Comparative action of cobalt carbonyl complexes on cancer cells using human tumor xenografts.

We have previously shown that alkyne-cobalt carbonyl complexes inhibit the growth of human cancer cells. They were more active than dicobalt octacarbonyl, cobalt chloride or the free ligands. A difference in growth inhibition was observed among several cobalt complexes in two different cell lines indicating that the ligand may influence the activity of the complex. To further analyze cell type selectivity we compared the growth inhibition of two cobalt carbonyl complexes on eight different human tumor xenografts using a clonogenic assay which has been found to have a high predictive value, for further in vivo evaluation. For one compound as additional four cell lines were evaluated. Surprisingly we observed a large difference in the activity of the two complexes on cells originating from different tissues. Both compounds showed a comparable activity pattern indicating a common mechanism which seems to be different from that of the established metal-based anticancer agent cisplatin. Both complexes exceeded cisplatin in its in vitro anticancer activity.