Development of an AlphaLISA high throughput technique to screen for small molecule inhibitors targeting protein arginine methyltransferases

Beyond VEGF: Targeting Inflammation and Other Pathways for Treatment of Retinal Disease

Neovascular eye diseases include conditions such as retinopathy of prematurity, proliferative diabetic retinopathy, and neovascular age-related macular degeneration. Together, they are a major cause of vision loss and blindness worldwide. The current therapeutic mainstay for these diseases is intravitreal injections of biologics targeting vascular endothelial growth factor (VEGF) signaling. Lack of universal response to these anti-VEGF agents coupled with the challenging delivery method underscore a need for new therapeutic targets and agents. In particular, proteins that mediate both inflammatory and proangiogenic signaling are appealing targets for new therapeutic development. Here, we review agents currently in clinical trials and highlight some promising targets in preclinical and early clinical development, focusing on the redox-regulatory transcriptional activator APE1/Ref-1, the bioactive lipid modulator soluble epoxide hydrolase, the transcription factor RUNX1, and others. Small molecules targeting each of these proteins show promise for blocking neovascularization and inflammation. The affected signaling pathways illustrate the potential of new antiangiogenic strategies for posterior ocular disease. SIGNIFICANCE STATEMENT: Discovery and therapeutic targeting of new angiogenesis mediators is necessary to improve treatment of blinding eye diseases like retinopathy of prematurity, diabetic retinopathy, and neovascular age-related macular degeneration. Novel targets undergoing evaluation and drug discovery work include proteins important for both angiogenesis and inflammation signaling, including APE1/Ref-1, soluble epoxide hydrolase, RUNX1, and others.

Nanofluidic Device for Detection of Lysine Methylpeptides and Sensing of Lysine Methylation

Protein methylation is the smallest possible yet vitally important post-translational modification (PTM). This small and chemically inert addition in proteins makes the analysis of methylation more challenging, thus calling for an efficient tool for the sake of recognition and detection. Herein, we present a nanofluidic electric sensing device based on a functionalized nanochannel that was constructed by introducing monotriazole-containing p-sulfonatocalix[4]arene (TSC) into a single asymmetric polymeric nanochannel via click chemistry. The device can selectively detect lysine methylpeptides with subpicomole sensitivity, distinguish between different lysine methylation states, and monitor the lysine methylation process by methyltransferase at the peptide level in real time. The introduced TSC molecule, with its confined asymmetric configuration, presents the remarkable ability to selectively bind to lysine methylpeptides, which, coupled with the release of the complexed Cu ions, allows the device to transform the molecular-level recognition to the discernible change in ionic current of the nanofluidic electric device, thus enabling detection. This work could serve as a stepping stone to the development of a new methyltransferase assay and the chemical that specifically targets lysine methylation in PTM proteomics.

Development of a Cell-Based AlphaLISA Assay for High-Throughput Screening for Small Molecule Proteasome Modulators

The balance between protein degradation and protein synthesis is a highly choreographed process generally called proteostasis. Most intracellular protein degradation occurs through the ubiquitin-proteasome system (UPS). This degradation takes place through either a ubiquitin-dependent or a ubiquitin-independent proteasomal pathway. The ubiquitin-independent pathway selectively targets unfolded proteins, including intrinsically disordered proteins (IDPs). Dysregulation of proteolysis can lead to the accumulation of IDPs, seen in the pathogenesis of various diseases, including cancer and neurodegeneration. Therefore, the enhancement of the proteolytic activity of the 20S proteasome using small molecules has been identified as a promising pathway to combat IDP accumulation. Currently, there are a limited number of known small molecules that enhance the activity of the 20S proteasome, and few are observed to exhibit enhanced proteasome activity in cell culture. Herein, we describe the development of a high-throughput screening assay to identify cell-permeable proteasome enhancers by utilizing an AlphaLISA platform that measures the degradation of a GFP conjugated intrinsically disordered protein, ornithine decarboxylase (ODC). Through the screening of the Prestwick and NIH Clinical Libraries, a kinase inhibitor, erlotinib, was identified as a new 20S proteasome enhancer, which enhances the degradation of ODC in cells and α-synuclein in vitro.

