An Iridium(III) Complex Inhibits JMJD2 Activities and Acts as a Potential Epigenetic Modulator

Iridium(III) complexes as novel theranostic small molecules for medical diagnostics, precise imaging at a single cell level and targeted anticancer therapy

Medical applications of iridium (III) complexes include their use as state-of-the-art theranostic agents - molecules that combine therapeutic and diagnostic functions into a single entity. These complexes offer a promising avenue in medical diagnostics, precision imaging at single-cell resolution and targeted anticancer therapy due to their unique properties. In this review we report a short summary of their application in medical diagnostics, imaging at single-cell level and targeted anticancer therapy. The exceptional photophysical properties of Iridium (III) complexes, including their brightness and photostability, make them excellent candidates for bioimaging. They can be used to image cellular processes and the microenvironment within single cells with unprecedented clarity, aiding in the understanding of disease mechanisms at the molecular level. Moreover the iridium (III) complexes can be designed to selectively target cancer cells,. Upon targeting, these complexes can act as photosensitizers for photodynamic therapy (PDT), generating reactive oxygen species (ROS) upon light activation to induce cell death. The integration of diagnostic and therapeutic capabilities in Iridium (III) complexes offers the potential for a holistic approach to cancer treatment, enabling not only the precise eradication of cancer cells but also the real-time monitoring of treatment efficacy and disease progression. This aligns with the goals of personalized medicine, offering hope for more effective and less invasive cancer treatment strategies.

Lysosome-targeted cyclometalated iridium(III) complexes: JMJD inhibition, dual induction of apoptosis and autophagy

A series of cyclometalated iridium(III) complexes with the formula [Ir(C^N)2 L](PF6) (C^N = 2-phenylpyridine (ppy, in Ir-1), 2-(2-thienyl)pyridine (thpy, in Ir-2), 2-(2,4-difluorophenyl)pyridine (dfppy, in Ir-3), L = 2-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)quinolin-8-ol) were designed and synthesized, which utilize 8-hydroxyquinoline derivative as N^N ligands to chelate the cofactor Fe2+ of the Jumonji domain-containing protein (JMJD) histone demethylase. As expected, the results of UV/Vis titration analysis confirm the chelating capabilities of Ir-1-3 for Fe2+, and molecular docking studies also show that Ir-1-3 can interact with the active pocket of JMJD protein, and treatment of cells with Ir-1-3 results in significant upregulation of trimethylated histone 3 lysine 9 (H3K9Me3), indicating the inhibition of JMJD activity. Meanwhile, Ir-1-3 exhibit much higher cytotoxicity against the tested tumor cell lines compared with the clinical chemotherapeutic agent cisplatin. And Ir-1-3 can block the cell cycle at G2/M phase and inhibit cell migration and colony formation. Further studies show that Ir-1-3 can specifically accumulate in lysosomes, damage the integrity of lysosomes, and induce apoptosis and autophagy. Reduction of mitochondrial membrane potential (MMP) and elevation of reactive oxygen species (ROS) also contribute to the antitumor effects of Ir-1-3. Finally, Ir-1 can inhibit tumor growth effectively in vivo and increase the expression of H3K9Me3 in tumor tissues. Our study demonstrates that these iridium(III) complexes are promising anticancer agents with multiple functions, including the inhibition of JMJD and induction of apoptosis and autophagy.

8-Hydroxyquinoline-modified ruthenium(II) polypyridyl complexes for JMJD inhibition and photodynamic antitumor therapy

As an ideal scaffold for metal ion chelation, 8-hydroxyquinoline (8HQ) can chelate different metal ions, such as Fe²⁺, Cu²⁺, Zn²⁺, etc. Here, by integrating 8HQ with a ruthenium(II) polypyridyl moiety, two Ru(II)-8HQ complexes (Ru1 and Ru2), [Ru(N-N)₂L](PF₆)₂ (L = 2-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)quinolin-8-ol; N-N: 2,2'-bipyridine (bpy, in Ru1), 1,10-phenanthroline (phen, in Ru2)) were designed and synthesized. In both complexes, ligand L is an 8HQ derivative designed to chelate the cofactor Fe²⁺ of jumonji C domain-containing demethylase (JMJD). As expected, Ru1 and Ru2 could inhibit the activity of JMJD by chelating the key cofactor Fe²⁺ of JMJD, resulting in the upregulation of histone-methylation levels in human lung cancer (A549) cells, and the upregulation was more pronounced under light conditions. In addition, MTT data showed that Ru1 and Ru2 exhibited lower dark toxicity, and light irradiation could significantly enhance their antitumor activity. The marked photodynamic activities of Ru1 and Ru2 could induce the elevation of reactive oxygen species (ROS), depolarization of mitochondrial membrane potential (MMP), and activation of caspases. These mechanistic studies indicated that Ru1 and Ru2 could induce apoptosis through the combination of JMJD inhibitory and PDT activities, thereby achieving dual antitumor effects.

