Radiation-inducible PTEN expression radiosensitises hepatocellular carcinoma cells

Abstract

Purpose: To test the radiosensitising effects of a tumour-suppressor gene, phosphatase and tensin homologue deleted from chromosome 10 (PTEN), in hepatocellular carcinoma cells (HCC).Materials and methods: Radiation-induced wild-type PTEN or mutant PTEN was transfected into the SMMC-7721 human hepatocellular carcinoma cells. The expressions of PTEN and serine/threonine protein kinase (Akt) were detected by Western blot analysis. 3-(4,5)-dimethylthiahiazo-(-z-y1)- 3,5-di-phenytetrazoliumromide (MTT) absorbance and clonogenic survival assays were used to determine cell viability, proliferation and radiosensitivity. By performing cell-cycle analysis, terminal deoxynucleotidyltransferase (TdT)-mediated dUTP biotin nick end labelling (TUNEL) assays and gamma-histone H2A (γ-H2AX) formation assays, we were able to explore the mechanism of PTEN enhancement of radiosensitivity.Results: Restoration of wild-type PTEN induced growth suppression and sensitised the cells to ionising radiation specifically by its lipid phosphatase activity through the PTEN-phosphatidylinositol 3-kinase (PI3K)-Akt signalling pathway. Restoring PTEN function correlated with G2/M arrest, apoptosis and the retardation of repair of radiation-induced double strand breaks (DSB).Conclusions: Our study suggests that strategies designed to restore the expression of PTEN may represent promising new therapies for sensitising HCC cells to ionising radiation.