METTL3 potentiates resistance to cisplatin through m6 A modification of TFAP2C in seminoma

Role of the RNA binding protein IGF2BP1 in cancer multidrug resistance

The insulin-like growth factor-2 mRNA-binding protein 1 (IGF2BP1), a member of a conserved family of single-stranded RNA-binding proteins (IGF2BP1-3), is expressed in a broad range of fetal tissues, placenta and more than sixteen cancer types but only in a limited number of normal adult tissues. IGF2BP1is required for the transport from nucleus to cytoplasm of certain mRNAs that play essential roles in embryogenesis, carcinogenesis, and multidrug resistance (MDR), by affecting their stability, translation, or localization. The purpose of this review is to gather and present information on MDR mechanisms in cancer and the significance of IGF2BP1 in this context. Within this review, we will provide an overview of IGF2BP1, including its tissue distribution, expression, molecular targets in the context of tumorigenesis and its inhibitors. Our main focus will be on elucidating the interplay between IGF2BP1 and MDR, particularly with regard to chemoresistance mediated by ABC transporters.

Functions and mechanisms of RNA m6A regulators in breast cancer (Review)

Breast cancer (BC) is a major malignant tumor in females and the incidence rate of BC has increased worldwide in recent years. N6‑methyladenosine (m6A) is a methylation modification that occurs extensively in eukaryotic RNA. The abnormal expression of m6A and related regulatory proteins can activate or inhibit certain signal pathways or oncogenes, thus affecting the proliferation, metastasis and prognosis of BC. Numerous studies have shown that m6A regulator disorder exists in BC, and this disorder can be reversed. Therefore, m6A is predicted as a potential therapeutic target for BC. However, the molecular mechanism of m6A RNA methylation regulating the occurrence and development of BC has not been comprehensively elucidated. In this review article, the functions of various m6A regulators and the specific mechanisms of certain regulators of the progress of BC were summarized. Furthermore, the dual role of RNA methylation in tumor progression was discussed, concluding that RNA methylation can not only lead to tumorigenesis but at times give rise to inhibition of tumor formation. In addition, further comprehensive analysis on mechanisms of m6A regulators in BC is conducive to screening effective potential targets and formulating targeted treatment strategies, which will provide new methods for the prevention and treatment of BC.

Examining the evidence for mutual modulation between m6A modification and circular RNAs: current knowledge and future prospects

The resistance of cancer cells to treatment significantly impedes the success of therapy, leading to the recurrence of various types of cancers. Understanding the specific mechanisms of therapy resistance may offer novel approaches for alleviating drug resistance in cancer. Recent research has shown a reciprocal relationship between circular RNAs (circRNAs) and N6-methyladenosine (m6A) modification, and their interaction can affect the resistance and sensitivity of cancer therapy. This review aims to summarize the latest developments in the m6A modification of circRNAs and their importance in regulating therapy resistance in cancer. Furthermore, we explore their mutual interaction and exact mechanisms and provide insights into potential future approaches for reversing cancer resistance.

LINC00313 suppresses autophagy and promotes stemness of nasopharyngeal carcinoma cells through PTBP1/STIM1 axis

BACKGROUND

Nasopharyngeal carcinoma (NPC) is a kind of malignant head and neck tumor with high mortality. lncRNAs are valuable diagnostic biomarkers and therapeutic targets for various tumors. This study investigated the effects and mechanism of LINC00313 in nasopharyngeal carcinoma.

METHODS

Cell Counting Kit-8 (CCK-8) and immunohistochemistry were used for assessing cell proliferation. The levels of autophagy-related proteins, and stem cell markers were detected. Immunofluorescence assay was used for LC3 detection. Methylated RNA Immunoprecipitation (meRIP) of LINC00313 in NPC cells was assessed. The localization of LINC00313 was verified by luorescence in situ hybridization (FIHS). The interaction between LINC00313 and the downstream targets were analyzed and confirmed by immunoprecipitation (RIP). Besides, the tumorigenesis roles of LINC00313 were confirmed in tumor growth mice model.

RESULTS

LINC00313 was increased in NPC tissues and cells. LINC00313 knockdown enhanced autophagy, and decreased stemness and cell viability of NPC cells through regulating STIM1. METTL3/IGF2BP1-mediated m6A modification promoted the stabilization and up-regulation of LINC00313. LINC00313 activated AKT/mTOR pathway in NPC cells through PTBP1/STIM1 axis. Moreover, LINC00313 promoted tumor growth and metastasis in xenograft model.

CONCLUSION

Upregulation of LINC00313 suppressed autophagy and promoted stemness of NPC cells through PTBP1/STIM1 axis.

Non-coding RNA transcripts, incredible modulators of cisplatin chemo-resistance in bladder cancer through operating a broad spectrum of cellular processes and signaling mechanism

Bladder cancer (BC) is a highly frequent neoplasm in correlation with significant rate of morbidity, mortality, and cost. The onset of BC is predominantly triggered by environmental and/or occupational exposures to carcinogens, such as tobacco. There are two distinct pathways by which BC can be developed, including non-muscle-invasive papillary tumors (NMIBC) and non-papillary (or solid) muscle-invasive tumors (MIBC). The Cancer Genome Atlas project has further recognized key genetic drivers of MIBC along with its subtypes with particular properties and therapeutic responses; nonetheless, NMIBC is the predominant BC presentation among the suffering individuals. Radical cystoprostatectomy, radiotherapy, and chemotherapy have been verified to be the common therapeutic interventions in metastatic tumors, among which chemotherapeutics are more conventionally utilized. Although multiple chemo drugs have been broadly administered for BC treatment, cisplatin is reportedly the most effective chemo drug against the corresponding malignancy. Notwithstanding, tumor recurrence is usually occurred following the consumption of cisplatin regimens, particularly due to the progression of chemo-resistant trait. In this framework, non-coding RNAs (ncRNAs), as abundant RNA transcripts arise from the human genome, are introduced to serve as crucial contributors to tumor expansion and cisplatin chemo-resistance in bladder neoplasm. In the current review, we first investigated the best-known ncRNAs, i.e. microRNAs (miRNAs), long ncRNAs (lncRNAs), and circular RNAs (circRNAs), correlated with cisplatin chemo-resistance in BC cells and tissues. We noticed that these ncRNAs could mediate the BC-related cisplatin-resistant phenotype through diverse cellular processes and signaling mechanisms, reviewed here. Eventually, diagnostic and prognostic potential of ncRNAs, as well as their therapeutic capabilities were highlighted in regard to BC management.

IGF2BPs as novel m6A readers: Diverse roles in regulating cancer cell biological functions, hypoxia adaptation, metabolism, and immunosuppressive tumor microenvironment

m6A methylation is the most frequent modification of mRNA in eukaryotes and plays a crucial role in cancer progression by regulating biological functions. Insulin-like growth factor 2 mRNA-binding proteins (IGF2BP) are newly identified m6A 'readers'. They belong to a family of RNA-binding proteins, which bind to the m6A sites on different RNA sequences and stabilize them to promote cancer progression. In this review, we summarize the mechanisms by which different upstream factors regulate IGF2BP in cancer. The current literature analyzed here reveals that the IGF2BP family proteins promote cancer cell proliferation, survival, and chemoresistance, inhibit apoptosis, and are also associated with cancer glycolysis, angiogenesis, and the immune response in the tumor microenvironment. Therefore, with the discovery of their role as 'readers' of m6A and the characteristic re-expression of IGF2BPs in cancers, it is important to elucidate their mechanism of action in the immunosuppressive tumor microenvironment. We also describe in detail the regulatory and interaction network of the IGF2BP family in downstream target RNAs and discuss their potential clinical applications as diagnostic and prognostic markers, as well as recent advances in IGF2BP biology and associated therapeutic value.

