METTL3 antagonizes 5‑FU chemotherapy and confers drug resistance in colorectal carcinoma

RNA epigenetic modifications in digestive tract cancers: Friends or foes

Digestive tract cancers are among the most common malignancies worldwide and have high incidence and mortality rates. Thus, the discovery of more effective diagnostic and therapeutic targets is urgently required. The development of technologies to accurately detect RNA modification has led to the identification of numerous RNA chemical modifications in humans (epitranscriptomics) that are involved in the occurrence and development of digestive tract cancers. RNA modifications can cooperatively regulate gene expression to facilitate normal physiological functions of the digestive system. However, the dysfunction of relevant RNA-modifying enzymes ("writers," "erasers," and "readers") can lead to the development of digestive tract cancers. Consequently, targeting dysregulated enzyme activity could represent a potent therapeutic strategy for the treatment of digestive tract cancers. In this review, we summarize the most widely studied roles and mechanisms of RNA modifications (m6A, m1A, m5C, m7G, A-to-I editing, pseudouridine [Ψ]) in relation to digestive tract cancers, highlight the crosstalk between RNA modifications, and discuss their roles in the interactions between the digestive system and microbiota during carcinogenesis. The clinical significance of novel therapeutic methods based on RNA-modifying enzymes is also discussed. This review will help guide future research into digestive tract cancers that are resistant to current therapeutics.

Autophagy-driven regulation of cisplatin response in human cancers: Exploring molecular and cell death dynamics

Despite the challenges posed by drug resistance and side effects, chemotherapy remains a pivotal strategy in cancer treatment. A key issue in this context is macroautophagy (commonly known as autophagy), a dysregulated cell death mechanism often observed during chemotherapy. Autophagy plays a cytoprotective role by maintaining cellular homeostasis and recycling organelles, and emerging evidence points to its significant role in promoting cancer progression. Cisplatin, a DNA-intercalating agent known for inducing cell death and cell cycle arrest, often encounters resistance in chemotherapy treatments. Recent studies have shown that autophagy can contribute to cisplatin resistance or insensitivity in tumor cells through various mechanisms. This resistance can be mediated by protective autophagy, which suppresses apoptosis. Additionally, autophagy-related changes in tumor cell metastasis, particularly the induction of Epithelial-Mesenchymal Transition (EMT), can also lead to cisplatin resistance. Nevertheless, pharmacological strategies targeting the regulation of autophagy and apoptosis offer promising avenues to enhance cisplatin sensitivity in cancer therapy. Notably, numerous non-coding RNAs have been identified as regulators of autophagy in the context of cisplatin chemotherapy. Thus, therapeutic targeting of autophagy or its associated pathways holds potential for restoring cisplatin sensitivity, highlighting an important direction for future clinical research.

Desulfovibrio desulfuricans and its derived metabolites confer resistance to FOLFOX through METTL3

BACKGROUND

Chemoresistance is a critical factor contributing to poor prognosis in clinical patients with cancer undergoing postoperative adjuvant chemotherapy. The role of gut microbiota in mediating resistance to tumour chemotherapy remains to be investigated.

METHODS

Patients with CRC were categorised into clinical benefit responders (CBR) and no clinical benefit responders (NCB) based on chemotherapy efficacy. Differential bacterial analysis using 16S rRNA sequencing revealed Desulfovibrio as a distinct microbe between the two groups. Employing a syngeneic transplantation model, we assessed the effect of Desulfovibrio on chemotherapy by measuring tumour burden, weight, and Ki-67 expression. We further explored the mechanisms underlying the compromised chemotherapeutic efficacy of Desulfovibrio using metabolomics, western blotting, colony formation, and cell apoptosis assays.

