However, a recent proteomic study was able to identify the classical form of the KLK4 protease in seminal plasma and blood serum from individuals with confirmed prostate cancer and negative biopsy without being able to identify any significant difference between the two sample groups, but thus confirming KLK4 is secreted from PCa as well as the normal prostate [41]. Here, KLK4 is linked to prostate carcinoma.