Kaposi's Sarcoma-Associated Herpesvirus Infection Promotes Invasion of Primary Human Umbilical Vein Endothelial Cells by Inducing Matrix Metalloproteinases

Abstract

Matrix metalloproteinases (MMPs) play important roles in cancer invasion, angiogenesis, and inflammatory infiltration. Kaposi's sarcoma is a highly disseminated angiogenic tumor of proliferative endothelial cells linked to infection by Kaposi's sarcoma-associated herpesvirus (KSHV). In this study, we showed that KSHV infection increased the invasiveness of primary human umbilical vein endothelial cells (HUVEC) in a Matrigelbased cell invasion assay. KSHV-induced cell invasion was abolished by an inhibitor of MMPs, BB-94, and occurred in both autocrine-and paracrine-dependent fashions. Analysis by zymography and Western blotting showed that KSHV-infected HUVEC cultures had increased secretion of MMP-1, -2, and -9. KSHV increased the secretion of MMP-2 within 1 h following infection without upregulating its mRNA expression level. In contrast, the secretion of MMP-1 and -9 was not increased until 6 h after KSHV infection and was correlated with the upregulation of their mRNA expression levels. Promoter analysis by reporter assays and electrophoretic mobility shift assays identified an AP-1 cis-element as the dominant KSHV-responsive site in the MMP-1 promoter. Together, these results suggest that KSHV infection modulates the production of multiple MMPs to increase cell invasiveness and thus contributes to the pathogenesis of KSHV-induced malignancies.

Kaposi's Sarcoma-Associated Herpesvirus Disrupts Adherens Junctions and Increases Endothelial Permeability by Inducing Degradation of VE-Cadherin

“…In the following experiments, we focused our efforts on the early stage of KSHV infection. stage of KSHV infection (27,57,81,84). While some proinflammatory and proangiogenic cytokines have been shown to regulate endothelial permeability in some pathological conditions (21,33,34,47,65), confluent endothelial cells are usually refractory to these cytokines partly because of the growth contact-inhibition effect exerted by the adherens junctions (13,37,46,64).…”

“…The disruption of adherens junctions mitigates contact inhibition and facilitates the growth of endothelial cells by transmitting mitogenic and survival signals, such as Src, phosphatidylinositol 3-kinase (PI 3-kinase), proteinase kinase C, protein kinase B, and mitogen-activated protein kinases (MAPKs), activated by extracellular growth and proangiogenic factors and by releasing ␤-catenin to the nucleus to promote the transcription of oncogenes, such as c-myc and cyclin D1 (15,71,74). We and others have shown that KSHV infection of endothelial cells activates many of these pathways and promotes the growth, angiogenesis, and invasion of the infected cells while simultaneously inducing proinflammatory and proangiogenic cytokines (14,27,54,57,66,67,76,81,82,84), which are consistent with the observed phenotypes of disruption of adherens junctions and increased endothelial permeability described in this study. Interestingly, these features are also characteristics of cellular transformation and the epithelial-to-mesenchymal transition of cancer cells (6,39).…”

The manipulation of miRNA-gene regulatory networks by KSHV induces endothelial cell motility

“…3,4 After infection, KSHV stimulates EC invasiveness by inducing extracellular matrix metalloproteinases (MMPs) such as MMP-1, MMP-2, and MMP-9. 10 Because the majority of cells in KS lesions and in KSHV-infected ECs are latently infected by KSHV, 4 viral latent proteins may, at least in part, contribute to the invasiveness of KSHV-infected cells. We have shown recently that K15M is a KSHV latent protein capable of inducing cell migration and invasion.…”

“…10,11 To identify the mechanisms involved, we analyzed KSHV-regulated genes in infected ECs. We used a recombinant KSHV expressing GFP 20 to infect a pure population of LECs.…”

Kaposi's Sarcoma-Associated Herpesvirus Downregulates Transforming Growth Factor β2 To Promote Enhanced Stability of Capillary-Like Tube Formation

“…In KS tumor cells, KSHV is predominantly in the latent state, and latent KSHV infection of endothelial cells can promote angiogenesis-related phenotypes, including increased tubule stability of macrovascular endothelial cells, induction of angiogenesis and capillary morphogenesis under low-growth-factor conditions, and enhanced migration and invasion (12)(13)(14)(15)(16)(17). During latent infection, KSHV expresses 6 genes, latency-associated nuclear antigen (LANA), vCyclin, vFLIP, and kaposins A, B, and C. Additionally, KSHV encodes a number of microRNAs (miRNAs) during latent infection.…”