FINDINGS

In comparison, Desulfovibrio was more abundant in the NCB group. In vivo experiments revealed that Desulfovibrio colonisation in the gut weakened the efficacy of FOLFOX. Treatment with Desulfovibrio desulfuricans elevates serum S-adenosylmethionine (SAM) levels. Interestingly, SAM reduced the sensitivity of CRC cells to FOLFOX, thereby promoting the growth of CRC tumours. These experiments suggest that SAM promotes the growth and metastasis of CRC by driving the expression of methyltransferase-like 3 (METTL3).

INTERPRETATION

A high abundance of Desulfovibrio in the intestines indicates poor therapeutic outcomes for postoperative neoadjuvant FOLFOX chemotherapy in CRC. Desulfovibrio drives the manifestation of METTL3 in CRC, promoting resistance to FOLFOX chemotherapy by increasing the concentration of SAM.

FUNDING

This study is supported by Wuxi City Social Development Science and Technology Demonstration Project (N20201005).

Targeting key RNA methylation enzymes to improve the outcome of colorectal cancer chemotherapy (Review)

RNA methylation modifications are closely linked to tumor development, migration, invasion and responses to various therapies. Recent studies have shown notable advancements regarding the roles of RNA methylation in tumor immunotherapy, the tumor microenvironment and metabolic reprogramming. However, research on the association between tumor chemoresistance and N6‑methyladenosine (m6A) methyltransferases in specific cancer types is still scarce. Colorectal cancer (CRC) is among the most common gastrointestinal cancers worldwide. Conventional chemotherapy remains the predominant treatment modality for CRC and chemotherapy resistance is the primary cause of treatment failure. The expression levels of m6A methyltransferases, including methyltransferase‑like 3 (METTL3), METTL14 and METTL16, in CRC tissue samples are associated with patients' clinical outcomes and chemotherapy efficacy. Natural pharmaceutical ingredients, such as quercetin, have the potential to act as METTL3 inhibitors to combat chemotherapy resistance in patients with CRC. The present review discussed the various roles of different types of key RNA methylation enzymes in the development of CRC, focusing on the mechanisms associated with chemotherapy resistance. The progress in the development of certain inhibitors is also listed. The potential of using natural remedies to develop antitumor medications that target m6A methylation is also outlined.

PFKP is upregulated in 5-fluorouracil-resistant patients and suppresses the antitumor activity of 5-fluorouracil in colorectal cancer in vitro and in vivo

As a long-established chemotherapy drug, 5-fluorouracil (5-FU) is widely used to clinically manage colorectal cancer (CRC). However, a substantial portion of patients develop 5-FU resistance at some stage, which poses a great challenge. Therefore, revealing the mechanisms that could guide the development of effective strategies to overcome 5-FU resistance is required. Here, we report that the expression of PFKP was higher in HCT116/5-FU CRC. Furthermore, genetic suppression of PFKP suppresses glycolysis, NF-κB activation, and expression of GLUT1 and HK2 in HCT116/5-FU cells. PFKP overexpression promotes glycolysis and expression of GLUT1 and HK2 via the NF-κB signaling pathway in HCT116 cells. Our functional assays demonstrated that PFKP silencing could sensitize HCT116/5-FU cells to 5-FU with an elevated population of apoptotic cells. In contrast, forced expression of PFKP conferred 5-FU resistance in HCT116 cells. Furthermore, PFKP silencing significantly inhibited CRC xenograft tumor growth. Notably, the combination of PFKP silencing and 5-FU inhibited tumor growth. Therefore, our results demonstrated that PFKP enhances 5-FU resistance by promoting glycolysis, indicating that PFKP could be a novel candidate for targeted therapy for 5-FU-resistant CRC.

New insights into the regulation of METTL3 and its role in tumors

As one of the most abundant epigenetic modifications in RNA, N6-methyladenosine (m6A) affects RNA transcription, splicing, stability, and posttranscriptional translation. Methyltransferase-like 3 (METTL3), a key component of the m6A methyltransferase complex, dynamically regulates target genes expression through m6A modification. METTL3 has been found to play a critical role in tumorigenesis, tumor growth, metastasis, metabolic reprogramming, immune cell infiltration, and tumor drug resistance. As a result, the development of targeted drugs against METTL3 is becoming increasingly popular. This review systematically summarizes the factors that regulate METTL3 expression and explores the specific mechanisms by which METTL3 affects multiple tumor biological behaviors. We aim to provide fundamental support for tumor diagnosis and treatment, at the same time, to offer new ideas for the development of tumor-targeting drugs.

