ERBB2 and neoplasm: After 8 and 24 h coculture, expression of all three exhaustion markers was significantly upregulated in both CD8+ (Figure 5A) and CD4+ (Supplementary Figure S9A) HER2-, but not ctrl-, CAR T cells, consistent with the current view that tumor cell/T cell interactions in the TME induce expression of exhaustion markers in T cells (3).