No abstract

The insulin-like growth factor binding proteins (IGFBPs) have IGF-independent differential effects on cell function. We investigated whether they can affect integrin-receptor-mediated cell attachment to different extracellular matrix (ECM) components in Hs578T cells.Cell attachment to a general ECM gel was unaffected by IGFBP-1 and -6 but was significantly increased by IGFBP-4 and -5 and decreased by IGFBP-2 and -3. Similar results were obtained for attachment to laminin or collagen type IV. Attachment to fibronectin, however, was increased by IGFBP-3 and decreased by IGFBP-5. The actions of IGFBP-3 and -5 on cell attachment to ECM were lost in the presence of a soluble Arg-Gly-Asp (RGD)-containing fibronectin fragment. Thrombospondin reversed the actions of IGFBP-3 on cell attachment, but IGFBP-5 still increased cell attachment.On plastic, neither IGFBP-3 nor -5 alone affected cell viability; although ceramide-induced apoptosis was enhanced by IGFBP-3 but reduced by IGFBP-5. The presence of RGD reversed the action of IGFBP-5 on cell death but attenuated that of IGFBP-3. With cells grown on fibronectin, the action of IGFBP-3 was reversed, and it conferred cell survival, whereas the survival effect of IGFBP-5 was lost.In summary we have demonstrated that IGFBP-3 and -5 both have intrinsic effects on cell survival. In each case the presence of fibronectin or fibronectin fragments determines whether susceptibility to apoptosis is increased or decreased. These effects on cell survival are paralleled by acute effects on integrin receptor function; IGFBP-3 and -5 were able to either enhance or inhibit cell attachment in the presence of fibronectin. Cell survival is tightly controlled by cues from the ECM and from growth factors, particularly the IGFs. Our findings indicate that, in addition to being crucial modulators of IGF actions, the IGFBPs have direct actions on cell attachment and survival that are specific and dependent upon the matrix components present.

Matrix metalloproteinase-7 (MMP-7) is localized to epithelial cells and is up-regulated in many cancers and in inflammation. We now report that MMP-7 targets a key mesenchymal cell type, the myofibroblast. Recombinant MMP-7 stimulated the proliferation and migration of human colonic myofibroblasts. These responses were partly attributable to activation of other MMPs, notably MMP-3 and MMP-8, and to stimulation of the mitogen-activated protein kinase and phosphatidylinositol 3-kinase signaling pathways. Using a proteomic approach, we identified insulin-like growth factor binding protein-5 (IGFBP-5) as a previously unsuspected target of MMP-7 produced by colonic myofibroblasts. We present evidence that the MMP-7 cleavage of IGFBP-5 liberates IGF-II that functions as an autocrine myofibroblast growth factor. Thus, MMP-7 may act as a signal from epithelial cells for local recruitment of myofibroblasts and stimulation of their proliferation. Similar effects of MMP-7 produced in epithelial tumors might account for the expansion of stroma through activation of myofibroblasts. (Cancer Res 2005; 65(16): 7363-9)

IGF-binding protein (IGFBP)-3 is generally considered to have actions that counterbalance those of IGFs and is therefore being developed as a cancer treatment. In breast tumors, however, high levels are associated with aggressive tumors and poor prognosis. Consistent with this we have demonstrated that although IGFBP-3 and a non-IGF-binding fragment (serine phosphorylation domain peptide) reduced attachment and enhanced apoptosis of Hs578T breast cancer cells cultured on collagen or laminin, it promoted their attachment and survival on fibronectin, which is abundant in the matrix of aggressive tumors. We have now examined the factors that determine whether IGFBP-3 has positive or negative actions on breast epithelial cells. IGFBP-3 also promoted survival of Hs578T cells in the presence of an antibody to the beta1-integrin subunit or when cholesterol-stabilized complexes were disrupted. These actions were blocked by IGF-I or a MAPK inhibitor. Serine phosphorylation domain peptide had similar actions on MCF-7 cells that were again reversed on fibronectin or with disruption of cholesterol-stabilized complexes and blocked by the beta1-integrin antibody. In contrast, IGFBP-3 promoted growth and survival for nonmalignant MCF-10A cells, but these effects were again reversed on fibronectin and blocked by the beta1 antibody or a MAPK inhibitor or by disruption of cholesterol-stabilized complexes. On Hs578T cells, IGFBP-3 bound to caveolin-1 and beta1-integrins, enhancing their aggregation, the recruitment of focal adhesion kinase, and the activation of MAPK. In summary, with three breast epithelial cell lines, IGFBP-3 had positive or negative effects on growth and survival dependent upon the status of cholesterol-stabilized integrin receptor complexes.

