Cytotoxicity of a transferrin‐adriamycin conjugate to anthracycline‐resistant cells

Conjugates of adriamycin coupled to transferrin by glutaraldehyde are cytotoxic to human promyelocytic (HL‐60) and erythroleukemic (K562) cells. Growth inhibition of adriamycin‐sensitive cells, as evaluated by thymidine incorporation and the MTT‐assay, was higher for conjugates than for free adriamycin. The cytotoxicity toward adriamycin‐resistant K562 and HL‐60 cells was 3‐fold and more than 10‐fold higher, respectively, for the transferrin‐adriamycin conjugate than for the free drug. The effect of the conjugate was dependent on its adriamycin content, i.e., on its coniugation number. © 1992 Wiley‐Liss, Inc.