Abstract:
Endometrial carcinoma is the most common malignancy of the female reproductive tract and the incidence in developed countries is rising. Poor survival of late stage and recurrent endometrial carcinoma patients, particularly with an aggressive histologic subtype, necessitate the development of new therapeutic modalities for advanced stage and recurrent endometrial carcinoma. Recent published data have demonstrated elevated levels of human growth hormone (hGH) in endometriosis and endometrial adenocarcinoma. Herein, I demonstrate that autocrine production of hGH can enhance the in vitro and in vivo oncogenic potential of endometrial carcinoma cells. Forced expression of hGH in endometrial carcinoma cell lines RL95-2 and AN3 resulted in an increased total cell number through enhanced cell cycle progression and decreased apoptotic cell death. In addition, autocrine hGH expression in endometrial carcinoma cells promoted anchorage-independent growth and increased cell migration/invasion in vitro. In a xenograft model of human endometrial carcinoma, autocrine hGH enhanced tumor size and progression. Changes in endometrial carcinoma cell gene expression stimulated by autocrine hGH was consistent with the altered in vitro and in vivo behavior. Functional antagonism of hGH in wild-type RL95-2 cells significantly reduced cell proliferation, cell survival, and anchorage- independent cell growth. These studies demonstrate a functional role for autocrine hGH in the development and progression of endometrial carcinoma and indicate potential therapeutic relevance of hGH antagonism in the treatment of endometrial carcinoma. I further provided evidence for the functional role of the neurotrophic factor artemin (ARTN) in progression of endometrial carcinoma. Increased ARTN protein expression was observed in endometrial carcinoma and ARTN protein expression in endometrial carcinoma was significantly associated with higher tumor grade and invasiveness. Forced expression of ARTN in endometrial carcinoma cells significantly increased total cell number as a result of enhanced cell cycle progression and cell survival. In addition, forced expression of ARTN significantly enhanced anchorage-independent growth and invasiveness of endometrial carcinoma cells. Moreover, forced expression of ARTN increased tumor size in xenograft models and produced highly proliferative, poorly differentiated and invasive tumors. The ARTN stimulated increases in oncogenicity and invasion were mediated by increased expression and activity of AKT1. siRNA mediated depletion or antibody inhibition of ARTN significantly reduced oncogenicity and invasion of endometrial carcinoma cells. Thus, inhibition of ARTN may be considered as a potential therapeutic strategy to retard progression of endometrial carcinoma. Furthermore, I demonstrated that ARTN stimulates the oncogenicity and invasiveness of endometrial carcinoma cells. Herein, I demonstrate that ARTN modulates the sensitivity of endometrial carcinoma cells to agents used to treat latestage endometrial carcinoma. Forced expression of ARTN in endometrial carcinoma cells decreased sensitivity to doxorubicin and paclitaxel. Accordingly, depletion of ARTN by small interfering RNA or functional inhibition of ARTN with antibodies significantly increased sensitivity of endometrial carcinoma cells to doxorubicin and paclitaxel. Forced expression of ARTN in endometrial carcinoma cells abrogated doxorubicininduced G2-M arrest and paclitaxel-induced apoptosis. ARTN increased CD24 expression in endometrial carcinoma cells by transcriptional up-regulation, and CD24 was partially correlated to ARTN expression in endometrial carcinoma. Forced expression of CD24 in endometrial carcinoma cells stimulated cell proliferation and oncogenicity, enhanced cell invasion, and decreased sensitivity to doxorubicin and paclitaxel. Depletion of CD24 in endometrial carcinoma cells abrogated ARTNstimulated resistance to doxorubicin and paclitaxel. ARTN-stimulated resistance to doxorubicin and paclitaxel in endometrial carcinoma cells is therefore mediated by the specific regulation of CD24. Functional inhibition of ARTN may therefore be considered as an adjuvant therapeutic approach to improve the response of endometrial carcinoma to specific chemotherapeutic agents.