Neuronal expression of SGK1 in aged human brain and its nuclear compartmentalization suggest a possible neuroprotective role. FOXO3a and NDRG1 data suggest augmented SGK1 activity (as reported for Akt) in severe AD. Increased intracellular SGK1 may complement enhanced Akt, with a distinct subcellular localization.

Chronic hypergastrinemia is associated with enterochromaffin-like (ECL) cell hyperplasia, which may progress to gastric carcinoid tumors. The latter consists of epithelial cells and stroma, and both compartments usually regress after normalization of hypergastrinemia. We previously showed that matrix metalloproteinase (MMP)-7 in gastric epithelial cells was upregulated by Helicobacter pylori and described MMP-7-dependent reciprocal signaling between the epithelium and a key stromal cell type, the myofibroblast. Here, we describe the regulation of gastric MMP-7 by gastrin and the potential significance for recruiting and maintaining myofibroblast populations. Biopsies of the gastric corpus and ECL cell carcinoid tumors were obtained from hypergastrinemic patients. Western blot analysis, ELISA, immunohistochemistry, and promoter-luciferase (luc) reporter assays were used to study MMP-7 expression. Gastric myofibroblasts were identified by alpha-smooth muscle actin (alpha-SMA) expression, and the effects of MMP-7 on myofibroblast proliferation were investigated. In hypergastrinemic patients, there was an increased abundance of MMP-7 and alpha-SMA in gastric corpus biopsies and ECL cell carcinoid tumors. In the latter, MMP-7 was localized to ECL cells but not stromal cells, which were nevertheless well represented. Gastrin stimulated MMP-7-luc expression in both AGS-G(R) and primary human gastric epithelial cells. Conditioned medium from gastrin-treated human gastric glands stimulated myofibroblast proliferation, which was inhibited by neutralizing antibodies to MMP-7. MMP-7 increased the proliferation of myofibroblasts via the MAPK and phosphatidylinositol 3-kinase (PI3K) pathways. In conclusion, stimulation of gastric MMP-7 by elevated plasma gastrin may activate epithelial-mesenchymal signaling pathways regulating myofibroblast function via MAPK and PI3K pathways and contribute to stromal deposition in ECL cell carcinoid tumors.

No abstract

{In addition to modulating insulin-like growth factors action, it is now clear that insulin-like growth factor-binding protein-3 also has intrinsic effects on cell growth and survival. We have compared the effects of insulin-like growth factor-binding protein-3 and transforming growth factor-beta on cell proliferation and death of Hs578T cells and the normal breast epithelial cell line, MCF-10A. The growth of MCF-10A cells was inhibited at low concentrations of insulin-like growth factor-binding protein-3 but stimulated at high concentrations. These differential effects were unaffected in the presence of an insulin-like growth factor-I receptor antagonist. A synthetic peptide corresponding to the serine phosphorylation domain of insulin-like growth factor-binding protein-3 (that does not bind to insulin-like growth factors) also mimicked these differential actions. The growth of both cell lines was significantly inhibited by transforming growth factor-beta, this was associated with a 14-fold increase of insulin-like growth factor-binding protein-3 secreted by the Hs578T cells but a five-fold decrease of insulin-like growth factorbinding protein-3 secreted by MCF-10A cells. Replacement doses of exogenous insulin-like growth factor-binding protein-3 overcame the transforming growth factor-beta-induced growth inhibition in the MCF-10A cells. Cell death induced by ceramide was significantly reduced by insulin-like growth factor-binding protein-3 in the MCF-10A cells and depleting insulinlike growth factor-binding protein-3 with transforming growth factor-beta in these cells consequently increased their susceptibility to ceramide. In contrast, insulin-like growth factor-binding protein-3 enhanced apoptosis induced by ceramide in the Hs578T cells but transforming growth factor-beta treated Hs578T cells were resistant to apoptosis. The addition of antisense mRNA to insulin-like growth factor-binding protein-3 significantly abrogated this effect of transforming growth factorbeta. These data indicate that insulin-like growth factor-binding protein-3 has intrinsic activity capable of inhibiting or enhancing the growth and survival of breast epithelial cells depending on the cell line and exposure to other cytokines.