ALKBH5 regulates paclitaxel resistance in NSCLC via inhibiting CEMIP-mediated EMT

N6-methyladenosine (m6A) is the most prevalent mRNA modification, and it is verified to be closely correlated with cancer occurrence and progression. The m6A demethylase ALKBH5 (alkB homolog 5) is dysregulated in various cancers. However, the role and underlying mechanism of ALKBH5 in the pathogenesis and especially the chemo-resistance of non-small cell lung cancer (NSCLC) is poorly elucidated. The current study shows that ALKBH5 expression is reduced in paclitaxel (PTX) resistant NSCLC cells and down-regulation of ALKBH5 usually implies poor prognosis of NSCLC patients. Over-expression of ALKBH5 in PTX-resistant cells can suppress cell proliferation and enhance chemo-sensitivity, while knockdown of ALKBH5 exerts the opposite effect, which further supports the tumor suppressive role of ALKBH5. Over-expression of ALKBH5 can also reverse the epithelial-mesenchymal transition (EMT) process in PTX-resistant cancer cells. Mechanistically, data from RNA-seq, real-time PCR and western blotting indicate that CEMIP (cell migration inducing hyaluronidase 1), also known as KIAA1199, may be the downstream target of ALKBH5. Furthermore, ALKBH5 negatively regulates the CEMIP level by reducing the stability of CEMIP mRNA. Collectively, the current data demonstrate that the ALKBH5/CEMIP axis modulates the EMT process in NSCLC, which in turn regulates the chemo-sensitivity of cancer cells to PTX.

The Role of m6A-Mediated DNA Damage Repair in Tumor Development and Chemoradiotherapy Resistance

Among the post-transcriptional modifications, m6A RNA methylation has gained significant research interest due to its critical role in regulating transcriptional expression. This modification affects RNA metabolism in several ways, including processing, nuclear export, translation, and decay, making it one of the most abundant transcriptional modifications and a crucial regulator of gene expression. The dysregulation of m6A RNA methylation-related proteins in many tumors has been shown to lead to the upregulation of oncoprotein expression, tumor initiation, proliferation, cancer cell progression, and metastasis.Although the impact of m6A RNA methylation on cancer cell growth and proliferation has been extensively studied, its role in DNA repair processes, which are crucial to the pathogenesis of various diseases, including cancer, remains unclear. However, recent studies have shown accumulating evidence that m6A RNA methylation significantly affects DNA repair processes and may play a role in cancer drug resistance. Therefore, a comprehensive literature review is necessary to explore the potential biological role of m6A-modified DNA repair processes in human cancer and cancer drug resistance.In conclusion, m6A RNA methylation is a crucial regulator of gene expression and a potential player in cancer development and drug resistance. Its dysregulation in many tumors leads to the upregulation of oncoprotein expression and tumor progression. Furthermore, the impact of m6A RNA methylation on DNA repair processes, although unclear, may play a crucial role in cancer drug resistance. Therefore, further studies are warranted to better understand the potential biological role of m6A-modified DNA repair processes in human cancer and cancer drug resistance.

The role of RNA modification in urological cancers: mechanisms and clinical potential

RNA modification is a post-transcriptional level of regulation that is widely distributed in all types of RNAs, including mRNA, tRNA, rRNA, miRNA, and lncRNA, where N6-methyladenine (m6A) is the most abundant mRNA methylation modification. Significant evidence has depicted that m6A modifications are closely related to human diseases, especially cancer, and play pivotal roles in RNA transcription, splicing, stabilization, and translation processes. The most common urological cancers include prostate, bladder, kidney, and testicular cancers, accounting for a certain proportion of human cancers, with an ever-increasing incidence and mortality. The recurrence, systemic metastasis, poor prognosis, and drug resistance of urologic tumors have prompted the identification of new therapeutic targets and mechanisms. Research on m6A modifications may provide new solutions to the current puzzles. In this review, we provide a comprehensive overview of the key roles played by RNA modifications, especially m6A modifications, in urologic cancers, as well as recent research advances in diagnostics and molecularly targeted therapies.

METTL3-mediated m6A methylation regulates ovarian cancer progression by recruiting myeloid-derived suppressor cells

BACKGROUND

Ovarian cancer (OC) typically develops an immunosuppressive microenvironment by funtional changes of host immune cells. Dysregulated m6A level is associated with cancer progression via the intrinsic oncogenic pathways. However, the role of m6A in regulating host immune cell function during anti-tumor immunity needs comprehensive analysis. This study aimed to investigate the role of METTL3, a catalytic subunit of the methyltransferase complex, in regulating host immune cell response against OC.

METHODS

In this study, myeloid-specific Mettl3 gene knockout (Mettl3-cKO) mice were bred using the Cre-LoxP system. Intraperitoneally injection of ID8 cells was used as a syngeneic OC model. Furthermore, the compositions of immune cell populations were analyzed by flow cytometry and single-cell sequencing. Moreover, chemokines and cytokines secretion were assessed using ELISA. Lastly, the role of METTL3 in regulating IL-1β secretion and inflammasome activation in bone marrow-derived macrophages cocultured with ID8 cells was specified by ELISA and immunoblotting.

RESULTS

It was revealed that OC cell growth was enhanced in Mettl3-cKO mice. Furthermore, a shift of decreased M1 to increased M2 macrophage polarization was observed during OC progression. Moreover, Mettl3 depletion in myeloid lineage cells increased secretion of CCL2 and CXCL2 in peritoneal lavage fluild. Interestingly, Mettl3 deficiency enhanced IL-1β secretion induced by viable ID8 cells independent of inflammasome activation and cell death. Therefore, OC cells in tumor-bearing mice trigger a slight inflammatory response with a low-to-moderate secretion of pro-inflammatory cytokines and chemokines.

CONCLUSION

This study provides new insights into METTL3-mediated m6A methylation, which regulates host immune response against OC.

The role of N6-methyladenosine RNA modification in platinum resistance

N6-methyladenosine (m6A) RNA methylation, a dynamic regulator of transcript expression, plays a pivotal role in cancer by influencing diverse mRNA processes, including nuclear export, splicing, translation and decay. It intersects with cancer biology, impacting progression, treatment sensitivity and prognosis. Platinum-based compounds are essential in cancer treatment, while intrinsic or acquired resistance poses a formidable challenge, limiting therapeutic efficacy. Recent breakthroughs have established a direct association between m6A RNA methylation and platinum resistance in various cancer types. This review summarized related studies, aiming to provide profound insights into the interplay between m6A-associated regulation and platinum-resistance mechanisms in cancer. It explores therapeutic approaches, including personalized treatments based on m6A profiles, guiding future research to enhance clinical strategies for oncological prognostic outcomes.

N6-methyladenosine (m6A) in cancer therapeutic resistance: Potential mechanisms and clinical implications

Cancer therapy resistance (CTR) is the development of cancer resistance to multiple therapeutic strategies, which severely affects clinical response and leads to cancer progression, recurrence, and metastasis. N6-methyladenosine (m6A) has been identified as the most common, abundant, and conserved internal transcriptional alterations of RNA modifications, regulating RNA splicing, translation, stabilization, degradation, and gene expression, and is involved in the development and progression of a variety of diseases, including cancer. Recent studies have shown that m6A modifications play a critical role in both cancer development and progression, especially in reversing CTR. Although m6A modifications have great potential in CTR, the specific molecular mechanisms are not fully elucidated. In this review, we summarize the potential molecular mechanisms of m6A modification in CTR. In addition, we update recent advances in natural products from Traditional Chinese Medicines (TCM) and small-molecule lead compounds targeting m6A modifications, and discuss the great potential and clinical implications of these inhibitors targeting m6A regulators and combinations with other therapies to improve clinical efficacy and overcome CTR.

