ABCB1 and cervical cancer: Promoter methylation of ABCB1, ABCC1, and ABCG2 has been determined in the cervix cancer line KB-3-1 and two drug-resistant sublines, KBC-1, selected against colchicine and overexpressing ABCB1, and KB-1089, selected against the thiosemicarbazone KP1089 and overexpressing ABCC1 and ABCG2 [142].