Kaposi's Sarcoma (KS) is the most common tumor associated with HIV infection. KS represents a vascular proliferation characterized by multiple lesions at initial presentation. an identical tumor develops in other settings without HIV infection, including the classic form seen predominantly in older Eastern European men, an African form, renal transplant recipients, and iatrogenically induced by glucocorticoids disease. Clinically, KS is a heterogeneous course that appears to be independent of the severity of immunodeficiency. KS in highly vascular angiogenic tumor that appears to be of endothelial cell origin. Gill's group has demonstrated in the past that angiogenic factors bFGF, VEGF and IL8 and inducers of angiogenesis IL6, TGFbeta, IL1beta and TNFalpha are all expressed in KS cells and more recently that VEGF is an autocrine factor, a permeability factor and a survival factor for KS cells in culture. He has also found that all known members of the VEGF family and VEGF-R family are expressed in both KS cell lines and KSHV infected EC cultures. He proposes that VEGF is the critical growth factor for KS and that VEGF/VEGF-R proteins represent the convergence points for all KS growth factor cascades. Therefore, he proposes to both demonstrate this and define the roles of individual VEGF/VEGF- R family members in both the KS Y-1 spindle cell line and in the recently developed KSHV infected BMEC system of Flore et al, as well as confirm expression of all of these proteins in primary KS tumor tissue. A comprehensive set of experiments focused on the following three Specific Aims are proposed. Specific Aim 1 is designed to use specific reagents to define and compare the expression and roles of VEGF-A, VEGF-B, VEGF-C, VEGF-D and PIGF, including the use of antisense phosphorothioate oligonucleotide inhibitors and VEGF-R antibodies to examine effects on cell proliferation, migration and survival. The new Specific Aim 2 involves an investigation of the importance of the greatly increased constitutive levels of ERK activation (an apparent downstream VEGF effect) found in KS cells compared to normal HUVEC or skin cells. Whether this is needed for cell survival and whether KSHV infection also induces ERK activation as a appropriate critical event will be examined as well as pharmacological intervention at other stages of MAPK signal transduction. New Specific Aim 3 represents an attempt to establish the hierarchy and possible convergence of IL1beta and IL6 autocrine growth factor action in relation to VEGF survival signaling by individually blocking all three loops and studying the impact on cell growth, migration, apoptosis and second messenger activity.