Caveolin-1-Enhanced Motility and Focal Adhesion Turnover Require Tyrosine-14 but Not Accumulation to the Rear in Metastatic Cancer Cells

Caveolin-1 is known to promote cell migration, and increased caveolin-1 expression is associated with tumor progression and metastasis. In fibroblasts, caveolin-1 polarization and phosphorylation of tyrosine-14 are essential to promote migration. However, the role of caveolin-1 in migration of metastatic cells remains poorly defined. Here, caveolin-1 participation in metastatic cell migration was evaluated by shRNA targeting of endogenous caveolin-1 in MDA-MB-231 human breast cancer cells and ectopic expression in B16-F10 mouse melanoma cells. Depletion of caveolin-1 in MDA-MB-231 cells reduced, while expression in B16-F10 cells promoted migration, polarization and focal adhesion turnover in a sequence of events that involved phosphorylation of tyrosine-14 and Rac-1 activation. In B16-F10 cells, expression of a non-phosphorylatable tyrosine-14 to phenylalanine mutant failed to recapitulate the effects observed with wild-type caveolin-1. Alternatively, treatment of MDA-MB-231 cells with the Src family kinase inhibitor PP2 reduced caveolin-1 phosphorylation on tyrosine-14 and cell migration. Surprisingly, unlike for fibroblasts, caveolin-1 polarization and re-localization to the trailing edge were not observed in migrating metastatic cells. Thus, expression and phosphorylation, but not polarization of caveolin-1 favor the highly mobile phenotype of metastatic cells

Regulation of angiogenesis by tissue factor cytoplasmic domain signaling

Hemostasis initiates angiogenesis-dependent wound healing, and thrombosis is frequently associated with advanced cancer. Although activation of coagulation generates potent regulators of angiogenesis, little is known about how this pathway supports angiogenesis in vivo. Here we show that the tissue factor (TF)-VIIa protease complex, independent of triggering coagulation, can promote tumor and developmental angiogenesis through protease-activated receptor-2 (PAR-2) signaling. In this context, the TF cytoplasmic domain negatively regulates PAR-2 signaling. Mice from which the TF cytoplasmic domain has been deleted (TFDeltaCT mice) show enhanced PAR-2-dependent angiogenesis, in synergy with platelet-derived growth factor BB (PDGF-BB). Ocular tissue from diabetic patients shows PAR-2 colocalization with phosphorylated TF specifically on neovasculature, suggesting that phosphorylation of the TF cytoplasmic domain releases its negative regulatory control of PAR-2 signaling in angiogenesis. Targeting the TF-VIIa signaling pathway may thus enhance the efficacy of angiostatic treatments for cancer and neovascular eye diseases

Morphine and breast tumor metastasis: the role of matrix-degrading enzymes

Opioids including morphine are commonly used in pain management during and after cancer surgery but have been linked to a variety of pro- and anti-tumor effects. In the present study the effect of morphine administration on the localization and growth of breast tumor cells in lungs and the level of extracellular matrix (ECM) proteases were investigated. In a mouse syngeneic model of intravenously inoculated breast cancer cells, morphine administration led to a reduction in the localization and growth of tumors in the lungs and a reduction in circulating matrix metalloproteinase-9 (MMP-9) and urokinase-like plasminogen activator (uPA). To model the involvement of non-malignant cells of the tumor microenvironment in the changes we observed in the level of proteases, we co-cultured breast cancer cells with macrophages, endothelial cells and fibroblasts. We found a significant elevation of matrix proteases as well as matrix protease inhibitors in co-cultures of breast cancer cells with macrophages or endothelial cells. Interestingly, morphine treatment of these co-cultures reduced the level of MMP-9 and increased its endogenous inhibitor, TIMP-1, thereby altering the proteolytic profile. Morphine affected the level of enzymes in co-cultures but not in cells grown individually. This suggests that anti-tumor effects of morphine observed in our in vivo model could be mediated at least in part through modulation of paracrine communication between cancer cells and non-malignant cells in the tumor microenvironment

Caveolin-1 polarization in transmigrating endothelial cells requires binding to intermediate filaments

Caveolin-1 influences cell migration through multiple signaling pathways. In a previous report, we have shown that caveolin-1 is polarized in three-dimensional migrating endothelial cells (EC), and that caveolin-1 accumulation at the front of transmigrating cells requires the phosphorylatable Tyr14 residue of caveolin-1. Immuno-electron microscopy further indicated that caveolin-1 was distributed along cytoskeletal structures in the anterior of transmigrating EC [Parat MO, Anand-Apte B, Fox PL (Mol Biol Cell 14:3156–3168, 2003)]. In the present study, we investigate whether caveolin-1 interacts with intermediate filaments (IF) and whether this interaction is required for caveolin-1 polarization in transmigrating cells. The distribution of vimentin is polarized in cells traversing a filter pore and overlaps with the distribution of caveolin-1, which accumulates in the cell front. In vivo sprouting EC also exhibit an anterior polarization of these two proteins. Furthermore, caveolin-1 co-purifies with intermediate filaments, suggesting an interaction between caveolin-1 and IF. Vimentin-deficient SW13 cells exhibit a dramatically altered polarization of caveolin-1-GFP, which no longer accumulates in the protruding cell extension. In addition, the Tyr14 residue of caveolin-1 is required for co-purification of the protein with IF. Taken together, our results show that caveolin-1 Tyr14 is necessary for binding to intermediate filaments, which in turn is required for anterior polarization of caveolin-1 in transmigrating cells