Therapy-Induced Senescence Shapes Extracellular Matrix Niches and Fibroblast Function in Head and Neck Squamous Cell Carcinoma

Cellular senescence is a stress-induced state characterised by durable proliferative arrest and extensive transcriptional and secretory reprogramming. In cancer, senescence can suppress early tumour outgrowth, yet persistence of senescent cells and their senescence-associated secretory phenotype (SASP) may drive maladaptive inflammation, immune dysfunction, vascular perturbation and extracellular matrix (ECM) remodelling. Head and neck squamous cell carcinoma (HNSCC) provides a clinically informative context because tumours arise in injury-prone mucosa and standard therapies (radiotherapy and platinum-based chemotherapy) can induce long-lived senescent phenotypes across stromal and vascular compartments. Here, we synthesise the evidence through a signal → matrix → function framework, in which the therapy-induced SASP modules reshape collagen density, alignment, confinement and crosslinking, thereby influencing invasion, immune access, perfusion and post-treatment fibrosis. We emphasise that senescence detection in head and neck tissues is highly context-dependent and readily confounded by inflammageing, chronic mucosal injury and HPV-associated biology, necessitating a cell-type-resolved, spatially anchored, multi-axis definition that integrates growth-arrest context, nuclear/DNA damage response hallmarks and functional outputs. We highlight oral submucous fibrosis (OSF) as a matrix-primed precursor state that exemplifies convergence between chronic injury, fibrosis and senescence-adjacent programmes. Finally, we propose an integrated translational roadmap combining multiplex spatial pathology with quantitative collagen imaging to map therapy-induced senescence-ECM niches and support biomarker-guided testing of senomorphic, senolytic and matrix-normalising strategies in HNSCC.