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J. Virol., Nov 1997, 8149-8156, Vol 71, No. 11
KC Thome, A Radfar and N Rosenberg
Abelson murine leukemia virus transforms pre-B cells in vitro and induces
rapid-onset pre-B-cell lymphoma in vivo. Expression of an active v-Abl
protein tyrosine kinase is required for the oncogenic functions of the
virus. Despite the strong growth-stimulatory signal provided by v-Abl, the
virus-induced tumors are clonal or oligoclonal, and changes in the growth
and oncogenic potential of in vitro transformants occur during the
derivation of the cell lines. Both of these features suggest that v-Abl
expression must be complemented by changes in expression of one or more
cellular genes for cells to acquire a fully malignant phenotype. Such genes
could include other oncogenes or tumor suppressor genes. Among the latter
is Tp53, a gene mutated in many spontaneous cancers. To determine if
mutation of the Tp53 tumor suppressor gene plays a role in Abelson virus
transformation, conformation-specific monoclonal antibodies were used to
examine p53 expression in a panel of Abelson virus-transformed pre-B cells.
Expression of mutant forms of p53 was detected in over 40% of the isolates.
Sequence analysis revealed the presence of point mutations affecting the
highly conserved central portion of the protein. These mutations interfered
with the ability of p53 to activate transcription from a promoter
containing p53-responsive elements and to induce apoptosis in response to
DNA damage. In addition, cells expressing mutant forms of p53 induced a
higher frequency of tumors with a more rapid course compared to
transformants expressing wild-type p53. These data suggest that Tp53 is one
important cellular gene involved in malignant transformation by Abelson
virus.
Copyright © 1997, American Society for Microbiology
Mutation of Tp53 contributes to the malignant phenotype of Abelson virus-transformed lymphoid cells
Department of Pathology and Graduate Program in Immunology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
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