RESUMO
An in vitro pharmacological evaluation of a novel dinuclear platinum complex ([KL(2)](2)[Pt(2)I(6)], where L is 3-amino-5-methyl-5-phenylhydantoin; Ad-1) was carried out. The cytotoxicity of [KL(2)](2)[Pt(2)I(6)] against human tumor cell lines was assessed using the MTT [-3-(4,5-dimethylthiazol-2-Yl)-2,5-diphenyltetrazolium bromide] assay. The complex exerted concentration-dependent cytotoxic effects that were comparable or even superior to that of cisplatin. Moreover, the novel complex retained significant activity against CaCo-2 and Neuro-2A cells, which showed primary resistance to cisplatin. As evidenced by the rising level of genomic DNA fragmentation following treatment with [KL(2)](2)[Pt(2)I(6)], the cytotoxic effects are at least partly mediated by induction of apoptosis. The DNA binding of [KL(2)](2)[Pt(2)I(6)] and cisplatin were assessed using a 40-base fragment, whereby the present GG-motif is the recognition sequence of the nuclease BamH1. The DNA platination was determined after BamH1 treatment, 5% PAGE, and ethidium bromide staining. Cisplatin completely inhibited the BamH1-mediated fragmentation of the target DNA molecule. [KL(2)](2)[Pt(2)I(6)] also significantly inhibited the fragmentation of the target DNA sequence. The platination induced by [KL(2)](2)[Pt(2)I(6)] was better repaired by the nucleotide excision repair than the cisplatin lesions. As evidenced by electrophoresis mobility shift assay, the Ad-1-modified DNA was efficiently recognized and bound by the high mobility group box (HMGB)-1 protein, a member of the HMG domain proteins, which implies that the latter are most probably important for the cytotoxicity mode of action of this agent.
