Stromal LOX–FAK–β-catenin pathway locks mammary fibroblasts into a tumor-promoting myCAF state

Background Cancer-associated fibroblasts (CAFs) sustain tumor progression, yet the soluble cues that maintain their myofibroblast (myCAF) state are poorly defined. Transforming growth factor beta (TGF-β) is a canonical CAF activator. This study aims to identify TGF-β-induced secreted mediators that reinforce the myCAF phenotype in breast cancer and map the downstream signaling cascade. Methods and Results Secretome profiling of primary patient-derived myCAFs and human mammary fibroblasts (HMF3s) engineered to over-express TGF-β1 revealed 20 extracellular-matrix remodelers shared exclusively by both activated states; lysyl oxidase (LOX) was the top-ranked hit. LOX knockdown abrogated TGF-β–driven α-smooth-muscle actin (α-SMA) induction, collagen-gel contraction and migration in HMF3s, and reduced constitutive α-SMA and β-catenin in myCAFs. Mechanistically, TGF-β upregulated LOX, which activated focal-adhesion kinase (FAK), leading to p38 MAPK- and Akt-mediated Ser9 phosphorylation (inactivation) of GSK3β and consequent β-catenin stabilization. In HCC1806-luciferase orthotopic xenografts, CAFs accelerated tumor growth, whereas LOX-deficient CAFs lost this pro-tumoral effect. Conclusion LOX is a pivotal autocrine effector of TGF-β that locks breast CAFs into a pro-tumoral myCAF state through a LOX/FAK/GSK3β/β-catenin axis. Targeting stromal LOX may disrupt CAF activation and curb breast cancer progression.