ABCG2 and cervical squamous intraepithelial neoplasia: Moreover, Ippolito et al. previously reported the link between CIN and drug resistance through the upregulation of ATP binding cassette subfamily G member 2 (ABCG2), a drug efflux pump, due to the amplification of its upstream regulator MAPK13 in topotecan-resistant tumor cells generated from treatment using CIN-inducing drug nocodazole.17 Together, these show that CIN fuels genomic diversity, upon which selection works, leading to the development of drug resistance.