Kaposi's sarcoma-associated herpesvirus confers a survival advantage to endothelial cells

Kaposi's sarcoma-associated herpesvirus (KSHV) is associated with three different human malignancies, including Kaposi's sarcoma (KS), primary effusion lymphoma, and multicentric Castleman's disease. The KS lesion is of endothelial cell in origin and is highly dependent on autocrine and paracrine factors for survival and growth. In this study, we show that KSHV infection of endothelial cells induces the activation of the prosurvival phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin pathway. KSHV infection of endothelial cells augmented cell survival in the presence of apoptotic inducers, including etoposide and staurosporine, and under conditions of serum deprivation. We found that KSHV infection of endothelial cells also increased the ability of these cells to form an in vitro tubular network under conditions of stress and growth factor deprivation. Finally, we show that the nuclear factor-kappaB and PI3K pathways are also required for endothelial tubular network formation. Collectively, these results suggest that KSHV infection of endothelial cells modulates cell signaling pathways and induces cell survival and angiogenesis, thereby contributing to the pathogenesis induced by KSHV.