ICAM1 and acute myeloid leukemia: To confirm that the impaired killing was due to the strongly reduced expression of ICAM-1 on the surface of STAT3-deficient AML cells, we pre-incubated THP-1 STAT3WT and STAT3KO cells with either IgG control antibody or ICAM-1 blocking antibody and assessed the killing capacity of NK92 cells.