The current landscape of m6A modification in urological cancers

N6-methyladenosine (m6A) methylation is a dynamic and reversible procession of epigenetic modifications. It is increasingly recognized that m6A modification has been involved in the tumorigenesis, development, and progression of urological tumors. Emerging research explored the role of m6A modification in urological cancer. In this review, we will summarize the relationship between m6A modification, renal cell carcinoma, bladder cancer, and prostate cancer, and discover the biological function of m6A regulators in tumor cells. We will also discuss the possible mechanism and future application value used as a potential biomarker or therapeutic target to benefit patients with urological cancers.

Crucial role of the transcription factors family activator protein 2 in cancer: current clue and views

The transcription factor family activator protein 2 (TFAP2) is vital for regulating both embryonic and oncogenic development. The TFAP2 family consists of five DNA-binding proteins, including TFAP2A, TFAP2B, TFAP2C, TFAP2D and TFAP2E. The importance of TFAP2 in tumor biology is becoming more widely recognized. While TFAP2D is not well studied, here, we mainly focus on the other four TFAP2 members. As a transcription factor, TFAP2 regulates the downstream targets directly by binding to their regulatory region. In addition, the regulation of downstream targets by epigenetic modification, posttranslational regulation, and interaction with noncoding RNA have also been identified. According to the pathways in which the downstream targets are involved in, the regulatory effects of TFAP2 on tumorigenesis are generally summarized as follows: stemness and EMT, interaction between TFAP2 and tumor microenvironment, cell cycle and DNA damage repair, ER- and ERBB2-related signaling pathway, ferroptosis and therapeutic response. Moreover, the factors that affect TFAP2 expression in oncogenesis are also summarized. Here, we review and discuss the most recent studies on TFAP2 and its effects on carcinogenesis and regulatory mechanisms.

Oncofetal protein IGF2BPs in human cancer: functions, mechanisms and therapeutic potential

N⁶-methyladenosine (m⁶A) is the most prevalent and well-characterized internal chemical modification in eukaryotic RNA, influencing gene expression and phenotypic changes by controlling RNA fate. Insulin-like growth factor-2 mRNA-binding proteins (IGF2BPs) preferentially function as m⁶A effector proteins, promoting stability and translation of m⁶A-modified RNAs. IGF2BPs, particularly IGF2BP1 and IGF2BP3, are widely recognized as oncofetal proteins predominantly expressed in cancer rather than normal tissues, playing a critical role in tumor initiation and progression. Consequently, IGF2BPs hold potential for clinical applications and serve as a good choice for targeted treatment strategies. In this review, we discuss the functions and mechanisms of IGF2BPs as m⁶A readers and explore the therapeutic potential of targeting IGF2BPs in human cancer.

The role of m6A methylation in therapy resistance in cancer

Cancer therapy resistance is the main cause of cancer treatment failure. The mechanism of therapy resistance is a hot topic in epigenetics. As one of the most common RNA modifications, N6-methyladenosine (m6A) is involved in various processes of RNA metabolism, such as stability, splicing, transcription, translation, and degradation. A large number of studies have shown that m6A RNA methylation regulates the proliferation and invasion of cancer cells, but the role of m6A in cancer therapy resistance is unclear. In this review, we summarized the research progress related to the role of m6A in regulating therapy resistance in cancers.

Breaking the Mold: Epigenetics and Genomics Approaches Addressing Novel Treatments and Chemoresponse in TGCT Patients

Testicular germ-cell tumors (TGCT) have been widely recognized for their outstanding survival rates, commonly attributed to their high sensitivity to cisplatin-based therapies. Despite this, a subset of patients develops cisplatin resistance, for whom additional therapeutic options are unsuccessful, and ~20% of them will die from disease progression at an early age. Several efforts have been made trying to find the molecular bases of cisplatin resistance. However, this phenomenon is still not fully understood, which has limited the development of efficient biomarkers and precision medicine approaches as an alternative that could improve the clinical outcomes of these patients. With the aim of providing an integrative landscape, we review the most recent genomic and epigenomic features attributed to chemoresponse in TGCT patients, highlighting how we can seek to combat cisplatin resistance through the same mechanisms by which TGCTs are particularly hypersensitive to therapy. In this regard, we explore ongoing treatment directions for resistant TGCT and novel targets to guide future clinical trials. Through our exploration of recent findings, we conclude that epidrugs are promising treatments that could help to restore cisplatin sensitivity in resistant tumors, shedding light on potential avenues for better prognosis for the benefit of the patients.

RNA N6-methyladenosine modification in regulating cancer stem cells and tumor immune microenvironment and its implication for cancer therapy

Therapy resistance is a well-known phenomenon in cancer treatment. It can be intrinsic or acquired, accountable for frequent tumor relapse and death worldwide. The interplay between cancer cells and their neighboring environment can activate complex signaling mechanisms influencing epigenetic changes and maintain cancer cell survival leading to the malignant phenotype. Cancer stem cells (CSCs) are tumor-initiating cells (TICs) and constitute the primary source of drug resistance and tumor recurrence. Studies have shown that cancer cells exhibit dysregulated RNA N6-methyladenosine (m6A) "writers," "erasers," and "readers" levels after acquiring drug resistance. The present review provides novel insight into the role of m6A modifiers involved in CSC generation, cancer cell proliferation, and therapy resistance. m6A RNA modifications in the cross-talk between CSC and the tumor immune microenvironment (TIME) have also been highlighted. Further, we have discussed the therapeutic potential of targeting m6A machinery for cancer diagnosis and the development of new therapies for cancer treatment.

RNA methylation and cellular response to oxidative stress-promoting anticancer agents

Disruption of the complex network that regulates redox homeostasis often underlies resistant phenotypes, which hinder effective and long-lasting cancer eradication. In addition, the RNA methylome-dependent control of gene expression also critically affects traits of cellular resistance to anti-cancer agents. However, few investigations aimed at establishing whether the epitranscriptome-directed adaptations underlying acquired and/or innate resistance traits in cancer could be implemented through the involvement of redox-dependent or -responsive signaling pathways. This is unexpected mainly because: i) the effectiveness of many anti-cancer approaches relies on their capacity to promote oxidative stress (OS); ii) altered redox milieu and reprogramming of mitochondrial function have been acknowledged as critical mediators of the RNA methylome-mediated response to OS. Here we summarize the current state of understanding on this topic, as well as we offer new perspectives that might lead to original approaches and strategies to delay or prevent the problem of refractory cancer and tumor recurrence.

