CD274 and neoplasm: This could be due to several factors including low persistence and expansion of CAR T cells in the recipient, tumor antigen escape (both are factors concurring in B cell malignances), together the insufficient ability of CAR T cells to traffic and infiltrate solid tumors, as well as the immunosuppressive tumor microenvironment (i.e., expression by the tumor of immune checkpoint PD-L1) and physical tumor barriers [132,135].