title: Sustained Epigenetic Drug Delivery Depletes Cholesterol-Sphingomyelin Rafts from Resistant Breast Cancer Cells, Influencing Biophysical Characteristics of Membrane Lipids.
abstract: Cell-membrane lipid composition can greatly influence biophysical properties of cell membranes, affecting various cellular functions. We previously showed that lipid synthesis becomes altered in the membranes of resistant breast cancer cells (MCF-7/ADR); they form a more rigid, hydrophobic lipid monolayer than do sensitive cell membranes (MCF-7). These changes in membrane lipids of resistant cells, attributed to epigenetic aberration, significantly affected drug transport and endocytic function, thus impacting the efficacy of anticancer drugs. The present study's objective was to determine the effects of the epigenetic drug, 5-aza-2'-deoxycytidine (DAC), delivered in sustained-release nanogels (DAC-NGs), on the composition and biophysical properties of membrane lipids of resistant cells. Resistant and sensitive cells were treated with DAC in solution (DAC-sol) or DAC-NGs, and cell-membrane lipids were isolated and analyzed for lipid composition and biophysical properties. In resistant cells, we found increased formation of cholesterol-sphingomyelin (CHOL-SM) rafts with culturing time, whereas DAC treatment reduced their formation. In general, the effect of DAC-NGs was greater in changing the lipid composition than with DAC-sol. DAC treatment also caused a rise in levels of certain phospholipids and neutral lipids known to increase membrane fluidity, while reducing the levels of certain lipids known to increase membrane rigidity. Isotherm data showed increased lipid membrane fluidity following DAC treatment, attributed to decrease levels of CHOL-SM rafts (lamellar beta [Lβ] structures or ordered gel) and a corresponding increase in lipids that form lamellar alpha-structures (Lα, liquid crystalline phase). Sensitive cells showed marginal or insignificant changes in lipid profile following DAC-treatment, suggesting that epigenetic changes affecting lipid biosynthesis are more specific to resistant cells. Since membrane fluidity plays a major role in drug transport and endocytic function, treatment of resistant cells with epigenetic drugs with altered lipid profile could facilitate anticancer drug transport to overcome acquired drug resistance in a combination therapy.
authors.affiliation: Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic , 9500 Euclid Avenue, Cleveland, Ohio 44195, United States.
authors.forename: Vijay
authors.initials: V
authors.lastname: Raghavan
authors.affiliation: Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic , 9500 Euclid Avenue, Cleveland, Ohio 44195, United States.
authors.forename: Sivakumar
authors.initials: S
authors.lastname: Vijayaraghavalu
authors.affiliation: Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic , 9500 Euclid Avenue, Cleveland, Ohio 44195, United States.
authors.forename: Chiranjeevi
authors.initials: C
authors.lastname: Peetla
authors.affiliation: Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic , 9500 Euclid Avenue, Cleveland, Ohio 44195, United States.
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Yamada
authors.affiliation: Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic , 9500 Euclid Avenue, Cleveland, Ohio 44195, United States.
authors.forename: Megan
authors.initials: M
authors.lastname: Morisada
authors.affiliation: Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic , 9500 Euclid Avenue, Cleveland, Ohio 44195, United States.|Taussig Cancer Institute, Cleveland Clinic , Cleveland, Ohio 44195, United States.
authors.forename: Vinod
authors.initials: V
authors.lastname: Labhasetwar
mesh_terms: D001943:Breast Neoplasms / Q000378:metabolism; D002784:Cholesterol / Q000737:chemistry*; D005260:Female; D006801:Humans; D008563:Membrane Lipids / Q000737:chemistry*; D013109:Sphingomyelins / Q000737:chemistry*
chemical_list: D008563:Membrane Lipids; D013109:Sphingomyelins; D002784:Cholesterol