Evaluation of anticancer effects in vitro of new iridium(III) complexes targeting the mitochondria

Mitochondria Localized Anticancer Iridium(III) Prodrugs for Targeted Delivery of Myeloid Cell Leukemia-1 (Mcl-1) Inhibitors and Cytotoxic Iridium(III) Complex

Myeloid cell leukemia-1 (Mcl-1) is an antiapoptotic oncoprotein overexpressed in several malignancies and acts as one of the promising therapeutic targets for cancer. Even though there are several small molecule based Mcl-1 inhibitors reported, the delivery of Mcl-1 inhibitor at the target site is quite challenging. In this regard, we developed a series of mitochondria targeting luminescent cyclometalated iridium(III) prodrugs bearing Mcl-1 inhibitors via ester linkage due to the presence of Mcl-1 protein in the outer mitochondrial membrane. Among the synthesized prodrugs, IrThpy@L2 was found to exhibit the potent cytotoxicity (IC50 = 30.93 nM) against HCT116 cell line when compared with bare Mcl-1 inhibitors (IC50 > 100 μM). Mechanistic studies further revealed that IrThpy@L2 quickly gets internalized inside the mitochondria of HCT116 cells and undergoes activation in the presence of overexpressed esterase which leads to the release of two cytotoxic species i.e. Mcl-1 inhibitors (I-2) and cytotoxic iridium(III) complex (IrThpy@OH). The improved cytotoxicity of IrThpy@L2 is due to the mitochondria targeting ability of iridium(III) prodrug, subsequent esterase activated release of I-2 to inhibit Mcl-1 protein and IrThpy@OH to generate reactive oxygen species (ROS). After prodrug activation, the released cytotoxic species cause mitochondrial membrane depolarization, activate a cascade of mitochondria-mediated cell death events, and arrest the cell cycle in S-phase which leads to apoptosis. The potent anticancer activity of IrThpy@L2 was further evident from the drastic morphological changes, size reduction in the solid tumor mimicking 3D multicellular tumor spheroids (MCTS) of HCT116.

Mitochondria-Targeting Metallodrugs for Cancer Therapy: Perspectives from Cell Death Modes

Mitochondria, recognized as the cellular powerhouses, are indispensable organelles responsible for crucial cellular processes, such as energy metabolism, material synthesis, and signaling transduction. Their intricate involvement in a broad spectrum of diseases, particularly cancer, has propelled the exploration of mitochondria-targeting treatment as a promising strategy for cancer therapy. Since the groundbreaking discovery of cisplatin, the trajectory of research on the development of metal complexes have been marked by continuous advancement, giving rise to a diverse array of metallodrugs characterized by variations in ligand types, metal center properties, and oxidation states. By specifically targeting mitochondria, these metallodrugs exhibit the remarkable ability to elicit various programmed cell death pathways, encompassing apoptosis, autophagy, and ferroptosis. This review primarily focuses on recent developments in transition metal-based mitochondria-targeting agents, offering a comprehensive exploration of their capacity to induce distinct cell death modes. The aim is not only to disseminate knowledge but also to stimulate an active field of research toward new clinical applications and novel anticancer mechanisms.

Photoactivatable, mitochondria targeting dppz iridium(III) complex selectively interacts and damages mitochondrial DNA in cancer cells

