Arsenic trioxide upregulates UL16 binding protein 1 expression in KG1a cells through ataxia telangiectasia mutated and RAD3-related kinase pathway

Objective To observe the effect of arsenic trioxide (ATO) on the expression of NKG2D ligand UL16 binding protein 1(ULBP1) in acute myeloid leukemia KG1a cells, and explore the molecular mechanism for its regulation of ULBP1 expression. Methods KG1a cells were cultured in vitro.Then, the inhibition of KG1a cell proli-feration by different concentrations of ATO was detected by cell counting kit-8(CCK8) assay, and the expression of ULBP1 mRNA and surface protein in KG1a cells were examined by real-time RT-PCR and flow cytometry, respectively.After that, the blocking effects of ataxia telangiectasia mutated and RAD3-related kinase (ATM/ATR) inhibitor caffeine on ATO-upregulated expression of ULBP1 mRNA and surface protein expressions were investigated, and the effects of ATO on the expression of CHK1 and CHK2 proteins and their phosphorylation in KG1a cells were observed by Western blot method. Results Different concentrations (1, 2, 3, 4, 5 μmol/L) of ATO could inhibit the proliferation of KG1a cells, which was concentration dependent, and the half inhibitory (IC50) concentration to KG1a cells was 2.7 μmol/L.The expression of ULBP1 mRNA on KG1a cells were increased when incubated with ATO at concentration 1, 2, 3, 4, 5 μmol/L, compared without ATO group, ULBP1 mRNA expression level relatively increased respectively to (1.86±0.30) times, (3.02±0.71) times, (3.16±0.75) times, (4.80±0.70) times and (3.70±0.89) times, and the differences were statistically significant (all P<0.05). Furthermore, ATO (1, 2, 3, 4 and 5 μmol/L) upregulated ULBP1 protein expression on KG1a cells compared with that in the group without caffeine, and the differences were statistically significant (all P<0.05). After caffeine pretreat KG1a cell 2 h and ATO incubate KG1a cell 24 h, ULBP1 mRNA and protein expression levels were significantly reduced.When caffeine concentration was 8 mmol/L, ULBP1 mRNA expression level relatively reduces from (9.55±0.38) times to (6.36±0.93) times compared with that in the group without caffeine, and the difference was statistically significant (P<0.05). When caffeine concentration was 2, 4 and 8 mmol/L respectively, the expression of ULBP1 protein was reduced from that in the group without caffein treatment (3.50±0.08) times to (2.17±0.07) times, (2.02±0.06) times and (1.75±0.06) times, respectively, and the differences were statistically significant (all P<0.05). The expression of CHK1 and CHK2 proteins decreased with the increase of ATO concentration, while p-CHK1 and p-CHK2 are increased as ATO. Conclusions ATO upregulate the expression of ULBP1 mRNA and protein in KG1a cells, and the ATM/ATR-CHK1/CHK2 pathway may be involved in it. Key words: Arsenic trioxide; KG1a cells; Natural killer cell; UL16 binding protein 1; Ataxia telangiectasia mutated and RAD3-related kinase pathway