The Discovery of Selective Protein Arginine Methyltransferase 5 Inhibitors in the Management of ß-Thalassemia through Computational Methods.

ß-Thalassemia is an inherited genetic disorder associated with ß-globin chain synthesis, which ultimately becomes anemia. Adenosine-2,3-dialdehyde, by inhibiting arginine methyl transferase 5 (PRMT5), can induce fetal hemoglobin (HbF) levels. Hence, the materialization of PRMT5 inhibitors is considered a promising therapy in the management of ß-thalassemia. This study conducted a virtual screening of certain compounds similar to 5'-deoxy-5'methyladenosine (3XV) using the PubChem database. The top 10 compounds were chosen based on the best docking scores, while their interactions with the PRMT5 active site were analyzed. Further, the top two compounds demonstrating the lowest binding energy were subjected to drug-likeness analysis and pharmacokinetic property predictions, followed by molecular dynamics simulation studies. Based on the molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) score and molecular interactions, (3R,4S)-2-(6-aminopurin-9-yl)-5-[(4-ethylcyclohexyl)sulfanylmethyl]oxolane-3,4-diol (TOP1) and 2-(6-Aminopurin-9-yl)-5-[(6-aminopurin-9-yl)methylsulfanylmethyl]oxolane-3,4-diol (TOP2) were identified as potential hit compounds, while TOP1 exhibited higher binding affinity and stabler binding capabilities than TOP2 during molecular dynamics simulation (MDS) analysis. Taken together, the outcomes of our study could aid researchers in identifying promising PRMT5 inhibitors. Moreover, further investigations through in vivo and in vitro experiments would unquestionably confirm that this compound could be employed as a therapeutic drug in the management of ß-thalassemia.

The interplay mechanism between IDH mutation, MGMT-promoter methylation, and PRMT5 activity in the progression of grade 4 astrocytoma: unraveling the complex triad theory.

Background: The dysregulation of Isocitrate dehydrogenase (IDH) and the subsequent production of 2-Hydroxyglutrate (2HG) may alter the expression of epigenetic proteins in Grade 4 astrocytoma. The interplay mechanism between IDH, O-6-methylguanine-DNA methyltransferase (MGMT)-promoter methylation, and protein methyltransferase proteins-5 (PRMT5) activity, with tumor progression has never been described. Methods: A retrospective cohort of 34 patients with G4 astrocytoma is classified into IDH-mutant and IDH-wildtype tumors. Both groups were tested for MGMT-promoter methylation and PRMT5 through methylation-specific and gene expression PCR analysis. Inter-cohort statistical significance was evaluated. Results: Both IDH-mutant WHO grade 4 astrocytomas (n = 22, 64.7%) and IDH-wildtype glioblastomas (n = 12, 35.3%) had upregulated PRMT5 gene expression except in one case. Out of the 22 IDH-mutant tumors, 10 (45.5%) tumors showed MGMT-promoter methylation and 12 (54.5%) tumors had unmethylated MGMT. All IDH-wildtype tumors had unmethylated MGMT. There was a statistically significant relationship between MGMT-promoter methylation and IDH in G4 astrocytoma (p-value = 0.006). Statistically significant differences in progression-free survival (PFS) were also observed among all G4 astrocytomas that expressed PRMT5 and received either temozolomide (TMZ) or TMZ plus other chemotherapies, regardless of their IDH or MGMT-methylation status (p-value=0.0014). Specifically, IDH-mutant tumors that had upregulated PRMT5 activity and MGMT-promoter methylation, who received only TMZ, have exhibited longer PFS. Conclusions: The relationship between PRMT5, MGMT-promoter, and IDH is not tri-directional. However, accumulation of D2-hydroxyglutarate (2-HG), which partially activates 2-OG-dependent deoxygenase, may not affect their activities. In IDH-wildtype glioblastomas, the 2HG-2OG pathway is typically inactive, leading to PRMT5 upregulation. TMZ alone, compared to TMZ-plus, can increase PFS in upregulated PRMT5 tumors. Thus, using a PRMT5 inhibitor in G4 astrocytomas may help in tumor regression.

Regulation of RORα Stability through PRMT5-Dependent Symmetric Dimethylation.