Discovery of New States of Immunomodulation for Vaccine Adjuvants via High Throughput Screening: Expanding Innate Responses to PRRs

Stimulation of the innate immune system is crucial in both effective vaccinations and immunotherapies. This is often achieved through adjuvants, molecules that usually activate pattern recognition receptors (PRRs) and stimulate two innate immune signaling pathways: the nuclear factor kappa-light-chain-enhancer of activated B-cells pathway (NF-κB) and the interferon regulatory factors pathway (IRF). Here, we demonstrate the ability to alter and improve adjuvant activity via the addition of small molecule "immunomodulators". By modulating signaling activity instead of receptor binding, these molecules allow the customization of select innate responses. We demonstrate both inhibition and enhancement of the products of the NF-κB and IRF pathways by several orders of magnitude. Some modulators apply generally across many receptors, while others focus specifically on individual receptors. Modulators boost correlates of a protective immune responses in a commercial flu vaccine model and reduced correlates of reactogenicity in a typhoid vaccine model. These modulators have a range of applications: from adjuvanticity in prophylactics to enhancement of immunotherapy.

PRMT5 is a therapeutic target in choroidal neovascularization

Ocular neovascular diseases including neovascular age-related macular degeneration (nvAMD) are widespread causes of blindness. Patients' non-responsiveness to currently used biologics that target vascular endothelial growth factor (VEGF) poses an unmet need for novel therapies. Here, we identify protein arginine methyltransferase 5 (PRMT5) as a novel therapeutic target for nvAMD. PRMT5 is a well-known epigenetic enzyme. We previously showed that PRMT5 methylates and activates a proangiogenic and proinflammatory transcription factor, the nuclear factor kappa B (NF-κB), which has a master role in tumor progression, notably in pancreatic ductal adenocarcinoma and colorectal cancer. We identified a potent and specific small molecule inhibitor of PRMT5, PR5-LL-CM01, that dampens the methylation and activation of NF-κB. Here for the first time, we assessed the antiangiogenic activity of PR5-LL-CM01 in ocular cells. Immunostaining of human nvAMD sections revealed that PRMT5 is highly expressed in the retinal pigment epithelium (RPE)/choroid where neovascularization occurs, while mouse eyes with laser induced choroidal neovascularization (L-CNV) showed PRMT5 is overexpressed in the retinal ganglion cell layer and in the RPE/choroid. Importantly, inhibition of PRMT5 by PR5-LL-CM01 or shRNA knockdown of PRMT5 in human retinal endothelial cells (HRECs) and induced pluripotent stem cell (iPSC)-derived choroidal endothelial cells (iCEC2) reduced NF-κB activity and the expression of its target genes, such as tumor necrosis factor α (TNF-α) and VEGF-A. In addition to inhibiting angiogenic properties of proliferation and tube formation, PR5-LL-CM01 blocked cell cycle progression at G1/S-phase in a dose-dependent manner in these cells. Thus, we provide the first evidence that inhibition of PRMT5 impedes angiogenesis in ocular endothelial cells, suggesting PRMT5 as a potential therapeutic target to ameliorate ocular neovascularization.

Discovery of novel PRMT5 inhibitors bearing a methylpiperazinyl moiety

Background: PRMT5 is an epigenetics-related enzyme, which plays a critical role in cancer development. Hence PRMT5 inhibition has been validated as a promising therapeutic strategy. Methods & Results: We synthesized a series of methylpiperazinyl derivatives as novel PRMT5 inhibitors that were achieved by scaffold-hopping from EPZ015666 by virtual screening followed by rational drug design. Among all compounds 43g, bearing a thiourea linker, showed antitumor activity across multiple cancer cell lines and reduced the level of symmetric arginine dimethylation of SmD3 dose-dependently. Moreover, 43g selectively inhibited PRMT5 among protein arginine methyltransferase isoforms. Further proteomics analysis revealed that 43g remarkably reduced the global arginine dimethylation level in a cellular context. Conclusion: This work provides new chemical templates for future structural optimization of PRMT5-related cancer treatments.

