Aberrant Methylation of APAF-1 Gene in Acute Myeloid Leukemia Patients

Background: Acute myeloid leukemia (AML) is a heterogeneous clonal disorder characterized by immature myeloid cell proliferation and bone marrow failure. Various genetic and epigenetic factors have been found to be influential in such patients. Methylation silencing of APAF-1, a putative tumor suppressor gene (TSG), has been found in several human malignancies. In this study, we explored the association of APAF-1 methylation status with AML patients. Materials and Methods: We studied the methylation status of APAF-1 gene in 101 AML patients and 50 healthy subjects as controls. Genomic DNA was extracted from leukocytes in peripheral blood or bone marrow and the methylation status of APAF-1 gene promoter was detectedusing methylation-specific PCR (MSP) method with specific methylated and unmethylated primers. Gene expression was analyzed using real time RT-PCR. Results: The prevalence of methylated (MM) and hemi-methylated (MU) CpG dinucleotides within the APAF-1 gene promoter of AML patients was 12 (11.9%) and 45 (44.6%), respectively, while no methylation was detected in the control samples (p < 0.001). Our results showed a higher frequency of methylated APAF1 in FLT3-ITD mutated cases (p=0.04). APAF1 mRNA expression was significantly lower in methylated cases compared with normal cases. Conclusion: The present study indicated the increased frequency of hypermethylation of APAF-1 gene promoter in AML patients. APAF-1 aberrant CpG island methylation was associated with transcriptional downregulation in AML patients. Therefore, promoter methylation of APAF-1 gene could be considered as an epigenetic factor that contributes to the development of AML.