The presence of numerous ATP-binding cassette (ABC) efflux transporters, such as P-glycoprotein (P-gp) and multidrug resistance (MDR) transporters, at the luminal surface of the brain capillaries as well as at the surface of tumour cells further contributes to lowering the actual chemotherapy concentration and exposition time of tumour cells [22]. The gene discussed is ABCB1; the disease is neoplasm.