Histone Demethylase JMJD2D: A Novel Player in Colorectal and Hepatocellular Cancers

Simple Summary

Histone demethylase JMJD2D is a multifunctional epigenetic factor coordinating androgen receptor activation, DNA damage repair, DNA replication, cell cycle regulation, and inflammation modulation. JMJD2D is also a well-established epigenetic facilitator in the progression of multiple malignant tumors, especially in colorectal cancer (CRC) and hepatocellular cancer (HCC). This review aims to summarize the mechanisms of JMJD2D in promoting CRC and HCC progression, which provides novel ideas for targeting JMJD2D in oncotherapy. JMJD2D promotes gene transcription by reducing H3K9 methylation and serves as a coactivator to enhance the activities of multiple carcinogenic pathways, including Wnt/β-catenin, Hedgehog, HIF1, JAK-STAT3, and Notch signaling; or acts as an antagonist of the tumor suppressor p53.

Abstract

Posttranslational modifications (PTMs) of histones are well-established contributors in a variety of biological functions, especially tumorigenesis. Histone demethylase JMJD2D (also known as KDM4D), a member of the JMJD2 subfamily, promotes gene transcription by antagonizing H3K9 methylation. JMJD2D is an epigenetic factor coordinating androgen receptor activation, DNA damage repair, DNA replication, and cell cycle regulation. Recently, the oncogenic role of JMJD2D in colorectal cancer (CRC) and hepatocellular cancer (HCC) has been recognized. JMJD2D serves as a coactivator of β-catenin, Gli1/2, HIF1α, STAT3, IRF1, TCF4, and NICD or an antagonist of p53 to promote the progression of CRC and HCC. In this review, we summarize the molecular mechanisms of JMJD2D in promoting the progression of CRC and HCC as well as the constructive role of its targeting inhibitors in suppressing tumorigenesis and synergistically enhancing the efficacy of anti-PD-1/PD-L1 immunotherapy.

Novel heterobimetallic Ir(III)-Re(I) complexes: design, synthesis and antitumor mechanism investigation

The reasonable design of binuclear or multinuclear metal complexes has demonstrated their potential advantages in the anticancer field. Herein, three heterobimetallic Ir(III)-Re(I) complexes, [Ir(C^N)₂LRe(CO)₃DIP](PF₆)₂ (C^N = 2-phenylpyridine (ppy, in IrRe-1), 2-(2-thienyl)pyridine (thpy, in IrRe-2) and 2-(2,4-difluorophenyl)pyridine (dfppy, in IrRe-3); L = pyridylimidazo[4,5-f][1,10]phenanthroline; DIP = 4,7-diphenyl-1,10-phenanthroline), were designed and synthesized. The heterobimetallic IrRe-1-3 complexes show pH-sensitive emission properties, which can be used for specific imaging of lysosomes. Additionally, IrRe-1-3 display higher cytotoxicity against tested tumor cell lines than the clinical chemotherapeutic drug cisplatin. Further mechanisms indicate that IrRe-1-3 can induce apoptosis and autophagy, increase intracellular reactive oxygen species (ROS), depolarize the mitochondrial membrane (MMP), block the cell cycle at the G0/G1 phase and inhibit cell migration. To the best of our knowledge, this is the first example of the synthesis of heterobimetallic Ir(III)-Re(I) complexes with superior anticancer activities and evaluation of their anticancer mechanisms.

Accumulation of mono-reduced [Ir(piq)2(LL)] photosensitizers relevant for solar fuels production

A series of nine [Ir(piq)₂(LL)]⁺.PF₆^- photosensitizers, where piqH = 1-phenylisoquinoline, was developed and investigated for excited-state electron transfer with sacrificial electron donors that included triethanolamine (TEOA), triethylamine (TEA) and 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole (BIH) in acetonitrile. The photosensitizers were obtained in 57-82% yield starting from the common [Ir(piq)₂µ-Cl]₂ precursor and were all characterized by UV-Vis absorption as well as by steady-state, time-resolved spectroscopies and electrochemistry. The excited-state lifetimes ranged from 250 to 3350 ns and excited-state electron transfer quenching rate constants in the 10⁹ M^-1 s^-1 range were obtained when BIH was used as electron donor. These quenching rate constants were three orders of magnitude higher than when TEA or TEOA was used. Steady-state photolysis in the presence of BIH showed that the stable and reversible accumulation of mono-reduced photosensitizers was possible, highlighting the potential use of these Ir-based photosensitizers in photocatalytic reactions relevant for solar fuels production.

