Cancer stem cells possess highly adaptable metabolic characteristics. Nonetheless, the precise mechanisms linking specific metabolic routes to the sustained stemness of gastric cancer cells are not well characterized. The present work identifies the critical contribution of serine hydroxymethyltransferase-2 (SHMT2) and serine to the functional interaction between one-carbon metabolism and lipid metabolism that supports stemness maintenance in gastric cancer. In clinical specimens, SHMT2 was strongly upregulated in both gastric cancer cells (GCs) and gastric cancer stem cells, with its expression levels closely associated with aggressive clinicopathological features and reduced survival in gastric cancer patients. From a mechanistic perspective, silencing SHMT2 lowered intracellular serine availability in the one-carbon pathway. This change subsequently reshaped the makeup and fluidity of membrane phospholipids, resulting in a marked decline in membrane lipid rafts. The consequent phospholipid reorganization prevented γ-secretase from localizing to lipid rafts, thereby blocking CD44 cleavage and the release of CD44-ICD. Consequently, CD44-ICD-mediated transcriptional activation of c-Myc and KLF4 was impaired, leading to the disruption of stemness properties in gastric cancer cells. Taken together, these observations reinforce the concept of metabolic flexibility in cancer stem cells and highlight the SHMT2/serine/lipid rafts signaling axis as a candidate biomarker for gastric cancer diagnosis and prognostic assessment. Moreover, we prepared HA-Exo-siSHMT2 nanoparticles to evaluate targeted therapeutic intervention in GC, thereby introducing a promising new direction for clinical gastric cancer management.
