METTL16 promotes colorectal cancer progression and CD8+ T cell function through BCAT1-dependent branched-chain amino acid metabolism.

This study aims to investigate whether Methyl-Transferase-Like Protein 16 (METTL16) promotes colorectal cancer (CRC) progression through regulating branched-chain amino acid (BCAA) transaminase 1 (BCAT1)-mediated metabolism to modulate CD8+T cell-mediated anti-tumor immunity. METTL16 levels were measured in clinical CRC samples and cell models using IHC, qPCR and western blot. Functional assays (CCK-8, EdU, wound healing, transwell) were performed to evaluate the impact of METTL16 knockdown on CRC cell behaviors. A co-culture system with CD8+T cells was established to assess immune evasion mechanisms. RIP, MeRIP, and mRNA stability assays were conducted to explore METTL16's regulation of BCAT1 via m6A modification. Metabolomics analysis using LC-MS/MS quantified branched-chain amino acids (BCAAs). In vivo experiments utilized a xenograft mouse model to validate findings. METTL16 was elevated in CRC. Knockdown of METTL16 suppressed malignant phenotype of CRC cell, while enhancing CD8+T cell proliferation and cytotoxic molecule secretion (IFN-γ, IL-2, and GzmB). METTL16 regulated BCAT1 expression through m6A-dependent mRNA stabilization, promoting BCAAs metabolism. Rescue experiments demonstrated that BCAT1 overexpression reversed the regulation of METTL16 knockdown on tumor cell malignancy and CD8+ T cell responses. In vivo, METTL16 depletion inhibited tumor growth, reduced Ki-67 expression, and enhanced CD8+T cell infiltration and effector molecule levels. METTL16 drives CRC progression by promoting BCAT1-mediated BCAAs metabolism and facilitating immune evasion through suppression of CD8+T cell function.