Silencing LDHA inhibits proliferation, induces apoptosis and increases chemosensitivity to temozolomide in glioma cells

Inhibition of heterogeneous nuclear ribonucleoproteins A1 and oxidative stress reduces glycolysis via pyruvate kinase M2 in chronic thromboembolic pulmonary hypertension

Background and Objective

Chronic thromboembolic pulmonary hypertension (CTEPH) is a lethal complication of pulmonary embolism involving pulmonary artery occlusion and microvascular disease. The glucose metabolism and reactive oxygen species (ROS) production may be perturbed in CTEPH, but the precise mechanisms are unclear. This study investigated glucose metabolism in CTEPH employing pulmonary endarterectomy (PEA)-derived pulmonary artery smooth muscle cells (PASMCs) and characterized the roles of pyruvate kinase M2 (PKM2) and its regulation by heterogeneous nuclear ribonucleoproteins A1 (hnRNPA1) and ROS in CTEPH.

Methods

PEA tissues and blood samples of CTEPH patients were collected to study the levels of PKM2. Primary PASMCs were isolated from PEA tissues. We used small interfering RNAs to knock down PKM2 and hnRNPA1, and applied antioxidant N-acetylcysteine (NAC) and mito-TEMPO to reduce ROS production. The expression of glucometabolic genes, ROS production, glycolysis rate and proliferative and migratory activities were analyzed in PEA-derived PASMCs.

Results

PKM2 levels in serum and PEA tissues of CTEPH patients were higher than that of the healthy controls. Compared to the control PASMCs, PEA-derived PASMCs showed increased PKM2 expression and ROS production. The rates of glycolysis, proliferation and migration were increased in PEA-PASMCs and could be mitigated by PKM2 downregulation through hnRNPA1 or ROS inhibition.

Conclusions

Increased glycolysis and PKM2 expression were found in PEA-PASMCs. Inhibition of hnRNPA1 or ROS corrected the aberrant glycolysis, cell proliferation and migration by downregulating PKM2. Regulation of the hnRNPA1/PKM2 axis represents a potential therapeutic target for the treatment of CTEPH.

A Novel Extracellular Matrix Gene-Based Prognostic Model to Predict Overall Survive in Patients With Glioblastoma

Background: Glioblastoma (GBM), one of the most prevalent brain tumor types, is correlated with an extremely poor prognosis. The extracellular matrix (ECM) genes could activate many crucial pathways that facilitate tumor development. This study aims to provide online models to predict GBM survival by ECM genes.

Methods: The associations of ECM genes with the prognosis of GBM were analyzed, and the significant prognosis-related genes were used to develop the ECM index in the CGGA dataset. Furthermore, the ECM index was then validated on three datasets, namely, GSE16011, TCGA-GBM, and GSE83300. The prognosis difference, differentially expressed genes, and potential drugs were obtained. Multiple machine learning methods were selected to construct the model to predict the survival status of GBM patients at 6, 12, 18, 24, 30, and 36 months after diagnosis.

Results: Five ECM gene signatures (AEBP1, F3, FLNC, IGFBP2, and LDHA) were recognized to be associated with the prognosis. GBM patients were divided into high– and low–ECM index groups with significantly different overall survival rates in four datasets. High–ECM index patients exhibited a worse prognosis than low–ECM index patients. Four small molecules (podophyllotoxin, lasalocid, MG-262, and nystatin) that might reduce GBM development were predicted by the Cmap dataset. In the independent dataset (GSE83300), the maximum values of prediction accuracy at 6, 12, 18, 24, 30, and 36 months were 0.878, 0.769, 0.748, 0.720, 0.705, and 0.868, respectively. These machine learning models were provided on a publicly accessible, open-source website (https://ospg.shinyapps.io/OSPG/).

Conclusion: In summary, our findings indicated that ECM genes were prognostic indicators for patient survival. This study provided an online server for the prediction of survival curves of GBM patients.

