The findings showed that in HeLa-UGT1A9, Ko143, a chemical inhibitor of breast cancer resistance protein (BCRP), significantly suppresses the efflux of diosmetin and chrysoeriol glucuronides and enhances their intracellular glucuronides in a dose-dependent manner, which increases cytotoxicity in A549 and HepG2 tumor cell lines. This evidence concerns the gene ABCG2 and neoplasm.