Inhibition of PRMT5 by market drugs as a novel cancer therapeutic avenue

Market drugs, such as Food and Drug Administration (FDA) or European Medicines Agency (EMA)-approved drugs for specific indications provide opportunities for repurposing for newer therapeutics. This potentially saves resources invested in clinical trials that verify drug safety and tolerance in humans prior to alternative indication approval. Protein arginine methyltransferase 5 (PRMT5) overexpression has been linked to promoting the tumor phenotype in several cancers, including pancreatic ductal adenocarcinoma (PDAC), colorectal cancer (CRC), and breast cancer (BC), making PRMT5 an important target for cancer therapy. Previously, we showed that PRMT5-mediated methylation of the nuclear factor (NF)-κB, partially contributes to its constitutive activation observed in cancers. In this study, we utilized an AlphaLISA-based high-throughput screening method adapted in our lab, and identified one FDA-approved drug, Candesartan cilexetil (Can, used in hypertension treatment) and one EMA-approved drug, Cloperastine hydrochloride (Clo, used in cough treatment) that had significant PRMT5-inhibitory activity, and their anti-tumor properties were validated using cancer phenotypic assays in vitro. Furthermore, PRMT5 selective inhibition of methyltransferase activity was confirmed by reduction of both NF-κB methylation and its subsequent activation upon drug treatment. Using in silico prediction, we identified critical residues on PRMT5 targeted by these drugs that may interfere with its enzymatic activity. Finally, Clo and Can treatment have exhibited marked reduction in tumor growth in vivo. Overall, we provide basis for pursuing repurposing Clo and Can as anti-PRMT5 cancer therapies. Our study offers potential safe and fast repurposing of previously unknown PRMT5 inhibitors into clinical practice.

Screening for Small-Molecule Inhibitors of Histone Methyltransferases

Potent and highly selective small-molecule inhibitors are needed to unravel the biological complexities of histone methyltransferases and to reveal their therapeutic potential. A prerequisite to developing these inhibitors is the identification of validated chemical matter for initiating a medicinal chemistry campaign. For the most part, finding these initial starting points occurs through screening of large, unbiased compound libraries. The size and nature of these libraries, coupled with the complexities of the bisubstrate utilizing histone methyltransferases, necessitates that the primary screen and subsequent hit triage be carefully considered.In this chapter, using EZH2 as a representative example, we describe a screening and hit triage campaign that identified validated chemical matter allowing initiation of medicinal chemistry studies. Moreover, we discuss a cell-based assay to support lead identification and optimization. The approach described here entailing a mixture of biochemical, biophysical and cell-based assays should be applicable to identifying validated starting points for other histone methyltransferases.

Screening S protein - ACE2 blockers from natural products: Strategies and advances in the discovery of potential inhibitors of COVID-19

The Coronavirus disease, 2019 (COVID-19) is caused by severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2), which poses a major threat to human life and health. Given its continued development, limiting the spread of COVID-19 in the population remains a challenging task. Currently, multiple therapies are being tried around the world to deal with SARS-CoV-2 infection, and a variety of studies have shown that natural products have a significant effect on COVID-19 patients. The combination of SARS-CoV-2 S protein with Angiotensin converting enzyme II(ACE2) of host cell to promote membrane fusion is an initial critical step for SARS-CoV-2 infection. Therefore, screening natural products that inhibit the binding of SARS-CoV-2 S protein and ACE2 also provides a feasible strategy for the treatment of COVID-19. Establishment of high throughput screening model is an important basis and key technology for screening S protein-ACE2 blockers. Based on this, the molecular structures of SARS-CoV-2 and ACE2 and their processes in the life cycle of SARS-CoV-2 and host cell infection were firstly reviewed in this paper, with emphasis on the methods and techniques of screening S protein-ACE2 blockers, including Virtual Screening (VS), Surface Plasmon Resonance (SPR), Biochromatography, Biotin-avidin with Enzyme-linked Immunosorbent assay and Gene Chip Technology. Furthermore, the technical principle, advantages and disadvantages and application scope were further elaborated. Combined with the application of the above screening technologies in S protein-ACE2 blockers, a variety of natural products, such as flavonoids, terpenoids, phenols, alkaloids, were summarized, which could be used as S protein-ACE2 blockers, in order to provide ideas for the efficient discovery of S protein-ACE2 blockers from natural sources and contribute to the development of broad-spectrum anti coronavirus drugs.

