LncRNA MALAT1 promotes METTL3-mediated m6A modification to promote progression in non-small cell lung cancer

Objective: This study aims to examine whether lncRNA MALAT1 targets METTL3 and modulates its expression, subsequently influencing the expression of INPP5B and LRIG2 genes. Additionally, the research seeks to determine how these interactions regulate the tumor immune microenvironment and impact the progression of non-small cell lung cancer (NSCLC). Methods: Non-small cell lung cancer cells (NCI-H226) served as the experimental model in this study. The cells were transfected with si-MALAT1 and OE-METTL3 constructs. Fluorescence in situ hybridization (FISH) was employed to determine the subcellular localization of MALAT1. Apoptosis was quantified using flow cytometry, whereas cell proliferation was assessed through the 5-ethynyl-2'-deoxyuridine (EDU) incorporation assay. The Transwell assay was utilized to evaluate cell migration capability and m6A methylation levels. Quantitative PCR (qPCR) and Western blot (WB) analyses were conducted to measure the expression levels of cancer-related genes. Furthermore, an RNA immunoprecipitation (RIP) assay was conducted to validate the interaction between MALAT1 and METTL3. To investigate the functional implications of this interaction, a BALB/c nude mouse subcutaneous xenograft model was utilized, wherein NSCLC cells with silenced MALAT1 expression were employed, both with and without the overexpression of METTL3. Results: The MALAT1 is primarily localized within the nucleus. Under conditions of low expression, MALAT1 remains confined to the nucleus, whereas at elevated expression levels, it translocates to the cytoplasm. Following the application of siRNA targeting MALAT1 (si-MALAT1), a reduction in cell proliferation and migration capabilities was observed, although no significant change in cell colony formation ability was detected. Additionally, an increase in cell apoptosis was noted, with cells exhibiting arrest in the G0/G1 phase of the cell cycle. In parallel, the expression levels of MALAT1 and the oncogenic gene LRIG2 were both diminished, concomitant with a reduction in m6A methylation levels. Subsequent to the interference with MALAT1, transfection with a METTL3 overexpression vector led to a notable decrease in apoptosis, retention of cells in the S phase, and a significant downregulation of the tumor suppressor gene INPP5B. Results from the RIP assay indicated an interaction between MALAT1 and the MALAT1 protein. Furthermore, MALAT1 modulates the impact of METTL3 on the immune microenvironment of NSCLC tumors. Conclusion: The long non-coding RNA MALAT1 facilitates the progression of NSCLC and holds potential as a novel prognostic biomarker and therapeutic target.