KDM5 family as therapeutic targets in breast cancer: Pathogenesis and therapeutic opportunities and challenges.

Breast cancer (BC) is the most frequent malignant cancer diagnosis and is a primary factor for cancer deaths in women. The clinical subtypes of BC include estrogen receptor (ER) positive, progesterone receptor (PR) positive, human epidermal growth factor receptor 2 (HER2) positive, and triple-negative BC (TNBC). Based on the stages and subtypes of BC, various treatment methods are available with variations in the rates of progression-free disease and overall survival of patients. However, the treatment of BC still faces challenges, particularly in terms of drug resistance and recurrence. The study of epigenetics has provided new ideas for treating BC. Targeting aberrant epigenetic factors with inhibitors represents a promising anticancer strategy. The KDM5 family includes four members, KDM5A, KDM5B, KDM5C, and KDMD, all of which are Jumonji C domain-containing histone H3K4me2/3 demethylases. KDM5 proteins have been extensively studied in BC, where they are involved in suppressing or promoting BC depending on their specific upstream and downstream pathways. Several KDM5 inhibitors have shown potent BC inhibitory activity in vitro and in vivo, but challenges still exist in developing KDM5 inhibitors. In this review, we introduce the subtypes of BC and their current therapeutic options, summarize KDM5 family context-specific functions in the pathobiology of BC, and discuss the outlook and pitfalls of KDM5 inhibitors in this disease.

Repurposing sodium stibogluconate as an uracil DNA glycosylase inhibitor against prostate cancer using a time-resolved oligonucleotide-based drug screening platform.

Repurposing drugs can significantly reduce the time and costs associated with drug discovery and development. However, many drug compounds possess intrinsic fluorescence, resulting in aberrations such as auto-fluorescence, scattering and quenching, in fluorescent high-throughput screening assays. To overcome these drawbacks, time-resolved technologies have received increasing attention. In this study, we have developed a rapid and efficient screening platform based on time-resolved emission spectroscopy in order to screen for inhibitors of the DNA repair enzyme, uracil-DNA glycosylase (UDG). From a database of 1456 FDA/EMA-approved drugs, sodium stibogluconate was discovered as a potent UDG inhibitor. This compound showed synergistic cytotoxicity against 5-fluorouracil-resistant cancer cells. This work provides a promising future for time-resolved technologies for high-throughput screening (HTS), allowing for the swift identification of bioactive compounds from previously overlooked scaffolds due to their inherent fluorescence properties.

Recent Advances in Organometallic NIR Iridium(III) Complexes for Detection and Therapy.

Iridium(III) complexes are emerging as a promising tool in the area of detection and therapy due to their prominent photophysical properties, including higher photostability, tunable phosphorescence emission, long-lasting phosphorescence, and high quantum yields. In recent years, much effort has been devoted to develop novel near-infrared (NIR) iridium(III) complexes to improve signal-to-noise ratio and enhance tissue penetration. In this review, we summarize different classes of organometallic NIR iridium(III) complexes for detection and therapy, including cyclometalated ligand-enabled NIR iridium(III) complexes and NIR-dye-conjugated iridium(III) complexes. Moreover, the prospects and challenges for organometallic NIR iridium(III) complexes for targeted detection and therapy are discussed.

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 discoveries of the role of histone modifications and related inhibitors in pathological cardiac hypertrophy.

Pathological cardiac hypertrophy is a common response of the heart to various pathological stimuli. In recent years, various histone modifications, including acetylation, methylation, phosphorylation and ubiquitination, have been identified to have crucial roles in regulating chromatin remodeling and cardiac hypertrophy. Novel drugs targeting these epigenetic changes have emerged as potential treatments for pathological cardiac hypertrophy. In this review, we provide a comprehensive summary of the roles of histone modifications in regulating the development of pathological cardiac hypertrophy, and discuss potential therapeutic targets that could be utilized for its treatment.

A glycyrrhetinic acid-iridium(III) conjugate as a theranostic NIR probe for hepatocellular carcinoma with mitochondrial-targeting ability.