Cyclometalated Ir(III) complex [Ir(L)2(dppz)]PF6 (where L = 1-methyl-2-(thiophen-2-yl)-1H-benzo[d]imidazole and dppz = dipyrido [3,2-a:2',3'-c]phenazine) (Ir1) is potent anticancer agent whose potency can be significantly increased by irradiation with blue light. Structural features of the cyclometalated Ir(III) complex Ir1 investigated in this work, particularly the presence of dppz ligand possessing an extended planar area, suggest that this complex could interact with DNA. Here, we have shown that Ir1 accumulates predominantly in mitochondria of cancer cells where effectively and selectively binds mitochondrial (mt)DNA. Additionally, the results demonstrated that Ir1 effectively suppresses transcription of mitochondria-encoded genes, especially after irradiation, which may further affect mitochondrial (and thus also cellular) functions. The observation that Ir1 binds selectively to mtDNA implies that the mechanism of its biological activity in cancer cells may also be connected with its interaction and damage to mtDNA. Further investigations revealed that Ir1 tightly binds DNA in a cell-free environment, with sequence preference for GC over AT base pairs. Although the dppz ligand itself or as a ligand in structurally similar DNA-intercalating Ru polypyridine complexes based on dppz ligand intercalates into DNA, the DNA binding mode of Ir1 comprises surprisingly a groove binding rather than an intercalation. Also interestingly, after irradiation with visible (blue) light, Ir1 was capable of cleaving DNA, likely due to the production of superoxide anion radical. The results of this study show that mtDNA damage by Ir1 plays a significant role in its mechanism of antitumor efficacy. In addition, the results of this work are consistent with the hypothesis and support the view that targeting the mitochondrial genome is an effective strategy for anticancer (photo)therapy and that the class of photoactivatable dipyridophenazine Ir(III) compounds may represent prospective substances suitable for further testing.

Designing a Mitochondria-Targeted Theranostic Cyclometalated Iridium(III) Complex: Overcoming Cisplatin Resistance and Inhibiting Tumor Metastasis through Necroptosis and Immune Response

To develop a potential theranostic metal agent to reverse the resistance of cancer cells to cisplatin and effectively inhibit tumor growth and metastasis, we proposed to design a cyclometalated iridium (Ir) complex based on the properties of the tumor environment (TME). To the end, we designed and synthesized a series of Ir(III) 2-hydroxy-1-naphthaldehyde thiosemicarbazone complexes by modifying the hydrogen atom(s) of the N-3 position of 2-hydroxy-1-naphthaldehyde thiosemicarbazone compounds and the structure of cyclometalated Ir(III) dimers and then investigated their structure-activity and structure-fluorescence relationships to obtain an Ir(III) complex (Ir5) with remarkable fluorescence and cytotoxicity to cancer cells. Ir5 not only possesses mitochondria-targeted properties but also overcomes cisplatin resistance and effectively inhibits tumor growth and metastasis in vivo. Besides, we confirmed the anticancer mechanisms of Ir5 acting on different components in the TME: directly killing liver cancer cells by inducing necroptosis and activating the necroptosis-related immune response.

Synthesis, characterization, molecular docking, RNA-sequence and anticancer efficacy evaluation in vitro of ruthenium(II) complexes on B16 cells

In recent years, the studies of the ruthenium(II) complexes on anticancer activity have been paid great attention, many Ru(II) complexes possess high anticancer efficiency. In this paper, three ligands CPIP (2-(4-chlorophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline), DCPIP (2-(3,4-dichlorophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline), TCPIP (2-(2,3,5-trichlorophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline) and their three ruthenium (II) complexes [Ru(dip)2(CPIP)](PF6)2 (1, dip = 4,7-diphenyl-1,10-phenanthroline), [Ru(dip)2(DCPIP)](PF6)2 (2) and [Ru(dip)2(TCPIP)](PF6)2 (3) were synthesized and characterized. 3-(4,5-dimethylthiazole-2-yl)-2,5-biphenyl tetrazolium bromide (MTT) assay was used to investigate in vitro cytotoxicity of complexes against various cancer cells. The results showed that complexes 1-3 exhibited pronounced cytotoxic effect on B16 cells with low IC50 values of 7.2 ± 0.1, 11.7 ± 0.6 and 1.2 ± 0.2 μM, respectively. The 3D model demonstrated that the complexes can validly prevent the cell proliferation. Apoptosis determined using Annexin V-FITC/PI double staining revealed that complexes 1-3 can effectively induce apoptosis in B16 cells. The intracellular localization of 1-3 in the mitochondria, the levels of intracellular reactive oxygen species (ROS), the opening of mitochondrial permeability transition pore as well as the decline of mitochondrial membrane potential were investigated, which demonstrated that the complexes 1-3 led to apoptosis via a ROS-mediated mitochondrial dysfunction pathway. The RNA-sequence indicated that the complexes upregulate the expression of 74 genes and downregulate the expression of 81 genes. The molecular docking showed that the complexes interact with the proteins through hydrogen bond, π-cation and π-π interaction. The results show that ruthenium(II) complexes 1, 2 and 3 can block tumor cell growth and induce cell death through autophagy and ROS-mediated mitochondrial dysfunction pathways.

