Firstly, our CAR designs were structurally identical except for two features (spacer length and co-stimulatory domain), while CAR design in the published studies incorporated not only the CD28 and 4-1BB co-stimulatory domains but also their transmembrane domains, which can influence the stability of CAR-derived surface protein expression, hence anti-cancer potential [26]. This evidence concerns the gene ERVW-1 and cancer.