ABCG2 and cancer: Based on the important role of ABC transporters in the MDR of cancers, numerous inhibitors of ABC transporters were discovered to improve the efficacy of anticancer agents in resistant tumor tissues in recent decades.8,9 However, most of these drugs failed in the clinic because of undesired side effects and toxicity issues.10,11 In addition, identifying novel anti-tumor candidates with low probability to develop resistance in cancers may also be another feasible strategy to avoid MDR.