However, our recent findings with PSCA- and HER2-directed CAR T cells show that while CD28-containing CAR T cells exhibit potent anti-tumor activity in solid tumors, undesirable increases in T cell exhaustion markers, limited persistence, and targeting of tumor cells that express very low levels of antigen may potentiate off-tumor toxicity, compared with 4-1BB-containing CARs (22, 24). Here, ERBB2 is linked to neoplasm.