Protein arginine methyltransferase 5-mediated epigenetic silencing of IRX1 contributes to tumorigenicity and metastasis of gastric cancer

The protein arginine methyltransferase family (PRMTs) regulates metastases in various tumors: From experimental study to clinical application

Tumor metastasis is the leading cause of mortality among advanced cancer patients. Understanding its mechanisms and treatment strategies is vital for clinical application. Arginine methylation, a post-translational modification catalyzed by protein arginine methyltransferases (PRMTs), is implicated in diverse physiological processes and disease progressions. Previous research has demonstrated PRMTs' involvement in tumor occurrence, progression, and metastasis. This review offers a comprehensive summary of the relationship between PRMTs, prognosis, and metastasis in various cancers. Our focus centers on elucidating the molecular mechanisms through which PRMTs regulate tumor metastasis. We also discuss relevant clinical trials and effective PRMT inhibitors, including chemical compounds, long non-coding RNA (lncRNA), micro-RNA (miRNA), and nanomaterials, for treating tumor metastasis. While a few studies present conflicting results, the overall trajectory suggests that inhibiting arginine methylation exhibits promise in curtailing tumor metastasis across various cancers. Nonetheless, the underlying mechanisms and molecular interactions are diverse. The development of inhibitors targeting arginine methylation, along with the progression of clinical trials, holds substantial potential in the field of tumor metastasis, meriting sustained attention.

IRX1 is a novel gene, overexpressed in high-grade IDH-mutant astrocytomas

BACKGROUND

IDH-mutant astrocytomas include CNS WHO grade 2 (A2), grade 3 (A3) and grade 4 (A4), of which A3 and A4 are high-grade. A3 has a heterogenous clinical outcome that cannot be explained entirely by the existing molecular biomarkers. We comprehensively studied the transcriptome profile of A3 to determine clinical significance.

METHODS

TCGA mRNA-sequencing data of A3 was analyzed to derive differentially expressed genes (DEG), which were short-listed using various approaches. mRNA expression of the short-listed genes was validated using NanoString platform on a uniformly treated and molecularly characterized A3 cohort. Protein expression of one prognostically significant gene, Iroquois-class homeodomain (IRX1) was assessed by immunohistochemistry and correlated with patient survival and tumor recurrence. IRX1 expression was also studied in different grades of astrocytoma. Since DNA methyltransferase 3 alpha (DNMT3A) influences IRX1 expression, its mutations were evaluated in a subset of tumors.

RESULTS

TCGA analysis identified 96 DEG in A3 tumours. 57 genes were short-listed and finally narrowed down to 14 genes. mRNA values of 12/14 genes validated in our cohort. On multiple-variable analysis, IRX1 was the most prognostically relevant gene, with respect to progression free survival of patients. Further, IRX1 immunoexpression was significantly higher in A3 and A4 when compared to A2 and glioblastoma. Higher IRX1 immunoexpression correlated with poor prognosis in patients with A3 tumours. Also, a higher IRX1 expression was associated with DNMT3A mutation.

CONCLUSION

Our study identifies IRX1 as a novel biomarker overexpressed in high-grade IDH-mutant astrocytomas with prognostic significance in A3. DNMT3A mutation probably modulates IRX1 expression.

Iroquois Family Genes in Gastric Carcinogenesis: A Comprehensive Review

Gastric cancer (GC) is the fifth leading cause of cancer-associated death worldwide, accounting for 768,793 related deaths and 1,089,103 new cases in 2020. Despite diagnostic advances, GC is often detected in late stages. Through a systematic literature search, this study focuses on the associations between the Iroquois gene family and GC. Accumulating evidence indicates that Iroquois genes are involved in the regulation of various physiological and pathological processes, including cancer. To date, information about Iroquois genes in GC is very limited. In recent years, the expression and function of Iroquois genes examined in different models have suggested that they play important roles in cell and cancer biology, since they were identified to be related to important signaling pathways, such as wingless, hedgehog, mitogen-activated proteins, fibroblast growth factor, TGFβ, and the PI3K/Akt and NF-kB pathways. In cancer, depending on the tumor, Iroquois genes can act as oncogenes or tumor suppressor genes. However, in GC, they seem to mostly act as tumor suppressor genes and can be regulated by several mechanisms, including methylation, microRNAs and important GC-related pathogens. In this review, we provide an up-to-date review of the current knowledge regarding Iroquois family genes in GC.

