The BRAF V600E/MEK/ERK/METTL3 positive feedback loop regulates autophagy and promotes stemness and invasiveness in glioblastoma via m6A modification

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Abstract Background Epithelioid glioblastoma (GBM) is characterized by its highly aggressive behavior and the presence of the BRAF V600E mutation. However, the impact and underlying mechanisms of the BRAF V600E mutation on GBM stemness and invasiveness are unknown. Dysregulation of N6-methyladenosine (m6A) modification is closely associated with the progression of various cancers. The role of m6A modification in BRAF V600E-mutant GBM has not been defined. Methods Functional assays were performed to evaluate the impact of BRAF V600E on stemness phenotypes of glioma stem-like cells (GSCs) and invasive phenotypes of GBM cells in vitro and in vivo. Mechanistic investigations involved m6A quantification, qPCR, western blotting, co-immunoprecipitation, MeRIP-seq, luciferase reporter assays, and transmission electron microscopy to elucidate the mechanism by which BRAF V600E regulates stemness and invasiveness. These findings were further supported by evidence from public GBM patient databases and tumor samples. Results We found that BRAF V600E significantly upregulated METTL3 expression via ERK signaling in GSCs and GBM cells, thereby promoting stemness and invasiveness. METTL3 established a positive feedback loop with BRAF V600E to facilitate m6A modification enrichment, thereby inducing autophagy. The BRAF V600E-driving stemness and invasiveness were autophagy-dependent. In vivo experiments showed that BRAF V600E-expressing GBM was responsive to both the METTL3 inhibitor STM2457 and the autophagy inhibitor HCQ. Conclusions This study reveals that the BRAF V600E/MEK/ERK/METTL3 positive feedback loop promotes autophagy, driving the stemness of GSCs and the invasiveness of GBM cells via m6A modification in vitro and in vivo. Our results suggest that METTL3 and autophagy are promising therapeutic targets in BRAF V600E-mutant GBM.

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