Methyltransferase-like 3 facilitates lung cancer progression by accelerating m6A methylation-mediated primary miR-663 processing and impeding SOCS6 expression.

OBJECTIVE: Lung cancer (LC) remains a threatening health issue worldwide. Methyltransferase-like protein 3 (METTL3) is imperative in carcinogenesis via m6A modification of microRNAs (miRNAs). This study estimated the effect of METTL3 in LC by regulating m6A methylation-mediated pri-miR-663 processing. METHODS: miR-663 expression in 4 LC cell lines and normal HBE cells was determined using RT-qPCR. A549 and PC9 LC cells selected for in vitro studies were transfected with miR-663 mimics or inhibitor. Cell viability, migration, invasion, proliferation, and apoptosis were detected by CCK-8, Transwell, EdU, and flow cytometry assays. The downstream target genes and binding sites of miR-663 were predicted via Starbase database and validated by dual-luciferase assay. LC cells were delivered with oe-METTL3/sh-METTL3. Crosslinking between METTL3 and DGCR8 was verified by co-immunoprecipitation. Levels of m6A, miR-663, and pri-miR-663 were measured by m6A dot blot assay and RT-qPCR. m6A modification of pri-miR-663 was verified by Me-RIP assay. Finally, the effects of METTL3 in vivo were ascertained by tumor xenograft in nude mice. RESULTS: miR-663 was upregulated in LC cells, and miR-663 overexpression promoted cell proliferation, migration, invasion, and inhibited apoptosis, but miR-663 knockdown exerted the opposite effects. miR-663 repressed SOCS6 expression. SOCS6 overexpression annulled the promotion of miR-663 on LC cell growth. METTL3 bound to DGCR8, and METTL3 silencing elevated the levels of pri-miR-663 and m6A methylation-modified pri-miR-663, and suppressed miR-663 maturation and miR-663 expression. METTL3 facilitated tumor growth in mice through the miR-663/SOCS6 axis. CONCLUSION: METTL3 promotes LC progression by accelerating m6A methylation-mediated pri-miR-663 processing and repressing SOCS6.