CA9 and neoplasm: In an effort to counteract the negative effects of the tumor microenvironment on CAR T cell function, we designed and tested a self-inactivating (SIN) bicistronic lentiviral vector that could deliver a new type of double immunotherapy based on enabling targeted anti-carbonic anhydrase (CAIX) CAR T cells to secrete anti-PD-L1 antibodies at the tumor site to block T cell exhaustion.