK/SIRT1 pathway plays an important role in the regulation of FSH on glycolysis in GCs. Our findings will enrich the understanding of FSH regulating the development of water buffalo follicles.

Characterization of genetically modified mice for phosphoglycerate mutase, a vitally-essential enzyme in glycolysis

Glycolytic metabolism is closely involved in physiological homeostasis and pathophysiological states. Among glycolytic enzymes, phosphoglycerate mutase (PGAM) has been reported to exert certain physiological role in vitro, whereas its impact on glucose metabolism in vivo remains unclear. Here, we report the characterization of Pgam1 knockout mice. We observed that homozygous knockout mice of Pgam1 were embryonic lethal. Although we previously reported that both PGAM-1 and -2 affect global glycolytic profile of cancers in vitro, in vivo glucose parameters were less affected both in the heterozygous knockout of Pgam1 and in Pgam2 transgenic mice. Thus, the impact of PGAM on in vivo glucose metabolism is rather complex than expected before.

Succinate Pathway in Head and Neck Squamous Cell Carcinoma: Potential as a Diagnostic and Prognostic Marker

Simple Summary

Emerging evidence points to succinate as an important oncometabolite in cancer development; however, the contribution of the succinate-SUCNR1 axis to cancer progression remains unclear. Head and neck squamous cell carcinoma (HNSCC) is associated with disease and treatment-related morbidity so there is an urgent need for innovation in treatment and diagnosis practices. Our aim was to evaluate the potential of the succinate-related pathway as a diagnostic and prognostic biomarker in HNSCC. The circulating succinate levels are increased in HNSCC, being a potential noninvasive biomarker for HNSCC diagnosis. Moreover, the succinate receptor (SUCNR1) and genes related to succinate metabolism, which are predominantly expressed in the tumoral mucosa as compared with healthy tissue, are positively associated with plasma succinate. Remarkably, we found that SUCNR1 and SDHA expression levels predict prognosis.

Abstract

Head and neck squamous cell carcinoma (HNSCC) is characterized by high rates of mortality and treatment-related morbidity, underscoring the urgent need for innovative and safe treatment strategies and diagnosis practices. Mitochondrial dysfunction is a hallmark of cancer and can lead to the accumulation of tricarboxylic acid cycle intermediates, such as succinate, which function as oncometabolites. In addition to its role in cancer development through epigenetic events, succinate is an extracellular signal transducer that modulates immune response, angiogenesis and cell invasion by activating its cognate receptor SUCNR1. Here, we explored the potential value of the circulating succinate and related genes in HNSCC diagnosis and prognosis. We determined the succinate levels in the serum of 66 pathologically confirmed, untreated patients with HNSCC and 20 healthy controls. We also surveyed the expression of the genes related to succinate metabolism and signaling in tumoral and nontumoral adjacent tissue and in normal mucosa from 50 patients. Finally, we performed immunohistochemical analysis of SUCNR1 in mucosal samples. The results showed that the circulating levels of succinate were higher in patients with HNSCC than in the healthy controls. Additionally, the expression of SUCNR1, HIF-1α, succinate dehydrogenase (SDH) A, and SDHB was higher in the tumor tissue than in the matched normal mucosa. Consistent with this, immunohistochemical analysis revealed an increase in SUCNR1 protein expression in tumoral and nontumoral adjacent tissue. High SUCNR1 and SDHA expression levels were associated with poor locoregional control, and the locoregional recurrence-free survival rate was significantly lower in patients with high SUCNR1 and SDHA expression than in their peers with lower levels (77.1% [95% CI: 48.9–100.0] vs. 16.7% [95% CI: 0.0–44.4], p = 0.018). Thus, the circulating succinate levels are elevated in HNSCC and high SUCNR1/SDHA expression predicts poor locoregional disease-free survival, identifying this oncometabolite as a potentially valuable noninvasive biomarker for HNSCC diagnosis and prognosis.

MIEF2 over-expression promotes tumor growth and metastasis through reprogramming of glucose metabolism in ovarian cancer

Background

Increasing evidence has revealed the close link between mitochondrial dynamic dysfunction and cancer. MIEF2 (mitochondrial elongation factor 2) is mitochondrial outer membrane protein that functions in the regulation of mitochondrial fission. However, the expression, clinical significance and biological functions of MIEF2 are still largely unclear in human cancers, especially in ovarian cancer (OC).

Methods

The expression and clinical significance of MIEF2 were determined by qRT-PCR, western blot and immunohistochemistry analyses in tissues and cell lines of OC. The biological functions of MIEF2 in OC were determined by in vitro and in vivo cell growth and metastasis assays. Furthermore, the effect of MIEF2 on metabolic reprogramming of OC was determined by metabolomics and glucose metabolism analyses.

Results

MIEF2 expression was significantly increased in OC mainly due to the down-regulation of miR-424-5p, which predicts poor survival for patients with OC. Knockdown of MIEF2 significantly suppressed OC cell growth and metastasis both in vitro and in vivo by inhibiting G1-S cell transition, epithelial-to-mesenchymal transition (EMT) and inducing cell apoptosis, while forced expression of MIEF2 had the opposite effects. Mechanistically, mitochondrial fragmentation-suppressed cristae formation and thus glucose metabolism switch from oxidative phosphorylation to glycolysis was found to be involved in the promotion of growth and metastasis by MIEF2 in OC cells.

Conclusions

MIEF2 plays a critical role in the progression of OC and may serve as a valuable prognostic biomarker and therapeutic target in the treatment of this malignancy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-020-01802-9.

