TP53 and neoplasm: Compared to the normal mammary tissues, MMTV-PyMT tumor tissues contains similar levels of FZD7+ cells (both <5%), whereas both C3(1)-Tag and p53/BRCA1-deficient basal-like tumors, particularly the latter, contained elevated levels of FZD7+ cells (both >5%) (Fig 1F and S5C Fig).