DNA-binding activity and cytotoxicity of the extended diphenylfuran bisamidines in breast cancer MCF-7 cells.

The DNA binding properties of three novel extended diphenylfuran bisamidines (1-3) possessing different dicationic terminal side chains were studied. The ultrafiltration assay showed that bisamidines 1-3 have significant affinity for DNA. The DNA-binding data for bisamidines 1-3 using homopolymers poly(dA-dT)- poly(dA-dT) and poly(dG-dC)- poly(dG-dC), indicated that these compounds show moderate specificity for AT base pairs. We studied the cytotoxicity effects of bisamidines 1-3, Hoechst 33258 and DAPI (4',6-diamidino-2-phenylindole) in cultured breast cancer MCF-7 cells. The bisamidines 1-3 showed comparable antitumour activity to Hoechst 33258, but were substantially more cytotoxic compared to DAPI. These data show that in broad terms the cytotoxic potency of bisamidines 1-3 in cultured breast cancer MCF-7 cells decreases with the size of the alkyl group substituent (cyclopropyl>isopropyl>cyclopentyl), in accord with their increases in DNA affinity, as shown by the binding constant values.