Adapting AlphaLISA high throughput screen to discover a novel small-molecule inhibitor targeting protein arginine methyltransferase 5 in pancreatic and colorectal cancers

The Application of Ejaculate-Based Shotgun Proteomics for Male Infertility Screening

Problems with the male reproductive system are of both medical and social significance. As a rule, spermatozoa and seminal plasma proteomes are investigated separately to assess sperm quality. The current study aimed to compare ejaculate proteomes with spermatozoa and seminal plasma protein profiles regarding the identification of proteins related to fertility scores. A total of 1779, 715, and 2163 proteins were identified in the ejaculate, seminal plasma, and spermatozoa, respectively. Among these datasets, 472 proteins were shared. GO enrichment analysis of the common proteins enabled us to distinguish biological processes such as single fertilization (GO:0007338), spermatid development (GO:0007286), and cell motility (GO:0048870). Among the abundant terms for GO cellular components, zona pellucida receptor complex, sperm fibrous sheath, and outer dense fiber were revealed. Overall, we identified 139 testis-specific proteins. For these proteins, PPI networks that are common in ejaculate, spermatozoa, and seminal plasma were related to the following GO biological processes: cilium movement (GO:0003341), microtubule-based movement (GO:0007018), and sperm motility (GO:0097722). For ejaculate and spermatozoa, they shared 15 common testis-specific proteins with spermatogenesis (GO:0007283) and male gamete generation (GO:0048232). Therefore, we speculated that ejaculate-based proteomics could yield new insights into the peculiar reproductive physiology and spermatozoa function of men and potentially serve as an explanation for male infertility screening.

Genetic Alterations of NF-κB and Its Regulators: A Rich Platform to Advance Colorectal Cancer Diagnosis and Treatment

Colorectal cancer (CRC) is the third leading cause of cancer mortality in the United States, with an estimated 52,000 deaths in 2023. Though significant progress has been made in both diagnosis and treatment of CRC in recent years, genetic heterogeneity of CRC-the culprit for possible CRC relapse and drug resistance, is still an insurmountable challenge. Thus, developing more effective therapeutics to overcome this challenge in new CRC treatment strategies is imperative. Genetic and epigenetic changes are well recognized to be responsible for the stepwise development of CRC malignancy. In this review, we focus on detailed genetic alteration information about the nuclear factor (NF)-κB signaling, including both NF-κB family members, and their regulators, such as protein arginine methyltransferase 5 (PRMT5), and outer dynein arm docking complex subunit 2 (ODAD2, also named armadillo repeat-containing 4, ARMC4), etc., in CRC patients. Moreover, we provide deep insight into different CRC research models, with a particular focus on patient-derived xenografts (PDX) and organoid models, and their potential applications in CRC research. Genetic alterations on NF-κB signaling components are estimated to be more than 50% of the overall genetic changes identified in CRC patients collected by cBioportal for Cancer Genomics; thus, emphasizing its paramount importance in CRC progression. Consequently, various genetic alterations on NF-κB signaling may hold great promise for novel therapeutic development in CRC. Future endeavors may focus on utilizing CRC models (e.g., PDX or organoids, or isogenic human embryonic stem cell (hESC)-derived colonic cells, or human pluripotent stem cells (hPSC)-derived colonic organoids, etc.) to further uncover the underpinning mechanism of these genetic alterations in NF-κB signaling in CRC progression. Moreover, establishing platforms for drug discovery in dishes, and developing Biobanks, etc., may further pave the way for the development of innovative personalized medicine to treat CRC in the future.

Phase 1 Study of JNJ-64619178, a Protein Arginine Methyltransferase 5 Inhibitor, in Advanced Solid Tumors

PURPOSE

In this first-in-human, Phase 1, open-label, multicenter study, we evaluated JNJ-64619178, a selective and potent PRMT5 inhibitor, in patients with advanced malignant solid tumors or non-Hodgkin lymphomas (NHL). The primary objective was to evaluate the safety and to identify a recommended Phase 2 dose (RP2D) of JNJ-64619178.

