No abstract

The expression of microRNAs (miRNAs) in the serum of B-cell acute lymphoblastic leukemia (B-ALL) patients is abnormal. However, the mechanism is not clear. Recent studies have shown that the methylation state of circulating cell-free DNA (cfDNA) is different between tumor patients and normal people. Therefore, we speculate that abnormal expression of miRNA may be associated with methylation in cfDNA. The aim of this study was to establish a fluorescently labeled B-ALL transplantation animal model, so as to explore the relationship between the serum miRNA expression and the related gene of cfDNA methylation. The expression levels of miRNAs were detected with quantitative real-time PCR (qRT-PCR). The cfDNA methylation levels of related gene were tested by bisulfite sequencing polymerase chain reaction (BSP). The result showed that the expression levels of miR-196b, miR-203, miR-34a-5p, miR-335-3p, miR-34b-5p, miR-615, miR-375-3p and miR-193b-5p in the serum of the model mice were significantly lower than those of the control (P < 0.05). The methylation level of miR-196b promoter in cfDNA of model group was significantly lower than that of the control group (P < 0.05), and there was no significant difference in miR-203 promoter. The methylation levels of miR-196b and miR-203 coding region in cfDNA of model group were significantly higher than those of the control (P < 0.05). The results indicate that CpG island hypermethyation in the miRNA coding region of cfDNA is related to the low expression of miR-196b and miR-203.