RNA Editing Enzyme ADAR1 Regulates METTL3 in an Editing Dependent Manner to Promote Breast Cancer Progression via METTL3/ARHGAP5/YTHDF1 Axis

Transcription factor KLF5 regulates MsrB1 to promote colorectal cancer progression by inhibiting ferroptosis through β-catenin

Methionine sulfoxide reductase B1 (MsrB1), a member of the selenoprotein family with a catalytic site containing a selenocysteine (Sec) residue, has been identified as an oncogene in colorectal cancer (CRC). However, the regulatory mechanisms of MsrB1 and the relationship between its oncogenic role and antioxidant capacity are not well understood. In this study, we show that either overexpression or suppression of MsrB1 in CRC cells leads to significant phenotypic changes, confirming its role in oncogenesis. To explore the molecular regulatory mechanisms of MsrB1, we used bioinformatic analyses to predict transcription factors within its promoter region, and validated these predictions using dual-luciferase reporter and chromatin immunoprecipitation (ChIP) assays. These assays revealed that Krüppel-like factor 5 (KLF5), acting as a transcription factor, binds to the MsrB1 promoter and activates it. Additionally, through Weighted Gene Co-expression Network Analysis (WGCNA) and Co-IP experimental validation, we identified β-catenin, a key component of the Wnt signaling pathway, as being co-expressed with MsrB1. The interaction between MsrB1 and β-catenin leads to the activation of GPX4 transcription, a known ferroptosis marker, which results in the inhibition of ferroptosis and promotion of oncogenesis in CRC. In conclusion, this study elucidates the transcriptional regulatory mechanism of MsrB1 and its role in inhibiting ferroptosis in conjunction with β-catenin. These findings suggest that MsrB1 may be a promising predictive biomarker and therapeutic target for CRC, extending its role beyond that of a conventional antioxidant selenoprotein.

Immunomodulatory role of RNA modifications in sex hormone-dependent cancers

Recent studies have identified that RNA epigenetic modifications, including m6A, m1A, m5C, etc, play pivotal roles in tumor progression. These modifications influence mRNA stability, RNA processing, translational efficiency, and decoding precision. However, comprehensive reviews detailing the connection between m6A RNA modifications and hormone-dependent cancers in both male and female populations remain scarce(breast cancer, ovarian cancer, and endometrial cancer, prostate cancer). In this article, we explore the cellular and molecular roles of various RNA modifications alongside the key elements of the tumor microenvironment. We examine how these RNA modifications influence the development of hormone-dependent cancers through their impact on immune mechanisms. By enhancing our understanding of the function of RNA modifications within the immune systems of four specific tumors, we offer fresh insights for their potential applications in diagnosis and treatment.

Silencing LINC01547 induces hepatocellular carcinoma cell apoptosis and metastasis inhibition via the ADAR1/FAK and miR-146b-5p/RAC1 axes

Growing research indicates that long noncoding RNAs (lncRNAs) are pivotal in the development and advancement of hepatocellular carcinoma (HCC). Our research pinpointed LINC01547 as a notable lncRNA that was significantly downregulated in Hep3B cells treated with bufotalin, whereas it exhibited elevated expression levels in HCC tumor tissues. Further study found that silencing LINC01547 markedly suppressed proliferation, induced apoptosis, and inhibited migration and invasion in Hep3B and HepG2 cells. LINC01547 knockdown reduced ADAR1 expression, which led to apoptosis and suppressed metastasis via inhibition of the FAK signaling pathway. Additionally, silencing LINC01547 upregulated miR-146b-5p, which in turn decreased RAC1 levels, further promoting apoptosis and inhibiting metastasis in HCC cells. In vivo, a Hep3B tumor-bearing mouse model confirmed the antitumor effects of LINC01547 silencing. Our findings demonstrate that LINC01547 regulates HCC cell apoptosis and metastasis through the ADAR1/FAK and miR-146b-5p/RAC1 pathways, suggesting that LINC01547 may serve as a biomarker and potential therapeutic target for HCC.

