Expression and clinical significance of miR-34b in children with acute leukemia

Abstract

Objective To research the expression, methylated regulation and clinical significances of miR-34b in chidren with acute leukemia(AL). Methods The methylation status of miR-34b promoter CpG islands were detected with methylation-specific polymerase chain reaction (MSP) in patients with AL.Then the expression of miR-34b was compared, which was detected by Taqman real-time fluorescence quantitative polymerase chain reaction (qRT-PCR), between the AL patients and normal group, in order to analyze their relationship with the clinical indicators. Results In 8 leukemia cell lines (U937, HL-60, MV4-11, M2R, K562, Raji, CCRF, DAMI) showed methylation, the po-sitive rate of the methyl was 100%.Thirty-one acute lymphocytic leukemia(ALL) pediatric patients were newly diagnosed, and 24 cases showed methylation, the methylation positive rate 77.42% (24/31). Nineteen acute myeloid leukemia(AML) patients were newly diagnosed, and 8 cases showed methylation, the methylation positive rate was 42.11%(8/19 cases). There was no methylation in the 23 cases of normal children.The relative expression levels of miR-34b in the normal group, the group of leukemia cell lines, the group of ALL pediatric patients with newly diagnosed, the AML group and the group with mixed lineage leukemia gene rearrangement MLL+ were 5.22±1.15, 0.03±0.03, 1.65±0.69, 0.18±0.06, 0.64±0.34, respectively.The findings indicated that there were significant differences in the relative expression levels of miR-34b between the normal group and the group of leukemia cell lines, the ALL group, the AML group, and the MLL+ group.The relative expression and methylated level of miR-34b had no statistically diffe-rence in gender, age at diagnosis, WBC count, chromosome, fusion gene, MLL gene rearrangement, and the minimal resi-dual disease(LDH) levels in newly diagnosed AML patients(all P>0.05). And the relative expression and methylated level of miR-34b had no statistically difference in gender, age at diagnosis, WBC count, immunophenotype, chromosome, fusion gene, MLL gene rearrangement, TEL/AML1 gene, risk stratification, the minimal residual disease (MRD) in thirty-three days and the LDH levels in newly diagnosed ALL patients(all P>0.05). But as for the response to prednisone experiment, there was a significant difference between the sensitive group and the non sensitive group(P<0.05). Conclusions The expression level of miR-34b in AL was significantly lower and it was regulated by methylation mechanism, which implies that miR-34b may play a role of a tumor suppressor gene in the pathogenesis of leukemia.MiR-34b may affect the early treatment response of ALL patients, and it may be an indicator of risk stratification and poor prognosis in pediatric ALL. Key words: Leukemia, acute; MiR-34b; DNA methylation; Expression; Clinical significance; Child