Down-regulation of macrophage inhibitory cytokine-1/prostate derived factor in benign prostatic hyperplasia

Macrophage inhibitory cytokine-1 (MIC-1) is a member of transforming growth factor-beta/bone morphogenetic protein (BMP) superfamily. Despite its potential role in prostatic regulation, little is known about its biological activity.

Expression profiling using 42K Affymetrix HuGeneFL array was conducted to compare symptomatic benign prostatatic hyperplasia (BPH), histological BPH without symptoms, and normal prostate samples from donors. MIC-1 gene expression was analyzed by RT-PCR in pure culture of prostate epithelial and stromal cells, and prostate cancer cells, LNCaP, PC-3, DU-145. Influence of androgens on MIC-1 expression in LNCaP cells was analyzed by Northern blot. Enhancement of promoter activity of MIC-1 by androgens was examined using reporter assays.

In contrast to normal prostates, MIC-1 gene was down-regulated in BPH samples with symptoms and histological BPH obtained from cystoprostatectomy specimens (P < 0.005 and P < 0.01, respectively). Expression level of MIC-1 in androgen-sensitive LNCaP cells was high and enhanced by androgens, whereas in the androgen-insensitive PC-3 and DU-145 cells the expression level was low. An 11 kb promoter region of MIC-1 gene was identified to be 6- to 12-fold activated by androgens.

Down-regulation of MIC-1 may play a role in the development of BPH. MIC-1 is positively regulated by androgens, but other regulatory factors remain unclear.