The immunological landscape and silico analysis of key paraptosis regulator LPAR1 in gastric cancer patients.

This study aims to identify key regulators of paraptosis in gastric cancer (GC) and explore their potential in guiding therapeutic strategies, especially in stomach adenocarcinoma (STAD). Genes associated with paraptosis were identified from the references and subjected to Cox regression analysis in the TCGA-STAD cohort. Using machine learning models, LPAR1 consistently ranked highest in feature importance. Multiple sequencing data showed that LPAR1 was significantly overexpressed in cancer-associated fibroblasts (CAFs). LPAR1 expression was significantly higher in normal tissues, and ROC analysis demonstrated its discriminative ability. Copy number alterations and microsatellite instability were significantly associated with LPAR1 expression. High LPAR1 expression correlated with advanced tumor grades and specific cancer immune subtypes, and multivariate analysis confirmed LPAR1 as an independent predictor of poor prognosis. LPAR1 expression was associated with different immune response metrics, including immune effector activation and upregulated chemokine secretion. High LPAR1 expression also correlated with increased sensitivity to compounds, such as BET bromodomain inhibitors I-BET151 and RITA, suggesting LPAR1 as a biomarker for predicting drug activity. FOXP2 showed a strong positive correlation with LPAR1 transcriptional regulation, while increased methylation of LPAR1 promoter regions was negatively correlated with gene expression. Knockdown of LPAR1 affected cell growth in most tumor cell lines, and in vitro experiments demonstrated that LPAR1 influenced extracellular matrix (ECM) contraction and cell viability in the paraptosis of CAFs. These findings suggest that LPAR1 is a critical regulator of paraptosis in GC and a potential biomarker for drug sensitivity and immunotherapy response. This underscores the role of CAFs in mediating tumorigenic effects and suggests that targeting LPAR1 could be a promising strategy for precision medicine in GC.

Specific deletion of Mettl3 in IECs triggers the development of spontaneous colitis and dysbiosis of T lymphocytes in mice.

The enzymatic core component of m6A writer complex, Mettl3, plays a crucial role in facilitating the development and progress of gastric and colorectal cancer (CRC). However, its underlying mechanism in regulating intestinal inflammation remains unclear and poorly investigated. First, the characteristics of Mettl3 expression in inflammatory bowel diseases (IBD) patients were examined. Afterward, we generated the mice line with intestinal epithelial cells (IECs)-specific deletion of Mettl3 verified by various experiments. We continuously recorded and compared the physiological status including survival rate etc. between the two groups. Subsequently, we took advantage of staining assays to analyze mucosal damage and immune infiltration of Mettl3WT and Mettl3KO primary IECs. Bulk RNA sequencing was used to pursuit the differential expression of genes (DEGs) and associated signaling pathways after losing Mettl3. Pyroptosis-related proteins were to determine whether cell death was caused by pyroptosis. Eventually, CyTOF was performed to probe the difference of CD45+ cells, especially CD3e+ T-cell clusters after losing Mettl3. In IBD patients, Mettl3 was highly expressed in the inner-nucleus of IECs while significantly decreased upon acute intestinal inflammation. IECs-specific deletion of Mettl3 KO mice triggered a wasting phenotype and developed spontaneous colitis. The survival rate, body weight, and intestinal length observed from 2 to 8 weeks of Mettl3KO mice were significantly lower than Mettl3WT mice. The degree of mucosal damage and immune infiltration in Mettl3KO were even more serious than in their WT littermate. Bulk RNA sequencing demonstrated that DEGs were dramatically enriched in NOD-signaling pathways due to the loss of Mettl3. The colonic epithelium was more prone to pyroptosis after losing Mettl3. Subsequently, CyTOF revealed that T cells have altered significantly in Mettl3KO. Furthermore, there was abnormal proliferation of CD4+ T and markedly exhaustion of CD8 + T in Mettl3KO mice. In severe IBD patients, Mettl3 is located in the inner-nucleus of IECs and declined when intestinal inflammation occurs. Subsequently, Mettl3 prevented mice from developing colitis.

Intestinal Epithelial Cell-specific Knockout of METTL3 Aggravates Intestinal Inflammation in CLP Mice by Weakening the Intestinal Barrier.

BACKGROUND: Many studies have demonstrated that the expression of methyltransferase- like 3 (METTL3) is altered in various inflammatory diseases. Its specific mechanistic role in the intestinal inflammatory response during sepsis remains limited and requires further investigation. OBJECTIVES: Explore the potential mechanism of METTL3 in the intestinal inflammatory response during sepsis. MATERIALS AND METHODS: Immunohistochemical analysis was utilized to detect the expression of METTL3 in the necrotic intestine of patients with intestinal necrosis and the small intestine of cecal ligation and puncture (CLP) mice. Mice were subjected to the CLP and Sham surgeries, intestine tissue was harvested and performed HE staining, and ELISA to examine intestinal inflammatory responses, while TUNEL staining was applied to detect intestinal cell apoptosis. Additionally, ELISA was used to detect diamine oxidase (DAO) and intestinal fatty acid binding protein (I-FABP) levels in intestinal tissue. Immunohistochemistry and RT-qPCR were also employed to examine the mRNA and protein expression levels of Zona Occludens 1 (ZO-1) and Claudin-1. Finally, transcriptomic sequencing was performed on the small intestine tissues of METTL3 Knock-out (KO) and Wild-type (WT) mice in response to sepsis. RESULTS: METTL3 exhibited lower expression level in the necrotic intestine of patients and the small intestine of CLP mice. Loss of METTL3 in CLP mice triggered significantly higher expression of TNF-α and IL-18, down-regulated expression of ZO-1 and claudin-1, and decreased expression of DAO and I-FABP in the intestinal tissue. KEGG enrichment analysis showed that the differential genes were significantly enriched in immune-related pathways. CONCLUSION: This study reveals a novel mechanism responsible for exacerbated intestinal inflammation orchestrated by METTL3. Particularly, METTL3 null mice displayed decreased ZO- 1 and Claudin-1 expression, which largely hampered intestinal epithelial barrier function, resulting in bacterial and toxin translocation and intestinal immune activation and inflammation against sepsis.