ABCB1 and breast neoplasm: While ABCB1 expression was significantly downregulated in post-treatment breast tumour specimens compared with non-neoplastic tissues [44], ABCB1 was related to resistance to 5-fluorouracil; Adriamycin and cyclophosphamide (FAC)/5-fluorouracil, epirubicin and cyclophosphamide (FEC) chemotherapy in another study involving 59 patients [45].