Search for human DNA topoisomerase II poisons in the group of 2,5-disubstituted-1,3,4-thiadiazoles

A series of six 2,5-disubstituted 1,3,4-thiadiazole derivatives was synthesized and examined for cytotoxic activity in MCF-7 and MDA-MB-231 breast cancer cells. MTT assay confirmed that 2-(3-fluorophenylamino)-5-(3-hydroxyphenyl)-1,3,4-thiadiazole (2), 2-(4-bromophenylamino)-5-(2,4-dichlorophenyl)-1,3,4-thiadiazole (3), 2-(4-fluorophenylamino)-5-(2,4-dichlorophenyl)-1,3,4-thiadiazole (4), had ability to inhibit MCF-7 and MDA-MB-231 cells proliferation. The IC50 values for the mentioned compounds ranged between 120 and 160 μM (with respect to MCF-7 cells) and from 70 to 170 μM (with respect to MDA-MB-231 cells). It turned out, moreover, that compound 2 is a human topoisomerase II (topoII) catalytic inhibitor whereas the two other compounds (i.e. 3 and 4) are capable of stabilizing DNA-topoII cleavage complex and thus are topoII poisons.