PATIENTS AND METHODS

Adult patients with treatment-refractory advanced solid tumors or NHL and measurable disease received escalating doses of JNJ-64619178 following two schedules (Schedule A: 14 days on/7 days off; Schedule B: every day on a 21-day cycle). Safety, pharmacokinetics (PK), pharmacodynamics (PD), and clinical activity were evaluated.

RESULTS

Ninety patients received JNJ-64619178. Thrombocytopenia was identified as the only dose-limiting toxicity. JNJ-64619178 showed dose-proportional PK and robust target engagement, as measured by plasma symmetric dimethylarginine, across all dose levels. The objective response rate was 5.6% (5 of 90). Patients with adenoid cystic carcinoma (ACC) had an ORR of 11.5% (3 of 26) and a median progression-free survival of 19.1 months.

CONCLUSIONS

JNJ-64619178 demonstrated manageable dose-dependent toxicity and preliminary evidence of antitumor activity in ACC and other tumor types. Plasma exposure was dose dependent, and target inhibition was maintained with intermittent and continuous dosing. On the basis of safety, clinical activity, PK, and PD findings, two provisional RP2Ds were selected: 1.5 mg intermittently and 1.0 mg once daily. Aside from ACC, clinical benefit was limited, and biomarkers to enrich for responsiveness to PRMT5 inhibition will be needed for further development.

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.

Design, Synthesis and Biological Evaluation of Novel and Potent Protein Arginine Methyltransferases 5 Inhibitors for Cancer Therapy

Protein arginine methyltransferases 5 (PRMT5) is a clinically promising epigenetic target that is upregulated in a variety of tumors. Currently, there are several PRMT5 inhibitors under preclinical or clinical development, however the established clinical inhibitors show favorable toxicity. Thus, it remains an unmet need to discover novel and structurally diverse PRMT5 inhibitors with characterized therapeutic utility. Herein, a series of tetrahydroisoquinoline (THIQ) derivatives were designed and synthesized as PRMT5 inhibitors using GSK-3326595 as the lead compound. Among them, compound 20 (IC₅₀: 4.2 nM) exhibits more potent PRMT5 inhibitory activity than GSK-3326595 (IC₅₀: 9.2 nM). In addition, compound 20 shows high anti-proliferative effects on MV-4-11 and MDA-MB-468 tumor cells and low cytotoxicity on AML-12 hepatocytes. Furthermore, compound 20 possesses acceptable pharmacokinetic profiles and displays considerable in vivo antitumor efficacy in a MV-4-11 xenograft model. Taken together, compound 20 is an antitumor compound worthy of further study.

Design and evaluation of achiral, non-atropisomeric 4-(aminomethyl)phthalazin-1(2H)-one derivatives as novel PRMT5/MTA inhibitors

MRTX1719 is an inhibitor of the PRMT5/MTA complex and recently entered clinical trials for the treatment of MTAP-deleted cancers. MRTX1719 is a class 3 atropisomeric compound that requires a chiral synthesis or a chiral separation step in its preparation. Here, we report the SAR and medicinal chemistry design strategy, supported by structural insights from X-ray crystallography, to discover a class 1 atropisomeric compound from the same series that does not require a chiral synthesis or a chiral separation step in its preparation.

