Metabolic Reprogramming and Oncogenesis

UBE2C enhances temozolomide resistance by regulating the expression of p53 to induce aerobic glycolysis in glioma

UBE2C is overexpressed in gliomas, and its overexpression has been reported to be correlated with the drug resistance of gliomas to some extent. In this study, we explore the role of UBE2C in regulating temozolomide (TMZ) resistance in glioma and investigate the underlying mechanisms involved. Twenty normal brain tissues and 100 glioma tissues from 50 TMZ-resistant patients and 50 TMZ-sensitive patients are included in this study. TMZ-resistant cell lines are constructed to explore the role of UBE2C in regulating glioma cell viability and TMZ resistance. Our results show that both the mRNA and protein levels of UBE2C are significantly elevated in the brain tissues of glioma patients, especially in those of TMZ-resistant patients. Consistently, UBE2C expression is markedly upregulated in TMZ-resistant cell lines. Overexpression of UBE2C rescues glioma cells from TMZ-mediated apoptosis and enhances cell viability. In contrast, downregulation of UBE2C expression further enhances TMZ function, increases cell apoptosis and decreases cell viability. Mechanistically, UBE2C overexpression decreases p53 expression and enhances aerobic glycolysis level by increasing ATP level, lactate production, and glucose uptake. Downregulation of p53 level abolishes the role of UBE2C downregulation in inhibiting TMZ resistance and aerobic glycolysis in glioma cells. Moreover, an animal assay confirms that downregulation of UBE2C expression further suppresses tumor growth in the context of TMZ treatment. Collectively, this study reveals that downregulation of UBE2C expression enhances the sensitivity of glioma cells to TMZ by regulating the expression of p53 to inhibit aerobic glycolysis.

Emerging roles of cytosolic phosphoenolpyruvate kinase 1 (PCK1) in cancer

Although it was traditionally believed that gluconeogenesis enzymes were absent from cancers that did not originate in gluconeogenic organs, numerous investigations have shown that they are functionally expressed in a variety of tumors as mediators of shortened forms of Gluconeogenesis. One of the isomers of PEPCK, the first-rate limiting enzyme in gluconeogenesis, is PCK 1, which catalyzes the conversion of oxaloacetate (OAA) and GTP into PEP, CO2, and GDP. It is also known as PEPCK-C or PCK1, and it is cytosolic. Despite being paradoxical, it has been demonstrated that, in addition to its enzymatic role in normal metabolism, this enzyme also plays a role in tumors that arise in gluconeogenic and non-gluconeogenic organs. According to newly available research, it has metabolic and non-metabolic roles in tumor progression and development. Thus, this review will give insight into PCK1 relationship, function, and mechanism in or with different types of cancer using contemporary findings.

Identifying Treatment Resistance Related Pathways by Analyzing Serum Extracellular Vesicles of Patients With Resistant Versus Regressed Retinoblastoma

Purpose

To identify the genes and pathways responsible for treatment resistance (TR) in retinoblastoma (RB) by analyzing serum small extracellular vesicles (sEVs) of patients with TR active RB (TR-RB) and completely regressed RB (CR-RB).

Methods

Serum-derived sEVs were characterized by transmission electron microscopy and nanoparticle tracking analysis. sEV transcriptome profiles of two TR-RB and one CR-RB with good response (>20 years tumor free) were compared to their age-matched controls (n = 3). Gene expression data were analyzed by the R Bioconductor package. The CD9 protein and mRNA expression of CD9, CD63, and CD81 were studied in five RB tumors and two control retinae by immunohistochemistry and quantitative reverse transcription-polymerase chain reaction.

Results

The isolated serum sEVs were round shaped and within the expected size (30-150 nm), and they had zeta potentials ranging from -10.8 to 15.9 mV. The mean ± SD concentrations of sEVs for two adults and four children were 1.1 × 1012 ± 0.1 and 5.8 × 1011 ± 1.7 particles/mL. Based on log2 fold change of ±2 and P < 0.05 criteria, there were 492 dysregulated genes in TR-RB and 184 in CR-RB. KAT2B, VWA1, CX3CL1, MLYCD, NR2F2, USP46-AS1, miR6724-4, and LINC01257 genes were specifically dysregulated in TR-RB. Negative regulation of apoptotic signaling, cell growth, and proton transport genes were greater than fivefold expressed only in TR-RB. CD9, CD63, and CD81 mRNA levels were high in RB tumors versus control retina, with increased and variable CD9 immunoreactivity in the invasive areas of the tumor.

