KLK4 and ovarian cancer: Previous studies reported that KLK4 (hK4) proteins are present in normal prostate tissue and are secreted in seminal plasma; however, higher levels of KLK4 expression are associated with the progression of ovarian cancer, mainly late stage serous epithelial-derived ovarian carcinomas where hK4 represents a potential biomarker for diagnosis and prognosis [64, 65].