M7G methylated core genes (METTL1 and WDR4) and associated RNA risk signatures are associated with prognosis and immune escape in HCC

Functions of METTL1/WDR4 and QKI as m7G modification - related enzymes in digestive diseases

N7-methylguanosine (m7G) modification is one of the most prevalent forms of chemical modification in RNA molecules, which plays an important role in biological processes such as RNA stability, translation regulation and ribosome recognition. Methyl-transferation of m7G modification is catalyzed by the enzyme complex of methyltransferase-like 1 (METTL1) and WD repeat domain 4 (WDR4), and Quaking (QKI) recognizes internal m7G methylated mRNA and regulates mRNA translation and stabilization. Recent studies have found that m7G modification - related enzymes are associated with the onset and progression of digestive cancer, such as colorectal cancer, liver cancer, and other digestive diseases such as ulcerative colitis. This review will focus on the latest research progress on the roles of m7G methyltransferase METTL1/WDR4 and recognized enzyme QKI in digestive diseases.

METTL Family in Healthy and Disease

Transcription, RNA splicing, RNA translation, and post-translational protein modification are fundamental processes of gene expression. Epigenetic modifications, such as DNA methylation, RNA modifications, and protein modifications, play a crucial role in regulating gene expression. The methyltransferase-like protein (METTL) family, a constituent of the 7-β-strand (7BS) methyltransferase subfamily, is broadly distributed across the cell nucleus, cytoplasm, and mitochondria. Members of the METTL family, through their S-adenosyl methionine (SAM) binding domain, can transfer methyl groups to DNA, RNA, or proteins, thereby impacting processes such as DNA replication, transcription, and mRNA translation, to participate in the maintenance of normal function or promote disease development. This review primarily examines the involvement of the METTL family in normal cell differentiation, the maintenance of mitochondrial function, and its association with tumor formation, the nervous system, and cardiovascular diseases. Notably, the METTL family is intricately linked to cellular translation, particularly in its regulation of translation factors. Members represent important molecules in disease development processes and are associated with patient immunity and tolerance to radiotherapy and chemotherapy. Moreover, future research directions could include the development of drugs or antibodies targeting its structural domains, and utilizing nanomaterials to carry miRNA corresponding to METTL family mRNA. Additionally, the precise mechanisms underlying the interactions between the METTL family and cellular translation factors remain to be clarified.

Anti-PD-1 therapy reverses TIGIT+CD226+NK depletion in immunotherapy resistance of hepatocellular carcinoma through PVR/TIGIT pathway

Immunotherapy resistance conducts the main reason for failure of PD-1-based immune checkpoint inhibitors (ICIs) in patients with hepatocellular carcinoma (HCC). This study aims to clarify the mechanism of nature kill cells (NK) depletion in immunotherapy resistance of HCC. Cancerous /paracancerous tissues and peripheral blood (PB) of 55 HCC patients were collected and grouped according to differentiation degree, FCM, IHC and lymphocyte culture drug intervention experiments were used to determine NK cell depletion degree. Furthermore, a mouse model of HCC in situ was constructed and divided into different groups according to intervention measures of ICIs. Immunofluorescence thermography was used to observe changes in tumor burden. NK cells in cancerous tissues significantly up-regulated TIGIT expression (P < 0.001). Intervention experiments revealed that TIGIT and PD-1 expression decreased gradually with increased PD-1 inhibitor dose in moderately-highly differentiated patients (P < 0.05). Animal experiment showed that tumors proliferation in experimental group was inhibited after PD-1 blockage, WB indicated that ICIs decreased TIGIT and PVRL1 protein expression while increased CD226 and PVRL3 protein expression. We concluded that TIGIT+NK cells competitively bind to PVR with CD226 and promote NK cell depletion. Anti-PD-1 decreases PVRL1 expression through PD-1/PD-L1 pathway, reducing the PVR/TIGIT inhibitory signal pathway, and enhancing function of PVR/CD226 activation signal.