Objectives NR4A1 is overexpressed in many solid tumors, and the objectives of this study were to investigate the expression and functional role of this receptor in endometrial cancer cells and demonstrate that NR4A1 antagonist inhibit mTOR. Methods Ishikawa and Hec-1B endometrial cells were used as models to investigate the parallel effects of NR4A1 knockdown by RNA interference (siNR4A1) and treatment with bis-indole-derived NR4A1 ligands (antagonists) on cell growth and survival by determining cell numbers and effects on Annexin V staining. Western blot analysis of whole cell lysates was used to determine effects of these treatments on expression of growth promoting, survival and apoptotic genes and mTOR signaling. Effects of NR4A1 antagonists on tumor growth were determined in athymic nude mice bearing Hec-1B cells as xenografts. Results siNR4A1 or treatment with bis-indole-derived NR4A1 antagonists inhibited growth of endometrial cancer cells in vitro and endometrial tumors in vivo and this was accompanied by decreased expression of growth promoting and survival genes and mTOR inhibition. Conclusions NR4A1 exhibited pro-oncogenic activity in endometrial cells due, in part, to regulation of cell growth, survival and mTOR signaling, and all of these pathways and their associated gene products were inhibited after treatment with bis-indole-derived NR4A1 antagonists. Moreover, these compounds also blocked endometrial tumor growth in vivo demonstrating that NR4A1 is a potential novel drug target for treatment of endometrial cancer.
