ABCG2 and non-small cell lung carcinoma: In particular, ABCG2 overexpression appears to show a significant correlation with decreased efficacy to topoisomerase I inhibitors such as irinotecan, SN-38, and topotecan in NSCLC (Bessho et al., 2006; Nagashima et al., 2006; Ohtsuka et al., 2010).