Hepatocellular carcinoma (HCC) is a major contributor to global mortality rates, but current treatment options have limitations. Advanced theranostics are needed to effectively integrate diagnosis and therapeutic of HCC. Glycyrrhetinic acid (GA) has abundant binding sites with glycyrrhetinic acid receptors (GA-Rs) on the surface of HCC cells and has also been reported to possess ligands with mitochondrial-targeting capability but with limited efficacy. Herein, we report a near-infrared (NIR) luminescent theranostic complex 1 through conjugating an iridium(III) complex to GA, which exhibits the desired photophysical properties and promotes mitochondrial-targeting capability. Complex 1 was selectively taken up by HepG2 liver cancer cells and was imaged within mitochondria with NIR emission. Complex 1 targeted mitochondria and opened mitochondrial permeability transition pores (MPTPs), resulting in ROS accumulation, mitochondrial damage, disruption of Bax/Bcl-2 equilibrium, and tumor cell apoptosis, resulting in significantly improved anticancer activity compared to GA. This work offers a methodology for developing multifunctional theranostic probes with amplified specificity and efficacy.

A Switch-On Affinity-Based Iridium(III) Conjugate Probe for Imaging Mitochondrial Glutathione S-Transferase in Breast Cancer Cells.

Glutathione S-transferase is heterogeneously expressed in breast cancer cells and is therefore emerging as a potential diagnostic biomarker for studying the heterogeneity of breast cancers. However, available fluorescent probes for GSTs depend heavily on GSTs-catalyzed glutathione (GSH) nucleophilic substitution reactions, making them susceptible to interference by the high concentration of nucleophilic species in the cellular environment. Moreover, the functions of subcellular GSTs are generally overlooked due to the lack of suitable luminescence probes. Herein, we report a highly selective affinity-based luminescence probe 1 for GST in breast cancer cells through tethering a GST inhibitor, ethacrynic acid, to an iridium(III) complex. Compared to activity-based probes which require the use of GSH, this probe could image GST-pi in the mitochondria by directly adducting to GST-pi (or potentially GST-pi/GS) in living cells. Probe 1 possesses desirable photophysical properties including a lifetime of 911 ns, a Stokes shift of 343 nm, and high photostability. The "turn on" luminescence mode of the probe enables highly selective detection of the GST with a limit of detection of 1.01 µM, while its long emission lifetime allows sensitive detection in organic dye-spiked autofluorescence samples by a time-resolved mode. The probe was further applied to specifically and quantitatively visualize MDA-MB-231 cells via specific binding to mitochondrial GST, and could differentiate breast cell lines based on their expression levels of GST. To the best of our knowledge, this probe is the first affinity-based iridium(III) imaging probe for the subcellular GST. Our work provides a valuable tool for unmasking the diverse roles of a subcellular GST in living systems, as well as for studying the heterogeneity of breast cancers.

Exosomal miRNA-mediated intercellular communications and immunomodulatory effects in tumor microenvironments.

Extracellular communication, in other words, crosstalk between cells, has a pivotal role in the survival of an organism. This communication occurs by different methods, one of which is extracellular vesicles. Exosomes, which are small lipid extracellular vesicles, have recently been discovered to have a role in signal transduction between cells inside the body. These vesicles contain important bioactive molecules including lipids, proteins, DNA, mRNA, and noncoding RNAs such as microRNAs (miRNAs). Exosomes are secreted by all cells including immune cells (macrophages, lymphocytes, granulocytes, dendritic cells, mast cells) and tumor cells. The tumor microenvironment (TME) represents a complex network that supports the growth of tumor cells. This microenvironment encompasses tumor cells themselves, the extracellular matrix, fibroblasts, endothelial cells, blood vessels, immune cells, and non-cellular components such as exosomes and cytokines. This review aims to provide insights into the latest discoveries concerning how the immune system communicates internally and with other cell types, with a specific focus on research involving exosomal miRNAs in macrophages, dendritic cells, B lymphocytes, and T lymphocytes. Additionally, we will explore the role of exosomal miRNA in the TME and the immunomodulatory effect.

