Discovery of a strongly apoptotic ruthenium complex through combinatorial coordination chemistry

• Published in: Dalton transactions : an international journal of inorganic chemistry Vol. 39; no. 35; pp. 8177 - 8182
• Main Authors: Mulcahy, Seann P, Gründler, Katharina, Frias, Corazon, Wagner, Laura, Prokop, Aram, Meggers, Eric
• Format: Journal Article
• Language: English
• Published: England 21.09.2010
• Subjects: Antineoplastic Agents - chemistry; Antineoplastic Agents - toxicity; Apoptosis; Cell Line, Tumor; Combinatorial Chemistry Techniques; Coordination Complexes - chemistry; Coordination Complexes - toxicity; Drug Evaluation, Preclinical; HeLa Cells; Humans; Membrane Potential, Mitochondrial - drug effects; Organometallic Compounds - chemistry; Organometallic Compounds - toxicity; Ruthenium - chemistry; Structure-Activity Relationship
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c0dt00034e

A strategy for combinatorial parallel coordination chemistry is introduced that provides access to libraries of tris-heteroleptic ruthenium complexes in an economical fashion. Using this method, a library of 560 constitutionally unique, monocationic ruthenium complexes was synthesized, followed by a screening for anticancer activity and resulting in the identification of three hits with promising cytotoxic properties in HeLa cancer cells. A subsequent structure-activity relationship led to the discovery of the surprisingly simple anticancer complex [Ru(tBu(2)bpy)(2)(phox)]PF(6) (complex 1), with tBu(2)bpy = 4,4'-di-tert-buty-2,2'-bipyridine and Hphox = 2-(2'-hydroxyphenyl)oxazoline, displaying an LC(50) value in HeLa cells of 1.3 microM and 0.3 microM after incubation for 24 and 72 h, respectively. Complex 1 also shows remarkable antiproliferative and apoptotic properties at submicromolar concentrations in more clinically relevant Burkitt-like lymphoma cells. A reduction of the mitochondrial membrane potential by 1 indicates the involvement of the intrinsic pathway of programmed cell death. Further investigations reveal that 1 requires caspase-3 for the induction of apoptosis but is insensitive to the proapoptotic and antiapoptotic proteins Smac and Bcl-2, respectively.