Messenger ribonucleic acid levels of steroid 5 alpha-reductase 2 in human prostate predict the enzyme activity.

Testosterone is converted to dihydrotestosterone by 5 alpha-reductase2 in the prostate. Dihydrotestosterone controls cell division, and interindividual differences in prostatic 5 alpha-reductase 2 expression and activity may be a determinant of the risk of developing prostate cancer. However, little is known about interindividual differences in intraprostatic hormonal activity in vivo. To determine whether 5 alpha-reductase-specific messenger RNA (mRNA) is predictive of 5 alpha-reductase activity in prostatic tissue, we analyzed 30 prostatic tissue specimens from 15 Caucasian patients, 47--82 yr old. The mRNA was measured by RT-PCR. Five specimens consisted of cancer, whereas the remaining 25 were derived from benign prostate hyperplasia (BPH). We found a strong association between enzyme activity at pH 5.5 and the 5 alpha-reductase 2-specific mRNA expression when expressed on the basis of beta-actin [Spearman's rank-correlation coefficient (r(s)) = 0.81; 95% confidence interval, 0.64-0.91; P < 0.0001]. The expression of 5 alpha-reductase 2-specific mRNA in the cancer specimens was significantly lower than in the BPH tissue (P = 0.03). There was no difference in the expression of 5 alpha-reductase 1-specific mRNA in the cancer specimens, compared with BPH (P = 0.56). The strong association between 5 alpha-reductase activity at pH 5.5 and the 5 alpha-reductase 2-specific mRNA expression makes it possible to predict prostatic 5 alpha-reductase activity using core needle biopsies.