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Aromatase Expression in Uterine Leiomyomata Is Regulated Primarily by Proximal Promoters I.3/II

Division of Reproductive Biology Research (A.G.I., Z.L., P.Y., S.D., B.Y., S.E.B.), Department of Obstetrics and Gynecology, Northwestern University, Chicago, Illinois 60611; and Department of Obstetrics and Gynecology (M.C., A.C.), Cumhuriyet University School of Medicine, 58140 Sivas, Turkey

Address all correspondence and requests for reprints to: Serdar E. Bulun, M.D., Department of Obstetrics and Gynecology, Northwestern University, 303 East Superior Street, Suite 4-123, Chicago, Illinois 60611. E-mail: s-bulun{at}northwestern.edu.

Context: Uterine leiomyomata are common tumors that cause irregular uterine bleeding and pregnancy loss and depend on estrogen for growth. Aromatase catalyzes the conversion of androgens to estrogens. Aromatase expression is regulated via alternatively used promoters in the placenta (I.1 and I.2a), fat (I.4, I.3, and II), bone (I.6), and gonads (II). A prostaglandin E₂/cAMP-dependent pathway regulates coordinately the proximal promoters I.3/II, whereas glucocorticoids and cytokines regulate the distal promoter I.4. Use of each promoter gives rise to a population of aromatase mRNA species with unique 5'-untranslated regions (5'-UTRs). Uterine leiomyoma tissue, but not normal myometrium, overexpresses aromatase leading to estrogen-stimulated cell proliferation. Aromatase inhibitor treatment shrank uterine leiomyomata in a few women.

Objective and Design: Promoter I.4 was reported to regulate aromatase expression in uterine leiomyomata from a group of Japanese women. Here, we used two independent techniques to identify the promoters that regulate aromatase expression in uterine leiomyomata (n = 30) from 23 African-American, Hispanic, and white women.

Results: Rapid amplification of 5'-cDNA ends of aromatase mRNA species revealed the following distribution of promoter usage in leiomyomata: promoters I.3/II, 61.5%; I.2a, 15.4%; I.6, 15.4%; and I.4, 7.7%. Real-time PCR, which quantifies mRNA species with promoter-specific 5'-UTRs, revealed the following distribution for each 5'-UTR as a fraction of total aromatase mRNA: I.3/II, 69.6%; I.4, 7.3%; and other promoters, 23.1%.

Conclusions: The primary in vivo aromatase promoter in leiomyoma tissues in non-Asian U.S. women is the prostaglandin E₂/cAMP-responsive I.3/II region. Alternative signals may stimulate aromatase expression that is a common biological phenotype in uterine leiomyomata.

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