Regulation of c-Myc and NBS1 by ionizing radiation in glioblastoma cells

Glioblastoma is the most common primary brain tumor presenting the worst prognostic. Radioresistance of these tumors is barrier to better treatment and management. Cellular response to ionizing radiation (IR) depends on various molecular mechanisms, including transcription of DNA damage response genes in response to oncogenes. Previous studies suggested that the radioresistance of glioma stem cells would be associated with c-Myc-dependent upregulation of NBS1. The purpose of this study was to evaluate whether IR and other DNA-damaging agents co-regulate c-Myc and NBS1 in glioblastoma cell lines. We found that c-Myc protein level is downregulated by IR in specific glioblastoma cell lines, while NBS1 protein content was not altered in response to genotoxic agents. Additionally, IR-induced downregulation of c-Myc protein content had no correlation with decreased cell viability. These findings indicate that the functional relationship between c-Myc and NBS1 in the context of genotoxic stress may be genetic background-specific.