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Molecular and Cellular Biology, March 1999, p. 1831-1840, Vol. 19, No. 3
The Wistar Institute, Philadelphia,
Pennsylvania 19104
Received 16 July 1998/Returned for modification 8 September
1998/Accepted 19 November 1998
Recent results have shown that the ability of farnesyltransferase
inhibitors (FTIs) to inhibit malignant cell transformation and Ras
prenylation can be separated. We proposed previously that farnesylated
Rho proteins are important targets for alternation by FTIs, based on
studies of RhoB (the FTI-Rho hypothesis). Cells treated with FTIs
exhibit a loss of farnesylated RhoB but a gain of geranylgeranylated
RhoB (RhoB-GG), which is associated with loss of growth-promoting
activity. In this study, we tested whether the gain of RhoB-GG elicited
by FTI treatment was sufficient to mediate FTI-induced cell growth
inhibition. In support of this hypothesis, when expressed in
Ras-transformed cells RhoB-GG induced phenotypic reversion, cell growth
inhibition, and activation of the cell cycle kinase inhibitor p21WAF1.
RhoB-GG did not affect the phenotype or growth of normal cells. These
effects were similar to FTI treatment insofar as they were all induced
in transformed cells but not in normal cells. RhoB-GG did not promote
anoikis of Ras-transformed cells, implying that this response to FTIs involves loss-of-function effects. Our findings corroborate the FTI-Rho
hypothesis and demonstrate that gain-of-function effects on Rho are
part of the drug mechanism. Gain of RhoB-GG may explain how FTIs
inhibit the growth of human tumor cells that lack Ras mutations.
0270-7306/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Cell Growth Inhibition by Farnesyltransferase
Inhibitors Is Mediated by Gain of Geranylgeranylated RhoB
*
Corresponding author. Mailing address: The Wistar
Institute, 3601 Spruce St., Philadelphia, PA 19104. Phone: (215)
898-3792. Fax: (215) 898-2205. E-mail:
prendergast{at}wista.wistar.upenn.edu.
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