m6A-Mediated Stabilization of PRMT9 mRNA by IGF2BP1 Drives Proliferation and Metastasis in Lung Adenocarcinoma.

Background: Protein arginine methyltransferase 9 (PRMT9) is dysregulated in various malignancies, particularly in lung adenocarcinoma (LUAD). This study aims to systematically investigate the expression patterns, biological functions, and underlying molecular mechanisms of PRMT9 in LUAD pathogenesis. Methods: PRMT9 expression was evaluated in paired clinical LUAD specimens and adjacent normal tissues, as well as in normal alveolar epithelial cells versus established lung cancer cell lines. Genetic silencing of PRMT9 was performed in A549 and H1568 cell models to assess its functional impact. Cellular migratory and invasive capacities were quantified using wound healing and Transwell invasion assays. The mechanism of PRMT9 overexpression was explored by examining m6A-mediated mRNA modification. The role of IGF2BP1 was determined through loss-of-function and gain-of-function experiments, supplemented with studies under PRMT9-deficient conditions. Downstream signaling was investigated using specific inhibitors targeting the RAS and MAPK pathways, with in vivo validation in xenograft models. Results: PRMT9 was significantly upregulated at both transcriptional and translational levels in LUAD tissues and cancer cell lines compared to normal controls. Genetic depletion of PRMT9 substantially impaired cell migration and invasion, and suppressed activation of the RAS/MEK/ERK signaling pathway. The aberrant expression of PRMT9 was mechanistically linked to IGF2BP1-regulated m6A modification. IGF2BP1 was similarly overexpressed in LUAD specimens and cell models. Knockdown of IGF2BP1 reduced PRMT9 m6A modification, compromised cell viability, migration, and invasion, and attenuated RAS/MEK/ERK signaling. Conversely, IGF2BP1 overexpression enhanced malignant behaviors, effects that were reversed by concurrent PRMT9 knockdown. Mechanistically, PRMT9 overexpression activated the RAS/MAPK signaling axis, and pharmacological inhibition of this pathway mitigated PRMT9-mediated metastatic progression. In vivo studies confirmed that PRMT9 suppression inhibited tumor growth, which was associated with decreased expression of RAS, pMek1/2, pErk1/2, and Ki67, alongside enhanced caspase-3 expression. Conclusion: PRMT9 is overexpressed in LUAD and promotes malignant progression by activating the RAS/MAPK signaling cascade. This aberrant PRMT9 expression is governed by IGF2BP1-mediated m6A modification. These findings suggest that therapeutic targeting of PRMT9 or the RAS/MAPK signaling axis may represent a promising strategy for LUAD treatment.