In vitro studies on the selective cytotoxic effect of luminescent Ru(ii)-p-cymene complexes of imidazo-pyridine and imidazo quinoline ligands

In recent years, Ru(ii) complexes have gained high importance in medicinal chemistry due to their significant anti-cancer activities, which are directly related to their DNA binding ability.

Epigenetic Modulators as Treatment Alternative to Diverse Types of Cancer

DNA is packaged in rolls in an octamer of histones forming a complex of DNA and proteins called chromatin. Chromatin as a structural matrix of a chromosome and its modifications are nowadays considered relevant aspects for regulating gene expression, which has become of high interest in understanding genetic mechanisms regulating various diseases, including cancer. In various types of cancer, the main modifications are found to be DNA methylation in the CpG dinucleotide as a silencing mechanism in transcription, post-translational histone modifications such as acetylation, methylation and others that affect the chromatin structure, the ATP-dependent chromatin remodeling and miRNA-mediated gene silencing. In this review we analyze the main alterations in gene expression, the epigenetic modification patterns that cancer cells present, as well as the main modulators and inhibitors of each epigenetic mechanism and the molecular evolution of the most representative inhibitors, which have opened a promising future in the study of HAT, HDAC, non-glycoside DNMT inhibitors and domain inhibitors.

Discovery of a potent and selective inhibitor of histone lysine demethylase KDM4D

Histone lysine demethylase 4D (KDM4D) plays an important role in the regulation of tumorigenesis, progression and drug resistance and has been considered a potential target for cancer treatment. However, there is still a lack of potent and selective KDM4D inhibitors. In this investigation, we report a new class of KDM4D inhibitors containing the 2-(aryl(pyrrolidine-1-yl)methyl)phenol scaffold, identified through AlphaLisa-based screening, structural optimization, and structure-activity relationship analyses. Among these inhibitors, 24s was the most potent, with an IC₅₀ value of 0.023 ± 0.004 μM. This compound exhibited more than 1500-fold selectivity towards KDM4D versus KDM4A as well as other JMJD subfamily members, indicating good selectivity for KDM4D. Kinetic analysis indicated that 24s did not occupy the 2-oxoglutarate binding pocket. In an in vitro assay, 24s significantly suppressed the proliferation and migration of colorectal cancer (CRC) cells. Overall, this study has identified a good tool compound to explore the biological function of KDM4D and a good lead compound for drug discovery targeting KDM4D.

Unravelling KDM4 histone demethylase inhibitors for cancer therapy

Epigenetic enzyme-targeted therapy is a promising new development in the field of drug discovery. To date, histone deacetylases and DNA methyltransferases have been investigated as druggable epigenetic enzyme targets in cancer therapeutics. Histone methyltransferases and lysine demethylase inhibitors are the latest groups of epi-drugs being actively studied in clinical trials. KDM4s are JmjC domain-containing histone H3 lysine 9/36 demethylase enzymes, belonging to the 2-OG-dependent oxygenases, which are upregulated in multiple malignancies. In the recent years, these enzymes have captured much attention as a novel target in cancer therapy. Herein, we traverse the discovery path and current challenges in designing potent KDM4 inhibitors as potential anticancer agents. We discuss the considerable efforts and proposed future strategies to develop selective small molecule inhibitors of KDM4s, highlighting scaffold candidates and cyclic skeletons for which activity data, selectivity profiles and structure-activity relationships (SARs) have been studied.

Recent advances in biological activities of rhodium complexes: Their applications in drug discovery research

Unique structure, characteristic reactivity, and facile synthesis of metal complexes have made them efficient ligands in drug development research. Among them, rhodium complexes have a limited history and there are a few discussions about their biological activities documented in the literature. However, investigation of kinetically inert rhodium complexes has recently attracted lots of attention and especially there are various evidences on their anti-cancer activity. It seems that they can be investigated as a versatile surrogates or candidates for the existing drugs which do not affect selectively or suffer from various side effects. In recent years, there has been an increasing interest in the use of mononuclear rhodium (III) organometallo drugs due to its versatile structurally important aspects to inhibit various enzymes. It has been demonstrated that organometallic Rh complexes profiting from both organic and inorganic aspects have shown more potent biological activities than classical inorganic compartments. In this respect, smart design, use of the appropriate organic ligands, and efficient and user-friendly synthesis of organometallic Rh complexes have played crucial roles in the inducing desirable biological activities. In this review, we focused on the recent advances published on the bioactivity of Rh (III/II/I) complexes especially inhibitory activity, from 2013 till now. Accordingly, considering the structure-activity relationship (SAR), the effect of oxidation state (+1, +2, and +3) and geometry (dimer or monomer complexes with coordination number of 4 and 6) of Rh complexes as well as various ligands on in vitro and in vivo studies was comprehensively discussed.

