Haploinsufficiency for p190B RhoGAP Inhibits MMTV-Neu Tumor Progression

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Haploinsufficiency for p190B RhoGAP Inhibits MMTV-Neu Tumor Progression

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Title: Haploinsufficiency for p190B RhoGAP Inhibits MMTV-Neu Tumor Progression
Author: Heckman-Stoddard, Brandy M; Vargo-Gogola, Tracy; McHenry, Peter R; Jiang, Vivian; Herrick, Matthew P; Hilsenbeck, Susan G; Settleman, Jeffrey Evan; Rosen, Jeffrey M.

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Citation: Heckman-Stoddard, Brandy M., Tracy Vargo-Gogola, Peter R. McHenry, Vivian Jiang, Matthew P. Herrick, Susan G. Hilsenbeck, Jeffrey Settleman, and Jeffrey M. Rosen. 2009. Haploinsufficiency for p190B RhoGAP inhibits MMTV-Neu tumor progression. Breast Cancer Research 11(4): R61.
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Abstract: Introduction: Rho signaling regulates key cellular processes including proliferation, survival, and migration, and it has been implicated in the development of many types of cancer including breast cancer. P190B Rho GTPase activating protein (RhoGAP) functions as a major inhibitor of the Rho GTPases. P190B is required for mammary gland morphogenesis, and overexpression of p190B in the mammary gland induces hyperplastic lesions. Hence, we hypothesized that p190B may play a pivotal role in mammary tumorigenesis. Methods: To investigate the effects of loss of p190B function on mammary tumor progression, p190B heterozygous mice were crossed with an MMTV-Neu breast cancer model. Effects of p190B deficiency on tumor latency, multiplicity, growth, preneoplastic progression and metastasis were evaluated. To investigate potential differences in tumor angiogenesis between the two groups, immunohistochemistry to detect von Willebrand factor was performed and quantified. To examine gene expression of potential mediators of the angiogenic switch, an angiogenesis PCR array was utilized and results were confirmed using immunohistochemistry. Finally, reciprocal transplantation of tumor fragments was performed to determine the impact of stromal deficiency of p190B on tumor angiogenesis. Results: P190B deficiency reduced tumor penetrance (53% of \(p190B^{+/-}Neu\) mice vs. 100% of \(p190B^{+/+}Neu\) mice formed tumors) and markedly delayed tumor onset by an average of 46 weeks. Tumor multiplicity was also decreased, but an increase in the number of preneoplastic lesions was detected indicating that p190B deficiency inhibited preneoplastic progression. Angiogenesis was decreased in the p190B heterozygous tumors, and expression of a potent angiogenic inhibitor, thrombospondin-1, was elevated in \(p190B^{+/-}Neu\) mammary glands. Transplantation of \(p190B^{+/-}Neu\) tumor fragments into wild-type recipients restored tumor angiogenesis. Strikingly, \(p190B^{+/+}Neu\) tumor fragments were unable to grow when transplanted into \(p190B^{+/-}Neu\) recipients. Conclusions: These data suggest that p190B haploinsufficiency in the epithelium inhibits MMTV-Neu tumor initiation. Furthermore, p190B deficiency in the vasculature is responsible, in part, for the inhibition of MMTV-Neu tumor progression.
Published Version: doi:10.1186/bcr2352
Other Sources: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2750123/pdf/
Terms of Use: This article is made available under the terms and conditions applicable to Other Posted Material, as set forth at http://nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of-use#LAA
Citable link to this page: http://nrs.harvard.edu/urn-3:HUL.InstRepos:5350704

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