DECREASED EXPRESSION OF FUNCTIONAL HUMAN CHORIONIC-GONADOTROPIN LUTEINIZING-HORMONE RECEPTOR GENE IN HUMAN UTERINE LEIOMYOMAS

Human myometrium contains functional hCG/LH receptors. The purpose of this study was to determine whether or not leiomyomas that arise from myometrium also contain these receptors. Northern blotting demonstrate d that leiomyomas and normal adjacent myometria contained hCG/LH recep tor mRNA transcripts. Western immunoblotting showed that leiomyomas an d corresponding normal myometria also contained 60- and 50-kDa recepto r proteins. Ligand blotting revealed that only the 50-kDa receptor pro tein in leiomyomas and corresponding normal myometria could bind I-125 -hCG and that this binding was inhibited by excess unlabeled hCG. In s itu hybridization and immunocytochemistry revealed that smooth muscle cells in leiomyomas and corresponding normal myometria contained the h CG/LH receptor mRNA transcripts and receptor proteins. The receptor le vels were lower in leiomyomas than in corresponding normal myometria. However, the receptors were functional, as treatment with hCG resulted in a decrease of connexin-43 protein levels in leiomyomas as in norma l myometria. In summary, human uterine leiomyomas express a functional hCG/LH receptor gene at a reduced level compared with that for normal corresponding myometria, This finding could be relevant to an underst anding of the growth control mechanisms in leiomyomas and the manner i n which medical therapy for leiomyomas might work.