PDCD1 and neoplasm: IL-33 has never been used in the context of genetically engineered tumor-specific T cells; however, its simultaneous expression in vivo was required to drive Tcf1 suppression, allowing OT1 cells to exit the memory-like/stemness-associated state and differentiate to polyfunctional PD-1+TOXneg effector cells with direct antitumor potential.