Synthesis, characterization, anticancer efficacy evaluation of ruthenium(II) and iridium(III) polypyridyl complexes toward A549 cells

A new ligand DFIP (2-(dibenzo[b,d]furan-3-yl)-1H-imidazo[4,5-f][1,10]phenanthroline) and its two complexes iridium(III) [Ir(ppy)₂(DFIP)](PF₆) (ppy = 2-phenylpyridine, Ir1) and ruthenium(II) [Ru(bpy)₂(DFIP)](PF₆)₂ (bpy = 2,2'-bipyridine, Ru1) were synthesized and characterized. The anticancer effects of the two complexes on A549, BEL-7402, HepG2, SGC-7901, HCT116 and normal LO2 cells were tested by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method. Complex Ir1 shows high cytotoxic activity on A549, BEL-7402, SGC-7901 and HepG2, Ru1 exhibits moderate anticancer activity toward A549, BEL-7402 and SGC-7901 cells. The IC₅₀ values of Ir1 and Ru1 toward A549 are 7.2 ± 0.1 and 22.6 ± 1.4 μM, respectively. The localization of complexes Ir1 and Ru1 in the mitochondrial, intracellular accumulation of reactive oxygen species (ROS) levels, and the changes of mitochondrial membrane potential (MMP) and cytochrome c (cyto-c) were investigated. Apoptosis and cell cycle were detected by flow cytometry. Immunogenic cell death (ICD) was used to detect the effects of Ir1 and Ru1 on the A549 using a confocal laser scanning microscope. The expression of apoptosis-related proteins was detected by western blotting. Ir1 and Ru1 can increase the intracellular ROS levels and release cyto-c, reduce the MMP, leading to the apoptosis of A549 cells and blocking the A549 cells at the G0/G1 phase. Additionally, the complexes caused a decrease of the expression of polyADP-ribose polymerase (PARP), caspase 3, Bcl-2 (B-cell lymphoma-2), PI3K (phosphoinositide-3 kinase) and upregulated the expression of Bax. All these findings indicated that the complexes exert anticancer efficacy to induce cell death through immunogenic cell death, apoptosis, and autophagy.

Evaluation of the Anticancer Activity and Mechanism Studies of Glycyrrhetic Acid Derivatives toward HeLa Cells

In this paper, a series of glycyrrhetic acid derivatives 3a–3f were synthesized via the esterification reaction. The cytotoxicity of these compounds against five tumor cells (SGC-7901, BEL-7402, A549, HeLa and B16) and normal LO2 cells was investigated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method. The results showed that compound 3a exhibited high antiproliferative activity against HeLa cells (IC50 = 11.4 ± 0.2 μM). The anticancer activity was studied through apoptosis, cloning, and scratching; the levels of the intracellular ROS, GSH, and Ca2+; and the change in the mitochondrial membrane potential, cell cycle arrest and RNA sequencing. Furthermore, the effects of compound 3a on gene expression levels and metabolic pathways in HeLa cells were investigated via transcriptomics. The experimental results showed that this compound can block the cell cycle in the S phase and inhibit cell migration by downregulating Focal adhesion kinase (FAK) expression. Moreover, the compound can reduce the intracellular glutathione (GSH) content, increase the Ca2+ level and the intracellular ROS content, and induce a decrease in the mitochondrial membrane potential, further leading to cell death. In addition, it was also found that the mechanism of compounds inducing apoptosis was related to the regulation of the expression of mitochondria-related proteins B-cell lymphoma-2 (Bcl-2), Bcl-2-Associated X (Bax), and the activation of the caspase proteins. Taken together, this work provides a help for the development of glycyrrhetinic acid compounds as potential anticancer molecules.

