Alternative gonadotropin-releasing hormone processing products secreted from endometrial carcinoma

Gonadotropin-releasing hormone (GnRH) receptor is demonstrated in uterine endometrial carcinoma. The endometrial carcinoma also produces GnRH or -like peptide, which prompted us to examine whether the intratumoral serves as natural ligand for its receptor. Endometrial carcinomas surgically removed had been screened for GnRH receptor expression before analysis. The in endometrial carcinoma cell-enriched culture media was characterized by immunoblots in tricine-supplied electrophoresis system and subsequent amino acid sequencing. Three major proteins of 10.0 kDa, 7.6 kDa and 1.1 kDa corresponding to pre-proGnRH, proGnRH and decapeptide GnRH, respectively, were detected in all of the ten endometrial carcinoma specimens tested. Immunoreactive contents in the culture media, assessed by RIA, ranged from 0.08 to 0.1 nM. In chorionic cell-conditioned media, only 1.1-kDa protein was detected. Endometrial carcinoma cells secrete alternative GnRH processing products in addition to natural GnRH. The GnRH variants may compete with mature GnRH at the level of its receptors, perhaps counteracting the GnRH signaling pathway to retard cell proliferation.