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

Inhibition of the growth of the human ovarian cancer cell line A2780 by org anometallic 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, a cetonitrile, or isonicotinamide, or X,Y is ethylenediamine (en) or N-ethyle thylenediamine, has been investigated. The X-ray crystal structures of the complexes [(eta (6)-p-cymene)Ru(en)Cl]PF6 (5), [(eta (6)-p-cymene)RuCl2(iso nicotinamide)] (7), and [(eta (6)-biphenyl)Ru(en)Cl]PF6 (9) are reported. T hey have "piano stool" geometries with eta (6) coordination of the arene li gand. 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 o f 5), 9, and 10 (ethylethylenediamine analogue of 9) were as active as carb oplatin. 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 monofun ctional 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 fr om that of the Ru(III) complex currently on clinical trial.