PRMT1 promotes pancreatic cancer development and resistance to chemotherapy.

Pancreatic ductal adenocarcinoma (PDAC) remains one of the most lethal types of cancer, and novel treatment regimens are direly needed. Epigenetic regulation contributes to the development of various cancer types, but its role in the development of and potential as a therapeutic target for PDAC remains underexplored. Here, we show that PRMT1 is highly expressed in murine and human pancreatic cancer and is essential for cancer cell proliferation and tumorigenesis. Deletion of PRMT1 delays pancreatic cancer development in a KRAS-dependent mouse model, and multi-omics analyses reveal that PRMT1 depletion leads to global changes in chromatin accessibility and transcription, resulting in reduced glycolysis and a decrease in tumorigenic capacity. Pharmacological inhibition of PRMT1 in combination with gemcitabine has a synergistic effect on pancreatic tumor growth in vitro and in vivo. Collectively, our findings implicate PRMT1 as a key regulator of pancreatic cancer development and a promising target for combination therapy.

Yifei Sanjie formula alleviates lung cancer progression via regulating PRMT6-YBX1-CDC25A axis.

Lung cancer (LC) is the most prevalent cancer type, with a high mortality rate worldwide. The current treatment options for LC have not been particularly successful in improving patient outcomes. Yifei Sanjie (YFSJ), a well-applicated traditional Chinese medicine formula, is widely used to treat pulmonary diseases, especially LC, yet little is known about its molecular mechanisms. This study was conducted to explore the molecular mechanism by which YFSJ ameliorated LC progression. The A549, NCI-H1975, and Calu-3 cells were treated with the YFSJ formula and observed for colony number, apoptosis, migration, and invasion properties recorded via corresponding assays. The PRMT6-YBX1-CDC25A axis was tested and verified through luciferase reporter, RNA immunoprecipitation, and chromatin immunoprecipitation assays and rescue experiments. Our results demonstrated that YFSJ ameliorated LC cell malignant behaviors by increasing apoptosis and suppressing proliferation, migration, and invasion processes. We also noticed that the xenograft mouse model treated with YFSJ significantly reduced tumor growth compared with the control untreated group in vivo. Mechanistically, it was found that YFSJ suppressed the expression of PRMT6, YBX1, and CDC25A, while the knockdown of these proteins significantly inhibited colony growth, migration, and invasion, and boosted apoptosis in LC cells. In summary, our results suggest that YFSJ alleviates LC progression via the PRMT6-YBX1-CDC25A axis, confirming its efficacy in clinical use. The findings of our study provide a new regulatory network for LC growth and metastasis, which could shed new insights into pulmonary medical research.

Knockdown of PRMT1 suppresses the malignant biological behavior of osteosarcoma cells and increases cisplatin sensitivity via c-Myc-mediated BCAT1 downregulation.

Increasing evidence indicated that protein arginine methyltransferase-1 (PRMT1) is an oncogene in multiple malignant tumors, including osteosarcoma (OS). The aim of this study was to investigate the underlying mechanism of PRMT1 in OS. The effects of PRMT1 or BCAT1, branched-chain amino acid transaminase 1 (BCAT1) on OS cell proliferation, invasion, autophagy, and apoptosis in vitro were examined. Moreover, molecular control of PRMT1 on c-Myc or transactivation of BCAT1 on c-Myc was assessed by chromatin immunoprecipitation and quantitative reverse transcription PCR assays. The effects of PRMT1 in vivo were examined with a xenograft tumor model. The results showed that PRMT1 was potently upregulated in OS tissues and cells. Upregulation of PRMT1 markedly increased OS cell proliferation and invasion in vitro and reduced cell apoptosis, whereas PRMT1 silencing showed the opposite effects. Cisplatin, one of the most effective chemotherapeutic drugs, improved cell survival rate by inducing the expression of PRMT1 to downregulate the cisplatin sensitivity. Meanwhile, the cisplatin-induced upregulation of PRMT1 expression caused dramatically autophagy induction and autophagy-mediated apoptosis by inactivating the mTOR signaling pathway, which could be reversed by 3-methyladenine, an autophagy inhibitor, or PRMT1 silencing. PRMT1 could activate c-Myc transcription and increase c-Myc-mediated expression of BCAT1. Furthermore, BCAT1 overexpression counteracted the effects of PRMT1 knockdown on cell proliferation, invasion, and apoptosis. Of note, deficiency of PRMT1 suppressed tumor growth in vivo. PRMT1 facilitated the proliferation and invasion of OS cells, inhibited cell apoptosis, and decreased chemotherapy sensitivity through c-Myc/BCAT1 axis, which may become potential target in treating OS.

