ABCG2 and neoplasm: Andersen et al. (2015) revealed that the mRNA expression of ABCG2 was decreased in cancer tissues. These findings underscore the importance of ABC transporters in the early steps of carcinogenesis and suggest that tumor formation might be related to epithelial barrier dysfunction. In addition, Kang et al. (2015) proposed that ABCG2 could be utilized as a prognostic biomarker.