p53/Lactate dehydrogenase A axis negatively regulates aerobic glycolysis and tumor progression in breast cancer expressing wild‐type p53

Tumor suppressor p53 is a master regulator of apoptosis and plays key roles in cell cycle checkpoints. p53 responds to metabolic changes and alters metabolism through several mechanisms in cancer. Lactate dehydrogenase A (LDHA), a key enzyme in glycolysis, is highly expressed in a variety of tumors and catalyzes pyruvate to lactate. In the present study, we first analyzed the association and clinical significance of p53 and LDHA in breast cancer expressing wild‐type p53 (wt‐p53) and found that LDHA mRNA levels are negatively correlated with wt‐p53 but not with mutation p53 mRNA levels, and low p53 and high LDHA expression are significantly associated with poor overall survival rates. Furthermore, p53 negatively regulates LDHA expression by directly binding its promoter region. Moreover, a series of LDHA gain‐of‐function and rescore experiments were carried out in breast cancer MCF7 cells expressing endogenous wt‐p53, showing that ectopic expression of p53 decreases aerobic glycolysis, cell proliferation, migration, invasion and tumor formation of breast cancer cells and that restoration of the expression of LDHA in p53‐overexpressing cells could abolish the suppressive effect of p53 on aerobic glycolysis and other malignant phenotypes. In conclusion, our findings showed that repression of LDHA induced by wt‐p53 blocks tumor growth and invasion through downregulation of aerobic glycolysis in breast cancer, providing new insights into the mechanism by which p53 contributes to the development and progression of breast cancer.     

Small interfering RNA against PTTG: a novel therapy for ovarian cancer

Ovarian epithelial cancer is a significant cause of death among women, accounting for 5% of all female cancer-related fatalities. A lack of reliable detection methods and resistance to chemotherapy agents are considerable obstacles in the treatment of this cancer. Recently, high-level expression of the pituitary tumor transforming gene (PTTG) was found in a wide range of tumors, including ovarian cancers. Elevated PTTG levels were found to induce cellular transformation in vitro and tumor formation in nude mice. Therefore, we hypothesize a correlation exists between the levels of PTTG expression and tumorigenesis, and that down-regulation of PTTG levels will result in the suppression of tumor growth. We used small interfering RNA (siRNA) to silence PTTG expression in human A2780 ovarian carcinoma cells and assessed the effect of PTTG silencing in tumor formation in vitro and in vivo. The siRNA directed against PTTG reduced its expression at both the mRNA and protein levels. A fifty percent reduction in cell proliferation was achieved in cells constitutively expressing PTTG siRNA compared to vector or control-siRNA transfected cells. Furthermore, colony formation in soft agar was reduced by 70% in PTTG siRNA stable cell lines. Using nude mice, we showed that animals injected with A2780 cells constitutively expressing PTTG-siRNA decreased the incidence of tumor development and tumor growth. Taken together, these results strongly suggest that PTTG may serve as an important molecular target for the discovery of new anticancer agents and treatment strategies.     

PTTG1 inhibits SMAD3 in prostate cancer cells to promote their proliferation

Increased expression of pituitary tumor-transforming gene 1 (PTTG1) occurs during mitosis-related sister chromatid segregation, and characterizes various tumor cells, including prostate cancer. Whereas the mechanism remains unclarified. Here, the PTTG1 levels in a prostate cancer cell line, PC3, were modulated by the expression of PTTG1 transgene or shRNA, showing that the PTTG1 levels affected the proliferation of prostate cancer cells, in vitro and in vivo. Moreover, a significant decrease in mothers against decapentaplegic homolog 3 (SMAD3), a key component of transforming growth factor β (TGFβ) signaling pathway, was induced by PTTG1 overexpression. Since SMAD3 is a ubiquitous cell-cycle inhibitor, our data suggest that PTTG1 may promote the proliferation of prostate cancer cells by inhibiting SMAD3-mediated TGFβ signaling. To identify a causal link, we expressed SMAD3 in PTTG1-overexpressing PC3 cells and found that SMAD3 expression inhibited the augmented cancer cell proliferation by PTTG1overexpression. Furthermore, SMAD3 inhibition by short hairpin RNA (ShRNA) completely rescued the cancer cell proliferation in PTTG1 ShRNA-treated PC3 cells. Taken together, our data suggest that PTTG1 promotes the proliferation of prostate cancer cells via the inhibition of SMAD3. SMAD3 thus appears to be a novel therapeutic target for suppressing the growth of prostate cancer.     