Propofol Prevents the Growth, Migration, Invasion, and Glycolysis of Colorectal Cancer Cells by Downregulating Lactate Dehydrogenase Both In Vitro and In Vivo

Colorectal cancer (CRC) is one of the most frequently diagnosed gastrointestinal malignancies worldwide and has high rates of morbidity and mortality. Propofol has been reported to have certain anticancer properties. However, the role and mechanism of propofol in CRC are not entirely clear. CRC cells were treated with propofol and/or LDH-overexpression plasmids, and a mouse xenograft model of CRC was also established and treated with propofol. Cell viability, migration, and invasion were evaluated by CCK-8, wound healing, and transwell assays; the expression of related proteins was confirmed by western blotting; indexes of the glycolytic pathway were analyzed using specialized kits; tumor growth in mice was measured; pathological tissue structure was assessed by H&E staining; and 8-OHDG expression was determined by an immunochemistry assay. Our results verified that propofol could effectively prevent the malignant behaviors of CRC cells by suppressing cell viability, migration, and invasion and accelerating apoptosis. We also discovered that propofol could attenuate the glycolytic pathway in CRC cells. Moreover, we proved that lactate dehydrogenase (LDH) was required for the inhibitory effects of propofol on the growth of CRC cells, including glycolysis in CRC cells. Furthermore, our results showed that propofol could not only significantly inhibit tumor growth and glycolysis, but also ameliorate the pathological structure of CRC tumors. The current results proved that propofol could attenuate the malignant progression of CRC by preventing LDH activity, suggesting that propofol might be an effective therapeutic agent for CRC.

Comprehensive Analyses of Glucose Metabolism in Glioma Reveal the Glioma-Promoting Effect of GALM

Glioma is the most common tumor with the worst prognosis in the central nervous system. Current studies showed that glucose metabolism could affect the malignant progression of tumors. However, the study on the dysregulation of glucose metabolism in glioma is still limited. Herein, we firstly screened 48 differentially expressed glucose metabolism-related genes (DE-GMGs) by comparing glioblastomas to low-grade gliomas. Then a glucose metabolism-related gene (GMG)-based model (PC, lactate dehydrogenase A (LDHA), glucuronidase beta (GUSB), galactosidase beta 1 (GLB1), galactose mutarotase (GALM), or fructose-bisphosphatase 1 (FBP1)) was constructed by a protein-protein interaction (PPI) network and Lasso regression. Thereinto, the high-risk group encountered a worse prognosis than the low-risk group, and the M2 macrophage was positively relevant to the risk score. Various classical tumor-related functions were enriched by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses. Since protein GALM was rarely studied in glioma, we detected high expression of GALM by western blot and immunohistochemistry in glioma tissues. And experiments in vitro showed that GALM could promote the epithelial-to-mesenchymal transition (EMT) process of glioma cells and could be regulated by TNFAIP3 in glioma cells. Overall, our study revealed the critical role of glucose metabolism in the prognosis of patients with glioma. Furthermore, we demonstrated that GALM was significantly related to the malignancy of glioma and could promote glioma cells' EMT process.

PI3K Pathway Inhibition with NVP-BEZ235 Hinders Glycolytic Metabolism in Glioblastoma Multiforme Cells

Glioblastoma (GBM) is the most lethal primary brain cancer that lacks effective molecular targeted therapies. The PI3K/AKT/mTOR pathway is activated in 90% of all Glioblastoma multiforme (GBM) tumors. To gain insight into the impact of the PI3K pathway on GBM metabolism, we treated U87MG GBM cells with NVP-BEZ235 (PI3K and mTOR a dual inhibitor) and identified differentially expressed genes with RNA-seq analysis. RNA-seq identified 7803 differentially regulated genes in response to NVP-BEZ235. Gene Set Enrichment Analysis (GSEA) identified two glycolysis-related gene sets that were significantly enriched (p < 0.05) in control samples compared to NVP-BEZ235-treated samples. We validated the inhibition of glycolytic genes by NVP-BEZ235 and examined the impact of the FOXO1 inhibitor (AS1842856) on these genes in a set of GBM cell lines. FOXO1 inhibition alone was associated with reduced LDHA expression, but not ENO1 or PKM2. Bioinformatics analyses revealed that PI3K-impacted glycolytic genes were over-expressed and co-expressed in GBM clinical samples. The elevated expression of PI3K-impacted glycolytic genes was associated with poor prognosis in GBM based on Kaplan-Meier survival analyses. Our results suggest novel insights into hallmark metabolic reprogramming associated with the PI3K-mTOR dual inhibition.

