Roles of luteinizing hormone/chorionic gonadotropin receptor in anchorage-dependent and -independent growth in human ovarian surface epithelial cell lines

Abstract

Epithelial ovarian carcinomas are thought to arise from cells of ovarian surface epithelium (OSE) covering the free surface of the human ovary. Two immortalized human cell lines, OSE2a (non-tumorigenic) and OSE2b-2 (tumorigenic), were previously established from normal OSE cells of a reproductive-age patient. In the present study, we found that expression of luteinizing hormone (LH)/chorionic gonadotropin (CG) receptor (LH/CGR) is present in OSE2a cells and absent in OSE2b-2 cells. In OSE2a cells, a low concentration (103 mlU/ml) of CG enhanced anchorage-dependent growth via up-regulation of insulin-like growth factor-1 (IGF1), whereas a high concentration (105 mlU/ml) of CG induced anchorage-independent growth and down-regulation of IGF1 expression. To investigate involvement of other genes in LH/CGR-related tumorigenicity, we compared cDNA expression arrays of OSE2a and OSE2b-2 cells, and found that the following genes had lower expression in OSE2b-2 than in OSE2a: integrin β1, intercellular adhesion molecule-1 (ICAM1), and Waf1/Cip1. Subsequent semiquantitative reverse transcription polymerase chain reaction using OSE2a cells showed that expression of integrin β1 was down-regulated by a high concentration (105 mlU/ml) of CG. These results suggest that LH/CGR affects anchorage-dependent and -independent growth by mediating up- and down-regulation of IGF1 and integrin β1. Repetitive and excessive activation of LH/ CGR may cause genetic alteration of its signal transduction pathway, resulting in stimulation of growth of OSE cells, initiation of ovarian carcinogenesis, and cancer progression.