Molecular insights into the antineoplastic mechanisms of mono- and bimetallic ruthenium(II) arene diamine complexes: a comprehensive evaluation.

Although platinum-based therapies are of central importance in oncology, their clinical benefits are often limited by systemic toxicity and the emergence of drug resistance. This study, a mechanistic continuation of our previous research on the cytotoxicity of organometallic Ru(II) complexes, presents a comprehensive in vitro investigation of the antineoplastic pathways of monometallic (Ru1) and bimetallic Ru(II) arene complexes (Ru2, Ru3) carrying diamine ligands. We evaluated their efficacy in prostate (PC-3, DU145) and colorectal (HT-29) cancer models, as well as in non-cancerous Vero cells. Morphological assessments and long-term wound healing tests revealed that the bimetallic complex (Ru3) significantly suppressed cellular motility and caused total cell death over a 7-day period. Immunocytochemical analysis of γ-H2AX foci confirmed that the complexes caused potent DNA double-strand breaks, and Ru3 demonstrated superior genotoxic activity in all cell lines. Mechanistic elucidation via flow cytometry and immunoblotting revealed that these complexes trigger a p53-dependent mitochondrial apoptotic pathway characterized by depolarization of the mitochondrial membrane potential, significant release of Cytochrome C, followed by Caspase-3 and PARP activation. Furthermore, treatment caused a remarkable reduction in anti-apoptotic Bcl-2 and Bcl-xL proteins. In particular, Ru1 exhibited unique antioxidant-like properties by reducing intracellular ROS and 8-OHdG levels in specific cell lines, suggesting a novel protective role in oxidative metabolism as well as its anticarcinogenic potential. Collectively, these results provide a potent molecular map for the activity of these Ru(II) diamine complexes and highlight Ru3 as a strong candidate for the development of next-generation, targeted anticancer therapies.