The Enhancement Of Irradiation To Cervical Cancer Cells By Topotecan

The Enhancement of Irradiation to Cervical Cancer Cells by TopotecanIntroductionTopotecan is DNA Topoisomerase I inhibitor, which can combine with DNA Topoisomerase I and form stable compund. Then it keep DNA double- strand break from repair and cause cells die. At present, Topotecan has some antitumor effect, not only for ovarian cancer, colon cancer, lung cancer, but also for advanced cervical cancer concurrently combined with radiotherapy and chemotherapy. In vitro research, it indicated that, Topotecan, which can inhibit many tumor cells obviously, is one kind of effective radiation sensitizing agents. Though the radiosensitizing effect of Topotecan on nasopharygeal carcinoma and lung cancer has been reported, the effect on cervical cancer is seldom investigated. This study is To investigate the radiosensitization effect and cell cycle effect of Topotecan on cervical carcinoma cell line HeLa.Materials and Methods1. After obtaining IC50 of Topotecan on Hela cells through MTT, we exposed Hela cells to Topotecan in 8 concentrations(less than IC50) in 24 hours which were assigned to 8 groups. X-rays(6MV) were given with single dose by accelerator. The cell survival cures and SERS(sensitive enhancement ratio) were obtained with clonogenic assay and single-hit multitarget model after analysis with Graphpad prism 4 Demo software.2. Cell cycles were calculated by flow cytometry.3. Statistical analysisThe expenment was done twice. Statistical analysis was performed by ANOVA using SPSS13.0 software, Statistical significance was defined as P＜0.05.Results1. The SERs of Topotecan of different concentrations in combination with radiotherapy were 1.09, 1.31, 1.37, 1.48, 1.45, 1.46, 1.50 respectively.2. Topotecan caused G₂/M blocking within cell cycle. G₂/M phrase ratio enhanced 4 hours, 24 hours, 48 hours after irradiation(P=0.005,0.015,0.023, respectively).Discussions1. In this study, it shows that, when the concentration of Topotecan is no more than 8ug/ml, SER enhances as the concentration of Topotecan, 1.09, 1.31, 1.37, 1.48; when the concentration is more than 20ï¼…IC50(≥12ug/ml), SER changes little, which indicates its cytotoxicity increasing. The radiosensitization of Topotecan is better in low concentrations(≤20ï¼…IC50).2. Irradiation may lead to DNA double-strand break, affect cell cycle, and cause G₁ phase,G₂/M phase or S phase arrest. This experiment indicated that Topotecan caused Hela cells G₂/M phase blocking. The P value was 0.005, 0.015, 0.023, separately, 4 hours, 24 hours, 48 hours after irradiation. The redistributing effect of Topotecan on Hela cells is much obvious in early stage (4 hours).ConclusionsTopotecan has some effects on radiosensitivity in cervical carcinoma cell line Hela. Topotecan caused G₂/M phrase arrest.