卵巢上皮性癌组织中PTTG的表达与微血管密度和bFGF的关系

目的:探讨垂体肿瘤转化基因(PTTG)在卵巢上皮性癌组织中的表达及其与微血管密度(MVD)计数和碱性成纤维细胞生长因子(bFGF)蛋白表达的关系。方法:采用逆转录聚合酶链反应(RTPCR)技术,检测42例卵巢上皮性癌组织中PTTGmRNA的表达;应用免疫组织化学法,检测PTTG和bFGF蛋白的表达,CD34标记血管内皮细胞并计数MVD。以18例卵巢良性上皮性肿瘤和12例正常卵巢组织进行对照。结果:卵巢上皮性癌组织中PTTG高度表达,并与手术病理分期和淋巴结转移正相关,P值均<0.05;PTTG的表达与年龄、病理类型或组织学分级无关,P>0.05。卵巢上皮性癌组织中PTTG的表达与bFGF蛋白表达及微血管密度正相关,P值均<0.05。结论:卵巢上皮性癌组织中PTTG高度表达参与了卵巢上皮性癌的发生及演进过程。PTTG可能通过激活bFGF蛋白表达促进新生血管生成而促使卵巢上皮性癌发生转移。     

Pituitary tumor transforming gene induces epithelial to mesenchymal transition by regulation of Twist, Snail, Slug, and E-cadherin

Pituitary tumor-transforming gene (PTTG) is an oncogene with its expression levels correlating with tumor development and metastasis. Epithelial to mesenchymal transition (EMT) is a crucial step in tumor progression and metastasis. Using ovarian epithelial tumor cell line (A2780) for loss-of-function or gain-of-function of PTTG in our experiments, we observed up regulation of TGF-β, Twist, Snail, Slug, vimentin and down regulation of E-cadherin on infection of cells with Ad-PTTG cDNA. In contrast reverse phenomena was observed on depletion of PTTG on infection of cells with Ad-PTTG siRNA, suggesting an important role of PTTG in induction of EMT in ovarian cancer cells.     

Artemisinin inhibits the development of esophageal cancer by targeting HIF-1α to reduce glycolysis levels

BackgroundChina has a high incidence of esophageal cancer (EC), mainly squamous cell carcinoma, which is a serious threat to human life. Previous studies have shown that artemisinin can inhibit the proliferation and metastasis of cancer cells, thus inhibiting the progression of cancer. Aerobic glycolysis plays an important role in the uncontrolled growth of tumor cells. However, there are still different opinions on the anti-cancer mechanism, and there have been few studies involving EC. Our pre-experiment found that artemisinin can inhibit the progression of EC by directly regulating aerobic glycolysis.MethodsThe EC cell lines KYSE-150 and KYSE-170 were used to detect the effects of artemisinin on cell viability, proliferation, metastasis, and aerobic glycolysis. Network pharmacology technology was used to explore the potential molecular mechanism of artemisinin inhibiting the development of EC through aerobic glycolysis and the findings were verified by molecular docking.ResultsArtemisinin could inhibit the proliferation, metastasis, and glycolysis of esophageal squamous cell carcinoma (ESCC), and this was verified by the expression of key metastatic proteins (N-cadherin) and key enzymes of glycolysis [hypoxia-inducible factor-1α (HIF-1α), pyruvate kinase M2 (PKM2)]. Through network pharmacology, we found the potential therapeutic target of artemisinin, HIF-1α. The results of molecular docking showed that artemisinin could directly target HIF-1α and promote its degradation.ConclusionsArtemisinin can target HIF-1α to reduce the level of glycolysis and inhibit the development of EC, which may become a targeted drug for the treatment of EC.     

