Kaposi's Sarcoma (KS) was the leading tumor in AIDS patients in this country before the widespread use of highly active antiretroviral therapy and is currently the most commonly reported tumor in certain regions of Africa. KS is a highly vascularized tumor made up of multiple cell types but predominated by spindle cells apparently of endothelial origin. In the KS tumor spindle cells are infected with Kaposi's Sarcoma-associated herpesvirus (KSHV, also known as Human Herpesvirus 8 or HHV-8). Epidemiological studies have indicated that KSHV is a necessary etiologic agent of KS. KSHV is also associated with two B-cell lymphoproliferative diseases, primary effusion lymphoma and plasmablastic multicentric Castleman's disease. My laboratory studies the interactions of KSHV with the host endothelial and B-cell, focusing on how viral infection might lead to tumor formation. We are primarily studying viral genes involved in signal transduction and how viral alterations of host cell signaling may lead to cell growth and ultimately KS or lymphomas.