2000 Fiscal Year Final Research Report Summary
Molecular mechanism of multi-step leukemogenesis in adult T-cell leukemia
| Project/Area Number |
11671006
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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 | KYOTO UNIVERSITY |
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Principal Investigator |
MATSUOKA Masao Kyoto University, Institute for Virus Research, M.D., Ph.D, ウイルス研究所, 教授 (10244138)
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| Project Period (FY) |
1999 – 2000
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| Keywords | ATL / HTLV-I / retrovirus / immunodeficiency / DNA methylation / naive T-cell / leukemogenesis |
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| Research Abstract |
1)Progressive DNA methylation in the promoter region of CDKNZA(p16)gene in adult T-cell luekemia cells : In this study we examined the methylation ststus of the CDKNZA gene in patients with different forms of adult T-cell leukemia(ATL)using Southem blot analysis, methylation-specific PCR(MSPCR), and nucleotide sequencing. We found that the CDKNZA gene was more frequently methylated in fresh tumor cells isolated from patients with acute ATL(47%)or lymphoma-type ATL(73%)than in those with less malignant chronic(17%)and smoldering ATL(17%). In addition, deletions of the CDKNZA gene were found in 24% of acute ATL patients ; thus abnormalities of the CDKNZA gene totaled 71% in acute ATL patients. In contrast, no CDKNZA gene methylation was found in asymptomatic carriers or uninfected individuals. Methylation of the p15 gene was not found in any samples from 36 ATL patients. Direct sequencing of the CDKNZA gene after sodium bisulfite treatment of genomic DNA revealed that the methylation of
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CpG sites had occurred in 24 of 32 ATL cases(75%)including chronic and smoldering ATL, even when MSPCR and the Southem blot had failed to detect CDKNZA gene methylation. Among fresh ATL samples with methylation, methylation was detected in the promoter region and exon in 17 out of 24 casee, and methylation in the exon wihout upstream was detected in 7 cases out of 24 cases. In one case' the pattern of methylation proved to be different between peripheral blood cells and lymph node cells, suggesting the presence of multiple subclones with regard to methyhlation patterns despite the same HTLV-I integration site. Quantitative PCR showed a marked decrease in CDKNZA mRNA expression in the cells with a methylated CDKNZA gene, especially if promoter region was methylated. These findings suggest that CpG methylation decreases CDKNZA expression and represents a critical factor in the disease progression of ATL.
2)Impaired prduction of naive T-lymphocytes in human T-cell leukemia virus type I infected individuals : its implications in the immunodeficient state : Opportunustic infections frequently occur in patients with adult T-cell leukemia(ATL), and human T-cell leukemia virus type I(HTLV-1)carriers. However, the underlying immunological and virological mechanisms of such infections remain unknown. To clarify the mechanism of immunodeficiency observed in HTLV-I infected individuals, we analyzed the T-cell subsets in HTLV-I carriers and patients with HAM/TSP and ATL using three color fluorescence with CD62L and CD45RA coexpression either with CD4 or CD8 positive T-cells. The number of naive T-lymphocytes was markedly suppressed in patients with ATL, particularly in those with acute form, compared with uninfected control individuals. The number of naive T-cells was low in HTLV-I infected individuals under 50 year-old compared with uninfected individuals whereas the number of memory Tlymphocytes was greater in HTLV-I infected individuals. Although the increase of memory T-lymphocytes correlated wih HTLV-I provirus loads, no relationship was found between naive T-cell counts and provirus loads. T-cell receptor rearrangement excision circels(TREC), which are generated by DNA recombination during early T-lymphopoiesis, were quantified to evaluate thyrnic function in HTLV-I infected individuals. TREC levels were lower in HTLV-I infected individuals than in uninfected individuals. In less than 70 years old HTLV-I carriers, an increase of Epstein-Barr virus DNA in peripheral blood mononuclear cells was observed in 6 of 16(38%) examined whereas it was detectable in only one case of 11 uninfected controls. Our results strongly sugggested that the low number of naive T-lymphocytes was due to suppressed production of T-lymphocytes in the thymus, which might account for immunodeficiency observed in HTLV-I infected individuals. Less
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Research Products
(14 results)
