CRISPR mediated triple knockout of TCR, HLA-I and Fas CAR T cells showed elevated levels of T cell expansion coupled with increased degranulation, cytokine production and potent antitumor activity in vitro, while Fas deficiency contributed to prolonged survival of CAR T cells in leukemia murine model, indicative of an attenuation in AICD. The gene discussed is FAS; the disease is leukemia.