By comparing differential gene expression in the insulin-like growth factor (IGF)-IR null cell fibroblast cell line (R؊ cells) with cells overexpressing the IGF-IR (R؉ cells), we identified the INTRODUCTIONInsulin-like growth factor (IGF)-I and IGF-II are ligands for the widely expressed IGF-I receptor tyrosine kinase, which promotes mitogenesis and cell survival (reviewed in Adams et al., 2000). The IGF-IR is essential for normal growth during embryonic development and promotes cell survival and migration. Circulating IGFs and the IGF-IR signaling pathways also have been associated with cancer progression (reviewed in LeRoith and Roberts, 2003). In a mouse model of pancreatic islet cell tumorigenesis, endogenous IGF-IR expression was up-regulated at invasive regions of the tumors, and ectopic IGF-IR expression resulted in the accelerated development of highly invasive and metastatic carcinomas (Lopez and Hanahan, 2002). Conversely, the suppression of IGF-IR expression by antisense strategies (Resnicoff, 1998) or blocking antibodies results in decreased tumor growth and decreased metastatic capacity in tumor cell models (Maloney et al., 2003). Signals from the IGF-IR associated with survival, tumorigenicity, and metastasis are associated with the C terminus of the receptor (O'Connor et al., 1997;Brodt et al., 2001;Baserga et al., 2003).Cell migration and invasion are complex processes that require the coordination of signals from both adhesion and growth factor receptors. Signals from the IGF-IR can interact with those from integrins to initiate the formation of signaling complexes necessary for the formation and disassembly of cell adhesions with the extracellular matrix (ECM) (Doerr and Jones, 1996;Brooks et al., 1997). These signals involve enhancement of Shc phosphorylation (Mauro et al., 1999;Jackson et al., 2000;Kim et al., 2004), regulation of focal adhesion kinase phosphorylation at focal adhesions (Manes et al., 1999), differential regulation of signals by scaffolding proteins such as RACK1 (Hermanto et al., 2002;Kiely et al., 2002), signals from reorganization of the cytoskeleton (Casamassima and Rozengurt, 1998;Kim and Feldman, 1998;Guvakova et al., 2002), expression of angiogenic and invasive factors , regulation of cadherin location (Playford et al., 2000;Pennisi et al., 2002), and transactivation of the epidermal growth factor (EGF) receptor (Burgaud and Baserga, 1996;Roudabush et al., 2000). How all of these events are coordinated during cell migration or invasion, or how some of these signals are enhanced in metastatic cancer, is still poorly understood.IGF-I induces expression of several genes that promote cell migration and cancer progression, including ␤-catenin (Playford et al., 2000), the cadherin complex protein ZO-1 (Mauro et al., 2001), the angiogenic factor vascular endothelial growth factor (Miele et al., 2000), the metalloprotease MT1 MMP , and heparin-binding EGF-like growth factor (Mulligan et al., 2002 refractory to cellular transformation by several oncogenes (Sell et al., 1994), ...

Various anticancer drugs cause mitochondrial perturbations in association with apoptosis. Here we investigated the involvement of caspase-and Bcl-2-dependent pathways in doxorubicin-induced mitochondrial perturbations and apoptosis. For this purpose, we set up a novel three-color flow cytometric assay using rhodamine 123, annexin V-allophycocyanin, and propidium iodide to assess the involvement of the mitochondria in apoptosis caused by doxorubicin in the breast cancer cell line MTLn3. Doxorubicin-induced apoptosis was preceded by up-regulation of CD95 and CD95L and a collapse of mitochondrial membrane potential (⌬) occurring prior to phosphatidylserine externalization. This drop in ⌬ was independent of caspase activity, since benzyloxycarbonyl-Val-Ala-DL-Asp-fluoromethylketone did not inhibit it. Benzyloxycarbonyl-Val-Ala-DLAsp-fluoromethylketone also blocked activation of caspase-8, thus excluding an involvement of the death receptor pathway in ⌬ dissipation. Furthermore, although overexpression of Bcl-2 in MTLn3 cells inhibited apoptosis, dissipation of ⌬ was still observed. No decrease in ⌬ was observed in cells undergoing etoposide-induced apoptosis. Immunofluorescent analysis of ⌬ and cytochrome c localization on a cell-to-cell basis indicates that the collapse of ⌬ and cytochrome c release are mutually independent in both normal and Bcl-2-overexpressing cells. Together, these data indicate that doxorubicin-induced dissipation of the mitochondrial membrane potential precedes phosphatidylserine externalization and is independent of a caspase-or Bcl-2-controlled checkpoint.

PDLIM2 integrates cytoskeletal signaling with gene expression to enable reversible differentiation of epithelial cancer cells. PDLIM2 associates with the COP9 signalosome and controls its nuclear translocation and the stability of key transcription factors necessary for either a mesenchymal or an epithelial phenotype.

Abstract-LDL is known to increase the sensitivity of human platelets for agonists and to induce aggregation and secretion independently at high concentrations, but its mechanism of action is largely obscure. To clarify how LDL increases platelet sensitivity, cells were incubated in lipoprotein-poor plasma and treated with collagen at a concentration that induced Ϸ20% secretion of 14 C-serotonin. Preincubation with LDL (30 minutes at 37°C) enhanced secretion in a dose-dependent manner to 60Ϯ14% at a concentration of 2 g LDL protein/L. Similar stimulation by LDL was seen when secretion was induced by the thrombin receptor-activating peptide. This enhancement was strongly reduced (1)