Given the effect of combined deletion of Wwox and Brca1 on mammary tumor formation and the known effect of WWOX/BRCA1 interaction on DNA repair pathway choice in vitro [17, 38, 39], we next set to examine which DSB repair pathway is favored in tumors of K14-Cre;Brca1fl/fl;Wwoxfl/fl mice. The gene discussed is BRCA1; the disease is breast cancer.