HIF-1α is a Potential Molecular Target for Herbal Medicine to Treat Diseases

HIF-1α is an important factor regulating oxygen balance in mammals, and its expression is closely related to various physiological and pathological conditions of the body. Because HIF-1α plays an important role in the occurrence and development of cancer and other diseases, it has become an enduring research hotspot. At the same time, natural medicines and traditional Chinese medicine compounds have amazing curative effects in various diseases related to HIF-1 subtype due to their unique pharmacological effects and more effective ingredients. Therefore, in this article, we first outline the structure of HIF-1α and the regulation related to its expression, then introduce various diseases closely related to HIF-1α, and finally focus on the regulation of natural medicines and compound Chinese medicines through various pathways. This will help us understand HIF-1α systematically, and use HIF-1α as a target to discover more natural medicines and traditional Chinese medicines that can treat related diseases.

Phosphoglycerate Mutase Cooperates with Chk1 Kinase to Regulate Glycolysis

Dysregulated glycolysis, including the cancerous Warburg effect, is closely involved in pathological mechanisms of diseased states. Among glycolytic enzymes, phosphoglycerate mutase (PGAM) has been known to exert certain physiological impact in vitro, whereas its regulatory role on glycolysis remains unclear. Here, we identified that PGAM plays a key role in regulating glycolysis in cancer cells but not in standard cells. Cancer-prone phenotype by PGAM overexpression in vivo was associated with upregulated glycolytic features. PGAM interacts and cooperates with Chk1 to regulate the enhanced glycolysis in cancer cells, especially under oncogenic Ras expressing conditions. Genetic or chemical interference of the PGAM-Chk1 interaction, with intact PGAM activity, abrogated the maintenance of cancerous enhanced glycolysis. Thus, the nonenzymatic function of PGAM is essential for the Warburg effect that accompanies cancerous proliferation.

Melatonin Antagonizes Nickel-Induced Aerobic Glycolysis by Blocking ROS-Mediated HIF-1α/miR210/ISCU Axis Activation

Nickel and its compounds, which are well-documented carcinogens, induce the Warburg effect in normal cells by stabilizing hypoxia-inducible factor 1α (HIF-1α). Melatonin has shown diverse anticancer properties for its reactive oxygen species- (ROS-) scavenging ability. Our aim was to explore how melatonin antagonized a nickel-induced increment in aerobic glycolysis. In the current work, a normal human bronchial epithelium cell line (BEAS-2B) was exposed to a series of nonlethal doses of NiCl₂, with or without 1 mM melatonin. Melatonin attenuated nickel-enhanced aerobic glycolysis. The inhibition effects on aerobic glycolysis were attributed to the capability of melatonin to suppress the regulatory axis comprising HIF-1α, microRNA210 (miR210), and iron-sulfur cluster assembly scaffold protein (ISCU1/2). N-Acetylcysteine (NAC) manifested similar effects as melatonin in scavenging ROS, maintaining prolyl-hydroxylase activity, and mitigating HIF-1α transcriptional activity in nickel-exposed cells. Our results indicated that ROS generation contributed to nickel-caused HIF-1α stabilization and downstream signal activation. Melatonin could antagonize HIF-1α-controlled aerobic glycolysis through ROS scavenging.

DRP1 upregulation promotes pancreatic cancer growth and metastasis through increased aerobic glycolysis

BACKGROUND

Mitochondrial shape is dynamically changed by fusion and fission processes in cells, and dysfunction of this process has become one of the emerging hallmarks of cancer. However, the expression patterns and biological effects of mitochondrial fission and fusion proteins in pancreatic cancer (PC) are still unclear.

METHODS

The expressions of mitochondrial fission and fusion proteins were first evaluated by quantitative reverse transcription polymerase chain reaction and western blot analysis in both PC cell lines and tissue samples. In addition, the biologic functions of the differentially expressed proteins in PC cell growth and metastasis both in vitro and in vivo and their potential underlying mechanisms were systematically explored.

RESULTS

We first found that DRP1 was substantially upregulated in PC cell lines and tissue samples mainly due to the downregulation of miR-29a, which contributed to the poor survival of PC patients. DRP1 promoted the growth and metastasis of PC cells both in vitro and in vivo by inducing G1-S cell cycle transition and matrix metalloproteinase 2 secretion. Mechanistic investigations revealed that increased DRP1 upregulation-mediated mitochondrial fission and subsequently enhanced aerobic glycolysis were involved in the promotion of growth and metastasis by DRP1 in PC cells.

CONCLUSIONS

Our findings demonstrate that mitochondrial fusion protein DRP1 plays a critical oncogenic role in PC cells by enhancing aerobic glycolysis, which could serve as a novel therapeutic target for PC treatment.

Atractylenolide I Induces Apoptosis and Suppresses Glycolysis by Blocking the JAK2/STAT3 Signaling Pathway in Colorectal Cancer Cells

Colorectal cancer (CRC) is the third most common cancer worldwide and is associated with a poor clinical outcome and survival. Therefore, the development of novel therapeutic agents for CRC is imperative. Atractylenolide I (AT-I) is a sesquiterpenoid lactone derivative of Rhizoma Atractylodis macrocephalae that exhibits diverse biological activities, including anti-cancer activities. However, the effects and potential mechanism of AT-I in CRC have yet to be fully elucidated. In this study, we aimed to examine the anti-cancer properties of AT-I and the associated functional mechanisms in vitro and in vivo. We found that AT-I treatment significantly suppressed the viability of CRC cell lines and inhibited colony formation, but to a lesser extent in NCM460 cells. Annexin V/PI staining showed that AT-I induced apoptosis in CRC cells, accompanied by increased caspase-3 and PARP-1 cleavage, enhanced expression of Bax, and reduced expression of Bcl-2. Furthermore, AT-I blocked cell glycolysis by inhibiting both glucose uptake and lactate production in CRC cells, and specifically downregulated the expression of the rate-limiting glycolytic enzyme HK2. In contrast, it had no discernable effects on the glycolytic enzymes PFK and PKM2. A mechanistic study revealed that AT-1 negatively regulates STAT3 phosphorylation through direct interaction with JAK2, thereby inhibiting its activation. Moreover, restoring the expression of STAT3 reversed the effect of AT-I on apoptosis and glycolysis in CRC cells. In vivo results revealed that AT-I significantly suppressed tumor growth in HCT116-xenografted mice. Collectively, our findings indicate that the anti-cancer activity of AT-I in CRC is associated with the induction of apoptosis and suppression of glycolysis in CRC cells, via the disruption of JAK2/STAT3 signaling. Our preliminary experimental data indicate that AT-I may have applications as a promising candidate for the treatment of CRC.

