CD28 and neoplasm: Superior anti-tumor activity of pCAR H/T cells was observed in mice with an established MDA-MB-468 xenograft (Figures 5H–5L) or a HER2-overexpressing derivative (Figures S4B–S4D), when compared with 2G (CD28 [Figures 5I, 5K, and S4C]; 41BB [Figure 5L]) or 3G controls (Figure 5L).