RAD51 and cancer: Previous studies found some potentially functional SNPs of HR genetic polymorphisms (e.g., RAD51-135 G>C, −172G>T, XRCC2 4234G>C, R188H, XRCC3 T241M and NBN E185Q) to be associated with various types of cancer risks, including cancers of the lung, breast, ovary, leukemia and head and neck [21].