Affiliation:
1. University of Kansas Medical Center, Department of Pathology and Laboratory Medicine, Center for Viral Oncology, KU Cancer Center, Kansas City
Abstract
Human T-cell leukemia virus type I (HTLV-I)–associated malignancies are seen in a small percentage of infected persons. Although in vitro immortalization by HTLV-I virus is very efficient, we report that Tax has poor oncogenic activity in human primary T cells and that immortalization by Tax is rare. Sustained telomerase activity represents one of the oncogenic steps required for Tax-mediated immortalization. Tax expression was required for the growth of primary T cells, but was not sufficient to propel T cells into cell cycle in the absence of exogenous interleukin-2 (IL-2). Tax was sufficient to activate the phosphoinositide-3 kinase (PI3K)/Akt pathway as shown by down regulation of Src homology phosphatase-1 and increased phosphorylation of Akt. We also found disruption of putative tumor suppressors IL-16 and translocated promoter region (TPR) in Tax-immortalized and HTLV-I–transformed cell lines. Our results confirmed previous observations that Tax activates the anaphase-promoting complex. However, Tax did not affect the mitotic spindle checkpoint, which was also functional in HTLV-I–transformed cells. These data provide a better understanding of Tax functions in human T cells, and highlight the limitations of Tax, suggesting that other viral proteins are key to T-cell transformation and development of adult T-cell leukemia.
Publisher
American Society of Hematology
Subject
Cell Biology,Hematology,Immunology,Biochemistry
Cited by
53 articles.
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