Kaposi’s sarcoma-associated herpesvirus (KSHV) is the causal agent of Kaposi’s sarcoma (KS) and several other malignancies. We have discovered that, unlike most other types of cancer cells that are addicted to glucose and aerobic glycolysis, KSHV-transformed cells do not depend on glucose and have a reduced level of aerobic glycolysis. Instead, KSHV-transformed cells are addicted to glutamine. More surprisingly, glutamine is primarily shunted to the syntheses of nucleotides and amino acids. To maintain the metabolic flow and clear the toxic products, KSHV hijacks the citrulline-urea cycle by upregulating the key rate-limiting metabolic enzyme argininosuccinate synthase 1 (ASS1). Significantly, ASS1 is essential for the proliferation and survival of KSHV- transformed cells and upregulation of the citrulline-urea cycle further provides an essential STAT3 oncogenic signal by inducing nitric oxide. Our hypothesis is that KSHV encodes specific gene(s) to hijack the citrulline-urea cycle to support the proliferation and survival of KSHV-transformed cells, and hence targeting this pathway is effective for treating KSHV-induced tumors. We have developed an efficient model of KSHV-induced cellular transformation and tumorigenesis, three-dimensional (3D) culture models KSHV- transformed cells, and advanced metabolic profiling and tracing technologies, all of which are particularly useful for testing this novel hypothesis. We will examine the essential roles of ASS1 and citrulline-urea cycle for maintaining metabolic flow, clearing toxic products and activating STAT3 pathway to support KSHV-induced cellular transformation (Aim 1); determine the mechanism by which ASS1 and active citrulline-urea cycle activate the STAT3 pathway to support KSHV-induced cellular transformation (Aim 2); determine the mechanism by which KSHV upregulates ASS1 and hijacks the citrulline-urea cycle (Aim 3); and determine the therapeutic potential of targeting key enzymes in the citrulline-urea cycle for treating KSHV-induced tumorigenesis (Aim 4). The proposed project is highly significant as it will test a novel hypothesis of KSHV manipulation of a key cellular metabolic pathway using multidisciplinary innovative approaches and model systems. It is our expectations that accomplishment of this project will lead to the identification of novel cancer drivers and vulnerabilities of KSHV-induced cancers, which could provide a scientific basis for developing novel therapies.