Using cell surface biotinylation of intact SKBR3 breast cancer cells and Caco2 CRC cells, we demonstrated that the streptavidin (SA)-binding, biotinylated proteins from both cell lines included KRT19 and KRT8 (SI Appendix, Fig. S2A), a type II keratin protein that dimerizes with KRT19. Here, KRT19 is linked to breast cancer.