Reactive Oxygen Species Drive Proliferation in Acute Myeloid Leukemia via the Glycolytic Regulator PFKFB3

Acute myeloid leukemia (AML) is a heterogeneous clonal disorder with a poor clinical outcome. Previously, we showed that overproduction of reactive oxygen species (ROS), arising from constitutive activation of NOX2 oxidase, occurs in >60% of patients with AML and that ROS production promotes proliferation of AML cells. We show here that the process most significantly affected by ROS overproduction is glycolysis. Whole metabolome analysis of 20 human primary AML showed that blasts generating high levels of ROS have increased glucose uptake and correspondingly increased glucose metabolism. In support of this, exogenous ROS increased glucose consumption while inhibition of NOX2 oxidase decreased glucose consumption. Mechanistically, ROS promoted uncoupling protein 2 (UCP2) protein expression and phosphorylation of AMPK, upregulating the expression of a key regulatory glycolytic enzyme, 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFKFB3). Overexpression of PFKFB3 promoted glucose uptake and cell proliferation, whereas downregulation of PFKFB3 strongly suppressed leukemia growth both in vitro and in vivo in the NSG model. These experiments provide direct evidence that oxidase-derived ROS promotes the growth of leukemia cells via the glycolytic regulator PFKFB3. Targeting PFKFB3 may therefore present a new mode of therapy for this disease with a poor outcome. SIGNIFICANCE: These findings show that ROS generated by NOX2 in AML cells promotes glycolysis by activating PFKFB3 and suggest PFKFB3 as a novel therapeutic target in AML.

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.

Glucose Starvation-Induced Rapid Death of Nrf1α-Deficient, but Not Nrf2-Deficient, Hepatoma Cells Results from Its Fatal Defects in the Redox Metabolism Reprogramming

Metabolic reprogramming exists in a variety of cancer cells, with the most relevance to glucose as a source of energy and carbon for survival and proliferation. Of note, Nrf1 was shown to be essential for regulating glycolysis pathway, but it is unknown whether it plays a role in cancer metabolic reprogramming, particularly in response to glucose starvation. Herein, we discover that Nrf1α^-/- hepatoma cells are sensitive to rapid death induced by glucose deprivation, such cell death appears to be rescued by Nrf2 interference, but HepG2 (wild-type, WT) or Nrf2^-/- cells are roughly unaffected by glucose starvation. Further evidence revealed that Nrf1α^-/- cell death is resulted from severe oxidative stress arising from aberrant redox metabolism. Strikingly, altered gluconeogenesis pathway was aggravated by glucose starvation of Nrf1α^-/- cells, as also accompanied by weakened pentose phosphate pathway, dysfunction of serine-to-glutathione synthesis, and accumulation of reactive oxygen species (ROS) and damages, such that the intracellular GSH and NADPH were exhausted. These demonstrate that glucose starvation leads to acute death of Nrf1α^-/- , rather than Nrf2^-/- , cells resulting from its fatal defects in the redox metabolism reprogramming. This is owing to distinct requirements of Nrf1 and Nrf2 for regulating the constructive and inducible expression of key genes involved in redox metabolic reprogramming by glucose deprivation. Altogether, this work substantiates the preventive and therapeutic strategies against Nrf1α-deficient cancer by limiting its glucose and energy demands.

Effect of vitrification temperature and cryoprotectant concentrations on the mRNA transcriptome of bovine mature oocytes after vitrifying at immature stage

The present study aimed to investigate the effect of vitrification temperature (VT) and cryoprotective agent concentrations (CPAs) on the mRNA transcriptome of bovine mature oocytes after vitrifying at immature stage. Cumulus oocyte complexes (COCs) were randomly divided into the following five groups: fresh oocytes (control), oocytes vitrified in liquid helium (LHe; -269 °C) with 5.6 M CPAs (LHe 5.6 M), oocytes vitrified in LHe with 6.6 M CPAs (LHe 6.6 M), oocytes vitrified in liquid nitrogen (LN; -196 °C) with 5.6 M CPAs (LN 5.6 M), and oocytes vitrified in LN with 6.6 M CPAs (LN 6.6 M). We performed two experiments in this study. In experiment 1, after vitrification and thawing, oocytes of vitrified and control groups were subjected to in vitro maturation (IVM), in vitro fertilization (IVF) and in vitro culture (IVC). The rates of normal morphology, maturation, cleavage, and blastocyst formation in LHe 5.6 M were higher than those in LN 5.6 M (P < 0.05). The rates of normal morphology and cleavage in LHe 6.6 M were higher than those in LN 6.6 M (P < 0.05). However, the maturation and blastocyst rates were similar (P > 0.05) between LHe 6.6 M and LN 6.6 M. The blastocyst rate of 13.31% in LHe 5.6 M was the highest among all vitrified groups (P < 0.05). In experiment 2, the mRNA transcriptome of each sample was analyzed by Smart-Seq4, and the differentially expressed genes (DEGs) were detected by edgeR (P ≤ 0.05; fold-change ≥ 2). A total of 505 DEGs (342 upregulated and 163 downregulated genes) were detected in LHe 5.6 M; 609 DEGs (493 upregulated and 116 downregulated genes) were detected in LHe 6.6 M; 218 DEGs (101 upregulated and 117 downregulated genes) were determined in LN 5.6 M; and 221 DEGs (104 upregulated and 117 downregulated genes) were detected in LN 6.6 M. LHe vitrification affected the mRNA transcriptome of bovine mature oocytes after vitrifying at immature stage mainly by upregulating gene expression. Decreased CPAs (5.6 M) reduced the effect of vitrification on mRNA transcriptome when LHe vitrification was used. Among the DEGs closely related to bovine oocytes, the genes possibly related to VT were ND2, MPV17L2, PIF1, LPIN1, IMP3, BRD1, DCTN3, DERA, ATP7B, NEK5, HVCN1, and MARK2. The gene that may be associated with CPAs is CC2D2A. Genes that may be affected by VT and CPAs included PGK1, SLC7A3, FITM2, NPM3, ISCU, CWC15, and PSAP.

