N6-methyladenosine upregulates ribosome biogenesis in environmental carcinogenesis

YTHDF2 promotes arsenic-induced malignant phenotypes by degrading PIDD1 mRNA in human keratinocytes

Arsenic is a widespread environmental carcinogen, and its carcinogenic mechanism has been the focus of toxicology. N6-methyladenosine (m6A) binding protein YTH domain family protein 2 (YTHDF2) performs various biological functions by degrading m6A-modified mRNAs. However, the m6A-modified target mRNA of YTHDF2 in regulating arsenic carcinogenesis remains largely unknown. To explore the effect of YTHDF2 in regulating arsenic carcinogenicity, we exposed the human keratinocyte HaCaT cells to 1 μM sodium arsenite for 50 generations to create a cell model of arsenic carcinogenesis (HaCaT-T). Our results demonstrated that YTHDF2 protein levels were higher in HaCaT-T cells than HaCaT cells, and knockdown of YTHDF2 significantly inhibited arsenic-induced malignant phenotypes. In addition, m6A levels in HaCaT-T cells were remarkably elevated, accompanied by abnormal expression of m6A methyltransferases and m6A demethylases. Mechanistically, YTHDF2 bound to p53-induced death domain protein 1 (PIDD1) mRNA in an m6A-dependent manner, thereby promoting the degradation of PIDD1 mRNA. Moreover, the decay of PIDD1 mRNA inhibited the formation of PIDDosome complex that is essential for activating the apoptosis initiator caspase-2, leading to a decrease in caspase-2-dependent mitochondrial apoptosis and subsequently promoting the malignant phenotypes of HaCaT-T cells. Collectively, our study reveals the role of YTHDF2 in arsenic-induced malignant phenotypes of human keratinocytes through direct interaction with PIDD1 mRNA in an m6A-dependent manner, which provides new insight into the precise mechanism underlying arsenic-induced skin cancer.

Dysregulation of Long Non-coding RNAs-the Novel lnc in Metal Toxicity and Carcinogenesis

PURPOSE OF REVIEW

Metals are common environmental pollutants. Acute and chronic exposures to non-essential toxic metals or excessive essential metals cause various diseases including cancer in humans. However, the underlying mechanisms have not been well understood. Long non-coding RNAs (lncRNAs) refer to RNA transcripts that have more than 200 nucleotides but do not have significant protein coding capacities. While lncRNAs were once considered transcription noise, they have become increasingly recognized as crucial players in various physiological and pathogenesis processes. The goal of this article is to review and discuss recent studies that show important roles of lncRNA dysregulations in metal toxicity and carcinogenesis.

RECENT FINDINGS

Recent studies showed that metal exposures dysregulate expression of lncRNAs in cultured cells, animals and humas. However, only a few studies determined the mechanisms of how metal exposure dysregulated expression of lncRNAs. The majority of the studies reported the association of abnormally expressed lncRNAs with various toxic effects of metal exposures, only limited studies established causal relationships demonstrating causal roles of dysregulated lncRNAs in metal toxicity and carcinogenesis. Mechanistically, most studies reported that dysregulated lncRNAs functioned as microRNA sponges to regulate gene expression, much less studies explored other mechanisms of lncRNA actions. It is evident that metal exposures dysregulate expression of lncRNAs, which may serve as novel mediators in metal toxicity and carcinogenesis. Further studies are needed to establish dysregulated lncRNAs as potential diagnostic biomarkers and therapeutic targets for metal exposure-associated diseases.

YTHDF2 phase separation promotes arsenic-induced keratinocyte transformation in a poly-m6A-dependent manner by inhibiting translational initiation of the key tumor suppressor PTEN

The phase separation of N6-methyladenosine (m6A) binding protein YTHDF2 plays a vital role in arsenic-induced skin damage, and YTHDF2 can bind to m6A-methylated mRNA of tumor suppressor PTEN. However, whether and how YTHDF2 phase separation regulates PTEN involved in arsenic-induced malignant transformation of keratinocytes remains blank. Here, we established arsenite-induced transformation models with stable expression of wild-type YTHDF2 or mutant YTHDF2 protein in vitro and in vivo. We found that the YTHDF2 protein underwent phase separation during arsenite-induced malignant transformation of keratinocytes, and YTHDF2 phase separation promoted the malignant phenotype of keratinocytes. Mechanically, YTHDF2 phase separation reduced PTEN protein levels, which in turn activated the pro-survival AKT signal. The binding of YTHDF2 to multiple m6A sites on PTEN mRNA drove YTHDF2 phase separation, inhibiting PTEN translation initiation and thus reducing PTEN protein levels. YTHDF2 phase separation recruited translation-initiation-factor kinase EIF2AK1 to phosphorylate eIF2α, thereby inhibiting translation initiation of poly-m6A-methylated PTEN mRNA. Furthermore, arsenite-induced oxidative stress triggered YTHDF2 phase separation by increasing m6A levels of PTEN mRNA. Our results demonstrated that YTHDF2 phase separation promotes arsenite-induced malignant transformation by inhibiting PTEN translation in a poly-m6A-dependent manner. This study sheds light on arsenic carcinogenicity from the novel aspect of m6A-mediated YTHDF2 phase separation.

