Table of Contents
ISRN Microbiology
Volume 2012 (2012), Article ID 978607, 11 pages
Research Article

Important Roles of Cellular MicroRNA miR-155 in Leukemogenesis by Human T-Cell Leukemia Virus Type 1 Infection

Department of Pathology and Oncology, Graduate School of Medical Science, University of the Ryukyus, 207 Uehara, Nishihara, Okinawa 903-0215, Japan

Received 3 July 2012; Accepted 13 August 2012

Academic Editors: C. K. Cote, T. Krishnan, and A. Tavanti

Copyright © 2012 Mariko Tomita. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Human T-cell leukemia virus type 1 (HTLV-1) is the pathogen that causes the aggressive and lethal malignancy of CD4+ T-lymphocytes called adult T-cell leukemia/lymphoma (ATLL). MicroRNAs (miRNAs), a class of short, noncoding RNAs, regulate gene expression by targeting mRNAs for translational repression or cleavage. miRNAs are involved in many aspects of cell biology linked with formation of several cancer phenotypes. However, the relation between miRNAs and pathologic implication in ATLL is not well elucidated. Here, we evaluated the roles of cellular miRNAs in ATLL caused by HTLV-1. We found that the expression of miR-155 was increased in HTLV-1-positive T-cell lines. miR-155 expression was enhanced by Tax and binding of transcription factors, NF-κB and AP-1, on the transcription binding sites of miR-155 gene promoter region is important to increase the expression of miR-155 by Tax. Transfection of anti-miR-155 inhibitor, which inhibits the function of miR-155, inhibited the growth of HTLV-1-positive T-cell lines. On the other hand, the growth of HTLV-1-negative T-cell lines was not changed by transfection of anti-miR-155. Forced expression of miR-155 enhanced the growth of HTLV-1-positive T-cell lines. These findings indicate that targeting the functions of miRNAs is a novel approach to the prevention or treatment of ATLL.