In lung cancer cells, several ABC proteins are involved in the reduction of intracellular drug concentrations: ABCA1, ABCA2 (ABC transports not classified as multidrug-resistant proteins), ABCB1 (P-glycoprotein/multidrug resistance protein 1; MDR1), and the multidrug resistance-associated proteins (MRPs) ABCB4, ABCB11, and ABCC1-6 as well as ABCC10, ABCC11, and ABCG2 (BCRP/MXR) [58]. Here, ABCG2 is linked to lung cancer.