Retinoic acid receptor-related orphan receptor alpha (RORα), a candidate tumor suppressor, is prevalently downregulated or lost in malignant breast cancer cells. However, the mechanisms of how RORα expression is regulated in breast epithelial cells remain incompletely understood. Protein arginine N-methyltransferase 5 (PRMT5), a type II methyltransferase catalyzing the symmetric methylation of the amino acid arginine in target proteins, was reported to regulate protein stability. To study whether and how PRMT5 regulates RORα, we examined the direct interaction between RORα and PRMT5 by immunoprecipitation and GST pull-down assays. The results showed that PRMT5 directly bound to RORα, and PRMT5 mainly symmetrically dimethylated the DNA-binding domain (DBD) but not the ligand-binding domain (LBD) of RORα. To investigate whether RORα protein stability is regulated by PRMT5, we transfected HEK293FT cells with RORα and PRMT5-expressing or PRMT5-silencing (shPRMT5) vectors and then examined RORα protein stability by a cycloheximide chase assay. The results showed that PRMT5 increased RORα protein stability, while silencing PRMT5 accelerated RORα protein degradation. In PRMT5-silenced mammary epithelial cells, RORα protein expression was decreased, accompanied by an enhanced epithelial-mesenchymal transition morphology and cell invasion and migration abilities. In PRMT5-overexpressed mammary epithelial cells, RORα protein was accumulated, and cell invasion was suppressed. These findings revealed a novel mechanism by which PRMT5 regulates RORα protein stability.

A phase I study to evaluate the safety, pharmacokinetics, and pharmacodynamics of PF-06939999 (PRMT5 inhibitor) in patients with selected advanced or metastatic tumors with high incidence of splicing factor gene mutations.

BACKGROUND: Protein arginine methyltransferase 5 (PRMT5) methylates multiple substrates dysregulated in cancer, including spliceosome machinery components. PF-06939999 is a selective small-molecule PRMT5 inhibitor. PATIENTS AND METHODS: This phase I dose-escalation and -expansion trial (NCT03854227) enrolled patients with selected solid tumors. PF-06939999 was administered orally once or twice a day (q.d./b.i.d.) in 28-day cycles. The objectives were to evaluate PF-06939999 safety and tolerability to identify maximum tolerated dose (MTD) and recommended part 2 dose (RP2D), and assess pharmacokinetics (PK), pharmacodynamics [changes in plasma symmetric dimethylarginine (SDMA) levels], and antitumor activities. RESULTS: In part 1 dose escalation, 28 patients received PF-06939999 (0.5 mg q.d. to 6 mg b.i.d.). Four of 24 (17%) patients reported dose-limiting toxicities: thrombocytopenia (n = 2, 6 mg b.i.d.), anemia (n = 1, 8 mg q.d.), and neutropenia (n = 1, 6 mg q.d.). PF-06939999 exposure increased with dose. Steady-state PK was achieved by day 15. Plasma SDMA was reduced at steady state (58%-88%). Modulation of plasma SDMA was dose dependent. No MTD was determined. In part 2 dose expansion, 26 patients received PF-06939999 6 mg q.d. (RP2D). Overall (part 1 + part 2), the most common grade ≥3 treatment-related adverse events included anemia (28%), thrombocytopenia/platelet count decreased (22%), fatigue (6%), and neutropenia (4%). Three patients (6.8%) had confirmed partial response (head and neck squamous cell carcinoma, n = 1; non-small-cell lung cancer, n = 2), and 19 (43.2%) had stable disease. No predictive biomarkers were identified. CONCLUSIONS: PF-06939999 demonstrated a tolerable safety profile and objective clinical responses in a subset of patients, suggesting that PRMT5 is an interesting cancer target with clinical validation. However, no predictive biomarker was identified. The role of PRMT5 in cancer biology is complex and requires further preclinical, mechanistic investigation to identify predictive biomarkers for patient selection.

Inhibition of PRMT5-mediated regulation of DKK1 sensitizes colorectal cancer cells to chemotherapy.

