EP₂ and EP₄ Receptors Regulate Aromatase Expression in Human Adipocytes and Breast Cancer Cells: EVIDENCE OF A BRCA1 AND p300 EXCHANGE

• Published in: The Journal of biological chemistry 2008-02, Vol.283 (6), p.3433-3444
• Main Authors: Subbaramaiah, Kotha, Hudis, Clifford, Chang, Sung-Hee, Hla, Timothy, Dannenberg, Andrew J
• Format: Article
• Language: English
• Subjects: Adipocytes - enzymology; Adipocytes - metabolism; Animals; Aromatase - biosynthesis; Aromatase - genetics; BRCA1 Protein - genetics; Breast Neoplasms - enzymology; Cell Line, Tumor; Dinoprostone - metabolism; E1A-Associated p300 Protein - genetics; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Neoplastic; Humans; Mammary Neoplasms, Animal - metabolism; Mice; Mice, Transgenic; Receptors, Prostaglandin E - metabolism; Receptors, Prostaglandin E, EP2 Subtype; Receptors, Prostaglandin E, EP4 Subtype
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M705409200

Cytochrome P450 aromatase (aromatase), a product of the CYP19 gene, catalyzes the synthesis of estrogens from androgens. Because aromatase-dependent estrogen biosynthesis has been linked to hormone-dependent breast carcinogenesis, it is important to elucidate the mechanisms that regulate CYP19 gene expression. The main objective of this study was to identify the receptors (EP) for prostaglandin E₂ (PGE₂) that mediate the induction of CYP19 transcription in human adipocytes and breast cancer cells. Treatment with PGE₂ induced aromatase, an effect that was mimicked by either EP₂ or EP₄ agonists. Antagonists of EP₂ or EP₄ or small interference RNA-mediated down-regulation of these receptors suppressed PGE₂-mediated induction of aromatase. PGE₂ via EP₂ and EP₄ stimulated the cAMP[rightward arrow]protein kinase A pathway resulting in enhanced interaction between P-CREB, p300, and the aromatase promoter I.3/II. Overexpressing a mutant form of p300 that lacks histone acetyltransferase activity suppressed PGE₂-mediated induction of aromatase promoter activity. PGE₂ via EP₂ and EP₄ also caused a reduction in both the amounts of BRCA1 and the interaction between BRCA1 and the aromatase promoter I.3/II. Activation of the aromatase promoter by PGE₂ was suppressed by overexpressing wild-type BRCA1. Silencing of EP₂ or EP₄ also blocked PGE₂-mediated induction of the progesterone receptor, a prototypic estrogen-response gene. In a mouse model, overexpressing COX-2 in the mammary gland, a known inducer of PGE₂ synthesis, led to increased aromatase mRNA and activity and reduced amounts of BRCA1; these effects were reversed by knocking out EP₂. Taken together, these results suggest that PGE₂ via EP₂ and EP₄ activates the cAMP[rightward arrow]PKA[rightward arrow]CREB pathway leading to enhanced CYP19 transcription and increased aromatase activity. Reciprocal changes in the interaction between BRCA1, p300, and the aromatase promoter I.3/II contributed to the inductive effects of PGE₂.