Abstract
It is well known that DNA-PKcs contributes to nonhomologous end-joining of DNA double-strand breaks, forming a complex with Ku70 and Ku80. We examined whether radio/heat sensitivity is enhanced by DNA-PKcs-targeted small interference (si)RNA which degrades DNA-PKcs mRNA. We used p53-null human cultured cells (H1299) transfected with wtp53 (H1299/wtp53) or mp53 gene (H1299/mp53) or SAS cells transfected with mp53 gene to study whether the effect of DNA-PKcs-targeted siRNA on radio/heat sensitivity of cells is p53-dependent or not. Colony formation assay showed X-ray sensitivity of those cells was remarkably enhanced by DNA-PKcs-targeted siRNA p53-independently but the heat sensitivity was not affected by the siRNA in the H1299 cells. In contrast, the heat sensitivity of SAS cells was slightly enhanced by the siRNA. In addition, heat-induced hsp70 accumulation was increased by the siRNA in the H1299 cells. Therefore, the increased hsp70 accumulation by the siRNA may introduce the no effectiveness about the heat sensitivity of the H1299 cells. These results suggest that DNA-PKcs-targeted siRNA is a strong candidate for p53-independent radiation sensitizer. [J Radiat Res 44:407 (2003)]
