Abstract
The present study aimed to investigate the association between aberrant DNA methylation of the promoter region of the ephrin type-B receptor 4 (EPHB4) gene and the development of childhood acute lymphoblastic leukemia (ALL). Bisulfite sequencing polymerase chain reaction (BSP) was performed to determine the methylation density of cytosine-guanine pair islands in the promoter region of EPHB4, in bone marrow samples from 40 children with ALL. The mRNA and protein expression levels of EPHB4 were detected using reverse transcription-quantitative polymerase chain reaction and western blot analysis. A total of 10 children with idiopathic thrombocytopenic purpura (ITP) were recruited as controls. The results revealed that the average methylation density of the bone marrow samples from the patients with ALL was significantly higher, compared with the patients with ITP (P=0.046). The relative mRNA expression levels of EPHB4 in the patients with ITP (25.08±4.03) and the patients with ALL without methylation (12.33±2.16) were significantly higher, compared with that observed in the patients with ALL with methylation (6.48±2.73; P<0.01). Pearson analysis revealed a significant negative linear correlation between EPHB4 gene methylation and its expression levels (r=-0.957; P<0.01). Western blot analysis indicated that EPHB4 protein expression levels were low in the methylated ALL samples. An evaluation of the two-year disease-free survival (DFS) of the patients with ALL was performed, which revealed that the patients with unmethylated ALL exhibited a significantly higher two-year DFS rate, as compared with patients with methylated ALL (P=0.036). These results suggest that the methylation of the EPHB4 gene is prevalent in childhood ALL and may result in expressional inactivation, which consequently promotes ALL pathogenesis and is associated with an unfavorable prognosis. Therefore, the EPHB4 gene may function as a potential tumor suppressor in childhood ALL.