Hypoxia in the microenvironment promotes glycolysis to aggravate tumor progression via modulating the lincRNA-p21 and its downstream genes in HCC

IntroductionLincRNA-p21 was found to inhibit hepatic stellate cell (HSC) activation and liver fibrosis via a signaling cascade of lincRNA-p21-miR-181b-PTEN. Hypoxia was also previously proved to regulate hepatocellular carcinoma (HCC) glycolysis by targeting HK2.Material and methodsLuciferase assay was carried out to examine the regulatory role of miR-181b in lincRNA-p21 and HK2 expression. Quantitative real-time PCR was performed to measure the expression of lincRNA-p21, miR-181b and HK2 mRNA. Western blot and immunohistochemistry were used to analyze the expression of HK2 protein.ResultsThe expression of lincRNA-p21 and HK2 was effectively suppressed by miR-181b in Hep3B and HepG2 cells. Besides, the luciferase activities of wild type lincRNA-p21 and HK2 were remarkably suppressed by miR-181b in Hep3B and HepG2 cells. Activation and suppression of lincRNA-p21 expression using pcDNA and shRNA revealed a negative correlation between miR-181b and lincRNA-p21 expression as well as a positive correlation between HK2 and lincRNA-p21 expression. Moreover, lincRNA-p21 shRNA could effectively reverse the effect of hypoxia-induced dysregulation in miR-181b and HK2 expression, as well as the altered levels of glucose consumption and lactate production in Hep3B and HepG2 cells. Furthermore, lincRNA-p21 was capable of altering the growth and miR-181b/HK2 expression of HepG2 xenograft tumors in nude mice.ConclusionsOur study investigated the molecular relationship between lincRNA-p21, miR-181b and HK2 in cellular and animal models, and validated that hypoxia could up-regulate the expression level of lincRNA-p21 in the microenvironment of solid hepatocellular carcinoma tumor, which accordingly led to aggravated glycolysis via elevated HK2 expression, thus inhibiting the apoptosis of HCC.