Interplays between non-coding RNAs and chemokines in digestive system cancers

Within tumors, chemokines and their cognate receptors are expressed by infiltrated leukocytes, cancerous cells, and related cells of stroma, like tumor-associated fibroblasts and tumor-associated macrophages. In malignancies, the altered expression of chemokines/chemokine receptors governs leukocyte infiltration and activation, epithelial-mesenchymal transition (EMT), cancer cell proliferation, angiogenesis, and metastasis. Non-coding RNAs (ncRNAs) contribute to multiple physiological and pathophysiological processes. Some miRNAs can exert anti-tumorigenic activity in digestive system malignancies by repressing the expression of tumor-promoting chemokines/chemokine receptors or by upregulating tumor-suppressing chemokines/chemokine receptors. However, many miRNAs exert pro-tumorigenic activity by suppressing the expression of chemokines/chemokine receptors or by upregulating tumor-promoting chemokines/chemokine receptors. LncRNA and circRNAs also exert pro- and anti-tumorigenic effects by targeting downstream miRNAs influencing the expression of tumor-promoting and tumor-suppressor chemokines/chemokine receptors. On the other side, some chemokines influence the expression of ncRNAs affecting tumor formation. The current review explains the communications between ncRNAs and chemokines/chemokine receptors in certain digestive system malignancies, such as gastric, colorectal, and pancreatic cancers and hepatocellular carcinoma to gain better insights into their basic crosstalk as well as possible therapeutic modalities.

Protein Arginine Methyltransferase 5 (PRMT5) Inhibitors in Oncology Clinical Trials: A review

Protein arginine methyltransferase 5 (PRMT5) inhibitors are a new class of antineoplastic agents showing promising preliminary clinical efficacy. Targeting an enzyme involved in a wide array of cellular and transcriptional pro-oncogenic processes, this class offers multifaceted tumor-suppressive effects. Partial response has been seen in adenoid cystic carcinoma from both GSK3326595 and JNJ-64619178, with four cases of stable disease seen with PRT543. Highly significant is a durable complete response in isocitrate dehydrogenase 1-mutated glioblastoma multiforme with PRT811. Both alone and in combination with existing chemotherapies and immunotherapies, this class shows promising preliminary data, particularly in cancers with splicing mutations and DNA damage repair deficiencies. Further studies are warranted, and there are clinical trials to come whose data will be telling of the efficacy of PRMT5 inhibitors in both hematologic and solid malignancies. The aim of this study is to compile available results of PRMT5 inhibitors in oncology clinical trials.

PRMT5 acts as a tumor suppressor by inhibiting Wnt/β-catenin signaling in murine gastric tumorigenesis

Previous studies have demonstrated the in vitro oncogenic role of protein arginine methyltransferase 5 (PRMT5) in gastric cancer cell lines. The in vivo function of PRMT5 in gastric tumorigenesis, however, is still unexplored. Here, we showed that Prmt5 deletion in mouse gastric epithelium resulted in spontaneous tumorigenesis in gastric antrum. All Prmt5-deficient mice displayed intestinal-type gastric cancer within 4 months of age. Of note, 20% (2/10) of Prmt5 mutants finally developed into invasive gastric cancer by 8 months of age. Gastric cancer caused by PRMT5 loss exhibited the increase in Lgr5⁺ stem cells, which are proposed to contribute to both the gastric tumorigenesis and progression in mouse models. Consistent with the notion that Lgr5 is the target of Wnt/β-catenin signaling, whose activation is the most predominant driver for gastric tumorigenesis, Prmt5 mutant gastric cancer showed the activation of Wnt/β-Catenin signaling. Furthermore, in human gastric cancer samples, PRMT5 deletion and downregulation were frequently observed and associated with the poor prognosis. We propose that as opposed to the tumor-promoting role of PRMT5 well-established in the progression of various cancer types, PRMT5 functions as a tumor suppressor in vivo, at least during gastric tumor formation.

Impacts and mechanisms of metabolic reprogramming of tumor microenvironment for immunotherapy in gastric cancer

Metabolic disorders and abnormal immune function changes occur in tumor tissues and cells to varying degrees. There is increasing evidence that reprogrammed energy metabolism contributes to the development of tumor suppressive immune microenvironment and influences the course of gastric cancer (GC). Current studies have found that tumor microenvironment (TME) also has important clinicopathological significance in predicting prognosis and therapeutic efficacy. Novel approaches targeting TME therapy, such as immune checkpoint blockade (ICB), metabolic inhibitors and key enzymes of immune metabolism, have been involved in the treatment of GC. However, the interaction between GC cells metabolism and immune metabolism and how to make better use of these immunotherapy methods in the complex TME in GC are still being explored. Here, we discuss how metabolic reprogramming of GC cells and immune cells involved in GC immune responses modulate anti-tumor immune responses, as well as the effects of gastrointestinal flora in TME and GC. It is also proposed how to enhance anti-tumor immune response by understanding the targeted metabolism of these metabolic reprogramming to provide direction for the treatment and prognosis of GC.