RPL35 promotes neuroblastoma progression via the enhanced aerobic glycolysis

Neuroblastoma (NB) is an rare type of tumor that almost affects children age 5 or younger due to its rapid proliferation ability. The overall survival rate of patients with advanced NB is not satisfactory. Ribosomal proteins (RPs) play a critical role in the development and progress of cancer. However, the contribution of RPL35 in NB has not been proven. In this study, we reveal that RPL35 is upregulated in NB tissues and the upregulation of RPL35 promotes proliferation and migration of NB while RPL35 knockdown significantly restrained the proliferation of NB cells. In terms of mechanism, glycolysis was decreased and the mitochondrial respiration was increased with knockdown of RPL35 in NB cells, indicating that RPL35 function as a positive regulator in aerobic glycolysis. Importantly, our data indicated that RPL35 deficiency decreased HIF1α expression both in mRNA and protein levels. Western blot analysis showed that RPL35 knockdown has a negative regulatory effect on the ERK pathway, and RPL35 modulated aerobic glycolysis in part through its regulation of the RPL35/ERK/HIF1α axis. Overall, RPL35 functions as a positive regulator of aerobic glycolysis, and the RPL35/ERK/HIF1α axis could be a potential therapeutic target for the therapy of NB.     

Tumor suppressor p53 negatively regulates glycolysis stimulated by hypoxia through its target RRAD

Cancer cells display enhanced glycolysis to meet their energetic and biosynthetic demands even under normal oxygen concentrations. Recent studies have revealed that tumor suppressor p53 represses glycolysis under normoxia as a novel mechanism for tumor suppression. As the common microenvironmental stress for tumors, hypoxia drives the metabolic switch from the oxidative phosphorylation to glycolysis, which is crucial for survival and proliferation of cancer cells under hypoxia. The p53''s role and mechanism in regulating glycolysis under hypoxia is poorly understood. Here, we found that p53 represses hypoxia-stimulated glycolysis in cancer cells through RRAD, a newly-identified p53 target. RRAD expression is frequently decreased in lung cancer. Ectopic expression of RRAD greatly reduces glycolysis whereas knockdown of RRAD promotes glycolysis in lung cancer cells. Furthermore, RRAD represses glycolysis mainly through inhibition of GLUT1 translocation to the plasma membrane. Under hypoxic conditions, p53 induces RRAD, which in turn inhibits the translocation of GLUT1 and represses glycolysis in lung cancer cells. Blocking RRAD by siRNA greatly abolishes p53''s function in repressing glycolysis under hypoxia. Taken together, our results revealed an important role and mechanism of p53 in antagonizing the stimulating effect of hypoxia on glycolysis, which contributes to p53''s function in tumor suppression.     

Role of the pituitary tumor transforming gene 1 in the progression of hepatocellular carcinoma

In order to demonstrate the role of the pituitary tumor transforming gene 1 (PTTG1) in the development of hepatocellular carcinoma (HCC) and its value as a molecular target for cancer therapy, we analyzed the expression of PTTG1 mRNA and protein, and their relation to clinicopathological characteristics and basic fibroblast growth factor (bFGF) expression in HCC. It was observed that the level of PTTG1 mRNA and the positive rate of PTTG1 protein in cancerous tissues were significantly higher than that in adjacent non-cancerous tissues (both P< 0.001). The PTTG1 protein levels were correlated with several clinicopathological parameters, including alpha-fetoprotein level, portal vein tumor thrombosis, tumor stage, and bFGF protein level (P< 0.05). The proliferation indices were significantly less and the apoptotic rates were significantly higher in the HepG2 and SMMC-7721 cells treated with PTTG1 siRNA transfection than their untransfected counterparts. The expressions of Caspase-3, Bax, p21 and p53 in HepG2 and SMMC-7721 cells were significantly increased after siRNA knockdown of PTTG1 expression. In conclusion, the PTTG1 gene is up-regulated in the cancerous tissue from patients with HCC and involved in the progression of HCC. Inhibiting PTTG1 expression decreases cell proliferation and induces apoptosis in hepatic cancer cell lines, indicating that PTTG1 may be a new therapeutic target for HCC treatment.     

Targeting metabolic remodeling in glioblastoma multiforme

A key aberrant biological difference between tumor cells and normal differentiated cells is altered metabolism, whereby cancer cells acquire a number of stable genetic and epigenetic alterations to retain proliferation, survive under unfavorable microenvironments and invade into surrounding tissues. A classic biochemical adaptation is the metabolic shift to aerobic glycolysis rather than mitochondrial oxidative phosphorylation, regardless of oxygen availability, a phenomenon termed the "Warburg Effect". Aerobic glycolysis, characterized by high glucose uptake, low oxygen consumption and elevated production of lactate, is associated with a survival advantage as well as the generation of substrates such as fatty acids, amino acids and nucleotides necessary in rapidly proliferating cells. This review discusses the role of key metabolic enzymes and their association with aerobic glycolysis in Glioblastoma Multiforme (GBM), an aggressive, highly glycolytic and deadly brain tumor. Targeting key metabolic enzymes involved in modulating the "Warburg Effect" may provide a novel therapeutic approach either singularly or in combination with existing therapies in GBMs.     

