CSPG4 and breast carcinoma: As observed for CSPG4 CAR T cells, B7-H3 CAR T cells did not show ‘off-tumor’ effect, as demonstrated by the lack of killing when cocultured with the B7-H3 negative Jurkat cell line or with the breast cancer cell line MDA-MB-231 genetically modified to knockout B7-H3 expression (MDA-MB-231 B7-H3-/-) (Fig. 2F, Supplementary Fig. 1E-I).