TNFRSF9 and acute myeloid leukemia: A novel NKG2D ectodomain/4-1BB/CD3ζ CAR design co-expressing anti-FLT3/4-1BB/CD3ζ CAR has been proposed to target the relapsed/refractory AML patients with FMS-like tyrosine kinase 3-internal tandem duplication (FLT3-ITD), who have limited treatment options and poor prognosis (62).