Highly Active Single-Atom Nanozymes with High-Loading Iridium for Sensitive Detection of Pesticides.

Single-atom nanozymes (SAzymes) are novel mimic-enzyme materials with atomically doped active sites. They play a pivotal role in the field of nanozymes because of their excellent catalytic activities, high utilization efficiency of the metal atoms, and simple model of active sites. Herein, the peroxidase (POD)-like SAzymes with high-loading iridium (Ir) (5.31%) on graphene oxide (GO) nanosheets [Ir(III)/GO] were prepared through a coordination reaction between the Ir(III) complex and the oxygen-containing groups in GO. The preparation strategy avoids nitrogen doping and pyrolysis procedures which are the usually used strategies to improve the GO-based enzyme mimic activity. Ascribed to the highly active Ir atoms, Ir(III)/GO SAzymes demonstrate outstanding POD-like activity without the oxidase-like activity. In advantage of the excellent POD-like activity, a simple and sensitive colorimetric pesticide detection platform is established. The developed sensing platform offers an excellent "switch-on" pirimicarb (PIB) detection in the linear range of 10-300 nM with a limit of detection (LOD) of 2.81 nM. Moreover, the detection platform was fabricated into a portable test kit, which is composed of a test swab and sample processing tube. In the aid of a color-reading APP, the test kit can detect PIB with the LOD of 3.31 nM. It is astonishing to get this excellent detection sensitivity just using the simple colorimetric strategy. This work not only provides a novel strategy to synthesize Ir-based SAzymes but also exhibits the super capability of Ir(III)/GO in the biosensing field.

A cell-impermeable luminogenic probe for near-infrared imaging of prostate-specific membrane antigen in prostate cancer microenvironments.

Prostate-specific membrane antigen (PSMA) imaging probes are a promising tool for the diagnosis and image-guided surgery of prostate cancer (PCa). However, PSMA-specific luminescence probes for PCa detection and heterogeneity studies with high imaging contrast are lacking. Here, we report the first near-infrared (NIR) iridium(III) complex for the wash-free and specific imaging of PSMA in PCa cells and spheroids. The conjugation of a PSMA inhibitor, Lys-urea-Glu, to an iridium(III) complex synergizes the PSMA-specific affinity and biocompatibility of the inhibitor with the desirable photophysical properties of the iridium(III) complex, including NIR emission (670 nm), high photostability and a large Stokes shift. The cellular impermeability of the probe along with its strong binding affinity to PSMA enhances its specificity for PSMA, enabling the washing-free luminescent imaging of membrane PSMA with lower cytotoxicity. The probe was successfully applied for selectively visualizing PSMA-expressing cells and for the imaging of PSMA in a multicellular PCa model with good imaging penetration, indicating its potential use in complicated and heterogeneous tumor microenvironments. Furthermore, the probe showed good imaging performance in the PCa-bearing tumor mice via targeting PSMA in vivo. This work provides a novel strategy for the development of highly sensitive and specific NIR probes for PSMA in biological systems in vitro, which is of great significance for the precise diagnosis of PCa and for elucidating PCa heterogeneity.

A robust luminescent assay for screening alkyladenine DNA glycosylase inhibitors to overcome DNA repair and temozolomide drug resistance.

Temozolomide (TMZ) is an anticancer agent used to treat glioblastoma, typically following radiation therapy and/or surgical resection. However, despite its effectiveness, at least 50% of patients do not respond to TMZ, which is associated with repair and/or tolerance of TMZ-induced DNA lesions. Studies have demonstrated that alkyladenine DNA glycosylase (AAG), an enzyme that triggers the base excision repair (BER) pathway by excising TMZ-induced N3-methyladenine (3meA) and N7-methylguanine lesions, is overexpressed in glioblastoma tissues compared to normal tissues. Therefore, it is essential to develop a rapid and efficient screening method for AAG inhibitors to overcome TMZ resistance in glioblastomas. Herein, we report a robust time-resolved photoluminescence platform for identifying AAG inhibitors with improved sensitivity compared to conventional steady-state spectroscopic methods. As a proof-of-concept, this assay was used to screen 1440 food and drug administration-approved drugs against AAG, resulting in the repurposing of sunitinib as a potential AAG inhibitor. Sunitinib restored glioblastoma (GBM) cancer cell sensitivity to TMZ, inhibited GBM cell proliferation and stem cell characteristics, and induced GBM cell cycle arrest. Overall, this strategy offers a new method for the rapid identification of small-molecule inhibitors of BER enzyme activities that can prevent false negatives due to a fluorescent background.

