Phenotypic changes during tumor progression associated to hypoxia (MOC-6) [83] and EMT (MOC-7) [84] have also been related to the sensitivity of HB cells to doxorubicin, mainly because these changes produce up-regulation of ABC transporters involved in the efflux of doxorubicin such as MRP1, MRP2 and BCRP [49]. This evidence concerns the gene ABCG2 and neoplasm.