PROJECT SUMMARY SETD2 is mutationally inactivated in many cancer types including lung adenocarcinoma. In published work, we demonstrated that Setd2 inactivation has potent tumor promoting effects in an autochthonous mouse model of KRASG12D-driven lung adenocarcinoma. SETD2 uniquely catalyzes histone H3 lysine 36 trimethylation (H3K36me3), which marks actively transcribed gene bodies, facilitating chromatin resetting after gene transcription. In the current project, we aim to understand the provocative observation that SETD2 inactivation potently drives tumor cell proliferation due to a defect in one-carbon metabolism and activation of mTORC1 signaling. We demonstrate that SETD2 loss is associated with an enrichment in the abundance of S- adenosyl methionine (SAM) and multiple other metabolites that are part of SAM-adjacent metabolic pathways. We will test the hypothesis that the disuse of SAM that results from the lost activity of the SETD2 methyltransferase leads to SAM accumulation, enhanced one-carbon metabolism, and activation of mTORC1 signaling, all supporting cell growth and proliferation. Consistent with this hypothesis, we demonstrate that limiting dietary intake of methionine reduces KRAS-driven lung adenocarcinoma growth and reverses the effects of SETD2 inactivation. Thus, we will assess the efficacy of clinical and pre-clinical drugs that target the methionine cycle for potential synthetic lethal interactions with SETD2 deficiency. Finally, downstream of activated mTORC1 signaling we observe prominent transcriptional programs of hypoxia inducible factors (HIFs) and peroxisome proliferator-activated receptor γ (PPARγ) coactivator 1 α (PGC1α). Consistently, we observe multiple pathophysiological changes that are associated with increased activation of HIF and PGC1α transcription, such as alterations in mitochondrial biogenesis and the co-enhancement of oxidative phosphorylation and glycolytic pathways. Thus, we will test the requirement of these master transcription factors for effectuating phenotypes downstream of SETD2 inactivation.