A review of gliomas-related proteins. Characteristics of potential biomarkers

Brain tumors are one of the most commonly diagnosed cancers of the central nervous system. Of all diagnosed malignant tumors, 80% are gliomas. An unequivocal diagnosis of gliomas is not always simple, and there is a great need for research to find new treatment options and diagnostic approaches. This paper is focused on the glioma-related protein profiles as compared to healthy brain tissue, which is reflected in multiple correlations between biological aspects that influence proliferation, apoptosis evasion and the invasiveness of neoplastic cells. The work presents the possibilities of facilitating clinical practice with proteomic biomarkers, which offer a wider diagnostic spectrum and reduce the margin of mistake in histopathological or imaging diagnostic methods. In fact, many changes in the body's homeostasis can be overlooked due to the lack of symptoms or their non-specificity. Nevertheless, a single marker has limited reliability in distinguishing a particular tumor subtype, since the increased or decreased level of the protein of interest may differ between the stages or locations of the tumor. Moreover, the correlations between proposed proteins - presented in this paper - may help clinicians to choose the most optimal therapy, and estimate its effectiveness, or indicate new therapeutic targets affecting disrupted biochemical pathways.

Detection of metabolic change in glioblastoma cells after radiotherapy using hyperpolarized 13 C-MRI

Dynamic nuclear polarization (DNP) of 13 C-labeled substrates enables the use of magnetic resonance imaging (MRI) to monitor specific enzymatic reactions in tumors and offers an opportunity to investigate these differences. In this study, DNP-MRI chemical shift imaging with hyperpolarized [1-13 C] pyruvate was conducted to evaluate the metabolic change in glycolytic profiles after radiation of two glioma stem-like cell-derived gliomas (GBMJ1 and NSC11) and an adherent human glioblastoma cell line (U251) in an orthotopic xenograft mouse model. The DNP-MRI showed an increase in Lac/Pyr at 6 and 16 h after irradiation (18% ± 4% and 14% ± 3%, respectively; mean ± SEM) compared with unirradiated controls in GBMJ1 tumors, whereas no significant change was observed in U251 and NSC11 tumors. Metabolomic analysis likewise showed a significant increase in lactate in GBMJ1 tumors at 16 h. An immunoblot assay showed upregulation of lactate dehydrogenase-A expression in GBMJ1 following radiation exposure, consistent with DNP-MRI and metabolomic analysis. In conclusion, our preclinical study demonstrates that the DNP-MRI technique has the potential to be a powerful diagnostic method with which to evaluate GBM tumor metabolism before and after radiation in the clinical setting.

Targeting CDK9 for the Treatment of Glioblastoma

Glioblastoma is the most common and aggressive primary malignant brain tumor, and more than two-thirds of patients with glioblastoma die within two years of diagnosis. The challenges of treating this disease mainly include genetic and microenvironmental features that often render the tumor resistant to treatments. Despite extensive research efforts, only a small number of drugs tested in clinical trials have become therapies for patients. Targeting cyclin-dependent kinase 9 (CDK9) is an emerging therapeutic approach that has the potential to overcome the challenges in glioblastoma management. Here, we discuss how CDK9 inhibition can impact transcription, metabolism, DNA damage repair, epigenetics, and the immune response to facilitate an anti-tumor response. Moreover, we discuss small-molecule inhibitors of CDK9 in clinical trials and future perspectives on the use of CDK9 inhibitors in treating patients with glioblastoma.

The future potential of Annona muricata L. extract and its bioactive compounds as radiation sensitizing agent: proposed mechanisms based on a systematic review

Despite technological advances in cancer treatment, especially in radiotherapy, many efforts are being made in improving cancer cell radio-sensitivity to increase therapeutic ratio and overcome cancer cell radio-resistance. In the present review, we evaluated the anticancer mechanism of Annona muricata L. (AM) leaves extract and its bioactive compounds such as annonaceous acetogenins, annomuricin, annonacin, or curcumin; and further correlated them with the potential of the mechanism to increase or to reduce cancer cells radio-sensitivity based on literature investigation. We see that AM has a promising future potential as a radio-sensitizer agent.

