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Dysregulation of c-Myb pathway by aberrant expression of proto-oncogene MYB provides the basis for malignancy in adult T-cell leukemia/lymphoma cells.

Authors: Nakano, K  Uchimaru, K  Utsunomiya, A  Yamaguchi, K  Watanabe, T 
Citation: Nakano K, etal., Clin Cancer Res. 2016 Jun 15. pii: clincanres.1739.2015.
Pubmed: (View Article at PubMed) PMID:27307595
DOI: Full-text: DOI:10.1158/1078-0432.CCR-15-1739

PURPOSE: Adult T-cell leukemia/lymphoma (ATLL) is an aggressive human T-cell malignancy induced by human T-lymphotrophic virus-1 (HTLV-1) infection. The genetic alterations in infected cells that lead to transformation have not been completely elucidated, thus hindering the identification of effective therapeutic targets for ATL. Here, we present the first assessment of MYB proto-oncogene dysregulation in ATL and an exploration of its role in the onset of ATL. EXPERIMENTAL DESIGN: We investigated the expression patterns of MYB splicing variants in ATL. The molecular characteristics of the c-Myb-9A isoform, which was overexpressed in ATL cells, were examined using chromatin immunoprecipitation and promoter assays. We further examined the biological impacts of abnormal c-Myb overexpression in ATL using overall c-Myb knockdown with small hairpin RNA or c-Myb-9A knockdown with morpholino oligomers. RESULTS: Both total c-Myb and c-Myb-9A, which exhibited strong transforming activity, were overexpressed in ATL cells in a leukemogenesis- and progression-dependent manner. Knockdown of either total c-Myb or c-Myb-9A induced ATL cell death. c-Myb transactivates nine genes that encode essential regulators of cell proliferation and NF-kappaB signaling. c-Myb-9A induced significantly stronger transactivation of all tested genes and stronger NF-kappaB activation compared with wild-type c-Myb. CONCLUSIONS: Our data demonstrate that c-Myb pathway overactivation caused by unbalanced c-Myb-9A overexpression is associated with disorders in cellular homeostasis and consequently, accelerated transformation, cell proliferation, and malignancy in ATL cells. These data support the notion of the c-Myb pathway as a promising new therapeutic target for ATL.

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RGD Object Information
RGD ID: 11532670
Created: 2016-09-02
Species: All species
Last Modified: 2016-09-02
Status: ACTIVE



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RGD is funded by grant HL64541 from the National Heart, Lung, and Blood Institute on behalf of the NIH.