Overexpression of PML-RARA and AML1-ETO leads to decreased killing by NK cells. (A-B) Left: GFP expression in U937 cells transduced with a lentivirus encoding for GFP together with PML-RARA or AML1-ETO (A-B, black lines, respectively) compared with naïve U937 cells (gray line). Right: The qRT-PCR analysis with specific primers for PML-RARA (A) and AML1-ETO (B). The results were normalized to hypoxanthine guanine phosphoribosyl transferase (HPRT) and the relative copy number of PML-RARA and AML1-ETO was arbitrarily defined as 1. The figure shows 1 representative experiment of 3 performed. (C) ³⁵S-labeled U937 cells expressing PML-RARA, AML1-ETO, or an empty vector were incubated with primary NK cells at the indicated effector to target (E:T) ratios. **P < .01; ***P < .001, Student t test. The upper asterisks are for PML-RARA and the lower asterisks are for AML1-ETO. Error bars represent standard deviation of triplicates. One of 10 representative experiments performed is shown.