독소루비신 내성 백혈병세포에서 방사선 내성에 대한 분자기전

Abstract

This study investigated radioresistance mechanisms in the doxorubicin-resistant acute myelogenous leukemia (AML-2/DX100) cells. AML-2/DX100 cells also showed resistance to radiation. In AML-2/WT cells, radiation increased ratio of Bax/Bcl-2 expression and its translocation to mitochondria, consequently induced the release of cytochrome c from the mitochondria with the subsequent caspase-3 activation. On the contrary, in AML-2/DX100 cells, radiation neither increased Bax/Bcl-2 expression ratio nor its translocation to mitochondria. A specific p38 inhibitor SB203580 increased radioresistance in AML-2/WT cells but little in AML-2/DX100 cells. It inhibited radiation-induced Bax translocation in AML-2/WT cells but not in AML-2/DX100 cells, indicating that p38 MAPK is working after irradiation in AML-2/WT cells but not in AML-2/DX100 cells. Electrophoretic mobility shift assay and Western blot analysis revealed that NF-κB in AML-2/DX100 cells was more activated with degradation of cytosolic IκBα than was that of AML-2/WT cells. cDNA microarray showed that Bfl-1/A1 and granzyme H in AML-2/DX100 were highly up-regulated (6.21-fold) and down-regulated (6.49-fold), respectively as compared with each of AML-2/WT cells, which were confirmed by RT-PCR assay. Taken together, these results indicate that radioresistance mechanisms of AML-2/DX100 cells could be related to alterations in mitochondrial translocation of Bax and Bcl-2, and in expression of pro-apoptotic (granzyme H) and anti-apoptotic (Bfl-1/A1) genes. It has been shown that balance of p38 MAPK and NF-κB signals is a determinant in radiosensitivity of AML-2/WT cells and AML-2/DX100 cells.