Global analysis by LC-MS/MS of N6-methyladenosine and inosine in mRNA reveal complex incidence

The precise and unambiguous detection and quantification of internal RNA modifications represents a critical step for understanding their physiological functions. The methods of direct RNA sequencing are quickly developing allowing for the precise location of internal RNA marks. This detection is, however, not quantitative and still presents detection limits. One of the biggest remaining challenges in the field is still the detection and quantification of m6A, m6Am, inosine, and m1A modifications of adenosine. The second intriguing and timely question remaining to be addressed is the extent to which individual marks are coregulated or potentially can affect each other. Here, we present a methodological approach to detect and quantify several key mRNA modifications in human total RNA and in mRNA, which is difficult to purify away from contaminating tRNA. We show that the adenosine demethylase FTO primarily targets m6Am marks in noncoding RNAs in HEK293T cells. Surprisingly, we observe little effect of FTO or ALKBH5 depletion on the m6A mRNA levels. Interestingly, the upregulation of ALKBH5 is accompanied by an increase in inosine level in overall mRNA.

STM2457 impairs the proliferation of esophageal squamous cell carcinoma by activating DNA damage response through ATM-Chk2 axis

METTL3 has been proven to play an important role in the proliferation of Esophageal squamous cell carcinoma (ESCC). In this study, we focused on investigating the therapeutic role and molecular mechanism of STM2457 in ESCC, which is a novel small-molecule inhibitor of METTL3. The effect of STM2457 on ESCC was evaluated using ESCC cell lines by the cell viability measurement, cloning formation assay, scratching assay, transwell assay, and flow cytometry techniques. Furthermore, the molecular mechanism study was employed to evaluate by RT-qPCR, Western blotting, proteomics analysis, comet assay, etc. Additionally, the anticancer effect of STM2457 was carried out by nude mice tumor xenograft in vivo. This study showed STM2457 could significantly inhibit the proliferation and migration of Eca109 and KYSE150 cells, which promoted G0/G1 phase arrest and apoptosis in a dose-dependent manners in vitro. Moreover, proteomics analysis suggested the important role of ATM in action mechanism of STM2457. Further studies showed that STM2457 may activate DNA damage response and the expression of ATM, p-ATM, p-Chk2, and γ-H2AX protein in ATM-Chk2 pathway. Intriguingly, ATM inhibitor CGK-733 and knocking down ATM significantly reduced the expression of ATM in Eca109 and KYSE150 cells treated with STM2457. Importantly, STM2457 significantly upregulated the expression of ATM and γ-H2AX protein and inhibited the growth of ESCC in vivo. Finally, STM2457 combined with PTX could also significantly inhibit the proliferation and migration ability of Eca109 and KYSE150 cells by targeting the ATM-mediated DDR pathway. In tumor-bearing nude mice model, STM2457 combined with Paclitaxel can inhibit the growth of ESCC and increased the expression of ATM and γ-H2AX protein. These findings revealed ATM-Chk2 pathway is a promising therapeutic target for STM2457 to effectively inhibit the proliferation of ESCC.

Unveiling the prognostic significance of RNA editing-related genes in colon cancer: evidence from bioinformatics and experiment

BACKGROUND

RNA editing is recognized as a crucial factor in cancer biology. Its potential application in predicting the prognosis of colon adenocarcinoma (COAD) remains unexplored.

METHODS

RNA editing data of COAD patients were downloaded from the Synapse database. LASSO regression was used to construct the risk model and verified by the receiver operating characteristic (ROC) curve. GO and KEGG enrichment analyses were performed to delineate the biological significance of the differentially expressed genes. Finally, differential analysis and immunohistochemistry were used to verify the expression of adenosine deaminase 1 (ADAR1).

RESULTS

We evaluated a total of 4079 RNA editing sites in 514 COAD patients from Synapse database. A prognostic signature was constructed based on five genes were significantly associated with the prognosis of COAD patients including GNL3L, NUP43, MAGT1, EMP2, and ARSD. Univariate and multivariate Cox regression analysis revealed that RNA editing-related genes (RERGs)-related signature was an independent risk factor for COAD. Moreover, Experimental evidence shows that ADAR1 is highly expressed in colon adenocarcinoma and silencing ADAR1 can inhibit cancer cell proliferation.

CONCLUSION

We established a prognostic model based on five RERGs with strong predictive value. This model not only serves as a foundation for a novel prognostic tool but also facilitates the identification of potential drug candidates for treating COAD.

