title: Cytotoxicity and mechanism of action of a new ROS-generating microsphere formulation for circumventing multidrug resistance in breast cancer cells.
abstract: Multidrug resistance (MDR) is one of the main challenges in the treatment of breast cancer. A new microsphere formulation able to generate reactive oxygen species (ROS) locally was thus investigated for circumventing MDR in breast cancer cells in this work. Glucose oxidase (GOX) was encapsulated in alginate/chitosan hydrogel microspheres (ACMS-GOX). The in vitro cytotoxicity of ACMS-GOX to murine breast cancer EMT6/AR1.0 cells, which overexpress P-glycoprotein (P-gp), was evaluated by a clonogenic assay. The mechanism of the cytotoxicity of ACMS-GOX was investigated by using various extracellular and intracellular ROS scavengers and antioxidant enzyme inhibitors. The effect of lipid peroxidation and cellular uptake of GOX was also evaluated. ACMS-GOX exhibited similar dose and time-dependent cytotoxicity to EMT6/AR1.0 cells as to their wild-type EMT6/WT parent cells, in effect circumventing the MDR phenotype of EMT6/AR1.0 cells. Extracellular H(2)O(2) and intracellular hydroxyl radical were found to play critical roles in the cytotoxicity of ACMS-GOX. Cellular uptake of GOX was negligible and thus not responsible for intracellular ROS generation. Combining ACMS-GOX with intracellular antioxidant inhibitors-enhanced cytoxicity. This work demonstrates that the ACMS-GOX are effective in circumventing P-gp-mediated MDR in breast cancer cells.
authors.affiliation: Leslie Dan Faculty of Pharmacy, University of Toronto, 144 College Street, Toronto, ON M5S 3M2, Canada.
authors.forename: Qun
authors.initials: Q
authors.lastname: Liu
authors.forename: Adam
authors.initials: A
authors.lastname: Shuhendler
authors.forename: Ji
authors.initials: J
authors.lastname: Cheng
authors.forename: Andrew Michael
authors.initials: AM
authors.lastname: Rauth
authors.forename: Peter
authors.initials: P
authors.lastname: O'Brien
authors.forename: Xiao Yu
authors.initials: XY
authors.lastname: Wu
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage*; D001943:Breast Neoplasms / Q000378:metabolism*; D045744:Cell Line, Tumor; D018432:Drug Resistance, Multiple / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D005260:Female; D005949:Glucose Oxidase / Q000008:administration & dosage*; D006861:Hydrogen Peroxide / Q000378:metabolism; D051379:Mice; D008863:Microspheres; D017382:Reactive Oxygen Species / Q000008:administration & dosage*
chemical_list: D000970:Antineoplastic Agents; D017382:Reactive Oxygen Species; D006861:Hydrogen Peroxide; D005949:Glucose Oxidase