Paclitaxel inhibits the migration of CD133+ U251 malignant glioma cells by reducing the expression of glycolytic enzymes

Energy metabolic reprogramming (EMR) allows for the rearrangement of a series of metabolic genes and proteins when tumor cells adapt to their microenvironment. EMR is characterized by changes in the metabolic pattern and metabolic intermediates to meet the needs of tumor cells for their malignant proliferation and infiltrative growth. The present study investigated the role of low-dose paclitaxel (PTX) in changing the expression levels of key genes and proteins during glycolysis in CD133+ U251 glioma cells and explored the relevant regulatory mechanisms of action at the molecular level. CD133 immunomagnetic beads were applied to malignant CD133+ U251 glioma cells, which were then divided into a negative control and an experimental group treated with 1, 2, 4 or 8 µM PTX for 72 h. Cell Counting Kit-8 (CCK-8) was used to measure U251 cell proliferation. RNA and protein were extracted from the malignant glioma cells in all groups to observe changes in the expression levels of key glycolytic enzymes, such as glucose transporter 1 (GLUT1), pyruvate kinase M (PKM) and lactate dehydrogenase A (LDHA), using reverse transcription-quantitative PCR and western blot assays. Transwell migration assays were performed to quantify the effects of PTX solution on U251 cells. CD133+ U251 glioma cells were isolated successfully. CD1133+ cells had a higher rate of proliferation compared with CD1133- cells. In CD1133+ cells treated with PTX, a dose-dependent reduction in the expression levels of the key glycolytic enzymes GLUT1, PKM and LDHA was observed at both the mRNA and protein levels. PTX solution also inhibited cell migration. Differences between the control and experimental groups were statistically significant (P<0.05). Since glycolysis plays an indispensable role in the proliferation and migration of stem cell-like glioma cells, PTX may inhibit tumor cell growth by downregulating the gene and protein expression levels of glycolytic enzymes in CD133+ glioma cells.

Targeting Glutamine Addiction in Gliomas

The most common malignant brain tumors are those of astrocytic origin, gliomas, with the most aggressive glioblastoma (WHO grade IV) among them. Despite efforts, medicine has not made progress in terms of the prognosis and life expectancy of glioma patients. Behind the malignant phenotype of gliomas lies multiple genetic mutations leading to reprogramming of their metabolism, which gives those highly proliferating cells an advantage over healthy ones. The so-called glutamine addiction is a metabolic adaptation that supplements oxidative glycolysis in order to secure neoplastic cells with nutrients and energy in unfavorable conditions of hypoxia. The present review aims at presenting the research and clinical attempts targeting the different metabolic pathways involved in glutamine metabolism in gliomas. A brief description of the biochemistry of glutamine transport, synthesis, and glutaminolysis, etc. will forego a detailed comparison of the therapeutic strategies undertaken to inhibit glutamine utilization by gliomas.

Novel therapies hijack the blood-brain barrier to eradicate glioblastoma cancer stem cells

Glioblastoma (GBM) is amongst the most aggressive brain tumors with a dismal prognosis. Despite significant advances in the current multimodality therapy including surgery, postoperative radiotherapy (RT) and temozolomide (TMZ)-based concomitant and adjuvant chemotherapy (CT), tumor recurrence is nearly universal with poor patient outcomes. These limitations are in part due to poor drug penetration through the blood-brain barrier (BBB) and resistance to CT and RT by a small population of cancer cells recognized as tumor-initiating cells or cancer stem cells (CSCs). Though CT and RT kill the bulk of the tumor cells, they fail to affect CSCs, resulting in their enrichment and their development into more refractory tumors. Therefore, identifying the mechanisms of resistance and developing therapies that specifically target CSCs can improve response, prevent the development of refractory tumors and increase overall survival of GBM patients. Small molecule inhibitors that can breach the BBB and selectively target CSCs are emerging. In this review, we have summarized the recent advancements in understanding the GBM CSC-specific signaling pathways, the CSC-tumor microenvironment niche that contributes to CT and RT resistance and the use of novel combination therapies of small molecule inhibitors that may be used in conjunction with TMZ-based chemoradiation for effective management of GBM.

