KLK15, also known as kallikrein-15 isoform 4, is one of the fifteen kallikrein subfamily members located in a cluster on chromosome 19. This protein contains multiple polyadenylation sites and alternative splicing results in multiple transcript variants encoding distinct isoforms. Also, growing evidence suggests that many kallikreins are implicated in carcinogenesis and some have potential as novel cancer and other disease biomarkers. In prostate cancer, it has increased expression, which indicates its possible use as a diagnostic or prognostic marker for prostate cancer.