Immunohistochemical Demonstration of Membrane-bound Prostaglandin E-2 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 nonneoplastic 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.