MUC16-mediated activation of mTOR and c-MYC reprograms pancreatic cancer metabolism

MUC16, a transmembrane mucin, facilitates pancreatic adenocarcinoma progression and metastasis. In the current studies, we observed that MUC16 knockdown pancreatic cancer cells exhibit reduced glucose uptake and lactate secretion along with reduced migration and invasion potential, which can be restored by supplementing the culture media with lactate, an end product of aerobic glycolysis. MUC16 knockdown leads to inhibition of mTOR activity and reduced expression of its downstream target c-MYC, a key player in cellular growth, proliferation and metabolism. Ectopic expression of c-MYC in MUC16 knockdown pancreatic cancer cells restores the altered cellular physiology. Our LC-MS/MS based metabolomics studies indicate global metabolic alterations in MUC16 knockdown pancreatic cancer cells, as compared to the controls. Specifically, glycolytic and nucleotide metabolite pools were significantly decreased. We observed similar metabolic alterations that correlated with MUC16 expression in primary tumor tissue specimens from human pancreatic adenocarcinoma cancer patients. Overall, our results demonstrate that MUC16 plays an important role in metabolic reprogramming of pancreatic cancer cells by increasing glycolysis and enhancing motility and invasiveness.     

癌细胞葡萄糖代谢重编程的分子基础

代谢的重编程是癌细胞的基本特征之一,其中葡萄糖代谢方式和途径的改变对癌症的发生和发展至关重要。即使在氧气足够充足的情况下,快速增殖的癌细胞生长所需的能量主要由糖酵解而非氧化磷酸化提供,癌细胞这种特殊的糖代谢现象被称为Warburg效应。这种特有的能量获取方式已在多种癌细胞中得到验证,以癌细胞对葡萄糖高摄取率和利用增加为原理的18F-FDG PET/CT显像已广泛应用于临床的癌症诊断。但癌细胞为何利用有氧酵解获取能量以及有氧酵解进行的分子基础目前尚不明确,本文围绕调控癌细胞糖酵解进程中的直接调控酶、癌基因及致癌代谢小分子进行分析和综述。      

Turning on a fuel switch of cancer: hnRNP proteins regulate alternative splicing of pyruvate kinase mRNA

Unlike normal cells, which metabolize glucose by oxidative phosphorylation for efficient energy production, tumor cells preferentially metabolize glucose by aerobic glycolysis, which produces less energy but facilitates the incorporation of more glycolytic metabolites into the biomass needed for rapid proliferation. The metabolic shift from oxidative phosphorylation to aerobic glycolysis is partly achieved by a switch in the splice isoforms of the glycolytic enzyme pyruvate kinase. Although normal cells express the pyruvate kinase M1 isoform (PKM1), tumor cells predominantly express the M2 isoform (PKM2). Switching from PKM1 to PKM2 promotes aerobic glycolysis and provides a selective advantage for tumor formation. The PKM1/M2 isoforms are generated through alternative splicing of two mutually exclusive exons. A recent study shows that the alternative splicing event is controlled by heterogeneous nuclear ribonucleoprotein (hnRNP) family members hnRNPA1, hnRNPA2, and polypyrimidine tract binding protein (PTB; also known as hnRNPI). These findings not only provide additional evidence that alternative splicing plays an important role in tumorigenesis, but also shed light on the molecular mechanism by which hnRNP proteins regulate cell proliferation in cancer.     

