NKG2D Gene Polymorphism Is Associated with Disease Control of Chronic Myeloid Leukemia By Dasatinib

Dasatinib (DA) is a tyrosine kinase inhibitor (TKI), and is approved for the treatment of naïve and relapsed/refractory Philadelphia chromosome positive leukemia. DA is a potent and multi-target TKI, and a part of patients treated with DA are reported to exhibit lymphocytosis and that is caused by a proliferation of NK cells or CD8 T cells. Nowadays, a lot of reports about the stop TKI trials suggested that treatment free remission of the CML after TKI discontinuation was significantly associated with NK cell proliferation in peripheral blood of the patients. So far, little is known about the individual differences in NK cell response among patients treated with Dasatinib.

NKG2D is an activating receptor expressed on NK cells. Recently, functional SNP were identified between LNK1 and HNK1 haplotypes of the NKG2D gene. We analyzed the association between patient's NKG2D polymorphism and achievement of the deep molecular response by Dasatinib. We retrospectively investigated thirty-one patients who were treated with Dasatinib for the first-line treatment of CML at Tokai university school of medicine between 2011 and 2015. Patients with HNK1 haplotype tended to achieve MR^4.5 more frequently (not significant), and these patients accomplished MR^4.5significantly faster than others.

Next, we harvested NK cells from healthy volunteers, and investigated NK cell responses by Dasatinib in vitro. There were differences in the degree of NK cell proliferation capacity among subjects after DA treatment in vitro. We found that NK cells with NKG2D LNK1/LNK1 haplotype exhibited significantly lower proliferation capacity than others in the population. NK cells of higher proliferation capacity exhibited Vav-1 Tyr174 phosphorylation, but they didn't show any differences in cytotoxicity capacity.

In this study, our data suggest that DA may stimulate NK cells with NKG2D HNK1 haplotype more strongly than LNK1 haplotype, and therefore patients with HNK1 haplotype can achieve deep molecular response faster than others. So, personalized medicine according to their NKG2D haplotype may be useful to the treatment of CML, especially when they are considered to discontinue DA in stop TKI trials.