Abstract 255: Dietary amphiphilic polyphenols modulate the biophysical properties of plasma membrane organization and membrane-dependent macropinocytosis
Authors: Salinas Michael L. , Fuentes Natividad R. , Barhoumi Rola , Chapkin Robert S. 
Published: July 2017

Abstract
Ras-driven cancers exhibit a distinct high metabolic demand necessary for biosynthetic growth/proliferation, in some cases resulting in over stimulation of macropinocytosis, a process intended for nutrient acquisition. A hallmark of Ras-driven macropinocytosis is plasma membrane ruffling resulting in invaginations and the formation of macropinosomes, extracellular nutrient-packed vesicles distinct from other endocytic processes due to their size, independence of vesicle-coating proteins, and are the result of rapid polymerization and branching of cytoskeletal actin filaments. These cytoskeletal manipulations are driven by spatial/temporal regulators downstream of Ras along with lipid rafts and their components. Drugs and other extrinsic factors, e.g., polyunsaturated fatty acids, have been shown to biophysically modulate these lipid domains. We hypothesize that unique dietary polyphenolic amphiphilic molecules [1] modulate plasma membrane fluidity, [2] disrupt macropinocytosis, and [3] suppress macropinocytosis-dependent proliferation.
Young adult mouse colonocyte (YAMC) cells, expressing an HRas mutation, were treated with 1, 10, and 100 µM (+)-catechin or procyanidin B2 for 30 min. For macropinocytosis assessment, cells were stimulated with 25 ng/mL epidermal growth factor (EGF) for 5 min following a 30-minute pretreatment. Membrane order was measured in whole cells and giant plasma membrane vesicles (GPMV) utilizing a lipid-packing detection dye, Di-4-ANEPPDHQ, and assayed using a combination of fluorescence image-based flow cytometry (Amnis FlowSight) and confocal microscopy. In addition, macropinocytosis was determined by uptake of fluorescently labeled 70 kDa dextran (FITC-dextran). The uptake was visualized by fluorescence image-based flow cytometry. In the GPMV model, (+)-catechin increased membrane fluidity, and procyanidin B2 decreased membrane fluidity in a dose-dependent manner. In contrast, in the whole cell model, interaction of (+)-catechin and procyanidin B2 with the plasma membrane resulted in an increase in membrane fluidity in a dose-dependent manner.
Interestingly, plasma membrane fluidification in the whole cell model was associated with a significant 27-67% inhibition of macropinocytosis. These observations indicate that dietary amphiphilic molecules (DAMs) modulate plasma membrane organization, which is linked to macropinocytosis, an essential fuel-obtaining process. Establishing a role for DAMs in membrane-dependent oncogenesis is noteworthy because these molecules are innocuous and found in high abundance in a variety of fruits, vegetables, and walnuts.
This work was support by NIH grant R35CA197707.
Citation Format: Michael L. Salinas, Natividad R. Fuentes, Rola Barhoumi, Robert S. Chapkin. Dietary amphiphilic polyphenols modulate the biophysical properties of plasma membrane organization and membrane-dependent macropinocytosis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 255. doi:10.1158/1538-7445.AM2017-255