ABCB1 and neoplasm: Another serious limitation for the extended clinical use of MTAs for cancer therapy is the rapid development of tumor resistance through diverse mechanisms, including the overexpression of ABC-transporters, such as P-glycoprotein [15,16,17], altered expression of specific β-tubulin isotypes [18], mutations in β-tubulin, delay of G2/M transition, impairment of the mitotic checkpoints, and apoptotic pathways which were extensively reviewed [19].