N6-Methyladenosine RNA Modifications Regulate the Response to Platinum Through Nicotinamide N-methyltransferase

Development of resistance to platinum (Pt) in ovarian cancer remains a major clinical challenge. Here we focused on identifying epitranscriptomic modifications linked to Pt resistance. Fat mass and obesity-associated protein (FTO) is a N6-methyladenosine (m6A) RNA demethylase that we recently described as a tumor suppressor in ovarian cancer. We hypothesized that FTO-induced removal of m6A marks regulates the cellular response of ovarian cancer cells to Pt and is linked to the development of resistance. To study the involvement of FTO in the cellular response to Pt, we used ovarian cancer cells in which FTO was knocked down via short hairpin RNA or overexpressed and Pt-resistant (Pt-R) models derived through repeated cycles of exposure to Pt. We found that FTO was significantly downregulated in Pt-R versus sensitive ovarian cancer cells. Forced expression of FTO, but not of mutant FTO, increased sensitivity to Pt in vitro and in vivo (P < 0.05). Increased numbers of γ-H2AX foci, measuring DNA double-strand breaks, and increased apoptosis were observed after exposure to Pt in FTO-overexpressing versus control cells. Through integrated RNA sequencing and MeRIP sequencing, we identified and validated the enzyme nicotinamide N-methyltransferase (NNMT), as a new FTO target linked to Pt response. NNMT was upregulated and demethylated in FTO-overexpressing cells. Treatment with an NNMT inhibitor or NNMT knockdown restored sensitivity to Pt in FTO-overexpressing cells. Our results support a new function for FTO-dependent m6A RNA modifications in regulating the response to Pt through NNMT, a newly identified RNA methylated gene target.

Emerging roles of m6A RNA modification in cancer therapeutic resistance

Marvelous advancements have been made in cancer therapies to improve clinical outcomes over the years. However, therapeutic resistance has always been a major difficulty in cancer therapy, with extremely complicated mechanisms remain elusive. N6-methyladenosine (m6A) RNA modification, a hotspot in epigenetics, has gained growing attention as a potential determinant of therapeutic resistance. As the most prevalent RNA modification, m6A is involved in every links of RNA metabolism, including RNA splicing, nuclear export, translation and stability. Three kinds of regulators, "writer" (methyltransferase), "eraser" (demethylase) and "reader" (m6A binding proteins), together orchestrate the dynamic and reversible process of m6A modification. Herein, we primarily reviewed the regulatory mechanisms of m6A in therapeutic resistance, including chemotherapy, targeted therapy, radiotherapy and immunotherapy. Then we discussed the clinical potential of m6A modification to overcome resistance and optimize cancer therapy. Additionally, we proposed existing problems in current research and prospects for future research.

HN1L/AP-2γ/PLK1 signaling drives tumor progression and chemotherapy resistance in esophageal squamous cell carcinoma

Hematological and neurological expressed 1 like (HN1L) is a newly identified oncogene in lung cancer and hepatocellular carcinoma recently identified by our team, but its roles in the development and treatment of esophageal squamous cell carcinoma (ESCC) remain incompletely cataloged. Here, using ESCC tissue array and public database analysis, we demonstrated that HN1L was highly expressed in ESCC tissues, which was associated with tumor tissue invasion, poor clinical stage and short survival for ESCC patients. Loss- and gain-of-function studies in ESCC cells revealed that HN1L enhances ESCC cell metastasis and proliferation in vitro and in mice models. Moreover, high level of HN1L reduces the sensibility of ESCC cells to chemotherapeutic drugs, such as Docetaxel. Mechanism studies revealed that HN1L activated the transcription of polo-like kinase 1 (PLK1) by interacting with transcription factor AP-2γ, which increased the expression of malignancy related proteins Cyclin D1 and Slug in ESCC cells. Blocking PLK1 with inhibitor BI-2356 abrogated the oncogenic function of HN1L and significantly suppressed ESCC progression by combining with chemotherapy. Therefore, this study demonstrates the vital pro-tumor role of HN1L/AP-2γ/PLK1 signaling axis in ESCC, offering a potential therapeutic strategy for ESCC patients with high HN1L by blocking PLK1.

cfDNA methylation in liquid biopsies as potential testicular seminoma biomarker

Background: Seminoma is a testicular tumor type, routinely diagnosed after orchidectomy. As cfDNA represents a source of minimally invasive seminoma patient management, this study aimed to investigate whether cfDNA methylation of six genes from liquid biopsies, have potential as novel seminoma biomarkers. Materials & methods: cfDNA methylation from liquid biopsies was assessed by pyrosequencing and compared with healthy volunteers' samples. Results: Detailed analysis revealed specific CpGs as possible seminoma biomarkers, but receiver operating characteristic curve analysis showed modest diagnostic performance. In an analysis of panels of statistically significant CpGs, two DNA methylation panels emerged as potential seminoma screening panels, one in blood CpG8/CpG9/CpG10 (KITLG) and the other in seminal plasma CpG1(MAGEC2)/CpG1(OCT3/4). Conclusion: The presented data promote the development of liquid biopsy epigenetic biomarkers in the screening of seminoma patients.

RNA m6 A methylation in cancer

N⁶ -methyladenosine (m⁶ A) is one of the most abundant internal modifications in eukaryotic messenger RNAs (mRNAs) and non-coding RNAs (ncRNAs). It is a reversible and dynamic RNA modification that has been observed in both internal coding segments and untranslated regions. Studies indicate that m⁶ A modifications play important roles in translation, RNA splicing, export, degradation and ncRNA processing control. In this review, we focus on the profiles and biological functions of RNA m⁶ A methylation on both mRNAs and ncRNAs. The dynamic modification of m⁶ A and its potential roles in cancer development are discussed. Moreover, we discuss the possibility of m⁶ A modifications serving as potential biomarkers for cancer diagnosis and targets for therapy.

TFAP2C Knockdown Sensitizes Bladder Cancer Cells to Cisplatin Treatment via Regulation of EGFR and NF-κB

Simple Summary

Bladder cancer (BCa) is considered one of the most common neoplasms of the urology system. Cisplatin-based chemotherapy has been the primary treatment for patients with advanced or metastatic BCa. Nevertheless, cisplatin resistance often limits the treatment of bladder cancer. We expect to find approaches to improve the therapeutic efficacy of cisplatin in bladder cancer. In recent years, many studies have shown that transcription factor AP-2 gamma (TFAP2C) acts as a key player in cancer development and and its expression level is closely related to the sensitivity of tumors to cisplatin. Our study investigated whether TFAP2C affects the sensitivity of BCa cells to cisplatin and the possible mechanisms. We found that TFAP2C expression was significantly upregulated in most BCa tissues compared to adjacent normal tissues. The present study confirmed that TFAP2C knockdown enhanced the anti-tumor effects of cisplatin by decreasing cisplatin-induced activation levels of epidermal growth factor receptor (EGFR) and nuclear factor kappaB (NF-κB). Specifically, this study provides a novel approach to improve the efficacy of cisplatin.

Abstract

Cisplatin is the first-line chemotherapy for advanced or metastatic bladder cancer. Nevertheless, approximately half of patients with BCa are insensitive to cisplatin therapy or develop cisplatin resistance during the treatment process. Therefore, it is especially crucial to investigate ways to enhance the sensitivity of tumor cells to cisplatin. Transcription factor AP-2 gamma (TFAP2C) is involved in cancer development and chemotherapy sensitivity. However, its relationship with chemotherapy has not been studied in BCa. In this study, we aimed to investigate the therapeutic potential of TFAP2C in human BCa. Results based on TCGA (The Cancer Genome Atlas), GTEx (The Genotype-Tissue Expression) and GEO (Gene Expression Omnibus) data showed that TFAP2C expression was upregulated in BCa tissues and that its high expression was associated with poor prognosis. Meanwhile, we demonstrated the overexpression of TFAP2C in BCa clinical specimens. Subsequently, in vitro, we knocked down TFAP2C in BCa cells and found that TFAP2C knockdown further increased cell cycle arrest and apoptosis caused by cisplatin. In addition, the inhibitory effect of cisplatin on BCa cell migration and invasion was enhanced by TFAP2C knockdown. Our data indicated that cisplatin increased epidermal growth factor receptor (EGFR) and nuclear factor-kappaB (NF-κB) activation levels, but TFAP2C knockdown suppressed this effect. Finally, in vivo data further validated these findings. Our study showed that TFAP2C knockdown affected the activation levels of EGFR and NF-κB and enhanced the anti-tumor effects of cisplatin in vivo and in vitro. This provides a new direction to improve the efficacy of traditional cisplatin chemotherapy.

