In vitro antitumor activity of 2-acetyl pyridine 4n-ethyl thiosemicarbazone and its platinum(II) and palladium(II) complexes

The reaction of platinum(II) [Pt(II)] or palladium(II) [Pd(II)] with 2-acetyl pyridine 4N-ethyl thiosemicarbazone, HAc4Et (1) results in the complexes [Pt(Ac4Et) 2 ] (2) and [Pd(Ac4Et) 2 ] (3). In a panel of human tumor cell lines of different origins (breast, colon, and ovary cancers), and containing also cisplatin-refractory/resistant cell lines, the in vitro growth inhibitory effect of 1–3 was compared to that of cisplatin by using the sulforodamine B assay. After a 96-hour continuous treatment, both the thiosemicarbazone HAc4Et and the metal compounds [Pt(Ac4Et) 2 ] and [Pd(Ac4Et) 2 ] exhibit very remarkable growth inhibitory activities with mean IC 50 values of 0.9 n M (0.22– 2.47 n M ), 0.7 n M (0.15–2 n M ) and 0.5 n M (0.17–1.02 n M ), respectively. In contrast, cisplatin shows a markedly lower growth inhibitory potency, the mean IC 50 in the panel being 2.8 _ M (0.2–8 _ M ). In addition to their major cell growth inhibitory potency, complexes 1–3 are characterized by a growth inhibitory profi le different from that of cisplatin, being active towards cisplatin-refractory tumor cell lines. These fi ndings, along with the ability of completely overcoming acquired cisplatin resistance from either multifocal or reduced uptake origin, confi rm the antitumor potential of HAc4Et and support the hypothesis that both [Pt(Ac4Et) 2 ] and [Pd(Ac4Et) 2 ] complexes can be characterized by cellular pharmacological properties distinctly different from those of cisplatin