What is most important is that these compounds only slightly influenced the expression of the ABCB1, ABCC1, and ABCC2 genes and the level of the MDR1 protein in the studied colon LS 174T and prostate DU 145 tumor cells, especially for the C-2028, C-2045, and C-2053 derivatives. This evidence concerns the gene ABCC2 and neoplasm.