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The Rho exchange factors Vav2 and Vav3 favor skin tumor initiation and promotion by engaging extracellular signaling loops.

ABSTRACT: The catalytic activity of GDP/GTP exchange factors (GEFs) is considered critical to maintain the typically high activity of Rho GTPases found in cancer cells. However, the large number of them has made it difficult to pinpoint those playing proactive, nonredundant roles in tumors. In this work, we have investigated whether GEFs of the Vav subfamily exert such specific roles in skin cancer. Using genetically engineered mice, we show here that Vav2 and Vav3 favor cooperatively the initiation and promotion phases of skin tumors. Transcriptomal profiling and signaling experiments indicate such function is linked to the engagement of, and subsequent participation in, keratinocyte-based autocrine/paracrine programs that promote epidermal proliferation and recruitment of pro-inflammatory cells. This is a pathology-restricted mechanism because the loss of Vav proteins does not cause alterations in epidermal homeostasis. These results reveal a previously unknown Rho GEF-dependent pro-tumorigenic mechanism that influences the biology of cancer cells and their microenvironment. They also suggest that anti-Vav therapies may be of potential interest in skin tumor prevention and/or treatment.

SUBMITTER: Menacho-Marquez M

PROVIDER: S-EPMC3720258 | biostudies-literature | 2013 Jul

REPOSITORIES: biostudies-literature

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The Rho exchange factors Vav2 and Vav3 favor skin tumor initiation and promotion by engaging extracellular signaling loops.

Menacho-Márquez Mauricio M García-Escudero Ramón R Ojeda Virginia V Abad Antonio A Delgado Pilar P Costa Clotilde C Ruiz Sergio S Alarcón Balbino B Paramio Jesús M JM Bustelo Xosé R XR

PLoS biology 20130723 7

The catalytic activity of GDP/GTP exchange factors (GEFs) is considered critical to maintain the typically high activity of Rho GTPases found in cancer cells. However, the large number of them has made it difficult to pinpoint those playing proactive, nonredundant roles in tumors. In this work, we have investigated whether GEFs of the Vav subfamily exert such specific roles in skin cancer. Using genetically engineered mice, we show here that Vav2 and Vav3 favor cooperatively the initiation and p ...[more]

PMID: 23935450

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Project description:The guanosine triphosphatases of the Rho and Rac subfamilies regulate protumorigenic pathways and are activated by guanine nucleotide exchange factors (Rho GEFs), which could be potential targets for anticancer therapies. We report that two Rho GEFs, Vav2 and Vav3, play synergistic roles in breast cancer by sustaining tumor growth, neoangiogenesis, and many of the steps involved in lung-specific metastasis. The involvement of Vav proteins in these processes did not correlate with Rac1 and RhoA activity or cell migration, implying the presence of additional biological programs. Microarray analyses revealed that Vav2 and Vav3 controlled a vast transcriptional program in breast cancer cells through mechanisms that were shared between the two proteins, isoform-specific or synergistic. Furthermore, the abundance of Vav regulated transcripts was modulated by Rac1-dependent and Rac1-independent pathways. This transcriptome encoded therapeutically targetable proteins that played non redundant roles in primary tumorigenesis and lung-specific metastasis, such as integrin-linked kinase (Ilk), the transforming growth factorM-bM-^@M-^Sb family ligand inhibin bA, cyclooxygenase-2, and the epithelial cell adhesion molecule Tacstd2. It also contained gene signatures that predicted disease outcome in breast cancer patients. These results identify possible targets for treating breast cancer and lung metastases and provide a potential diagnostic tool for clinical use. All microarray experiments were performed by the personnel of the Genomics and Proteomics Unit of our Institution. Transcriptomal changes were determined using the Mouse Gene 1.0 ST arrays (Affymetrix). Two independent experiments were performed to identify the Vav2/Vav3-dependent transcriptome. In the first one, we compared the transcriptomes of Control, KD2/3(A) and KD2/3(B) to identify Vav family-dependent genes. In the second one, we compared the transcriptomes of KD2/3(A) and KD2/3+V2/3 cells. In all cases, total cellular RNA was extracted from three independent exponential cultures of the appropriate cell lines using the RNAeasy kit (Qiagen), quantified using 6000 Nano Chips (Agilent Technologies, Santa Clara, CA), and used (2.3 M-NM-<g/sample) to generated labeled cRNA probes according to the manufacturerM-bM-^@M-^Ys instructions (Affymetrix). Upon microarray hybridization, the raw data was normalized, filtered and analyzed with the Bioconductor software (www.bioconductor.com) using the Affy and Siggenes applications. Generation of knockdown cell lines. The shRNA-mediated knockdown of transcripts for Vav2 and Vav3 was carried out using already packaged Mission TRC lentiviral particles (Sigma-Aldrich) according to the manufacturerM-bM-^@M-^Ys protocol. The catalogue numbers and shRNA sequences yielding the greatest knockdown were clone number TRC0000097094 (5M-bM-^@M-^Y-CCGGGCCTGCATCTCTGGTTTAGATCTCGAGATCTAA ACCAGAGATGCAGGCTTTTTG-3M-bM-^@M-^Y) for the mouse Vav2 mRNA; TRC0000097124 (5M-bM-^@M-^Y-CCGGCCAGCATTTCTCGTCTTAAATCTCGAGATTTAA GACGAGAAATGCTGGTTTTTG-3M-bM-^@M-^Y) for the mouse Vav3 mRNA. Lentiviral particles containing the empty pLOK.1puro vector (Sigma-Aldrich) were used to generate the M-bM-^@M-^\ControlM-bM-^@M-^] 4T1 cells used in these experiments. Cells were incubated with lentiviral particles in the presence of 8 M-NM-<g/ml polybrene (Sigma), selected with puromycin (1 M-NM-<g/ml; Sigma), and used as either pools or isolated clones. Two clones of double Vav2;Vav3 knockdown cells (designated KD2/A(A) and KD2/3 (B)) were used in these experiments. Generation of rescued 4T1 cell lines. To generate the rescued KD2/3(A) cell line expressing both Vav2 and Vav3, cells were first infected with lentiviral particles produced from the pCCM33 vector (encoding wild type, HA-tagged Vav2) and then with lentiviral particles containing the pCQS1 vector (encoding wild type, Myc-tagged Vav3). Cells were then selected with hygromycin (present in the Vav2-encoding pCCM33 vector) and susbsequently sorted by flow cytometry to isolate GFP positive cells (which was expressed bicistronically from the same Vav3-encoding pCQS1 vector). A clone of double reconstituted cells was used in the microarray experiments and designated as KD2/3+V2/V3.

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The Rho exchange factors Vav2 and Vav3 favor skin tumor initiation and promotion by engaging extracellular signaling loops.

Publications

The Rho exchange factors Vav2 and Vav3 favor skin tumor initiation and promotion by engaging extracellular signaling loops.

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