Gonadotropin-Releasing Hormone Signaling Pathways in an Experimental Ovarian Tumor

• Published in: Endocrinology (Philadelphia) 2003-07, Vol.144 (7), p.2957-2966
• Main Authors: Chamson-Reig, Astrid, Sorianello, Eleonora M, Catalano, Paolo N, Fernández, Marina O, Pignataro, Omar P, Libertun, Carlos, Lux-Lantos, Victoria A. R
• Format: Article
• Language: English
• Subjects: Adenylate cyclase; Adenylyl Cyclases - metabolism; Animals; Antineoplastic Agents, Hormonal - pharmacology; Arachidonic acid; Biological and medical sciences; Buserelin - pharmacology; Carcinogens - pharmacology; Cell activation; Cell culture; Chorionic gonadotropin; Culture media; Cyclic AMP; Cyclic AMP - metabolism; Enzyme Activation - drug effects; Extracellular signal-regulated kinase; Female; Fundamental and applied biological sciences. Psychology; Gonadotropin-releasing hormone; Gonadotropin-Releasing Hormone - metabolism; Gonadotropins; GTP-Binding Protein alpha Subunits; GTP-Binding Protein alpha Subunits, Gi-Go - metabolism; Heterotrimeric GTP-Binding Proteins - metabolism; Kinases; Luteoma - metabolism; Mitogen-Activated Protein Kinase 1 - metabolism; Mitogen-Activated Protein Kinase 3; Mitogen-Activated Protein Kinases - metabolism; Ovarian Neoplasms - metabolism; Ovaries; Pertussis; Pertussis toxin; Pertussis Toxin - pharmacology; Phospholipase; Phospholipase A2; Phospholipase C; Phospholipase D; Phospholipase D - metabolism; Phospholipases A - metabolism; Phosphorylation; Phosphorylation - drug effects; Pituitary (anterior); Progesterone; Progesterone - secretion; Protein kinase C; Protein Kinase C - metabolism; Proteins; Rats; Rats, Sprague-Dawley; Second messengers; Signal transduction; Signal Transduction - physiology; Tetradecanoylphorbol Acetate - pharmacology; Toxins; Tumor cells; Tumor Cells, Cultured; Tumors
• ISSN: 0013-7227; 1945-7170
• DOI: 10.1210/en.2003-0011

Previous results showed that GnRH signaling is altered in cells from rat luteinized ovarian tumors (tumor group) because it did not activate the phospholipase C pathway, in contrast to control ovarian cells from superovulated prepubertal rats (SPO). In the present work, alternate GnRH-induced second messengers such as phospholipase A2 and phospholipase D activation, cAMP production, ERK1/2 phosphorylation, and the presence of G proteins were evaluated to determine GnRH mechanism of action in tumor cells. G proteins examined were present in both cell types. Buserelin, a GnRH agonist, (1, 10, and 100 ng/ml) increased phosphatidylethanol in SPO, indicating phospholipase D activation. Only 100 ng/ml buserelin induced a significant response in the tumor group. Buserelin (100 ng/ml) increased 3H-arachidonic acid in culture media in SPO, indicating phospholipase A2 activation; no effect was observed in the tumor group. Buserelin (100 and 1000 ng/ml) induced pertussis toxin-insensitive cAMP increases in both cell types, with similar potencies. In the tumor group, buserelin (100 ng/ml) inhibited human chorionic gonadotropin-induced cAMP and progesterone; this effect was protein kinase C (PKC) dependent (inhibited by GF109203X, a PKC inhibitor). Buserelin (100 and 1000 ng/ml) induced ERK1/2 phosphorylation in both cell kinds. Buserelin-induced ERK1/2 activation was Gi/0 independent and PKC dependent. Only in the tumor group, buserelin-induced ERK1/2 activation was cAMP dependent (abolished by SQ 22536, the adenylyl cyclase inhibitor). Furthermore, dibutyryl cAMP-induced ERK1/2 activation in the tumor group was PKC dependent (inhibited by GF109203X). In conclusion, activation of phospholipases in tumor cells does not seem to mediate GnRH effects. GnRH signaling seems to involve adenylyl cyclase activation, PKC stimulation, and ERK1/2 phosphorylation.