Protein arginine N-methyltransferase 5 in colorectal carcinoma: Insights into mechanisms of pathogenesis and therapeutic strategies

Protein arginine N-methyltransferase 5 (PRMT5) enzyme is one of the eight canonical PRMTs, classified as a type II PRMT, induces arginine monomethylation and symmetric dimethylation. PRMT5 is known to be overexpressed in multiple cancer types, including colorectal cancer (CRC), where its overexpression is associated with poor survival. Recent studies have shown that upregulation of PRMT5 induces tumor growth and metastasis in CRC. Moreover, various novel PRMT5 inhibitors tested on CRC cell lines showed promising anticancer effects. Also, it was suggested that PRMT5 could be a valid biomarker for CRC diagnosis and prognosis. Hence, a deeper understanding of PRMT5-mediated CRC carcinogenesis could provide new avenues towards developing a targeted therapy. In this study, we started with in silico analysis correlating PRMT5 expression in CRC patients as a prelude to further our investigation of its role in CRC. We then carried out a comprehensive review of the scientific literature that dealt with the role(s) of PRMT5 in CRC pathogenesis, diagnosis, and prognosis. Also, we have summarized key findings from in vitro research using various therapeutic agents and strategies directly targeting PRMT5 or disrupting its function. In conclusion, PRMT5 seems to play a significant role in the pathogenesis of CRC; therefore, its prognostic and therapeutic potential merits further investigation.

Protein Arginine Methyltransferase (PRMT) Inhibitors-AMI-1 and SAH Are Effective in Attenuating Rhabdomyosarcoma Growth and Proliferation in Cell Cultures

Rhabdomyosarcoma (RMS) is a malignant soft tissue cancer that develops mostly in children and young adults. With regard to histopathology, four rhabdomyosarcoma types are distinguishable: embryonal, alveolar, pleomorphic and spindle/sclerosing. Currently, increased amounts of evidence indicate that not only gene mutations, but also epigenetic modifications may be involved in the development of RMS. Epigenomic changes regulate the chromatin architecture and affect the interaction between DNA strands, histones and chromatin binding proteins, thus, are able to control gene expression. The main aim of the study was to assess the role of protein arginine methyltransferases (PRMT) in the cellular biology of rhabdomyosarcoma. In the study we used two pan-inhibitors of PRMT, called AMI-1 and SAH, and evaluated their effects on proliferation and apoptosis of RMS cells. We observed that AMI-1 and SAH reduce the invasive phenotype of rhabdomyosarcoma cells by decreasing their proliferation rate, cell viability and ability to form cell colonies. In addition, microarray analysis revealed that these inhibitors attenuate the activity of the PI3K-Akt signaling pathway and affect expression of genes related to it.

The Pivotal Player: Components of NF-κB Pathway as Promising Biomarkers in Colorectal Cancer

Over the last several decades, colorectal cancer (CRC) has been one of the most prevalent cancers. While significant progress has been made in both diagnostic screening and therapeutic approaches, a large knowledge gap still remains regarding the early identification and treatment of CRC. Specifically, identification of CRC biomarkers that can help with the creation of targeted therapies as well as increasing the ability for clinicians to predict the biological response of a patient to therapeutics, is of particular importance. This review provides an overview of CRC and its progression stages, as well as the basic types of CRC biomarkers. We then lay out the synopsis of signaling pathways related to CRC, and further highlight the pivotal and multifaceted role of nuclear factor (NF) κB signaling in CRC. Particularly, we bring forth knowledge regarding the tumor microenvironment (TME) in CRC, and its complex interaction with cancer cells. We also provide examples of NF-κB signaling-related CRC biomarkers, and ongoing efforts made at targeting NF-κB signaling in CRC treatment. We conclude and anticipate that with more emerging novel regulators of the NF-κB pathway being discovered, together with their in-depth characterization and the integration of large groups of genomic, transcriptomic and proteomic data, the day of successful development of more ideal NF-κB inhibitors is fast approaching.

Application of an AlphaLISA method for rapid sensitive detection of African swine fever virus in porcine serum

