Effect of long intergenic noncoding RNA-p21 knockdown on radiosensitivity of hypoxic tumor cells

Abstract

Objective To investigate the effect and mechanisms of lincRNA-p21 knockdown on radiosensitivity of hypoxic tumor cells. Methods The expression of lincRNA-p21 in SMMC7721 and U251MG cells after hypoxia treatment were detected by QRT-PCR. Lentivirus vector carrying lincRNA-p21 siRNA or scrambled oligos were constructed. SMMC7721 and U251MG cells with stable integration of lincRNA-p21 siRNA or scrambled sequence were generated through lentiviral-mediated gene transfer. Cell cycle and apoptosis of hypoxic tumor cells were analyzed by flow cytometry. Radiosensitivity of hypoxic tumor cells were measured by cloning formation assay. The expressions of HIF-1α and GLUT1 protein were detected by Western blot. Results Under hypoxia condition (1%O2) for 24 and 48 h, lincRNA-p21 strongly increased (t=5.13, 7.49, 8.90, 10.11, P<0.05) in SMMC7721 and U251MG cells in a time-dependent manner, but this increase was suppressed in the SMMC7721 and U251MG cells with stable integration of lincRNA-p21 siRNA (t=144.81, 334.32, P<0.05). When SMMC7721 and U251MG cells were cultured under hypoxia condition (1%O2) for 48 h, knockdown of lincRNA-p21 induced G2/M phase arrest (t=7.05, 10.18, P<0.05) and apoptosis (t=42.27, 24.79, P<0.05), reduced the expressions of HIF-1α and GLUT1 protein, and enhanced radiosensitivity with a radiosensitization ratio of 1.23 and 1.31, respectively. Conclusions Hypoxia treatment elevate the expression of lincRNA-p21. Knockdown of lincRNA-p21 enhance radiosensitivity of hypoxic tumor cells accompanied with G2/M phase arrest, apoptosis induction and the decrease of HIF-1α protein expression. Key words: lincRNA-p21; Hypoxia; Cell cycle arrest; Cell apoptosis; Radiosensitivity