METTL3- and IGF2BP1-associated m6A regulation of FADS2 contributes to lipid droplet accumulation and malignant progression in non-small cell lung cancer.

Background: Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related mortality worldwide, and its underlying molecular mechanisms remain incompletely defined. N6-methyladenosine (m6A) RNA modification has emerged as a key epigenetic regulator of tumor metabolic reprogramming. However, the roles of the m6A writer methyltransferase-like 3 (METTL3) and the m6A reader insulin-like growth factor 2 mRNA-binding protein 1 (IGF2BP1) in NSCLC, particularly in lipid metabolic regulation, remain poorly characterized. The present study aimed to investigate the functional significance of METTL3 and IGF2BP1 in NSCLC, with particular focus on their regulation of FADS2 expression and lipid metabolism. Methods: Differentially expressed m6A-related genes were identified by analyzing RNA-seq data from The Cancer Genome Atlas (TCGA), followed by validation in 60 paired NSCLC and adjacent normal tissues. Gene and protein expression were examined by qRT-PCR and western blotting, respectively, with immunohistochemistry (IHC) further confirming protein levels in tissue specimens. Functional assays, including colony formation, Transwell migration/invasion, and Oil Red O staining, were performed in A549 and H1299 cells following METTL3, IGF2BP1, or FADS2 perturbation. The m6A modification on FADS2 mRNA was assessed by MeRIP-qPCR, and its association with METTL3 and IGF2BP1 was examined by RIP-qPCR. RNA stability was evaluated via actinomycin D chase assays, and rescue experiments were conducted through co-transfection of shRNA and overexpression constructs. The in vivo role of FADS2 was assessed using a xenograft tumor model. Results: METTL3 and IGF2BP1 were significantly upregulated in NSCLC tissues and were associated with poor overall survival. Silencing either gene inhibited NSCLC cell proliferation, migration, and invasion. FADS2 expression was markedly elevated in NSCLC and positively correlated with METTL3 and IGF2BP1 expression. Knockdown of FADS2 reduced lipid droplet accumulation and suppressed malignant phenotypes in vitro, while significantly inhibiting tumor growth in vivo. Mechanistically, m6A modification was enriched within the 3'-UTR of FADS2 mRNA, where both METTL3 and IGF2BP1 were found to bind. Loss of METTL3 or IGF2BP1 accelerated FADS2 mRNA decay, whereas their overexpression enhanced transcript stability. Rescue experiments further confirmed that METTL3 and IGF2BP1 cooperatively regulate FADS2 expression and thereby promote NSCLC progression. Conclusions: METTL3-mediated m6A modification of FADS2 transcripts is recognized by IGF2BP1, resulting in enhanced mRNA stability, increased lipid accumulation, and NSCLC progression. Our findings suggest that the METTL3/IGF2BP1-FADS2 axis contributes to lipid metabolic alterations in NSCLC and may serve as a potential therapeutic target.