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 factor–b 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.
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.
Project description:Cutaneous squamous tumors rely on autocrine/paracrine loops for proper fitness. Targeting this Achilles’ heel is therefore considered a potential avenue for patient treatment. However, the mechanisms that engage and sustain such programs during tumor ontogeny are poorly understood. Here, we show that two Rho/Rac activators, the exchange factors Vav2 and Vav3, control the expression of an epithelial autocrine/paracrine program that regulates keratinocyte survival and proliferation as well as the creation of an inflammatory microenvironment. Vav proteins are also critically involved in some of the subsequent autocrine signaling loops activated in keratinocytes. The genetic inactivation of both Vav proteins reduces tumor multiplicity without hampering skin homeostasis, thus suggesting that pan-specific Vav therapies may be useful in skin tumor prevention and treatment. The dorsal skin of WT and DKO mice (Vav2-/-;Vav3-/-) were treated with either one or four applications of phorbol ester 12-O-tetradecanoylphorbol-13 acetate (TPA) (6.8 nmol in 200 μl acetone) two days after shaving. As control, we applied 200 μl of acetone. Animals were euthanized 24 hours after treatment.
Project description:Here, we report that the Rho GTPase activators Vav2 and Vav3 utilize a new, miR-200c-dependent mechanism that maintains the epithelial state by limiting the abundance of the Zeb2 transcriptional repressor in breast cancer cells. In parallel, Vav proteins engage an expression program that maintains epithelial cell traits in 3D culture. Depletion of Vav proteins triggers EMT in epithelioid breast cancer cells and, conversely, expression of constitutively active Vav2 restores both miR-200c expression and epithelial traits in mesenchymal breast cancer cells. In silico analyses suggest that the negative Vav-Zeb2 axis is operative in human luminal breast tumors.
Project description:ERBB4 is a member of the epidermal growth factor receptor (EGFR)/ERBB subfamily of receptor tyrosine kinases that regulates cellular processes including proliferation, migration and survival. ERBB4 signaling is involved in embryogenesis and homeostasis of adult tissues, but also in human pathologies such as cancer, neurological disorders and cardiovascular diseases. A mass spectrometry screen revealed guanine nucleotide exchange factor (GEF) VAV3, an activator of Rho family GTPases, as a novel ERBB4-interacting protein in breast cancer cells. The ERBB4-VAV3-interaction was confirmed by targeted mass-spectrometry, coimmunoprecipitation experiments, and further defined by demonstrating that kinase activity and tyrosine residues 1022 and 1162 of ERBB4, as well as the intact phosphotyrosine-interacting SH2 domain of VAV3 were necessary for the interaction. ERBB4 was also shown to stimulate tyrosine phosphorylation of the VAV3 activation domain, which is required for GEF activity of VAV proteins. In addition to VAV3, also the other members of the VAV family, VAV1 and VAV2 were shown to coprecipitate with ERBB4. Analyses of the effects of overexpression of dominant-negative VAV3 constructs or downregulation of VAV3 expression by shRNAs in breast cancer cells demonstrated that active VAV3 was involved in ERBB4-stimulated migration. These findings define the VAV GTPases as novel effectors of ERBB4 activity in a signaling pathway relevant for cancer cell migration.
Project description:Cutaneous squamous tumors rely on autocrine/paracrine loops for proper fitness. Targeting this Achilles’ heel is therefore considered a potential avenue for patient treatment. However, the mechanisms that engage and sustain such programs during tumor ontogeny are poorly understood. Here, we show that two Rho/Rac activators, the exchange factors Vav2 and Vav3, control the expression of an epithelial autocrine/paracrine program that regulates keratinocyte survival and proliferation as well as the creation of an inflammatory microenvironment. Vav proteins are also critically involved in some of the subsequent autocrine signaling loops activated in keratinocytes. The genetic inactivation of both Vav proteins reduces tumor multiplicity without hampering skin homeostasis, thus suggesting that pan-specific Vav therapies may be useful in skin tumor prevention and treatment.
Project description:Acute B-cell lymphoblastic leukemia (B-ALL) represents a multiclonal evolution of B-cell progenitors endowed with both tumor-initiating and propagating properties. We have previously shown that the concurrent overexpression and activation of both the Rac guanine nucleotide exchange factor (RacGEF) Vav3 and Rac GTPases is required for BCR-ABL-mediated leukemogenesis. Here, we show that upon BCR-ABL expression, Vav3 expression becomes predominantly nuclear. In this location, Vav2 interacts with BCR-ABL, Rac, and the canonical polycomb repression complex proteins Bmi1, Ring1b and Ezh2. The GEF activity of Vav3 is required for B-cell proliferation and Bmi1-dependent B-cell progenitor self-renewal, nuclear Rac activation, protein interaction with Bmi1, H2A(K119) mono-ubiquitination (H2AK119Ub), and repression of downstream target loci. Vav3 deficiency results in de-repression and repression of loci encoding negative regulators of cell proliferation and oncogenic transcriptional factors, respectively. Mechanistically, we show that Vav3 prevents the Phlpp2-sensitive and Akt (S473)-dependent phosphorylation of Bmi1 on the regulatory residue S314 that, in turn, promotes the transcriptional factor reprogramming of leukemic B-cell progenitors. These results highlight the importance of non-canonical nuclear Rho GTPase signaling in leukemogenesis.
Project description:Acute B-cell lymphoblastic leukemia (B-ALL) represents a multiclonal evolution of B-cell progenitors endowed with both tumor-initiating and propagating properties. We have previously shown that the concurrent overexpression and activation of both the Rac guanine nucleotide exchange factor (RacGEF) Vav3 and Rac GTPases is required for BCR-ABL-mediated leukemogenesis. Here, we show that upon BCR-ABL expression, Vav3 expression becomes predominantly nuclear. In this location, Vav2 interacts with BCR-ABL, Rac, and the canonical polycomb repression complex proteins Bmi1, Ring1b and Ezh2. The GEF activity of Vav3 is required for B-cell proliferation and Bmi1-dependent B-cell progenitor self-renewal, nuclear Rac activation, protein interaction with Bmi1, H2A(K119) mono-ubiquitination (H2AK119Ub), and repression of downstream target loci. Vav3 deficiency results in de-repression and repression of loci encoding negative regulators of cell proliferation and oncogenic transcriptional factors, respectively. Mechanistically, we show that Vav3 prevents the Phlpp2-sensitive and Akt (S473)-dependent phosphorylation of Bmi1 on the regulatory residue S314 that, in turn, promotes the transcriptional factor reprogramming of leukemic B-cell progenitors. These results highlight the importance of non-canonical nuclear Rho GTPase signaling in leukemogenesis.
Project description:It is known that Rho GTPases control different aspects of the biology of skin stem cells (SSCs). However, little information is available on the role of its upstream regulators under normal and tumorigenic conditions in this process. To address this issue, we have used here mouse models in which the activity of guanosine nucleotide exchange factors of the Vav subfamily has been manipulated using both gain- and loss-of-function strategies. These experiments indicate that Vav2 and Vav3 regulate the number, functional status, and responsiveness of hair follicle bulge stem cells. This is linked to gene expression programs related to the reinforcement of the SSC identity and the quiescent state. By contrast, Vav proteins promote transcriptomal programs associated with the identity and activation state of SSCs in cancer stem cells.