Conclusions

Serum sEVs could serve as a potential liquid biopsy source for understanding TR mechanisms in RB.

Downregulation of angulin-1/LSR induces malignancy via upregulation of EGF-dependent claudin-2 and TGF-β-dependent cell metabolism in human lung adenocarcinoma A549 cells

Abnormal expression of bicellular tight junction claudins, including claudin-2 are observed during carcinogenesis in human lung adenocarcinoma. However, little is known about the role of tricellular tight junction molecule angulin-1/lipolysis-stimulated lipoprotein receptor (LSR). In the lung adenocarcinoma tissues examined in the present study, expression of claudin-2 was higher than in normal lung tissues, while angulin-1/LSR was poorly or faintly expressed. We investigated how loss of angulin-1/LSR affects the malignancy of lung adenocarcinoma cell line A549 and normal human lung epithelial (HLE) cells. The EGF receptor tyrosine kinase inhibitor AG1478 prevented the increase of claudin-2 expression induced by EGF in A549 cells. Knockdown of LSR induced expression of claudin-2 at the protein and mRNA levels and AG1478 prevented the upregulation of claudin-2 in A549 cells. Knockdown of LSR induced cell proliferation, cell migration and cell metabolism in A549 cells. Knockdown of claudin-2 inhibited the cell proliferation but did not affect the cell migration or cell metabolism of A549 cells. The TGF-β type I receptor inhibitor EW-7197 prevented the decrease of LSR and claudin-2 induced by TGF-β1 in A549 cells and 2D culture of normal HLE cells. EW-7197 prevented the increase of cell migration and cell metabolism induced by TGF-β1 in A549 cells. EW-7197 prevented the increase of epithelial permeability of FITC-4kD dextran induced by TGF-β1 in 2.5D culture of normal HLE cells. In conclusion, downregulation of angulin-1/LSR induces malignancy via EGF-dependent claudin-2 and TGF-β-dependent cell metabolism in human lung adenocarcinoma.

LPLUNC1 reduces glycolysis in nasopharyngeal carcinoma cells through the PHB1-p53/c-Myc axis

Cancer cells prefer glycolysis to support their proliferation. Our previous studies have shown that the long palate, lung, and nasal epithelial cell clone 1 (LPLUNC1) can upregulate prohibitin 1 (PHB1) expression to inhibit the proliferation of nasopharyngeal carcinoma (NPC) cells. Given that PHB1 is an important regulator of cell energy metabolism, we explored whether and how LPLUNC1 regulated glucose glycolysis in NPC cells. LPLUNC1 or PHB1 overexpression decreased glycolysis and increased oxidative phosphorylation (OXPHOS)-related protein expression in NPC cells, promoting phosphorylated PHB1 nuclear translocation through 14-3-3σ. LPLUNC1 overexpression also increased p53 but decreased c-Myc expression in NPC cells, which were crucial for the decrease in glycolysis and increase in OXPHOS-related protein expression induced by LPLUNC1 overexpression. Finally, we found that treatment with all-trans retinoic acid (ATRA) reduced the viability and clonogenicity of NPC cells, decreased glycolysis, and increased OXPHOS-related protein expression by enhancing LPLUNC1 expression in NPC cells. Therefore, the LPLUNC1-PHB1-p53/c-Myc axis decreased glycolysis in NPC cells, and ATRA upregulated LPLUNC1 expression, ATRA maybe a promising drug for the treatment of NPC.

P2RX7 promotes osteosarcoma progression and glucose metabolism by enhancing c-Myc stabilization

BACKGROUND

Osteosarcoma is the most common malignant tumor in bone and its prognosis has reached a plateau in the past few decades. Recently, metabolic reprogramming has attracted increasing attention in the field of cancer research. In our previous study, P2RX7 has been identified as an oncogene in osteosarcoma. However, whether and how P2RX7 promotes osteosarcoma growth and metastasis through metabolic reprogramming remains unexplored.