Infection with African swine fever virus (ASFV) causes an acute and highly lethal hemorrhagic disease that has been responsible for huge economic losses in China. To exactly detect the antigen of ASFV, we established a rapid, no-wash, one-step sandwich-type immunoassay based on the amplified luminescent proximity homogenous assay-linked immunosorbent assay (AlphaLISA) using two monoclonal antibodies (mAbs) M-5 and M-6 against ASFV p72. ASFV p72 in samples was captured by biotinylated mAb M-5 connected to the donor bead surface via streptavidin and "sandwiched" by mAb M-6 which was coated onto the acceptor bead. Efficacy and sensitivity trials revealed that the AlphaLISA could detect ≥0.78 ng/ml of purified p72 and with a linear range of 0.78-100 ng/ml. The AlphaLISA was specific for ASFV and did not cross-react with other common pathogenic porcine viruses. Compared with RealPCR ASFV DNA test and ASFV antigen detection kit, the sensitivity of the AlphaLISA evaluated in 60 porcine serum samples was 93% and 100%, respectively. The specificity was 100% and 91.7%, respectively. This study presents a good laboratory diagnostic tool for sensitive and efficient detection of ASFV in porcine serum. KEY POINTS: • MAbs M-5 and M-6 recognized various epitopes of ASFV p72. • The established ASFV p72 AlphaLISA showed well specificity, high sensitivity, and satisfied correlation coefficient.

Biology of the mRNA Splicing Machinery and Its Dysregulation in Cancer Providing Therapeutic Opportunities

Dysregulation of messenger RNA (mRNA) processing—in particular mRNA splicing—is a hallmark of cancer. Compared to normal cells, cancer cells frequently present aberrant mRNA splicing, which promotes cancer progression and treatment resistance. This hallmark provides opportunities for developing new targeted cancer treatments. Splicing of precursor mRNA into mature mRNA is executed by a dynamic complex of proteins and small RNAs called the spliceosome. Spliceosomes are part of the supraspliceosome, a macromolecular structure where all co-transcriptional mRNA processing activities in the cell nucleus are coordinated. Here we review the biology of the mRNA splicing machinery in the context of other mRNA processing activities in the supraspliceosome and present current knowledge of its dysregulation in lung cancer. In addition, we review investigations to discover therapeutic targets in the spliceosome and give an overview of inhibitors and modulators of the mRNA splicing process identified so far. Together, this provides insight into the value of targeting the spliceosome as a possible new treatment for lung cancer.

Dysregulation of protein argininemethyltransferase in the pathogenesis of cancerpy

Arginine methylation is considered to be one of the most permanent and one of the most frequent post-translational modifications. The reaction of transferring a methyl group from S-adenosylmethionine to arginine residue is catalyzed by aginine methyltransferase (PRMT). In humans there are nine members of the PRMT family, named in order of discovery of PRMT1- PRMT9. Arginine methyltransferases were divided into three classes: I, II, III, with regard to the product of the catalyzed reaction. The products of their activity are, respectively, the following: asymmetric dimethylarginine (ADMA), symmetrical dimethylarginine (SDMA) and monomethylarginine (MMA). These modifications significantly affect the chromatin functions; therefore, they can act as co-activators or suppressors of the transcription process. Arginine methylation plays a crucial role in many biological processes in a human organism. Among others, it participates in signal transduction control, mRNA splicing and the regulation of basic cellular processes such as proliferation, differentiation, migration and apoptosis. There is increasing evidence that dysregulation of PRMT levels may lead to the cancer transformation of cells. The correlation between increased PRMT level and cancer has been demonstrated in the following: breast, ovary, lung and colorectal cancer. The activity of arginine methyltransferase can be regulated by small molecule PRMT inhibitors. To date, three substances that inhibit PRMT activity have been evaluated in clinical trials and exhibit anti-tumor activity against hematological cancer. It is believed that the use of specific PRMT inhibitors may become a new, effective and safe treatment of oncological diseases.

PRMT5 promotes colorectal cancer growth by interaction with MCM7

Protein arginine methyltransferase 5 (PRMT5) is a type of methyltransferase enzyme that can catalyse arginine methylation of histones and non‐histone proteins. Accumulating evidence indicates that PRMT5 promotes cancer development and progression. However, its function in colorectal cancer (CRC) is poorly understood. In this study, we revealed the oncogenic roles of PRMT5 in CRC. We found that PRMT5 promoted CRC cell proliferation, migration and invasion in vitro and in vivo. We identified minichromosome maintenance‐7 (MCM7) as the direct PRMT5‐binding partner. A co‐immunoprecipitation (co‐IP) assay indicated that PRMT5 physically interacted with MCM7 and that the direct binding domain was located between residues 1‐248 in MCM7. In addition, our results from analysis of 99 CRC tissues and 77 adjacent non‐cancerous tissues indicated that the PRMT5 and MCM7 expression levels were significantly higher in CRC tissues than in control tissues, which was further confirmed by bioinformatic analysis using TCGA and GEO datasets. We also found that MCM7 promoted CRC cell proliferation, migration and invasion in vitro. Furthermore, we observed that increased PRMT5 expression predicted unfavourable patient survival in CRC patients and in the subgroup of patients with a tumour size of ≤5 cm. These data suggested that PRMT5 and MCM7 might be novel potential targets for the treatment of CRC.

