Effect of Cyclin G1 on Radiosensitivity of Hepatocellular Carcinoma HepG2 Cells and Its Mechanism

Objective To investigate the effect of Cyclin G1 on the radiosensitivity of hepatocellular carcinoma HepG2 cells and its possible mechanism.

Methods HepG2-Cyclin G1-siRNA cells was constructed through the transfection of Cyclin G1-siRNA to HepG2 cells, and the effect of Cyclin G1 on radiosensitivity of HepG2 cells was observed. Flow cytometry was used to monitor the change of cell cycle. The expression of hypoxia-inducible factor-1α(HIF-1α) and ROS were detected by ELISA analysis, and Western blot was used to detect the expression of Bcl-2 and Bax.

Results q-PCR showed the expression of Cyclin G1 in HepG2-Cyclin G1-siRNA cells was decreased to 43.5% of normal control group. Clone formation analysis showed that Cyclin G1-siRNA could increase the radiosensitivity of HepG2 cells, SER_Dq=1.41, compared with normal control group. Flow cytometry analysis showed that the cells in G₂/M phase were increased and the cells in G₀/G₁ phase were decreased in HepG2-Cyclin G1-siRNA cells. ELISA analysis showed that the HIF-1α of HepG2 cells could be induced by X-ray irradiation, while Cyclin G1-siRNA could cause a significant decrease in the content of HIF-1α. ROS content in X-ray-irradiated cells showed mild increase, with no significant difference. Cyclin G1-siRNA could increase the content of ROS, moreover, the change was more significant when it combined with X-ray radiation. Western blot showed that X-ray irradiation and Cyclin G1-siRNA could decrease the expression of BCL-2 and increase the expression of Bax, and the changes of HepG2-Cyclin G1-siRNA combined with X-ray irradiation group were the most obvious.

Conclusion Cyclin G1-siRNA could upregulate the radiosensitivity of hepatocellular carcinoma cell line HepG2, and its mechanism may be related to the regulation of HIF-1, ROS and apoptosis-related proteins expressions.