For example, one of the liver tumors arising from P2p53 mice showed complete Palb2 deletion and likely stemmed from PALB2 loss; a lung tumor and a liver tumor from B1p53 mice showed strong Brca1 deletion to a degree similar to that found in mammary tumors from mice in the same cohort (Supplementary Fig. 2), suggesting that these two tumors might have arisen due to BRCA1 loss. Here, BRCA1 is linked to breast cancer.