Advances in A-to-I RNA editing in cancer

RNA modifications are widespread throughout the mammalian transcriptome and play pivotal roles in regulating various cellular processes. These modifications are strongly linked to the development of many cancers. One of the most prevalent forms of RNA modifications in humans is adenosine-to-inosine (A-to-I) editing, catalyzed by the enzyme adenosine deaminase acting on RNA (ADAR) in double-stranded RNA (dsRNA). With advancements in RNA sequencing technologies, the role of A-to-I modification in cancer has garnered increasing attention. Research indicates that the levels and specific sites of A-to-I editing are significantly altered in many malignant tumors, correlating closely with tumor progression. This editing occurs in both coding and noncoding regions of RNA, influencing signaling pathways involved in cancer development. These modifications can either promote or suppress cancer progression through several mechanisms, including inducing non-synonymous amino acid mutations, altering the immunogenicity of dsRNAs, modulating mRNA interactions with microRNAs (miRNAs), and affecting the splicing of circular RNAs (circRNAs) as well as the function of long non-coding RNAs (lncRNAs). A comprehensive understanding of A-to-I RNA editing is crucial for advancing the diagnosis, treatment, and prognosis of human cancers. This review explores the regulatory mechanisms of A-to-I editing in cancers and examines their potential clinical applications. It also summarizes current research, identifies future directions, and highlights potential therapeutic implications.

ZFHX2-AS1 interacts with DKC1 to regulate ARHGAP5 pseudouridylation and suppress ovarian cancer progression

Ovarian cancer (OCa) remains a highly lethal disease, largely due to late-stage diagnosis and limited treatment options for recurrent metastatic tumors. Long non-coding RNAs (lncRNAs) have been recognized as key regulators of cancer hallmarks, yet their specific roles in driving OCa progression are not fully understood. In this study, we employed an integrated approach combining clinical correlation, functional assays, and mechanistic investigations to reveal that lncRNA ZFHX2-AS1 is significantly downregulated in OCa tissues and cells, with its reduced expression associated with poor clinical outcomes. Using in vitro and in vivo models, we demonstrated that overexpression of ZFHX2-AS1 suppresses OCa cell proliferation, migration and invasion, whereas ZFHX2-AS1 knockdown enhances these malignant phenotypes. Mechanistically, we defined that ZFHX2-AS1 interacts with and attenuates the enzymatic activity of the pseudouridine synthase DKC1, thereby reducing pseudouridylation and stabilizing the oncogenic ARHGAP5 mRNA. Re-expression of ARHGAP5 could partially reverse the tumor-suppressive effects of ZFHX2-AS1. Further, we found that ARHGAP5 promotes epithelial-mesenchymal transition (EMT) by regulating Rho GTPases activities, and that ZFHX2-AS1 inhibits EMT in OCa by downregulating ARHGAP5 expression and suppressing the Rho GTPase signaling pathway. Taken together, our findings identify ZFHX2-AS1 as a potent tumor suppressor in OCa, acting through the modulation of DKC1-mediated pseudouridylation of ARHGAP5 and the inhibition of the Rho GTPase pathway, thus offering a potential therapeutic target for combating OCa progression.

N6-Methyladenosine methylation modification in breast cancer: current insights

Breast cancer is the most common cancer type among women. Despite advanced treatment strategies, some patients still face challenges in disease control, prompting the exploration of new therapeutic approaches. N6-Methyladenosine (m6A) methylation modification regulates RNA and plays a crucial role in various tumor biological processes, closely linked to breast cancer occurrence, development, prognosis, and treatment. M6A regulators impact breast cancer progression, development, and drug resistance by modulating RNA metabolism and tumor-related pathways. Researchers have begun to understand the regulatory mechanisms of m6A methylation in breast cancer. This paper discusses the roles of m6A regulators in breast cancer progression, prognosis, and treatment, offering new perspectives for breast cancer diagnosis and treatment.

