Overexpression of Aromatase P450 in Leiomyoma Tissue Is Driven Primarily through Promoter I.4 of the Aromatase P450 Gene (CYP19)

Abstract

The CYP19 gene encoding aromatase P450 (estrogen synthetase) is expressed in several extragonadal sites and regulated in a tissue-specific fashion, which is achieved by alternative use of the seven different promoters (and corresponding exons 1) of the CYP19 gene. Previously, we demonstrated that aromatase P450 is overexpressed in leiomyoma tissue and that in situ estrogen synthesized in leiomyoma tissues possibly plays a role in leiomyoma growth. To elucidate the mechanism of overexpression of aromatase P450, we determined the promoter use of aromatase P450 in leiomyomas. 5'-Rapid amplification of cDNA ends analysis revealed that of six leiomyoma nodules tested, four nodules contained I.4-specific transcript of aromatase P450 alone, one nodule contained PII-specific transcript alone, and the remaining nodule contained both I.4- and PII-specific transcripts simultaneously. The levels of aromatase transcripts were then quantified by competitive RT-PCR assay. Among 21 leiomyomas, I.4-specific transcript and PII-specific transcript were predominant in 18 and 2 leiomyomas, respectively, whereas the remaining leiomyoma was negative for aromatase P450 expression. We next compared the aromatase activity of leiomyoma cells stimulated by promoter-specific regulatory factors. A combination of IL-1beta and dexamethasone, known as a potent inducer of promoter I.4-driven transcription, effectively increased aromatase activity. A combination of (Bt)(2)cAMP, 3-isobutyl-1-myethylxanthine, and PGE(2), known as inducers of promoter II-driven transcription, also increased aromatase activity, but the increases found were smaller than that induced by dexamethasone and IL-1beta. The transcriptional ability of the promoter I.4 sequence was confirmed by transient transfection assay using primary cells released from leiomyomas and established cells from normal myometrium (KW cells). Luciferase vectors containing promoter I.4 sequence (-340/+14 or longer) showed a significant increase in luciferase activity in response to dexamethasone. Deletion or mutation of a putative glucocorticoid-responsive element in the promoter I.4 sequence eliminated promoter activity. These results indicate that promoter I.4 is the major promoter responsible for overexpression of aromatase P450 in leiomyomas and that a glucocorticoid-responsive element within it plays a substantial role in the expression of aromatase P450.

Functional analysis of the I.3, I.6, pII and I.4 promoters of CYP19 (aromatase) gene in human osteoblasts and their role in vitamin D and dexamethasone stimulation

“…This activation of I.4 promoter activity has similarly been described in the stromal cells of adipose tissue as well as in hOBs (22,24,25,31). A glucocorticoid-response element in the I.4 promoter could well be involved in this osteoblast response (24).…”

Celebrating 75 years of oestradiol

“…Aromatase excess syndrome results from subchromosomal recombination events including duplication, deletion, and inversion (Shozu & Simpson 1998, Shozu et al 2002. The latter two recombinations result in recruitment of novel promoters for CYP19A1.…”

Processes of apoptosis and cell proliferation in uterine myomas originating from reproductive and perimenopausal women

“…Apoptosis and cell proliferation in uterine myomas Apoptosis and cell proliferation in uterine myomas Apoptosis and cell proliferation in uterine myomas Apoptosis and cell proliferation in uterine myomas Apoptosis and cell proliferation in uterine myomas www.fhc.viamedica.pl of steroids and other growth factors in the initiation and growth of the tumors remain incompletely understood [8]. Most probably, the neoplastic transformation of smooth muscle cells to leiomyoma involves somatic mutations of genes playing roles in proliferation and apoptosis in a normal myometrium and in complex interactions between sex steroids and growth factors.…”