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J Virol, June 1998, p. 4980-4988, Vol. 72, No. 6
Department of Microbiology and
Immunology1 and
Department of
Pathology,2 Georgetown University Medical
Center, Washington, D.C. 20007;
Laboratory of Molecular
Virology, National Cancer Institute, Bethesda, Maryland
208923; and
Department of Medical
Microbiology and Immunology, University of South Florida, Tampa,
Florida 336124
Received 17 December 1997/Accepted 2 March 1998
The recently identified human herpesvirus 8 (HHV-8, or Kaposi's
sarcoma-associated herpesvirus) has been implicated in the etiology of
both Kaposi's sarcoma (KS) and primary effusion (body cavity-based)
lymphoma (PEL) (Y. Chang et al., Science 266:1865-1869, 1994; P. S. Moore et al., J. Virol. 70:549-558, 1996). An important feature of the association of HHV-8 with these malignancies is the
expression of an abundant, latency-associated 0.7-kb transcript, T0.7
(W. Zhong et al., Proc. Natl. Acad. Sci. USA 93:6641-6646, 1996). T0.7
is found in all stages in nearly all KS tumors of different
epidemiologic origin, including AIDS-associated, African endemic, and
classical KS (K. A. Staskus et al., J. Virol. 71:715-719, 1997), as well as in a body cavity-based lymphoma-derived cell line,
BCBL-1, that is latently infected with HHV-8 (R. Renne et al., Nat.
Med. 2:342-346, 1996). T0.7 encodes a unique HHV-8 open reading frame,
K12, also known as kaposin. In this study, we report that the kaposin
gene induced tumorigenic transformation. Constructs with kaposin
expressed either from its endogenous promoter or from a heterologous
promoter induced focal transformation upon transfection into Rat-3
cells. All transformed Rat-3 cell lines containing kaposin sequences
produced high-grade, highly vascular, undifferentiated sarcomas upon
subcutaneous injection of athymic nu/nu mice.
Tumor-derived cell lines expressed kaposin mRNA, suggesting a role in
the maintenance of the transformed phenotype. Furthermore, kaposin
protein was detected in transformed and tumor-derived cells by
immunofluorescence and localized to the cytoplasm. More importantly,
expression of kaposin protein was also detected in the PEL cell lines
BCBL-1 and KS-1. These findings demonstrate the oncogenic potential of
kaposin and suggest its possible role in the development of KS and
other HHV-8-associated malignancies.
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Identification of Kaposin (Open Reading Frame K12)
as a Human Herpesvirus 8 (Kaposi's Sarcoma-Associated Herpesvirus)
Transforming Gene
*
Corresponding author. Mailing address: Department of
Microbiology and Immunology, Georgetown University Medical Center, 3900 Reservoir Rd., NW, Washington, D.C. 20007. Phone: (202) 687-1140. Fax:
(202) 687-1264. E-mail: rosenthl{at}gunet.georgetown.edu.
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