ADAR promotes USP38 auto-deubiquitylation and stabilization in an RNA editing-independent manner in esophageal squamous cell carcinoma

Esophageal cancer is mainly divided into esophageal adenocarcinoma and esophageal squamous cell carcinoma (ESCC). China is one of the high-incidence areas of esophageal cancer, of which about 90% are ESCC. The deubiquitinase USP38 has been reported to play significant roles in several biological processes, including inflammatory responses, antiviral infection, cell proliferation, migration, invasion, DNA damage repair, and chemotherapy resistance. However, the role and mechanisms of USP38 in ESCC development remain still unclear. Furthermore, although many substrates of USP38 have been identified, few upstream regulatory factors of USP38 have been identified. In this study, we found that USP38 was significantly upregulated in esophageal cancer tissues. Knockdown of USP38 inhibited ESCC growth. USP38 stabilized itself through auto-deubiquitylation. In addition, we demonstrate that adenosine deaminase acting on RNA (ADAR) could enhance the stability of USP38 protein and facilitate USP38 auto-deubiquitylation by interacting with USP38 in an RNA editing-independent manner. ADAR inhibition of ESCC cell proliferation depended on USP38. In summary, these results highlight that the potential of targeting the ADAR-USP38 axis for ESCC treatment.

Loss of ADAR1 induces ferroptosis of breast cancer cells

Adenosine deaminases acting on RNA 1(ADAR1), an RNA editing enzyme that converts adenosine to inosine by deamination in double-stranded RNAs, plays an important role in occurrence and progression of various types of cancer. Ferroptosis has emerged as a hot topic of cancer research in recent years. We have previously reported that ADAR1 promotes breast cancer progression by regulating miR-335-5p and METTL3. However, whether ADAR1 has effects on ferroptosis in breast cancer cells is largely unknown. In this study, we knocked down ADAR1 using CRISPR-Cas9 technology or over-expressed ADAR1 protein using plasmid expressing ADAR1 in MCF-7 and MDA-MB-231 breast cancer cell lines, then detected cell viability, and levels of ROS, MDA, GSH, Fe2+, GPX4 protein and miR-335-5p. We showed that the cell proliferation was inhibited, levels of ROS, MDA, Fe2+, and miR-335-5p were increased, while GSH and GPX4 levels were decreased after loss of ADAR1, compared to the control group. The opposite effects were observed after ADAR1 overexpression in the cells. Further, we demonstrated that ADAR1-controlled miR-335-5p targeted Sp1 transcription factor of GPX4, a known ferroptosis molecular marker, leading to inhibition of ferroptosis by ADAR1 in breast cancer cells. Moreover, RNA editing activity of ADAR1 is not essential for inducing ferroptosis. Collectively, loss of ADAR1 induces ferroptosis in breast cancer cells by regulating miR-335-5p/Sp1/GPX4 pathway. The findings may provide insights into the mechanism by which ADAR1 promotes breast cancer progression via inhibiting ferroptosis.

Prognostic analysis and risk assessment based on RNA editing in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related mortality, and prognosis assessment is crucial for guiding treatment decisions. In this study, we aimed to develop a personalized prognostic model for HCC based on RNA editing. RNA editing is a post-transcriptional process that can affect gene expression and, in some cases, play a role in cancer development. By analyzing RNA editing sites in HCC, we sought to identify a set of sites associated with patient prognosis and use them to create a prognostic model. We gathered RNA editing data from the Synapse database, comprising 9990 RNA editing sites and 250 HCC samples. Additionally, we collected clinical data for 377 HCC patients from the Cancer Genome Atlas (TCGA) database. We employed a multi-step approach to identify prognosis-related RNA editing sites (PR-RNA-ESs). We assessed how patients in the high-risk and low-risk groups, as defined by the model, fared in terms of survival. A nomogram was developed to predict the precise survival prognosis of HCC patients and assessed the prognostic model's utility through a receiver operating characteristic (ROC) analysis and decision curve analysis (DCA). Our analysis identified 33 prognosis-related RNA editing sites (PR-RNA-ESs) associated with HCC patient prognosis. Using a combination of LASSO regression and cross-validation, we constructed a prognostic model based on 13 PR-RNA-ESs. Survival analysis demonstrated significant differences in the survival outcomes of patients in the high-risk and low-risk groups defined by this model. Additionally, the differential expression of the 13 PR-RNA-ESs played a role in shaping patient survival. Risk-prognostic investigations further distinguished patients based on their risk levels. The nomogram enabled precise survival prognosis prediction. Our study has successfully developed a highly personalized and accurate prognostic model for individuals with HCC, leveraging RNA editing data. This model has the potential to revolutionize clinical evaluation and medical management by providing individualized prognostic information. The identification of specific RNA editing sites associated with HCC prognosis and their incorporation into a predictive model holds promise for improving the precision of treatment strategies and ultimately enhancing patient outcomes in HCC.

