In the present study, we discovered that the mRNA and protein expression levels of MDR1 were higher in breast tumor tissues and cells than that in normal breast tissues and cells and MDR1 overexpression obviously decreased sensitivity to ADR and PTX induced by Gal-1 knockdown in MCF-7/PTX and MCF-7/ADR cells by promoting cell proliferation and suppressing apoptosis. This evidence concerns the gene ABCB1 and breast neoplasm.