KLK3 and benign prostatic hyperplasia: Serum PSA levels are not correlated with AKR1C3 (rs = -0.016, P = 0.979) in BPH but are negatively correlated with AKR1C3 expression (rs = -0.377, P = 0.036), which indicates that AKR1C3 is a better marker to reflect the clinicopathological stage and evaluation of PCa progression in those patients with low levels of PSA.