TGF-β and IL-1β as putative combinatorial regulators of extracellular matrix architecture in the tumor microenvironment: A mechanochemical hypothesis

Despite the success of immune checkpoint blockade in selected malignancies, most solid tumors remain refractory to T-cell-mediated immunotherapy. Resistance is attributed to both biochemical and physical mechanisms. One such underappreciated physical contributor is densely aligned collagen networks within the tumor stroma, which can exclude CD8+ cytotoxic T lymphocytes from the tumor core. TGF-β is well established as a driver of myofibroblastic cancer-associated fibroblast (myCAF) differentiation and collagen synthesis, while IL-1β can drive inflammatory CAF (iCAF) programs and modulate matrix metalloproteinase expression. Their combined influence on matrix geometry, as distinct from matrix abundance, has received little systematic attention. Here we propose, as a working hypothesis, that these cytokines may act as a combinatorial mechanochemical code operating through intercellular cooperation, TGF-β would provide the structural signal required for collagen synthesis and myCAF contractility, while IL-1β would provide the proteolytic facilitation required for matrix plasticity. We hypothesize that their spatial co-occurrence generates a matrix phenotype characterized by highly aligned, densely crosslinked fibers with restricted pore size, which could function as a physical barrier to immune infiltration. This model, offered explicitly as a hypothesis, reframes the tumor stroma as a potentially programmed gatekeeper rather than a passive scaffold. If validated, it would suggest that dual blockade of TGF-β and IL-1β may be required to dismantle this barrier, offering a possible mechanistic explanation for the limited efficacy of TGF-β monotherapy in desmoplastic tumors.