In Vitro Studies Of Radiosensitizing Effect Of Catechine On Human Hepatocellular Cacinoma Cell Lines

Objectives:The studies aimed to evaluate the influence of catechine on radiosensitivity of human hepatocellular carcinoma cell lines cultured in vitro.Firstly,we tried to find out if catechine could increase the radiosensitivity of two human hepatocellular carcinoma cell lines and whether there were any differences between the effect of various density of catechines.Secondly,We tried to postulate the possible mechanisms of radiosensitizing effect of catechine. Materials and methods: (1 )A human hepatocellular carcinoma cell line -HepG2 was used to evaluate the combined cytotoxicity effect of catechine and 2Gy X-ray irradiation by means of trypan blue exclusion and the tetrazolium salt MTT method.The cell survival was evaluated using a standard colony-forming assay to study the sensitizing effect of catechine on two hepatocarcinoma cell lines- HepG2 and BEL-7402.Survival curves were fitted to the data using the multitarget model and the values for D0,Dq and SF2 were calculated.The sensitizing enhancement ratio for each catechine pretreatment was calculated at the I 0%survival level. (2)The apoptotic ratio of the two cell lines after 5Gy X-ray radiation with or without pretreatment of catechine were determined with hematoxylin- elosin (HE) staining and flow cytometry(FCM).The expression level of bcl-2 and Bax protein before and after exposure of the two cell lines to catechine were investigated by immunohistochemical method and flow cytometry. Results: (1 )The results by using trypan blue exclusion and the tetrazolium salt MTT method showed that catechine could decrease the surviving cells radiated by 2Gy X-ray on an attitude of density and time-dependent. Colony- forming assay results showed that catechine enhanced the radiosensitivity of the two cell lines.The SER at the 10% suevival level were 1.25 and 1 ,S4for HepG2 cell lines of I it g/ml and 10 i-i g/ml catechine respectively, 1.21 and 1.62 for BEL-7402 cell lines of 1 ii g/ml and 10 i-i g/ml catechine respectively. (2)Compared to 5Gy X-ray radiation alone,the apoptotic rate of the two 4 cell lines was higher when cells were pretreated with 1 10 1.i g/ml catechine. The results by immunohistochemical method and flow cytometry demonstrated that the expression of bcl-2 protein gradually down- regulated ,contrarily,that of the Bax protein reversed after the treatment of the two cell lines with catechines. Conclutions: (1)Catechine could increase the radiosensitivity of human hepatocarcinoma cell lines-HepG2 and BEL-7402. (2)Catechine was able to enhance the effect of the two cell lines to radiation through increasing apoptotic rate of cells induced by radiation through modulating the expression of bcl-2 and Bax protein.