The Dickkopf family proteins (DKKs) are strong Wnt signaling antagonists that play a significant role in colorectal cancer (CRC) development and progression. Recent work has shown that DKKs, mainly DKK1, are associated with the induction of chemoresistance in CRC and that DKK1 expression in cancer cells correlates with that of protein arginine N-methyltransferase 5 (PRMT5). This points to the presence of a regulatory loop between DKK1 and PRMT5. Herein, we addressed the question of whether PRMT5 contributes to DKK1 expression in CRC and hence CRC chemoresistance. Both in silico and in vitro approaches were used to explore the relationship between PRMT5 and different DKK members. Our data demonstrated that DKK1 expression is significantly upregulated in CRC clinical samples, KRAS-mutated CRC in particular and that the levels of DKK1 positively correlate with PRMT5 activation. Chromatin immunoprecipitation (ChIP) data indicated a possible epigenetic role of PRMT5 in regulating DKK1, possibly through the symmetric dimethylation of H3R8. Knockdown of DKK1 or treatment with the PRMT5 inhibitor CMP5 in combination with doxorubicin yielded a synergistic anti-tumor effect in KRAS mutant, but not KRAS wild-type, CRC cells. These findings suggest that PRMT5 regulates DKK1 expression in CRC and that inhibition of PRMT5 modulates DKK1 expression in such a way that reduces CRC cell growth.

Long Non-Coding RNA NUTM2A-AS1/miR-376a-3p/PRMT5 Axis Promotes Prostate Cancer Progression.

BACKGROUND: In recent years, significant attention has been directed towards long non-coding RNA NUT family member 2A antisense RNA 1 (NUTM2A-AS1) for its oncogenic role in tumours. This study aimed to investigate the functional and molecular mechanisms underlying NUTM2A-AS1 in prostate cancer (PCa). METHODS: NUTM2A-AS1, miR-376a-3p, and protein arginine methyltransferase 5 (PRMT5) levels were assessed in PCa samples and matched non-cancerous prostate samples. The DU145 cell line was conditioned to undergo transfection with relevant plasmids, and a cell counting kit-8 assay was performed to evaluate cell proliferation. A Transwell assay was conducted to analyse cell migration or invasion. Cell apoptosis was assessed using an annexin V-fluorescein isothiocyanate/propidium iodide apoptosis detection kit and flow cytometry. A tumour sphere formation assay was conducted to assess the ability of PCa cells to form tumour spheres. RESULTS: We found elevated expression of NUTM2A-AS1 and PRMT5 and decreased expression of miR-376a-3p in PCa samples. Inhibition of NUTM2A-AS1 or overexpression of miR-376a-3p led to reduced cell proliferation and diminished cancer stem cell-like traits in vitro. NUTM2A-AS1 regulated miR-376a-3p through competitive absorption, thereby modulating PRMT5. Up-regulation of PRMT5 nullified the therapeutic effects of inhibiting NUTM2A-AS1 or overexpressing miR-376a-3p in DU145 cells. CONCLUSIONS: NUTM2A-AS1 promotes cancer stem cell-like traits in PCa cells by targeting PRMT5 through miR-376a-3p. Therefore, these NUTM2A-AS1-based novel insights into tumour therapy hold promise for patients with PCa.

Long Non-Coding RNA NUTM2A-AS1/miR-376a-3p/PRMT5 Axis Promotes Prostate Cancer Progression

Background: In recent years, significant attention has been directed towards long non-coding RNA NUT family member 2A antisense RNA 1 (NUTM2A-AS1) for its oncogenic role in tumours. This study aimed to investigate the functional and molecular mechanisms underlying NUTM2A-AS1 in prostate cancer (PCa). Methods: NUTM2A-AS1, miR-376a-3p, and protein arginine methyltransferase 5 (PRMT5) levels were assessed in PCa samples and matched non-cancerous prostate samples. The DU145 cell line was conditioned to undergo transfection with relevant plasmids, and a cell counting kit-8 assay was performed to evaluate cell proliferation. A Transwell assay was conducted to analyse cell migration or invasion. Cell apoptosis was assessed using an annexin V-fluorescein isothiocyanate/propidium iodide apoptosis detection kit and flow cytometry. A tumour sphere formation assay was conducted to assess the ability of PCa cells to form tumour spheres. Results: We found elevated expression of NUTM2A-AS1 and PRMT5 and decreased expression of miR-376a-3p in PCa samples. Inhibition of NUTM2A-AS1 or overexpression of miR-376a-3p led to reduced cell proliferation and diminished cancer stem cell-like traits in vitro. NUTM2A-AS1 regulated miR-376a-3p through competitive absorption, thereby modulating PRMT5. Up-regulation of PRMT5 nullified the therapeutic effects of inhibiting NUTM2A-AS1 or overexpressing miR-376a-3p in DU145 cells. Conclusions: NUTM2A-AS1 promotes cancer stem cell-like traits in PCa cells by targeting PRMT5 through miR-376a-3p. Therefore, these NUTM2A-AS1-based novel insights into tumour therapy hold promise for patients with PCa. (AU)

