MUC5B and breast cancer: IF stainings for basal- (KRT5, KRT17), secretory- (MUC5AC, MUC5B, SCGB1A1), or ciliated (AcTub) epithelial cell markers revealed that the human BC maintain their basal cell identity and differentiated towards secretory MUC5AC+, MUC5B+, SCGB1A1 + epithelial cells (Fig. 6F).