Cell cycle distribution and radiosensitivity of mouse mammary carcinoma derived cell line SX-9

Objective To investigate cell cycle distribution of radiosensitive cell line SX-9 after X-ray irradiation and the relationship between radiosensitivity and cell cycle distribution. Methods The survival fraction of SX-9 to SR-1 was compared with clonegenic assay,cell cycle distribution and p53 gene status were investigated with FCM and RT-PCR respectively. Results SX-9 is radiosensitive compared with its parental cell line SR-1. Because of its p53 mutation in exson 5,only G 2 arrest was found in SX-9 cell line .Apoptosis was not observed in either of these two cell lines after DNA electrophoresis,flow cytometry and trypan blue staining. Conclusions Irradiation of serum-starved synchronous cells show a prolonged delay in G 2 for radiosensitive cell line SX-9 and in G 1 and G 2 for its parental cell line SR-1,whereas no differences are found in DNA electrophoresis,flow cytometry and trypan blue staining between these two cell lines. It implicates the deficiency in the rejoining of DNA DSB during G 2-phase delay as a possible cause for its radiosensitivity,although the mechanism is not fully understood.