A cytotoxic nitrido-osmium(VI) complex induces caspase-mediated apoptosis in HepG2 cancer cells

A review on metal complexes and its anti-cancer activities: Recent updates from in vivo studies

Research into cancer therapeutics has uncovered various potential medications based on metal-containing scaffolds after the discovery and clinical applications of cisplatin as an anti-cancer agent. This has resulted in many metallodrugs that can be put into medical applications. These metallodrugs have a wider variety of functions and mechanisms of action than pure organic molecules. Although platinum-based medicines are very efficient anti-cancer agents, they are often accompanied by significant side effects and toxicity and are limited by resistance. Some of the most studied and developed alternatives to platinum-based anti-cancer medications include metallodrugs based on ruthenium, gold, copper, iridium, and osmium, which showed effectiveness against many cancer cell lines. These metal-based medicines represent an exciting new category of potential cancer treatments and sparked a renewed interest in the search for effective anti-cancer therapies. Despite the widespread development of metal complexes touted as powerful and promising in vitro anti-cancer therapeutics, only a small percentage of these compounds have shown their worth in vivo models. Metallodrugs, which are more effective and less toxic than platinum-based drugs and can treat drug-resistant cancer cells, are the focus of this review. Here, we highlighted some of the most recently developed Pt, Ru, Au, Cu, Ir, and Os complexes that have shown significant in vivo antitumor properties between 2017 and 2023.

Cytotoxic cis-ruthenium(III) bis(amidine) complexes

In chemotherapy, the search for ruthenium compounds as alternatives to platinum compounds is proposed because of their unique properties. However, the geometry effect of ruthenium complexes is sparely investigated. In this paper, we report the synthesis of a series of bis(acetylacetonato)ruthenium(III) complexes bearing two amidines (1-) in a cis configuration. These complexes are highly cytotoxic against various cancer cell lines, including a cisplatin-resistant cell line. In vitro studies suggested that the representative complex can induce cell cycle G0/G1 phase arrest, decrease the mitochondrial membrane potential, elevate the intracellular reactive oxygen species level, and cause DNA damage and caspase-mediated mitochondrial pathway apoptosis in NCI-H460 cells. In vivo, it can effectively inhibit tumor xenograft growth in nude mouse models with no body weight loss. In combination with the reported trans-bis(amidine)ruthenium(III) complexes, we found that ruthenium(III) bis(amidine) complexes could be cytotoxic in both trans and cis geometries, which is in contrast to platinum-based compounds.

A Pyrazolate Osmium(VI) Nitride Exhibits Anticancer Activity through Modulating Protein Homeostasis in HepG2 Cells

Interest in the third-row transition metal osmium and its compounds as potential anticancer agents has grown in recent years. Here, we synthesized the osmium(VI) nitrido complex Na[Os^VI(N)(tpm)₂] (tpm = [5-(Thien-2-yl)-1H-pyrazol-3-yl]methanol), which exhibited a greater inhibitory effect on the cell viabilities of the cervical, ovarian, and breast cancer cell lines compared with cisplatin. Proteomics analysis revealed that Na[Os^VI(N)(tpm)₂] modulates the expression of protein-transportation-associated, DNA-metabolism-associated, and oxidative-stress-associated proteins in HepG2 cells. Perturbation of protein expression activity by the complex in cancer cells affects the functions of the mitochondria, resulting in high levels of cellular oxidative stress and low rates of cell survival. Moreover, it caused G2/M phase cell cycle arrest and caspase-mediated apoptosis of HepG2 cells. This study reveals a new high-valent osmium complex as an anticancer agent candidate modulating protein homeostasis.

Osmium(VI) nitride triggers mitochondria-induced oncosis and apoptosis

We report a new osmium(VI) nitrido complex bearing a nonplanar tetradentate ligand with potent anticancer activity. This complex causes mitochondrial damage, which induces liver cancer cell death via oncosis and apoptosis. This is the first osmium-based anticancer candidate that induces oncosis.

High-Spin Iron(VI), Low-Spin Ruthenium(VI), and Magnetically Bistable Osmium(VI) in Molecular Group 8 Nitrido Trifluorides NMF3

Pseudo‐tetrahedral nitrido trifluorides N≡MF₃ (M=Fe, Ru, Os) and square pyramidal nitrido tetrafluorides N≡MF₄ (M=Ru, Os) were formed by free‐metal‐atom reactions with NF₃ and subsequently isolated in solid neon at 5 K. Their IR spectra were recorded and analyzed aided by quantum‐chemical calculations. For a d² electron configuration of the N≡MF₃ compounds in C_3v symmetry, Hund's rule predict a high‐spin ³A₂ ground state with two parallel spin electrons and two degenerate metal d(δ)‐orbitals. The corresponding high‐spin ³A₂ ground state was, however, only found for N≡FeF₃, the first experimentally verified neutral nitrido Fe^VI species. The valence‐isoelectronic N≡RuF₃ and N≡OsF₃ adopt different angular distorted singlet structures. For N≡RuF₃, the triplet ³A₂ state is only 5 kJ mol⁻¹ higher in energy than the singlet ¹A′ ground state, and the magnetically bistable molecular N≡OsF₃ with two distorted near degenerate ¹A′ and ³A“ electronic states were experimentally detected at 5 K in solid neon.