Abstract 2581: Dietary fat influences pancreatic cancer progression by altering cell membrane lipid content to impact the PI3K/AKT pathway
Authors: Torres Carolina , Mancinelli Georgina , Chen Emily , Cordoba-Chacon Jose , Pins Danielle , McKinney Ronald , Saeed Sara , Castellanos Karla , Orsi Giulia , Singhal Megha , Grimaldo Sam , Yalagala Poorna Chandra Rao , Subbaiah Papasani , Leal Cecilia , Grippo Paul 
Published: July 2021

Abstract
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.