Abstract B53: KSHV regulation of fibulins in Kaposi's sarcoma (KS): Implications for the role of the extracellular matrix in KS tumorigenesis

Introduction: Kaposi9s sarcoma-associated herpesvirus (KSHV) is the etiological agent of KS, which is the leading cause of cancer and cancer related mortality in HIV/AIDS. African Americans currently have the highest incidence of KS throughout the world. This study examines the initial pathogenic path leading to, or promoting KS, and considers if a protein(s) in that path could provide a novel prognostic and therapeutic target for KS. Experimental Procedures: Microarray analysis was used to examine KSHV and mock infected dermal microvascular endothelial cells (DMVEC). Expression of fibulin-2 protein was examined by dual labeled immunofluorescense and immunoblot analysis. Transcriptional analysis of fibulins was analyzed by quantitative real time polymerase chain reaction (qRT-PCR). KSHV infection levels in primary effusion lymphoma cell lines (PELs) were examined by Southern blot hybridization using a 32P labeled viral genome terminal repeat fragment as a probe. Fibulin-2 protein expression in PELs was determined by immunoblots. Fibulin-2 and KSHV latency associated nuclear antigen (LANA) expression in KS tumors was performed using KS tumor tissue microarrays (from the AIDS Cancer Specimen Resource Consortium) and dual labeled immunohisto-chemistry. Transcriptional analysis of fibulin-2 ligand binding partners and time course transcriptional analysis of infected and control DMVEC cells were performed by qRTPCR. Data Summary and Conclusions: Fibulins are extra-cellular matrix proteins (ECM) involved in cell adhesion, proliferation, migration, invasion and angiogenesis, and have been linked to progression of several cancers. To our knowledge, fibulins have not been studied in KS. Here we demonstrate that fibulin-2 protein expression is down-regulated 50-fold in 10 day KSHV infected DMVEC with a 26-fold reduction in fibulin-2 message. By time-course analysis there was a consistent reduction of fibulin-2 message accompanied by an increase in LANA transcription. After examining all fibulin family members, fibulins −2, −5 and −3 were down-regulated over time in KSHV infected DMVEC, fibulins 1C and 1D were up-regulated, and no change in fibulins 4, 6 and 7. In contrast, in PELs (which express different levels of KSHV lytic replication), we found no detectable fibulin-2 expression. Tissue microarrays representing patch/plaque and nodular forms of KS from 86 patients were shown to be statistically significant for downregulation of fibulin-2 in virus infected LANA positive cells by dual labeled immunohistochemical staining. We also examined transcriptional dysregulation of fibulin-2 ligand binding partners laminin a2, fibrillin, aggrecan, versican, fibronectin, nidogen, perlecan, and tropoelastin. We found a 5 and 12.5-fold transcriptional suppression of fibronectin and tropoelastin mRNA, respectively, in virus infected cells, with no significant change in transcription for other fibulin-2 ligand binding partners. This represents the first study to examine fibulin-2 expression in KSHV infected DMVEC and in KS tissue samples to determine if suppression of this ECM protein or its ECM ligand binding partners play a role in KS tumor progression. Understanding the interactions between KSHV, fibulin-2 and its associated ECM protein binding partners may lead to development of novel treatment strategies for KS disease. Citation Information: Cancer Epidemiol Biomarkers Prev 2010;19(10 Suppl):B53.