A recent study reported that treatment-free remission (TFR) of chronic myeloid 
leukemia (CML) after dasatinib (Das) treatment was significantly associated with 
natural killer (NK) cell proliferation in the peripheral blood. However, 
biomarkers to predict lymphocytosis or successful TFR are not well 
characterized. In order to clarify individual differences in NK cell responses 
among patients treated with Das, we retrospectively analyzed the association 
between polymorphisms in the natural killer group 2D receptor [NKG2D; also known 
as killer cell lectin like receptor K1 (KLRK1)] gene and clinical outcomes in 31 
patients treated with Das as first-line treatment for CML. Patients with the 
NKG2D HNK1/HNK1 (high-cytotoxic activity-related allele on NKG2D hb-1) haplotype 
achieved MR4.5 more quickly than those with other haplotypes [hazard ratio (HR) 
4.39; 95% confidence interval (CI) 2.75-118.6; P = 0.004]. In addition, NK cells 
with the NKG2D HNK1 allele exhibited enhanced phosphorylation of vav guanine 
nucleotide exchange factor 1 (VAV1) at Tyr174. These data suggest that NKG2D 
gene polymorphisms may represent candidate biomarkers for the prediction of TFR 
following Das treatment.