The Pivotal Role of NF-kB in the Pathogenesis and Therapeutics of Alzheimer’s Disease

Alzheimer’s Disease (AD) is the most common neurodegenerative disease worldwide, with a high prevalence that is expected to double every 20 years. Besides the formation of Aβ plaques and neurofibrillary tangles, neuroinflammation is one the major phenotypes that worsens AD progression. Indeed, the nuclear factor-κB (NF-κB) is a well-established inflammatory transcription factor that fuels neurodegeneration. Thus, in this review, we provide an overview of the NF-κB role in the pathogenesis of AD, including its interaction with various molecular factors in AD mice models, neurons, and glial cells. Some of these cell types and molecules include reactive microglia and astrocytes, β-secretase, APOE, glutamate, miRNA, and tau protein, among others. Due to the multifactorial nature of AD development and the failure of many drugs designed to dampen AD progression, the pursuit of novel targets for AD therapeutics, including the NF-κB signaling pathway, is rising. Herein, we provide a synopsis of the drug development landscape for AD treatment, offering the perspective that NF-κB inhibitors may generate widespread interest in AD research in the future. Ultimately, the additional investigation of compounds and small molecules that target NF-κB signaling and the complete understanding of NF-κB mechanistic activation in different cell types will broaden and provide more therapeutic options for AD patients.

Integration of Transcriptomics and Metabolomics Reveals the Antitumor Mechanism Underlying Tadalafil in Colorectal Cancer

The potential role of tadalafil, a PDE5 inhibitor, in anticancer activity and prolonged survival has been proposed. However, the systematic effects of tadalafil in colorectal cancer were not fully understood. In this study, we assessed the anti-tumor activity of tadalafil in human colorectal cancer cells. A systematic perspective of the tadalafil-induced anti-tumor mechanism was provided by the integration of transcriptomics and metabolomics. We found that differentially expressed genes (DEGs) were mainly involved in microRNAs in cancer, purine metabolism, glycosphingolipid biosynthesis, arginine biosynthesis, and amino acid metabolism. Amino acid metabolism, especially alanine, aspartate, and glutamate metabolism was the most of the differentially accumulated metabolites (DAMs) through the analysis of metabolomics. The conjoint analysis of DEGs and DAMs presented that they were also mainly involved in alanine, aspartate, and glutamate metabolism. Amino acid metabolism-related genes, GPT, GGT5, and TAT, were significantly decreased after tadalafil treatment. In particular, the disturbance of alanine, aspartate, and glutamate metabolism may be the explanation for the major mechanism resulting from tadalafil anti-tumor activity.

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.

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.

Clinical and Preclinical Outcomes of Combining Targeted Therapy With Radiotherapy

In the era of precision medicine, radiation medicine is currently focused on the precise delivery of highly conformal radiation treatments. However, the tremendous developments in targeted therapy are yet to fulfill their full promise and arguably have the potential to dramatically enhance the radiation therapeutic ratio. The increased ability to molecularly profile tumors both at diagnosis and at relapse and the co-incident progress in the field of radiogenomics could potentially pave the way for a more personalized approach to radiation treatment in contrast to the current ‘‘one size fits all’’ paradigm. Few clinical trials to date have shown an improved clinical outcome when combining targeted agents with radiation therapy, however, most have failed to show benefit, which is arguably due to limited preclinical data. Several key molecular pathways could theoretically enhance therapeutic effect of radiation when rationally targeted either by directly enhancing tumor cell kill or indirectly through the abscopal effect of radiation when combined with novel immunotherapies. The timing of combining molecular targeted therapy with radiation is also important to determine and could greatly affect the outcome depending on which pathway is being inhibited.

The Structure and Functions of PRMT5 in Human Diseases

Since the discovery of protein arginine methyltransferase 5 (PRMT5) and the resolution of its structure, an increasing number of papers have investigated and delineated the structural and functional role of PRMT5 in diseased conditions. PRMT5 is a type II arginine methyltransferase that catalyzes symmetric dimethylation marks on histones and non-histone proteins. From gene regulation to human development, PRMT5 is involved in many vital biological functions in humans. The role of PRMT5 in various cancers is particularly well-documented, and investigations into the development of better PRMT5 inhibitors to promote tumor regression are ongoing. Notably, emerging studies have demonstrated the pathological contribution of PRMT5 in the progression of inflammatory diseases, such as diabetes, cardiovascular diseases, and neurodegenerative disorders. However, more research in this direction is needed. Herein, we critically review the position of PRMT5 in current literature, including its structure, mechanism of action, regulation, physiological and pathological relevance, and therapeutic strategies.

