The mechanism for protein kinase C inhibition of androgen production and 17alpha-hydroxylase expression in a theca cell tumor model.
BACKGROUND
In polycystic ovary syndrome (PCOS), there is increased formation of androgens by thecal cells. Moreover, PCOS ovaries have been shown to have decreased levels of c-fos transcription factor. We hypothesize that c-fos expression inhibits 17alpha-hydroxylase 17,20 lyase (CYP17) activity in the human ovary, and its decreased expression seen in PCOS may lead to elevated CYP17 transcription, resulting in increased androgen production.


OBJECTIVE
Our objective was to define the role of the activator protein-1 transcription factors, namely c-fos, in the regulation of CYP17 expression in theca cells.


METHODS
Human ovarian thecal-like tumor cells were used for all experiments. The following techniques were used: steroid quantification, mRNA extraction, microarray analysis, transfection, small interfering RNA, and immunohistochemistry.


RESULTS
Stimulation of human ovarian thecal-like tumor cells with the protein kinase A pathway activator forskolin resulted in stimulation of C19 androgen production. In contrast, treatment with the protein kinase C pathway activator tetradecanoylphorbol acetate (TPA) resulted in decreased androgen production with a shift toward C21 progesterone production. TPA also led to complete inhibition of CYP17. Microarray data showed a 37-fold increase in c-fos after treatment with TPA. Transfection with steroidogenic factor 1 resulted in an increase in CYP17 promoter activity, which was significantly inhibited in the presence of c-fos. c-fos gene silencing led to an increase in CYP17 mRNA levels. Immunohistochemical staining for c-fos in ovaries demonstrated strong staining in granulosa cells, but not theca.


CONCLUSIONS
The activator protein-1 transcription factor c-fos plays a role in the inhibition of CYP17 expression. The decreased levels of c-fos expression in polycystic ovaries may be responsible for increased CYP17 levels in PCOS.
Beshay
Victor E
VE
Department of Obstetrics and Gynecology, Division of Reproductive Endocrinology and Infertility, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, Texas 75235-9032, USA.
Havelock
Jon C
JC
Sirianni
Rosa
R
Ye
Ping
P
Suzuki
Takashi
T
Rainey
William E
WE
Carr
Bruce R
BR
D000728:Androgens / Q000096:biosynthesis*; D015153:Blotting, Western; D045744:Cell Line, Tumor; D018076:DNA, Complementary / Q000096:biosynthesis / Q000235:genetics; D005260:Female; D020868:Gene Silencing; D016762:Genes, fos / Q000235:genetics; D016758:Genes, jun / Q000235:genetics; D005822:Genetic Vectors; D006801:Humans; D007150:Immunohistochemistry; D020411:Oligonucleotide Array Sequence Analysis; D010051:Ovarian Neoplasms / Q000201:enzymology / Q000378:metabolism*; D011085:Polycystic Ovary Syndrome / Q000378:metabolism; D011493:Protein Kinase C / Q000502:physiology*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D034741:RNA, Small Interfering; D013254:Steroid 17-alpha-Hydroxylase / Q000096:biosynthesis*; D013798:Thecoma / Q000201:enzymology / Q000378:metabolism*; D014162:Transfection
D000728:Androgens; D018076:DNA, Complementary; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D013254:Steroid 17-alpha-Hydroxylase; D011493:Protein Kinase C