Establishment of radioresistant human cervical cancer cells and the differential expression of DNA damage repair-related genes.

Objective To screen the differential expression of DNA damage repair-related genes between the different radioresistant cervical cancer cells to investigate radiation tolerance mechanism of cervical cancer. Methods A radioresistant cell line, SiHaR, was established from a human cervical squamous carcinoma cell line SiHa by repeated high-dose 9MeV-ß irradiation. The differential gene expressions were screened with cDNA microarray by DNA damage repair-related gene chip. Portions of differential genes screened were confirmed by Western blotting. Results The SiHa and SiHaR cells were exponentially killed after irradiation. The survival fraction (SF) value of SiHaR cells was higher at the same dose irradiation. As to SF2, the radioresistance of SiHaR cells was 2.26 times that of SiHa cells. Totally 41 DNA damage repair-related genes with differential expressions were screened out between radioresistant SiHaR cell line and its parental SiHa cell line, with 27 up-regulated and 14 down-regulated genes. Among them, there were 13 genes whose ratio was higher than 6.0 or lower than 0.1. Western blot prompted to verify the results of four differentially expressed proteins compared with SiHa cells, in which the expression levels of ras-related associated with diabetes (RRAD1) and replication factor C2 (RCF2) were significantly down-regulated in SiHaR, while the expressions of X-ray repair complementing defective repair (XRCC1) and excision repair cross-complementing (ERCC1) at the protein level were significantly up-regulated. Conclusion A stable radioresistant cell line denoted by SiHaR and induced from the SiHa cell line was successfully isolated by repeated high-dose 9MeV-ß irradiation. The radioresistance of cervical cancer is significantly related to gene mutation that occurs in DNA damage repair after exposure to irradiation, which provides several gene targets for sensitizing the radioresistant cells for improving the radiocurability of cervical cancer. [ABSTRACT FROM AUTHOR]