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Journal
of the National Cancer Institute, Vol. 94, No. 4, 239, February 20, 2002
© 2002 Oxford
University Press
Press Release
Viral Protein May be Associated with Human Brain Tumors
Researchers have found that a specific protein called agnoprotein, which
is produced by a virus, is present in human brain tumors, suggesting
a possible role for the virus in the development of medulloblastoma,
the most frequent type of malignant brain tumor in children.
Luis Del Valle, M.D., and Kamel Khalili, Ph.D., of Temple University in
Philadelphia, and their coworkers found that some medulloblastomas contain
only agnoprotein and not T antigen, another protein believed to play
a role in the development of several types of brain tumors. Their
findings appear in the Feb. 20 issue of the Journal of the
National Cancer Institute.
Both agnoprotein and T antigen are protein products of the JC virus
(JCV), a human polyomavirus that can cause progressive multifocal
leukoencephalopathy (PML), a fatal disease frequently seen in AIDS
patients. In the absence of PML, JCV may stimulate rapid and
uncontrolled cell growth, leading to cancer, the authors note. The
virus is transmitted early in life, infecting 65% of children by the
age of 14. The virus is most likely transmitted through the parent,
the authors note, and may enter a child’s developing brain through
infected B cells.
T antigen may cause brain tumors in part by blocking tumor suppressor proteins
such as p53 and pRb. The role of agnoprotein in the development of
brain tumors is unknown. Recent studies suggest, however, that the
interaction of T antigen with agnoprotein may effect T antigen’s
ability to enhance replication of the viral genes.
In the current study, the authors found the presence of the gene
that encodes agnoprotein in 69% of 16 medulloblastoma samples, and T
antigen DNA in 65% of 20 medulloblastoma samples. The authors found
agnoprotein and T antigen in 45% of 20 medulloblastoma samples; 2
out of the 20 samples contained only agnoprotein. The authors
conclude that "the finding of agnoprotein expression in the
absence of T antigen expression suggests a potential role for
agnoprotein in pathways involved in the development of
JCV-associated medulloblastomas."
In a related editorial, Howard A. Fine, M.D, of the Neuro-Oncology Branch
of the National Cancer Institute and the National Institute of
Neurologic Disorders and Stroke says this is a "provocative assertion,"
but cautions that, "the presence of these sequences in tumor
cells may merely represent genetic remnants of a prior abortive
infection in an earlier progenitor cell that ultimately happened to
turn tumorigenic."
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Contact: Preston Moretz, Temple University, (215) 204-7476; fax:
(215) 204-4403, pmoretz@temple.edu
Editorial: NCI Press Office, (301) 496-6641
Del Valle L, Gordon J, Enam S, Delbue S, Croul S, Abraham S, Radhakrishnan
S, Assimakapoulou M, Katsetos CD, Khalili K. Expression of human
polyomavirus JCV late gene product agnoprotein in human medulloblastoma.
J Natl Cancer Inst 2002;94:267–73.
Editorial: Fine HA. Polyomavirus and medulloblastoma: a smoking gun
or guilt by association? J Natl Cancer Inst 2002;94:240–1.
Attribution to the Journal of the National Cancer Institute is
requested in all news coverage.
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