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Antoine E. Karnoub

Bio: Antoine E. Karnoub is an academic researcher from Harvard University. The author has contributed to research in topics: Metastasis & Cancer. The author has an hindex of 23, co-authored 37 publications receiving 6407 citations. Previous affiliations of Antoine E. Karnoub include Massachusetts Institute of Technology & University of North Carolina at Chapel Hill.

Papers
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Journal ArticleDOI
04 Oct 2007-Nature
TL;DR: It is demonstrated that bone-marrow-derived human mesenchymal stem cells, when mixed with otherwise weakly metastatic human breast carcinoma cells, cause the cancer cells to increase their metastatic potency greatly when this cell mixture is introduced into a subcutaneous site and allowed to form a tumour xenograft.
Abstract: Mesenchymal stem cells have been recently described to localize to breast carcinomas, where they integrate into the tumour-associated stroma. However, the involvement of mesenchymal stem cells (or their derivatives) in tumour pathophysiology has not been addressed. Here, we demonstrate that bone-marrow-derived human mesenchymal stem cells, when mixed with otherwise weakly metastatic human breast carcinoma cells, cause the cancer cells to increase their metastatic potency greatly when this cell mixture is introduced into a subcutaneous site and allowed to form a tumour xenograft. The breast cancer cells stimulate de novo secretion of the chemokine CCL5 (also called RANTES) from mesenchymal stem cells, which then acts in a paracrine fashion on the cancer cells to enhance their motility, invasion and metastasis. This enhanced metastatic ability is reversible and is dependent on CCL5 signalling through the chemokine receptor CCR5. Collectively, these data demonstrate that the tumour microenvironment facilitates metastatic spread by eliciting reversible changes in the phenotype of cancer cells.

2,997 citations

Journal ArticleDOI
TL;DR: Despite great strides in understanding of the molecular and cellular mechanisms of action of the Ras proteins, the expanding roster of their downstream effectors and the complexity of the signalling cascades that they regulate indicate that much remains to be learnt.
Abstract: Extensive research over the past 30 years has revealed the involvement of Ras not only in tumorigenesis but also in many developmental disorders. The complexity of the molecular and cell biological mechanisms of action of Ras proteins indicates that much remains to be learnt.

1,355 citations

Journal ArticleDOI
TL;DR: Using oncogenic Ras mutants that activate single effectors as well as constitutively active effectors, it is found that the RalGEF, and not the Raf or PI3-kinase pathway, is sufficient for Ras transformation in human cells.
Abstract: The spectrum of tumors associated with oncogenic Ras in humans often differs from those in mice either treated with carcinogens or engineered to sporadically express oncogenic Ras, suggesting that the mechanism of Ras transformation may be different in humans. Ras stimulates primarily three main classes of effector proteins, Rafs, PI3-kinase, and RalGEFs, with Raf generally being the most potent at transforming murine cells. Using oncogenic Ras mutants that activate single effectors as well as constitutively active effectors, we find that the RalGEF, and not the Raf or PI3-kinase pathway, is sufficient for Ras transformation in human cells. Thus, oncogenic Ras may transform murine and human cells by distinct mechanisms, and the RalGEF pathway—previously deemed to play a secondary role in Ras transformation—could represent a new target for anti-cancer therapy.

461 citations

Journal ArticleDOI
TL;DR: Compared tumors derived from two different normal human mammary epithelial cell populations, one of which was isolated using a new culture medium, found that the pre-existing differences between BPECs and HMECs strongly influence the phenotypes of their transformed derivatives.