Synthesis and biological evaluation of 1-phenyl-tetrahydro-ß-carboline-based first dual PRMT5/EGFR inhibitors as potential anticancer agents.

Protein arginine methyltransferase 5 (PRMT5) and epidermal growth factor receptor (EGFR) are both involved in the regulation of various cancer-related processes, and their dysregulation or overexpression has been observed in many types of tumors. In this study, we designed and synthesized a series of 1-phenyl-tetrahydro-ß-carboline (THßC) derivatives as the first class of dual PRMT5/EGFR inhibitors. Among the synthesized compounds, 10p showed the most potent dual PRMT5/EGFR inhibitory activity, with IC50 values of 15.47 ± 1.31 and 19.31 ± 2.14 µM, respectively. Compound 10p also exhibited promising antiproliferative activity against A549, MCF7, HeLa, and MDA-MB-231 cell lines, with IC50 values below 10 µM. Molecular docking studies suggested that 10p could bind to PRMT5 and EGFR through hydrophobic, π-π, and cation-π interactions. Furthermore, 10p displayed favorable pharmacokinetic properties and oral bioavailability (F = 30.6%) in rats, and administrated orally 10p could significantly inhibit the growth of MCF7 orthotopic xenograft tumors. These results indicate that compound 10p is a promising hit compound for the development of novel and effective dual PRMT5/EGFR inhibitors as potential anticancer agents.

SMYD4 monomethylates PRMT5 and forms a positive feedback loop to promote hepatocellular carcinoma progression.

Both lysine and arginine methyltransferases are thought to be promising therapeutic targets for malignant tumors, yet how these methyltransferases function in malignant tumors, especially hepatocellular carcinoma (HCC), has not been fully elucidated. Here, we reported that SMYD4, a lysine methyltransferase, acts as an oncogene in HCC. SMYD4 was highly upregulated in HCC and promoted HCC cell proliferation and metastasis. Mechanistically, PRMT5, a well-known arginine methyltransferase, was identified as a SMYD4-binding protein. SMYD4 monomethylated PRMT5 and enhanced the interaction between PRMT5 and MEP50, thereby promoting the symmetrical dimethylation of H3R2 and H4R3 on the PRMT5 target gene promoter and subsequently activating DVL3 expression and inhibiting expression of E-cadherin, RBL2, and miR-29b-1-5p. Moreover, miR-29b-1-5p was found to inversely regulate SMYD4 expression in HCC cells, thus forming a positive feedback loop. Furthermore, we found that the oncogenic effect of SMYD4 could be effectively suppressed by PRMT5 inhibitor in vitro and in vivo. Clinically, high coexpression of SMYD4 and PRMT5 was associated with poor prognosis of HCC patients. In summary, our study provides a model of crosstalk between lysine and arginine methyltransferases in HCC and highlights the SMYD4-PRMT5 axis as a potential therapeutic target for the treatment of HCC.

Inhibition of PRMT5/MEP50 Arginine Methyltransferase Activity Causes Cancer Vulnerability in NDRG2low Adult T-Cell Leukemia/Lymphoma.

