A Lentiviral For Down-regulated Mi RNA-21 Regulate Aerobic Glycolysis In Bladder Cancer Cells

Bladder cancer, primarily urothelial cell carcinoma, is the second most common genitourinary malignancy that leads to significant morbidity and mortality. Among them, 70% of patients presenting non-muscle invasive tumors and 10% ~ 30% presenting muscle-invasive disease associated with a poor prognosis from distant metastases. In recent years, despite the rapidly developed surgery, the long-term recurrence rate and survival rate of patients did not improve. Other therapies include chemotherapy and radiotherapy are lack of specificity with obvious side effects. Therefore, further study on molecular mechanism of bladder cancer is necessary. MicroRNAs(miRNAs) are short noncoding RNAs, 18 to 25 nucleotides in length, which regulate gene expression through complementary with 3’UTR(3’-untranslated region) of their target mRNAs. The mi RNA-mediated regulation of gene expression could be either by post-transcriptional regulation of gene expression leading to target mRNA degradation or repression of its translation with consequent decrease in the particular protein levels.Normal cells metabolise glucose by mitochondrial oxidative phosphorylation to maximise ATP production. Furthermore, normal cells produce large amounts of lactate and some ATP only under anaerobic conditions. Glycolytic pathway only generates two ATP, but efficiently and easily. However, tumour cells ferment glucose to produce lactate and support mitochondrial oxidative phosphorylation regardless of the presence or absence of oxygen. This is referred to as the Warburg effect and was first observed by Otto Warburg in the 1920 s. Several lines of evidence implicate altered miRNA regulation in aerobic glycolysis of cancer cells. However, the specific mechanism between mi RNA and aerobic glycolysis is still unclear. In the present study, functional analyses were conducted to investigate the role of miR-21 in aerobic glycolysis in bladder cancer cells.We used a lentivirus vector to knock down miR-21 expression in T24 cells and found that miR-21 knock-down could represses cell proliferation with the reduction of glucose uptake, lactate secretion, hexokinase activity and increasing sensitivity to 2-DG in those cells. Our results indicated that the expression levels of key glycolytic protein in bladder tumour tissues were higher than those in adjacent tissues. Further results also showed that the protein levels of glycolytic regulators in miR-21 knockdown cells were lower than those in miR-21 control cells. In the present study, miR-21 inhibition could enhance PTEN protein level and inhibit AKT phosphorylation and deactivate mTOR with down-regulated expression of p-4EBP1 and p-S6 K protein expressions. Above all, our findings suggest that miR-21 acts as a molecular switch to regulate aerobic glycolysis in bladder cancer cells probably via the PTEN/PI3K/AKT/mTOR pathway. Blocking miR-21 function can be an effective diagnostic and therapeutic approach either by itself or in combination with existing methods to treat bladder cancer.