The effect of combinations of the anthracycline aclarubicin and the topoisomerase II targeting drugs 4'-demethylepipodophyllotoxin-9-(4,6-O-ethylidene-beta-D-glucopyra noside) (VP-16) and 4'-(9-acridinylamino)methanesulfon-m-anisidide (m-AMSA) was investigated in a clonogenic assay