Mice with Brca1 and Trp53 loss develop basal-like HR-negative mammary tumors, and mice with inhibition of proteins of the Rb family and Trp53 loss or the combination of Rb, Trp53 and Brca1 aberrations develop luminal ductal carcinoma that is positive for ER, PR and Her2 expression, but endocrine resistant. Here, ESR1 is linked to breast cancer.