Promising role of protein arginine methyltransferases in overcoming anti-cancer drug resistance.

Drug resistance remains a major challenge in cancer treatment, necessitating the development of novel strategies to overcome it. Protein arginine methyltransferases (PRMTs) are enzymes responsible for epigenetic arginine methylation, which regulates various biological and pathological processes, as a result, they are attractive therapeutic targets for overcoming anti-cancer drug resistance. The ongoing development of small molecules targeting PRMTs has resulted in the generation of chemical probes for modulating most PRMTs and facilitated clinical treatment for the most advanced oncology targets, including PRMT1 and PRMT5. In this review, we summarize various mechanisms underlying protein arginine methylation and the roles of specific PRMTs in driving cancer drug resistance. Furthermore, we highlight the potential clinical implications of PRMT inhibitors in decreasing cancer drug resistance. PRMTs promote the formation and maintenance of drug-tolerant cells via several mechanisms, including altered drug efflux transporters, autophagy, DNA damage repair, cancer stem cell-related function, epithelial-mesenchymal transition, and disordered tumor microenvironment. Multiple preclinical and ongoing clinical trials have demonstrated that PRMT inhibitors, particularly PRMT5 inhibitors, can sensitize cancer cells to various anti-cancer drugs, including chemotherapeutic, targeted therapeutic, and immunotherapeutic agents. Combining PRMT inhibitors with existing anti-cancer strategies will be a promising approach for overcoming anti-cancer drug resistance. Furthermore, enhanced knowledge of the complex functions of arginine methylation and PRMTs in drug resistance will guide the future development of PRMT inhibitors and may help identify new clinical indications.

PRMT blockade induces defective DNA replication stress response and synergizes with PARP inhibition.

Multiple cancers exhibit aberrant protein arginine methylation by both type I arginine methyltransferases, predominately protein arginine methyltransferase 1 (PRMT1) and to a lesser extent PRMT4, and by type II PRMTs, predominately PRMT5. Here, we perform targeted proteomics following inhibition of PRMT1, PRMT4, and PRMT5 across 12 cancer cell lines. We find that inhibition of type I and II PRMTs suppresses phosphorylated and total ATR in cancer cells. Loss of ATR from PRMT inhibition results in defective DNA replication stress response activation, including from PARP inhibitors. Inhibition of type I and II PRMTs is synergistic with PARP inhibition regardless of homologous recombination function, but type I PRMT inhibition is more toxic to non-malignant cells. Finally, we demonstrate that the combination of PARP and PRMT5 inhibition improves survival in both BRCA-mutant and wild-type patient-derived xenografts without toxicity. Taken together, these results demonstrate that PRMT5 inhibition may be a well-tolerated approach to sensitize tumors to PARP inhibition.

Phase 1 study of JNJ-64619178, a protein arginine methyltransferase 5 inhibitor, in patients with lower-risk myelodysplastic syndromes.