Discovery of a Copper-Based Mcl-1 Inhibitor as an Effective Antitumor Agent

Myeloid cell leukemia 1 (Mcl-1), which belongs to the Bcl-2 family of prosurvival proteins, is a key regulator of cancer cell survival. To date, few drug-like Mcl-1 inhibitors have been reported. Herein, we report the preparation of 10 copper complexes with 9-substituted β-carboline ligands that act as metal-based Mcl-1 inhibitors. Complex 14 was identified as a potent and selective Mcl-1 inhibitor with strong in vitro antitumor activity. Mechanistic studies demonstrated that complex 14 disrupted Mcl-1-Bax/Bak heterodimerization and induced Bax/Bak-dependent apoptosis. In addition, complex 14 significantly (P < 0.001) inhibited tumor growth in vivo, induced tumor necrosis, and extended survival time in an NCI-H460 xenograft model. Furthermore, complex 14 showed no apparent toxicity in mice. Together, these findings indicate that complex 14 is a copper-based Mcl-1 inhibitor with high efficacy and low toxicity that could be developed for the treatment of Mcl-1-related cancers.

Modified linear regression predicts drug-target interactions accurately

State-of-the-art approaches for the prediction of drug-target interactions (DTI) are based on various techniques, such as matrix factorisation, restricted Boltzmann machines, network-based inference and bipartite local models (BLM). In this paper, we propose the framework of Asymmetric Loss Models (ALM) which is more consistent with the underlying chemical reality compared with conventional regression techniques. Furthermore, we propose to use an asymmetric loss model with BLM to predict drug-target interactions accurately. We evaluate our approach on publicly available real-world drug-target interaction datasets. The results show that our approach outperforms state-of-the-art DTI techniques, including recent versions of BLM.

Imidazole and Benzimidazole Modified Half-Sandwich IridiumIII N-Heterocyclic Carbene Complexes: Synthesis, Anticancer Application, and Organelle Targeting

Herein, we report the synthesis, characterization and anticancer activity of a series of half-sandwich iridium^III imidazole and benzimidazole N-heterocyclic carbene (NHC) anticancer complexes, and the general formula of which can be expressed as [(η⁵-Cp^x)Ir(C^∧N)Cl]Cl (Cp^x: pentamethylcyclopentadienyl (Cp^*) or biphenyl derivatives (Cp^xbiph); C^∧N: imidazole and benzimidazole NHC chelating ligands). Compared with cis-platin, these complexes showed interesting antitumor activity against A549 cells. Complexes could bind to bovine serum albumin (BSA) by means of static quenching mode, catalyze the oxidation of nicotinamide adenine dinucleotide (NADH) and increase the levels of reactive oxygen species (ROS). Meanwhile, these complexes could arrest the cell cycles of A549 cells and influence the mitochondrial membrane potential significantly. Due to the inherent luminescence property, laser confocal test show that complexes could enter cells followed an energy-dependent mechanism and effectively accumulate in lysosome (the value of Pearson's co-localization coefficient is 0.70 after 1 h), further destroy lysosome integrity and induce apoptosis.

Cyclometalated Ir(III)-8-oxychinolin complexes acting as red-colored probes for specific mitochondrial imaging and anticancer drugs

