Increased expression of tissue inhibitor of metalloproteinase‐2 in clear cell carcinoma of the ovary

The matrix metalloproteinases (MMPs) and the tissue inhibitors of metalloproteinases (TIMPs) have been associated with ovarian tissue remodelling and development of ovarian tumours. With respect to ovarian cancer, the majority of previous studies were performed on serous and mucinous tumours, and little is known about clear cell carcinoma, which shows unique characteristics among ovarian cancers. In the present study, we assessed the differences in the levels of MMP-2, MMP-9, TIMP-1 and TIMP-2 in the normal ovary and ovarian tumours of different histology, including clear cell carcinoma, using specific enzyme-linked immunosorbent assays. In malignant tumours, a prominent increase in pro-MMP-9 levels was observed compared with those of normal ovary and benign tumours, and pro-MMP-2 and TIMP-1 levels were moderately increased. In contrast, TIMP-2 levels were markedly decreased in malignant tumours compared with normal ovary with the exception of clear cell carcinoma, in which they were significantly elevated. Similar results were obtained by the organ culture of carcinoma tissue and normal ovary as well as in the cyst fluids of the tumours. Increased expression of TIMP-2 in clear cell carcinoma was also confirmed by Western blot analysis. Immunohistochemistry showed that TIMP-2 immunoreactivity was localized predominantly in epithelial cancer cells in clear cell carcinoma, while it was present mainly in stromal cells in the other histological types. Taken together, the present study shows that TIMP-2 expression is markedly increased in clear cell carcinoma of the ovary, suggesting a role of TIMP-2 in its unique characteristics among ovarian cancers.