Effect of RNaseH-1 on inhibition of telomerase-negative osteosarcoma and enhancement of radiosensitivity / 中华放射肿瘤学杂志

ABSTRACT

Objective:To investigate the effect and mechanism of RNaseH-1 on the radiosensitivity of the osteosarcoma cells via the alternative lengthening of telomeres (ALT) mechanism to maintain the telomere length.Methods:ALT osteosarcoma cell U2OS and telomerase-positive osteosarcoma cell 143B over-expressing RNaseH-1 were constructed by lentiviral transfection. After cell transfection, cell proliferation and cell cycle were determined using CCK-8 assay and flow cytometry. The effect of RNaseH-1 on the radiosensitivity of osteosarcoma cells was examined by colony formation assay. DNA injury (γ-H 2AX foci) was assessed by immunofluorescent assay. The expression levels of related proteins were detected by Western blot. Results:The proliferation abilities of U2OS cells were significantly declined following the over-expression of RNaseH-1, and G 1 cell cycle arrest was noted (all P<0.05). Over-expression of RNaseH-1 in U2OS cells increased the phosphorylated levels of ATM and Chk 2, down-regulated the expression of homologous recombination (HR)-related proteins RAD51 and BRCA1significantly aggravated DNA damage and remarkably enhanced the radiosensitivity (all P<0.05). Over-expression of RNaseH-1 exerted no inhibitory effect upon the telomerase-positive 143B cells ( P>0.05). Conclusion:RNaseH-1 over-expression suppresses telomerase-negative osteosarcoma cells and enhances the radiosensitivity probably via the role of RNaseH-1 in inhibiting the homologous recombination repair and activating the ATM signaling pathway.