ENO2 sustains cancer stemness and metastatic competence through a phosphoenolpyruvate-dependent metabolic axis in triple-negative breast cancer.

Enolase 2 (ENO2) is a neuron-specific glycolytic enzyme whose expression is elevated in aggressive breast cancers, yet its enzymatic and biological contributions to triple-negative breast cancer (TNBC) progression remain incompletely defined. Here, we demonstrate that ENO2 sustains cancer stem cell (CSC) properties and metastatic competence through a phosphoenolpyruvate (PEP)-dependent metabolic axis. Elevated ENO2 expression correlated with advanced tumor grade and poor clinical outcomes in TNBC cohorts, underscoring its clinical relevance. Genetic depletion of ENO2 impaired aerobic glycolysis and oxidative phosphorylation, reduced migration, invasion, and CSC frequency, and suppressed tumor growth and pulmonary metastasis in orthotopic models. Mechanistically, exogenous PEP or pyruvate restored CSC-associated traits and invasiveness in ENO2-deficient cells, supporting the functional involvement of ENO2-derived metabolites in CSC maintenance. Reconstitution with wild-type ENO2, but not a catalytically impaired mutant, restored CSC properties, invasiveness, and metastatic colonization, establishing that ENO2 catalytic activity is required for these malignant traits. Further analysis revealed that PKM2 perturbation preferentially attenuated PEP-mediated rescue while largely sparing pyruvate-mediated rescue, supporting a functional PEP-PKM2-pyruvate axis in CSC regulation. Consistently, PKM2 depletion partially blunted ENO2-mediated rescue; however, residual rescue despite PKM2 perturbation suggested additional PKM2-independent PEP-responsive mechanisms. Importantly, pharmacological inhibition of enolase with POMHEX phenocopied genetic ENO2 loss and suppressed CSC maintenance in vitro and tumor growth in vivo. Taken together, these findings identify the ENO2-driven PEP-dependent metabolic axis as a mechanistic link between metabolic reprogramming, cancer stemness, and metastasis, revealing a therapeutically actionable metabolic vulnerability in TNBC.