The different biological effects of single, fractioned and continuous low dose rate radiations on CL187 colorectal cancer cell line / 中华放射医学与防护杂志

ABSTRACT

Objective To investigate the effect and underlying mechanism of single,fractioned and continuous low dose rate radiation on CL187 colorectal cancer cell line.Methods CL187 cells were exposed to 6 MV X-rays at a high dose rate of 4 Gy/min and 125Ⅰ seed at a low dose rate of 2.77 cGy/h with three groupssingle dose radiation group (SDR),fractioned dose radiation group (FDR) by 2 Gy/f,and continuous low dose rate radiation group (CLDR).The radiation doses were 0,2,4 and 8 Gy.Total cell number and cell viability were determined by trypan blue.Clone forming assay was used to evaluate the cell proliferation ability.The percentage of apoptosis cells was analyzed by flow cytometry.Western blot was used to detect the protein expression levels of PHLPP2,PTEN and Bax.Results Compared with SDR and FDR groups,the total cell number and survival fraction of CLDR group decreased.The relative biological effect (RBE) for 125Ⅰ seeds compared with 6 MV X-rays was 1.41.The percentage of apoptosis cells of CLDR group was significantly increased (t =-15.08,-11.99,P ＜ 0.05).The expression level of Bax increased in CLDR group,while no obvious changes were observed on PHLPP2 and PTEN among three groups.Conclusions The expression level of PHLPP2 increaseS in SDR,FDR and CLDR group,while it seems that it was not influenced by dose rate.The expression level of Bax increased in three groups,while more colorectal CL187 cells in CLDR group may be killed due to the increase of Bax expression.