Metal Complexes as Promising Matrix Metalloproteinases Regulators

Nowadays, cancers and dementia, such as Alzheimer's disease, are the most fatal causes of death. Many studies tried to understand the pathogenesis of those diseases clearly and develop a promising way to treat the diseases. Matrix metalloproteinases (MMPs) have been reported to be involved in the pathology of cancers and AD through tumor cell movement and amyloid degradation. Therefore, control of the levels and actions of MMPs, especially MMP-2 and MMP-9, is necessary to care for and/or cure cancer and AD. Various molecules have been examined for their potential application as regulators of MMPs expression and activity. Among the molecules, multiple metal complexes have shown advantages, including simple synthesis, less toxicity and specificity toward MMPs in cancer cells or in the brain. In this review, we summarize the recent studies and knowledge of metal complexes (e.g., Pt-, Ru-, Au-, Fe-, Cu-, Ni-, Zn-, and Sn-complexes) targeting MMPs and their potentials for treating and/or caring the most fatal human diseases, cancers and AD.

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.

Light activation of iridium(III) complexes driving ROS production and DNA damage enhances anticancer activity in A549 cells

The work aimed to synthesize and characterize two iridium(III) complexes [Ir(ppy)₂(IPPH)](PF₆) (Ir1, IPPH = (2S,3R,5S,6R)-2-(2-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)phenoxy)-6-(hydroxymethyl)tetrahydro-2H-pyran-3,4,5-triol, ppy = 2-phenylpyridine), [Ir(piq)₂(IPPH)](PF₆) (Ir2, piq = 1-phenylisoquinoline). The cytotoxicity of the complexes against BEL-7402, A549, HCT-116, B16 cancer cells and normal LO2 was evaluated through 3-(4,5-dimethylthiazole-2-yl)-2,5-biphenyl tetrazolium bromide (MTT) method. The complexes show no cytotoxic activity (IC₅₀ > 100 μM) against these cancer cells, while their cytotoxicity can significantly be elevated upon illumination. The IC₅₀ values range from 0.2 ± 0.05 to 35.5 ± 3.5 μM. The cellular uptake, endoplasmic reticulum and mitochondria localization, reactive oxygen species, the change of mitochondrial membrane potential, γ-H2AX levels, cycle arrest, apoptosis and the expression of B-cell lymphoma-2 were investigated. The calreticulin (CRT), heat shock protein 70 (HSP70), high mobility group box 1 (HMGB1) were explored. This study demonstrates that photoactivatable complexes induce cell death in A549 through ROS-mediated endoplasmic reticulum stress-mitochondrial pathway, DNA damage pathways, immunogenic cell death (ICD), activation of PI3K/AKT signaling pathway and inhibit the cell growth at S phase.

Induction of apoptosis in SGC-7901 cells by iridium(III) complexes via endoplasmic reticulum stress-mitochondrial dysfunction pathway