Crosstalk between m6A regulators and mRNA during cancer progression

m⁶A modification, the most abundant and widespread RNA modification, is present and involved in the occurrence and development of various cancers. To date, most studies have mainly focused on the roles of a single m⁶A regulator (writer/eraser/reader) in various cancers, but cumulative evidence shows that aberrant m⁶A regulators and m⁶A levels exert dual effects (promoting and/or inhibiting roles) in cancer progression. Recently, studies have investigated the direct interactions between different m⁶A regulators (writer/eraser and reader) and mRNAs in a variety of cancers. In this review, we summarize the functions of m⁶A regulators and their roles in various types of cancers. We further propose the possible crosstalk mechanisms (Writer-m⁶A-Reader-mRNA axis and Eraser-m⁶A-Reader-mRNA axis) between different m⁶A regulators and mRNAs during cancer progression. We also discuss the clinical potential of m⁶A regulator‑targeting strategies.

Mutual regulation between N6-methyladenosine (m6A) modification and circular RNAs in cancer: impacts on therapeutic resistance

The resistance of tumor cells to therapy severely impairs the efficacy of treatment, leading to recurrence and metastasis of various cancers. Clarifying the underlying mechanisms of therapeutic resistance may provide new strategies for overcoming cancer resistance. N6-methyladenosine (m6A) is the most prevalent RNA modification in eukaryotes, and is involved in the regulation of RNA splicing, translation, transport, degradation, stability and processing, thus affecting several physiological processes and cancer progression. As a novel type of multifunctional non-coding RNAs (ncRNAs), circular RNAs (circRNAs) have been demonstrated to play vital roles in anticancer therapy. Currently, accumulating studies have revealed the mutual regulation of m6A modification and circRNAs, and their interaction can further influence the sensitivity of cancer treatment. In this review, we mainly summarized the recent advances of m6A modification and circRNAs in the modulation of cancer therapeutic resistance, as well as their interplay and potential mechanisms, providing promising insights and future directions in reversal of therapeutic resistance in cancer.

Crosstalk among m6A RNA methylation, hypoxia and metabolic reprogramming in TME: from immunosuppressive microenvironment to clinical application

The tumor microenvironment (TME), which is regulated by intrinsic oncogenic mechanisms and epigenetic modifications, has become a research hotspot in recent years. Characteristic features of TME include hypoxia, metabolic dysregulation, and immunosuppression. One of the most common RNA modifications, N6-methyladenosine (m⁶A) methylation, is widely involved in the regulation of physiological and pathological processes, including tumor development. Compelling evidence indicates that m⁶A methylation regulates transcription and protein expression through shearing, export, translation, and processing, thereby participating in the dynamic evolution of TME. Specifically, m⁶A methylation-mediated adaptation to hypoxia, metabolic dysregulation, and phenotypic shift of immune cells synergistically promote the formation of an immunosuppressive TME that supports tumor proliferation and metastasis. In this review, we have focused on the involvement of m⁶A methylation in the dynamic evolution of tumor-adaptive TME and described the detailed mechanisms linking m⁶A methylation to change in tumor cell biological functions. In view of the collective data, we advocate treating TME as a complete ecosystem in which components crosstalk with each other to synergistically achieve tumor adaptive changes. Finally, we describe the potential utility of m⁶A methylation-targeted therapies and tumor immunotherapy in clinical applications and the challenges faced, with the aim of advancing m⁶A methylation research.

Epitranscriptomics Changes the Play: m6A RNA Modifications in Apoptosis

Apoptosis is a form of programmed cell death that is essential for cellular and organismal homeostasis. Any irregularities that disturb the balance between apoptosis and cell survival have severe implications, such as improper development or life-threatening diseases. Thus, it is highly critical to maintain a proper rate of apoptosis throughout development. In fact, several complex transcriptional and posttranscriptional mechanisms exist in eukaryotes to critically regulate the rate of apoptotic processes. Recent studies suggest that not only RNA sequences but also their modifications, such as m⁶A methylation, play a fundamental role in these transcriptional and posttranscriptional processes. A specific set of proteins, called writer, eraser, and reader of m⁶A marks, modulate the rate of apoptosis by determining the m⁶A repertoire and the fate of certain transcripts associated with apoptosis. In this Review, we will cover the dynamic m⁶A RNA modifications and their impact on modulation of apoptosis.

YTHDF2 promotes intrahepatic cholangiocarcinoma progression and desensitises cisplatin treatment by increasing CDKN1B mRNA degradation

BACKGROUND

Intrahepatic cholangiocarcinoma (ICC) is an aggressive cancer with exceedingly poor prognosis, and chemoresistance is a huge challenge for treatment. N6-methyladenosine (m6 A) modification plays an important role in the progression and chemoresistance of cancers. We aimed to investigate the oncogenic function and therapeutic significance of the m6 A binding protein, YTH domain family 2 (YTHDF2), in ICC progression and cisplatin-based chemotherapy.

METHODS

Several independent data sets were used to assess the expression of YTHDF2 in ICC, particularly in chemoresistant ICC. Knockdown and overexpression were used to evaluate the effects of YTHDF2 on tumourigenesis and cisplatin response in ICC. Multi-omics sequencing was performed to identify target genes. RIP, dual luciferase reporter, RNA stability experiment and loss-of-function assays were conducted to study the mechanisms underlying the oncogenic function of YTHDF2. Furthermore, patient-derived xenograft (PDX) model was established to determine the effect of combination treatment of YTHDF2 siRNA and cisplatin in ICC.

RESULTS

Our study showed that YTHDF2 was upregulated in ICC tissues, particularly in chemoresistant ICC tissues, and correlated with poor prognosis. Furthermore, silencing YTHDF2 led to inhibited proliferation, promoted apoptosis and G0/G1 cell cycle arrest. Its downregulation also enhanced DNA damage and sensitised ICC cells to cisplatin. YTHDF2 overexpression exerted the opposite results. Integration analysis using RNA-seq, MeRIP-seq and anti-YTHDF2 RIP-seq elucidated the role of YTHDF2 in tumourigenesis and cisplatin-desensitising function by promoting the degradation of cyclin-dependent kinase inhibitor 1B (CDKN1B) mRNA in an m6 A-dependent manner. Downregulation of CDKN1B increased the YTHDF2 silencing-induced influence on tumourigenesis and cisplatin response to ICC. In addition, the combination treatment of YTHDF2 siRNA and cisplatin significantly enhanced the anti-tumour effect of cisplatin in a chemoresistant ICC PDX model.

CONCLUSIONS

YTHDF2 exhibits tumour oncogenic and cisplatin-desensitising properties, which may offer insight into the development of novel combination therapeutic strategies for ICC.

Exosome-transmitted circVMP1 facilitates the progression and cisplatin resistance of non-small cell lung cancer by targeting miR-524-5p-METTL3/SOX2 axis

Background

Circular RNAs (circRNAs) play important regulatory roles in multiple human malignancies, including non-small cell lung cancer (NSCLC). Here, we explored the role of circRNA vacuole membrane protein 1 (circVMP1) in NSCLC progression and cisplatin (DDP) resistance.