A new class of luminescent Ir^III antitumor agents, namely, [Ir(CP1)(PY1)₂] (Ir-1), [Ir(CP1)(PY2)₂] (Ir-2), [Ir(CP1)(PY4)₂] (Ir-3), [Ir(CP2)(PY1)₂] (Ir-4), [Ir(CP2)(PY4)₂] (Ir-5), [Ir(CP3)(PY1)₂]⋅CH₃OH (Ir-6), [Ir(CP4)(PY4)₂]⋅CH₃OH (Ir-7), [Ir(CP5)(PY2)₂] (Ir-8), [Ir(CP5)(PY4)₂]⋅CH₃OH (Ir-9), [Ir(CP6)(PY1)₂] (Ir-10), [Ir(CP6)(PY2)₂]⋅CH₃OH (Ir-11), [Ir(CP6)(PY3)₂] (Ir-12), [Ir(CP6)(PY41)₂] (Ir-13), and [Ir(CP7)(PY1)₂] (Ir-14), supported by 8-oxychinolin derivatives and 1-phenylpyrazole ligands was prepared. Compared with SK-OV-3/DDP and HL-7702 cells, the Ir-1-Ir-14 compounds exhibited half maximal inhibitory concentration (IC₅₀) values within the high nanomolar range (50 nM-10.99 μM) in HeLa cells. In addition, Ir-1 and Ir-3 accumulated and stained the mitochondrial inner membrane of HeLa cells with high selectivity and exhibited a high antineoplastic activity in the entire cervical HeLa cells, with IC₅₀ values of 1.22 ± 0.36 μM and 0.05 ± 0.04 μM, respectively. This phenomenon induced mitochondrial dysfunction, suggesting that these cyclometalated Ir^III complexes can be potentially used in biomedical imaging and Ir(III)-based anticancer drugs. Furthermore, the high cytotoxicity activity of Ir-3 is correlated with the 1-phenylpyrazole (H-PY4) secondary ligands in the luminescent Ir^III antitumor complex.

Serum proteomics analysis based on label-free revealed the protective effect of Chinese herbal formula Gu-Ben-Fang-Xiao

Gubenfangxiao decoction (GBFXD) is a traditional Chinese medicine formula derived from Yupingfengsan, an ancient formula widely used to treat respiratory diseases. In recent years, GBFXD has been applied to efficaciously and safely treat asthma. However, the mechanism of GBFXD is still not fully elucidated. The aim of this study was to employ the label-free proteomic method to explore the protective mechanism of GBFXD in respiratory syncytial virus (RSV)-ovalbumin (OVA) induced chronic persistent asthmatic mice. After RSV-OVA challenge, mice were orally administered GBFXD at a dose of 36 g/kg accompanied with OVA nasal spray once every 3 days for 28 days. The label-free proteomics-based liquid chromatography-tandem mass spectrometry method was used to explore the differentially abundant proteins (DAPs) in the serum from model mice compared with that in control mice (M:C), and in GBFXD-treated mice compared with that in model mice (G:M). The mass spectrometry proteomics data have been deposited to the ProteomeXchange with identifier PXD013244. A total of 69 significant DAPs were identified including 39 in M:C, 46 in G:M, and 16 common differential proteins. Bioinformatics analysis revealed that the DAPs of M:C were mainly involved in inflammatory response and were related to lipid metabolism. However, the DAPs of G:M mostly participated in stress response, inflammatory response, and epithelial cell proliferation. Serum levels of Apoa-1, Apoc-1, Cfd, and Lrg1, EGFR and Lrg1 in the lungs were consistent with the results of proteomic analysis. Apoa-1 and Apoc-1 were closely related to cholesterol transport, lipid metabolism balance, and airway epithelial integrity; Cfd participated in immune response, affecting the occurrence and development of inflammation; EGFR and Lrg1 were involved in epithelial cell proliferation, influencing the process of airway remodeling. In summary, these results indicated that GBFXD may affect inflammatory and immune response of asthma by regulating cholesterol transport and complement factor activation. Furthermore, it could repair damaged airway epithelium and avoid airway remodeling to prevent and treat asthma.

Structure-Based Discovery of a Selective KDM5A Inhibitor that Exhibits Anti-Cancer Activity via Inducing Cell Cycle Arrest and Senescence in Breast Cancer Cell Lines

Breast cancer is the one of the most frequent causes of female cancer mortality. KDM5A, a histone demethylase, can increase the proliferation, metastasis, and drug resistance of cancers, including breast cancer, and is thus an important therapeutic target. In the present work, we performed hierarchical virtual screening towards the KDM5A catalytic pocket from a chemical library containing 90,000 compounds. Using multiple biochemical methods, the cyclopenta[c]chromen derivative 1 was identified as the top candidate for KDM5A demethylase inhibitory activity. Compared with the well-known KDM5 inhibitor CPI-455 (18), 1 exhibited higher potency against KDM5A and much higher selectivity for KDM5A over both KDM4A and other KDM5 family members (KDM5B and KDM5C). Additionally, compound 1 repressed the proliferation of various KDM5A-overexpressing breast cancer cell lines. Mechanistically, 1 promoted accumulation of p16 and p27 by blocking KDM5A-mediated H3K4me3 demethylation, leading to cell cycle arrest and senescence. To date, compound 1 is the first cyclopenta[c]chromen-based KDM5A inhibitor reported, and may serve as a novel motif for developing more selective and efficacious pharmacological molecules targeting KDM5A. In addition, our research provides a possible anti-cancer mechanism of KDM5A inhibitors and highlights the feasibility and significance of KDM5A as a therapeutic target for KDM5A-overexpressing breast cancer.

