In recent years, co-stimulation receptors derived from 4-1BB or CD28, etc., were incorporated to create second-generation CARs, because the first-generation CAR-T cells engineered with a targeting domain and CD3ζ failed to elicit durable anti-tumor responses.20, 21, 22 It is now clear that incorporation of co-stimulatory signals in CARs is essential to maximize T cell expansion, persistence, and anti-tumor activity. The gene discussed is CD247; the disease is neoplasm.