CD274 and neoplasm: Incubation of AAV vectors with bispecific antibodies binding to 2E3 and fibroblast activation protein (FAP) or to programmed death-ligand 1 (PD-L1), respectively, retargeted the new AAV2 capsid to FAP, which is upregulated on activated fibroblasts within the tumor stroma and to PD-L1, which is strongly upregulated on the surface of tumor cells in many cancers.