Pharmacological Inhibition of LSD1 for Cancer Treatment

Lysine-specific demethylase 1A (LSD1, also named KDM1A) is a demethylase that can remove methyl groups from histones H3K4me1/2 and H3K9me1/2. It is aberrantly expressed in many cancers, where it impedes differentiation and contributes to cancer cell proliferation, cell metastasis and invasiveness, and is associated with inferior prognosis. Pharmacological inhibition of LSD1 has been reported to significantly attenuate tumor progression in vitro and in vivo in a range of solid tumors and acute myeloid leukemia. This review will present the structural aspects of LSD1, its role in carcinogenesis, a comparison of currently available approaches for screening LSD1 inhibitors, a classification of LSD1 inhibitors, and its potential as a drug target in cancer therapy.

Small molecule KDM4s inhibitors as anti-cancer agents

Histone demethylation is a vital process in epigenetic regulation of gene expression. A number of histone demethylases are present to control the methylated states of histone. Among these enzymes, KDM4s are one subfamily of JmjC KDMs and play important roles in both normal and cancer cells. The discovery of KDM4s inhibitors is a potential therapeutic strategy against different diseases including cancer. Here, we summarize the development of KDM4s inhibitors and some related pharmaceutical information to provide an update of recent progress in KDM4s inhibitors.

Discovery of a New Four-Leaf Clover-Like Ligand as a Potent c-MYC Transcription Inhibitor Specifically Targeting the Promoter G-Quadruplex

Downregulating transcription of the oncogene c-MYC is a feasible strategy for cancer therapy. Stabilization of the G-quadruplex structure present in the c-MYC promoter can suppress c-MYC transcription. Thus, far, several ligands targeting this structure have been developed. However, most have shown no selectivity for the c-MYC G-quadruplex over other G-quadruplexes, leading to uncertain side effects. In this study, through structural modification of aryl-substituted imidazole/carbazole conjugates, a brand-new, four-leaf clover-like ligand called IZCZ-3 was found to preferentially bind and stabilize the c-MYC G-quadruplex. Further intracellular studies indicated that IZCZ-3 provoked cell cycle arrest and apoptosis and thus inhibited cell growth, primarily by blocking c-MYC transcription through specific targeting of the promoter G-quadruplex structure. Notably, IZCZ-3 effectively suppressed tumor growth in a mouse xenograft model. Accordingly, this work provides an encouraging example of a selective small molecule that can target one particular G-quadruplex structure, and the selective ligand might serve as an excellent anticancer agent.

Anticancer activity of complexes of the third row transition metals, rhenium, osmium, and iridium

A summary of recent developments on the anticancer activity of complexes of rhenium, osmium, and iridium is described.

Inhibition of the p53/hDM2 protein-protein interaction by cyclometallated iridium(III) compounds

Inactivation of the p53 transcription factor by mutation or other mechanisms is a frequent event in tumorigenesis. One of the major endogenous negative regulators of p53 in humans is hDM2, a ubiquitin E3 ligase that binds to p53 causing proteasomal p53 degradation. In this work, a library of organometallic iridium(III) compounds were synthesized and evaluated for their ability to disrupt the p53/hDM2 protein-protein interaction. The novel cyclometallated iridium(III) compound 1 [Ir(eppy)₂(dcphen)](PF₆) (where eppy = 2-(4-ethylphenyl)pyridine and dcphen = 4, 7-dichloro-1, 10-phenanthroline) blocked the interaction of p53/hDM2 in human amelanotic melanoma cells. Finally, 1 exhibited anti-proliferative activity and induced apoptosis in cancer cell lines consistent with inhibition of the p53/hDM2 interaction. Compound 1 represents the first reported organometallic p53/hDM2 protein-protein interaction inhibitor.

Drug-target interaction prediction: A Bayesian ranking approach

BACKGROUND AND OBJECTIVE

In silico prediction of drug-target interactions (DTI) could provide valuable information and speed-up the process of drug repositioning - finding novel usage for existing drugs. In our work, we focus on machine learning algorithms supporting drug-centric repositioning approach, which aims to find novel usage for existing or abandoned drugs. We aim at proposing a per-drug ranking-based method, which reflects the needs of drug-centric repositioning research better than conventional drug-target prediction approaches.

