Transcriptional Regulation and Control of mRNA Stability Constitute a Dual Effect Upon Cyclooxygenase-2 Gene Expression Regulation Triggered by KSHV-vGPCR.

JULIAN NAIPAUER; GEORGINA CARDAMA; AGATA M. DAGOSTINO; CLARA FONTANA; OMAR A. COSO; VICTORIA MEDINA; DAIANA A. SAPOCHNIK; ENRIQUE MESRI

New York

Workshop; The 22nd International Workshop on Kaposi?s Sarcoma Herpesvirus (KSHV) and Related Agents; 2019

NIH Usa

Kaposi sarcoma (KS) is the most frequent AIDS-related cancer and arises when endothelial cells are transformed by the KSHV virus. The constitutively active receptor vGPCR is encoded within the KSHV genome and has a key role in cell transformation and angiogenesis. For this reason, the identification of signalling events triggered by vGPCR could be of therapeutic interest. As Cyclooxygenase-2 (COX-2) is known to be an important inflammatory mediator, our goal is to characterize the link between vGPCR and COX-2 expression, through its promoter activation an mRNA stability. Using SVEC vGPCR (endothelial cells that constitutively express vGPCR), we observed COX-2 mRNA and protein overexpression, compared to SVEC control cells. Co-transfecting reporter plasmids and plasmids expressing several MEK kinases, we observed that vGPCR signalling has an impact both on COX-2 promoter activity and regulatory events involving mRNA 3?UTR elements. Constitutively active MEK (MEKEE) increases COX-2 promoter expression and, among mRNA binding proteins of the AUBP family, we observed that TTP decreases COX-2 mRNA stability. The Rac1 inhibitory drug 1A-116, provided evidence that Rac1 has an important role in COX-2 promoter activation.Treatment with the COX-2 selective inhibitory drug Celecoxib produces a significant retardation in tumor growth in a mouse model using injected cells that express vGPCR. An intradermal angiogenesis assay showed that treatment with the COX-2 inhibitory drug NS398 before inoculation of vGPCR-transformed cells abolishes the angiogenic response induced by vGPCR expression.Based on all these results we conclude that vGPCR upregulates COX-2 levels in endothelial cells due to a dual effect upon its promoter region and upon elements in the 3?UTR region of mature mRNAs. Also, we can conclude that vGPCR regulates angiogenicity and tumorigenicity via COX-2 activation. These facts pinpoint COX-2 as potential target for KS chemoprevention and therapy.