Iminophosphorane-organogold(III) complexes induce cell death through mitochondrial ROS production

Gold compounds are being investigated as potential antitumor drugs. Some gold(III) derivatives have been shown to induce cell death in solid tumors but their mechanism of action differs from that of cisplatin, since most of these compounds do not bind to DNA. We have explored cellular events triggered by three different iminophosphorane-organogold(III) compounds in leukemia cells (a neutral compound with two chloride ligands Au{κ²-C,N-C₆H₄(PPh₂ = N(C₆H₅)-2}Cl₂] 1, and two cationic compounds with either a dithiocarbamate ligand Au{κ²-C,N-C₆H₄(PPh₂ = N(C₆H₅)-2}(S₂CN-Me₂)]PF₆2, or a water-soluble phosphine and a chloride ligand Au{κ²-C,N-C₆H₄(PPh₂ = N(C₆H₅)-2}(P{Cp(m-C₆H₄-SO₃Na)₂}₃) Cl]PF₆3). All three compounds showed higher toxicity against leukemia cells when compared to normal T-lymphocytes. Compounds 1 and 2 induced both necrosis and apoptosis, while 3 was mainly apoptotic. Necrotic cell death induced by 1 and 2 was Bax/Bak- and caspase-independent, while apoptosis induced by 3 was Bax/Bak-dependent. Reactive oxygen species (ROS) production at the mitochondrial level was a critical step in the antitumor effect of these compounds.