METHODS

We used CRISPR/Cas9 genome editing technology to establish P2RX7 knockout cell lines. Transcriptomics and metabolomics were performed to explore metabolic reprogramming in osteosarcoma. RT-PCR, western blot and immunofluorescence analyses were used to determine gene expression related to glucose metabolism. Cell cycle and apoptosis were examined by flowcytometry. The capacity of glycolysis and oxidative phosphorylation were assessed by seahorse experiments. PET/CT was carried out to assess glucose uptake in vivo.

RESULTS

We demonstrated that P2RX7 significantly promotes glucose metabolism in osteosarcoma via upregulating the expression of genes related to glucose metabolism. Inhibition of glucose metabolism largely abolishes the ability of P2RX7 to promote osteosarcoma progression. Mechanistically, P2RX7 enhances c-Myc stabilization by facilitating nuclear retention and reducing ubiquitination-dependent degradation. Furthermore, P2RX7 promotes osteosarcoma growth and metastasis through metabolic reprogramming in a predominantly c-Myc-dependent manner.

CONCLUSIONS

P2RX7 plays a key role in metabolic reprogramming and osteosarcoma progression via increasing c-Myc stability. These findings provide new evidence that P2RX7 might be a potential diagnostic and/or therapeutic target for osteosarcoma. Novel therapeutic strategies targeting metabolic reprogramming appear to hold promise for a breakthrough in the treatment of osteosarcoma.

Untargeted metabolomics reveals alterations in the metabolic reprogramming of prostate cancer cells by double-stranded DNA-modified gold nanoparticles

Metabolic reprogramming plays an important role in the development of prostate cancer (PCa). However, there are few reports on the effects of nanomaterials as vectors on cancer metabolic reprogramming. Herein, a type of nanoparticle with good biocompatibility was synthesized by modifying the double-stranded of DNA containing a sulfhydryl group on the surface of gold nanoparticles (AuNPs-dsDNA) through salt-aging conjugation methods. The resultant AuNPs-dsDNA complexes possessed low toxicity to PC3 and DU145 cells in vitro. There was also no obvious hepatorenal toxicity after intravenous injection of AuNPs-dsDNA complexes in vivo, which indicated that these nanoparticles had good biological compatibilities. We investigated their biological functions using prostate cancer cells. Seahorse assay showed that AuNPs-dsDNA complexes could increase glycolysis and glycolysis capacity both in PC3 and DU145 cells. We further detected the expression of glycolysis-related genes by qPCR assay, and found that PKM2, PDHA, and LDHA were significantly upregulated. Furthermore, untargeted metabolomics revealed that PC (18:2(9Z,12Z)/18:2(9Z,12Z)) and PC (18:0/18:2 (9Z,12Z)) levels were decreased and inosinic acid level was increased in PC3 cells. Whereas (3S,6E,10E)-1,6,10,14-Phytatetraen-3-ol, Plasmenyl-PE 36:5 and Cer (d18:2/18:2) were decreased, PE 21:3 and 1-pyrrolidinecarboxaldehyde were increased in DU145 cells after co-culturing with AuNPs-dsDNA. In summary, we found that AuNPs and AuNPs-dsDNA complexes possibly regulate the metabolic reprogramming of cancer cells mainly through the lipid metabolic pathways, which could compensate for the previously mentioned phenomenon of enhanced glycolysis and glycolysis capacity. This will provide an important theoretical basis for our future research on the characteristic targeted design of nanomaterials for cancer metabolism.

