Balance of NF-kappaB and p38 MAPK is a determinant of radiosensitivity of the AML-2 and its doxorubicin-resistant cell lines.
This study investigated radioresistance mechanisms in the doxorubicin-resistant acute myelogenous leukemia (AML)-2/DX100. AML-2/DX100 also showed resistance to radiation. AML-2/DX100 characterized by down-regulated catalase expression was supersensitive to exogenous hydrogen peroxide whereas they increased defense mechanisms against endogenous reactive oxygen species (ROS) as compared with AML-2/WT. In AML-2/WT, radiation increased Bax expression and its translocation to mitochondria but had little effect on translocation of Bcl-2 and consequently induced the release of cytochrome c from the mitochondria with the subsequent caspase-3 activation. On the contrary, in AML-2/DX100, radiation neither increased Bax expression nor its translocation to mitochondria while it increased Bcl-2 translocation to mitochondria. A specific p38 MAPK inhibitor SB203580 increased radioresistance in AML-2/WT but little in AML-2/DX100. It inhibited radiation-induced Bax translocation in AML-2/WT but not in AML-2/DX100, indicating that p38 MAPK is working after irradiation in AML-2/WT but not in AML-2/DX100. Electrophoretic mobility shift assay and Western blot analysis revealed that NF-kappaB in AML-2/DX100 was more activated with degradation of cytosolic IkappaBalpha than was that of AML-2/WT. 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, which were confirmed by RT-PCR assay. Taken together, these results indicate that radioresistance mechanisms of AML-2/DX100 could be related to alterations in ROS-scavenging activity, 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-kappaB signals is a determinant in radiosensitivity of AML-2/WT and AML-2/DX100.
Choi
Cheol-Hee
CH
Research Center for Resistant Cells, Chosun University, Gwangju 501-759, Republic of Korea.
Xu
Haidong
H
Bark
Hyun
H
Lee
Tae-Bum
TB
Yun
Jisoo
J
Kang
Sung-In
SI
Oh
Yoon-Kyeong
YK
D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D045744:Cell Line, Tumor; D004317:Doxorubicin / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm / Q000528:radiation effects*; D020869:Gene Expression Profiling; D053804:Granzymes; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D015470:Leukemia, Myeloid, Acute / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D016877:Oxidants / Q000494:pharmacology; D021381:Protein Transport; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011836:Radiation Tolerance; D017382:Reactive Oxygen Species / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014965:X-Rays; D051028:bcl-2-Associated X Protein / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
D000903:Antibiotics, Antineoplastic; C494826:BAX protein, human; D016328:NF-kappa B; D016877:Oxidants; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D051028:bcl-2-Associated X Protein; D004317:Doxorubicin; D006861:Hydrogen Peroxide; D048051:p38 Mitogen-Activated Protein Kinases; D053804:Granzymes