CARζ/CPR41BB cells (n = 6 donors) expanded comparably in media containing IL-7 and IL-15 (P = not significant; two-way ANOVA with the Tukey test; Supplementary Fig. S6D) and exhibited proliferative capacity similar to that of second-generation CART (n = 3 donors) when exposed to HER2+/PD-L1+ tumor cells for 72 hours (Supplementary Fig. S6E). This evidence concerns the gene IL15 and neoplasm.