TGFB1 and neoplasm: The role of TGF-β1 strongly depends on the stage of cSCC: while in the early stage, it acts as a tumor suppressor, it contributes to tumor progression in later cSCC stages, by enhancing tumor heterogeneity and treatment resistance via cancer stem cell pathways, increasing invasiveness by promoting epithelial to mesenchymal transition, and suppressing anti-tumor immunity.