315 citations

Journal ArticleDOI
16 Dec 2004-Oncogene
TL;DR: Surprisingly, it is found that Rac1b, like the constitutively-activated and transforming Rac1(Q61L) mutant, promoted growth transformation of NIH3T3 cells and selectively activates a subset of Rac1 downstream signaling pathways to facilitate cellular transformation.
Abstract: A novel splice variant of Rac1, designated Rac1b, is expressed in human breast and colon carcinoma cells. Rac1b contains an additional 19 amino-acid insert immediately behind the switch II domain, a region important for Rac1 interaction with regulators and effectors. Recent studies showed that Rac1b exhibited the biochemical properties of a constitutively activated GTPase, yet it showed impaired interaction with downstream effectors, suggesting that Rac1b may be defective in biological activity. Whether Rac1b is a biologically active protein was not addressed. Therefore, we evaluated the biochemical, signaling and growth-promoting properties of authentic Rac1b. Similar to previous observations, we found that Rac1b showed enhanced intrinsic guanine nucleotide exchange activity, impaired intrinsic GTPase activity, and failed to interact with RhoGDI. Surprisingly, we found that Rac1b, like the constitutively-activated and transforming Rac1(Q61L) mutant, promoted growth transformation of NIH3T3 cells. Rac1b-expressing cells also showed a loss of density-dependent and anchorage-dependent growth. Surprisingly, unlike activated Rac1(61L), Rac1b did not show enhanced activation of the nuclear factor kappaB (NF-kappaB) transcription factor or stimulate cyclin D1 expression, the signaling activities that best correlate with Rac1 transforming activity. However, Rac1b did promote activation of the AKT serine/threonine kinase. Therefore, we suggest that Rac1b selectively activates a subset of Rac1 downstream signaling pathways to facilitate cellular transformation.

187 citations


Cited by
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Journal ArticleDOI
04 Mar 2011-Cell
TL;DR: Recognition of the widespread applicability of these concepts will increasingly affect the development of new means to treat human cancer.

51,099 citations

Journal ArticleDOI
25 Nov 2009-Cell
TL;DR: The mesenchymal state is associated with the capacity of cells to migrate to distant organs and maintain stemness, allowing their subsequent differentiation into multiple cell types during development and the initiation of metastasis.

8,642 citations

Journal ArticleDOI
TL;DR: The paradoxical roles of the tumor microenvironment during specific stages of cancer progression and metastasis are discussed, as well as recent therapeutic attempts to re-educate stromal cells within the TME to have anti-tumorigenic effects.
Abstract: Cancers develop in complex tissue environments, which they depend on for sustained growth, invasion and metastasis. Unlike tumor cells, stromal cell types within the tumor microenvironment (TME) are genetically stable and thus represent an attractive therapeutic target with reduced risk of resistance and tumor recurrence. However, specifically disrupting the pro-tumorigenic TME is a challenging undertaking, as the TME has diverse capacities to induce both beneficial and adverse consequences for tumorigenesis. Furthermore, many studies have shown that the microenvironment is capable of normalizing tumor cells, suggesting that re-education of stromal cells, rather than targeted ablation per se, may be an effective strategy for treating cancer. Here we discuss the paradoxical roles of the TME during specific stages of cancer progression and metastasis, as well as recent therapeutic attempts to re-educate stromal cells within the TME to have anti-tumorigenic effects.

5,396 citations

Journal ArticleDOI
TL;DR: Most of the hallmarks of cancer are enabled and sustained to varying degrees through contributions from repertoires of stromal cell types and distinctive subcell types, which presents interesting new targets for anticancer therapy.

3,486 citations

Journal ArticleDOI
TL;DR: Experimental data demonstrating the role of the microenvironment in metastasis is described, areas for future research are identified and possible new therapeutic avenues are suggested.
Abstract: Metastasis is a multistage process that requires cancer cells to escape from the primary tumour, survive in the circulation, seed at distant sites and grow. Each of these processes involves rate-limiting steps that are influenced by non-malignant cells of the tumour microenvironment. Many of these cells are derived from the bone marrow, particularly the myeloid lineage, and are recruited by cancer cells to enhance their survival, growth, invasion and dissemination. This Review describes experimental data demonstrating the role of the microenvironment in metastasis, identifies areas for future research and suggests possible new therapeutic avenues.

3,332 citations