Colitis-associated carcinogenesis: crosstalk between tumors, immune cells and gut microbiota

Colorectal cancer (CRC) is the third most common cancer worldwide. One of the main causes of colorectal cancer is inflammatory bowel disease (IBD), which includes ulcerative colitis (UC) and Crohn's disease (CD). Intestinal epithelial cells (IECs), intestinal mesenchymal cells (IMCs), immune cells, and gut microbiota construct the main body of the colon and maintain colon homeostasis. In the development of colitis and colitis-associated carcinogenesis, the damage, disorder or excessive recruitment of different cells such as IECs, IMCs, immune cells and intestinal microbiota play different roles during these processes. This review aims to discuss the various roles of different cells and the crosstalk of these cells in transforming intestinal inflammation to cancer, which provides new therapeutic methods for chemotherapy, targeted therapy, immunotherapy and microbial therapy.

METTL3 promotes drug resistance to oxaliplatin in gastric cancer cells through DNA repair pathway

Gastric cancer (GC) poses a significant threat to human health and remains a prevalent form of cancer. Despite clinical treatments, the prognosis for Gastric cancer patients is still unsatisfactory, largely due to the development of multidrug resistance. Oxaliplatin (OXA), a second-generation platinum drug, is commonly recommended for adjuvant and palliative chemotherapy in Gastric cancer; however, the underlying mechanisms of acquired resistance to Oxaliplatin in Gastric cancer patients are not yet fully understood. In this study, we aimed to explore the potential mechanisms of Oxaliplatin resistance in Gastric cancer by employing bioinformatics analysis and conducting in vitro experiments. Specifically, we focused on investigating the role of methyltransferase-like 3 (METTL3). Our findings revealed that the knockdown of METTL3 significantly impeded the proliferation and migration of Gastric cancer cells. METTL3 knockdown induced apoptosis in OXA-resistant Gastric cancer cells and enhanced their sensitivity to Oxaliplatin. Furthermore, we found that DNA repair pathways were significantly activated in OXA-resistant Gastric cancer cells, and METTL3 knockdown significantly inhibited DNA repair pathways. Another important finding is that METTL3 knockdown and OXA-induced Gastric cancer cell death are additive, and the targeted METTL3 can assist Oxaliplatin treatment. Collectively, our findings suggest that METTL3 knockdown can augment the sensitivity of Gastric cancer cells to Oxaliplatin by impeding DNA repair processes. Consequently, targeting METTL3 holds great promise as a viable adjuvant strategy in the treatment of Gastric cancer patients.

[Research Advances of RAD51AP1 in Tumor Progression and Drug Resistance]

The genomic instability may lead to an initiation of cancer in many organisms. Homologous recombination repair (HRR) is vital in maintaining cellular genomic stability. RAD51 associated protein 1 (RAD51AP1), which plays a crucial role in HRR and primarily participates in forming D-loop, was reported as an essential protein for maintaining cellular genomic stability. However, recent studies showed that RAD51AP1 was significantly overexpressed in various cancer types and correlated with poor prognosis. These results suggested that RAD51AP1 may play a significant pro-cancer effect in multiple cancers. The underlying mechanism is still unclear. Cancer stemness-maintaining effects of RAD51AP1 might be considered as the most reliable mechanism. Meanwhile, RAD51AP1 also promoted resistance to radiation therapy and chemotherapy in many cancers. Thus, researches focused on RAD51AP1, and its regulatory molecules may provide new targets for overcoming cancer progression and treatment resistance. Here, we reviewed the latest research on RAD51AP1 in cancers and summarized its differential expression and prognostic implications. In this review, we also outlined the potential mechanisms of its pro-cancer and drug resistance-promoting effects to provide several potential directions for further research.
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Methyltransferase-like proteins in cancer biology and potential therapeutic targeting