Protein arginine methyltransferases: promising targets for cancer therapy

Protein methylation, a post-translational modification (PTM), is observed in a wide variety of cell types from prokaryotes to eukaryotes. With recent and rapid advancements in epigenetic research, the importance of protein methylation has been highlighted. The methylation of histone proteins that contributes to the epigenetic histone code is not only dynamic but is also finely controlled by histone methyltransferases and demethylases, which are essential for the transcriptional regulation of genes. In addition, many nonhistone proteins are methylated, and these modifications govern a variety of cellular functions, including RNA processing, translation, signal transduction, DNA damage response, and the cell cycle. Recently, the importance of protein arginine methylation, especially in cell cycle regulation and DNA repair processes, has been noted. Since the dysregulation of protein arginine methylation is closely associated with cancer development, protein arginine methyltransferases (PRMTs) have garnered significant interest as novel targets for anticancer drug development. Indeed, several PRMT inhibitors are in phase 1/2 clinical trials. In this review, we discuss the biological functions of PRMTs in cancer and the current development status of PRMT inhibitors in cancer therapy.

PRMT5: a putative oncogene and therapeutic target in prostate cancer

Protein arginine methyltransferase 5 (PRMT5) was discovered two decades ago. The first decade focused on the biochemical characterization of PRMT5 as a regulator of many cellular processes in a healthy organism. However, over the past decade, evidence has accumulated to suggest that PRMT5 may function as an oncogene in multiple cancers via both epigenetic and non-epigenetic mechanisms. In this review, we focus on recent progress made in prostate cancer, including the role of PRMT5 in the androgen receptor (AR) expression and signaling and DNA damage response, particularly DNA double-strand break repair. We also discuss how PRMT5-interacting proteins that are considered PRMT5 cofactors may cooperate with PRMT5 to regulate PRMT5 activity and target gene expression, and how PRMT5 can interact with other epigenetic regulators implicated in prostate cancer development and progression. Finally, we suggest that targeting PRMT5 may be employed to develop multiple therapeutic approaches to enhance the treatment of prostate cancer.

PRMT5 Promotes EMT Through Regulating Akt Activity in Human Lung Cancer

The type II protein arginine methyltransferase 5 (PRMT5) has been engaged in various human cancer development and progression types. Nevertheless, few studies uncover the biological functions of PRMT5 in the epithelial-mesenchymal transition (EMT) of human lung cancer cells, and the associated molecular mechanisms and signaling cascades are entirely unknown. Here, we show that PRMT5 is the ectopic expression in human lung cancer tissues and cell lines. Further study reveals that silencing PRMT5 by lentivirus-mediated shRNA or blocking of PRMT5 by specific inhibitor GSK591 attenuates the expression levels of EMT-related markers in vivo, using the xenograft mouse model. Moreover, our results show that down-regulation of PRMT5 impairs EGFR/Akt signaling cascades in human lung cancer cells, whereas re-expression of PRMT5 recovers those changes, suggesting that PRMT5 regulates EMT probably through EGFR/Akt signaling axis. Altogether, our results demonstrate that PRMT5 serves as a critical oncogenic regulator and promotes EMT in human lung cancer cells. More importantly, our findings also suggest that PRMT5 may be a potential therapeutic candidate for the treatment of human lung cancer.

Coordinated methyl readers: Functional communications in cancer

Methylation is a major post-translational modification (PTM) generated by methyltransferase on target proteins; it is recognized by the epigenetic reader to expand the functional diversity of proteins. Methylation can occur on specific lysine or arginine residues localized within regulatory domains in both histone and nonhistone proteins, thereby allowing distinguished properties of the targeted protein. Methylated residues are recognized by chromodomain, malignant brain tumor (MBT), Tudor, plant homeodomain (PHD), PWWP, WD-40, ADD, and ankyrin repeats by an induced-fit mechanism. Methylation-dependent activities regulate distinct aspects of target protein function and are largely reliant on methyl readers of histone and nonhistone proteins in various diseases. Methylation of nonhistone proteins that are recognized by methyl readers facilitates the degradation of unwanted proteins, as well as the stabilization of necessary proteins. Unlike nonhistone substrates, which are mainly monomethylated by methyltransferase, histones are di- or trimethylated by the same methyltransferases and then connected to other critical regulators by methyl readers. These fine-tuned controls by methyl readers are significant for the progression or inhibition of diseases, including cancers. Here, current knowledge and our perspectives about regulating protein function by methyl readers are summarized. We also propose that expanded research on the strong crosstalk mechanisms between methylation and other PTMs via methyl readers would augment therapeutic research in cancer.

