Identification of Tumorigenesis from the Specific Coupling of Cyclooxygenase-2 with Microsomal Prostaglandin E2 Synthase-1 in vivo

Abstract

A newly created hybrid enzyme (COX-2-10aa-mPGES-1), which mimics the specific biosynthesis of the inflammatory PGE2 through COX-2's coupling to mPGES-1, was stably expressed in HEK293 cells. The stable cell line, which consistently expresses the superior triple catalytic (Trip-Cat) activities from COX-2 and mPGES-1, was able to directly convert arachidonic acid into the pathogenic PGE2 and distinguish it from other PGE2 synthesizing pathways, as confirmed by enzyme immunoassay, LC/MS analysis and a specific [14C]-AA (arachidonic acid) metabolite analysis approach. A competitive assay confirmed that the endogenous cPGES and mPGES-2 in the HEK293 cells had little involvement in the presence of the expressed COX-2-10aa-mPGES-1 for the synthesis of pathogenic PGE2. Furthermore, subcutaneous injection of the stable cell lines into nu/nu mice revealed 100% (10 out 10) occurrence of tumor mass formation beginning on Day 7 and a continuous progression of the masses to the maximal size which required sacrificing the mice. In contrast, only 10% occurrence of tumor masses, though smaller and with slower growth rates, were observed for the group of vector-transfected HEK293 control cells expressing only endogenous cPGES and/or mPGES-2. The PGE2 produced from multiple pathways by the HEK293 cells co-expressing the individual wild type COX-2 and mPGES-1, and in the presence of endogenous cPGES and mPGES-2, showed also a significantly increased tumor occurrence rate to 30%, which confirmed that the sole coupling of COX-2 to mPGES-1 is a powerful tumor-advancing factor. This result implies that the engineered COX-2-10aa-mPGES-1 could be a promising molecule as a drug developing target against the pathway of COX-2 coupled to mPGES-1 to treat inflammatory diseases and cancers.