This study was intended to evaluate the anticancer activity of three newly synthesized iridium(III) complexes [Ir(ppy)₂(PEIP)](PF₆) (1) (ppy = 2-phenylpyridine, PEIP = 2-phenethyl-1H-imidazo[4,5-f][1,10]phenanthroline), [Ir(ppy)₂(SIP)](PF₆) (2) (SIP = (E)-2-styryl-1H-imidazo[4,5-f][1,10]phenanthroline) and [Ir(ppy)₂(PEYIP)](PF₆) (3) (PEYIP = 2-phenethynyl-1H-imidazo[4,5-f][1,10]phenanthroline). The cytotoxic activity in vitro against A549, SGC-7901, HepG2, HeLa and normal NIH3T3 cells was investigated by 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) method. We found that the complexes 1, 2 and 3 significantly inhibited cell proliferation, in particular, complexes 2 and 3 show high cytotoxic effect on SGC-7901 cells with an IC₅₀ value of 5.8 ± 0.7 and 4.4 ± 0.1 μM. Moreover, cell cycle assay revealed that the complexes could block G2/M phase of the cell cycle. Apoptotic evaluation by Annexin V/PI staining indicated that complexes 1-3 can induce apoptosis in SGC-7901 cells. In addition, microscopy detection suggested that disruption of mitochondrial functions, characterized by increased generation of intracellular ROS and Ca²⁺ as well as decrease of mitochondrial membrane potential. Western blot analysis shows that the complexes upregulate the expression of pro-apoptotic Bax and downregulate the expression of anti-apoptotic Bcl-2, which further activates caspase-3 and prompts the cleavage of PARP. Taken together, these results demonstrated that complexes 1-3 exert a potent anticancer effect on SGC-7901 cells via ROS-mediated endoplasmic reticulum stress-mitochondrial apoptotic pathway and have a potential to be developed as novel chemotherapeutic agents for human gastric cancer. Three new iridium(III) complexes [Ir(ppy)₂(PEIP)](PF₆) (1) (ppy = 2-phenylpyridine, PEIP = 2-phenethyl-1H-imidazo[4,5-f][1,10]phenanthroline), [Ir(ppy)₂(SIP)](PF₆) (2) (SIP = 2-styryl-1H-imidazo[4,5-f][1,10]phenanthroline) and [Ir(ppy)₂(PEYIP)](PF₆) (3) (PEYIP = 2-phenethynyl-1H-imidazo[4,5-f][1,10]phenanthroline) were synthesized and characterized. The anticancer activity in vitro was investigated by 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) method. The results show that the complexes induce apoptosis via ROS-mediated endoplasmic reticulum stress-mitochondrial dysfunction pathway.

Metal Complexes in Target-Specific Anticancer Therapy: Recent Trends and Challenges

Cancer is characterized by abnormal cell differentiation in or on the part of the body. The most commonly used chemotherapeutic drugs are developed to target rapidly dividing cells, such as cancer cells, but they also damage healthy epithelial cells. This has serious consequences for normal cells and become responsible for the development of various disorders. Several strategies for delivering the cytotoxic drugs to cancerous sites that limit systemic toxicity and other adverse effects have recently been evolved. Among them, biomolecule-conjugated metal complexes-based cancer targeting strategies have shown tremendous advantages in cancer therapy. This review focuses on several chemoselective biomolecules-bound metal complexes as prospective cancer therapy-targeted agents. In this review, we presented the details of the various extra- and intracellular targeting mechanisms in cancer therapy. We also addressed the current clinical issues and recent therapeutic strategies in targeted cancer therapy that may pave a way for the future direction of metal complexes-based targeted cancer therapy.

Iridium(III) complexes entrapped in liposomes trigger mitochondria-mediated apoptosis and GSDME-mediated pyroptosis

In this report, a new ligand TFBIP (TFBIP = 2-(4'-trifluoromethyl)-[1,1'-biphenyl]-4-yl)-1H-imidazo[4,5-f][1,10]phenanthroline) and its three iridium (III) complexes [Ir(ppy)₂(TFBIP)](PF₆) (Ir1, ppy = 2-phenylpyridine), [Ir(bzq)₂(TFBIP)](PF₆) (Ir2, bzq = benzo[h]quinolone) and [Ir(piq)₂(TFBIP)](PF₆) (Ir3, piq = 1-phenylisoquinoline) were synthesized and characterized. The cytotoxicity in vitro of the complexes toward several cancer cells was evaluated by 3-(4,5-dimethylthiazole-2-yl)-2,5-biphenyl tetrazolium bromide (MTT) methods. The complexes show no cytotoxicity (IC₅₀ > 100 μM) against these cancer cells. To enhance anticancer activity, these complexes were trapped in liposomes to form Ir1Lipo, Ir2Lipo and Ir3Lipo. The liposomes Ir1Lipo, Ir2Lipo and Ir3Lipo exhibit high or moderate cytotoxic activity. In particular, Ir1Lipo can effectively inhibit the cell growth with a low IC₅₀ value (< 10 μM) toward A549, HepG2, BEL-7402, B16, HeLa and SGC-7901 cells. Surprisingly, Ir1Lipo has no cytotoxic activity against the normal cell LO2 (IC₅₀ > 100 μM). The apoptosis and pyroptosis were investigated. Ir3Lipo induces apoptosis with a high early apoptotic number of 37%. The reactive oxygen species (ROS) levels, mitochondrial permeability transition pore open and mitochondrial membrane potential were detected. The intracellular Ca²⁺ concentration and release of cytochrome c were investigated. The expression of Bcl-2 (B-cell lymphoma-2) family proteins was explored by western blot. The antitumor activity in vivo of Ir1Lipo was evaluated with an inhibitory rate of 53%.

