Among these, Ko143, a highly potent analogue of fumetremorgin C1, has been shown to re-sensitize human cancer cell lines with acquired SN-38 resistance and significant upregulation of ABCG2 mRNA as well as to enhance the efficacy of irinotecan in ABCG2-expressing CRC xenograft tumor models [41,42]. Here, ABCG2 is linked to colorectal carcinoma.