Molecular tools to reestablish progestin control of endometrial cancer cell proliferation

OBJECTIVE: Endometrial cancers often arise in a setting of estrogen stimula tion unopposed by the differentiating effects of progesterone. Our laborato ry and others have previously shown that progesterone receptor down-regulat ion or perturbation of progesterone receptor isoform A or B expression is a ssociated with the development of poorly differentiated endometrial cancers that are not growth inhibited by progestins. The purpose of these studies was to reestablish high progesterone receptor isoform A and 8 gene expressi ons in such endometrial cancer cells and to examine the effects of progesti n treatment on cell growth and metastatic potential after this transformati on. STUDY DESIGN: To induce high levels of expression of the progesterone recep tor isoforms in KLE and Hec50 endometrial cancer cells, adenoviral vectors encoding the genes for progesterone receptor isoforms A and B were created. The characteristic ability of cancer cells to grow independently of anchor age to the surrounding solid matrix was measured by counting colony formati on on soft agar for 8 to 14 days. Cell proliferation in response to a time course of progestin treatment was tested with flow cytometry. RESULTS: After treatment with a control vector without a progesterone recep tor-encoding insert, no effect of progestin treatment on cell proliferation was found, after treatment with vectors encoding progesterone receptor iso form A or B, however, progestin treatment resulted in significant inhibitio n of cell growth. The anchorage-independent cell growth on soft agar assay showed that by 8 to 14 days the number of cell colonies was reduced by 50% relative to control preparations in the presence of progesterone receptor i soform A plus progestin (P <.0001, both Hec50 and KLE cell lines) and by 90 % in the presence of progesterone receptor isoform B plus progestin(P<.0001 , both Hec50 and KLE cell lines). Progestin treatment also resulted in a ti me-dependent reduction in cell proliferation as measured by flow cytometry. Although transfection with both progesterone receptor isoforms A and B red uced cell proliferation according to our assays, progesterone receptor isof orm B caused a much more dramatic decrease in cell growth (P = .001, Hec50 cells; P <.0001, KLE cells), CONCLUSION: In poorly differentiated endometrial cancer cells that are resi stant to progestin therapy, adenovirus-induced expressions of progesterone receptors A and B reestablish progestin control of endometrial cancer cell proliferation.