Background: Pancreatic ductal adenocarcinoma (PDAC) is one of the worst solid malignancies in regard to outcomes and metabolic dysfunction leading to cachexia. It is alarming that PDAC incidence rates continue to increase and warrant the need for innovative approaches to combat this disease. Due to its relatively slow progression (10-20 years), prevention strategies represent an effective means to improve outcomes. One of the risk factors for many cancers and for pancreatic cancer in particular is diet. Hence, our objective is to understand how a diet rich in omega 3 and omega 6 polyunsaturated fatty acids affects the progression of this disease. Methods: We investigated polyunsaturated fatty acid (PUFA) effects on disease progression employing both in vitro (PDAC cell lines) and in vivo (EL-Kras and KC mice) approaches. Also, we gathered data from the National Health and Nutrition Examination Survey (NHANES) and the National Cancer Institute (NCI) from 1999 to 2017 for a retrospective observational study. Results: The consumption of PUFAs in a patient population correlates with increased PDAC incidence, particularly when the omega 3 intake increases to a lesser extent than omega 6. Our data demonstrate dietary PUFAs can be incorporated into plasma membrane lipids affecting PI3K/AKT signaling and support the emergence of membrane-targeted therapies. Moreover, we show that the phospholipid composition of a lipid nanoparticle (LNP) can impact the cell membrane integrity and, ultimately, cell viability after administration of these LNPs. Conclusions: Cancer prevention is impactful particularly for those with very poor prognosis, including pancreatic cancer. Our results point to the importance of dietary intervention in this disease when detected early and the potential to improve the antiproliferative effect of drug efficacy when combined with these regimens in later stages of pancreatic cancer.

Pancreatic cancer (PC) is one of the few cancers for which incidence and mortality continue to rise despite increasing knowledge of its etiology and risk factors. Amongst the latter, dietary patterns are significantly associated with PC risk. Due to its relatively slow progression, preventive strategies represent a simple means to improve outcomes. We are interested in understanding the influence of diet on PC prevention and have studied the effects of polyunsaturated fatty acids (PUFAs) in the progression of the disease both in vitro (via PC cell lines) and in vivo (via EL-KrasG12D and p48Cre/LSL-KrasG12D mouse models that recapitulate IPMN- and PanIN-like lesions, respectively). Our data demonstrate that dietary PUFAs are incorporated into plasma membrane phospholipids (PL) affecting signal transduction, particularly PI3K/AKT signaling, supporting the emergence of membrane-targeted therapies. We evaluated the effects of diets supplemented with omega-3 (ω-3) or omega-6 (ω-6) PUFAs on neoplastic lesion development. This work supports that ω-3 reduces while ω-6 accelerates lesion penetrance, tumor formation and proliferation associated with changes in pAKT. These results were also recapitulated in vitro to confirm that reduced activity of the PI3K/AKT pathway when incubated with Docosahexaenoic Acid (DHA), the primary component of the ω-3 enriched diet. This effect was abrogated by over-activation of the pathway when dosed with the main component of the ω-6 enriched diet, Linoleic Acid (LA). Since PI3K depends on its binding to PIP2 in the membrane for its activity, we next aimed to study if PUFAs were altering PL composition. By using IF and stably-transfected PC cells with a fluorescent translocation biosensor to monitor PIP2 and PIP3 lipids in the membrane, we discovered an effect of exogenous fatty acids expressed as a ratio of PIP2 to PIP3 in the plasma membrane. Enriched areas of membrane GFP staining (or PIP3) were observed in LA-treated Panc-1 cells. DHA treatment prevented PIP3 localization in the membrane of tumor cells, keeping the GFP signal diffuse in the cytoplasm. Using the PIP2 biosensor we sought to study the affinity of PI3K for PIP2 depending on the incorporation of DHA or LA in PIP2. DHA treatment reduced PI3K interaction (not total PI3K) with PIP2 resulting in lower levels of PIP3 in the membrane and reduced pAKT activation. Our results are encouraging because these PUFAs impinge on AKT, a downstream target of Kras which serves as a logical alternative to the elusive therapies for Kras and often toxic effects of PI3K/AKT pathway inhibition. Citation Format: Carolina Torres, Georgina Mancinelli, Emily Chen, Jose Cordoba-Chacon, Danielle Pins, Ronald McKinney, Sara Saeed, Karla Castellanos, Giulia Orsi, Megha Singhal, Sam Grimaldo, Poorna Chandra Rao Yalagala, Papasani Subbaiah, Cecilia Leal, Paul Grippo. Dietary fat influences pancreatic cancer progression by altering cell membrane lipid content to impact the PI3K/AKT pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2581.

Hepatic PPARγ expression is positively associated with the progression of non-alcoholic fatty liver disease and non-alcoholic steatohepatitis (NASH) in mice and humans. Although PPARγ agonists, thiazolidinediones (TZD), could be used to treat patients with NASH, these drugs reduced steatosis only in some patients with NASH, while it exacerbated steatosis in obese mice. Several mouse models with congenital knockout or overexpression of hepatic PPARγ have been used to study the actions and relevance of hepatocyte PPARγ in the development of steatosis. However, the mechanisms that hepatocyte PPARγ regulates to promote steatosis are not fully understood. Our group has previously reported that adult-onset hepatocyte-specific PPARγ knockout (aHepPPARγKO) mice fed a high fat diet (60% Kcal from fat) developed adiposity similar to PPARγ-intact controls, but aHepPPARγKO mice showed a dramatic reduction in steatosis, associated with reduced hepatic Cd36-mediated fatty acid uptake. Here, we fed aHepPPARγKO mice two different diets that produce steatosis and NASH to determine if loss of hepatocyte PPARγ expression reduced hepatic lipid levels associated with a reduction in Cd36 expression. Specifically, aHepPPARγKO and control mice were generated by injecting 10 wk-old male PPARγ-floxed littermate mice with a single dose of adeno-associated virus serotype 8 (AAV8) expressing hepatocyte-specific Cre recombinase or a AAV8-null vector, respectively. Two weeks later, aHepPPARγKO and control mice were fed either a methionine- and choline-deficient diet (MCD) for 3 weeks or a high-fat, cholesterol and fructose diet (HFCFD) diet for 8 weeks. The expression of hepatic PPARγ and Cd36 was significantly increased in MCD- and HFCF-fed control mice as compared to their respective control diet-fed controls. Of note, aHepPPARγKO reduced the expression of hepatic PPARγ (by >85%) and Cd36 (by >35-65%). Overall, MCD-fed mice showed reduced body weight, fat mass, and plasma cholesterol levels, while HFCFD-fed mice showed increased body weight and gonadal fat mass, and reduced plasma NEFA levels as compared to their respective control diet-fed littermates. Independent of diet, aHepPPARγKO did not alter body weight, adiposity, or the levels of plasma lipids. However, aHepPPARγKO reduced steatosis in HFCFD-fed mice, but not in MCD-fed mice. Interestingly, the levels of hepatic oleic [18:1(n-9)] and linoleic [18:2(n-6)] acids were, in fact, increased in MCD-fed aHepPPARγKO mice, while the levels of hepatic palmitoleic [16:1(n-7)] and oleic [18:1(n-9)] acids were reduced in HFCFD-fed aHepPPARγKO mice. Taken together, these data suggest that hepatocyte PPARγ serves as a steatogenic factor only in HFCFD-fed mice and not in MCD-fed mice, and this may be due to diet-dependent effects: nature of the development of steatosis and/or changes in adipose tissue.