Digging deeper through glucose metabolism and its regulators in cancer and metastasis

Quantification of 2-NBDG, a probe for glucose uptake, in GLUT1 overexpression in HEK293T cells by LC-MS/MS

The growth and proliferation of most cancer cells involve the excessive uptake of glucose mediated by glucose transporters. An effective strategy for cancer therapy has been to inhibit the GLUTs that are usually overexpressed in a variety of tumor cells. 2-NBDG is a GLUT1 substrate that can be used as a probe for GLUT1 inhibitors. An accurate and simple assay for 2-NBDG in a HEK293T cell model overexpressing GLUT1 was developed using liquid chromatography-tandem mass spectrometry. Chromatographic separation was achieved using a Xbridge® Amide column (3.5 μm, 2.1 mm × 150 mm, Waters) with acetonitrile-water containing 2 μM ammonium acetate (80:20, v/v) at a flow rate of 0.25 mL/min. Mass detection was conducted in the parallel reaction monitoring (PRM) mode. The calibration curve for 2-NBDG showed good linearity in the concentration range of 5-500 ng/mL with satisfactory precision, a relative standard deviation ranging from 2.92 to 9.59% and accuracy with a relative error ranging from -13.14 to 7.34%. This method was successfully applied to quantify the uptake of GLUT1-mediated 2-NBDG, and the results clearly indicated inhibition of GLUT1 by WZB117 and quercetin (two potent glucose transporter inhibitors) in the GLUT1-HEK293T cell model. This study provides a convenient and accurate method for high-throughput screening of selective and promising GLUT1 inhibitors.

Glucose Metabolism and Glucose Transporters in Breast Cancer

Breast cancer is the most common malignancy in women worldwide and is associated with high mortality rates despite the continuously advancing treatment strategies. Glucose is essential for cancer cell metabolism owing to the Warburg effect. During the process of glucose metabolism, various glycolytic metabolites, such as serine and glycine metabolites, are produced and other metabolic pathways, such as the pentose phosphate pathway (PPP), are associated with the process. Glucose is transported into the cell by glucose transporters, such as GLUT. Breast cancer shows high expressions of glucose metabolism-related enzymes and GLUT, which are also related to breast cancer prognosis. Triple negative breast cancer (TNBC), which is a high-grade breast cancer, is especially dependent on glucose metabolism. Breast cancer also harbors various stromal cells such as cancer-associated fibroblasts and immune cells as tumor microenvironment, and there exists a metabolic interaction between these stromal cells and breast cancer cells as explained by the reverse Warburg effect. Breast cancer is heterogeneous, and, consequently, its metabolic status is also diverse, which is especially affected by the molecular subtype, progression stage, and metastatic site. In this review, we will focus on glucose metabolism and glucose transporters in breast cancer, and we will additionally discuss their potential applications as cancer imaging tracers and treatment targets.

Circ-RPPH1 knockdown retards breast cancer progression via miR-328-3p-mediated suppression of HMGA2

BACKGROUND

Circular RNA Ribonuclease P RNA Component H1 (circ-RPPH1) was confirmed to act as an oncogene in many cancers to promote cancer progression. However, the exact function and mechanism of circ-RPPH1 in breast cancer (BC) remain vague.

METHODS

The expression of circ-RPPH1, microRNA (miR)-328-3p and high-mobility group AT-hook 2 (HMGA2) was detected using quantitative real-time polymerase chain reaction and western blot. Cell viability, apoptosis, migration and invasion were determined using cell counting kit-8 assay, flow cytometry and transwell assay, respectively. Glucose metabolism was calculated by detecting glucose uptake and lactate production. The target correlations between miR-328-3p and circ-RPPH1 or HMGA2 were confirmed by dual-luciferase reporter assay. The murine xenograft model was established to conduct in vivo experiments.

RESULTS

Circ-RPPH1 expression was elevated and miR-328-3p was decreased in BC tissues and cells. Circ-RPPH1 knockdown or miR-328-3p re-expression suppressed cell proliferation, migration, invasion and glycolysis but induced apoptosis in BC in vitro. Circ-RPPH1 was a sponge of miR-328-3p, and silencing of miR-328-3p reversed the inhibitory effects of circ-RPPH1 knockdown on BC cell malignant phenotypes and glycolysis. MiR-328-3p directly targeted HMGA2, and HMGA2 overexpression abolished the action of miR-328-3p in BC cells. Besides, circ-RPPH1 could regulate HMGA2 expression by miR-328-3p in BC cells. Moreover, murine xenograft model analysis suggested circ-RPPH1 knockdown inhibited tumor growth in vivo.

CONCLUSION

Circ-RPPH1 knockdown retarded cell malignant phenotypes and glycolysis via miR-328-3p/HMGA2 axis in BC, providing a potential therapeutic target for BC treatment.