Metabolic phenotype of bladder cancer

Metabolism of bladder cancer represents a key issue for cancer research. Several metabolic altered pathways are involved in bladder tumorigenesis, representing therefore interesting targets for therapy.Tumor cells, including urothelial cancer cells, rely on a peculiar shift to aerobic glycolysis-dependent metabolism (the Warburg-effect) as the main energy source to sustain their uncontrolled growth and proliferation. Therefore, the high glycolytic flux depends on the overexpression of glycolysis-related genes (SRC-3, glucose transporter type 1 [GLUT1], GLUT3, lactic dehydrogenase A [LDHA], LDHB, hexokinase 1 [HK1], HK2, pyruvate kinase type M [PKM], and hypoxia-inducible factor 1-alpha [HIF-1α]), resulting in an overproduction of pyruvate, alanine and lactate. Concurrently, bladder cancer metabolism displays an increased expression of genes favoring the pentose phosphate pathway (glucose-6-phosphate dehydrogenase [G6PD]) and the fatty-acid synthesis (fatty acid synthase [FASN]), along with a decrease of AMP-activated protein kinase (AMPK) and Krebs cycle activities. Moreover, the PTEN/PI3K/AKT/mTOR pathway, hyper-activated in bladder cancer, acts as central regulator of aerobic glycolysis, hence contributing to cancer metabolic switch and tumor cell proliferation.Besides glycolysis, glycogen metabolism pathway plays a robust role in bladder cancer development. In particular, the overexpression of GLUT-1, the loss of the tumor suppressor glycogen debranching enzyme amylo-α-1,6-glucosidase, 4-α-glucanotransferase (AGL), and the increased activity of the tumor promoter enzyme glycogen phosphorylase impair glycogen metabolism. An increase in glucose uptake, decrease in normal cellular glycogen storage, and overproduction of lactate are consequences of decreased oxidative phosphorylation and inability to reuse glucose into the pentose phosphate and de novo fatty acid synthesis pathways. Moreover, AGL loss determines augmented levels of the serine-to-glycine enzyme serine hydroxymethyltransferase-2 (SHMT2), resulting in an increased glycine and purine ring of nucleotides synthesis, thus supporting cells proliferation.A deep understanding of the metabolic phenotype of bladder cancer will provide novel opportunities for targeted therapeutic strategies.     

Methylation-associated silencing of miR-9-1 promotes nasopharyngeal carcinoma progression and glycolysis via HK2

Characteristically, cancer cells metabolize glucose through aerobic glycolysis, known as the Warburg effect. Accumulating evidence suggest that during cancer formation, microRNAs (miRNAs) could regulate such metabolic reprogramming. In the present study, miR-9-1 was identified as significantly hypermethylated in nasopharyngeal carcinoma (NPC) cell lines and clinical tissues. Ectopic expression of miR-9-1 inhibited NPC cell growth and glycolytic metabolism, including reduced glycolysis, by reducing lactate production, glucose uptake, cellular glucose-6-phosphate levels, and ATP generation in vitro and tumor proliferation in vivo. HK2 (encoding hexokinase 2) was identified as a direct target of miR-9-1 using luciferase reporter assays and Western blotting. In NPC cells, hypermethylation regulates miR-9-1 expression and inhibits HK2 translation by directly targeting its 3' untranslated region. MiR-9-1 overexpression markedly reduced HK2 protein levels. Restoration of HK2 expression attenuated the inhibitory effect of miR-9-1 on NPC cell proliferation and glycolysis. Fluorescence in situ hybridization results indicated that miR-9-1 expression was an independent prognostic factor in NPC. Our findings revealed the role of the miR-9-1/HK2 axis in the metabolic reprogramming of NPC, providing a potential therapeutic strategy for NPC.     

JQ1 suppresses tumor growth through downregulating LDHA in ovarian cancer

Amplification and overexpression of c-Myc is commonly seen in human ovarian cancers, and this could be a potentially novel therapeutic target for this disease. JQ1, a selective small-molecule BET bromodomain (BRDs) inhibitor, has been found to suppress tumor progression in several cancer cell types. Using ovarian cancer cell lines, a transgenic mouse model, and primary cell cultures from human ovarian cancer tissues, we demonstrated that JQ1 significantly suppressed cellular proliferation and induced cell cycle arrest and apoptosis in ovarian cancer cells and mouse model via targeting c-Myc. In addition, JQ1 had multiple influences on cancer metabolism, particularly in the aerobic glycolysis pathway. JQ1 reduced both the activity and phosphorylation of LDHA, inhibited lactate production, and decreased the energy supply to ovarian cancer cell lines and tumors. Taken together, our findings suggest that JQ1 is an efficacious anti-tumor agent in ovarian cancer that is associated with cell cycle arrest, induction of apoptosis and alterations of metabolism.