Dual roles of glutathione S-transferase mu 1 in the development and metastasis of hepatocellular carcinoma

PURPOSE

Reactive oxygen species (ROS) are implicated in carcinogenesis, and cellular antioxidant systems are important for detoxifying ROS and reversing oxidant-mediated modifications. Glutathione S-transferase mu (GSTM) belongs to a family of phase II detoxification enzymes that catalyze the conjugation of reduced glutathione (GSH) to a wide range of endogenous and exogenous electrophilic compounds. The genotype of GSTM1 was associated with the risk and prognosis of cancer in several meta-analyses. This study explored the function of GSTM1 in hepatocellular carcinoma (HCC).

METHODS

Polymerase chain reaction (PCR) and western blotting (WB) were used to detect the levels of gene and protein expression. MTS assays, Transwell assays, and flow cytometry were used to explore the function of GSTM1 in vitro. The xenograft assay and tail vein injection model were used to explore the function of GSTM1 in vivo.

RESULTS

The mRNA and protein expression of GSTM1 was downregulated in HCC, but the expression levels of GSTM1 were not correlated with patient survival time. In vitro, Transwell and doxorubicin (DOX)-induced apoptosis assays revealed that GSTM1 showed opposite functions in different HCC cell lines with varied TP53 genotype statuses. The overexpression of GSTM1 in the above cell lines led to a significant decrease in ROS and an increase in GSH concentration and TP53 levels, suggesting that the controversial role of GSTM1 resulted from the TP53 genotype of HCC cells. The overexpression of GSTM1 promoted cell migration and inhibited apoptosis in the MHCC-97H cell line (TP53, R249S), but inhibited cell migration and increased apoptosis in the SMMC-7721 cell line (TP53 wildtype).

CONCLUSION

GSTM1 down-regulation may partially account for ROS-mediated oxidative damage and HCC carcinogenesis. GSTM1 also regulates tumor progression by disrupting the ROS-TP53 axis in HCC cells with different genetic backgrounds.

Transcriptome Analyses Identify a Metabolic Gene Signature Indicative of Dedifferentiation of Papillary Thyroid Cancer

CONTEXT

Metabolic reprogramming is a common feature of tumorigenesis. It remains unknown concerning the expression pattern of metabolism-associated genes in dedifferentiated thyroid cancer (DDTC).

OBJECTIVE

This study aimed to identify a useful signature to indicate dedifferentiation of papillary thyroid cancer (PTC).

DESIGN AND SETTING

We used one discovery and two validation cohorts to screen out aberrant metabolic genes in DDTC, and further used The Cancer Genome Atlas (TCGA) cohort to search for independent risk factors for the low-differentiated phenotype of PTC as a signature of dedifferentiation. The prediction of the signature for DDTC was validated in the TCGA cohort and the combined Gene Expression Omnibus cohort. We also analyzed the correlations of the signature risk score with clinicopathological features of PTC. Gene set enrichment analyses were performed in the TCGA cohort.

RESULTS

Significant enrichment of metabolic pathways correlated with differentiation status of PTC. A signature of metabolic genes including LPCAT2, ACOT7, HSD17B8, PDE8B, and ST3GAL1 was discovered and validated across three cohorts. The signature was not only predictive of DDTC but also significantly associated with BRAFV600E mutation (P < 0.001), T3/T4 stage (P < 0.001), extrathyroidal extension (P < 0.001), lymph node metastasis (P < 0.001), and tumor/lymph node/metastasis III/IV stage (P < 0.001) in PTC. Downregulations of LPCAT2 expression (P = 0.009) and ST3GAL1 expression (P = 0.005) increased risks of decreased disease-free survival for patients. Furthermore, the signature was implicated in a number of oncogenic biological pathways.

CONCLUSIONS

Our findings suggest that metabolic deregulations mediate dedifferentiation of PTC, and that the metabolic gene signature can be used as a biomarker for DDTC.

