6816 The Estrogen Environment Characteristic of Endometriotic Lesion May Attenuate the Receptor γ-Mediated Antiproliferative Activity of Retinoids

Abstract Disclosure: M. Izawa: None. Y. Azuma: None. F. Taniguchi: None. Background: Endometriosis has been accepted as an estrogen-dependent disease, and the estrogen environment in endometriotic lesions has been proposed as a major background of the pathophysiology. Although the hormonal therapy targeting the reduction of estrogen has been employed to reduce endometriosis-associated symptoms, the limitation of therapy has been well recognized. How to overcome the limitation remains an urgent subject to be explored. [Objective:]We focused on retinoids, which have been known to induce an antiproliferative activity in tumors. Based on the retinoic acid receptor (RAR) expression profile in endometriotic lesions, we evaluated the antiproliferative activity of retinoids using endometriotic cells. Finally, we examined the effect of estrogen on antiproliferative activity. Methods: Endometriotic tissue and cells: Institutional Review Boards approved this project. The chocolate cyst lining in the ovaries of patients with endometriosis was the source of endometriotic tissue. Stromal cells collected from endometriotic tissues were used as endometriotic cells. RAR expression: RNAs were prepared from endometriotic tissues and cells, and single-stranded cDNAs were subjected to RT-PCR. Primers were designed using the UCSF genome browser. Protein expression was examined by Western blotting. Cell proliferation assay: Cells were treated with all-trans retinoic acid (ATRA), selective RAR modulators (sRARMs), BMS753, CD2314 and CD437, RARγ antagonist MM11253 and 17β-estradiol (E2). Viable cells were estimated using WST-8 assay. RNA-seq analysis: Cells were treated with retinoids and E2. RNA samples were used for polyA+ selected library and the strand-specific RNA-seq. Differentially expressed genes with p-values < 0.05 and log2 fold changes > 1 were extracted as responsive genes. Results: RAR expression: Transcripts of wild-type RARα, RARβ, and RARγ were demonstrated in arbitrary 10 regions of patient tissue, and in endometriotic cells. The expression of these RARs was almost at a comparable level. Effect of retinoids and/or estrogen on cell proliferation: Cell proliferation rate was significantly decreased in the presence of ATRA. Among sRARMs tested, only CD437 reduced the cell proliferation. The antiproliferative activity of ATRA was attenuated either in the presence of MM11253 or E2, respectively. ATRA- and/or E2-responsive gene expressions To explore gene expressions in response to retinoids and E2, RNA-seq analysis was performed. The results suggest the diversity of ATRA- and E2-responsive genes in endometriotic lesions.[Conclusion:]Endometriotic cell proliferation was significantly suppressed in response to retinoids through RARγ. The observation that the antiproliferative activity was attenuated in the presence of E2 suggests a suppressive environment against the activity of retinois in endometriotic legions. Presentation: 6/2/2024