ABCG2 and cancer: Consistent with this observation, higher levels of reducing equivalents (NADPH/GSH) were observed in MCF-7/MX cells and they were more resilient to oxidative stress, in line with the notion that glutamine metabolism plays a major role in maintaining cancer cell redox homeostasis (38) and in agreement with previous studies by our lab (3) and others (39) showing that ABCG2 protects against inducers of oxidative stress including radiation and nutrient deprivation.