XRCC2 and breast cancer: RAD51 homolog (RecA homolog, E. coli) (S. cerevisiae) plays an important role in homologous recombination via, direct interaction with XRCC2 (X-ray repair cross-complementing group 2), XRCC3 (X-ray repair cross-complementing group 3), BRCA1 (breast cancer-1), BRCA2 (breast cancer-2), and other DNA repair proteins, to form a complex essential for repair of double-strand breaks and DNA cross-links (especially XRCC2 and XRCC3) and for the maintenance of chromosome stability [18–20].