Acquired resistance to PRMT5 inhibition induces concomitant collateral sensitivity to paclitaxel

Epigenetic regulators play key roles in cancer and are increasingly being targeted for treatment. However, for many, little is known about mechanisms of resistance to the inhibition of these regulators. We have generated a model of resistance to inhibitors of protein arginine methyltransferase 5 (PRMT5). This study was conducted in Kras ^G12D;Tp53-null lung adenocarcinoma (LUAD) cell lines. Resistance to PRMT5 inhibitors (PRMT5i) arose rapidly, and barcoding experiments showed that this resulted from a drug-induced transcriptional state switch, not selection of a preexisting population. This resistant state is both stable and conserved across variants arising from distinct LUAD lines. Moreover, it brought with it vulnerabilities to other chemotherapeutics, especially the taxane paclitaxel. This paclitaxel sensitivity depended on the presence of stathmin 2 (STMN2), a microtubule regulator that is specifically expressed in the resistant state. Remarkably, STMN2 was also essential for resistance to PRMT5 inhibition. Thus, a single gene is required for both acquisition of resistance to PRMT5i and collateral sensitivity to paclitaxel in our LUAD cells. Accordingly, the combination of PRMT5i and paclitaxel yielded potent and synergistic killing of the murine LUAD cells. Importantly, the synergy between PRMT5i and paclitaxel also extended to human cancer cell lines. Finally, analysis of The Cancer Genome Atlas patient data showed that high STMN2 levels correlate with complete regression of tumors in response to taxane treatment. Collectively, this study reveals a recurring mechanism of PRMT5i resistance in LUAD and identifies collateral sensitivities that have potential clinical relevance.

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.

The Discovery of Two Novel Classes of 5,5-Bicyclic Nucleoside-Derived PRMT5 Inhibitors for the Treatment of Cancer

Protein arginine methyltransferase 5 (PRMT5) is a type II arginine methyltransferase that catalyzes the post-translational symmetric dimethylation of protein substrates. PRMT5 plays a critical role in regulating biological processes including transcription, cell cycle progression, RNA splicing, and DNA repair. As such, dysregulation of PRMT5 activity is implicated in the development and progression of multiple cancers and is a target of growing clinical interest. Described herein are the structure-based drug designs, robust synthetic efforts, and lead optimization strategies toward the identification of two novel 5,5-fused bicyclic nucleoside-derived classes of potent and efficacious PRMT5 inhibitors. Utilization of compound docking and strain energy calculations inspired novel designs, and the development of flexible synthetic approaches enabled access to complex chemotypes with five contiguous stereocenters. Additional efforts in balancing bioavailability, solubility, potency, and CYP3A4 inhibition led to the identification of diverse lead compounds with favorable profiles, promising in vivo activity, and low human dose projections.

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.

Protein arginine methyltransferase 5: a potential cancer therapeutic target

BACKGROUND

PRMT5 is a type II protein arginine methyltransferase that methylates histone or non-histone proteins. Arginine methylation by PRMT5 has been implicated in gene transcription, ribosome biogenesis, RNA transport, pre-mRNA splicing and signal transduction. High expression of PRMT5 has been observed in various cancers and PRMT5 overexpression has been reported to improve cancer cell survival, proliferation, migration and metabolism and to inhibit cancer cell apoptosis. In addition, PRMT5 has been found to be required for cancer stem cell survival, self-renewal and differentiation. Several microRNAs have been shown to regulate PRMT5 expression. As PRMT5 has oncogene-like properties, several PRMT5 inhibitors have been used to explore their efficacy as potential drugs for different types of cancer, and three of them are now being tested in clinical trials.