Alterations of Methionine Metabolism as Potential Targets for the Prevention and Therapy of Hepatocellular Carcinoma

Several researchers have analyzed the alterations of the methionine cycle associated with liver disease to clarify the pathogenesis of human hepatocellular carcinoma (HCC) and improve the preventive and the therapeutic approaches to this tumor. Different alterations of the methionine cycle leading to a decrease of S-adenosylmethionine (SAM) occur in hepatitis, liver steatosis, liver cirrhosis, and HCC. The reproduction of these changes in MAT1A-KO mice, prone to develop hepatitis and HCC, demonstrates the pathogenetic role of MAT1A gene under-regulation associated with up-regulation of the MAT2A gene (MAT1A:MAT2A switch), encoding the SAM synthesizing enzymes, methyladenosyltransferase I/III (MATI/III) and methyladenosyltransferase II (MATII), respectively. This leads to a rise of MATII, inhibited by the reaction product, with a consequent decrease of SAM synthesis. Attempts to increase the SAM pool by injecting exogenous SAM have beneficial effects in experimental alcoholic and non-alcoholic steatohepatitis and hepatocarcinogenesis. Mechanisms involved in hepatocarcinogenesis inhibition by SAM include: (1) antioxidative effects due to inhibition of nitric oxide (NO•) production, a rise in reduced glutathione (GSH) synthesis, stabilization of the DNA repair protein Apurinic/Apyrimidinic Endonuclease 1 (APEX1); (2) inhibition of c-myc, H-ras, and K-ras expression, prevention of NF-kB activation, and induction of overexpression of the oncosuppressor PP2A gene; (3) an increase in expression of the ERK inhibitor DUSP1; (4) inhibition of PI3K/AKT expression and down-regulation of C/EBPα and UCA1 gene transcripts; (5) blocking LKB1/AMPK activation; (6) DNA and protein methylation. Different clinical trials have documented curative effects of SAM in alcoholic liver disease. Furthermore, SAM enhances the IFN-α antiviral activity and protects against hepatic ischemia-reperfusion injury during hepatectomy in HCC patients with chronic hepatitis B virus (HBV) infection. However, although SAM prevents experimental tumors, it is not curative against already established experimental and human HCCs. The recent observation that the inhibition of MAT2A and MAT2B expression by miRNAs leads to a rise of endogenous SAM and strong inhibition of cancer cell growth could open new perspectives to the treatment of HCC.

Micromanaging aerobic respiration and glycolysis in cancer cells

BACKGROUND

Cancer cells possess a common metabolic phenotype, rewiring their metabolic pathways from mitochondrial oxidative phosphorylation to aerobic glycolysis and anabolic circuits, to support the energetic and biosynthetic requirements of continuous proliferation and migration. While, over the past decade, molecular and cellular studies have clearly highlighted the association of oncogenes and tumor suppressors with cancer-associated glycolysis, more recent attention has focused on the role of microRNAs (miRNAs) in mediating this metabolic shift. Accumulating studies have connected aberrant expression of miRNAs with direct and indirect regulation of aerobic glycolysis and associated pathways.

SCOPE OF REVIEW

This review discusses the underlying mechanisms of metabolic reprogramming in cancer cells and provides arguments that the earlier paradigm of cancer glycolysis needs to be updated to a broader concept, which involves interconnecting biological pathways that include miRNA-mediated regulation of metabolism. For these reasons and in light of recent knowledge, we illustrate the relationships between metabolic pathways in cancer cells. We further summarize our current understanding of the interplay between miRNAs and these metabolic pathways. This review aims to highlight important metabolism-associated molecular components in the hunt for selective preventive and therapeutic treatments.

MAJOR CONCLUSIONS

Metabolism in cancer cells is influenced by driver mutations but is also regulated by posttranscriptional gene silencing. Understanding the nuanced regulation of gene expression in these cells and distinguishing rapid cellular responses from chronic adaptive mechanisms provides a basis for rational drug design and novel therapeutic strategies.

The ubiquitin ligase KBTBD8 regulates PKM1 levels via Erk1/2 and Aurora A to ensure oocyte quality

Tight control of energy metabolism is essential for normal cell function and organism survival. PKM (pyruvate kinase, muscle) isoforms 1 and 2 originate from alternative splicing of PKM pre-mRNA. They are key enzymes in oxidative phosphorylation and aerobic glycolysis, respectively, and are essential for ATP generation. The PKM1:PKM2 expression ratio changes with development and differentiation, and may also vary under metabolic stress and other conditions. Until now, there have been no reports about the function and regulation of PKM isozymes in oocytes. Here, we demonstrate that PKM1 or PKM2 depletion significantly disrupts ATP levels and mitochondrial integrity, and exacerbates free-radical generation and apoptosis in mouse oocytes. We also show that KBTBD8, a female fertility factor in the KBTBD ubiquitin ligase family, selectively regulates PKM1 levels through a signaling cascade that includes Erk1/2 and Aurora A kinases as intermediates. Finally, using RNA sequencing and protein network analysis, we identify several regulatory proteins that may be govern generation of mature PKM1 mRNA. These results suggest KBTBD8 affects PKM1 levels in oocytes via a KBTBD8→Erk1/2→Aurora A axis, and may also affect other essential processes involved in maintaining oocyte quality.

Long non-coding RNAs involved in cancer metabolic reprogramming

Metabolic reprogramming has now been accepted as a hallmark of cancer. Compared to normal cells, cancer cells exhibit different metabolic features, including increased glucose uptake, aerobic glycolysis, enhanced glutamine uptake and glutaminolysis, altered lipid metabolism, and so on. Cancer metabolic reprogramming, which supports excessive cell proliferation and growth, has been widely regulated by activation of oncogenes or loss of tumor suppressors. Here, we review that long non-coding RNAs (lncRNAs) can affect cancer metabolism by mutual regulation with oncogenes or tumor suppressors. Additionally, the interaction of lncRNAs with crucial transcription factors, metabolic enzymes or microRNAs can also effectively modulate the processes of cancer metabolism. LncRNAs-derived metabolism reprogramming allows cancer cells to maintain deregulated proliferation and withstand hostile microenvironment such as energy stress. Understanding the functions of lncRNAs in cancer metabolic reprogramming that contributes to carcinogenesis and cancer development may help to develop novel and effective strategies for cancer diagnosis, prognosis and treatment.

