CD28 and mesothelioma: The advantage of co-expressing CAR and PD1-CD28 switch receptor is that the CAR T cells’ anti-tumor potency can be further improved by offsetting the inhibitory signals of PD1/PD-L1/2 and at the same time, providing T cells with additional CD28 costimulatory signal, which was supported by a recent study that tested T cells transferred with CARs and switch receptors in different clinically relevant mouse tumor models for mesothelioma and prostate cancer by targeting mesothelin or prostate stem cell antigen (PSCA).