PTK7 and lung cancer: In view of the in vitro preferential target-specific recognition and cytotoxicity of PTK7-CAR2 T cells as well as the fact that the antibody from which the scFv used by PTK7-CAR2 is derived has been tested in the clinical trial (12), we evaluated the in vivo antitumor activity of these candidate CAR T cells in the xenograft tumor models established from two lung cancer cell lines with distinct antigen expression: H520 and H69 cells with high or moderate level of PTK7 expression respectively as determined by flow cytometry and IHC staining of cell line-derived xenografts (Figures 2 and S4).