METTL3 Promotes Intrahepatic Cholangiocarcinoma Progression by Enhancing S100A4 Expression in an m6A-Dependent Manner

Background: Intrahepatic cholangiocarcinoma (ICC) is a prevalent type of cancer originating from epithelial cells of the bile duct within the liver. The molecular mechanisms underlying ICC proliferation, invasion, and metastasis remain unclear. Recently, N6-methyladenosine (m6A) RNA methylation has been associated with tumor progression. Methyltransferase 3 (METTL3) is a crucial methyltransferase for m6A. However, its biological significance and the regulatory mechanisms underlying ICC invasion and metastasis remain poorly understood. Therefore, we aimed to explore the role of METTL3 in ICC progression and its potential mechanisms. Methods: We analyzed the expression of METTL3 in ICC using bioinformatics, quantitative reverse transcription polymerase chain reaction (qRT-PCR), and immunohistochemistry analysis. Furthermore, we evaluated the impact of METTL3 on ICC cell proliferation and metastasis in vivo and in vitro . For mechanistic studies, we used RNA-Seq to screen the crucial downstream targets of METTL3 in ICC cells. Furthermore, we examined the regulatory impact of METTL3 on the phenotype of ICC cells through S100 calcium-binding protein A4 (S100A4) using qRT-PCR, Western blot, and rescue experiments. Finally, we assessed the effect of METTL3 on S100A4 stability by mediating m6A modification using the methylated RNA immunoprecipitation qPCR (MeRIP-qPCR) and messenger RNA (mRNA) degradation experiments. Results: The expression of METTL3 was upregulated in patients with ICC ( p < 0.05). Moreover, METTL3 knockdown inhibited the proliferation, migration, and invasion ability of ICC cells ( p < 0.05). Mechanistically, METTL3 mediated m6A modification of S100 calcium-binding protein A4 ( S100A4 ) mRNA and inhibited S100A4 mRNA decay in an m6A-dependent manner ( p < 0.05), thus promoting the proliferation and metastasis of ICC. Conclusions: METTL3 promotes ICC proliferation and metastasis by mediating S100A4 mRNA degradation, suggesting that METTL3 may be a potential target for treating ICC.