Impact of dietary lipids on pancreas cancer initiation and progression

PROJECT SUMMARY Despite advances in cancer treatment, the five-year survival rate for pancreatic ductal adenocarcinoma (PDA) is 12%. Obesity has been linked to PDA risk epidemiologically, implying that diet and metabolism have roles in PDA tumor initiation, but the biological basis for this correlation is not clear. Data from our labs shows that high fat diet (HFD) can accelerate PDA development in a Ptf1a-Cre/LSL-KrasG12D (KC) mouse model of PDA. Further, recent work has shown that acute inflammation can epigenetically prime acinar cells in the pancreas for tumorigenesis. We hypothesize that HFD, which has been clearly demonstrated to alter inflammation in a range of tissues, can similarly prime the pancreas to promote or prevent tumor development. The two aims in our proposal investigate effects of two HFDs chosen specifically because they are enriched for classes of fatty acids known to have distinct biological effects. Aim 1 examines the effects of a HFD comprised of lard (HFLD), which contains mostly saturated long chain fatty acids that are associated with obesity, on PDA tumorigenesis. To study how HFLD may prime the pancreas for tumor growth, we will use scRNA-seq and scATAC-seq to define dietary effects on healthy pancreas. We will also leverage our newly developed CYTO-Tag mouse to rapidly isolate acinar cells for metabolomics, thus allowing us to draw connections between changes in gene expression, chromatin structure, and metabolism in acinar cells in the context of HFLD. We will then use a tamoxifen- inducible Ptf1a-CreERT/LSL-KrasG12D (iKC) model to study the effects of HFLD on tumor growth, and use an orthotopic tumor model generated from HFLD-conditioned iKC acinar cells to distinguish between acinar cell- intrinsic and -extrinsic tumor growth mechanisms. In Aim 2, we will examine the effects of a HFD comprised of coconut oil (HFCD), isocalorically matched with the HFLD, on PDA tumor growth. Coconut oil is comprised of medium chain saturated fatty acids. It is a common dietary fat “swap” patients use when attempting to eat healthier, particularly in a ketogenic diet, but the effects of HFCD on PDA tumor growth are not known. We will use scRNA-seq, scATAC-seq, and our CYTO-Tag mouse to characterize the effects of HFCD on healthy pancreas, followed by tumor growth experiments in iKC mice. We will begin to pinpoint mechanisms underlying any observed effects on tumor growth through studies in orthotopic tumor models using HFCD-conditioned acinar cells. Aim 2 will define the effects of HFCD on tumor growth for the first time, and because our HFLD and HFCD are isocaloric, we will be able to directly compare effects of these diets on tumor growth. Understanding the molecular basis underlying differential effects of compositionally distinct HFD will enable more informed dietary recommendations for patients to potentially reduce cancer risk.