On the other hand, in chimeric antigen receptor (CAR) T cell treatment for cancer, integration of the lentiviral CAR cassette into specific cancer genes can potentiate CAR-T cell therapeutic effect by promoting the persistence of CAR T cells (by insertional activation of BACH2) (42) or driving proliferation of specific clones (by insertional disruption of TET2 or insertional activation of VAV1) (56, 57). The gene discussed is VAV1; the disease is cancer.