A requirement for autophagy in HMGA2-induced metabolic reprogramming to support Cd-induced migration

High mobility group A2 (HMGA2) is closely related to the occurrence, development and prognosis of tumors. But the mechanism is unclear. Metabolic reprogramming is a dominant way to meet anabolic and energy requirements of tumor cells for their survival, growth and proliferation. Here, we investigated the role of metabolic reprogramming from oxidative phosphorylation (OXPHOS) to glycolysis mediated by HMGA2/autophagy axis in cadmium (Cd, CdCl₂)-induced migration. First, we found that Cd induced glycolysis and reduced OXPHOS in vivo (0.5 and 1 mg/kg, i.p. or 0.8 and 1.6 μM, i.t.) and in vitro (2 μM in A549 cells and 0.05 μM in HELF cells). Then, genetic knockdown of HMGA2 restored Cd-reduced mitochondrial mass and OXPHOS and inhibited Cd-increased glycolysis, indicating that HMGA2 was involved in Cd-induced metabolic reprogramming. 2-Deoxy-d-glucose (2DG, 5 mM), the inhibitor of glycolysis decreased Cd/HMGA2-induced cell migration and restored Cd/HMGA2-decreased OXPHOS and mitochondrial mass. Inhibition of autophagy by 3-Methyladenine (3MA, 3 mM) elucidated an essential role of autophagy in HMGA2-induced glycolysis, migration, and HMGA2-reduced OXPHOS. Overall, our study demonstrated that autophagy was required for HMGA2-mediated metabolic reprogramming, which was critical for Cd-induced migration. Targeting HMGA2 and autophagy-dependent reprogrammed metabolism may be an effective way to inhibit Cd-induced cell migration.

Cancer Metabostemness and Metabolic Reprogramming via P2X7 Receptor

The heterogeneity of tumor cell mass and the plasticity of cancer cell phenotypes in solid tumors allow for the insurgence of resistant and metastatic cells, responsible for cancer patients' clinical management's main challenges. Among several factors that are responsible for increased cancer aggression, metabolic reprogramming is recently emerging as an ultimate cancer hallmark, as it is central for cancer cell survival and self-renewal, metastasis and chemoresistance. The P2X7 receptor, whose expression is upregulated in many solid and hematological malignancies, is also emerging as a good candidate in cancer metabolic reprogramming and the regulation of stem cell proliferation and differentiation. Metabostemness refers to the metabolic reprogramming of cancer cells toward less differentiated (CSCs) cellular states, and we believe that there is a strong correlation between metabostemness and P2X7 receptor functions in oncogenic processes. Here, we summarize important aspects of P2X7 receptor functions in normal and tumor tissues as well as essential aspects of its structure, regulation, pharmacology and its clinical use. Finally, we review current knowledge implicating P2X7 receptor functions in cancer-related molecular pathways, in metabolic reprogramming and in metabostemness.

How Far Are We from Prescribing Fasting as Anticancer Medicine?

(1) Background: the present review provides a comprehensive and up-to date overview of the potential exploitation of fasting as an anticancer strategy. The rationale for this concept is that fasting elicits a differential stress response in the setting of unfavorable conditions, empowering the survival of normal cells, while killing cancer cells. (2) Methods: the present narrative review presents the basic aspects of the hormonal, molecular, and cellular response to fasting, focusing on the interrelationship of fasting with oxidative stress. It also presents nonclinical and clinical evidence concerning the implementation of fasting as adjuvant to chemotherapy, highlighting current challenges and future perspectives. (3) Results: there is ample nonclinical evidence indicating that fasting can mitigate the toxicity of chemotherapy and/or increase the efficacy of chemotherapy. The relevant clinical research is encouraging, albeit still in its infancy. The path forward for implementing fasting in oncology is a personalized approach, entailing counteraction of current challenges, including: (i) patient selection; (ii) fasting patterns; (iii) timeline of fasting and refeeding; (iv) validation of biomarkers for assessment of fasting; and (v) establishment of protocols for patients’ monitoring. (4) Conclusion: prescribing fasting as anticancer medicine may not be far away if large randomized clinical trials consolidate its safety and efficacy.

