Objective To investigate the expression of TET2 mRNA and protein in the bone marrow mononuclear cells(BMMNC) of patients with myelodysplastic syndrome(MDS) and its clinical significance. Methods The expression of TET2 mRNA and protein in bone marrow mononuclear cells(BMMNC) of 32 patients with MDS and 20 healthy donors was examined by qPCR and Western blot. Results The expression of TET2 mRNA in BMMNC was down-regulated in MDS patients compared with the donor group [(0.41±0.28)%vs.(1.07±0.56)%](P<0.001).Compared with lower expression group(TET2<0.4)[(6.53±6.17)%],patients with higher expression of TET2(≥0.4) presented significantly lower proportion of bone marrow blasts[(1.21±1.56)%](P<0.05).The expression of TET2 mRNA in BMMNC of MDS patients was inversely correlated with malignant clone burden(r=-0.398,P<0.05) and IPSS(r=-0.412, P<0.05).The expression of TET2 protein was down-regulated in MDS patients compared with that in the donor group. Conclusions The mRNA and protein expression of TET2 in BMMNC of MDS patients is decreased,which might be useful as an important parameter for the evaluation of MDS clone burden. Objective To investigate the expression of TET2 mRNA and protein in the bone marrow mononuclear cells (BMMNC) of patients with myelodysplastic syndrome (MDS) and its clinical significance. Methods The expression of TET2 mRNA and protein in bone marrow mononuclear cells (BMMNC) of 32 Results The expression of TET2 mRNA in BMMNC was down-regulated in MDS patients compared with the donor group [(0.41 ± 0.28)% vs (1.07 ± 0.56)% (P <0.001) .Compared with lower expression group (TET2 <0.4) [(6.53 ± 6.17)%], patients with higher expression of TET2 (≥0.4) presented significantly lower proportion of bone marrow blasts [(1.21 ± 1.56) %] (P <0.05). The expression of TET2 mRNA in BMMNC of MDS patients was inversely correlated with malignant clone burden (r = -0.398, P <0.05) and IPSS of TET2 protein was down-regulated in MDS patients compared with that in the donor group. Conclusions The mRNA and protein expre ssion of TET2 in BMMNC of MDS patients is decreased, which might be useful as an important parameter for the evaluation of MDS clone burden.