The role and prospect of lysine-specific demethylases in cancer chemoresistance.

Histone methylation plays a key function in modulating gene expression, and preserving genome integrity and epigenetic inheritance. However, aberrations of histone methylation are commonly observed in human diseases, especially cancer. Lysine methylation mediated by histone methyltransferases can be reversed by lysine demethylases (KDMs), which remove methyl marks from histone lysine residues. Currently, drug resistance is a main impediment for cancer therapy. KDMs have been found to mediate drug tolerance of many cancers via altering the metabolic profile of cancer cells, upregulating the ratio of cancer stem cells and drug-tolerant genes, and promoting the epithelial-mesenchymal transition and metastatic ability. Moreover, different cancers show distinct oncogenic addictions for KDMs. The abnormal activation or overexpression of KDMs can alter gene expression signatures to enhance cell survival and drug resistance in cancer cells. In this review, we describe the structural features and functions of KDMs, the KDMs preferences of different cancers, and the mechanisms of drug resistance resulting from KDMs. We then survey KDM inhibitors that have been used for combating drug resistance in cancer, and discuss the opportunities and challenges of KDMs as therapeutic targets for cancer drug resistance.

Synthesis and luminescence monitoring of iridium(III) complex-functionalized gold nanoparticles and their application for determination of gold(III) ions.

A new method is presented for the one-step synthesis and real-time monitoring of iridium(III) complex-functionalized AuNPs from the precursor gold(III) chloride (AuCl3). The functionalized AuNPs with an average size of 8 - 20 nm were obtained by the reduction of Au3+ ions by the alkyne group of iridium(III) complexes, which was accompanied by the anchoring iridium(III) complexes on the surface of the nanoparticles. Meanwhile, the luminescence of the iridium(III) complexes was effectively quenched due to distance-dependent fluorescence quenching by AuNPs, thereby enabling luminescence monitoring of the formation process of the functionalized AuNPs and obtaining scattering information and spectral information in real time. Moreover, this method was applied to the determination of Au3+ ions in buffer with a limit of detection of 0.38 µM at 700 nm in luminescence mode, while the detection limit for absorbance was 10.04 µM. Importantly, the multimodal detection strategy alleviates interference from other metal ions. Furthermore, the iridium(III) alkyne complexes were capable of imaging mitochondrial Au3+ ions in living cells. Taken together, this work opens a new avenue for convenient synthesis and monitoring formation of functionalized AuNPs, and also provides a tool for selective determination of Au3+ ions in solution and in cellulo.

Imaging mitochondrial palladium species in living cells with a NIR iridium(III) complex.

The wide use of palladium (Pd) raises the concern about environmental pollution and human diseases, evoking the need for the development of detection methods for Pd species. However, the development of near-infrared (NIR) luminescence probes for subcellular Pd species remains challenging. In this work, we presented a NIR iridium(III) complex-based luminescence probe for the detection of Pd0 species through incorporating an allyl group and amino group into the N^N ligand. We found that the probe was capable of detecting Pd0 species with a limit of detection (LOD) of 0.5 µM. Importantly, cell imaging experiments showed that the probe is applicable for visualizing mitochondrial Pd0 ions in living cells, which are also suitable for Pd(II) species. To the best of our knowledge, this is the first NIR luminescence imaging probe for the detection of mitochondria Pd species in living cells, paving the way for studying subcellular distributions and related toxicity analysis of exogenous Pd species in living cells.

Interference reduction isothermal nucleic acid amplification strategy for COVID-19 variant detection.