N-myc downstream-regulated gene 2 (NDRG2), which is a tumour suppressor, is frequently lost in many types of tumours, including adult T-cell leukaemia/lymphoma (ATL). The downregulation of NDRG2 expression is involved in tumour progression through the aberrant phosphorylation of several important signalling molecules. We observed that the downregulation of NDRG2 induced the translocation of protein arginine methyltransferase 5 (PRMT5) from the nucleus to the cytoplasm via the increased phosphorylation of PRMT5 at Serine 335. In NDRG2low ATL, cytoplasmic PRMT5 enhanced HSP90A chaperone activity via arginine methylation, leading to tumour progression and the maintenance of oncogenic client proteins. Therefore, we examined whether the inhibition of PRMT5 activity is a drug target in NDRG2low tumours. The knockdown of PRMT5 and binding partner methylsome protein 50 (MEP50) expression significantly demonstrated the suppression of cell proliferation via the degradation of AKT and NEMO in NDRG2low ATL cells, whereas NDRG2-expressing cells did not impair the stability of client proteins. We suggest that the relationship between PRMT5/MEP50 and the downregulation of NDRG2 may exhibit a novel vulnerability and a therapeutic target. Treatment with the PRMT5-specific inhibitors CMP5 and HLCL61 was more sensitive in NDRG2low cancer cells than in NDRG2-expressing cells via the inhibition of HSP90 arginine methylation, along with the degradation of client proteins. Thus, interference with PRMT5 activity has become a feasible and effective strategy for promoting cancer vulnerability in NDRG2low ATL.

Excessive fatty acids activate PRMT5/MDM2/Drosha pathway to regulate miRNA biogenesis and lipid metabolism.

BACKGROUND: Excessive fatty acids in the liver lead to the accumulation of lipotoxic lipids and then cellular stress to further evoke the related disease, like non-alcoholic fatty liver disease (NAFLD). As reported, fatty acid stimulation can cause some specific miRNA dysregulation, which caused us to investigate the relationship between miRNA biogenesis and fatty acid overload. METHODS: Gene expression omnibus (GEO) dataset analysis, miRNA-seq, miRNA cleavage assay, RT-qPCR, western blotting, immunofluorescence and co-immunoprecipitation (co-IP) were used to reveal the change of miRNAs under pathological status and explore the relevant mechanism. High fat, high fructose, high cholesterol (HFHFrHC) diet-fed mice transfected with AAV2/8-shDrosha or AAV2/8-shPRMT5 were established to investigate the in vivo effects of Drosha or PRMT5 on NAFLD phenotype. RESULTS: We discovered that the cleavage of miRNAs was inhibited by analysing miRNA contents and detecting some representative pri-miRNAs in multiple mouse and cell models, which was further verified by the reduction of the Microprocessor activity in the presence of palmitic acid (PA). In vitro, PA could induce Drosha, the core RNase III in the Microprocessor complex, degrading through the proteasome-mediated pathway, while in vivo, knockdown of Drosha significantly promoted NAFLD to develop to a more serious stage. Mechanistically, our results demonstrated that PA can increase the methyltransferase activity of PRMT5 to degrade Drosha through MDM2, a ubiquitin E3 ligase for Drosha. The above results indicated that PRMT5 may be a critical regulator in lipid metabolism during NAFLD, which was confirmed by the knocking down of PRMT5 improved aberrant lipid metabolism in vitro and in vivo. CONCLUSIONS: We first demonstrated the relationship between miRNA dosage and NAFLD and proved that PA can activate the PRMT5-MDM2-Drosha signalling pathway to regulate miRNA biogenesis.

Structure-based discovery of a new series of nucleoside-derived ring-opening PRMT5 inhibitors.

The ubiquitous methyltransferases employing SAM as the methyl donor have emerged as potential targets in many disease treatments, especially in anticancer. Therefore, developing SAM-competitive inhibitors of methyltransferases is of great interest to the drug research. To explore this direction, herein, we rationally designed a series of nucleoside derivatives as potent PRMT5 inhibitors with novel scaffold. The representative compounds A2 and A8 exhibited highly potent PRMT5 inhibition activity as well as good selectivity over other PRMTs and PKMTs. Further cellular experiments revealed that compounds A2 and A8 potently reduced the level of sDMA and inhibited the proliferation of Z-138 and MOLM-13 cell lines by inducing apoptosis. Moreover, compounds A8 which had favorable pharmacokinetic properties exhibited potent antitumor efficacy without the loss of body weight in a subcutaneous MOLM-13 xenograft model. In summary, our efforts provided a series of novel nucleoside analogs as potent PRMT5 inhibitors and may also offer a new strategy to develop SAM analogs as other methyltransferases' inhibitors.

