The ABC transporter proteins ABCB1 (MDR1/P-glycoprotein), ABCC1, and ABCG2 permit the transmembrane transport of different substrates, including chemotherapeutic agents; thus, they are implicated in multidrug resistance (MDR) in different types of tumors, such as lung cancer—reviewed in [92]. The gene discussed is ABCB1; the disease is lung carcinoma.