ABCG2 and neoplasm: To demonstrate that the retarded tumor growth observed after treatment with siRNA-loaded PEAL NPs + UTMD plus ADR was associated with ABCG2 downregulation in tumor cells, the mice were executed after treatment for 30 days, and all tumors were collected to extract total mRNA or protein to assess the levels of ABCG2 mRNA and protein expression using RT-PCR and WB analyses, respectively.