GGTase-I deficiency reduces tumor formation and improves survival in mice with K-RAS–induced lung cancer
Anna-Karin M. Sjogren, … , Stephen G. Young, Martin O. Bergo
Anna-Karin M. Sjogren, … , Stephen G. Young, Martin O. Bergo
Published May 1, 2007
Citation Information: J Clin Invest. 2007;117(5):1294-1304. https://doi.org/10.1172/JCI30868.
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Research Article

GGTase-I deficiency reduces tumor formation and improves survival in mice with K-RAS–induced lung cancer

Abstract

Protein geranylgeranyltransferase type I (GGTase-I) is responsible for the posttranslational lipidation of CAAX proteins such as RHOA, RAC1, and cell division cycle 42 (CDC42). Inhibition of GGTase-I has been suggested as a strategy to treat cancer and a host of other diseases. Although several GGTase-I inhibitors (GGTIs) have been synthesized, they have very different properties, and the effects of GGTIs and GGTase-I deficiency are unclear. One concern is that inhibiting GGTase-I might lead to severe toxicity. In this study, we determined the effects of GGTase-I deficiency on cell viability and K-RAS–induced cancer development in mice. Inactivating the gene for the critical β subunit of GGTase-I eliminated GGTase-I activity, disrupted the actin cytoskeleton, reduced cell migration, and blocked the proliferation of fibroblasts expressing oncogenic K-RAS. Moreover, the absence of GGTase-I activity reduced lung tumor formation, eliminated myeloproliferative phenotypes, and increased survival of mice in which expression of oncogenic K-RAS was switched on in lung cells and myeloid cells. Interestingly, several cell types remained viable in the absence of GGTase-I, and myelopoiesis appeared to function normally. These findings suggest that inhibiting GGTase-I may be a useful strategy to treat K-RAS–induced malignancies.

Authors

Anna-Karin M. Sjogren, Karin M.E. Andersson, Meng Liu, Briony A. Cutts, Christin Karlsson, Annika M. Wahlstrom, Martin Dalin, Carolyn Weinbaum, Patrick J. Casey, Andrej Tarkowski, Birgitta Swolin, Stephen G. Young, Martin O. Bergo

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Figure 1

Generation of a conditional knockout allele for the β subunit of GGTase-I (Pggt1bfl).

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Generation of a conditional knockout allele for the β subunit of GGTase-...
(A) A sequence-replacement gene-targeting vector in which exon 7 of Pggt1b is flanked by loxP sites (arrowheads). Expression of Cre recombinase results in the excision of exon 7, creating a frameshift mutation and a null allele. The locations of primers for genotyping are indicated. neo, neomycin phosphotransferase cassette; tk, thymidine kinase. (B) PCR and RT-PCR analyses demonstrating the Cre-induced inactivation of Pggt1b. Heterozygous Pggt1bfl/+ and homozygous Pggt1bfl/fl fibroblasts were treated with either a β-gal– or a Cre-adenovirus, and genomic DNA and total RNA were isolated 2 days later. (C) GGTase-I and FTase activity in extracts of β-gal– and Cre-adenovirus–treated Pggt1bfl/fl fibroblasts. Values are mean ± SEM of 2 different cell lines in 2 independent experiments. (D) Western blots of extracts from 2 different Pggt1bfl/fl fibroblast cell lines treated with β-gal– and Cre-adenovirus. The blots were incubated with antibodies recognizing nonprenylated RAP1, total RAP1, and RHOA. Total ERK1/2 was used as a loading control. (E) Distribution of nonprenylated RAP1 and total RAP1 proteins in the membrane (pellet [P]) and cytosolic (soluble [S]) fractions of β-gal– or Cre-adenovirus–treated Pggt1bfl/fl fibroblasts. T, total extract.