c-fos gene and protein expression in pelvic endometriosis: a local marker of estrogen action.

Endometriosis is an estrogen-dependent disease, causing pelvic pain and infertility. c-fos is an early transcription factor that has been reported to be related to estradiol-dependent cell proliferation. The aim of the present study was to assess the c-fos gene and protein expression in pelvic endometriotic implants in comparison to normal endometrium from infertile women. An open, prospective and controlled study included 15 infertile women with endometriosis and 19 control infertile women. Endometrial and endometriotic biopsies were performed at the follicular phase and the samples were processed for RT-PCR and immunohistochemistry. ERalpha mRNA levels were similar in the endometriotic implants/eutopic endometrium from women with endometriosis and in normal tissue (P = 0.649). The aromatase gene, however, was not expressed in the eutopic endometrium from either control or endometriosis groups, and was only expressed in 50% of endometriotic implants (P = 0.044). c-fos gene expression was higher in endometriotic implants (1.32 +/- 0.13; P = 0.011) than in eutopic endometrium from patients with endometriosis (0.97 +/- 0.11) or from the control group (0.91 +/- 0.05). In addition, immunohistochemistry showed a more abundant distribution of c-Fos in the stroma of endometriotic tissue compared to eutopic endometrium. These data suggest that c-fos may play a role in the molecular mechanisms of estrogen action on the induction, promotion or progression of endometriosis.