Cancer-associated fibroblasts (CAFs) are believed to contribute to this CAR T cell inactivation by releasing immunosuppressive cytokines such as IL-10 and TGF-β (19), secreting tumor-stimulating growth factors including fibroblast growth factors, vascular endothelial growth factors, and hepatocyte growth factor (19–22), and depositing extracellular matrix components such as collagen and fibronectin that can create an impermeable barrier to entry of immune cells and therapeutic agents, and also facilitate cancer metastasis (19, 21, 23). The gene discussed is TGFB1; the disease is cancer.