MAT2A Inhibition Blocks the Growth of MTAP-Deleted Cancer Cells by Reducing PRMT5-Dependent mRNA Splicing and Inducing DNA Damage

The methylthioadenosine phosphorylase (MTAP) gene is located adjacent to the cyclin-dependent kinase inhibitor 2A (CDKN2A) tumor-suppressor gene and is co-deleted with CDKN2A in approximately 15% of all cancers. This co-deletion leads to aggressive tumors with poor prognosis that lack effective, molecularly targeted therapies. The metabolic enzyme methionine adenosyltransferase 2α (MAT2A) was identified as a synthetic lethal target in MTAP-deleted cancers. We report the characterization of potent MAT2A inhibitors that substantially reduce levels of S-adenosylmethionine (SAM) and demonstrate antiproliferative activity in MTAP-deleted cancer cells and tumors. Using RNA sequencing and proteomics, we demonstrate that MAT2A inhibition is mechanistically linked to reduced protein arginine methyltransferase 5 (PRMT5) activity and splicing perturbations. We further show that DNA damage and mitotic defects ensue upon MAT2A inhibition in HCT116 MTAP-/- cells, providing a rationale for combining the MAT2A clinical candidate AG-270 with antimitotic taxanes.

Histone H4-based peptoids are inhibitors of protein arginine methyltransferase 1 (PRMT1)

Methylation of arginine residues occurs on a number of protein substrates, most notably the N-terminal tails of histones, and is catalyzed by a family of enzymes called the protein arginine methyltransferases (PRMTs). This modification can lead to transcriptional activation or repression of cancer-related genes. To date, a number of inhibitors, based on natural peptide substrates, have been developed for the PRMT family of enzymes. However, because peptides are easily degraded in vivo, the utility of these inhibitors as potential therapeutics is limited. The use of peptoids, which are peptide mimetics where the amino acid side chain is attached to the nitrogen in the amide backbone instead of the α-carbon, may circumvent the problems associated with peptide degradation. Given the structural similarities, peptoid scaffolds may provide enhanced stability, while preserving the mechanism of action. Herein, we have identified that peptoids based on natural peptide substrates are not catalyzed to the product by PRMT1, but instead are inhibitors of this enzyme. Reducing the length of the peptoid reduces inhibition and suggest the residues distal from the site of modification are important for binding. Furthermore, a positive charge on the N-terminus helps promote binding and improves inhibition. Selectivity among family members is likely possible based on inhibition being moderately selective for PRMT1 over PRMT5 and provides a scaffold that can be used to develop pharmaceuticals against this class of enzymes.

Comparative Analysis of Multiple Immunoassays for Cytokine Profiling in Drug Discovery

Cytokines and their receptors play critical roles in biological processes. Dysfunction or dysregulation of cytokines may cause a variety of pathophysiological conditions. Consequently, cytokine profiling and related technologies are essential for biological studies, disease diagnosis, and drug discovery. In this report, three cytokines, interleukin (IL)-1β, IL-6, and tumor necrosis factor alpha (TNF-α), from the same sets of samples were analyzed with several commonly used technologies (enzyme-linked immunosorbent assay [ELISA], Luminex, Meso Scale Discovery [MSD], time-resolved fluorescence resonance energy transfer [TR-FRET], cytometric bead array [CBA], AlphaLISA, and FirePlex). Through experimental data analysis, several assay features were compared, including sensitivity, dynamic range, and robustness. Our studies reveal that MSD has the best sensitivity in the low detection limit and the broadest dynamic range, while CBA and Luminex also demonstrate superior performance in the sensitivity and dynamic range. Additional aspects of these technologies, including assay principles, formats, throughputs, robustness, costs, and multiplexing capabilities, were also reviewed and compared. Combining all these features, our comparison highlights MSD as the most sensitive technology, while CBA is the most suitable one for cytokine high-throughput screening with multiplexing capability. Along with perspectives on new technology development in the field, this report aims to help readers understand these technologies and select the proper one for specific applications.

