XRCC6P5 and cancer: However, as with the case of overexpression of endogenous antioxidants, even those DNA repair proteins that show largely beneficial effects in terms of mutagenesis protection may reduce the clinical efficacy of radiation therapy for cancer in the event of subsequent carcinogenesis due to enhanced DNA repair capabilities in cancer cells when constitutively expressed [245], while simultaneously enhancing protection from carcinogenesis prior to actual malignant transformation.