Iridium (III) complexes induce cervical carcinoma apoptosis via disturbing cellular redox homeostasis disorder and inhibiting PI3K/AKT/mTOR pathway

Covalent inhibition of epidermal growth factor receptor using a long-lived iridium(III)-afatinib probe

The overexpression and overactivation of epidermal growth factor receptor (EGFR) are frequently observed in human cancers, including squamous cell carcinoma and adenocarcinoma. In this study, a covalent EGFR probe was developed by conjugating afatinib to an iridium(III) scaffold. Complex 1 showed enhanced luminescence in living epidermoid squamous carcinoma A431 cells compared to other cell lines, via engaging EGFR as confirmed via CETSA and knockdown experiments. Moreover, complex 1 inhibited downstream targets of EGFR in cellulo with repression persisting after removal of the complex, indicating an irreversible mode of inhibition. Finally, complex 1 showed potent antiproliferative activity against A431 cells with comparable potency to afatinib alone. To our knowledge, complex 1 is the first EGFR covalent inhibitor based on an iridium scaffold reported in the literature, with the potential to be further explored as a theranostic agent in the future.

Recent Advancement in the Synthesis of Ir-Based Complexes

Cancer is a devastating disease with over 100 types, including lung and breast cancer. Cisplatin and metal-based drugs are limited due to their drug resistance and side effects. Iridium-based compounds have emerged as promising candidates due to their unique chemical properties and resemblance to platinum compounds. The objective of this study is to investigate the synthesis and categorization of iridium complexes, with a particular emphasis on their potential use as anticancer agents. The major focus of this research is to examine the synthesis of these complexes and their relevance to the field of cancer treatment. The negligible side effects and flexibility of cyclometalated iridium(III) complexes have garnered significant interest. Organometallic half-sandwich Ir(III) complexes have notable benefits in cancer research and treatment. The review places significant emphasis on categorizing iridium complexes according to their ligand environment, afterward considering the ligand density and coordination number. This study primarily focuses on several methods for synthesizing cyclometalated and half-sandwich Ir complexes, divided into subgroups based on ligand denticity. The coordination number of iridium complexes determines the number of ligands coordinated to the central iridium atom, which impacts their stability and reactivity. Understanding these complexes is crucial for designing compounds with desired properties and investigating their potential as anticancer agents. Cyclometalated iridium(III) complexes, which contain a meta-cycle with the E-M-C order σ bond, were synthesized in 1999. These complexes have high quantum yields, significant stock shifts, luminescence qualities, cell permeability, and strong photostability. They have been promising in biosensing, bioimaging, and phosphorescence of heavy metal complexes.

Design, synthesis and biological evaluation of liposome entrapped iridium(III) complexes toward SGC-7901 cells

In this study, two new iridium(III) polypyridyl complexes [Ir(bzq)₂(DIPH)](PF₆) (bzq = deprotonated benzo[h]quinoline, DIPH = 4-(2,5-dibromo-4-(1H-imidazo[4,5-f][1,10]phenanthrolim-2-yl)-4-hydroxybutan-2-one) (Ir1) and [Ir(piq)₂(DIPH)](PF₆) (piq = deprotonated 1-phenylisoquinoline) (Ir2) were synthesized and characterized by elemental analysis, HRMS, ¹H and ¹³C NMR. The cytotoxic activity of Ir1, Ir2, Ir1lipo and Ir2lipo against cancer cells SGC-7901, HepG2, A549, HeLa, B16 and normal NIH3T3 cells in vitro was evaluated using 3-(4,5-dimethylthiazole-2-yl)-2,5-biphenyl tetrazolium bromide (MTT) method. Ir1 and Ir2 showed no cytotoxic activity, but their liposome-entrapped Ir1 (Ir1lipo) and Ir2 (Ir2lipo) showed significant cellular activity, especially sensitive to SGC-7901 with IC₅₀ values of 4.7 ± 0.2 and 12.4 ± 0.5 μM, respectively. The cellular uptake, endoplasmic reticulum (ER) localization, autophagy, tubulin polymerization, glutathione (GSH), malondialdehyde (MDA) and release of cytochrome c were investigated to explore the mechanisms of apoptosis. The calreticulin (CRT), heat shock protein 70 (HSP70), high mobility group box 1 (HMGB1) were also explored. Western blotting showed that Ir1lipo and Ir2lipo inhibited PI3K (phosphoinositide-3 kinase), AKT (protein kinase B), p-AKT and activated Bcl-2 (B-cell lymphoma-2) protein and apoptosis-regulated factor caspase 3 (cysteinyl aspartate specific proteinase-3) and cleaving PARP (poly ADP-ribose polymerase). The results demonstrated that Ir1lipo and Ir2lipo induce cell apoptosis through targeting the endoplasmic reticulum (ER), cause oxidative stress damage, inhibiting PI3K/AKT signaling pathway, immunogenic cell death (ICD) and inhibit the cell growth at G2/M phase.