Epigenetic Regulatory Enzymes: mutation Prevalence and Coexistence in Cancers

Epigenetic regulation is an important layer of transcriptional control with the particularity to affect the broad spectrum of genome. Over the years, largely due to the substantial number of recurrent mutations, there have been hundreds of novel driver genes characterized in various cancers. Additionally, the relative contribution of two dysregulated epigenomic entities (DNA methylation and histone modifications) that gradually drive the cancer phenotype remains in the research focus. However, a complex scenario arises when the disease phenotype does not harbor any relevant mutation or an abnormal transcription level. Although the cancer landscape involves the contribution of multiple genetic and non-genetic factors, herein, we discuss specifically the mutation spectrum of epigenetically-related enzymes in cancer. In addition, we address the coexistence of these two epigenetic entities in malignant human diseases, especially cancer. We suggest that the study of epigenetically-related somatic mutations in the early cellular differentiation stage of embryonic development might help to understand their later-staged footprints in the cancer genome. Furthermore, understanding the co-occurrence and/or inverse association of different disease types and redefining the general definition of "healthy" controls could provide insights into the genome reorganization.

PRMT5 functionally associates with EZH2 to promote colorectal cancer progression through epigenetically repressing CDKN2B expression

Background: Protein arginine methyltransferase 5 (PRMT5) is a type II arginine methyltransferase that symmetrically di-methylates arginine residues on both histone and non-histone protein substrates. Accumulating evidence suggests that PRMT5 exerts its oncogenic properties in a wide spectrum of human malignancies. However, the underlying mechanisms by which PRMT5 contributes to the progression of colorectal cancer (CRC) remain to be defined. Methods: Western blot and real-time PCR were used to analyze the expression of CDKN2B. Co-immunoprecipitation (Co-IP), immunofluorescence and GST pulldown assays were employed to investigate the interaction between PRMT5 and EZH2. Luciferase reporter and chromatin immunoprecipitation (ChIP) assays were performed to validate CDKN2B as a direct target of PRMT5/EZH2. DNA methylation status at the CpG islands of promoter region of CDKN2B gene was analyzed by bisulfite sequencing. The effect of PRMT5/EZH2 on malignant phenotypes was examined through in vitro and in vivo assays. PRMT5 and EZH2 protein expression levels in CRC tissues were analyzed by immunohistochemistry (IHC) staining. Results: We observed that PRMT5-deficient CRC cells exhibit proliferation defects in vitro. PRMT5 was identified as a major transcriptional repressor of CDKN2B (p15INK4b) for determining CRC progression. Mechanistically, PRMT5-mediated histone marks H4R3me2s and H3R8me2s were predominantly deposited at the promoter region of CDKN2B gene in CRC cells. Knockdown of PRMT5 in CRC cells decreased the accumulation of H4R3me2s and H3R8me2s marks and reduced the CpG methylation level of CDKN2B promoter, then re-activated CDKN2B expression. Strikingly, silencing of CDKN2B partially abrogated the proliferation defects caused by PRMT5 depletion in vitro and in vivo. Furthermore, we proved that PRMT5 interacted with Enhancer of zeste homolog 2 (EZH2), leading to enhanced EZH2 binding and H3K27me3 deposition together with decreased transcriptional output of CDKN2B gene. Importantly, we found that the combined interventions exerted a synergistic inhibitory effect of combined treatment with PRMT5i (GSK591) and EZH2i (GSK126) on the growth of CRC cells/xenografts in vitro and in vivo. Moreover, PRMT5 and EZH2 were found to be significantly elevated and associated with poor prognosis in CRC patients. Conclusion: PRMT5 functionally associates with EZH2 to promote CRC progression through epigenetically repressing CDKN2B expression. Thus, our findings raise the possibility that combinational intervention of PRMT5 and EZH2 may be a promising strategy for CRC therapy.