Methods

The DDP resistance, proliferation, sphere formation ability, migration, invasion, and apoptosis of NSCLC cells were analyzed by Cell Counting Kit-8 (CCK8) assay, 5-ethynyl-2′-deoxyuridine (EdU) assay, sphere formation assay, wound healing assay, Transwell assay, and flow cytometry. Methylated RIP-qPCR (MeRIP-qPCR) was conducted to analyze the m⁶A modification level of SRY-box transcription factor 2 (SOX2). Dual-luciferase reporter assay, RNA immunoprecipitation (RIP) assay, and RNA-pull down assay were performed to confirm the intermolecular interaction. Exosomes were identified by transmission electron microscopy (TEM) and characterized by nanoparticle tracking analysis (NTA).

Results

CircVMP1 expression was markedly elevated in DDP-resistant NSCLC cell lines compared with their parental cell lines. CircVMP1 absence restrained the proliferation, sphere formation, migration, invasion, and DDP resistance and promoted the apoptosis of DDP-resistant NSCLC cells. CircVMP1 acted as microRNA-524-5p (miR-524-5p) sponge to up-regulate the expression of methyltransferase 3, N6-adenosine-methyltransferase complex catalytic subunit (METTL3) and SOX2. CircVMP1 silencing restrained the malignant behaviors and DDP resistance of A549/DDP and H1299/DDP cells by targeting miR-524-5p. Exosomal circVMP1 disseminated the malignant properties and DDP resistance to DDP-sensitive cells. Exosomal circVMP1 elevated the DDP resistance of xenograft tumors in vivo. Exosomal circVMP1 was up-regulated in the serum samples of DDP-resistant NSCLC patients compared with DDP-sensitive patients.

Conclusion

Exosome-mediated transmission of circVMP1 promoted NSCLC progression and DDP resistance by targeting miR-524-5p-METTL3/SOX2 axis.

Highlights

CircVMP1 level is up-regulated in DDP-resistant NSCLC cell lines compared with DDP-sensitive cell lines.

CircVMP1 absence restrains the malignant behaviors and DDP resistance of A549/DDP and H1299/DDP cells.

CircVMP1-miR-524-5p/METTL3/SOX2 axis is identified for the first time.

CircVMP1 plays an oncogenic role by targeting miR-524-5p-METTL3/SOX2 axis in A549/DDP and H1299/DDP cells.

Exosomal circVMP1 transmits the malignant properties and DDP resistance to DDP-sensitive cells.

N6-Methyladenosine Methyltransferase METTL3 Promotes Angiogenesis and Atherosclerosis by Upregulating the JAK2/STAT3 Pathway via m6A Reader IGF2BP1

Atherosclerosis (AS) is a life-threatening vascular disease. RNA N6-methyladenosine (m6A) modification level is dysregulated in multiple pathophysiologic processes including AS. In this text, the roles and molecular mechanisms of m6A writer METTL3 in AS progression were explored in vitro and in vivo. In the present study, cell proliferative, migratory, and tube formation capacities were assessed through CCK-8, Transwell migration, and tube formation assays, respectively. RNA m6A level was examined through a commercial kit. RNA and protein levels of genes were measured through RT-qPCR and western blot assays, respectively. VEGF secretion level was tested through ELISA assay. JAK2 mRNA stability was detected through actinomycin D assay. The relationship of METTL3, IGF2BP1, and JAK2 was investigated through bioinformatics analysis, MeRIP, RIP, RNA pull-down, and luciferase reporter assays. An AS mouse model was established to examine the effect of METTL3 knockdown on AS development in vivo. The angiogenetic activity was examined through chick chorioallantoic membrane assay in vivo. The results showed that METTL3 was highly expressed in ox-LDL-induced dysregulated HUVECs. METTL3 knockdown inhibited cell proliferation, migration, tube formation, and VEGF expression/secretion in ox-LDL-treated HUVECs, hampered AS process in vivo, and prevented in vivo angiogenesis of developing embryos. METTL3 positively regulated JAK2 expression and JAK2/STAT3 pathway in an m6A dependent manner in HUVECs. IGF2BP1 positively regulated JAK2 expression through directly binding to an m6A site within JAK2 mRNA in HUVECs. METTL3 knockdown weakened the interaction of JAK2 and IGF2BP1. METTL3 exerted its functions through JAK2/STAT3 pathway. In conclusion, METTL3 knockdown prevented AS progression by inhibiting JAK2/STAT3 pathway via IGF2BP1.

METTL3 induces PLX4032 resistance in melanoma by promoting m6A-dependent EGFR translation

Acquired resistance often limits therapeutic efficacy of the BFAF (V600E) kinase inhibitor PLX4032 in patients with advanced melanoma. Epitranscriptomic modification of mRNAs by N⁶-methyladenosine (m⁶A) modification contributes to melanoma pathogenesis; however, its role in acquired PLX4032 resistance remains unexplored. Here, we showed that m⁶A methyltransferase METTL3 expression is upregulated in A375R cells, a PLX4032-resistant subline of A375 melanoma cells, compared with the parental cells. Moreover, METTL3 increased the m⁶A modification of epidermal growth factor receptor (EGFR) mRNA in A375R cells, which promoted its translation efficiency. In turn, increased EGFR expression facilitated rebound activation of the RAF/MEK/ERK pathway in A375R cells, inducing PLX4032 resistance. In contrast, knockout of METTL3 in A375R cells reduced EGFR expression and restored PLX4032 sensitivity. PLX4032 treatment following METTL3 knockout induced apoptosis and reduced colony formation in A375R cells and reduced A375R cell-derived tumor growth in BALB/c nude mice. These findings indicate that METTL3 promotes rebound activation of the RAF/MEK/ERK pathway through EGFR upregulation and highlight a critical role for METTL3-induced m⁶A modification in acquired PLX4032 resistance in melanoma, implicating METTL3 as a potential candidate for targeted chemotherapy.

m6A Modification in Non-Coding RNA: The Role in Cancer Drug Resistance

Cancer drug resistance has always been a major difficulty in cancer therapy. In the face of drug pressure, resistant cancer cells show complex molecular mechanisms including epigenetic changes to maintain survival. Studies prove that cancer cells exhibit abnormal m6A modification after acquiring drug resistance. m6A modification in the target RNA including non-coding RNA can be a controller to determine the fate and metabolism of RNA by regulating their stability, subcellular localization, or translation. In particular, m6A-modified non-coding RNA plays multiple roles in multiple drug-resistant cancer cells, which can be a target for cancer drug resistance. Here, we provide an overview of the complex regulatory mechanisms of m6A-modified non-coding RNA in cancer drug resistance, and we discuss its potential value and challenges in clinical applications.

Dynamic m6A-ncRNAs association and their impact on cancer pathogenesis, immune regulation and therapeutic response

Several types of modifications have been proven to participate in the metabolism and processing of different RNA types, including non-coding RNAs (ncRNAs). N-6-methyladenosine (m6A) is a dynamic and reversible RNA modification that is closely involved in the ncRNA homeostasis, and serves as a crucial regulator for multiple cancer-associated signaling pathways. The ncRNAs usually regulate the epigenetic modification, mRNA transcription and other biological processes, displaying enormous roles in human cancers. In this review, we summarized the significant implications of m6A-ncRNA interaction in various types of cancers. In particular, the interplay between m6A and ncRNAs in cancer pathogenesis and therapeutic resistance are being widely recognized. We also discussed the relevance of m6A-ncRNA interaction in immune regulation, followed by the interference on cancer immunotherapeutic procedures. In addition, we briefly highlighted the computation tools that could identify the accurate features of m6A methylome among ncRNAs. In summary, this review would pave the way for a better understanding of the biological functions of m6A-ncRNA crosstalk in cancer research and treatment.

