Methylation analysis of the DAPK1 gene in imatinib-resistant chronic myeloid leukemia patients

Death-associated protein kinase-1 (DAPK1) is a pro-apoptotic gene that induces cellular apoptosis in response to internal and external apoptotic stimulants. The silencing of DAPK1 can result in uncontrolled cell proliferation, indicating that it may have a role in tumor suppression. DAPK1 activity can be inhibited by the cytosine methylation that occurs in its promoter region. These methylation changes in the promoter region of DAPK1 have been reported in a range of solid and hematological malignancies. In the present study, DAPK1 methylation was investigated in chronic myeloid leukemia patients (n=43) using bisulfite conversion followed by methylation-specific polymerase chain reaction. The present study included a number of patients who were identified to be resistant to the common chemotherapeutic agent imatinib (STI571, Gleevec(®), Glivec(®)), exhibiting at least one mutation in the breakpoint cluster region-Abelson murine leukemia (BCR-ABL) gene. Thus, the patients in the present study were divided into two groups according to their response to imatinib therapy: Non-resistant (n=26) and resistant (n=17) to imatinib. Resistant patients were characterized by the presence of single or multiple mutations of the BCR-ABL gene: i) T315I, ii) M351T, iii) E255K, iv) T315I and M351T or v) T315I, M351T and E255K. The present study identified that: i) The incidence of DAPK1 methylation was significantly higher in the resistant patients compared with the non-resistant patients; ii) the extent of resistance varied between mutation types; and iii) there was no DAPK1 methylation in any of the healthy controls. These findings indicate that DAPK1 methylation may be associated with a signaling pathway for imatinib resistance in chronic myeloid leukemia.