Common reference methods for COVID-19 variant diagnosis include viral sequencing and PCR-based methods. However, sequencing is tedious, expensive, and time-consuming, while PCR-based methods have high risk of insensitive detection in variant-prone regions and are susceptible to potential background signal interference in biological samples. Here, we report a loop-mediated interference reduction isothermal nucleic acid amplification (LM-IR-INA) strategy for highly sensitive single-base mutation detection in viral variants. This strategy exploits the advantages of nicking endonuclease-mediated isothermal amplification, luminescent iridium(III) probes, and time-resolved emission spectroscopy (TRES). Using the LM-IR-INA strategy, we established a luminescence platform for diagnosing COVID-19 D796Y single-base substitution detection with a detection limit of 2.01 × 105 copies/µL in a linear range of 6.01 × 105 to 3.76 × 108 copies/µL and an excellent specificity with a variant/wild-type ratio of significantly less than 0.0625%. The developed TRES-based method was also successfully applied to detect D796Y single-base substitution sequence in complicated biological samples, including throat and blood, and was a superior to steady-state technique. LM-IR-INA was also demonstrated for detecting the single-base substitution D614G as well as the multiple-base mutation H69/V70del without mutual interference, indicating that this approach has the potential to be used as a universal viral variant detection strategy.

Discovery of a tetrahydroisoquinoline-based CDK9-cyclin T1 protein-protein interaction inhibitor as an anti-proliferative and anti-migration agent against triple-negative breast cancer cells.

Triple-negative breast cancer (TNBC) is a highly aggressive and metastasizing cancer that has the worst prognosis out of all breast cancer subtypes. The epithelial-mesenchymal transition (EMT) and cancer stem cells (CSCs) have been proposed as important mechanisms underlying TNBC metastasis. CDK9 is highly expressed in breast cancer, including TNBC, where it promotes EMT and induces cancer cell stemness. In this study, we have identified a tetrahydroisoquinoline derivative (compound 1) as a potent and selective CDK9-cyclin T1 inhibitor via virtual screening. Interestingly, by targeting the ATP binding site, compound 1 not only inhibited CDK9 activity but also disrupted the CDK9-cyclin T1 protein-protein interaction (PPI). Mechanistically, compound 1 reversed EMT and reduced the ratio of CSCs by blocking the CDK9-cyclin T1 interaction, leading to reduced TNBC cell proliferation and migration. To date, compound 1 is the first reported tetrahydroisoquinoline-based CDK9-cyclin T1 ATP-competitive inhibitor that also interferes with the interaction between CDK9 and cyclin T1. Compound 1 may serve as a promising scaffold for developing more selective and potent anti-TNBC agents. Our work also provides insight into the role of the CDK9-cyclin T1 PPI on EMT and CSCs and highlights the feasibility and significance of targeting CDK9 for the treatment of TNBC.

Development of a NIR iridium(III) complex for self-calibrated and luminogenic detection of boron trifluoride.

Boron trifluoride (BF3) is a potential environmental pollutant, and excess exposure to it may cause human diseases. However, the sensitive, rapid and accurate detection of BF3 for on-site purposes is still a challenge. In this work, we developed the first NIR iridium(III)-based probe with dual emission and a Stokes shift of 370 nm for self-calibrated and luminogenic detection of BF3. This probe exhibited a strong luminescence enhancement at around 650 nm to BF3 (0-100 µM) with almost no change in luminescence at 475 nm, displaying a 220-fold I650 nm/I475 nm enhancement at 100 µM of BF3 with a detection limit of 0.35 µM. Moreover, the probe showed a fast response time of less than 5 s to BF3 along with an obvious color change under UV irradiation for visual detection. Importantly, the desirable photophysical properties of the iridium(III)-based probe can be harnessed for time-resolved detection of BF3 in the presence of the fluorescence background. The applicability of the probe was further verified in an organic solvent waste-spiked system and on a glass pane. This work will provide a solid basis for the development of sensitive and on-site BF3 sensing toolkits for environmental monitoring.