Alteration of DNA damage signaling pathway profile in radiation-treated glioblastoma stem-like cells.

The present study aimed to investigate the alteration of the DNA damage signaling pathway profile in radiation-treated glioblastoma stem-like cells (GSLCs), and also aimed to explore potential targets for overcoming glioblastoma radioresistance. Serum-free medium was used to isolate and culture GSLCs. Cell growth was detected using a cell counting kit-8 assay and cell sorting analysis was performed by flow cytometry. X-ray irradiation was produced by a Siemens-Primus linear accelerator. Reverse transcription-quantitative polymerase chain reaction (qPCR)was performed to investigate target genes. SPSS 15.0 was used for all statistical analyses. Human glioblastoma U251 and U87 cells were cultured in serum-free medium supplemented with epidermal growth factor and fibroblast growth factor 2, which constitutes tumor sphere medium, and demonstrated sphere formation, with significantly increased the proportion of CD133+ and Nestin+ cells, which are referred to as GSLCs. The present data revealed that treatment with 10 Gy X-ray radiation alters the expression profile of DNA damage-associated genes in GSLCs. The expression levels of 12 genes demonstrated a ≥2-fold increase in the irradiated U87 GSLCs compared with the untreated U87 GSLCs. Three genes, consisting of XPA, RAD50 and PPP1R15A, were selected from the 12 genes by gene functional searching and qPCR confirmatory studies, as these genes were considered to be potential targets for overcoming radioresistance. The expression of XPA, RAD50 and PPP1R15A is significantly increased in U87 and U251 radiation resistant GSLCs, indicating three potential targets for overcoming the radioresistance of GSLCs.