MTHFR functions as a metabolic checkpoint in NSCLC through SLC25A26-mediated SHMT2 inhibition.

The progression of non-small cell lung cancer (NSCLC) is driven by metabolic plasticity and evasion of apoptotic surveillance, mechanisms that remain incompletely understood. Here, through integrated transcriptomic-metabolomic profiling, molecular interaction mapping, and functional validation, we unveiled a dual regulatory mechanism governed by the MTHFR/SLC25A26 axis that suppresses NSCLC. Clinical cohort analyses revealed concurrent downregulation of MTHFR and SLC25A26 in NSCLC tissues, which strongly correlated with poor prognosis. Mechanistically, MTHFR directly binds and stabilizes SLC25A26, whereas SLC25A26 accelerates SHMT2 degradation via the ubiquitin-proteasome pathway and concurrently suppresses AKT-driven MYB transcriptional activation. This coordinated disruption of serine/one-carbon metabolism and oncogenic signaling significantly inhibited tumor growth in patient-derived xenograft models. Crucially, we identified SLC25A26 as a mitochondrial transporter-ubiquitin adapter hybrid that destabilizes SHMT2 through ubiquitination, whereas its interaction with MTHFR prevents metabolic dysregulation induced by the C677T mutation. Our findings establish the MTHFR/SLC25A26 axis as a master regulator of metabolic-transcriptional crosstalk, providing a therapeutic framework for targeting enzyme stability and kinase signaling in NSCLC treatment. The MTHFR/SLC25A26 axis suppresses NSCLC progression through catalytic activity-dependent stabilization of SLC25A26 by MTHFR, where SLC25A26 functions as a ubiquitin adapter to degrade SHMT2 while concurrently repressing AKT-MYB-driven SHMT2 transcription; clinical downregulation of this axis predicts poor prognosis, and MTHFR overexpression inhibits tumor growth in vivo.