THU625 Med12 Mutation Activates Tryptophan-Kynurenine-ahr Pathway To Promote Growth Of Uterine Leiomyoma

Disclosure: A. Zuberi: None. Y. Huang: None. A. Dotts: None. H. Wei: None. J. Coon V: None. T. Lizuka: None. O. Wu: None. O. Sotos: None. D. Chakravarti: None. Y. Dai: None. S.E. Bulun: None. P. Yin: None. A.Z. and Y.H. contributed equally to this work.(†) Y.D., S.E.B., and P.Y. are co-senior authors. (‡)To whom correspondence should be addressed: Serdar E. Bulun, M.D.Division of Reproductive Science in MedicineDepartment of Obstetrics and Gynecology Feinberg School of Medicine at Northwestern University 250 E. Superior Street, Suite 03-2306 Chicago, Illinois 60611-2914 Tel: 312-472-3636 Fax: 312-472-3740 Email: s-bulun@northwestern.edu Ping Yin, M.D., Ph.D. Division of Reproductive Science in Medicine Department of Obstetrics and Gynecology Feinberg School of Medicine at Northwestern University 303 E. Superior Street, Suite 10-111 Chicago, Illinois 60611 Tel: 312-503-1831 Fax: 312-503-0095 Email: p-yin@northwestern.edu. Conflict of interest: The authors have declared that no conflict of interest exists. Uterine leiomyomas (LM) cause heavy menstrual bleeding, anemia and pregnancy loss in approximately 10 million US women. Driver mutations in the mediator complex subunit 12 (MED12) gene in uterine myometrial cells initiate 70% LM tumors that grow in a progesterone-dependent manner. We showed a distinct chromatin occupancy landscape of MED12 and a shift of binding sites from proximal promoters to intronic/intergenic regions in mutant (mut-MED12) vs wild-type LM tissues. Integration of cistrome and transcriptome data identified tryptophan 2,3-dioxygenase (TDO2) as the top mut-MED12 target gene, which was massively upregulated in mut-MED12 LM. TDO2 catalyzes the conversion of tryptophan to kynurenine, which is an aryl hydrocarbon receptor (AHR) ligand and significantly elevated in mut-MED12 LM. Incubation of primary mut-MED12 LM cells with tryptophan or kynurenine stimulated AHR nuclear translocation, increased proliferation, inhibited apoptosis and induced AHR-target gene expression, whereas blocking the TDO2-kynurenine-AHR pathway by siRNA or pharmacologically abolished these effects. Progesterone receptor regulated the expression of AHR and its target genes. In vivo, TDO2 expression positively correlated with the expression of genes crucial for LM growth. In summary, activation of the TDO2-kynurenine-AHR pathway selectively in mut-MED12 LM induces tumor growth and may inform the development of targeted treatments and precision medicine. Presentation: Thursday, June 15, 2023