Collateral sensitivity: ABCG2-overexpressing cells are more vulnerable to oxidative stress. 
Multidrug resistance (MDR), which is the main obstacle to cancer chemotherapy, is mainly due to overexpression of ATP-binding cassette (ABC) transporters, especially ABCB1 (P-glycoprotein), ABCC1 (MRP1), and ABCG2 (BCRP).  A novel idea to overcome MDR is that of collateral sensitivity, i.e., finding a treatment to which cells overexpressing ABC transporters are more sensitive than cells that do not overexpress them.  In this study we demonstrate for the first time that MDCKII-BCRP cells, overexpressing ABCG2, are more vulnerable to exogenous oxidative stress induced by several oxidants, viz.  paraquat, menadione, hydrogen peroxide, tert-butylperoxide, and 2,2-azobis(2-methylpropionamidine) dihydrochloride.  MDCKII-BCRP cells have significantly decreased glutathione level and decreased activities of glutathione S-transferase and glutathione reductase, which may underlie their augmented vulnerability to oxidative stress.  These results suggest the possibility of using agents that induce oxidative stress to selectively kill cells overexpressing BCRP.