Immunohistochemical demonstration of membrane-bound prostaglandin E2 synthase-1 in papillary thyroid carcinoma

Microsomal prostaglandin E(2) synthase-1 (mPGES-1) is an inducible enzyme that catalyzes the conversion of prostaglandin (PG) H(2) to PGE(2) in downstream of cyclooxygenase-2 (COX-2). Recent studies have obtained in vitro evidence that PGE(2) participates in carcinogenesis, angiogenesis, and induction of matrix metalloproteinase-9 (MMP-9), which plays a crucial role in cancer invasion. However, implications for mPGES-1 in thyroid carcinomas remain to be determined. To address this issue, we performed an immunohistochemical analysis for mPGES-1, COX-2 and MMP-9 in 20 papillary thyroid carcinoma (PTC) patients. mPGES-1 immunoreactivity was localized in the cytoplasm of carcinoma cells in 19 cases, with an intensity that tended to be distinct at the interface between the tumor and the surrounding non-neoplastic tissue. Staining was more intense in regions with papillary arrangement, while it was less intense in regions with trabecular or solid arrangement. In many cases, immunohistochemical localization of COX-2 and MMP-9 resemble that of mPGES-1. Taken together, our results suggest the involvement of mPGES-1 in proliferation and differentiation of PTC as well as local invasion of PTC.