Splicing factor (SF) gene mutations are frequent in myelodysplastic syndromes (MDS), and agents that modulate RNA splicing are hypothesized to provide clinical benefit. JNJ-64619178, a protein arginine methyltransferase 5 (PRMT5) inhibitor, was evaluated in patients with lower-risk (LR) MDS in a multi-part, Phase 1, multicenter study. The objectives were to determine a tolerable dose and to characterize safety, pharmacokinetics, pharmacodynamics, and preliminary clinical activity. JNJ-64619178 was administered on a 14 days on/7 days off schedule or every day on a 21-day cycle to patients with International Prognostic Scoring System (IPSS) Low or Intermediate-1 risk MDS who were red blood cell transfusion-dependent. Twenty-four patients were enrolled; 15 (62.5 %) patients had low IPSS risk score, while 18 (75.0 %) had an SF3B1 mutation. Median duration of treatment was 3.45 months (range: 0.03-6.93). No dose limiting toxicities were observed. The 0.5 mg once daily dose was considered better tolerated and chosen for dose expansion. Twenty-three (95.8 %) patients experienced treatment-emergent adverse events (TEAE). The most common TEAEs were neutropenia (15 [62.5 %]) and thrombocytopenia (14 [58.3 %]). JNJ-64619178 pharmacokinetics was dose-dependent. Target engagement as measured by plasma symmetric di-methylarginine was observed across all dose levels; however, variant allele frequency of clonal mutations in bone marrow or blood did not show sustained reductions from baseline. No patient achieved objective response or hematologic improvement per International Working Group 2006 criteria, or transfusion independence. A tolerable dose of JNJ-64619178 was identified in patients with LR MDS. However, no evidence of clinical benefit was observed.

Nuclear PRMT5 is a biomarker of sensitivity to tamoxifen in ERα+ breast cancer.

Endocrine therapies targeting estrogen signaling, such as tamoxifen, have significantly improved management of estrogen receptor alpha (ERα)-positive breast cancers. However, their efficacy is limited by intrinsic and acquired resistance to treatment, and there is currently no predictive marker of response to these anti-estrogens to guide treatment decision. Here, using two independent cohorts of breast cancer patients, we identified nuclear PRMT5 expression as an independent predictive marker of sensitivity to tamoxifen. Mechanistically, we discovered that tamoxifen stimulates ERα methylation by PRMT5, a key event for its binding to corepressors such as SMRT and HDAC1, participating in the inhibition of the transcriptional activity of ERα. Although PRMT5 is mainly localized in the cytoplasm of tumor cells, our analyses show that tamoxifen triggers its nuclear translocation in tamoxifen-sensitive tumors but not in resistant ones. Hence, we unveil a biomarker of sensitivity to tamoxifen in ERα-positive breast tumors that could be used to enhance the response of breast cancer patients to endocrine therapy, by fostering its nuclear expression.

Targeting epigenetic features in clear cell sarcomas based on patient-derived cell lines.

BACKGROUND: Clear cell sarcomas (CCSs) are translocated aggressive malignancies, most commonly affecting young adults with a high incidence of metastases and a poor prognosis. Research into the disease is more feasible when adequate models are available. By establishing CCS cell lines from a primary and metastatic lesion and isolating healthy fibroblasts from the same patient, the in vivo process is accurately reflected and aspects of clinical multistep carcinogenesis recapitulated. METHODS: Isolated tumor cells and normal healthy skin fibroblasts from the same patient were compared in terms of growth behavior and morphological characteristics using light and electron microscopy. Tumorigenicity potential was determined by soft agar colony formation assay and in vivo xenograft applications. While genetic differences between the two lineages were examined by copy number alternation profiles, nuclear magnetic resonance spectroscopy determined arginine methylation as epigenetic features. Potential anti-tumor effects of a protein arginine N-methyltransferase type I (PRMT1) inhibitor were elicited in 2D and 3D cell culture experiments using cell viability and apoptosis assays. Statistical significance was calculated by one-way ANOVA and unpaired t-test. RESULTS: The two established CCS cell lines named MUG Lucifer prim and MUG Lucifer met showed differences in morphology, genetic and epigenetic data, reflecting the respective original tissue. The detailed cell line characterization especially in regards to the epigenetic domain allows investigation of new innovative therapies. Based on the epigenetic data, a PRMT1 inhibitor was used to demonstrate the targeted antitumor effect; normal tissue cells isolated and immortalized from the same patient were not affected with the IC50 used. CONCLUSIONS: MUG Lucifer prim, MUG Lucifer met and isolated and immortalized fibroblasts from the same patient represent an ideal in vitro model to explore the biology of CCS. Based on this cell culture model, novel therapies could be tested in the form of PRMT1 inhibitors, which drive tumor cells into apoptosis, but show no effect on fibroblasts, further supporting their potential as promising treatment options in the combat against CCS. The data substantiate the importance of tailored therapies in the advanced metastatic stage of CCS.