Metformin delays AKT/c-Met-driven hepatocarcinogenesis by regulating signaling pathways for de novo lipogenesis and ATP generation

Hepatocellular carcinoma (HCC) is a lethal malignancy with few effective options for therapeutic treatment in its advanced stages. Metformin, a first-line oral agent used in the treatment of type 2 diabetes, exhibits efficacy in metabolic reprogramming fueling changes in cell growth and proliferation for multiple cancer types, including HCC. However, the molecular mechanism by which metformin delays hepatocarcinogenesis in individuals with hepatic steatosis remains rare. Here, we investigate the preventive efficacy of metformin in a rapid AKT/c-Met-triggered HCC mouse model featuring excessive levels of steatosis. Hematoxylin and eosin staining, Oil Red O staining and immunoblotting were applied for mechanistic investigations. Pharmacological and biochemical strategies were employed to illuminate molecular evidence for HCC cell lines. The results show that metformin obstructs the malignant transformation of hepatocytes in AKT/c-Met mice. Mechanistically, metformin reduces the expression of phospho-ERK (Thr202/Tyr204) and two forms of proto-oncogenes, Cyclin D1 and c-Myc, in AKT/c-Met mice. Moreover, metformin ameliorates FASN-mediated aberrant lipogenesis and HK2/PKM2-driven ATP generation in vivo. Furthermore, metformin represses the expression of FASN and HK-2 by targeting c-Myc in an AMPK-dependent manner in vitro. In addition, metformin is effective at inhibiting PKM2 expression in the presence of an AMPK inhibitor compound C, suggesting that its functioning in PKM2 is AMPK-independent. Our study experimentally validates a novel molecular mechanism by which metformin alleviates enhanced lipogenesis and high energy metabolism during hepatocarcinogenesis, indicating that metformin may serve as an agent for the prevention of HCC in patients with nonalcoholic fatty liver diseases.

Next generation sequencing of RNA reveals novel targets of resveratrol with possible implications for Canavan disease

Resveratrol (RSV) is a small compound first identified as an activator of sirtuin 1 (SIRT1), a key factor in mediating the effects of caloric restriction. Since then, RSV received great attention for its widespread beneficial effects on health and in connection to many diseases. RSV improves the metabolism and the mitochondrial function, and more recently it was shown to restore fatty acid β-oxidation (FAO) capacities in patient fibroblasts harboring mutations with residual enzyme activity. Many of RSV's beneficial effects are mediated by the transcriptional coactivator PGC-1α, a direct target of SIRT1 and a master regulator of the mitochondrial fatty acid oxidation. Despite numerous studies RSV's mechanism of action is still not completely elucidated. Our aim was to investigate the effects of RSV on gene regulation on a wide scale, possibly to detect novel genes whose up-regulation by RSV may be of interest with respect to disease treatment. We performed Next Generation Sequencing of RNA on normal fibroblasts treated with RSV. To investigate whether the effects of RSV are mediated through SIRT1 we expanded the analysis to include SIRT1-knockdown fibroblasts. We identified the aspartoacylase (ASPA) gene, mutated in Canavan disease, to be strongly up-regulated by RSV in several cell lines, including Canavan disease fibroblasts. We further link RSV to the up-regulation of other genes involved in myelination including the glial specific transcription factors POU3F1, POU3F2, and myelin basic protein (MBP). We also observe a strong up-regulation by RSV of the riboflavin transporter gene SLC52a1. Mutations in SLC52a1 cause transient multiple acyl-CoA dehydrogenase deficiency (MADD). Our analysis of alternative splicing identified novel metabolically important genes affected by RSV, among which is particularly interesting the α subunit of the stimulatory G protein (Gsα), which regulates the cellular levels of cAMP through adenylyl cyclase. We conclude that in fibroblasts RSV stimulates the PGC-1α and p53 pathways, and up-regulates genes affecting the glucose metabolism, mitochondrial β-oxidation, and mitochondrial biogenesis. We further confirm that RSV might be a relevant treatment in the correction of FAO deficiencies and we suggest that treatment in other metabolic disorders including Canavan disease and MADD might be also beneficial.

Myc and ChREBP transcription factors cooperatively regulate normal and neoplastic hepatocyte proliferation in mice

Analogous to the c-Myc (Myc)/Max family of bHLH-ZIP transcription factors, there exists a parallel regulatory network of structurally and functionally related proteins with Myc-like functions. Two related Myc-like paralogs, termed MondoA and MondoB/carbohydrate response element-binding protein (ChREBP), up-regulate gene expression in heterodimeric association with the bHLH-ZIP Max-like factor Mlx. Myc is necessary to support liver cancer growth, but not for normal hepatocyte proliferation. Here, we investigated ChREBP's role in these processes and its relationship to Myc. Unlike Myc loss, ChREBP loss conferred a proliferative disadvantage to normal murine hepatocytes, as did the combined loss of ChREBP and Myc. Moreover, hepatoblastomas (HBs) originating in myc^-/-, chrebp^-/-, or myc^-/-/chrebp^-/- backgrounds grew significantly more slowly. Metabolic studies on livers and HBs in all three genetic backgrounds revealed marked differences in oxidative phosphorylation, fatty acid β-oxidation (FAO), and pyruvate dehydrogenase activity. RNA-Seq of livers and HBs suggested seven distinct mechanisms of Myc-ChREBP target gene regulation. Gene ontology analysis indicated that many transcripts deregulated in the chrebp^-/- background encode enzymes functioning in glycolysis, the TCA cycle, and β- and ω-FAO, whereas those dysregulated in the myc^-/- background encode enzymes functioning in glycolysis, glutaminolysis, and sterol biosynthesis. In the myc^-/-/chrebp^-/- background, additional deregulated transcripts included those involved in peroxisomal β- and α-FAO. Finally, we observed that Myc and ChREBP cooperatively up-regulated virtually all ribosomal protein genes. Our findings define the individual and cooperative proliferative, metabolic, and transcriptional roles for the "Extended Myc Network" under both normal and neoplastic conditions.