Adenosine-to-Inosine RNA editing in cancer: molecular mechanisms and downstream targets

Adenosine-to-Inosine (A-to-I), one of the most prevalent RNA modifications, has recently garnered significant attention. The A-to-I modification actively contributes to biological and pathological processes by affecting the structure and function of various RNA molecules, including double stranded RNA, transfer RNA, microRNA, and viral RNA. Increasing evidence suggests that A-to-I plays a crucial role in the development of human disease, particularly in cancer, and aberrant A-to-I levels are closely associated with tumorigenesis and progression through regulation of the expression of multiple oncogenes and tumor suppressor genes. Currently, the underlying molecular mechanisms of A-to-I modification in cancer are not comprehensively understood. Here, we review the latest advances regarding the A-to-I editing pathways implicated in cancer, describing their biological functions and their connections to the disease.

Functions of methyltransferase-like 3 in breast cancer: pathogenesis, drug resistance, and therapeutic target

Breast cancer (BC) is a highly prevalent malignancy worldwide, with complex pathogenesis and treatment challenges. Research reveals that methyltransferase-like 3 (METTL3) is widely involved in the pathogenesis of several tumors through methylation of its target RNAs, and its role and mechanisms in BC are also extensively studied. In this review, we aim to provide a comprehensive interpretation of available studies and elucidate the relationship between METTL3 and BC. This review suggests that high levels of METTL3 are associated with the pathogenesis, poor prognosis, and drug resistance of BC, suggesting METTL3 as a potential diagnostic or prognostic biomarker and therapeutic target. Collectively, this review provides a comprehensive understanding of how METTL3 functions through RNA methylation, which provides a valuable reference for future fundamental studies and clinical applications.

Molecular mechanisms of non-genetic aberrant peptide production in cancer

The cancer peptidome has long been known to be altered by genetic mutations. However, more recently, non-genetic polypeptide mutations have also been related to cancer cells. These non-genetic mutations occur post-t30ranscriptionally, leading to the modification of the peptide primary structure, while the corresponding genes remain unchanged. Three main processes participate in the production of these aberrant proteins: mRNA alternative splicing, mRNA editing, and mRNA aberrant translation. In this review, we summarize the molecular mechanisms underlying these processes and the recent findings on the functions of the aberrant proteins, as well as their exploitability as new therapeutic targets due to their specific enrichment in cancer cells. These non-genetic aberrant polypeptides represent a source of novel cancer cell targets independent from their level of mutational burden, still to be exhaustively explored.

Epitranscriptomic orchestrations: Unveiling the regulatory paradigm of m6A, A-to-I editing, and m5C in breast cancer via long noncoding RNAs and microRNAs

Breast cancer (BC) poses a persistent global health challenge, particularly in countries with elevated human development indices linked to factors such as increased life expectancy, education, and wealth. Despite therapeutic progress, challenges persist, and the role of epitranscriptomic RNA modifications in BC remains inadequately understood. The epitranscriptome, comprising diverse posttranscriptional modifications on RNA molecules, holds the potential to intricately modulate RNA function and regulation, implicating dysregulation in various diseases, including BC. Noncoding RNAs (ncRNAs), acting as posttranscriptional regulators, influence physiological and pathological processes, including cancer. RNA modifications in long noncoding RNAs (lncRNAs) and microRNAs (miRNAs) add an extra layer to gene expression control. This review delves into recent insights into epitranscriptomic RNA modifications, such as N-6-methyladenosine (m6A), adenine-to-inosine (A-to-I) editing, and 5-methylcytosine (m5C), specifically in the context of lncRNA and miRNAs in BC, highlighting their potential implications in BC development and progression. Understanding this intricate regulatory landscape is vital for deciphering the molecular mechanisms underlying BC and identifying potential therapeutic targets.

