XRCC6 and glioblastoma: Ku70 predicts results of RT in prostate cancer, EAF2 as a critical factor mediating androgen protection of DNA damage via Ku70/Ku80 in prostate cancer, Ku70 silences chemo‐sensitizes gemcitabine in pancreatic cancer cells, target therapy for radiosensitization of Glioblastoma multiforme (GBM) with hyper‐activated UBE2S, ku70/80 as prognostic tool to envisage the reaction to chemoradiation in locally progressive rectal cancer (LARC)