Protein Arginine Methyltransferases 5 (PRMT5) affect Multiple Stages of Autophagy and Modulate Autophagy-related Genes in Controlling Breast Cancer Tumorigenesis.

BACKGROUND: Autophagy disorders are linked to human cancer, and the details of their mechanisms remain unclear. OBJECTIVE: To investigate the regulatory role of PRMT5 in the autophagy of breast cancer cells. METHODS: Human breast adenocarcinoma cell lines (MDA-MB-231, MCF7) were cultured. Plasmids of overexpression and down-regulation of PRMT5 were transfected into MDA-MB-231 and MCF7 cells. The MTT assay was used to determine the proliferation of MDA-MB-231 and MCF7 cells. A western blotting assay was used to verify the expression of autophagy-associated molecules. Immunofluorescence was applied to observe the expression of GFP-LC3. RESULTS: The expression of PRMT5 decreased the sensitivity to rapamycin and nutrient deprivation. PRMT5 acts as an oncogene to promote cell proliferation and influences migration and stamness. PRMT5 expression elevated the autophagic activity initiated by EBSS and Rapamycin. PRMT5 was necessary and sufficient to enhance stress-induced autophagy. PRMT5 could improve several autophagy- related gene expressions. Atg5 expression could be regulated by activating the PRMT5 and PDCD4 molecules. The PRMT5 molecule could mediate the regulation of ULK1 expression. CONCLUSION: PRMT5 influenced multiple stages of autophagy in controlling autophagy and tumorigenesis. Autophagy-related PRMT5 might be a respected target for therapeutic interventions in cancers. This study would provide new ideas for treating and selecting breast cancer targets.

Loss of PRMT7 reprograms glycine metabolism to selectively eradicate leukemia stem cells in CML.

Our group has reported previously on the role of various members of the protein arginine methyltransferase (PRMT) family, which are involved in epigenetic regulation, in the progression of leukemia. Here, we explored the role of PRMT7, given its unique function within the PRMT family, in the maintenance of leukemia stem cells (LSCs) in chronic myeloid leukemia (CML). Genetic loss of Prmt7, and the development and testing of a small-molecule specific inhibitor of PRMT7, showed that targeting PRMT7 delayed leukemia development and impaired self-renewal of LSCs in a CML mouse model and in primary CML CD34+ cells from humans without affecting normal hematopoiesis. Mechanistically, loss of PRMT7 resulted in reduced expressions of glycine decarboxylase, leading to the reprograming of glycine metabolism to generate methylglyoxal, which is detrimental to LSCs. These findings link histone arginine methylation with glycine metabolism, while suggesting PRMT7 as a potential therapeutic target for the eradication of LSCs in CML.

Targeting epigenetic modifications in cancer therapy: erasing the roadmap to cancer.

Epigenetic dysregulation is a common feature of most cancers, often occurring directly through alteration of epigenetic machinery. Over the last several years, a new generation of drugs directed at epigenetic modulators have entered clinical development, and results from these trials are now being disclosed. Unlike first-generation epigenetic therapies, these new agents are selective, and many are targeted to proteins which are mutated or translocated in cancer. This review will provide a summary of the epigenetic modulatory agents currently in clinical development and discuss the opportunities and challenges in their development. As these drugs advance in the clinic, drug discovery has continued with a focus on both novel and existing epigenetic targets. We will provide an overview of these efforts and the strategies being employed.