ABCG2 and neoplasm: Combining MDR drug reversal agents, RNAi/DNA, targeted drugs with nanocarrier drug delivery systems, through nonspecific internalization, reduce the efflux of drugs by ABC transporters in tumor cells, increases the uptake of drugs, and through RNAi/DNA Delivery, active targeting, and increased responsiveness to physiological stimuli can reverse tumor cell MDR.425, 426, 427