METHODS

We propose Bayesian Ranking Prediction of Drug-Target Interactions (BRDTI). The method is based on Bayesian Personalized Ranking matrix factorization (BPR) which has been shown to be an excellent approach for various preference learning tasks, however, it has not been used for DTI prediction previously. In order to successfully deal with DTI challenges, we extended BPR by proposing: (i) the incorporation of target bias, (ii) a technique to handle new drugs and (iii) content alignment to take structural similarities of drugs and targets into account.

RESULTS

Evaluation on five benchmark datasets shows that BRDTI outperforms several state-of-the-art approaches in terms of per-drug nDCG and AUC. BRDTI results w.r.t. nDCG are 0.929, 0.953, 0.948, 0.897 and 0.690 for G-Protein Coupled Receptors (GPCR), Ion Channels (IC), Nuclear Receptors (NR), Enzymes (E) and Kinase (K) datasets respectively. Additionally, BRDTI significantly outperformed other methods (BLM-NII, WNN-GIP, NetLapRLS and CMF) w.r.t. nDCG in 17 out of 20 cases. Furthermore, BRDTI was also shown to be able to predict novel drug-target interactions not contained in the original datasets. The average recall at top-10 predicted targets for each drug was 0.762, 0.560, 1.000 and 0.404 for GPCR, IC, NR, and E datasets respectively.

CONCLUSIONS

Based on the evaluation, we can conclude that BRDTI is an appropriate choice for researchers looking for an in silico DTI prediction technique to be used in drug-centric repositioning scenarios. BRDTI Software and supplementary materials are available online at www.ksi.mff.cuni.cz/∼peska/BRDTI.

Discovery of pyrazolo[1,5-a]pyrimidine-3-carbonitrile derivatives as a new class of histone lysine demethylase 4D (KDM4D) inhibitors

Herein we report the discovery of a series of new small molecule inhibitors of histone lysine demethylase 4D (KDM4D). Molecular docking was first performed to screen for new KDM4D inhibitors from various chemical databases. Two hit compounds were retrieved. Further structural optimization and structure-activity relationship (SAR) analysis were carried out to the more selective one, compound 2, which led to the discovery of several new KDM4D inhibitors. Among them, compound 10r is the most potent one with an IC₅₀ value of 0.41±0.03μM against KDM4D. Overall, compound 10r could be taken as a good lead compound for further studies.

Luminescent Strategies for Label-Free G-Quadruplex-Based Enzyme Activity Sensing

By catalyzing highly specific and tightly controlled chemical reactions, enzymes are essential to maintaining normal cellular physiology. However, aberrant enzymatic activity can be linked to the pathogenesis of various diseases. Therefore, the unusual activity of particular enzymes can represent testable biomarkers for the diagnosis or screening of certain diseases. In recent years, G-quadruplex-based platforms have attracted wide attention for the monitoring of enzymatic activities. In this Personal Account, we discuss our group's works on the development of G-quadruplex-based sensing system for enzyme activities by using mainly iridium(III) complexes as luminescent label-free probes. These studies showcase the versatility of the G-quadruplex for developing assays for a variety of different enzymes.

Inhibitors of Protein Methyltransferases and Demethylases

Post-translational modifications of histones by protein methyltransferases (PMTs) and histone demethylases (KDMs) play an important role in the regulation of gene expression and transcription and are implicated in cancer and many other diseases. Many of these enzymes also target various nonhistone proteins impacting numerous crucial biological pathways. Given their key biological functions and implications in human diseases, there has been a growing interest in assessing these enzymes as potential therapeutic targets. Consequently, discovering and developing inhibitors of these enzymes has become a very active and fast-growing research area over the past decade. In this review, we cover the discovery, characterization, and biological application of inhibitors of PMTs and KDMs with emphasis on key advancements in the field. We also discuss challenges, opportunities, and future directions in this emerging, exciting research field.

Anticancer osmium complex inhibitors of the HIF-1α and p300 protein-protein interaction

The hypoxia inducible factor (HIF) pathway has been considered to be an attractive anti-cancer target. One strategy to inhibit HIF activity is through the disruption of the HIF-1α–p300 protein-protein interaction. We report herein the identification of an osmium(II) complex as the first metal-based inhibitor of the HIF-1α–p300 interaction. We evaluated the effect of complex 1 on HIF-1α signaling pathway in vitro and in cellulo by using the dual luciferase reporter assay, co-immunoprecipitation assay, and immunoblot assay. Complex 1 exhibited a dose-dependent inhibition of HRE-driven luciferase activity, with an IC₅₀ value of 1.22 μM. Complex 1 interfered with the HIF-1α–p300 interaction as revealed by a dose-dependent reduction of p300 co-precipitated with HIF-1α as the concentration of complex 1 was increased. Complex 1 repressed the phosphorylation of SRC, AKT and STAT3, and had no discernible effect on the activity of NF-κB. We anticipate that complex 1 could be utilized as a promising scaffold for the further development of more potent HIF-1α inhibitors for anti-cancer treatment.