METTL3 increases cisplatin chemosensitivity of cervical cancer cells via downregulation of the activity of RAGE

Cervical cancer is the most common gynecologic malignancy worldwide. Methyltransferase-like 3 (METTL3) is involved in tumorigenesis; however, it is unclear whether METTL3 plays a potential role in regulating cisplatin (DDP) resistance. Therefore, the role of METTL3 in the regulation of cisplatin sensitivity in cervical cancer cells was determined. Our immunohistochemistry (IHC) data showed that METTL3 was highly expressed in para-cancerous compared with cervical cancer tissues. Furthermore, METTL3 overexpression inhibited viability and increased cisplatin sensitivity of cervical cancer cells in vitro. Overexpression of METTL3 inhibited tumor growth in vivo. IHC results showed that the receptor for advanced glycation and products (RAGE) had higher expression levels in cervical cancer tissues. RAGE downregulation increased cell sensitivity to cisplatin treatment. Moreover, the combination of FPS-ZM1 with cisplatin was more effective in inhibiting cell viability as compared with FPS-ZM1 or cisplatin only. Additionally, METTL3 reduced RAGE expression in cervical cancer cells. Overexpression of METTL3 downregulated RAGE expression and caused more sensitivity to cisplatin treatment in the SiHa-DDP cell line. METTL3 inhibited cell viability and increased apoptosis as well as enhanced the sensitivity of cisplatin via downregulating RAGE expression in cervical cancer cells.

The component of the m6A writer complex VIRMA is implicated in aggressive tumor phenotype, DNA damage response and cisplatin resistance in germ cell tumors

Background

Germ cell tumors (GCTs) are developmental cancers, tightly linked to embryogenesis and germ cell development. The recent and expanding field of RNA modifications is being increasingly implicated in such molecular events, as well as in tumor progression and resistance to therapy, but still rarely explored in GCTs. In this work, and as a follow-up of our recent study on this topic in TGCT tissue samples, we aim to investigate the role of N6-methyladenosine (m⁶A), the most abundant of such modifications in mRNA, in in vitro and in vivo models representative of such tumors.

Methods

Four cell lines representative of GCTs (three testicular and one mediastinal), including an isogenic cisplatin resistant subline, were used. CRISPR/Cas9-mediated knockdown of VIRMA was established and the chorioallantoic membrane assay was used to study its phenotypic effect in vivo.

Results

We demonstrated the differential expression of the various m⁶A writers, readers and erasers in GCT cell lines representative of the major classes of these tumors, seminomas and non-seminomas, and we evidenced changes occurring upon differentiation with all-trans retinoic acid treatment. We showed differential expression also among cells sensitive and resistant to cisplatin treatment, implicating these players in acquisition of cisplatin resistant phenotype. Knockdown of VIRMA led to disruption of the remaining methyltransferase complex and decrease in m⁶A abundance, as well as overall reduced tumor aggressiveness (with decreased cell viability, tumor cell proliferation, migration, and invasion) and increased sensitivity to cisplatin treatment, both in vitro and confirmed in vivo. Enhanced response to cisplatin after VIRMA knockdown was related to significant increase in DNA damage (with higher γH2AX and GADD45B levels) and downregulation of XLF and MRE11.

Conclusions

VIRMA has an oncogenic role in GCTs confirming our previous tissue-based study and is further involved in response to cisplatin by interfering with DNA repair. These data contribute to our better understanding of the emergence of cisplatin resistance in GCTs and support recent attempts to therapeutically target elements of the m⁶A writer complex.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-02072-9.

N6-methyladenosine methyltransferases: functions, regulation, and clinical potential

N6-methyladenosine (m6A) has emerged as an abundant modification throughout the transcriptome with widespread functions in protein-coding and noncoding RNAs. It affects the fates of modified RNAs, including their stability, splicing, and/or translation, and thus plays important roles in posttranscriptional regulation. To date, m6A methyltransferases have been reported to execute m6A deposition on distinct RNAs by their own or forming different complexes with additional partner proteins. In this review, we summarize the function of these m6A methyltransferases or complexes in regulating the key genes and pathways of cancer biology. We also highlight the progress in the use of m6A methyltransferases in mediating therapy resistance, including chemotherapy, targeted therapy, immunotherapy and radiotherapy. Finally, we discuss the current approaches and clinical potential of m6A methyltransferase-targeting strategies.

Intra-arterial infusion chemotherapy utilizing cisplatin inhibits bladder cancer by decreasing the fibrocytic myeloid-derived suppressor cells in an m6A-dependent manner

Intra-arterial infusion chemotherapy (IAIC), using immunomodulatory cisplatin, is a novel treatment for bladder cancer (BC) that allows the delivery of specific drugs to the local malignant lesion. To explore the immunomodulatory effect of cisplatin during IAIC, we detected the proportion of immunosuppressed cells in BC tissue from eight BC patients, with the reduction of myeloid-derived suppressor cells (MDSCs), more specifically fibrocytic-MDSCs (f-MDSCs). Further, we demonstrated that cisplatin inhibits their proliferation and immunosuppressive activity. f-MDSCs promote tumor proliferation and metastasis in the BC immune environment. Then, we analyzed the genetic differences detected in samples before and after chemotherapy and found that granulocyte colony-stimulating factors (G-CSF) decreased after IAIC. Furthermore, G-CSF methylation decreased following treatment with cisplatin. Specifically, treatment with cisplatin decreased the methylase (METTL3) levels in BC cells, which is important for G-CSF production. Collectively, cisplatin decreased the number of f-MDSCs during IAIC, by blocking G-CSF methylation via targeting METTL3.

Role of RNA N6-Methyladenosine Modification in Male Infertility and Genital System Tumors

Epigenetic alterations, particularly RNA methylation, play a crucial role in many types of disease development and progression. Among them, N6-methyladenosine (m6A) is the most common epigenetic RNA modification, and its important roles are not only related to the occurrence, progression, and aggressiveness of tumors but also affect the progression of many non-tumor diseases. The biological effects of RNA m6A modification are dynamically and reversibly regulated by methyltransferases (writers), demethylases (erasers), and m6A binding proteins (readers). This review summarized the current finding of the RNA m6A modification regulators in male infertility and genital system tumors and discussed the role and potential clinical application of the RNA m6A modification in spermatogenesis and male genital system tumors.

N6-methyladenosine (m6A) methyltransferase KIAA1429 accelerates the gefitinib resistance of non-small-cell lung cancer

N6-methyladenosine (m6A) modification has been convincingly identified to be a critical regulator in human cancer. However, the contribution of m6A to NSCLC gefitinib resistance is still largely unknown. Here, we screened and identified that m6A methyltransferase KIAA1429 was highly expressed in gefitinib-resistant NSCLC cells (PC9-GR), tissues, and closely related to unfavorable survival. Functionally, KIAA1429 accelerated the gefitinib resistance of NSCLC in vitro. Depletion of KIAA1429 repressed the tumor growth of PC9-GR cells in vivo. Mechanistically, KIAA1429 enhanced the mRNA stability of HOXA1 through targeting its 3'-untranslated regions (3'-UTR). Overall, our findings indicate that KIAA1429 plays essential oncogenic roles in NSCLC gefitinib resistance, which may provide a feasible therapeutic target for NSCLC.

