Role of acetyl-CoA in linking cancer cell metabolism and epigenetics

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PROJECT SUMMARY Pancreatic ductal adenocarcinoma (PDA) carries a dismal prognosis, due largely to the fact that it metastasizes early and is typically detected late, when tumors can no longer be resected. Obesity increases an individual’s risk of developing PDA, although the mechanisms driving this link are poorly understood. This proposal investigates the hypothesis that insulin signaling in PDA cells promotes metabolic alterations and changes in gene expression that facilitate tumor development and progression, potentially pointing towards new strategies to prevent PDA in at-risk populations or to improve PDA treatment outcomes. Histone acetylation is highly sensitive to the availability of the acetyl donor acetyl-CoA, and our previous work has defined a role for the metabolic enzyme ATP-citrate lyase (ACLY) in the regulation of histone acetylation levels in diverse mammalian cell types. Histone acetylation plays key roles in PDA tumorigenesis, although the mechanisms that drive altered histone acetylation are not well understood. In preliminary studies, we have found that insulin and insulin-like growth factor (IGF) stimulation of PDA cells results in ACLY Ser455 phosphorylation, increasing its activity, as well as elevated levels of global histone acetylation. ACLY is phosphorylated downstream of AKT, and AKT inhibition suppresses histone acetylation globally and at cancer- relevant loci. We hypothesize that elevated insulin/IGF levels promote metabolic and transcriptional remodeling in PDA cells, promoting tumor progression. To test this, we will define the role of insulin/IGF signaling in metabolic and epigenetic remodeling in KRAS mutant PDA cells, using a combination of hypothesis-driven and unbiased approaches. Finally, we will test the role of ACLY in mediating obesity-linked pancreatic tumorigenesis, as well as the potential to target acetyl-CoA-dependent processes to suppress tumor growth and improve therapeutic responses. This study will elucidate new mechanisms through which systemic metabolism influences cellular metabolism and the tumor epigenome. Findings from this study have potential to provide a mechanistic rationale for nutritional recommendations for PDA patients and/or to identify new therapeutic targets to prevent tumor recurrence after surgical resection or to use in conjunction with chemotherapy to improve its efficacy.