KLK6 and colorectal cancer: It is known that human hK6 is are involved in several malignancies, Several scholars have reported that hK6 is overexpressed in ovarian cancer [14], uterine serous papillary cancer [15], colorectal cancer [16], gastric cancer [6] and esophageal cancer [17], but underexpressed in salivary gland tumors [18] and renal cell carcinoma [19], which depends on the tumor tissue types and microenvironment [20].