Iridium(III) complexes inhibit the proliferation and migration of BEL-7402 cells through the PI3K/AKT/mTOR signaling pathway

Iridium(III) complexes are largely studied as anti-cancer complexes due to their excellent anti-cancer activity. In this article, two new iridium(III) complexes [Ir(piq)₂(THPIP)]PF₆ (THPIP = 2,4-di-tert-butyl-6-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)phenol, piq = deprotonated 1-phenylisoquinoline) (Ir1) and [Ir(bzq)₂(THPIP)]PF₆ (bzq = deprotonated benzo[h]quinolone) (Ir2) were synthesized. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays showed that complex Ir1 exhibits moderate activity (IC₅₀ = 29.9 ± 4.6 μM) and Ir2 shows high cytotoxicity (IC₅₀ = 9.8 ± 1.8 μM) against BEL-7402 cells. Further studies on the mechanism showed that Ir1 and Ir2 induced apoptosis by changing the mitochondrial membrane potential, Ca²⁺ release, ROS accumulation, and cell cycle arrest at the S phase. The complexes can effectively inhibit cell colony formation and migration. The expression of B-cell lymphoma-2 (Bcl-2) family proteins, PI3K (phosphatidylinositol 3-kinase), AKT (protein kinase B), mTOR (mammalian target of rapamycin), and p-mTOR was studied by immunoblotting. Complexes Ir1 and Ir2 downregulated the expression of anti-apoptotic protein Bcl-2 and increased the expression of autophagy-related proteins of Beclin-1 and LC3-II. Further experiments showed that the complexes inhibited the production of glutathione (GSH) and increased the amounts of malondialdehyde (MDA). Fluorescence of HMGB1 was significantly increased. We also investigated the effect of the complexes on the expression of genes using RNA-sequence analysis, we further calculated the lowest binding energies between the complexes and proteins using molecular docking. Taken together, the above results indicated that complexes Ir1 and Ir2 induce apoptosis in BEL-7402 cells through a ROS-mediated mitochondrial dysfunction and inhibition of the PI3K/AKT/mTOR signaling pathway.

Anticancer effect evaluation of iridium(III) complexes targeting mitochondria and endoplasmic reticulum

Ligand HMSPIP (2-(4-(methylsulfonyl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline) and its iridium(III) complexes [Ir(ppy)₂(HMSPIP)]PF₆ (ppy = 2-phenylpyridine, Ir1) and [Ir(bzq)₂(HMSPIP)]PF₆ (bzq = benzo[h]quinoline, Ir2) were synthesized. The complexes were characterized by ¹H NMR, ¹³C NMR, and UV/Vis spectra. The cytotoxicity of the complexes toward cancer cells were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method, the scratch wound healing and colony-forming were also investigated. MTT assay certificated that the complexes show high toxic effect on the HeLa cells. The cell cycle assay illustrated that the complexes blocked cell growth at G₀/G₁ phase in HeLa cells. A series of subsequent experiments showed that the complexes first enter the endoplasmic reticulum (ER) and then enter the mitochondria, leading to an increase in intracellular Ca²⁺ and reactive oxygen species (ROS) content, depolarizing mitochondrial membrane potential (MMP), and ultimately resulting in apoptosis. In addition, the experimental results revealed that the complexes not only increase the level of ROS but also inhibit the production of GSH and eventually produce large amounts of MDA and further leading to cell death. Taken together, we consider that the complexes can be used as potential candidate drugs for HeLa cancer treatment.

Current status of iridium-based complexes against lung cancer

Lung cancer is one of the most common malignant tumors, with the highest mortality rate in the world, and its incidence is second only to breast cancer. It has posed a serious threat to human health. Cisplatin, a metal-based drug, is one of the most widely used chemotherapeutic agents for the treatment of various cancers. However, its clinical efficacy is seriously limited by numerous side effects and drug resistance. This has led to the exploration and development of other transition metal complexes for the treatment of malignant tumors. In recent years, iridium-based complexes have attracted extensive attention due to their potent anticancer activities, limited side effects, unique antitumor mechanisms, and rich optical properties, and are expected to be potential antitumor drugs. In this review, we summarize the recent progress of iridium complexes against lung cancer and introduce their anti-tumor mechanisms, including apoptosis, cycle arrest, inhibition of lung cancer cell migration, induction of immunogenic cell death, etc.