YTHDF1 enhances stemness and chemoresistance in triple-negative breast cancer cells by upregulating SIAH2

Triple-negative breast cancer (TNBC) is the most lethal and aggressive subtype of breast cancer, and chemoresistance is the major determinant of TNBC treatment failure. This study explores the molecular mechanism of TNBC chemoresistance. The Cancer Genome Atlas, breast cancer integrative platform, and GEPIA databases were used to analyze the expression and correlation of YTHDF1 and seven in absentia homology 2 (SIAH2) in breast cancer. Knockdown of YTHDF1 and SIAH2, or overexpression of SIAH2 in vitro and in vivo, was conducted to evaluate the impact of changes in YTHDF1 and SIAH2 expression on TNBC cell proliferation, apoptosis, stemness, drug resistance, and Hippo pathway gene expression. YTHDF1 and SIAH2 were highly expressed in breast cancer patients and TNBC cells. Knockdown of YTHDF1 and SIAH2 significantly inhibited proliferation and stemness and promoted apoptosis and chemosensitivity of TNBC cells. Mechanistically, the knockdown of YTHDF1 inhibited the expression of SIAH2, thereby downregulating the Hippo pathway, which inhibited proliferation and stemness and promoted apoptosis and chemosensitivity of TNBC cells. The current findings revealed the regulatory mechanism of YTHDF1 in TNBC and clarified the role of the YTHDF1/SIAH2 axis in TNBC drug resistance and stemness. This could provide new insights into the vital role of targeting YTHDF1/SIAH2 to suppress drug resistance and stemness in TNBC cells.

The role of ADAR1 through and beyond its editing activity in cancer

Adenosine-to-inosine (A-to-I) editing of RNA, catalyzed by adenosine deaminase acting on RNA (ADAR) enzymes, is a prevalent RNA modification in mammals. It has been shown that A-to-I editing plays a critical role in multiple diseases, such as cardiovascular disease, neurological disorder, and particularly cancer. ADARs are the family of enzymes, including ADAR1, ADAR2, and ADAR3, that catalyze the occurrence of A-to-I editing. Notably, A-to-I editing is mainly catalyzed by ADAR1. Given the significance of A-to-I editing in disease development, it is important to unravel the complex roles of ADAR1 in cancer for the development of novel therapeutic interventions.In this review, we briefly describe the progress of research on A-to-I editing and ADARs in cancer, mainly focusing on the role of ADAR1 in cancer from both editing-dependent and independent perspectives. In addition, we also summarized the factors affecting the expression and editing activity of ADAR1 in cancer.

The role of dsRNA A-to-I editing catalyzed by ADAR family enzymes in the pathogeneses

The process of adenosine deaminase (ADAR)-catalyzed double-stranded RNA (dsRNA) Adenosine-to-Inosine (A-to-I) editing is essential for the correction of pathogenic mutagenesis, as well as the regulation of gene expression and protein function in mammals. The significance of dsRNA A-to-I editing in disease development and occurrence is explored using inferential statistics and cluster analyses to investigate the enzymes involved in dsRNA editing that can catalyze editing sites across multiple biomarkers. This editing process, which occurs in coding or non-coding regions, has the potential to activate abnormal signalling pathways that contributes to disease pathogenesis. Notably, the ADAR family enzymes play a crucial role in initiating the editing process. ADAR1 is upregulated in most diseases as an oncogene during tumorigenesis, whereas ADAR2 typically acts as a tumour suppressor. Furthermore, this review also provides an overview of small molecular inhibitors that disrupt the expression of ADAR enzymes. These inhibitors not only counteract tumorigenicity but also alleviate autoimmune disorders, neurological neurodegenerative symptoms, and metabolic diseases associated with aberrant dsRNA A-to-I editing processes. In summary, this comprehensive review offers detailed insights into the involvement of dsRNA A-to-I editing in disease pathogenesis and highlights the potential therapeutic roles for related small molecular inhibitors. These scientific findings will undoubtedly contribute to the advancement of personalized medicine based on dsRNA A-to-I editing.

Elevated ADAR expression is significantly linked to shorter overall survival and immune infiltration in patients with lung adenocarcinoma

