The soluble EP2 receptor FuEP2/Ex2 suppresses endometrial cancer cell growth in an orthotopic xenograft model in nude mice

Endometrial cancer is one of the most common gynecologic malignancies and many factors influence in its growth and development. As in many other types of cancer, prostaglandin E2 (PGE2) is thought to be an accelerator of cell proliferation and endometrial cancer progression. In this study, we examined the effect of FuEP2/Ex2, a soluble decoy receptor for PGE2 on growth of endometrial cancer cells. A stable transfectant expressing FuEP2/Ex2 was established from human endometrial cancer Ishikawa cells (Ish-FuEP2/Ex2). Ish-FuEP2/Ex2 cells expressed FuEP2/Ex2 mRNA and protein. Expression levels of E-prostanoid receptor 1 (EP1), EP2, EP3, EP4, and F-prostanoid receptor (FP) were almost the same in Ish-FuEP2/Ex2 and vector control cells. Growth rates of Ish-FuEP2/Ex2 under normal culture conditions were also similar to vector control cells, although PGE2-induced growth stimulation was completely inhibited in Ish-FuEP2/Ex2 or by Ish-FuEP2/Ex2 culture medium. Moreover, phosphorylation of extracellular signal-regulated kinase (ERK) and induction of cyclooxygenase-2 (COX-2), vascular endothelial growth factor (VEGF), cyclin D1, and c-fos mRNA by PGE2 were not observed in Ish-FuEP2/Ex2 and Ish-FuEP2/Ex2 culture medium-treated vector control cells, although they were found when treated with prostaglandin F2α. An orthotopic xenograft model in athymic nude mice revealed that Ish-FuEP2/Ex2-injected mice had significantly decreased mean tumor area. The proportion of Ki-67-positive cells in the tumor lesion was also significantly lower in Ish-FuEP2/Ex2-injected mice. These findings suggest that an EP-targeting strategy using FuEP2/Ex2 may be of use in the treatment of endometrial cancer.