Regulation of aromatase expression in human ovarian surface epithelial cells.
Ovarian cancer originates mainly from surface epithelial cells, which are potential targets of estrogen action. Using immunohistochemistry and RT-PCR analysis, aromatase (estrogen synthetase) can be detected in human ovarian surface epithelial tumors. In this study, we functionally characterized the aromatase expressed in a primary cell culture, normal human ovarian surface epithelial (HOSE) 17. The apparent K(m) and V(max) values were determined to be 5.8 +/- 0.5 nM, and 0.3 +/- 0.0 pmol/mg.h, respectively. The aromatase activity in HOSE 17 cells can be induced effectively by phorbol esters and forskolin, suggesting that estrogen biosynthesis in HOSE 17 cells is mainly regulated through protein kinase C- and protein kinase A-mediated mechanisms. Exon I-specific RT-PCR revealed that phorbol esters predominantly up-regulated promoter II. Whereas forskolin treatment increased exon I.3A-containing messenger RNA, the aromatase activity remained low in the cells treated with this agent. In vitro transcription/translation analysis using plasmids containing T7 promoter and the human snail gene (SnaH) as a reporter capped with different untranslated exon Is revealed that exon PII-containing transcripts were translated more effectively than exon I. 3-containing transcripts. These findings explain why aromatase activity is higher in cells with the PII-containing transcripts than is cells with the I.3-containing transcripts. Our results indicate that aromatase is functionally expressed in human ovarian surface epithelial cells and its expression is regulated at both the transcriptional and translational levels.
Okubo
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Division of Immunology, Beckman Research Institute of the City of Hope, Duarte, California 91010, USA.
Mok
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SC
Chen
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D020121:5' Untranslated Regions / Q000235:genetics; D000328:Adult; D000735:Androstenedione / Q000378:metabolism; D001141:Aromatase / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D015139:Blotting, Southern; D002273:Carcinogens / Q000494:pharmacology; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D004247:DNA / Q000032:analysis; D003907:Dexamethasone / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D005938:Glucocorticoids / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D010053:Ovary / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000302:isolation & purification; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014158:Transcription, Genetic / Q000235:genetics
D020121:5' Untranslated Regions; D002273:Carcinogens; D005938:Glucocorticoids; D012333:RNA, Messenger; D005576:Colforsin; D000735:Androstenedione; D003907:Dexamethasone; D004247:DNA; D001141:Aromatase; D013755:Tetradecanoylphorbol Acetate