To date, few studies have investigated whether the RNA-editing enzymes adenosine deaminases acting on RNA (ADARs) influence RNA functioning in lung adenocarcinoma (LUAD). To investigate the role of ADAR in lung cancer, we leveraged the advantages of The Cancer Genome Atlas (TCGA) database, from which we obtained transcriptome data and clinical information from 539 patients with LUAD. First, we compared ARAR expression levels in LUAD tissues with those in normal lung tissues using paired and unpaired analyses. Next, we evaluated the influence of ADARs on multiple prognostic indicators, including overall survival at 1, 3 and 5 years, as well as disease-specific survival and progression-free interval, in patients with LUAD. We also used Kaplan-Meier survival curves to estimate overall survival and Cox regression analysis to assess covariates associated with prognosis. A nomogram was constructed to validate the impact of the ADARs and clinicopathological factors on patient survival probabilities. The volcano plot and heat map revealed the differentially expressed genes associated with ADARs in LUAD. Finally, we examined ADAR expression versus immune cell infiltration in LUAD using Spearman's analysis. Using the Gene Expression Profiling Interactive Analysis (GEPIA2) database, we identified the top 100 genes most significantly correlated with ADAR expression, constructed a protein-protein interaction network and performed a Gene Ontology/Kyoto Encyclopedia of Genes and Genomes analysis on these genes. Our results demonstrate that ADARs are overexpressed in LUAD and correlated with poor patient prognosis. ADARs markedly increase the infiltration of T central memory, T helper 2 and T helper cells, while reducing the infiltration of immature dendritic, dendritic and mast cells. Most immune response markers, including T cells, tumor-associated macrophages, T cell exhaustion, mast cells, macrophages, monocytes and dendritic cells, are closely correlated with ADAR expression in LUAD.

A-to-I RNA editing shows dramatic up-regulation in osteosarcoma and broadly regulates tumor-related genes by altering microRNA target regions

A-to-I RNA editing is a prevalent type of RNA modification in animals. The dysregulation of RNA editing has led to multiple human cancers. However, the role of RNA editing has never been studied in osteosarcoma, a complex bone cancer with unknown molecular basis. We retrieved the RNA-sequencing data from 24 primary osteosarcoma patients and 3 healthy controls. We systematically profiled the RNA editomes in these samples and quantitatively identified reliable differential editing sites (DES) between osteosarcoma and normal samples. RNA editing efficiency is dramatically increased in osteosarcoma, presumably due to the significant up-regulation of editing enzymes ADAR1 and ADAR2. Up-regulated DES in osteosarcoma are enriched in 3'UTRs. Strikingly, such 3'UTR sites are further enriched in microRNA binding regions of gene EMP2 and other oncogenes, abolishing the microRNA suppression on target genes. Accordingly, the expression of these tumor-promoting genes is elevated in osteosarcoma. There might be an RNA editing-dependent pathway leading to osteosarcoma. We expanded our knowledge on the potential roles of RNA editing in oncogenesis. Based on these molecular features, our work is valuable for future prognosis and diagnosis of osteosarcoma.

METTL3-mediated m6A methylation of PYGB facilitates pancreatic ductal adenocarcinoma progression through the activation of NF-κB signaling

Brain Type Glycogen Phosphorylase (PYGB) has been revealed to participate in the progression of multiple human cancers. Nevertheless, the clinical significance and biological function of PYGB in pancreatic ductal adenocarcinoma (PAAD) remains unclarified. This study first analyzed the expression pattern, diagnostic value, and prognostic significance of PYGB in PAAD using the TCGA database. Subsequently, western blot assessed the protein expression of genes in PAAD cells. The viability, apoptosis, migration, and invasion of PAAD cells were assessed by CCK-8, TUNEL, and Transwell assays. Finally, in vivo experiment evaluated the effect of PYGB on PAAD tumor growth and metastasis. Through our investigation, it was revealed that PYGB had extremely high expression in PAAD and predicted a worse prognosis in patients with PAAD. Besides, the aggressiveness of PAAD cells could be suppressed or enhanced by depleting or supplementing PYGB. In addition, we demonstrated that METTL3 enhanced the translation of PYGB mRNA in an m6A-YTHDF1-dependent manner. Moreover, PYGB was revealed to regulate the malignant behaviors of PAAD cells by the mediation of the NF-κB signaling. Finally, PYGB depletion suppressed the growth and distant metastasis of PAAD in vivo. To conclude, our results indicated that METTL3-mediated m6A modification of PYGB exerted the tumor-promotive effect on PAAD through NF-κB signaling, suggesting PYGB is a potential therapeutic target in PAAD.

CREBZF mRNA nanoparticles suppress breast cancer progression through a positive feedback loop boosted by circPAPD4

BACKGROUND

Breast cancer (BC) negatively impacts the health of women worldwide. Circular RNAs (circRNAs) are a group of endogenous RNAs considered essential regulatory factor in BC tumorigenesis and progression. However, the underlying molecular mechanisms of circRNAs remain unclear.