Histone Lysine Demethylase Inhibitors

The dynamic regulation of covalent modifications to histones is essential for maintaining genomic integrity and cell identity and is often compromised in cancer. Aberrant expression of histone lysine demethylases has been documented in many types of blood and solid tumors, and thus demethylases represent promising therapeutic targets. Recent advances in high-throughput chemical screening, structure-based drug design, and structure-activity relationship studies have improved both the specificity and the in vivo efficacy of demethylase inhibitors. This review will briefly outline the connection between demethylases and cancer and will provide a comprehensive overview of the structure, specificity, and utility of currently available demethylase inhibitors. To date, a select group of demethylase inhibitors is being evaluated in clinical trials, and additional compounds may soon follow from the bench to the bedside.

Diiridium(iii) complexes: luminescent probes and sensors for G-quadruplex DNA and endoplasmic reticulum imaging

Two new dinuclear iridium (Ir) complexes bridged by a conjugated aromatic tppz ligand, (bhq)₂Ir(tppz)Ir(bhq)₂(1) and (ppy)₂Ir(tppz)Ir(ppy)₂(2) (bhq = benzo(h)quinolone, ppy = phenyl-pyridine, tppz = tetrapyrido[3,2-a:2′,3′-c:3′′,2′′-h:2′′′,3′′′-j]phenazine), were prepared.

A Rhodium(III) Complex as an Inhibitor of Neural Precursor Cell Expressed, Developmentally Down-Regulated 8-Activating Enzyme with in Vivo Activity against Inflammatory Bowel Disease

We report herein the identification of the rhodium(III) complex [Rh(phq)₂(MOPIP)]⁺ (1) as a potent and selective ATP-competitive neural precursor cell expressed, developmentally down-regulated 8 (NEDD8)-activating enzyme (NAE) inhibitor. Structure-activity relationship analysis indicated that the overall organometallic design of complex 1 was important for anti-inflammatory activity. Complex 1 showed promising anti-inflammatory activity in vivo for the potential treatment of inflammatory bowel disease.

Ester-Modified Cyclometalated Iridium(III) Complexes as Mitochondria-Targeting Anticancer Agents

Organometallic iridium complexes are potent anticancer candidates which act through different mechanisms from cisplatin-based chemotherapy regimens. Here, ten phosphorescent cyclometalated iridium(III) complexes containing 2,2'-bipyridine-4,4'-dicarboxylic acid and its diester derivatives as ligands are designed and synthesized. The modification by ester group, which can be hydrolysed by esterase, facilitates the adjustment of drug-like properties. The quantum yields and emission lifetimes are influenced by variation of the ester substituents on the Ir(III) complexes. The cytotoxicity of these Ir(III) complexes is correlated with the length of their ester groups. Among them, 4a and 4b are found to be highly active against a panel of cancer cells screened, including cisplatin-resistant cancer cells. Mechanism studies in vitro indicate that they undergo hydrolysis of ester bonds, accumulate in mitochondria, and induce a series of cell-death related events mediated by mitochondria. Furthermore, 4a and 4b can induce pro-death autophagy and apoptosis simultaneously. Our study indicates that ester modification is a simple and feasible strategy to enhance the anticancer potency of Ir(III) complexes.

A survey of the mechanisms of action of anticancer transition metal complexes

Metal complexes have been the subject of numerous investigations in oncology but, despite the plethora of newly synthesized compounds, their precise mechanisms of action remain generally unknown or, for the best, incompletely determined. The continuous development of efficient and sensitive techniques in analytical chemistry and molecular biology gives scientists new tools to gather information on how metal complexes can be effective toward cancer. This review focuses on recent findings about the anticancer mechanism of action of metal complexes and how the ligands can be used to tune their pharmacological and physicochemical properties.

Antagonizing STAT5B dimerization with an osmium complex

Targeting STAT5 is an appealing therapeutic strategy for the treatment of hematologic malignancies and inflammation. Here, we present the novel osmium(II) complex 1 as the first metal-based inhibitor of STAT5B dimerization. Complex 1 exhibited superior inhibitory activity against STAT5B DNA binding compared to STAT5A DNA binding. Moreover, 1 repressed STAT5B transcription and blocked STAT5B dimerization via binding to the STAT5B protein, thereby inhibiting STAT5B translocation to the nucleus. Furthermore, 1 was able to selectively inhibit STAT5B phosphorylation without affecting the expression level of STAT5B.