ABCG2 and neoplasm: Compared with the tumor tissue from normal saline treated mice, the expression of Bax and caspase-3 were obviously up-regulated, and the expression of p-gp, MRP-1, BCRP, NF-κB and BCL-2 was remarkably down-regulated in the tumor tissue from DOX/RES-loaded NPS treated tumor-bearing mice.