CONCLUSIONS

In this review, we summarize current knowledge on the role of PRMT5 in cancer development and progression, including its functions and underlying mechanisms. In addition, we highlight the rapid development of PRMT5 inhibitors and summarize ongoing clinical trials for cancer therapy. By affecting both tumor cells and the tumor microenvironment, PRMT5 inhibitors may serve as effective anti-cancer agents, especially when combined with immune therapies.

Phosphorylation of the Regulators, a Complex Facet of NF-κB Signaling in Cancer

The nuclear factor kappa B (NF-κB) is a ubiquitous transcription factor central to inflammation and various malignant diseases in humans. The regulation of NF-κB can be influenced by a myriad of post-translational modifications (PTMs), including phosphorylation, one of the most popular PTM formats in NF-κB signaling. The regulation by phosphorylation modification is not limited to NF-κB subunits, but it also encompasses the diverse regulators of NF-κB signaling. The differential site-specific phosphorylation of NF-κB itself or some NF-κB regulators can result in dysregulated NF-κB signaling, often culminating in events that induce cancer progression and other hyper NF-κB related diseases, such as inflammation, cardiovascular diseases, diabetes, as well as neurodegenerative diseases, etc. In this review, we discuss the regulatory role of phosphorylation in NF-κB signaling and the mechanisms through which they aid cancer progression. Additionally, we highlight some of the known and novel NF-κB regulators that are frequently subjected to phosphorylation. Finally, we provide some future perspectives in terms of drug development to target kinases that regulate NF-κB signaling for cancer therapeutic purposes.

EPZ015666, a selective protein arginine methyltransferase 5 (PRMT5) inhibitor with an antitumour effect in retinoblastoma

Retinoblastoma (RB) is the most common intraocular malignant tumour in infants, and chemotherapy has been the primary therapy method in recent years. PRMT5 is an important member of the protein arginine methyltransferase family, which plays an important role in various tumours. Our study showed that PRMT5 was overexpressed in retinoblastoma and played an important role in retinoblastoma cell growth. EPZ015666 is a novel PRMT5 inhibitor, and we found that it inhibited retinoblastoma cell proliferation and led to cell cycle arrest at the G1 phase. At the same time, EPZ015666 regulated cell cycle related protein (P53, P21, P27, CDK2) expression. In brief, our study showed that PRMT5 promoted retinoblastoma growth, the PRMT5 inhibitor EPZ015666 inhibited retinoblastoma in vitro by regulating P53-P21/P27-CDK2 signaling pathways and slowed retinoblastoma growth in a xenograft model.

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.

Regulation of a PRMT5/NF-κB Axis by Phosphorylation of PRMT5 at Serine 15 in Colorectal Cancer

The overexpression of PRMT5 is highly correlated to poor clinical outcomes for colorectal cancer (CRC) patients. Importantly, our previous work demonstrated that PRMT5 overexpression could substantially augment activation of the nuclear factor kappa B (NF-κB) via methylation of arginine 30 (R30) on its p65 subunit, while knockdown of PRMT5 showed the opposite effect. However, the precise mechanisms governing this PRMT5/NF-κB axis are still largely unknown. Here, we report a novel finding that PRMT5 is phosphorylated on serine 15 (S15) in response to interleukin-1β (IL-1β) stimulation. Interestingly, we identified for the first time that the oncogenic kinase, PKCι could catalyze this phosphorylation event. Overexpression of the serine-to-alanine mutant of PRMT5 (S15A), in either HEK293 cells or CRC cells HT29, DLD1, and HCT116 attenuated NF-κB transactivation compared to WT-PRMT5, confirming that S15 phosphorylation is critical for the activation of NF-κB by PRMT5. Furthermore, the S15A mutant when compared to WT-PRMT5, could downregulate a subset of IL-1β-inducible NF-κB-target genes which correlated with attenuated promoter occupancy of p65 at its target genes. Additionally, the S15A mutant reduced IL-1β-induced methyltransferase activity of PRMT5 and disrupted the interaction of PRMT5 with p65. Furthermore, our data indicate that blockade of PKCι-regulated PRMT5-mediated activation of NF-κB was likely through phosphorylation of PRMT5 at S15. Finally, inhibition of PKCι or overexpression of the S15A mutant attenuated the growth, migratory, and colony-forming abilities of CRC cells compared to the WT-PRMT5. Collectively, we have identified a novel PKCι/PRMT5/NF-κB signaling axis, suggesting that pharmacological disruption of this pivotal axis could serve as the basis for new anti-cancer therapeutics.

