2005 Fiscal Year Final Research Report Summary
Role of BMI-1 in leukemia
| Project/Area Number |
16590931
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Hematology
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| Research Institution | Aichi Cancer Center (2005)
Nagoya University (2004) |
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Principal Investigator |
YAMAMOTO Kauzhito Aichi Cancer Center, Molecular Medicine, Researcher, 遺伝子医療研究部, 研究員 (60250247)
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| Co-Investigator(Kenkyū-buntansha) |
NAOE Tomoki Nagoya Univ Grad Scl Med, Hematol and Med Oncol, Professor, 大学院・医学系研究科, 教授 (50217634)
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| Project Period (FY) |
2004 – 2005
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| Keywords | BMI-1 / Differentiation / Proliferation / Apoptosis / Mouse model |
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| Research Abstract |
Recent studies have suggested that one of the polycomb group genes, BMI-1,has an important role in the maintenance of normal and leukemia stem cells by repressing the INK4a/ARF locus. Firstly, we quantitatively examined the BMI-1 expression level in acute myeloid leukemia (AML) cells. The BMI-1 expression level of AML samples was significantly higher than that of normal bone marrow controls. The CD34-positive fraction of cord blood showed a transcript about 8 times as high as CD34-negative fraction, whereas normal peripheral mononuclear cells showed a moderate transcript, lower than a cell line expressing a high BMI-1 level. According to FAB classification, BMI-1 transcript of M0-type was about 3 times higher than that of other types of AMLs. The INK4a-ARF transcript had a tendency of inverse proportion to that of BMI-1. This suggested that BMI-1 in part downregulates the transcript of INK4a-ARF locus in leukemia. In an M0 patient with a high transcript of BMI-1,the level fell promptly
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and maintained a low value after achieving complete remission. Secondly, to investigate the role of BMI-1 in proliferation, differentiation and apoptosis of leukemias, 32D cells were infected with MIG-BMI-1-IRES-EGFP vector or MIG vector, and the GFP positive rates of BMI-1 overexpressing 32D cells gradually increased under IL-3 diminished conditions, and the consecutive MTT assays using cells sorted by GFP positivity confirmed this finding, suggesting that BMI-1 could confer growth advantages on 32D cells under IL-3 diminished conditions. Exposure of the GFP sorted 32D cells to G-CSF revealed that BMI-1 overexpression suppressed the granulocytic differentiation of 32D cells by G-CSF. The expressions of CD11b and Gr-1 were both suppressed by the overexpression of BMI-1,and real-time PCR analyses indicated that the expression levels of MPO was remarkably suppressed, while those of C/EBPα were not significantly changed. These results revealed that BMI-1 delayed granulocytic differentiation and ameliorated the growth of 32D cells under IL-3 diminished conditions. We also established a stroma-dependent AML (M0) cell line which overexpresses BMI-1. This line is a useful cell line to study biology of leukemia cells overexpressing BMI-1. Less
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