TP53 and breast cancer: At the molecular level, basal-like breast cancer exhibits expression patterns which are also observed in the basal epithelial layer of the skin and airways; this includes expression of high molecular weight cytokeratins 5, 6, and 17 and deficiencies in retinoblastoma transcriptional corepressor 1 (RB1), BRCA1, and tumor protein 53 (TP53).