Protein Expression Profiling Identifies Key Proteins and Pathways Involved in Growth Inhibitory Effects Exerted by Guggulsterone in Human Colorectal Cancer Cells

Colorectal cancer (CRC) is a leading killer cancer worldwide and one of the most common malignancies with increasing incidences of mortality. Guggulsterone (GS) is a plant sterol used for treatment of various ailments such as obesity, hyperlipidemia, diabetes, and arthritis. In the current study, anti-cancer effects of GS in human colorectal cancer cell line HCT 116 was tested, potential targets identified using mass spectrometry-based label-free shotgun proteomics approach and key pathways validated by proteome profiler antibody arrays. Comprehensive proteomic profiling identified 14 proteins as significantly dysregulated. Proteins involved in cell proliferation/migration, tumorigenesis, cell growth, metabolism, and DNA replication were downregulated while the protein with functional role in exocytosis/tumor suppression was found to be upregulated. Our study evidenced that GS treatment altered expression of Bcl-2 mediated the mitochondrial release of cytochrome c which triggered the formation of apoptosome as well as activation of caspase-3/7 leading to death of HCT 116 cells via intrinsic apoptosis pathway. GS treatment also induced expression of p53 protein while p21 expression was unaltered with no cell cycle arrest. In addition, GS was found to inhibit NF-kB signaling in colon cancer cells by quelling the expression of its regulated gene products Bcl-2, cIAP-1, and survivin.

PRMTs and miRNAs: functional cooperation in cancer and beyond

Epigenetic modulators play pivotal roles in directing gene expression for the maintenance of normal cellular functions. However, when these modulators are aberrantly regulated, this can result in a variety of disease states, including cancer. One class of epigenetic regulators, protein arginine methyltransferases (PRMTs), have been shown to play critical roles in disease through methylation of arginine residues (R) on histone or non-histone proteins. Quite different from PRMTs, microRNAs (miRNAs) belong to the family of modulators known as noncoding RNAs (ncRNA) that act to regulate gene expression via RNA-mediated gene silencing. Importantly, miRNAs are frequently dysregulated and contribute to the progression of cancer and other conditions, including neurological and cardiovascular diseases. Recently, numerous studies have shown that miRNAs and other epigenetic enzymes can co-regulate each other. This review highlights multiple nodes of interaction between miRNAs and PRMTs and also discusses how this interplay might open up promising opportunities for drug development for the treatment of cancer and other diseases.

Role of protein arginine methyltransferase 5 in human cancers

Protein arginine methyltransferases (PRMTs) play important roles in protein methylation. PRMT5 is the major type II arginine methyltransferase that catalyzes the transfer of two methyl groups symmetrically to the arginine residues of either histone or non-histone proteins. In recent years, increasing evidence has shown that PRMT5, as an oncogene, plays an indispensable regulatory role in the pathological progression of several human cancers by promoting the proliferation, invasion, and migration of cancer cells. PRMT5 is overexpressed in many malignant tumors and plays an important role in the occurrence and development of cancer, which suggests that PRMT5 may become a potential biomarker or therapeutic target of cancer. This article reviews the biological function, mechanism, and clinical significance of PRMT5 in tumorigenesis.