METHODS

Expression levels of circPAPD4, miR-1269a, CREBZF, and ADAR1 in BC cell lines and tissues were measured using bioinformatics analysis, RT-qPCR, ISH, and IHC. Cell proliferation and apoptosis were measured using CCK8, EdU staining, flow cytometry, and TUNEL assays. Pearson correlation analysis, RNA pull-down, dual-luciferase reporter, and co-immunoprecipitation assays were used to explore the correlation among circPAPD4, miR-1269a, CREBZF, STAT3, and ADAR1. Effects of circPAPD4 overexpression on tumor progression were investigated using in vivo assays. Moreover, CREBZF mRNA delivered by polymeric nanoparticles (CREBZF-mRNA-NPs) was used to examine application value of our findings.

RESULTS

CircPAPD4 expression was low in BC tissues and cells. Functionally, circPAPD4 inhibited proliferation and promoted apoptosis in vitro and in vivo. Mechanistically, circPAPD4 biogenesis was regulated by ADAR1. And circPAPD4 promoted CREBZF expression by competitively binding to miR-1269a. More importantly, CREBZF promoted circPAPD4 expression by suppressing STAT3 dimerization and ADAR1 expression, revealing a novel positive feedback loop that curbed BC progression. Systematic delivery of CREBZF-mRNA-NPs effectively induced CREBZF expression and activated the positive feedback loop of circPAPD4/miR-1269a/CREBZF/STAT3/ADAR1, which might suppress BC progression in vitro and in vivo.

CONCLUSION

Our findings firstly illustrated that circPAPD4/miR-1269a/CREBZF/STAT3/ADAR1 positive feedback loop mediated BC progression, and delivering CREBZF mRNA nanoparticles suppressed BC progression in vitro and in vivo, which might provide novel insights into therapeutic strategies for breast cancer.

ARHGAP6 inhibits bladder cancer cell viability, migration, and invasion via β-catenin signaling and enhances mitomycin C sensitivity

The Rho/ROCK pathway regulates diverse cellular processes and contributes to the development and advancement of several types of human cancers. This study investigated the role of specific Rho GTPase-activating proteins (RhoGAP), ARHGAP6, in bladder cancer (BC). In this study, ARHGAP6 expression in BC and its clinical significance were investigated. In vitro and in vivo assays were used to explore the tumor-related function and the underlying molecular mechanism ARHGAP6 of in BC. The mRNA and protein levels of ARHGAP6 significantly reduced in human BC tissues and cell lines compared with corresponding adjacent non-cancerous tissues and normal urothelial cells. In vitro, ARHGAP6 overexpression markedly decreased the viability, migration, and invasion of BC cells. Interestingly, low ARHGAP6 expression in BC strongly correlated with poor patient survival and was highly associated with metastasis and β-catenin signaling. Furthermore, ARHGAP6 expression strongly influenced the sensitivity of BC cells to mitomycin C treatment. Together, our results demonstrate that ARHGAP6 plays critical roles in regulating the proliferation, migration, invasion, and metastasis of BC cells possibly via the modulation of β-catenin and strongly influences the chemosensitivity of BC cells.

Roles of RNA Methylations in Cancer Progression, Autophagy, and Anticancer Drug Resistance

RNA methylations play critical roles in RNA processes, including RNA splicing, nuclear export, nonsense-mediated RNA decay, and translation. Regulators of RNA methylations have been shown to be differentially expressed between tumor tissues/cancer cells and adjacent tissues/normal cells. N6-methyladenosine (m6A) is the most prevalent internal modification of RNAs in eukaryotes. m6A regulators include m6A writers, m6A demethylases, and m6A binding proteins. Since m6A regulators play important roles in regulating the expression of oncogenes and tumor suppressor genes, targeting m6A regulators can be a strategy for developing anticancer drugs. Anticancer drugs targeting m6A regulators are in clinical trials. m6A regulator-targeting drugs could enhance the anticancer effects of current chemotherapy drugs. This review summarizes the roles of m6A regulators in cancer initiation and progression, autophagy, and anticancer drug resistance. The review also discusses the relationship between autophagy and anticancer drug resistance, the effect of high levels of m6A on autophagy and the potential values of m6A regulators as diagnostic markers and anticancer therapeutic targets.