ABCB1 and cancer: ATP-binding cassette (ABC) transporters are members of a transport system superfamily that play a crucial role in the development of multidrug resistance.5 Numerous studies have shown that overexpression of ABC transporter genes can cause drug resistance in various cancer types.6 P-glycoprotein, also known as ABCB1, is encoded by MDR1, which belongs to the human ABCB (MDR/TAP) family and is a well-known multidrug-efflux transporter.