Radiosensitization And Inhibition Of Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitor Gefitinib On Cervical Carcinoma In Vitro

Objective:To investigate the inhibition and radiosensitization of a selective epidermal growth factor receptor tyrosine kinase inhibitor gefitinib on cervical carcinoma cells in vitro and its possible mechanismsMethods:The effect of gefitinib on cervical carcinoma cells (Siha, Hela) was determined by MTT assay. The effect of gefitinib combined with cisplatin (DDP) on cervical carcinoma cells was also evaluated. Burgi formula was adopted to analyze the combination effect. The cells were divided into four groups: (1) the control: without gefitinib and radiation; (2) radiation alone:6MV X-ray radiation at a dose of 1,2,3,4,6 or 8Gy, respectively; (3) gefitinib alone: gefitinib (IC20)) were exposed to cells for 72h; (4) gefitinib combined radiation: After 6MV X-ray radiation was given at a dose of 1,2,3,4,6 or 8Gy, cells were exposed to gefitinib (IC20)) for 72h, respectively.Cells were assayed for clonogenic survival to determine the radiosensitizing effect of gefitinib. Calculating the sensitization enhancement ratio SER. In clonogenic assay, all data for gefitinib combined radiation group should be rectified by that of gefitinib alone to exclude its cytotoxity. Western Blot analysis was used to measure expression of P-Erk, P-Akt, CyclinD1, bcl-xL proteins in Siha and Hela cell lines. In addition, the distribution of cell cycle and cell apoptosis rate were analyzed by flow cytometry.Results:1. The proliferation of cervical carcinoma cell lines (Siha, Hela) was inhibited by gefitinib,and the effect was dose-dependent. The value of IC50 for the effect of gefitinib on cervical carcinoma cell lines (Siha, Hela) was 1.48umol/L and 2.67umol/L respectively.2. Gefitinib could enhance the effect of DDP on Siha and Hela cells. The Q values by Burgi formula were 1.06±0.03 and 1.13±0.01 respectively.3. When exposed to gefitinib for 72h, the SER of Siha and Hela cells was 1.693 and 1.228 respectively.4. The level of P-Erk, P-Akt,Cyclin D1,bcl-xL expression was decreased by gefitinib.5. Flow cytometry analysis showed that gefitinib induced accumulation of G0/G1 phase and increased apoptosis in Siha and Hela cells.Conclusion:1. Gefitinib inhibits the proliferation of cervical carcinoma cells and enhances the effect of DDP. Gefitinib induces cervical carcinoma cells (Siha, Hela) cell cycle arrest in the G1 phase and induce cell apoptosis.2. The radiosensitization of cervical carcinoma cells induced by gefitinib may be associated with accumulation of G0/G1 phase and increased apoptosis rate, and decreased expression of P-Erk, P-Akt,Cyclin D1,bcl-xL proteins.