Reciprocal signaling-metabolic crosstalk between fibroblasts and tumor cells drives cetuximab tolerance in head and neck cancers

BACKGROUND: Resistance to EGFR-targeted therapies, including cetuximab, remains a major barrier to effective treatment of head and neck squamous cell carcinoma (HNSCC). Lipid metabolism reprogramming, TGFβ signaling, and cancer-associated fibroblast (CAF) activation have each been linked to cetuximab resistance, but how these processes mechanistically converge remains unclear. METHODS: We integrated transcriptomic, metabolic, and biochemical assays in HNSCC cell lines, co-culture systems with matched patient-derived non tumoral fibroblasts and CAFs, patient-derived organoids (PDOs), and patient-derived xenografts (PDXs) to characterize tumor-stroma interactions during cetuximab treatment. Fluorescence-based fatty acid (FA) tracing and lipidomic analyses were used to assess FA flux. Functional relevance was tested through genetic and pharmacologic inhibition of TGF-β2 signaling and FA transfer. Clinical relevance was assessed by analyzing TGFB2 expression and plasma TGF-β2 levels in HNSCC patient cohorts. RESULTS: Cetuximab-treated HNSCC cells specifically upregulated and secreted TGF-β2, which induced two coordinated adaptive programs: (i) autocrine metabolic rewiring promoting FA uptake, oxidation, and storage in tumor cells, and (ii) paracrine activation of fibroblasts toward a myofibroblastic, lipid-secreting phenotype. These TGFβ2-activated CAFs supplied FA that sustained oxidative metabolism and preserved EGFR/MAPK signaling in tumor cells, establishing a reciprocal feedback loop that maintained a reversible drug-tolerant state. Disrupting either TGF-β2 signaling or FA transfer abrogated this circuit and restored cetuximab sensitivity in HNSCC cells, spheroids, and PDOs. In PDX models, TGF-β2 inhibition delayed tumor regrowth following cetuximab treatment. Elevated TGFB2 expression and circulating TGF-β2 levels were associated with metabolic reprogramming and poorer clinical outcomes following cetuximab therapy. CONCLUSIONS: Our findings define a tumor-stroma metabolic cooperation axis in which TGFβ2-driven lipid exchange sustains adaptive cetuximab tolerance in HNSCC. Targeting TGFβ2-mediated stromal reprogramming or FA transfer represents a promising strategy to delay or overcome resistance to EGFR-targeted therapies.