Discovery of First-in-Class Protein Arginine Methyltransferase 5 (PRMT5) Degraders

The aberrant expression of protein arginine methyltransferase 5 (PRMT5) has been associated with multiple cancers. Using the proteolysis targeting chimera technology, we discovered a first-in-class PRMT5 degrader 15 (MS4322). Here, we report the design, synthesis, and characterization of compound 15 and two structurally similar controls 17 (MS4370) and 21 (MS4369), with impaired binding to the von Hippel-Lindau E3 ligase and PRMT5, respectively. Compound 15, but not 17 and 21, effectively reduced the PRMT5 protein level in MCF-7 cells. Our mechanism studies indicate that compound 15 degraded PRMT5 in an E3 ligase- and proteasome-dependent manner. Compound 15 also effectively reduced the PRMT5 protein level and inhibited growth in multiple cancer cell lines. Moreover, compound 15 was highly selective for PRMT5 in a global proteomic study and exhibited good plasma exposure in mice. Collectively, compound 15 and its two controls 17 and 21 are valuable chemical tools for exploring the PRMT5 functions in health and disease.

Histone H4R3 symmetric di-methylation by Prmt5 protects against cardiac hypertrophy via regulation of Filip1L/β-catenin

BACKGROUND AND PURPOSE

Although histone lysine methylation has been extensively studied for their participation in pathological cardiac hypertrophy, the potential regulatory role of histone arginine methylation remains to be elucidated. The present study focused on H4R3 symmetric di-methylation (H4R3me2s) induced by protein arginine methyltransferase 5 (Prmt5), and explored its epigenetic regulation and underlying mechanisms in cardiomyocyte hypertrophy.

METHODS AND RESULTS

1. The expressions of Prmt5 and H4R3me2s were suppressed in cardiac hypertrophy models in vivo and in vitro; 2. Prmt5 silencing or its inhibitor EPZ, or knockdown of cooperator of Prmt5 (Copr5) to disrupt H4R3me2s, facilitated cardiomyocyte hypertrophy, whereas overexpression of wild type Prmt5 rather than the inactive mutant protected cardiomyocytes against hypertrophy; 3. ChIP-sequence analysis identified Filip1L as a target gene of Prmt5-induced H4R3me2s; 4. Knockdown or inhibition of Prmt5 impaired Filip1L transcription and subsequently prevented β-catenin degradation, thus augmenting cardiomyocyte hypertrophy.

CONCLUSIONS

The present study reveals that Prmt5-induced H4R3me2s ameliorates cardiomyocyte hypertrophy by transcriptional upregulation of Filip1L and subsequent enhancement of β-catenin degradation. Deficiency of Prmt5 and the resulting suppression of H4R3me2s might facilitate the development of pathological cardiac hypertrophy. Prmt5 might serve as a key epigenetic regulator in pathological cardiac hypertrophy.

Modulating the modulators: regulation of protein arginine methyltransferases by post-translational modifications

The therapeutic potential of targeting protein arginine methyltransferases (PRMTs) is inextricably linked to their key roles in various cellular functions, including splicing, proliferation, cell cycle regulation, differentiation, and DNA damage signaling. Unsurprisingly, the development of inhibitors against these enzymes has become a rapidly expanding research area. However, effective targeting of PRMTs requires a deeper understanding of the mechanistic details behind their regulation at multiple levels, involving those mechanisms that alter their activity, interactions, and localization. Recently, post-translational modifications (PTMs) of PRMTs have emerged as another crucial aspect of this regulation. Here, we review the regulatory role of PTMs in the activity and function of PRMTs, with emphasis on the contribution of these PTMs to pathological states, such as cancer.