In vitro and In silico anticancer activities of Mn(ii), Co(ii), and Ni(ii) complexes: synthesis, characterization, crystal structures, and DFT studies

Complexes 1, 2 and 3 showed significant activity against K562, MCF-7, and DL cancer cell lines. Complexes 1–3 showed higher growth inhibition than metal salts or ligands in tumour cell growth and colony formation. Complex 1 exhibited higher anticancer activity than cisplatin.

Increasing anticancer effect in vitro and vivo of liposome-encapsulated iridium(III) complexes on BEL-7402 cells

The studies of iridium (III) complexes as potent anticancer reagents have attracted great attention. Here, a new iridium (III) complex [Ir(bzq)₂(PYIP)](PF₆) (Ir1, bzq = benzo[h]quinoline, PYIP = 2-(pyren-1-yl)-1H-imidazo[4,5-f][1,10]phenanthroline) was synthesized and its liposomes (Ir1Lipo) was prepared. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method was used to detect the cytotoxic activity of Ir1 and Ir1Lipo on HepG2, SGC-7901, BEL-7402, HeLa, B16, A549 and normal NIH3T3 cells. The complex Ir1 displays no obvious inhibitory effect on the growth of BEL-7402 cells, while the Ir1Lipo shows significant cytotoxic activity on BEL-7402 cells (IC₅₀ = 2.6 ± 0.03 μM). In further studies, Ir1Lipo induced apoptosis by the mitochondrial pathways, such as increasing intracellular reactive oxygen species (ROS) content and intracellular Ca²⁺ level, decreasing the mitochondrial membrane potential (MMP). In addition, after incubation with Ir1Lipo, the colony formation of BEL-7402 cells was significantly inhibited. Moreover, flow cytometry was used to detect the impact of Ir1Lipo on cell cycle distribution, and western blot was used to detect the expression of caspases and Bcl-2 (B-cell lymphoma-2) family proteins. Furthermore, Ir1Lipo exhibited significant antitumor activity in vivo with an inhibitory rate of 65.8%. These results indicated that Ir1Lipo induces apoptosis in BEL-7402 cells through intrinsic mitochondrial pathway.

Antitumor activity studies of iridium (III) polypyridine complexes-loaded liposomes against gastric tumor cell in vitro

Two iridium (III) polypyridine complexes [Ir(ppy)₂(BIP)]PF₆ (ppy = 2-phenylpyridine, BIP = 2-biphenyl-1H-imidazo[4,5-f][1,10]phenanthroline, Ir1), [Ir(piq)₂(BIP)]PF₆ (piq = 1-phenylisoquinoline, Ir2) and their liposomes Ir1lipo and Ir2lipo were synthesized and characterized. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to evaluate cytotoxic activity against several cancer cells (A549, HepG2, SGC-7901, Bel-7402, HeLa) and non-cancer cell (mouse embryonic fibroblast, NIH3T3). The results showed that Ir1lipo displays the high cytotoxicity toward SGC-7901 with IC₅₀ value of 5.8 ± 0.2 μM, while the complexes have no cytotoxicity toward A549, HepG2, Bel-7402 and HeLa cells. The cell colony demonstrated that the iridium (III) complexes-loaded liposomes can inhibit cell proliferation, induce cell cycle arrest at G0/G1 phase. Moreover, they also cause autophagy, induce a decrease of mitochondrial membrane potential and increase intracellular reactive oxygen species (ROS) content. These results suggest that the complexes encapsulated liposomes Ir1lipo and Ir2lipo inhibit the growth of SGC-7901 cells through a ROS-mediated mitochondrial dysfunction and activating the PI3K (phosphoinositide-3 kinase)/ AKT (protein kinase B) signaling pathways.