Protein arginine methyltransferase 5 (PRMT5) activates WNT/β-catenin signalling in breast cancer cells via epigenetic silencing of DKK1 and DKK3

Protein arginine methyltransferase 5 (PRMT5) activity is dysregulated in many aggressive cancers and its enhanced levels are associated with increased tumour growth and survival. However, the role of PRMT5 in breast cancer remains underexplored. In this study, we show that PRMT5 is overexpressed in breast cancer cell lines, and that it promotes WNT/β-CATENIN proliferative signalling through epigenetic silencing of pathway antagonists, DKK1 and DKK3, leading to enhanced expression of c-MYC, CYCLIN D1 and SURVIVIN. Through chromatin immunoprecipitation (ChIP) studies, we found that PRMT5 binds to the promoter region of WNT antagonists, DKK1 and DKK3, and induces symmetric methylation of H3R8 and H4R3 histones. Our findings also show that PRMT5 inhibition using a specific small molecule inhibitor, compound 5 (CMP5), reduces PRMT5 recruitment as well as methylation of H3R8 and H4R3 histones in the promoter regions of DKK1 and DKK3, which consequently results in reduced expression CYCLIN D1 and SURVIVIN. Furthermore, CMP5 treatment either alone or in combination with 5-Azacytidine and Trichostatin A restored expression of DKK1 and DKK3 in TNBCs. PRMT5 inhibition also altered the growth characteristics of breast cancer cells and induced their death. Collectively, these results show that PRMT5 controls breast cancer cell growth through epigenetic silencing of WNT/β-CATENIN pathway antagonists, DKK1 and DKK3, resulting in up-regulation of WNT/β-CATENIN proliferative signalling.

Clinicopathological and Prognostic Significance of PRMT5 in Cancers: A System Review and Meta-Analysis

PURPOSE

Since protein arginine methyltransferase 5 (PRMT5) is abnormally expressed in various tumors, in this study we aim to assess the association between PRMT5 and clinicopathological and prognostic features.

METHODS

Electronic databases including PubMed, Web of Science, Scopus, ScienceDirect, and the Cochrane Library were searched until July 25, 2021. The critical appraisal of the eligible studies was performed using the Newcastle-Ottawa Quality Assessment Scale. Pooled hazard ratios (HR) and pooled odds ratios (OR) were calculated to assess the effect. Engauge Digitizer version 12.1, STATA version 15.1, and R version 4.0.5 were used to obtain and analysis the data.

RESULTS

A total of 32 original studies covering 15,583 patients were included. In our data, it indicated that high level of PRMT5 was significantly correlated with advanced tumor stage (OR = 2.12, 95% CI: 1.22-3.70, P =.008; I2 = 80.7%) and positively correlated with poor overall survival (HR = 1.59, 95% CI: 1.46-1.73, P < .001; I2 = 50%) and progression-free survival (HR = 1.53, 95% CI: 1.24-1.88, P < .001; I2 = 0%). In addition, sub-group analysis showed that high level of PRMT5 was associated with poor overall survival for such 5 kinds of cancers as hepatocellular carcinoma, pancreatic cancer, breast cancer, gastric cancer, and lung cancer.

CONCLUSION

For the first time we found PRMT5 was pan-cancerous as a prognostic biomarker and high level of PRMT5 was associated with poor prognosis for certain cancers.

Genetic Engineering of Zebrafish in Cancer Research

Zebrafish (Danio rerio) is an excellent model to study a wide diversity of human cancers. In this review, we provide an overview of the genetic and reverse genetic toolbox allowing the generation of zebrafish lines that develop tumors. The large spectrum of genetic tools enables the engineering of zebrafish lines harboring precise genetic alterations found in human patients, the generation of zebrafish carrying somatic or germline inheritable mutations or zebrafish showing conditional expression of the oncogenic mutations. Comparative transcriptomics demonstrate that many of the zebrafish tumors share molecular signatures similar to those found in human cancers. Thus, zebrafish cancer models provide a unique in vivo platform to investigate cancer initiation and progression at the molecular and cellular levels, to identify novel genes involved in tumorigenesis as well as to contemplate new therapeutic strategies.

Prognostic value of Iroquois homeobox 1 methylation in non-small cell lung cancers

BACKGROUND

Non-small cell lung cancer (NSCLC) poses a great threat to human health. DNA methylation abnormalities play a central role in the development and outcome of most human malignancies, providing potential biomarkers for diagnosis and prognosis. Iroquois homeobox 1 (IRX1) can act as a tumor suppressor or promoter depending on the tumor microenvironment, and its role in lung cancer is still controversial.

OBJECTIVE

The purpose of this study was to investigate the biological role and prognostic value of IRX1 in NSCLC.

METHODS

We examined the methylation status of IRX1 promoter in 146 tumors from patients with NSCLC using pyrosequencing and analyzed the association between methylation status and overall patient survival.

RESULTS

A total of 37 cases (25.3%) showed IRX1 methylation-positive tumors when compared with matched normal tissues. No association between IRX1 expression level and methylation status was found in lung cancer cell lines. IRX1 methylation significantly correlated with smoking status and TP53 mutation. Patients with IRX1 methylation showed significantly longer survival than patients without methylation (log-rank P = 0.011). In a multivariate analysis of prognostic factors, IRX1 methylation in tumor samples was an independent prognostic factor (adjusted hazard ratio = 0.35, 95% confidence interval 0.17-0.73, P = 0.005).

