KLK3 and prostate cancer: Although most patients with prostate cancer are diagnosed with low-risk disease, approximately 15% of the patients are identified with high-risk prostatic cancer and face poor prognosis, with a 5-year biochemical recurrence (defined as prostate-specific antigen (PSA) ≥0.2 ng/mL)-free rate of 41.6%-62.8% (2–6).