Superior survival rates were noted in mice treated with CAR1‐, CAR2 (CD8 TMD‐ FcεRIγ SD)‐, CAR3 (CD8 TMD‐OX40 CD‐ CD3ζ SD)‐ and CAR4‐NK cells over those treated with CAR5 (CD28 TMD‐ FcεRIγ SD)‐, CAR6 (CD8 TMD‐4‐1BB CD‐CD3ζ 1‐ITAM SD)‐ and CAR7 (CD8 TMD‐OX40 CD‐CD3ζ 1‐ITAM SD)‐NK cells, with CAR5‐NK cells showing the weakest anti‐tumour activity. This evidence concerns the gene CD28 and neoplasm.