CONCLUSION

These results suggest that IRX1 promoter methylation may be a tumor-associated event and an independent predictor of survival advantage in patients with NSCLC. Further large-scale studies are needed to confirm these findings.

PRMT5-dependent transcriptional repression of c-Myc target genes promotes gastric cancer progression

The proto-oncogene c-Myc regulates multiple biological processes mainly through selectively activating gene expression. However, the mechanisms underlying c-Myc-mediated gene repression in the context of cancer remain less clear. This study aimed to clarify the role of PRMT5 in the transcriptional repression of c-Myc target genes in gastric cancer.

Methods: Immunohistochemistry was used to evaluate the expression of PRMT5, c-Myc and target genes in gastric cancer patients. PRMT5 and c-Myc interaction was assessed by immunofluorescence, co-immunoprecipitation and GST pull-down assays. Bioinformatics analysis, immunoblotting, real-time PCR, chromatin immunoprecipitation, and rescue experiments were used to evaluate the mechanism.

Results: We found that c-Myc directly interacts with protein arginine methyltransferase 5 (PRMT5) to transcriptionally repress the expression of a cohort of genes, including PTEN, CDKN2C (p18^INK4C), CDKN1A (p21^CIP1/WAF1), CDKN1C (p57^KIP2) and p63, to promote gastric cancer cell growth. Specifically, we found that PRMT5 was required to promote gastric cancer cell growth in vitro and in vivo, and for transcriptional repression of this cohort of genes, which was dependent on its methyltransferase activity. Consistently, the promoters of this gene cohort were enriched for both PRMT5-mediated symmetric di-methylation of histone H4 on Arg 3 (H4R3me2s) and c-Myc, and c-Myc depletion also upregulated their expression. H4R3me2s also colocalized with the c-Myc-binding E-box motif (CANNTG) on these genes. We show that PRMT5 directly binds to c-Myc, and this binding is required for transcriptional repression of the target genes. Both c-Myc and PRMT5 expression levels were upregulated in primary human gastric cancer tissues, and their expression levels inversely correlated with clinical outcomes.

Conclusions: Taken together, our study reveals a novel mechanism by which PRMT5-dependent transcriptional repression of c-Myc target genes is required for gastric cancer progression, and provides a potential new strategy for therapeutic targeting of gastric cancer.

Downregulated microRNA-150 upregulates IRX1 to depress proliferation, migration, and invasion, but boost apoptosis of gastric cancer cells

OBJECTIVE

Many studies have reported the correlation of microRNAs (miRNAs) with cancers, yet few have proposed the function of miR-150 in gastric cancer. This study intends to discuss the role of miR-150 in gastric cancer development by regulating IRX1.

METHODS

Gastric cancer tissues and adjacent tissues were collected. MiR-150-3p, IRX1, CXCL14, and NF-κB (p65) expressions were detected. Gastric cancer cell lines SNU-1 and MKN-45 were used for subsequent cellular experiments. Cell proliferation, colony formation, migration and invasion, apoptosis, and cell cycle distribution in SNU-1 and MKN-45 cells were determined via gain-of and loss-of-function assays. The tumor growth in nude mice was also detected.

RESULTS

MiR-150, CXCL14, and NF-κB (p65) were upregulated and IRX1 was downregulated in gastric cancer tissues and cells. CXCL14 and NF-κB (p65) expression was positively related to miR-150 expression and negatively to IRX1 expression. MiR-150 inhibition and IRX1 overexpression in SNU-1 cells restricted viability, colony formation, migration, and invasion abilities, but boosted apoptosis of gastric cancer cells in vitro, and also repressed tumor growth in vivo. These results could be reversed by miR-150 elevation and IRX1 silencing, and the results from in vivo and in vitro experiments were consistent.

CONCLUSION

Our study reveals that miR-150 downregulation restrains proliferation, migration, and invasion, while facilitating apoptosis of gastric cancer cells by upregulating IRX1.

