RelB regulates Bcl-xl expression and the irradiation-induced apoptosis of murine prostate cancer cells

Apoptosis in prostate cancer (PCa) induced by ionizing radiation (IR) is believed to play a critical role in radioresistance. Bcl-xl, an important member of the anti-apoptotic Bcl-2 family, has critical roles in tumor progression and development. The aim of the present study was to investigate the association of Bcl-xl expression and radiosensitivity from murine PCa RM-1 cells. An adenovirus-mediated RNA interference technique was employed to inhibit the expression of the RelB gene. RelB proteins were detected upon irradiation following transfection with small interfering (si)RelB, as shown by western blot analysis. The radiosensitivity of the RM-1 cells was determined by clonogenic assays. The apoptosis of the RM-1 cells were detected by flow cytometry assay, then quantitative polymerase chain reaction assays were performed to determine the expression level of Bcl-xl mRNA in the RM-1 cells. Radiation treatment increased the RelB protein levels from the cytosol and nucleus in the RM-1 cells. The protein expression levels of RelB in the pLentilox-sh-RelB-transfected RM-1 cells were significantly lower than in the negative interference group following radiation treatment. The percentage of cells undergoing apoptosis in the siRelB-RM-1 group was significantly higher than that in the control group following radiation treatment. Finally, a positive link between Bcl-xl expression and RelB activity was established in the RM-1 cells. Inhibition of RelB correlates with a decrease in expression of Bcl-xl. In conclusion, adenovirus-mediated siRNA targeting RelB inhibits Bcl-xl expression, enhances radiosensitivity and regulates the irradiation-induced apoptosis of the murine PCa RM-1 cell line.