Deregulation of methionine metabolism as determinant of progression and prognosis of hepatocellular carcinoma

The under-regulation of liver-specific MAT1A gene codifying for S-adenosylmethionine (SAM) synthesizing isozymes MATI/III, and the up-regulation of widely expressed MAT2A, MATII isozyme occurs in hepatocellular carcinoma (HCC). MATα1:MATα2 switch strongly contributes to the fall in SAM liver content both in rodent and human liver carcinogenesis. SAM administration to carcinogen-treated animals inhibits hepatocarcinogenesis. The opposite occurs in Mat1a-KO mice, in which chronic SAM deficiency is followed by HCC development. This review focuses upon the changes, induced by the MATα1:MATα2 switch, involved in HCC development. In association with MATα1:MATα2 switch there occurs, in HCC, global DNA hypomethylation, decline of DNA repair, genomic instability, and deregulation of different signaling pathways such as overexpression of c-MYC (avian myelocytomatosis viral oncogene homolog), increase of polyamine (PA) synthesis and RAS/ERK (Harvey murine sarcoma virus oncogene homolog/extracellular signal-regulated kinase), IKK/NF-kB (I-k kinase beta/nuclear factor kB), PI3K/AKT, and LKB1/AMPK axes. Furthermore, a decrease in MATα1 expression and SAM level induces HCC cell proliferation and survival. SAM treatment in vivo and enforced MATα1 overexpression or MATα2 inhibition, in cultured HCC cells, prevent these changes. A negative correlation of MATα1:MATα2 and MATI/III:MATII ratios with cell proliferation and genomic instability and a positive correlation with apoptosis and global DNA methylation are present in human HCC. Altogether, these data suggest that the decrease of SAM level and the deregulation of MATs are potential therapeutic targets for HCC.

Low ketolytic enzyme levels in tumors predict ketogenic diet responses in cancer cell lines in vitro and in vivo

The ketogenic diet (KD) is a high-fat, very-low-carbohydrate diet that triggers a fasting state by decreasing glucose and increasing ketone bodies, such as β-hydroxybutyrate (βHB). In experimental models and clinical trials, the KD has shown anti-tumor effects, possibly by reducing energy supplies to cells, which damage the tumor microenvironment and inhibit tumor growth. Here, we determined expression levels of genes encoding the ketolytic enzymes 3-hydroxybutyrate dehydrogenase 1 (BDH1) and succinyl-CoA: 3-oxoacid CoA transferase 1 (OXCT1) in 33 human cancer cell lines. We then selected two representative lines, HeLa and PANC-1, for in vivo examination of KD sensitivity in tumors with high or low expression, respectively, of these two enzymes. In mice with HeLa xenografts, the KD increased tumor growth and mouse survival decreased, possibly because these tumors actively consumed ketone bodies as an energy source. Conversely, the KD significantly inhibited growth of PANC-1 xenograft tumors. βHB added to each cell culture significantly increased proliferation of HeLa cells, but not PANCI-1 cells. Downregulation of both BDH1 and OXCT1 rendered HeLa cells sensitive to the KD in vitro and in vivo. Tumors with low ketolytic enzyme expression may be unable to metabolize ketone bodies, thus predicting a better response to KD therapy.

Connections Between Metabolism and Epigenetics in Programming Cellular Differentiation

Researchers are intensifying efforts to understand the mechanisms by which changes in metabolic states influence differentiation programs. An emerging objective is to define how fluctuations in metabolites influence the epigenetic states that contribute to differentiation programs. This is because metabolites such as S-adenosylmethionine, acetyl-CoA, α-ketoglutarate, 2-hydroxyglutarate, and butyrate are donors, substrates, cofactors, and antagonists for the activities of epigenetic-modifying complexes and for epigenetic modifications. We discuss this topic from the perspective of specialized CD4⁺ T cells as well as effector and memory T cell differentiation programs. We also highlight findings from embryonic stem cells that give mechanistic insight into how nutrients processed through pathways such as glycolysis, glutaminolysis, and one-carbon metabolism regulate metabolite levels to influence epigenetic events and discuss similar mechanistic principles in T cells. Finally, we highlight how dysregulated environments, such as the tumor microenvironment, might alter programming events.

UDP-sugar accumulation drives hyaluronan synthesis in breast cancer

Increased uptake of glucose, a general hallmark of malignant tumors, leads to an accumulation of intermediate metabolites of glycolysis. We investigated whether the high supply of these intermediates promotes their flow into UDP-sugars, and consequently into hyaluronan, a tumor-promoting matrix molecule. We quantified UDP-N-Acetylglucosamine (UDP-GlcNAc) and UDP-glucuronic acid (UDP-GlcUA) in human breast cancer biopsies, the levels of enzymes contributing to their synthesis, and their association with the hyaluronan accumulation in the tumor. The content of UDP-GlcUA was 4 times, and that of UDP-GlcNAc 12 times higher in the tumors as compared to normal glandular tissue obtained from breast reductions. The surge of UDP-GlcNAc correlated with an elevated mRNA expression of glutamine-fructose-6-phosphate aminotransferase 2 (GFAT2), one of the key enzymes in the biosynthesis of UDP-GlcNAc, and the expression of GFAT1 was also elevated. The contents of both UDP-sugars strongly correlated with tumor hyaluronan levels. Interestingly, hyaluronan content did not correlate with the mRNA levels of the hyaluronan synthases (HAS1-3), thus emphasizing the role of the UDP-sugar substrates of these enzymes. The UDP-sugars showed a trend to higher levels in ductal vs. lobular cancer subtypes. The results reveal for the first time a dramatic increase of UDP-sugars in breast cancer, and suggest that their high supply drives the accumulation of hyaluronan, a known promoter of breast cancer and other malignancies. In general, the study shows how the disturbed glucose metabolism typical for malignant tumors can influence cancer microenvironment through UDP-sugars and hyaluronan.