Emerging roles of N6-methyladenosine in arsenic-induced toxicity

Arsenic can cause extensive toxic damage after entering the body of humans and animals by altering a variety of events. As the most common form of methylation modification of RNA in eukaryotic cells, N6-methyladenosine (m6A) is widely involved in regulating RNA processing, translation and degradation, thus playing important role in various pathophysiological processes. Emerging studies have demonstrated that m6A modification is synergistically mediated by methyltransferases, demethylases and methyl-binding proteins. Recently, emerging studies have shown that m6A modification and its regulatory proteins play important roles in arsenic toxicity through mediating various key signaling pathways. We comprehensively analyzed the mechanisms by which m6A modification and its regulatory proteins contribute to arsenic toxicity. Our reviews offer a scientific foundation for the development of preventive and control strategies to mitigate arsenic-induced toxicity, with an emphasis on an epigenetic approach.

Effects and mechanisms of N6-methyladenosine RNA methylation in environmental pollutant-induced carcinogenesis

Environmental pollution, including air pollution, plastic contamination, and heavy metal exposure, is a pressing global issue. This crisis contributes significantly to pollution-related diseases and is a critical risk factor for chronic health conditions, including cancer. Mounting evidence underscores the pivotal role of N6-methyladenosine (m6A) as a crucial regulatory mechanism in pathological processes and cancer progression. Governed by m6A writers, erasers, and readers, m6A orchestrates alterations in target gene expression, consequently playing a vital role in a spectrum of RNA processes, covering mRNA processing, translation, degradation, splicing, nuclear export, and folding. Thus, there is a growing need to pinpoint specific m6A-regulated targets in environmental pollutant-induced carcinogenesis, an emerging area of research in cancer prevention. This review consolidates the understanding of m6A modification in environmental pollutant-induced tumorigenesis, explicitly examining its implications in lung, skin, and bladder cancer. We also investigate the biological mechanisms that underlie carcinogenesis originating from pollution. Specific m6A methylation pathways, such as the HIF1A/METTL3/IGF2BP3/BIRC5 network, METTL3/YTHDF1-mediated m6A modification of IL 24, METTL3/YTHDF2 dynamically catalyzed m6A modification of AKT1, METTL3-mediated m6A-modified oxidative stress, METTL16-mediated m6A modification, site-specific ATG13 methylation-mediated autophagy, and the role of m6A in up-regulating ribosome biogenesis, all come into play in this intricate process. Furthermore, we discuss the direction regarding the interplay between pollutants and RNA metabolism, particularly in immune response, providing new information on RNA modifications for future exploration.

Enhancing m6A modification of lncRNA through METTL3 and RBM15 to promote malignant progression in bladder cancer

Objective

Bladder cancer is one of the most prominent malignancies affecting the urinary tract, characterized by a poor prognosis. Our previous research has underscored the pivotal role of m6A methylation in the progression of bladder cancer. Nevertheless, the precise relationship between N6-methyladenosine (m6A) regulation of long non-coding RNA (lncRNA) and bladder cancer remains elusive.

Methods

This study harnessed sequencing data and clinical records from 408 bladder cancer patients in the TCGA database. Employing R software, we conducted bioinformatics analysis to establish an m6A-lncRNA co-expression network. Analyzing the differences between high and low-risk groups, particularly at the immunological level, and subsequently investigating the primary regulatory factors of these lncRNA, validating the findings through experiments, and exploring their specific cellular functions.

