RB1 and breast cancer: Tumors expressing part of the large T antigen (T121), and thus inhibiting proteins of the Rb family, displayed the luminal subtype of breast cancer, and cells were positive for expression of hormone receptors and Her2, regardless of their Brca1 status, while tumors with loss of Trp53 and Brca1 but without Rbf suppression exhibited the triple-negative phenotype.