N6-Methyladenosine, DNA Repair, and Genome Stability

N⁶-methyladenosine (m⁶A) modification in mRNAs and non-coding RNAs is a newly identified epitranscriptomic mark. It provides a fine-tuning of gene expression to serve as a cellular response to endogenous and exogenous stimuli. m⁶A is involved in regulating genes in multiple cellular pathways and functions, including circadian rhythm, cell renewal, differentiation, neurogenesis, immunity, among others. Disruption of m⁶A regulation is associated with cancer, obesity, and immune diseases. Recent studies have shown that m⁶A can be induced by oxidative stress and DNA damage to regulate DNA repair. Also, deficiency of the m⁶A eraser, fat mass obesity-associated protein (FTO) can increase cellular sensitivity to genotoxicants. These findings shed light on the novel roles of m⁶A in modulating DNA repair and genome integrity and stability through responding to DNA damage. In this mini-review, we discuss recent progress in the understanding of a unique role of m⁶As in mRNAs, lncRNAs, and microRNAs in DNA damage response and regulation of DNA repair and genome integrity and instability.

The m6A methyltransferase METTL3 regulates autophagy and sensitivity to cisplatin by targeting ATG5 in seminoma

Background

Our previous work shows Autophagy enhanced resistance to cisplatin in seminoma. The expression of the N6-methyladenosine (m6A) methyltransferases METTL3 was significantly increased in the cisplatin-resistant TCam-2 cell line of seminoma. We aimed to investigate the role of m6A methylation in autophagy and the chemosensitivity of seminoma cells.

Methods

Plasmid and siRNA were used to overexpress and knockdown METTL3. Autophagy was detected by western blot and immunofluorescence, respectively. The expression of downstream targets of METTL3 was detected by quantitative real-time PCR (qRT-PCR) and western blot, and the m6A level of them was detected by MeRIP-qPCR. Chemosensitivity of the TCam-2 cell line was identified through MTT assay.

Results

Upon METTL3 overexpression, autophagy of TCam-2 cell line was enhanced and its sensitivity to cisplatin was decreased. The use of autophagy inhibitors 3-methyladenine (3-MA) could reverse the protective effect of METTL3 on TCam-2 cells. We found that the up-regulation of METTL3 could increase the m6A modification level of ATG5 transcript, thus increased expression of ATG5. Moreover, knockdown of ATG5 reduced METTL3-induced autophagy, suggesting that ATG5 was a potential target for METTL3 to promote autophagy.

Conclusions

In summary, our research unveiled the unique mechanism by which m6A methylation regulates autophagy and chemosensitivity of the TCam-2 cell line and METTL3 was a potential target to overcome the cisplatin resistance of seminoma.

Effects of Quercetin on the Efficacy of Various Chemotherapeutic Drugs in Cervical Cancer Cells

Purpose

This study aimed to investigate the effects of quercetin on the efficacy of various chemotherapeutic drugs in cervical cancer cells.

Methods

All drug experiments were performed in HeLa and SiHa cells. The cell viability was detected by Cell Counting Kit-8 assay, and cell proliferation was estimated by bromodeoxyuridine assay. CompuSyn software was utilized to calculate the combination index (CI) and evaluate the synergistic or antagonistic effect of quercetin with cisplatin, paclitaxel, 5-fluorouracil and doxorubicin on cell viability. Cell migration and invasion abilities were detected by transwell assays, and cell apoptosis was measured by flow cytometry. The expression levels of matrix metallopeptidase 2 (MMP2), ezrin, P-glycoprotein (P-Gp) and methyltransferase-like 3 (METTL3) protein treated with various drugs were analyzed by Western blotting.

Results

Quercetin inhibited the viability of HeLa and SiHa cells in a dose- and time-dependent manner. The CI values of quercetin with cisplatin, paclitaxel, 5-fluorouracil and doxorubicin were <1, >1, >1 and >1, respectively. The effect of combination of quercetin and cisplatin on cell proliferation was stronger than their individual effects. Co-treatment group could inhibit more cell migration and invasion in contrast to single-drug group. Besides, quercetin combined with cisplatin group induced more cell apoptosis in contrast to single-drug group. The results of Western blotting showed that the expression levels of MMP2, ezrin, P-Gp and METTL3 in co-treatment group were lower than in cisplatin group, respectively.

Conclusion

Quercetin and cisplatin had synergistic inhibitory effect on cervical cancer cells. Quercetin might enhance the antitumor effect of cisplatin via inhibiting proliferation, migration and invasion and elevating apoptosis through weakening MMP2, ezrin, METTL3 and P-Gp expression of cancer cells.

Dual effects of N6-methyladenosine on cancer progression and immunotherapy

According to the latest global cancer statistics, cancer has become a major threat to human health, but cancer treatment has encountered many bottlenecks. As an emerging topic in epigenetics, N⁶-methyladenosine (m⁶A) is the most common internal modification on eukaryotic mRNA, which has attracted increasing attention in recent years. Accumulating studies have shown that aberrant m⁶A modifications have profound effects on the characteristics of tumors, which undoubtedly led to a significant breakthrough in cancer treatment. Although m⁶A function as an oncogene or tumor suppressor is not fully revealed, determining its precise function in the development and evolution of malignant tumors is crucial in improving clinical decisions involving targeted therapies. In this review, we briefly introduce the composition of the m⁶A methylation machinery and mainly summarize the biological mechanism of m⁶A in cancer cell death, angiogenesis, epithelial-mesenchymal transition (EMT), and therapeutic resistance. Subsequently, we present the exogenous regulatory factors of m⁶A and highlight the role of m⁶A on immune cells and cancer immunotherapy. The potential therapeutic strategies of m⁶A in human cancer are also discussed, considering research gaps and future applications.

METTL3 potentiates resistance to cisplatin through m6 A modification of TFAP2C in seminoma

Testicular germ cell tumours (TGCTs) rank as the most common malignancy in men aged 20‐34 years, and seminomas are the most type of TGCTs. As a crucial anti‐tumour agent with explicit toxicity, cisplatin may render resistance through intertwined mechanisms, even in disease entities with high curative ratio, such as seminoma. Previously, we established cisplatin‐resistant seminoma TCam‐2 (TCam‐2/CDDP) cells and showed that epigenetic regulations, such as non‐coding RNA (ncRNA) interactions, might orchestrate cell fate decisions in the cisplatin treatment context in seminoma. N6‐methyladenosine (m6A) is the most prevalent internal modification in mRNA. In the present study, we assessed cisplatin resistance in seminoma from the perspective of m⁶A, another manner of epigenetic modification. The global m⁶A enrichment of TCam‐2 and TCam‐2/CDDP was depicted. Then, we elucidated whether transcription factor‐activating enhancer‐binding protein 2C (TFAP2C) was functionally m⁶A‐modified by methyltransferase‐like protein 3 (METTL3), which acted as an m⁶A ‘writer’, and insulin‐like growth factor 2 mRNA‐binding protein 1 (IGF2BP1), which acted as an m⁶A ‘reader’. Enhanced stability of TFAP2C mRNA promoted seminoma cell survival under cisplatin treatment burden probably through up‐regulation of DNA repair‐related genes. Hopefully, this study will help improve our understanding of the subtleties of the tumour cellular coping strategy in response to chemotherapy. Targeting factors that are involved in m⁶A methylation may be an effective strategy for circumventing cisplatin resistance in seminoma.