BRCA1 and neoplasm: Since Brca1 inactivation and subsequent tumor formation in the WAPcre-driven model occurs during the first estrus cycle (independent of pregnancy-induced WAP activation) [43], we anticipate that this is probably due to the fact that prior to treatment, WAPcre;Brca1F/F;Trp53F/F female mice contain Brca1-deficient mammary epithelial cells.