Anti-VAV2 monoclonal antibody, clone NBD 522

Melanoma cells express the chemokine receptor CXCR4, which confers invasive signals on binding to its ligand CXCL12. We show here that knocking down membrane-type matrix metalloproteinase (MT1-MMP) expression translates into a blockade of invasion across reconstituted basement membranes and type I collagen gels in response to CXCL12, which is the result of lack of MMP-2 activation. Interference with MMP-2 expression further confirms its important role during this invasion. Vav proteins are guanine-nucleotide exchange factors for Rho GTPases that regulate actin dynamics and gene expression. We show that melanoma cells express Vav1 and Vav2, which are activated by CXCL12 involving Jak activity. Blocking Vav expression by RNA interference results in impaired activation of Rac and Rho by CXCL12 and in a remarkable inhibition of CXCL12-promoted invasion. Importantly, up-regulation of MT1-MMF expression by CXCL12, a mechanism contributing to melanoma cell invasion, is blocked by knocking down Vav expression or by inhibiting Jak. Together, these data indicate that activation of jak/Vav/ Rho GTPase pathway by CXCL12 is a key signaling event for MT1-MMP/MMP-2-dependent melanoma cell invasion.

Proper lung development depends on the precise temporal and spatial expression of several morphogenic factors, including Fgf10, Fgf9, Shh, Bmp4, and Tgf-beta. Over- or under-expression of these molecules often leads to aberrant embryonic or postnatal lung development. Herein, we deleted the Tgf-beta 1 gene specifically within the lung embryonic mesenchymal compartment at specific gestational stages to determine the contribution of this cytokine to lung development. Mutant embryos developed severe lung hypoplasia and died at birth due to the inability to breathe. Despite the markedly reduced lung size, proliferation and differentiation of the lung epithelium was not affected by the lack of mesenchymal expression of the Tgf-beta 1 gene, while apoptosis was significantly increased in the mutant lung parenchyma. Lack of mesenchymal expression of the Tgf-beta 1 gene was also associated with reduced lung branching morphogenesis, with accompanying inhibition of the local FGF10 signaling pathway as well as abnormal development of the vascular system. To shed light on the mechanism of lung hypoplasia, we quantified the phosphorylation of 226 proteins in the mutant E12.5 lung compared with control. We identified five proteins, Hrs, Vav2, c-Kit, the regulatory subunit of Pi3k (P85), and Fgfrl, that were over- or under-phosphorylated in the mutant lung, suggesting that they could be indispensable effectors of the TGF-beta signaling program during embryonic lung development. In conclusion, we have uncovered novel roles of the mesenchyme-specific Tgf-beta 1 ligand in embryonic mouse lung development and generated a mouse model that may prove helpful to identify some of the key pathogenic mechanisms underlying lung hypoplasia in humans.