THE POTENTIAL OF IRON CHELATORS OF THE PYRIDOXAL ISONICOTINOYL HYDRAZONE CLASS AS EFFECTIVE ANTIPROLIFERATIVE AGENTS .2. THE MECHANISM OF ACTION OF LIGANDS DERIVED FROM SALICYLALDEHYDE BENZOYL HYDRAZONE AND 2-HYDROXY-1-NAPHTHYLALDEHYDE BENZOYL HYDRAZONE

We have recently screened 36 analogues of the lipophilic iron (Fe) che lator, pyridoxal isonicotinoyl hydrazone (PIH), for their antiprolifer ative effect (Richardson et al, Blood 86:4295, 1995). Of these compoun ds, 1 chelator derived from salicylaldehyde benzoyl hydrazone (206) an d 4 ligands derived from 2-hydroxy-1-naphthylaldehyde benzoyl hydrazon e (308, 309, 311, and 315) showed pronounced antiproliferative activit y, being far more effective than desferrioxamine (DFO). The present st udy was designed to investigate in detail the mechanism of action of t hese PIH analogues in a variety of neoplastic cell lines. This investi gation showed that the analogues were far more active than DFO at inhi biting cellular proliferation and H-3-thymidine, H-3-leucine, and H-3- uridine incorporation. Additional experiments showed that, in contrast to DFO, the 5 analogues were potent at preventing Fe-59 uptake from t ransferrin (Tf) and increasing Fe-59 release from cells at concentrati ons as low as 10 mu mol/L. Examination of the distribution of Fe-59 in neoplastic cells using native polyacrylamide gel electrophoresis (PAG E)/ Fe-59-autoradiography showed that most of the Fe-59 taken up from Tf was incorporated into ferritin, although 3 other previously unrecog nized components (bands A, B, and C) were also identified. Band C comi grated with Fe-59-citrate and was chelated on incubation of neuroblast oma cells with DFO, PIH, or the PIH analogues, with this compartment b eing the main intracellular target of these ligands. Further work show ed that the effects of the chelators at inducing characteristics consi stent with apoptosis or necrosis were cell line-specific, and while DF O increased the percentage of cells in the G(0)/G(1) phases in all cel l types, the effect of analogue 311 on the cell cycle was variable dep ending on the cell line. This study provides further evidence for the potential use of these Fe chelators as anticancer agents. (C) 1997 by The American Society of Hematology.