IRX1 hypermethylation promotes heart failure by inhibiting CXCL14 expression

To identify the mechanism and functions of IRX1 in heart failure (HF) and provide evidence for new therapies. Bioinformatic analysis was performed to select target genes in HF cells compared to normal groups. Experimental rats were treated in a controllable manner to explore how IRX1 methylation accounted for this disease in vivo. Cardiac ultrasonic and morphologic examinations were conducted to test the mouse heart and evaluate the degree of cardiac impairment at in the level of organization. GSEA analysis revealed the relative enrichment of functions. Immunofluorescent assays, western blotting and qRT-PCR were used to determine the DNA methylation and expression levels. IRX1 was hypermethylated in heart failure and identified as a target gene by bioinformatic analysis. Transverse aortic constriction (TAC) induced heart failure in rats, while 5-aza-2'-deoxycytidine (5-Aza) alleviated heart failure in rats according to medical cardiac indexes. Western blotting and qRT-PCR revealed that a conspicuous difference in the expression of IRX1 and CXCL14 between HF and normal cardiac cells. As a result of gene methylation, left ventricular hypertrophy and cardiac fibrosis is usually accompanied by heart failure. Moreover, is the results implied that the demethylation of IRX1 improves heart failure in vivo and in vitro. IRX1 methylation induced damaged cardiac function and even heart failure, which has important implications for HF treatment and diagnosis.

Epigenetic regulation of IncRNA KCNKI5-ASI in gastric cancer

Background

Long noncoding RNAs (lncRNAs) play an important role in gastric cancer. In this study, we aimed to uncover the epigenetic regulatory mechanism of lncRNA KCNK15-AS1 in gastric cancer progression.

Patients and methods

Forty patients were included in the study. The expression of KCNK15-AS1 was detected by real-time PCR (RT-PCR), the promoter of KCNK15-AS1 was detected by methylation-specific PCR, and the luciferase assay was performed to detect the relationship between KCNK15-AS1 and miR-21. The relationship of the proteins was explored by an RNA pull-down assay and RNA immunoprecipitation. Chromatin immunoprecipitation was performed to detect the relationship between the promoter and the protein.

Results

The expression of KCNK15-AS1 was lower in the tumor tissue compared to the normal tissue. KCNK15-AS1 interacted with miR-21. Both the overexpression of KCNK15-AS1 and the knockdown of the expression of miR-21 inhibited proliferation and promoted apoptosis and decreased the level of MMP-9, bcl-2, and MMP-2 but increased the level of Bax. In addition, the methylation of KCNK15-AS1 was detected in the tumor tissue but was not detected in the normal tissue. Treatment with 5-azacytidine and chidamide decreased the level of DNMT1 and HDAC1 and increased the level of KCNK15-AS1. The RNA pull-down and RNA immunoprecipitation results showed that KCNK15-AS1 interacted with DNMT1 and HDAC1. The ChIP-seq result showed that the promoter of MAPK interacted with DNMT1, and the promoter of AKT and STAT5 interacted with HDAC1.

Conclusion

In this study, we identified two regulatory axes, namely KCNK15-AS1-DNMT1-MAPK and KCNK15-AS1-HDAC1-AKT, which were associated with gastric cancer progression. Chidamide and 5-azacytidine might provide new modes for treating gastric cancer.

Iroquois Homeobox 1 Acts as a True Tumor Suppressor in Multiple Organs by Regulating Cell Cycle Progression

Iroquois homeobox 1 (IRX1) belongs to the Iroquois homeobox family known to play an important role during embryonic development. Interestingly, however, recent studies have suggested that IRX1 also acts as a tumor suppressor. Here, we use homozygous knockout mutants of zebrafish to demonstrate that the IRX1 gene is a true tumor suppressor gene and mechanism of the tumor suppression is mediated by repressing cell cycle progression. In this study, we found that knockout of zebrafish Irx1 gene induced hyperplasia and tumorigenesis in the multiple organs where the gene was expressed. On the other hands, overexpression of the IRX1 gene in human tumor cell lines showed delayed cell proliferation of the tumor cells. These results suggest that the IRX1 gene is truly involved in tumor suppression. In an attempt to identify the genes regulated by the transcription factor IRX1, we performed microarray assay using the cRNA obtained from the knockout mutants. Our result indicated that the highest fold change of the differential genes fell into the gene category of cell cycle regulation, suggesting that the significant canonical pathway of IRX1 in antitumorigenesis is done by regulating cell cycle. Experiment with cell cycle blockers treated to IRX1 overexpressing tumor cells showed that the IRX1 overexpression actually delayed the cell cycle. Furthermore, Western blot analysis with cyclin antibodies showed that IRX1 overexpression induced decrease of cyclin production in the cancer cells. In conclusion, our in vivo and in vitro studies revealed that IRX1 gene functionally acts as a true tumor suppressor, inhibiting tumor cell growth by regulating cell cycle.