Pyruvate kinase variant of fission yeast tunes carbon metabolism, cell regulation, growth and stress resistance

Cells balance glycolysis with respiration to support their metabolic needs in different environmental or physiological contexts. With abundant glucose, many cells prefer to grow by aerobic glycolysis or fermentation. Using 161 natural isolates of fission yeast, we investigated the genetic basis and phenotypic effects of the fermentation-respiration balance. The laboratory and a few other strains depended more on respiration. This trait was associated with a single nucleotide polymorphism in a conserved region of Pyk1, the sole pyruvate kinase in fission yeast. This variant reduced Pyk1 activity and glycolytic flux. Replacing the "low-activity" pyk1 allele in the laboratory strain with the "high-activity" allele was sufficient to increase fermentation and decrease respiration. This metabolic rebalancing triggered systems-level adjustments in the transcriptome and proteome and in cellular traits, including increased growth and chronological lifespan but decreased resistance to oxidative stress. Thus, low Pyk1 activity does not lead to a growth advantage but to stress tolerance. The genetic tuning of glycolytic flux may reflect an adaptive trade-off in a species lacking pyruvate kinase isoforms.

Intercellular mitochondria trafficking highlighting the dual role of mesenchymal stem cells as both sensors and rescuers of tissue injury

Mitochondria are crucial organelles that not only regulate the energy metabolism, but also the survival and fate of eukaryotic cells. Mitochondria were recently discovered to be able to translocate from one cell to the other. This phenomenon was observed in vitro and in vivo, both in physiological and pathophysiological conditions including tissue injury and cancer. Mitochondria trafficking was found to exert prominent biological functions. In particular, several studies pointed out that this process governs some of the therapeutic effects of mesenchymal stem cells (MSCs). In this review, we give an overview of the current knowledge on MSC-dependent intercellular mitochondria trafficking and further discuss the recent findings on the intercellular mitochondria transfer between differentiated and mesenchymal stem cells, their biological significance and the mechanisms underlying this process.

Diverse Stakeholders of Tumor Metabolism: An Appraisal of the Emerging Approach of Multifaceted Metabolic Targeting by 3-Bromopyruvate

Malignant cells possess a unique metabolic machinery to endure unobstructed cell survival. It comprises several levels of metabolic networking consisting of 1) upregulated expression of membrane-associated transporter proteins, facilitating unhindered uptake of substrates; 2) upregulated metabolic pathways for efficient substrate utilization; 3) pH and redox homeostasis, conducive for driving metabolism; 4) tumor metabolism-dependent reconstitution of tumor growth promoting the external environment; 5) upregulated expression of receptors and signaling mediators; and 6) distinctive genetic and regulatory makeup to generate and sustain rearranged metabolism. This feat is achieved by a "battery of molecular patrons," which acts in a highly cohesive and mutually coordinated manner to bestow immortality to neoplastic cells. Consequently, it is necessary to develop a multitargeted therapeutic approach to achieve a formidable inhibition of the diverse arrays of tumor metabolism. Among the emerging agents capable of such multifaceted targeting of tumor metabolism, an alkylating agent designated as 3-bromopyruvate (3-BP) has gained immense research focus because of its broad spectrum and specific antineoplastic action. Inhibitory effects of 3-BP are imparted on a variety of metabolic target molecules, including transporters, metabolic enzymes, and several other crucial stakeholders of tumor metabolism. Moreover, 3-BP ushers a reconstitution of the tumor microenvironment, a reversal of tumor acidosis, and recuperative action on vital organs and systems of the tumor-bearing host. Studies have been conducted to identify targets of 3-BP and its derivatives and characterization of target binding for further optimization. This review presents a brief and comprehensive discussion about the current state of knowledge concerning various aspects of tumor metabolism and explores the prospects of 3-BP as a safe and effective antineoplastic agent.

Trial watch: dietary interventions for cancer therapy

Dietary interventions have a profound impact on whole body metabolism, including oncometabolism (the metabolic features allowing cancer cells to proliferate) and immunometabolism (the catabolic and anabolic reactions that regulate immune responses). Recent preclinical studies demonstrated that multiple dietary changes can improve anticancer immunosurveillance of chemo-, radio- and immunotherapy. These findings have fostered the design of clinical trials evaluating the capacity of dietary interventions to synergize with treatment and hence limit tumor progression. Here, we discuss the scientific rationale for harnessing dietary interventions to improve the efficacy of anticancer therapy and present up-to-date information on clinical trials currently investigating this possibility.

