PDCD1 and neoplasm: In line with the encouraging results from studies combining TCR-modified T cells and CSR,111,113,114 PD-1–CD28 can improve the therapeutic effects of anti-mesothelin CARs and anti-PSCA CARs in tumour xenograft models.115 The improved therapeutic effect was attributed to an increase in the number of infiltrating CAR T cells, a decrease in susceptibility of the cells to tumour-induced hypofunction, and an attenuation of inhibitory receptor expression.