Hyperpolarized Pyruvate MR Spectroscopy Depicts Glycolytic Inhibition in a Mouse Model of Glioma

BackgroundA generation of therapies targeting tumor metabolism is becoming available for treating glioma. Hyperpolarized MRI is uniquely suited to directly measure the metabolic effects of these emerging treatments.PurposeTo explore the feasibility of the use of hyperpolarized [1-carbon 13 {¹³C}]-pyruvate for real-time measurement of metabolism and response to treatment with a glycolytic inhibitor in an orthotopic mouse model of glioma.Materials and MethodsIn this animal study, anatomic MRI and dynamic ¹³C MR spectroscopy were performed at 7 T during intravenous injection of hyperpolarized [1-¹³C]-pyruvate on mice with orthotopic U87MG glioma and healthy control mice. Anatomic MRI and dynamic ¹³C MR spectroscopy were repeated after administration of the glycolytic inhibitor WP1122, a prodrug of 2-deoxy-d-glucose. All experiments were conducted in athymic nude mice between October 2016 and March 2017. Hyperpolarized lactate production was quantified as an apparent reaction rate, or k_PL, and normalized lactate ratio (nLac). The Wilcoxon signed-rank test was used to assess changes in paired measures of lactate production before and after treatment.ResultsThirteen 12-16-week-old female mice and five healthy female mice underwent anatomic MRI and hyperpolarized [1-¹³C]-pyruvate spectroscopy. Large contrast agent-enhanced tumors were shown in mice with glioma at T2-weighted and T1-weighted postcontrast MRI by postimplantation day 40. After treatment with WP1122, a decrease in lactate was observed in mice with glioma (baseline and treatment mean k_PL, 0.027 and 0.018 sec^-1, respectively, P = .01; baseline and posttreatment mean nLac, 0.28 and 0.22, respectively, P = .01) whereas no significant decrease was observed in healthy control mice (baseline and posttreatment mean k_PL, 0.011 and 0.017 sec^-1, respectively, P = .91; baseline and posttreatment mean nLac, 0.16 and 0.21, respectively, P = .84).ConclusionHyperpolarized carbon 13 measurements of pyruvate metabolism can provide rapid feedback for monitoring treatment response in glioma.© RSNA, 2019.

Lactate Dehydrogenases as Metabolic Links between Tumor and Stroma in the Tumor Microenvironment

Cancer is a metabolic disease in which abnormally proliferating cancer cells rewire metabolic pathways in the tumor microenvironment (TME). Molecular reprogramming in the TME helps cancer cells to fulfill elevated metabolic demands for bioenergetics and cellular biosynthesis. One of the ways through which cancer cell achieve this is by regulating the expression of metabolic enzymes. Lactate dehydrogenase (LDH) is the primary metabolic enzyme that converts pyruvate to lactate and vice versa. LDH also plays a significant role in regulating nutrient exchange between tumor and stroma. Thus, targeting human lactate dehydrogenase for treating advanced carcinomas may be of benefit. LDHA and LDHB, two isoenzymes of LDH, participate in tumor stroma metabolic interaction and exchange of metabolic fuel and thus could serve as potential anticancer drug targets. This article reviews recent research discussing the roles of lactate dehydrogenase in cancer metabolism. As molecular regulation of LDHA and LDHB in different cancer remains obscure, we also review signaling pathways regulating LDHA and LDHB expression. We highlight on the role of small molecule inhibitors in targeting LDH activity and we emphasize the development of safer and more effective LDH inhibitors. We trust that this review will also generate interest in designing combination therapies based on LDH inhibition, with LDHA being targeted in tumors and LDHB in stromal cells for better treatment outcome.

Cyclin G2 Inhibits the Warburg Effect and Tumour Progression by Suppressing LDHA Phosphorylation in Glioma

Cyclin G2 has been identified as a tumour suppressor in several cancers. However, its regulatory roles and underlying mechanisms in tumours are still unknown. In this study, we demonstrated that cyclin G2 was expressed at low levels in glioma, which was as a poor prognostic factor for this disease. We also found that, cyclin G2 could suppress cell proliferation, initiate cell apoptosis and reduce aerobic glycolysis, suggesting that cyclin G2 plays a tumour suppressive role in glioma. Mechanistically, cyclin G2 could negatively regulate tyrosine-10 phosphorylation of a critical glycolytic enzyme, lactate dehydrogenase A, through direct interaction. Taken together, these results indicate that cyclin G2 acts as a tumour suppressor in glioma by repressing glycolysis and tumour progression through its interaction with LDHA.