Our purpose was to examine the immunolocalization of inhibin, activin and the activin signaling system in ovarian clear cell adenocarcinoma tissue. Tissue samples of ovarian clear cell adenocarcinoma were collected from ten women. The patients' ages ranged from 41 to 71 years (mean ± standard deviation; 53.4±9.9). Their surgicopathological staging was based on the criteria of the International Federation of Gynecology and Obstetrics (FIGO); there were 5 patients with stage I, 3 with stage II, and 2 with stage III. We examined the immunohistochemical localization of inhibin/activin α-subunit, βA-subunit, activin A, and activin receptor types IA, IB, IIA, IIB, Smad2, Smad3 and Smad4 using an avidin-biotin peroxidase complex technique. With the antibodies against the βA-subunit, and activin A, we observed positive immunoreactive staining in the cytoplasm of clear cell adenocarcinoma, whereas we did not observe any staining for the α-subunit of inhibin. We observed positive immunoreactive staining in the cell cytoplasm and surface with the antibodies against the activin receptors, types IA, IB, IIA and IIB. We observed positive immunoreactive staining in the cytoplasm and nucleus with the antibodies against the Smad2, Smad3 and Smad4. It is suggested that activin A, not inhibins, might be secreted by ovarian clear cell adenocarcinoma, and that an activin signal transduction pathway might exist in ovarian clear cell adenocarcinoma.

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