KRT5 and breast cancer: We conducted in silico experiments to estimate the number of cleavages that typically occur in cytokeratin (CK5, 7, 8, 14, 17, 18 and 19) [33–35] and collagen (collagen type I α1 chain, α2 chain and type III α1 chain) [36] subtypes expressed in normal mammary gland and breast cancer tissue by representative digestive enzymes (Additional file 1: Fig. S2B and S2C).