Results

We identified 50 m6A-related lncRNA with prognostic significance through univariate Cox regression analysis. In parallel, we employed a LASSO-Cox regression model to pinpoint 11 lncRNA and calculate risk scores for bladder cancer patients. Based on the median risk score, patients were categorized into low-risk and high-risk groups. The high-risk cohort exhibited notably lower survival rates than their low-risk counterparts. Further analysis pointed to RBM15 and METTL3 as potential master regulators of these m6A-lncRNA. Experimental findings also shed light on the upregulated expression of METTlL3 and RBM15 in bladder cancer, where they contributed to the malignant progression of tumors. The experimental findings demonstrated a significant upregulation of METTL3 and RBM15 in bladder cancer specimens, implicating their contributory role in the oncogenic progression. Knockdown of METTL3 and RBM15 resulted in a marked attenuation of tumor cell proliferation, invasion, and migration, which was concomitant with a downregulation in the cellular m6A methylation status. Moreover, these results revealed that RBM15 and METTL3 function in a synergistic capacity, positing their involvement in cancer promotion via the upregulation of m6A modifications in long non-coding RNAs. Additionally, this study successfully developed an N-methyl-N-nitrosourea (MNU)-induced rat model of in situ bladder carcinoma, confirming the elevated expression of RBM15 and METTL3, which paralleled the overexpression of m6A-related- lncRNAs observed in bladder cancer cell lines. This congruence underscores the potential utility of these molecular markers in in vivo models that mirror human malignancies.

Conclusion

This study not only offers novel molecular targets,but also enriches the research on m6A modification in bladder cancer, thereby facilitating its clinical translation.

RNA methylation-related inhibitors: Biological basis and therapeutic potential for cancer therapy

RNA methylation is widespread in nature. Abnormal expression of proteins associated with RNA methylation is strongly associated with a number of human diseases including cancer. Increasing evidence suggests that targeting RNA methylation holds promise for cancer treatment. This review specifically describes several common RNA modifications, such as the relatively well-studied N6-methyladenosine, as well as 5-methylcytosine and pseudouridine (Ψ). The regulatory factors involved in these modifications and their roles in RNA are also comprehensively discussed. We summarise the diverse regulatory functions of these modifications across different types of RNAs. Furthermore, we elucidate the structural characteristics of these modifications along with the development of specific inhibitors targeting them. Additionally, recent advancements in small molecule inhibitors targeting RNA modifications are presented to underscore their immense potential and clinical significance in enhancing therapeutic efficacy against cancer. KEY POINTS: In this paper, several important types of RNA modifications and their related regulatory factors are systematically summarised. Several regulatory factors related to RNA modification types were associated with cancer progression, and their relationships with cancer cell migration, invasion, drug resistance and immune environment were summarised. In this paper, the inhibitors targeting different regulators that have been proposed in recent studies are summarised in detail, which is of great significance for the development of RNA modification regulators and cancer treatment in the future.

N6-methyladenosine promotes aberrant redox homeostasis required for arsenic carcinogenesis by controlling the adaptation of key antioxidant enzymes

N6-methyladenosine (m6A), a high-profile RNA epigenetic modification, responds to oxidative stress and temporal-specifically mediates arsenic carcinogenesis. However, how m6A affects aberrant redox homeostasis required for arsenic carcinogenesis is poorly understood. Here, we established arsenic-carcinogenic models of different stages, including As-treated, As-transformed, and As-tumorigenic cell models. We found that arsenic-induced reactive oxygen species (ROS) elevated m6A levels, thus triggering m6A-dependent antioxidant defenses. During arsenic-induced cell transformation, METTL3-upregulated m6A on the mRNAs of SOD1, SOD2, CAT, TXN, and GPX1 promoted the mRNA translation and protein expressions of these antioxidant enzymes by increasing YTHDF1-mediated mRNA stability. Meanwhile, FTO-downregulated m6A on PRDX5 mRNA increased PRDX5 translation and expression by reducing YTHDF2-mediated mRNA decay. After upregulated antioxidant defenses balanced with high levels of ROS induced by arsenic, the m6A balance formed in mRNAs of six key antioxidant enzymes (SOD1, SOD2, CAT, TXN, GPX1, and PRDX5) and promoted high expressions of these antioxidant enzymes to maintain aberrant redox homeostasis. METTL3 inhibitor STM2457, FTO inhibitor FB23-2, or YTHDF1 knockdown disturbed the aberrant redox homeostasis by breaking the m6A balance, causing cell death in arsenic-induced tumors. Our results demonstrated that m6A promotes the formation and maintenance of aberrant redox homeostasis required for arsenic carcinogenesis by time-dependently orchestrating the adaptive expressions of six key m6A-targeted antioxidant enzymes. This study advances our understanding of arsenic carcinogenicity from the novel aspect of m6A-dependent adaptation to arsenic-induced oxidative stress.