TGFB1 and squamous cell carcinoma: However, a recent discovery showed that a subset of TGF‐β‐responsive squamous cell carcinoma initiating cells are refractory to adoptive T cell transfer immunotherapy in a skin cancer model due to expression of CD80, leading to dampening of cytotoxic T cell responses, and upon TGF‐β‐blocking or CD80 ablation, tumor initiating cells become vulnerable 132.