RNA modification has recently become a significant process of gene regulation, and the methyltransferase-like (METTL) family of proteins plays a critical role in RNA modification, methylating various types of RNAs, including mRNA, tRNA, microRNA, rRNA, and mitochondrial RNAs. METTL proteins consist of a unique seven-beta-strand domain, which binds to the methyl donor SAM to catalyze methyl transfer. The most typical family member METTL3/METTL14 forms a methyltransferase complex involved in N6-methyladenosine (m6A) modification of RNA, regulating tumor proliferation, metastasis and invasion, immunotherapy resistance, and metabolic reprogramming of tumor cells. METTL1, METTL4, METTL5, and METTL16 have also been recently identified to have some regulatory ability in tumorigenesis, and the rest of the METTL family members rely on their methyltransferase activity for methylation of different nucleotides, proteins, and small molecules, which regulate translation and affect processes such as cell differentiation and development. Herein, we summarize the literature on METTLs in the last three years to elucidate their roles in human cancers and provide a theoretical basis for their future use as potential therapeutic targets.

Clostridium butyricum inhibits epithelial-mesenchymal transition of intestinal carcinogenesis through downregulating METTL3

Colorectal cancer (CRC) is related to gut microbiota dysbiosis, especially butyrate-producing bacteria reduction. Our previous study suggested that administration of Clostridium butyricum, a butyrate-producing bacterium, exerts a crucial effect against CRC, however the potential mechanism is not clear. We first found that methyltransferase-like 3 (METTL3) showed a positive correlation with proliferation, epithelial-mesenchymal transition (EMT), DNA repair, metastasis, and invasion in a database analysis. The expression of METTL3 gradually increased from human normal colon tissue, to adenoma, and carcinoma, and was positively correlated with E-cadherin and CD34 levels. Overexpression of METTL3 promoted the proliferation, migration, and invasion of CRC cells and induced vasculogenic mimicry (VM) formation. Clostridium butyricum could downregulate METTL3 expression in CRC cells and decrease the expression of vimentin and vascular endothelial growth factor receptor 2 to reduce EMT and VM formation. Clostridium butyricum alleviated the pro-oncogenic effect of METTL3 overexpressing plasmid in CRC cells. The anti-EMT effect on METTL3 reduction of C. butyricum could be blunted by knocking down G-protein coupled receptor 43. Moreover, C. butyricum prevented EMT and VM and inhibited tumor metastasis in nude mice. Accordingly, C. butyricum could inhibit EMT and VM formation of intestinal carcinogenesis through downregulating METTL3. These findings broaden our understanding of probiotics supplement in CRC prevention and treatment.

The diverse role of RNA methylation in esophageal cancer

Esophageal cancer is one of the major life-threatening diseases in the world. RNA methylation is the most common post-transcriptional modification and a wide-ranging regulatory system controlling gene expression. Numerous studies have revealed that dysregulation of RNA methylation is critical for cancer development and progression. However, the diverse role of RNA methylation and its regulators in esophageal cancer remains to be elucidated and summarized. In this review, we focus on the regulation of major RNA methylation, including m ⁶A, m ⁵C, and m ⁷G, as well as the expression patterns and clinical implications of its regulators in esophageal cancer. We systematically summarize how these RNA modifications affect the "life cycle" of target RNAs, including mRNA, microRNA, long non-coding RNA, and tRNA. The downstream signaling pathways associated with RNA methylation during the development and treatment of esophageal cancer are also discussed in detail. Further studies on how these modifications function together in the microenvironment of esophageal cancer will draw a clearer picture of the clinical application of novel and specific therapeutic strategies.