Inhibiting Arginine Methylation as a Tool to Investigate Cross-Talk with Methylation and Acetylation Post-Translational Modifications in a Glioblastoma Cell Line

Glioblastomas (GBM) are the most common grade 4 brain tumours; patients have very poor prognosis with an average survival of 15 months after diagnosis. Novel research lines have begun to explore aberrant protein arginine methylation (ArgMe) as a possible therapeutic target in GBM and ArgMe inhibitors are currently in clinical trials. Enzymes known as protein arginine methyltransferases (PRMT1-9) can lead to mono- or di-ArgMe, and in the latter case symmetric or asymmetric dimethylation (SDMA and ADMA, respectively). Using the most common GBM cell line, we have profiled the expression of PRMTs, used ArgMe inhibitors as tools to investigate post-translational modifications cross-talk and measured the effect of ArgMe inhibitors on cell viability. We have identified novel SDMA events upon inhibition of ADMA in GBM cells and spheroids. We have observed cross-talk between ADMA and lysine acetylation in GBM cells and platelets. Treatment of GBM cells with furamidine, a PRMT1 inhibitor, reduces cell viability in 2D and 3D models. These data provide new molecular understanding of a disease with unmet clinical needs.

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

The protein arginine methyltransferase (PRMT) family of enzymes comprises nine family members in mammals. They catalyze arginine methylation, either monomethylation or symmetric/asymmetric dimethylation of histone and non-histone proteins. PRMT methylation of its substrate proteins modulates cellular processes such as signal transduction, transcription, and mRNA splicing. Recent studies have linked overexpression of PRMT5, a member of the PRMT superfamily, to oncogenesis, making it a potential target for cancer therapy. In this study, we developed a highly sensitive (Z' score = 0.7) robotic high throughput screening (HTS) platform to discover small molecule inhibitors of PRMT5 by adapting the AlphaLISA™ technology. Using biotinylated histone H4 as a substrate, and S-adenosyl-l-methionine as a methyl donor, PRMT5 symmetrically dimethylated H4 at arginine (R) 3. Highly specific acceptor beads for symmetrically dimethylated H4R3 and streptavidin-coated donor beads bound the substrate, emitting a signal that is proportional to the methyltransferase activity. Using this powerful approach, we identified specific PRMT5 inhibitors P1608K04 and P1618J22, and further validated their efficacy and specificity for inhibiting PRMT5. Importantly, these two compounds exhibited much more potent efficacy than the commercial PRMT5 inhibitor EPZ015666 in both pancreatic and colorectal cancer cells. Overall, our work highlights a novel, powerful, and sensitive approach to identify specific PRMT5 inhibitors. The general principle of this HTS screening method can not only be applied to PRMT5 and the PRMT superfamily, but may also be extended to other epigenetic targets. This approach allows us to identify compounds that inhibit the activity of their respective targets, and screening hits like P1608K04 and P1618J22 may serve as the basis for novel drug development to treat cancer and/or other diseases.

Combination therapy versus gemcitabine monotherapy in the treatment of elderly pancreatic cancer: a meta-analysis of randomized controlled trials

Purpose

We aimed to compare the efficacy of combination therapy versus gemcitabine monotherapy in the treatment of elderly pancreatic cancer (PC) by using a meta-analysis.

Materials and methods

Databases were searched to identify relevant clinical trials. Hazard ratios (HRs) were used to estimate overall survival (OS) and progression-free survival (PFS). Statistical analyses were conducted by using Comprehensive Meta Analysis software (version 2.0).

Results

=0.009) in comparison with gemcitabine alone. No publication bias was detected by Begg's and Egger's tests for OS.

Conclusion

The findings of this study suggest that combined chemotherapy, but not for gemcitabine plus targeted agents, could be recommended for elderly PC patients due to its survival benefits. Further studies are still needed to assess the treatment tolerance of combination chemotherapy in these patient populations.