Small molecule inhibitors in pancreatic cancer

Pancreatic cancer (PC), with a 5 year survival of <7%, is one of the most fatal of all human cancers. The highly aggressive and metastatic character of this disease poses a challenge that current therapies are failing, despite significant efforts, to meet. This review examines the current status of the 35 small molecule inhibitors targeting pancreatic cancer in clinical trials and the >50 currently under investigation. These compounds inhibit biological targets spanning protein kinases, STAT3, BET, HDACs and Bcl-2 family proteins. Unsurprisingly, protein kinase inhibitors are overrepresented. Some trials show promise; a phase I combination trial of vorinostat 11 and capecitabine 17 gave a median overall survival (MoS) of 13 months and a phase II study of pazopanib 15 showed a MoS of 25 months. The current standard of care for metastatic pancreatic ductal adenocarcinoma, fluorouracil/folic acid (5-FU, Adrucil®), and gemcitabine (GEMZAR®) afforded a MoS of 23 and 23.6 months (EPAC-3 study), respectively. In patients who can tolerate the FOLFIRINOX regime, this is becoming the standard of treatment with a MoS of 11.1 months. Clinical study progress has been slow with limited improvement in patient survival relative to gemcitabine 1 monotherapy. A major cause of low PC survival is the late stage of diagnosis, occurring in patients who consider typical early stage warning signs of aches and pains normal. The selection of patients with specific disease phenotypes, the use of improved efficient drug combinations, the identification of biomarkers to specific cancer subtypes and more effective designs of investigation have improved outcomes. To move beyond the current dire condition and paucity of PC treatment options, determination of the best regimes and new treatment options is a challenge that must be met. The reasons for poor PC prognosis have remained largely unchanged for 20 years. This is arguably a consequence of significant changes in the drug discovery landscape, and the increasing pressure on academia to deliver short term 'media' friendly short-term news 'bites'. PC research sits at a pivotal point. Perhaps the greatest challenge is enacting a culture change that recognises that major breakthroughs are a result of blue sky, truly innovative and curiosity driven research.

Discovery of Novel PRMT5 Inhibitors by Virtual Screening and Biological Evaluations

As an important epigenetics related enzyme, protein arginine methyltransferase 5 (PRMT5) has been confirmed as an anticancer therapeutic target in recent years. Among all the reported PRMT5 inhibitors, two small molecules (GSK-3326595 and JNJ-64619178) are currently being assessed in clinical trial. In this study, 40 PRMT5 inhibitor candidates were purchased from SPECS database supplier according to the pharmacophore and molecular docking based virtual screening results. Alpha linked immunosorbent assay (LISA) methylation assay was performed to test their inhibitory activity against PRMT5. The in vitro enzymatic assay results indicated that four compounds (2, 4, 10 and 37) showed PRMT5 inhibitory activity, while 4 and 10 displayed the most potent activity with IC₅₀ values of 8.1 ± 1.1 and 6.5 ± 0.6 µM, respectively. The inhibitory activity results of 20 extra analogs of 4 further confirmed the potency of this scaffold. As expected, compounds 4 and 10 exhibited moderate anti-proliferative activity against mantle cell lymphoma Jeko-1 and leukemia cell MV4-11. Besides, Western blot assay results showed that 4 could reduce the H4R3me2s level in a dose-dependent manner, indicating that it could inhibit the activity of PRMT5 in cellular context. Detailed interactions between 4 and PRMT5 were characterized by binding mode analysis through molecular docking. The compounds discovered in this study will inspire medicinal chemists to further explore this series of PRMT5 inhibitors.

Discovery of new potent protein arginine methyltransferase 5 (PRMT5) inhibitors by assembly of key pharmacophores from known inhibitors

Protein arginine methyltransferase 5 (PRMT5) is an epigenetics related enzyme that has been validated as a promising therapeutic target for human cancer. Up to now, two small molecule PRMT5 inhibitors has been put into phase I clinical trial. In the present study, a series of candidate molecules were designed by combining key pharmacophores of formerly reported PRMT5 inhibitors. The in vitro PRMT5 inhibitory testing of compound 4b14 revealed an IC₅₀ of 2.71 μM, exhibiting high selectivity over PRMT1 and PRMT4 (>70-fold selective). As expected, 4b14 exhibited potent anti-proliferative activity against a panel of leukemia and lymphoma cells, including MV4-11, Pfeiffer, SU-DHL-4 and KARPAS-422. Besides, 4b14 showed significant cell cycle arrest and apoptosis-inducing effects, as well as reduced the cellular symmetric arginine dimethylation level of SmD3 protein. Finally, affinity profiling analysis indicated that hydrophobic interactions, π-π stacking and cation-π actions made the major contributions to the overall binding affinity. This scaffold provides a new chemical template for further development of better lead compounds targeting PRMT5.