OBJECTIVETo explore the expression and promoter CpG island methylation status of miR-34b in leukemia cell lines and their clinical significance.

METHODSA total of 10 cases of non-hematologic diseases were selected as control group, and the bone marrow cells of control group and HL-60, K562 cells were selected; the relative expression of miR-34b was detected in bone marrow cells, HL-60 and K562 cell lines by fluorescence quantitative PCR, and the MiR-34b methylation status was detected by methylation-specific PCR, the HL-60 and K562 cell lines were treated with decitabine, and the expression levels and methylation status of miR-34b in the 2 cell lines were detected by the same method. Has-miR-34b was transfected into K562 cells, which were divided into non-transfection group, negative control group and Has-miR-34b transfection group; if the transfection was successful, the cell proliferation should be recorded at different time points of culture, and the proliferation inhibition rate should be calculated.

RESULTSThe relative expression level of miR-34b in the control group was (5.23 ± 0.75), in HL-60 was (0.05 ± 0.01) and in K562 was (0.04 ± 0.01). The difference between 3 groups was statistically significant (F = 44.812, P < 0.01). The promoter regions of CpG island in HL-60 and K562 cell lines were methylated, while the bone marrow cells were not methylated in 10 cases of non hematologic diseases children.Through miR-34b expression levels of HL-60 and K562 cell lines significantly increased by decitabine treatment (P < 0.05), and the methylation of leukemia cell line promoter region CpG island was found before and after decitabine treatment, but after administration of decitabine the methylation significantly decreased, suggesting that decitabine has an inhibitory effect on methylation of promoter region CpG island. After being cultured for 48, 72, 96 and 120 hrs, the cell proliferation in Has-miR-34b transfection group reached to 24.8%, 46.7%, 33.6% and 4.7%, repectively, and significantly lower than that in non transfection group (P < 0.05).

CONCLUSIONCpG island methylation of miR-34b promoter region in leukemia cell lines can decrease the expression levels of miR-34b, which is also the reason why miR-34b can reduce the inhibition of cell proliferation, thus miR-34b might be a tumor suppressor gene involved in the regulation of leukemia.