Changes in the Expression of DNMTs Before and After Treatment with Methotrexate (MTX)/Mercaptopurine (6-MP) in B-Cell ALL Children

Background: DNA methylation is catalyzed by DNA methyltransferases (DNMTs) which are encoded by DNMT1, DNMT3A, and DNMT3B. DNMTs play a major role in the abnormal methylation of tumor suppressors and cancer-related genes. Herein, this study explored the expression profile of DNMTs in pediatric patients with B-cell acute lymphoblastic leukemia (ALL), before and after methotrexate (MTX)/mercaptopurine (6-MP) treatment. Materials and Methods: This before-after prospective study included 30 matched children in sex and age (20 children with B-cell ALL and 10 healthy children used as a control or calibrator group). The expression profile of DNMTs was assessed at two-time points; at the diagnosis time and after MTX/6-MP treatment in the consolidation-maintenance phase of therapy. Notable, all pediatric patients included in this study continued the therapy without adverse events, except two children who were excluded from the study. Results: The average age of the patient group was 7.1 ± 1.3 years (in the range of 4-9 years), and the average age of the control group was 8.3 ± 1.7 years (6-10 years). The expression profile of DNMTs in B-cell ALL children was obtained completely different from that in the healthy group. After MTX/6-MP treatment of B-cell ALL children, the expression levels of DNMT1 and 3A were increased (p <0.01 & 0.04, respectively), and the expression level of DNMT3B was decreased (p <0.01), significantly. Conclusions: In ALL, the expression profile of DNMTs would be changed whereby contribute to abnormal growth and maturation capacity of leukemic stem cells and MTX/6-MP treatment could reverse this profile from a cancerous phenotype to the normal one.