FRI372 Retinoic Acids Attenuate The Endometriotic Cell Proliferation Through A Cell-specific Receptor Isoform

Disclosure: M. Izawa: None. Y. Azuma: None. F. Taniguchi: None. [Background] Endometriosis has been accepted as an estrogen-dependent, proliferative and inflammatory disease for over two decades, and the hormonal therapy targeting the reduction of estrogen has been employed as the first choice of treatment to reduce the endometriosis-associated symptoms. However, the limitation of therapy is becoming evident. In the hope of overcoming the limitation, we focused on retinoids, which have been known to elicit antiproliferative activity in breast tumors. Retinoic acid receptor (RAR) expression has been known to correlate with estrogen receptor expression. [Objective] As a first step to test the antiproliferative activity of retinoids in endometriotic lesions, we examined the expression profile of the retinoic acid receptor (RAR) in endometriotic cells. We then examined the antiproliferative activity of retinoids and the effect of estrogen on their activity. [Patients] Institutional Review Boards approved this project. We obtained informed consent from all patients. The chocolate cyst lining in the ovaries of patients with endometriosis was the source of endometriotic tissue. [Methods] Endometriotic cells: Stromal cells were collected from endometriotic tissues and used as endometriotic cells throughout the experiment. RAR gene expression: Single-stranded cDNA was prepared and subjected to PCR. Primer sets were designed using sequences in the UCSF genome browser. At the end of PCR cycles, the reaction mixture was subjected to electrophoresis on agarose gel. As an internal control, β-tubulin mRNA expression was assayed in parallel. Cell proliferation: Endometriotic cells were treated with retinoids in the presence or absence of estradiol (E2). All-trans retinoic acid (ATRA) and selective RAR modulators (SRARMs) were used. The number of viable cells was estimated using WST-8 assay. Ki-67 expression: Ki-67 expression was examined by Western blotting. As an internal control, β-tubulin expression was assayed in parallel. [Results] RAR mRNA expression: Transcripts of wild-type RARα, RARβ, RARγ, and their splice variants were demonstrated. These mRNAs were expressed almost at a comparable level: a truncated form of RARα without a DNA binding domain, a truncated form of RARβ without a transactivation domain at the N-terminal, and a form of RARγ with a distinct transactivation domain at N-terminal region. Effect of Retinoic acids on cell proliferation: The cell proliferation rate and Ki-67 expression were downregulated in the presence of ATRA. Among SRARMs tested, a selective RARγ modulator decreased cell proliferation. The antiproliferative activity of ATRA was attenuated in the presence of E2 in some cells.[Conclusion]We tested the antiproliferative activity of retinoids in endometriotic cells. Although the endometriotic cells responded to retinoids, the present finding suggested the diversity of cell types in endometriotic lesions. Presentation: Friday, June 16, 2023