Synthesis and evaluation of iridium(III) complexes on antineoplastic activity against human gastric carcinoma SGC-7901 cells

The study was intended to determine the antineoplastic effects of two new iridium(III) complexes [Ir(ppy)2(PTTP)](PF6) (1) (ppy = 2-phenylpyridine) and [Ir(piq)2(PTTP)](PF6) (2) (piq = 1-phenylisoquinoline, PTTP = 2-phenoxy-1,4,8,9-tetraazatriphenylene). In MTT assay, the ligand PTTP displayed ineffective inhibition on cell growth in SGC-7901, BEL-7402, HepG2 as well as NIH3T3 cell lines, while complexes 1 and 2 showed high cytotoxic activity on SGC-7901 cells with an IC50 value of 0.5 ± 0.1 µM and 4.4 ± 0.6 µM, respectively. Cellular uptake, cell cloning experiments, wound healing assay and cell cycle arrest indicated that the two complexes can inhibit the cell proliferation in SGC-7901 and induce cell cycle arrest at G0/G1 phase. Additionally, reactive oxygen species (ROS) and mitochondrial membrane potential suggested that the two complexes induced cell apoptosis through disrupting mitochondrial functions. Further, western blot analysis illustrated that the two complexes caused apoptosis via regulating expression levels of Bcl-2 family proteins. Moreover, complex 1 could suppress tumor growth in vivo with an inhibitory rate of 49.41%. Altogether, these results demonstrated that complexes 1 and 2 exert a potent anticancer effect against SGC-7901 cells via mitochondrial apoptotic pathway and have a potential to be developed as antineoplastic drug candidates for human gastric cancer.

Anticancer effect evaluation in vitro and in vivo of iridium(III) polypyridyl complexes targeting DNA and mitochondria

To investigate the antitumor effect of iridium complexes, three iridium (III) complexes [Ir(ppy)₂(dcdppz)]PF₆ (ppy = 2-phenylpyridine, dcdppz = 11,12-dichlorodipyrido[3,2-a:2',3'-c]phenazine) (Ir1), [Ir(bzq)₂(dcdppz)]PF₆ (bzq = benzo[h]quinoline) (Ir2) and [Ir(piq)₂(dcdppz)]PF₆ (piq = 1-phenylisoquinoline) (Ir3) were synthesized and characterized. Geometry optimization, molecular dynamics simulation and docking studies have been performed to further explore the antitumor mechanism. The cytotoxicity of Ir1-3 toward cancer cells was studied by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method. The localization of complexes Ir1-3 in the mitochondria, intracellular accumulation of reactive oxygen species (ROS) levels, the changes of mitochondrial membrane potential and morphological changes in apoptosis were investigated. Flow cytometry was applied to quantify fluorescence intensity and determine cell cycle distribution. Western blotting was used to detect the expression of apoptosis-related proteins. The anti-tumor effect of Ir1 in vivo was evaluated. The results showed that Ir1-3 had high cytotoxicity to most tumor cells, especially to SGC-7901 cells with a low IC₅₀ value. Ir1-3 can increase the intracellular ROS levels, reduce the mitochondrial membrane potential. Additionally, the complexes induce an increase of apoptosis-related protein expression, enhance the percentage of apoptosis. The complexes inhibit the cell proliferation at G0/G1 phase. The results obtained from antitumor in vivo indicate that Ir1 can significantly inhibit the growth of tumors with an inhibitory rate of 54.08%. The docking studies show that complexes Ir1-3 interact with DNA through minor-groove intercalation, which increases the distance of DNA base pairs, leading to a change of DNA helix structure. These experimental and theoretical findings indicate that complexes Ir1-3 can induce apoptosis in SGC-7901 cells through the mitochondrial dysfunction and DNA damage pathways, and then exerting anti-tumor activity in vitro and vivo.