CTLA4 and neoplasm: Moreover, as a vector, oncolytic viruses can carry cofactors, such as granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin 12 (IL-12), or some immune checkpoint inhibitor antibodies such as programmed cell death protein 1 (PD-1) and cytotoxic T-lymphocyte associated protein 4 (CTLA4) [3,19,20,21,22,23,24,25,26], and deliver them to tumor lesions for tumor therapy.