KLK6 and neoplasm: Based on GEPIA database, the mRNA expressions of key genes KLK6, KRT6A and KRT6C in CRC samples and normal samples were verified, implying that KLK6 expression in tumor tissues was substantially elevated as compared to normal tissues (p < 0.05, Fig. 3D); KRT6A level in tumor tissues was increased as compared to normal tissues without significant difference (p > 0.05, Fig. 3E).