Adverse glycaemic effects of cancer therapy: indications for a rational approach to cancer patients with diabetes

Diabetes and cancer are common, chronic, and potentially fatal diseases that frequently co-exist. Observational studies have reported an increased risk of cancer in patients with diabetes. Furthermore, many patients with cancer already have diabetes, or develop hyperglycaemia as a consequence of the tumor or of cancer therapies, and coexisting diabetes confers a greater risk of mortality for many malignancies. Managing oncologic patients with diabetes is often complicated, since the co-existence of diabetes and cancer poses several complex clinical questions: what level of glycaemic control to achieve, which therapy to use, how to deal with glucocorticoid therapies and artificial nutrition, how diabetes complications can affect cancer management, which drug-drug interactions should be taken into account, or even how to manage diabetes at the end of life. In the clinical setting, both at hospital and at home, there are little agreed, evidence-based guidelines on the best management and criteria upon which clinical decisions should be based. A practical solution lies in the implementation of care networks based on communication and ongoing collaboration between Oncologists, Endocrinologists, and the nursing staff, with the patient at the centre of the care process. This manuscript aims to review the current evidence on the effect of cancer therapies on glucose metabolism and to address some of the more common challenges of diabetes treatment in patients with cancer.

MiR-448 promotes glycolytic metabolism of gastric cancer by downregulating KDM2B

MicroRNAs are critical in various human cancers, including gastric cancer (GC). However, the mechanism underlying the GC development remains elusive. In this study, we demonstrate that miR-448 is increased in GC samples and cell lines. Overexpression of miR-448 facilitated the proliferation of GC cells by stimulating glycolysis. Mechanistically, we identified KDM2B, a reader for methylated CpGs, as the target of miR-448 that represses glycolysis and promotes oxidative phosphorylation. Overexpression of miR-448 reduced both the mRNA and protein levels of KDM2B, whereas KDM2B re-expression abrogated the miR-448-mediated glycolytic activities. Furthermore, we discovered Myc as a key target of KDM2B that controls metabolic switch in GC. Importantly, a cohort of 81 GC tissues revealed that miR-448 level closely associated with a battery of glycolytic genes, in which KDM2B showed the strongest anti-correlation coefficient. In addition, enhanced miR-448 level was significantly associated with poor clinical outcomes of GC patients. Hence, we identified a previously unappreciated mechanism by which miR-448 orchestrate epigenetic, transcriptional and metabolic networks to promote GC progression, suggesting the possibility of therapeutic intervention against cancer metabolic pathways.

YAP1-TEAD1-Glut1 axis dictates the oncogenic phenotypes of breast cancer cells by modulating glycolysis

Altered energy metabolism is a universal property of most cancer cells. The Hippo signaling pathway and its principal downstream effector YAP1 are responsible for tissue homeostasis including organ size, cell proliferation, apoptosis, and differentiation. Dysregulation of the Hippo pathway leads to the activation of YAP1 and further culminates in the development of multiple human cancers. In this study, by loss-of-function assay, we demonstrated that YAP1 contributed to the glycolytic phenotype of breast cancer cells. Knockdown of YAP1 inhibited the extracellular acidification rates, glucose consumption, and lactate production of breast cancer cells. Moreover, YAP1 interacted with TEAD1, exerted their transcriptional control of the functional target, glucose transporter 1 (Glut1). Overexpression of Glut1 restored the inhibitory effects of YAP1 knockdown on glycolysis as demonstrated by glucose consumption and lactate production. Suppression of glycolysis by deprivation of glucose largely compromised the oncogenic roles of YAP1 on cell proliferation, apoptosis, and invasive potential. Taken together, our data identify a novel role of YAP1-TEAD1 pathway in cancer energy metabolism.

A prospective study of serum metabolites and glioma risk

Malignant glioma is one of the most lethal adult cancers, yet its etiology remains largely unknown. We conducted a prospective serum metabolomic analysis of glioma based on 64 cases and 64 matched controls selected from Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study. Median time from collection of baseline fasting serum to diagnosis was nine years (inter-decile range 3-20 years). LC/MS-MS identified 730 known metabolites, and conditional logistic regression models estimated odds ratios for one-standard deviation differences in log-metabolite signals. Forty-three metabolites were associated with glioma at P<0.05. 2-Oxoarginine, cysteine, alpha-ketoglutarate, chenodeoxycholate and argininate yielded the strongest metabolite signals and were inversely related to overall glioma risk (0.0065≤P<0.0083). Also, seven xanthine metabolites related to caffeine metabolism were higher in cases than in controls (0.017≤P<0.042). Findings were mostly similar in high-grade glioma cases, although prominent inversely associated metabolites included the secondary bile acids glycocholenate sulfate and 3β-hydroxy-5-cholenoic acid, xenobiotic methyl 4-hydroxybenzoate sulfate, sex steroid 5alpha-pregnan-3beta, 20beta-diol-monosulfate, and cofactor/vitamin oxalate (0.0091≤P<0.021). A serum metabolomic profile of glioma identified years in advance of clinical diagnoses is characterized by altered signals in arginine/proline, antioxidant, and coffee-related metabolites. The observed pattern provides new potential leads regarding the molecular basis relevant to etiologic or sub-clinical biomarkers for glioma.