Gonadotropin releasing hormone analogs induce apoptosis by extrinsic pathway involving p53 phosphorylation in primary cell cultures of human prostatic adenocarcinomas.
BACKGROUND
Gonadotropin-releasing-hormone (GnRH) analogs are widely used to block hypothalamic-pituitary-gonadal axis and inhibit blood androgen levels in patients with prostate cancer (PCa). In addition, GnRH analogs induce proliferation arrest and apoptosis through GnRH receptors expressed on the membrane of PCa cells. Possible molecular mechanisms involved in GnRH-mediated apoptosis on prostate cancer cells were studied.


METHODS
Primary cultures from PCa and benign prostatic hyperplasia (BPH) (non-malignant control) were derived from samples provided by our Institutional Hospital. Cell cultures were incubated for 24 hr with 20 ng/ml of GnRH agonist Leuprolide (Lp) or antagonist Cetrorelix (Cx). Apoptosis was evaluated by studying the expression of Bax and Bcl-2 and the activation of caspase-9 (intrinsic pathway), caspase-8 (extrinsic pathway), and caspase-3. Also, mRNA level, protein expression and phosphorylation of p53 were studied.


RESULTS
Cleaved caspase-8 and -3, but not -9, increased in presence of Lp and Cx in PCa cell cultures. Bax and Bcl-2 mRNA levels showed no changes after GnRH-analog treatments. Only Bax protein showed an increase after Cx treatment in PCa cell cultures. p53 mRNA level was higher in PCa than in BPH cell cultures. Lp and Cx increased p53 expression and phosphorylation in PCa cell cultures.


CONCLUSIONS
Apoptosis induced by GnRH analogs seems to be mediated by extrinsic pathway involving p53 phosphorylation. Phosphorylated-p53 might be associated with the increase in apoptotic NGF receptor, p75, previously reported by our laboratory. These findings reinforce the concept of clinical use of GnRH analogs for PCa suggesting that intraprostatic treatment may be more effective.
Clementi
Marisa
M
Faculty of Medicine, Physiology and Biophysics Program, Institute of Biomedical Sciences, University of Chile, Santiago, Chile.
Sánchez
Catherine
C
Benitez
Dixan A
DA
Contreras
Héctor R
HR
Huidobro
Christian
C
Cabezas
Juan
J
Acevedo
Cristian
C
Castellón
Enrique A
EA
D000230:Adenocarcinoma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000494:pharmacology* / Q000627:therapeutic use; D006801:Humans; D008297:Male; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D015398:Signal Transduction / Q000502:physiology*; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism* / Q000502:physiology
D016159:Tumor Suppressor Protein p53; D007987:Gonadotropin-Releasing Hormone