Colony-stimulating factor-2 triggers NNMT-dependent myofibroblast activation in head and neck cancer

Myofibroblastic cancer-associated fibroblasts (myoCAFs) represent a crucial stromal cell subpopulation associated with tumor growth, relapse, and metastasis. In this study, we identify a noncanonical mechanism through which head and neck cancer cells regulate myoCAF activation. Co-culture with tumor organoids promoted the expression of cytokine interaction-related genes and myoCAF phenotypic markers in paracancerous fibroblasts (PFs). Cytokine and tissue array analyses revealed that upregulation of colony-stimulating factor-2 (CSF2) in tumor cells correlated with overexpression of nicotinamide N-methyltransferase (NNMT) in CAFs. Notably, CSF2 treatment enhanced myoCAF properties in a NNMT-dependent manner, while NNMT overexpression remained largely unaffected by transforming growth factor-β (TGF-β). In both assembled organoid and xenograft models, tumor growth was reduced when either CSF2 in cancer cells or CSF2 receptor subunit CSF2RA in CAFs was knocked down. Mechanistically, CSF2 induced FOS phosphorylation at Ser32, promoting nuclear translocation of phosphorylated FOS (p-FOS) to regulate NNMT transcription. In drug screening assays, CSF2 blockade partially overcame resistance to TGF-β inhibition. These findings establish the CSF2/FOS/NNMT axis as a TGF-β-independent pathway driving myoCAF activation.