BRCA1 and breast cancer: Fzd7 was also highly expressed in 2 out of 4 Trp53-null ER-positive mammary tumors but exhibited medium/low expression levels in Brca1 knockout (KO)/Trp53-wild type (WT) tumors (S4 Fig), raising a possibility of a potential role of p53-loss in Fzd7 up-regulation.