Epigenetic response profiles into environmental epigenotoxicant screening and health risk assessment: A critical review

The epigenome may be an important interface between exposure to environmental contaminants and adverse outcome on human health. Many environmental pollutants deregulate gene expression and promote diseases by modulating the epigenome. Adverse epigenetic responses have been widely used for risk assessment of chemical substances. Various pollutants, including trace elements and persistent organic pollutants, have been detected frequently in the environment. Epigenetic toxicity of environmental matrices including water, air, soil, and food cannot be ignored. This review provides a comprehensive overview of epigenetic effects of pollutants and environmental matrices. We start with an overview of the mechanisms of epigenetic regulation and the effects of several types of environmental pollutants (trace elements, persistent organic pollutants, endocrine disrupting chemicals, and volatile organic pollutants) on epigenetic modulation. We then discuss the epigenetic responses to environmental water, air, and soil based on in vivo and in vitro assays. Finally, we discuss recommendations to promote the incorporation of epigenotoxicity into contamination screening and health risk assessment.

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.

NF-κB/mTOR/MYC Axis Drives PRMT5 Protein Induction After T Cell Activation via Transcriptional and Non-transcriptional Mechanisms

Multiple sclerosis is an autoimmune disease of the central nervous system (CNS) mediated by CD4+ T cells and modeled via experimental autoimmune encephalomyelitis (EAE). Inhibition of PRMT5, the major Type II arginine methyltransferase, suppresses pathogenic T cell responses and EAE. PRMT5 is transiently induced in proliferating memory inflammatory Th1 cells and during EAE. However, the mechanisms driving PRMT5 protein induction and repression as T cells expand and return to resting is currently unknown. Here, we used naive mouse and memory mouse and human Th1/Th2 cells as models to identify mechanisms controlling PRMT5 protein expression in initial and recall T cell activation. Initial activation of naive mouse T cells resulted in NF-κB-dependent transient Prmt5 transcription and NF-κB, mTOR and MYC-dependent PRMT5 protein induction. In murine memory Th cells, transcription and miRNA loss supported PRMT5 induction to a lesser extent than in naive T cells. In contrast, NF-κB/MYC/mTOR-dependent non-transcriptional PRMT5 induction played a major role. These results highlight the importance of the NF-κB/mTOR/MYC axis in PRMT5-driven pathogenic T cell expansion and may guide targeted therapeutic strategies for MS.

Regulation of fibroblast-like synoviocyte transformation by transcription factors in arthritic diseases

Inflammation in the synovium is known to mediate joint destruction in several forms of arthritis. Fibroblast-like synoviocytes (FLS) are cells that reside in the synovial lining of joints and are known to be key contributors to inflammation associated with arthritis. FLS are a major source of inflammatory cytokines and catabolic enzymes that promote joint degeneration. We now know that there exists a direct correlation between the signaling pathways that are activated by the pro-inflammatory molecules produced by the FLS, and the severity of joint degeneration in arthritis. Research focused on understanding the signaling pathways that are activated by these pro-inflammatory molecules has led to major advancements in the understanding of the joint pathology in arthritis. Transcription factors (TFs) that act as downstream mediators of the pro-inflammatory signaling cascades in various cell types have been reported to play an important role in inducing the deleterious transformation of the FLS. Interestingly, recent studies have started uncovering that several TFs that were previously reported to play role in embryonic development and cancer, but not known to have pronounced roles in tissue inflammation, can actually play crucial roles in the regulation of the pathological properties of the FLS. In this review, we will discuss reports that have been able to impart novel arthritogenic roles to TFs that are specialized in embryonic development. We also discuss the therapeutic potential of targeting these newly identified regulators of FLS transformation in the treatment of arthritis.

Protein arginine methyltransferase 5 (PRMT5) dysregulation in cancer

Protein arginine methyltransferases (PRMTs) are known for their ability to catalyze methylation of specific arginine residues in a wide variety of cellular proteins, which are involved in a plethora of processes including signal transduction, transcription, and more recently DNA recombination. All members of the PRMT family can be grouped into three main classes depending on the type of methylation they catalyze. Type I PRMTs induce monomethylation and asymmetric dimethylation, while type II PRMTs catalyze monomethylation and symmetric dimethylation of specific arginine residues. In contrast, type III PRMTs carry out only monomethylation of arginine residues. In this review, we will focus on PRMT5, a type II PRMT essential for viability and normal development, which has been shown to be overexpressed in a wide variety of cancer cell types, owing it to the crucial role it plays in controlling key growth regulatory pathways. Furthermore, the role of PRMT5 in regulating expression and stability of key transcription factors that control normal stem cell function as well as cancer stem cell renewal will be discussed. We will review recent work that shows that through its ability to methylate various cellular proteins, PRMT5 functions as a master epigenetic regulator essential for growth and development, and we will highlight studies that have examined its dysregulation and the effects of its inhibition on cancer cell growth.