ABSTRACT Clear cell renal cell carcinoma (ccRCC), the most common type of kidney cancer, is characterized by deregulated hypoxic signaling, metabolic defects, and complex immune cell infiltrate in the tumor microenvironment (TME). Loss of the oxygen sensing gene, von Hippel Lindau (VHL), is a critical early event in ccRCC pathogenesis and promotes stabilization of hypoxia inducible (transcription) factors (HIF) that upregulate pro-growth signaling pathways, including aerobic glycolysis, regardless of oxygen availability. This phenomenon is termed “pseudo- hypoxia.” The most frequent immune types affecting ccRCC are functionally impaired CD8 tumor infiltrating lymphocytes (CD8 TIL) and metabolically enhanced tumor associated macrophages (TAM). Advancements in immune oncology have led to improved overall patient outcomes with immune checkpoint blockade (ICB) therapy; however, current modalities do not result in durable responses for the majority of ccRCC patients. I propose that features linked to pseudo-hypoxic signaling promote alterations in cancer cell energetic requirements that impact immune cell function in the TME and revealing these aspects may provide new opportunities for therapy. My preliminary data indicate that Vhl loss favors a mature TAM myeloid phenotype with enhanced mitochondrial metabolism in murine RCC, and this result is consistent with enhanced metabolism observed in the myeloid compartment of human ccRCC. Additionally, TAM suppression of CD8 TIL may be enhanced by specific interactions with cancer cells, though exact TAM functions are not understood. In this proposal, I will test the hypothesis that pseudo-hypoxic signals from cancer cells in the TME preferentially support a metabolically active TAM subset that promotes CD8 TIL suppression and that inhibiting TAM activity will enhance the CD8 TIL response to ICB therapy. To test the cancer cell pseudo- hypoxic effect on TAM function I have developed a fine needle aspiration-based patient-derived organoid (FNA- PDO) model that recapitulates key factors of the TME in human tumors. I will also employ a pair of murine syngeneic Renca cell line models (Vhl WT and Vhl KO) to address the impact of pseudo-hypoxia on the TME in vivo. I will: (1) Test if pseudo-hypoxia supports a unique TAM phenotype with distinct metabolism; and (2), Test the role of TAM in T cell suppression and ICB response. Ultimately, these studies will advance our current understanding of kidney cancer biology by demonstrating mechanisms that shape the TME and highlighting new strategies to improve immunotherapy.