Prevalence of Human Polyomavirus BK Virus in Prostate Cancer Patients and Benign Prostatic Hyperplasia: A Cross-sectional Study on Prostate Patients Referred to Imam Khomeini Hospital in Ahvaz Between 2015 and 2017

Background: Human polyomavirus BK virus (BKV) belongs to the Polyomaviridae family and seems to be a drastic virus in prostate cancer (PCa) etiology. BK virus induces oncogenesis via the expression of large tumor antigen (LTAg) and small tumor antigen (stAg). Also, BKV infection seems to play an essential role in prostate cancer development. Objectives: In this study was aimed to study the prevalence of BKV in benign and cancerous prostate tissues. Methods: In this study, 100 formalin-fixed paraffin-embedded tissues of PCa specimens and benign prostatic hyperplasia (BPH) were collected. The DNA was extracted from tissue samples, and the BKV DNA was investigated using a semi-nested polymerase chain reaction (PCR). The MEGA 6.0 software was used for phylogenetic analysis to assemble the viral genome. A phylogenetic tree was constructed by neighbor-joining analysis with 1,000 replicates of the bootstrap resampling test. Results: The BKV DNA was found in 66% (33/50) of patients with PCa and 36% (18/50) of patients with benign prostatic hyperplasia (BPH) (P = 0.003). The frequency of BKV DNA in different classes of Gleason score (5 - 10) was not significant (0.094). The distribution of BKV DNA among different age groups was not significant (P = 0.086). Conclusions: High frequency of BKV infection was detected in patients with PCa compared to patients with BPH (P = 0.003), and the coexistence of BKV DNA was confirmed in 51% (51/100) of tissue samples, which were confirmed to be subtype 1 of BKV infection.

Recent advancements in therapeutic targeting of the Warburg effect in refractory ovarian cancer: A promise towards disease remission

Epithelial ovarian cancer, the most lethal gynecological malignancy, is diagnosed at advanced stage, recurs and displays chemoresistance to standard chemotherapeutic regimen of taxane/platinum drugs. Despite development of recent therapeutic approaches including poly-ADP ribose polymerase inhibitors, this fatal disease is diagnosed at advanced stage and heralds strategies for early detection and improved treatment. Recent literature suggests that high propensity of ovarian cancer cells to consume and metabolize glucose via glycolysis even in the presence of oxygen (the 'Warburg effect') can significantly contribute to disease progression and chemoresistance and hence, it has been exploited as novel drug target. This review focuses on the molecular cues of aberrant glycolysis as drivers of chemo-resistance and aggressiveness of recurrent ovarian cancer. Furthermore, we discuss the status quo of small molecule inhibition of aerobic glycolysis and significance of metabolic coupling between cancer cells and tumor microenvironment as novel therapeutic interventions against this lethal pathology.

Mechanisms of Metabolic Reprogramming in Cancer Cells Supporting Enhanced Growth and Proliferation

Cancer cells alter metabolic processes to sustain their characteristic uncontrolled growth and proliferation. These metabolic alterations include (1) a shift from oxidative phosphorylation to aerobic glycolysis to support the increased need for ATP, (2) increased glutaminolysis for NADPH regeneration, (3) altered flux through the pentose phosphate pathway and the tricarboxylic acid cycle for macromolecule generation, (4) increased lipid uptake, lipogenesis, and cholesterol synthesis, (5) upregulation of one-carbon metabolism for the production of ATP, NADH/NADPH, nucleotides, and glutathione, (6) altered amino acid metabolism, (7) metabolism-based regulation of apoptosis, and (8) the utilization of alternative substrates, such as lactate and acetate. Altered metabolic flux in cancer is controlled by tumor-host cell interactions, key oncogenes, tumor suppressors, and other regulatory molecules, including non-coding RNAs. Changes to metabolic pathways in cancer are dynamic, exhibit plasticity, and are often dependent on the type of tumor and the tumor microenvironment, leading in a shift of thought from the Warburg Effect and the “reverse Warburg Effect” to metabolic plasticity. Understanding the complex nature of altered flux through these multiple pathways in cancer cells can support the development of new therapies.

Vitamin D regulation of energy metabolism in cancer

Vitamin D exerts anti-cancer effects in recent clinical trials and preclinical models. The actions of vitamin D are primarily mediated through its hormonal form, 1,25-dihydroxyvitamin D (1,25(OH)₂ D). Previous literature describing in vitro studies has predominantly focused on the anti-tumourigenic effects of the hormone, such as proliferation and apoptosis. However, recent evidence has identified 1,25(OH)₂ D as a regulator of energy metabolism in cancer cells, where requirements for specific energy sources at different stages of progression are dramatically altered. The literature suggests that 1,25(OH)₂ D regulates energy metabolism, including glucose, glutamine and lipid metabolism during cancer progression, as well as oxidative stress protection, as it is closely associated with energy metabolism. Mechanisms involved in energy metabolism regulation are an emerging area in which vitamin D may inhibit multiple stages of cancer progression.

The role of IGF2BP2, an m6A reader gene, in human metabolic diseases and cancers

The human insulin-like growth factor 2 (IGF2) mRNA binding proteins 2 (IGF2BP2/IMP2) is an RNA-binding protein that regulates multiple biological processes. Previously, IGF2BP2 was thought to be a type 2 diabetes (T2D)-associated gene. Indeed IGF2BP2 modulates cellular metabolism in human metabolic diseases such as diabetes, obesity and fatty liver through post-transcriptional regulation of numerous genes in multiple cell types. Emerging evidence shows that IGF2BP2 is an N6-methyladenosine (m6A) reader that participates in the development and progression of cancers by communicating with different RNAs such as microRNAs (miRNAs), messenger RNAs (mRNAs) and long non-coding RNAs (lncRNAs). Additionally, IGF2BP2 is an independent prognostic factor for multiple cancer types. In this review, we summarize the current knowledge on IGF2BP2 with regard to diverse human metabolic diseases and its potential for cancer prognosis.