Enhancement of radiation induced cell death in chicken B lymphocytes by withaferin A

Abstract

Withaferin A (WA), a plant withanolide, has shown significant radiosensitizing effect <i style="">in vitro</i> and <i style="">in vivo</i>. Inhibition of DNA repair has been suggested as a mechanism of radiosensitization by WA. To test this, the effect of withaferin A on survival of DT40 chicken B-lymphocyte cell line and its repair deficient single gene mutants Rad54^-/-, Ku70^-/- and double mutant Ku70^-/-/Rad54^-/-after irradiation was studied. Exponentially growing cells were treated for 1 hr with 5 mM WA and then exposed to different doses of X-rays. Cell survival was studied by clonogenic assay. WA significantly reduced survival of DT40, Ku70^-/- and Ku70^-/-/Rad54^-/-, but not Rad54^-/-cells, suggesting that WA enhances radiosensitivity by interfering with homologous repair, the major pathway of DSB repair in these cells. Inhibition of DNA repair is further indicated in a significant decrease in surviving fraction of DT40 cells by post-irradiation incubation with WA. This could have relevance to cancer radiotherapy.