In the tumor microenvironment, potential stimuli that activate fibroblasts include bone morphogenetic protein (BMP), interleukin-1, interleukin-6, platelet-derived growth factor (PDGF), sonic hedgehog (SHH), reactive oxygen species (ROS), transforming growth factor-β (TGF-β), as well as TNF. The gene discussed is TGFB1; the disease is neoplasm.