In the human melanoma cell line, A375, vorinostat sensitized cells to radiation-induced apoptosis by inhibiting key DNA repair genes, Ku70, Ku80 and Rad 50 [37].Using cDNA expression arrays, phenylbutyrate attenuated the expression of DNA-PK and worked synergistically with ionizing radiation to induce apoptosis in prostate cancer cell lines [34]. Here, XRCC5 is linked to prostate cancer.