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Mol. Cell. Biol., Dec 1995, 6513-6525, Vol 15, No. 12
M Auvinen, A Paasinen-Sohns, H Hirai, LC Andersson and E Holtta
We have found that overexpression of human ornithine decarboxylase (ODC)
induces cell transformation in NIH 3T3 and Rat-1 cells (M. Auvinen, A.
Paasinen, L. C. Andersson, and E. Holtta, Nature (London) 360:355-358,
1992). The ODC-transformed cells display increased levels of tyrosine
phosphorylation, in particular of a cluster of 130-kDa proteins. Here we
show that one of the proteins with enhanced levels of tyrosine
phosphorylation in ODC-overexpressing cells is the previously described
p130 substrate of pp60v-src, known to associate also with v- Crk and
designated p130CAS. We also studied the role of protein tyrosine
phosphorylation in the ODC-induced cell transformation by exposing the
cells to herbimycin A, a potent inhibitor of Src-family kinases, and to
other inhibitors of protein tyrosine kinases. Treatment with the inhibitors
reversed the phenotype of ODC-transformed cells to normal, with an
organized, filamentous actin cytoskeleton. Coincidentally, the tyrosine
hyperphosphorylation of p130 was markedly reduced, while the level of
activity of ODC remained highly elevated. A similar reduction in pp130
phosphorylation and reversion of morphology by herbimycin A were observed
in v-src- and c-Ha-ras-transformed cells. In addition, we show that
expression of antisense mRNA for p130CAS resulted in reversion of the
transformed phenotype of all these cell lines. An increased level of
tyrosine kinase activity, not caused by c- Src or c-Abl, was further
detected in the cytoplasmic fraction of ODC- transformed cells. Preliminary
characteristics of this kinase are shown. These data indicate that p130CAS
is involved in cell transformation by ODC, c-ras, and v-src oncogenes,
raise the intriguing possibility that p130CAS may be generally required for
transformation, and imply that there is at least one protein tyrosine
kinase downstream of ODC that is instrumental for cell transformation.
Copyright © 1995, American Society for Microbiology
Ornithine decarboxylase- and ras-induced cell transformations: reversal by protein tyrosine kinase inhibitors and role of pp130CAS
Department of Pathology, Haartman Institute, University of Helsinki, Finland.
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