PRMT5-PAK1 Signaling Participates in Metastasis and Is Associated With Poor Prognosis in Human Esophageal Carcinoma.

BACKGROUND/AIM: Protein arginine methyltransferase 5 (PRMT5), a member of the arginine methyltransferases, is an enzyme catalyzing the methylation of arginine residuals of histones and non-histone proteins to serve as one of many critical posttranslational modifications (PTMs). Phosphorylated P21-activated kinase 1 (p-PAK1), a serine/threonine protein kinase family member, is a cytoskeletal protein that plays a critical role in metastasis. We examined the expression of PRMT5 and PAK1 in esophageal squamous cell carcinoma (ESCC) and evaluated the correlation between PRMT5/p-PAK1 and both clinicopathological parameters and prognosis of ESCC patients. MATERIALS AND METHODS: 106 tumor tissues collected from ESCC patients were assessed for PRMT5 and PAK1 expression using immunohistochemistry. Pearson's correlation and Kaplan-Meier analysis were used to estimate the correlation with the clinicopathological parameters and effect on patient survival. Western blot analysis was used to determine the PRMT5/p-PAK1 protein expression. The wound healing assay was performed to assess the effect of PRMT5 on the migration of ESCC cells. RESULTS: PRMT5 is upregulated in ESCC and the level of PRMT5 is correlated with metastasis and can serve as an independent prognostic factor for overall survival (OS). PRMT5 knockdown remarkably inhibited ESCC cell migration with concomitantly reduced levels of phosphorylated PAK1 (p-PAK1) but not total PAK1. Kaplan-Meier analysis showed that the OS of the subgroup of patients with PRMT5high/p-PAK1high is remarkably shorter than those of other subgroups (i.e., PRMT5high/p-PAK1low, PRMT5low/p-PAK1low and PRMT5low/p-PAK1high). CONCLUSION: PRMT5-PAK1 signaling participates in ESCC metastasis and can predict patients' outcomes.

ETD-Based Proteomic Profiling Improves Arginine Methylation Identification and Reveals Novel PRMT5 Substrates.

Protein arginine methylations are important post-translational modifications (PTMs) in eukaryotes, regulating many biological processes. However, traditional collision-based mass spectrometry methods inevitably cause neutral losses of methylarginines, preventing the deep mining of biologically important sites. Herein we developed an optimized mass spectrometry workflow based on electron-transfer dissociation (ETD) with supplemental activation for proteomic profiling of arginine methylation in human cells. Using symmetric dimethylarginine (sDMA) as an example, we show that the ETD-based optimized workflow significantly improved the identification and site localization of sDMA. Quantitative proteomics identified 138 novel sDMA sites as potential PRMT5 substrates in HeLa cells. Further biochemical studies on SERBP1, a newly identified PRMT5 substrate, confirmed the coexistence of sDMA and asymmetric dimethylarginine in the central RGG/RG motif, and loss of either methylation caused increased the recruitment of SERBP1 to stress granules under oxidative stress. Overall, our optimized workflow not only enabled the identification and localization of extensive, nonoverlapping sDMA sites in human cells but also revealed novel PRMT5 substrates whose sDMA may play potentially important biological functions.

CRISPR-Cas9-mediated chicken prmt5 gene knockout and its critical role in interferon regulation.

Protein arginine methyltransferase 5 (PRMT5), a type II arginine methyltransferase, controls arginine dimethylation of a variety of substrates. While many papers have reported the function of mammalian PRMT5, it remains unclear how PRMT5 functions in chicken cells. In this study, we found that chicken (ch) PRMT5 is widely expressed in a variety of chicken tissues and is distributed in both the cytoplasm and the nucleus. Ectopic expression of chPRMT5 significantly suppresses chIFN-ß activation induced by chMDA5. In addition, a prmt5 gene-deficient DF-1 cell line was constructed using CRISPR/Cas9. In comparison with the wild-type cells, the prmt5-/- DF-1 cells displays normal morphology and maintain proliferative capacity. Luciferase reporter assay and overexpression showed that prmt5-/- DF-1 cells had increased IFN-ß production. With identified chicken PRMT5 and CRISPR/Cas9 knockout performed in DF-1 cells, we uncovered a functional link of chPRMT5 in suppression of IFN-ß production and interferon-stimulated gene expression.

