Antiproliferative effects of luteinizing hormone-releasing hormone agonists on the human prostatic cancer cell line LNCaP.

Abstract

Highly potent LH-releasing hormone (LHRH) agonists have been recently introduced in therapy for the treatment of the carcinoma of the prostate, an androgen-dependent pathology. These peptides are believed to act mainly by inhibiting the pituitary-testicular axis and, consequently, by reducing testosterone levels. The recent observation that binding sites for LHRH analogs are present on prostatic tumor tissue suggests that these drugs could also act directly on the tumor. To verify this hypothesis, the effects of two potent LHRH agonists [Zoladex (Z) and Buserelin (B)] have been studied on the proliferation of the human prostatic cancer cell line LNCaP (lymph node carcinoma of the prostate). LNCaP cells were treated for 9 days with different doses of either Z or B (concentrations from 10(-12)-10(-6) M). Both analogs significantly inhibited cell proliferation at doses between 10(-9)-10(-6) M. The antiproliferative action of the two LHRH agonists was shown to be dose dependent, with IC50 values of 0.82 and 1.79 nM for Z and B, respectively. A similar treatment with B was without any significant effect on the proliferation of a mouse embryo fibroblast cell line (Swiss 3T3), which was used as a nontumoral control. The inhibitory action of both LHRH agonists (10(-8) M) on LNCaP cell proliferation was completely antagonized by the simultaneous treatment of the cells with a potent LHRH antagonist (Nal-Arg-LHRH; 10(-8) M); when given alone at the dose selected, the antagonist did not affect cell growth. These results clearly suggest that the antiproliferative effect of LHRH agonists on LNCaP cells may be mediated by specific receptors. The presence of binding sites for [125I]B was consequently demonstrated on the membranes of LNCaP cells cultured in a medium containing charcoal-stripped fetal calf serum, i.e. in the absence of steroids. The affinity of these binding sites for the ligand was lower than that observed for the same receptors on rat pituitary membranes. To clarify the mechanism of the antiproliferative action of the LHRH agonists, the effects of both Z and B on the incorporation of [3H]thymidine and [14C]methionine into LNCaP cells were investigated. During a short incubation period (3 h), the two LHRH agonists rapidly inhibited [3H]thymidine incorporation into the cells. The same treatment did not affect the incorporation of [14C]methionine into proteins.(ABSTRACT TRUNCATED AT 400 WORDS)

Down-regulation of proliferation and up-regulation of apoptosis by gonadotropin-releasing hormone agonist in cultured uterine leiomyoma cells

“…These GnRH-binding sites are present in endometrium, endometrial carcinoma, ovary, and placenta as well as in breast, ovarian, endometrial, prostatic, and hepatoma cancer cell lines (10 -18). In vitro studies with breast, prostatic and ovarian cancer cell lines suggest that GnRHa directly inhibits cell proliferation and induces apoptosis (7,19,20). RT-PCR analysis revealed that uterine leiomyoma, unaffected myometrium, and isolated myometrial smooth muscle cells maintained in primary culture express GnRH and GnRH receptor mRNA (21,22).…”

Alteration of gonadotropin-releasing hormone receptor expression with the progression of prostate cancer in the Dunning rat adenocarcinoma sublines

“…The clinical application of GnRH analogues in the treatment of hormone-dependent malignancies is primarily based on their ability to inhibit the hypophysealÁ/gonadal axis through the desensitization of gonadotropes and hence the suppression of circulating levels of sex steroids [21,22]. In addition, specific membrane receptors for GnRH, at least type I, have been found in a high percentage of human prostate tumours and various rat and human PC cell lines [1,2,4,10,16,17]. These receptors mediate inhibiting effects of GnRH analogues in vitro suggesting that direct inhibitory effects on the tumour may be of importance also in vivo.…”

“…Evidence is now accumulating that GnRH analogues may inhibit tumour growth, not only by suppressing the pituitary Á/testicular axis but also by acting directly at the level of the tumour [1,2]. Specific binding sites for GnRH (GnRH-R type I and II) have been characterized in a number of extrapituitary tissues including the prostate [3 Á/5].…”

“…Specific binding sites for GnRH (GnRH-R type I and II) have been characterized in a number of extrapituitary tissues including the prostate [3 Á/5]. GnRH-like immunoreactive material has been isolated from the human PCa cell lines LNCaP and DU 145 and from specimens of human malignant prostate tumours [1,2,6]. Furthermore, it has been shown that LNCaP cells produces and secretes an enzyme that degrades GnRH [7].…”

Induction of transforming growth factor beta in hormonally treated human prostate cancer

“…The majority of British urologists now use either orchiectomy or luteinising hormone-releasing hormone analogues (LHRH) in this context. Both stilboestrol (Schultz & Bauer, 1988) and LHRH analogues (Qayum et al, 1990;Limonta et al, 1992) are known to have directly cytotoxic effects on prostatic cancer cells in vitro, but the conventional view of their mode of action centres around suppression of androgen production via the hypothalamic-pituitary-gonadal axis.…”