Defining the mechanisms by which leptin stimulates proliferation of ovarian cancer cells
15017 Background: Ovarian cancer (OvCa) ranks fourth as the cause of death related to cancer in women in the U.S. The vast majority (>90%) of OvCa originates from the ovarian surface epithelium. There is sufficient evidence to suggest that hormones, especially estrogen, may be involved in the etiopathogenesis of epithelial OvCa. Recent studies indicate that leptin participates either directly or indirectly to promote carcinogenesis in both breast and endometrial cancers. Furthermore it has been proposed that leptin may elicit its action via an estrogen related pathway. Leptin can stimulate proliferation of some OvCa cell lines and has been implicated as a potential biomarker for OvCa. However the mechanism(s) by which leptin contributes to the growth of OvCa has yet to be defined. We hypothesize that leptin’s effect will be mediated in part by estrogen receptor (ER) pathways. Methods: Three epithelial OvCa cell lines (IGROV1, OVCAR5 and TOV21G) and one benign human ovarian surface epithelial cell line (HOSE) were evaluated. Enzyme linked immunosorbent assay (ELISA) and Western blotting were used to assess leptin and leptin receptor (ObR), respectively. Leptin (0.06 nM–6.25 nM) induced effects on cell proliferation were assessed in the presence or absence of an aromatase enzyme inhibitor (Anastrozole) or the ER antagonist (ICI182780). Further, we explored leptin-induced effects on ERα promoter activity as evidenced by change in fluorescence via a dual luciferase promoter reporter. All experiments were conducted in triplicate. All data were subjected to ANOVA followed by Tukey’s post hoc test (p < 0.05). Results: All ovarian cell lines expressed ObR; whereas, no measurable amounts of leptin were detected in conditioned media. Leptin stimulated cell proliferation in both the benign and malignant lines. Leptin-induced cell proliferation was inhibited by Anastrozole and ICI182780. Furthermore, leptin stimulated luciferase activity of the ERα promoter/reporter. Conclusions: Leptin promotes proliferation of benign and malignant ovarian epithelial cells and appears to be mediated, at least in part, via aromatase and ER which may have therapeutic implications. This work was supported by the Vincent Memorial Hospital, SG Komen Foundation and the Advanced Medical Research Foundation. No significant financial relationships to disclose.