MUC1 and lung cancer: The major challenge in CAR-T treatment is the target antigen choice, that needs to be highly specific, expressed and stable [299] such as, for lung cancers, the epidermal growth factor receptor (EGFR) [300], mucin 1, cell surface associated (MUC1) [301], the receptor tyrosine kinase like orphan receptor 1 (ROR1) [302], mesothelin (MSLN) [303].