Inhibition of cancer cell growth by ruthenium(II) arene complexes.

Inhibition of the growth of the human ovarian cancer cell line A2780 by organometallic ruthenium(II) complexes of the type [(eta(6)-arene)Ru(X)(Y)(Z)], where arene is benzene or substituted benzene, X, Y, and Z are halide, acetonitrile, or isonicotinamide, or X,Y is ethylenediamine (en) or N-ethylethylenediamine, has been investigated. The X-ray crystal structures of the complexes [(eta(6)-p-cymene)Ru(en)Cl]PF(6) (5), [(eta(6)-p-cymene)RuCl(2)(isonicotinamide)] (7), and [(eta(6)-biphenyl)Ru(en)Cl]PF(6) (9) are reported. They have "piano stool" geometries with eta(6) coordination of the arene ligand. Complexes with X,Y as a chelated en ligand and Z as a monofunctional leaving group had the highest activity. Complexes 5, 6 (the iodo analogue of 5), 9, and 10 (ethylethylenediamine analogue of 9) were as active as carboplatin. Hydrolysis of the reactive Ru-Cl bond in complex 5 was detected by HPLC but was suppressed by the addition of chloride ions. Complex 5 binds strongly and selectively to G bases on DNA oligonucleotides to form monofunctional adducts. No inhibition of topoisomerase I or II by complexes 5, 6, or 9 was detected. These chelated Ru(II) arene complexes have potential as novel metal-based anticancer agents with a mechanism of action different from that of the Ru(III) complex currently on clinical trial.

Kinetics of formation and stability of [Pt(dien)]2+ complexes with octamer and 14-mer DNA oligonucleotides containing a GG sequence.

Reaction of [Pt(dien)Cl]+ (1) with the 14-mer oligonucleotide 5'-d(ATACATGGTACATA) (I) gave rise to two major species which corresponded to the 5'-G and 3'-G platinated monofunctional adducts, and a minor amount of the bis-platinated adduct formed during the later stages of the reaction. The reaction of (1) with the related octamer 5'-d(ATA-CATGG) (II) was also investigated. Kinetic data obtained by HPLC showed that the 5'-G and 3'-G bases of the 14-mer oligonucleotide were platinated at similar rates: the second-order rate constant is 53 x 10(-2) M-1 s-1 at 298 K in 0.1 M NaClO4. However, the platination rate of 5'-G of the octamer (II) (k = 69 x 10(-2) M-1 s-1) was enhanced by a factor of three compared to the rate of platination at 3'-G (k = 22 x 10(-2) M-1 s-1). All the adducts were separated by HPLC and characterized by NMR spectroscopy, enzymatic digestion and MALDITOF mass spectrometry. 1H and 15N NMR shifts suggest that there are distinct conformational differences between 14-mer duplexes platinated at 5'-G (I5' ds) and 3'-G (I3' ds). Molecular mechanics modelling indicates that rotation around the Pt-N7 bond is more restricted in the case of the 5'-G adduct than in that of the 3'-G adduct. The binding of {Pt(dien)}2+ to 5'-GN7 and 3'-GN7 in the monofunctional adducts of (I) was shown to be reversible upon the addition of high concentrations of chloride ions.