Combined inhibition of MTAP and MAT2a mimics synthetic lethality in tumor models via PRMT5 inhibition.

Homozygous 5'-methylthioadenosine phosphorylase (MTAP) deletions occur in approximately 15% of human cancers. Co-deletion of MTAP and methionine adenosyltransferase 2 alpha (MAT2a) induces a synthetic lethal phenotype involving protein arginine methyltransferase 5 (PRMT5) inhibition. MAT2a inhibitors are now in clinical trials for genotypic MTAP-/- cancers, however the MTAP-/- genotype represents fewer than 2% of human colorectal cancers (CRCs), limiting the utility of MAT2a inhibitors in these and other MTAP+/+ cancers. Methylthio-DADMe-immucillin-A (MTDIA) is a picomolar transition state analog inhibitor of MTAP that renders cells enzymatically MTAP-deficient to induce the MTAP-/- phenotype. Here, we demonstrate that MTDIA and MAT2a inhibitor AG-270 combination therapy mimics synthetic lethality in MTAP+/+ CRC cell lines with similar effects in mouse xenografts and without adverse histology on normal tissues. Combination treatment is synergistic with a 104-fold increase in drug potency for inhibition of CRC cell growth in culture. Combined MTDIA and AG-270 decreases S-adenosyl-L-methionine and increases 5'-methylthioadenosine in cells. The increased intracellular methylthioadenosine:S-adenosyl-L-methionine ratio inhibits PRMT5 activity, leading to cellular arrest and apoptotic cell death by causing MDM4 alternative splicing and p53 activation. Combination MTDIA and AG-270 treatment differs from direct inhibition of PRMT5 by GSK3326595 by avoiding toxicity caused by cell death in the normal gut epithelium induced by the PRMT5 inhibitor. The combination of MTAP and MAT2a inhibitors expands this synthetic lethal approach to include MTAP+/+ cancers, especially the remaining 98% of CRCs without the MTAP-/- genotype.

Alpha-synuclein promotes PRMT5-mediated H4R3me2s histone methylation by interacting with the BAF complex.

α-Synuclein (αS) is a key molecule in the pathomechanism of Parkinson's disease. Most studies on αS to date have focused on its function in the neuronal cytosol, but its action in the nucleus has also been postulated. Indeed, several lines of evidence indicate that overexpressed αS leads to epigenomic alterations. To clarify the functional role of αS in the nucleus and its pathological significance, HEK293 cells constitutively expressing αS were used to screen for nuclear proteins that interact with αS by nanoscale liquid chromatography/tandem mass spectrometry. Interactome analysis of the 229 identified nuclear proteins revealed that αS interacts with the BRG1-associated factor (BAF) complex, a family of multi-subunit chromatin remodelers important for neurodevelopment, and protein arginine methyltransferase 5 (PRMT5). Subsequent transcriptomic analysis also suggested a functional link between αS and the BAF complex. Based on these results, we analyzed the effect of αS overexpression on the BAF complex in neuronally differentiated SH-SY5Y cells and found that induction of αS disturbed the BAF maturation process, leading to a global increase in symmetric demethylation of histone H4 on arginine 3 (H4R3me2s) via enhanced BAF-PRMT5 interaction. Chromatin immunoprecipitation sequencing confirmed accumulated H4R3me2s methylation near the transcription start site of the neuronal cell adhesion molecule (NRCAM) gene, which has roles during neuronal differentiation. Transcriptional analyses confirmed the negative regulation of NRCAM by αS and PRMT5, which was reconfirmed by multiple datasets in the Gene Expression Omnibus (GEO) database. Taken together, these findings suggest that the enhanced binding of αS to the BAF complex and PRMT5 may cooperatively affect the neuronal differentiation process.

Carcinogenesis and Prognostic Utility of Arginine Methylation-Related Genes in Hepatocellular Cancer.