Double genetic disruption of lactate dehydrogenases A and B is required to ablate the "Warburg effect" restricting tumor growth to oxidative metabolism

Increased glucose consumption distinguishes cancer cells from normal cells and is known as the "Warburg effect" because of increased glycolysis. Lactate dehydrogenase A (LDHA) is a key glycolytic enzyme, a hallmark of aggressive cancers, and believed to be the major enzyme responsible for pyruvate-to-lactate conversion. To elucidate its role in tumor growth, we disrupted both the LDHA and LDHB genes in two cancer cell lines (human colon adenocarcinoma and murine melanoma cells). Surprisingly, neither LDHA nor LDHB knockout strongly reduced lactate secretion. In contrast, double knockout (LDHA/B-DKO) fully suppressed LDH activity and lactate secretion. Furthermore, under normoxia, LDHA/B-DKO cells survived the genetic block by shifting their metabolism to oxidative phosphorylation (OXPHOS), entailing a 2-fold reduction in proliferation rates in vitro and in vivo compared with their WT counterparts. Under hypoxia (1% oxygen), however, LDHA/B suppression completely abolished in vitro growth, consistent with the reliance on OXPHOS. Interestingly, activation of the respiratory capacity operated by the LDHA/B-DKO genetic block as well as the resilient growth were not consequences of long-term adaptation. They could be reproduced pharmacologically by treating WT cells with an LDHA/B-specific inhibitor (GNE-140). These findings demonstrate that the Warburg effect is not only based on high LDHA expression, as both LDHA and LDHB need to be deleted to suppress fermentative glycolysis. Finally, we demonstrate that the Warburg effect is dispensable even in aggressive tumors and that the metabolic shift to OXPHOS caused by LDHA/B genetic disruptions is responsible for the tumors' escape and growth.

Peroxisomes and cancer: The role of a metabolic specialist in a disease of aberrant metabolism

Cancer is irrevocably linked to aberrant metabolic processes. While once considered a vestigial organelle, we now know that peroxisomes play a central role in the metabolism of reactive oxygen species, bile acids, ether phospholipids (e.g. plasmalogens), very-long chain, and branched-chain fatty acids. Immune system evasion is a hallmark of cancer, and peroxisomes have an emerging role in the regulation of cellular immune responses. Investigations of individual peroxisome proteins and metabolites support their pro-tumorigenic functions. However, a significant knowledge gap remains regarding how individual functions of proteins and metabolites of the peroxisome orchestrate its potential role as a pro-tumorigenic organelle. This review highlights new advances in our understanding of biogenesis, enzymatic functions, and autophagic degradation of peroxisomes (pexophagy), and provides evidence linking these activities to tumorigenesis. Finally, we propose avenues that may be exploited to target peroxisome-related processes as a mode of combatting cancer.

The role of compartmentalized signaling pathways in the control of mitochondrial activities in cancer cells

Mitochondria are the powerhouse organelles present in all eukaryotic cells. They play a fundamental role in cell respiration, survival and metabolism. Stimulation of G-protein coupled receptors (GPCRs) by dedicated ligands and consequent activation of the cAMP·PKA pathway finely couple energy production and metabolism to cell growth and survival. Compartmentalization of PKA signaling at mitochondria by A-Kinase Anchor Proteins (AKAPs) ensures efficient transduction of signals generated at the cell membrane to the organelles, controlling important aspects of mitochondrial biology. Emerging evidence implicates mitochondria as essential bioenergetic elements of cancer cells that promote and support tumor growth and metastasis. In this context, mitochondria provide the building blocks for cellular organelles, cytoskeleton and membranes, and supply all the metabolic needs for the expansion and dissemination of actively replicating cancer cells. Functional interference with mitochondrial activity deeply impacts on cancer cell survival and proliferation. Therefore, mitochondria represent valuable targets of novel therapeutic approaches for the treatment of cancer patients. Understanding the biology of mitochondria, uncovering the molecular mechanisms regulating mitochondrial activity andmapping the relevant metabolic and signaling networks operating in cancer cells will undoubtly contribute to create a molecular platform to be used for the treatment of proliferative disorders. Here, we will highlight the emerging roles of signaling pathways acting downstream to GPCRs and their intersection with the ubiquitin proteasome system in the control of mitochondrial activity in different aspects of cancer cell biology.