Roles of Kallikrein-2 Biomarkers (Free-Hk2 and Pro-Hk2) for Predicting Prostate Cancer Progression-Free Survival

Free human kallikrein 2 (free-hK2) and hK2 pro-form (pro-hK2) have been found to be increased in tumor tissues and serum from patients with prostate cancer. We established semiautomatic assays for free-hK2 and pro-hK2 using a research version of the Beckman Coulter ACCESS2 system. Serum samples from a cohort of 189 men undergoing radical prostatectomy for known high-risk disease were assayed for Prostate-Specific Antigen (PSA), free-PSA, free-hK2, and pro-hK2. Univariate Cox regression and multivariate models were used to predict both Gleason scores and progression-free survival (PFS). Free-hk2 levels ≥80 ng/L were predictive of both Gleason scores ≥7 ( p = 0.04) and PFS ( p = 0.03). PSA ≥8.0 µg/L also was predictive of PFS ( p = 0.02). However, neither % free-PSA nor pro-hK2, when treated as continuous or cutoff variables were associated with Gleason score or PFS. Multivariable models showed that clinical stage T1c versus T2/T3, Gleason score ≥7, and PSA ≥8.0 µg/L or clinical stage T1c versus T2/T3, Gleason scores ≥7, and free-hK2 ≥80 ng/L were among the best models predicting PFS. Both free-hK2 and PSA in conjunction with clinical stage and Gleason score are good predictors of PFS in prostate cancer.