Protein arginine methylation is among the most important post-translational modifications and has been studied in cancers such as those of the lung and breast. However, comparatively less has been investigated regarding hepatocellular carcinoma, with an annual incidence of almost one million cases. Through using in silico methods, this study examined arginine methylation-related gene expression and methylation levels, and alongside network and enrichment analysis attempted to find how said genes can drive tumorigenesis and offer possible therapeutic targets. We found a robust relationship among the selected methylation genes, with ⅞ showing prognostic value regarding overall survival, and a medley of non-arginine methylation pathways also being highlighted through the aforementioned analysis. This study furthers our knowledge of the methylation and expression patterns of arginine histone methylation-related genes, offering jumping points for further wet-lab studies.

Pan-cancer analysis identifies protein arginine methyltransferases PRMT1 and PRMT5 and their related signatures as markers associated with prognosis, immune profile, and therapeutic response in lung adenocarcinoma.

Purpose: Protein arginine methyltransferases (PRMTs) regulate several signal transduction pathways involved in cancer progression. Recently, it has been reported that PRMTs are closely related to anti-tumor immunity; however, the underlying mechanisms have yet to be studied in lung adenocarcinoma (LUAD). In this study, we focused on PRMT1 and PRMT5, key members of the PRMT family. And their signatures in lung carcinoma associated with prognosis, immune profile, and therapeutic response including immunotherapy and radiotherapy were explored. Methods: To understand the function of PRMT1 and PRMT5 in tumor cells, we examined the association between the expression of PRMT1 and PRMT5 and the clinical, genomic, and immune characteristics, as well as the sensitivity to immunotherapy and radiotherapy. Specifically, our investigation focused on the role of PRMT1 and PRMT5 in tumor progression, with particular emphasis on interferon-stimulated genes (ISGs) and the pathway of type I interferon. Furthermore, the influence of proliferation, migration, and invasion ability was investigated based on the expression of PRMT1 and PRMT5 in human lung adenocarcinoma cell lines. Results: Through the examination of receiver operating characteristic (ROC) and survival studies, PRMT1 and PRMT5 were identified as potential biomarkers for the diagnosis and prognosis. Additionally, heightened expression of PRMT1 or PRMT5 was associated with immunosuppressive microenvironments. Furthermore, a positive correlation was observed between the presence of PRMT1 or PRMT5 with microsatellite instability, tumor mutational burden, and neoantigens in the majority of cancers. Moreover, the predictive potential of PRMT1 or PRMT5 in individuals undergoing immunotherapy has been acknowledged. Our study ultimately revealed that the inhibition of PRMT1 and PRMT5 in lung adenocarcinoma resulted in the activation of the cGAS-STING pathway, especially after radiation. Favorable prognosis was observed in lung adenocarcinoma patients receiving radiotherapy with reduced PRMT1 or PRMT5 expression. It was also found that the expression of PRMT1 and PRMT5 influenced proliferation, migration, and invasion of human lung adenocarcinoma cell lines. Conclusion: The findings indicate that PRMT1 and PRMT5 exhibit potential as immune-related biomarkers for the diagnosis and prognosis of cancer. Furthermore, these biomarkers could be therapeutically targeted to augment the efficacy of immunotherapy and radiotherapy in lung adenocarcinoma.

PRMT5 as a Potential Therapeutic Target in MYC-Amplified Medulloblastoma.

MYC amplification or overexpression is most common in Group 3 medulloblastomas and is positively associated with poor clinical outcomes. Recently, protein arginine methyltransferase 5 (PRMT5) overexpression has been shown to be associated with tumorigenic MYC functions in cancers, particularly in brain cancers such as glioblastoma and medulloblastoma. PRMT5 regulates oncogenes, including MYC, that are often deregulated in medulloblastomas. However, the role of PRMT5-mediated post-translational modification in the stabilization of these oncoproteins remains poorly understood. The potential impact of PRMT5 inhibition on MYC makes it an attractive target in various cancers. PRMT5 inhibitors are a promising class of anti-cancer drugs demonstrating preclinical and preliminary clinical efficacies. Here, we review the publicly available preclinical and clinical studies on PRMT5 targeting using small molecule inhibitors and discuss the prospects of using them in medulloblastoma therapy.