KLK2 and Familial prostate cancer: In our study, KLK2, KLK3, and KLK4 were identified as gene signatures for prostate cancer; KLK3 is a prostate-specific antigen that is a gold-standard clinical biomarker widely employed in the diagnosis and monitoring of prostate cancer (Fuhrman-Luck et al., 2014); KLK2 showed promise as prostate cancer biomarker, as well.