Effect of prostatic inhibin peptide (PIP) on prostate cancer cell growth in vitro and in vivo.

Prostatic inhibin peptide (PIP), is a 94 amino acid protein which is secreted by the prostate gland in an androgen-independent manner. Previously, it has been demonstrated that PIP appears to inhibit follicle-stimulating-hormone (FSH) secretion by the pituitary and prostate glands. In vitro, the Dunning R3327 rat prostate cancer cell line MAT-LyLu (MLL) cells and the human prostate cancer cell line PC-3, are stimulated to grow in response to exogenous FSH and these effects are blocked by PIP. In vivo, PIP inhibits the growth of the highly metastatic MLL prostate cancer cell line. A comparison of hormone levels in control and PIP-treated rats demonstrates a significant inhibition of FSH in treated animals. It appears that, in vivo, PIP may inhibit prostate cancer growth by inhibiting FSH. PIP may represent a novel hormonal treatment for prostate cancer.