The fibroblast growth factor-binding protein FGF-BP.

Fibroblast growth factors (FGFs) are important regulators of cell migration, proliferation and differentiation, e.g., during embryogenesis and wound healing, and under several pathological conditions including tumor growth and tumor angiogenesis. Since heparin-binding FGFs are tightly bound to heparansulfate proteoglycans, and therefore, trapped in the extracellular matrix, their release through the action of an FGF-binding protein (FGF-BP) is one of the critical steps in FGF bioactivation. FGF-BP expression is highly tissue specific and strictly regulated through different promoter elements. Besides its role in embryogenesis and wound healing, FGF-BP is upregulated in several tumors and it is associated especially with early stages of tumor formation, where angiogenesis plays a critical role. Concomitantly, in several mouse tumor models, targeting of FGF-BP by ribozymes or RNA interference (RNAi) abolishes or reduces tumor growth and tumor angiogenesis. This indicates that FGF-BP can be rate-limiting for tumor growth and serves as an angiogenic switch molecule, and that it represents an increasingly promising target molecule in anti-tumor therapy.

Inhibition of HER-2 by three independent targeting strategies increases paclitaxel resistance of SKOV-3 ovarian carcinoma cells.

Current treatment options for ovarian cancer, which is one of the most widespread gynecological malignancies, are limited, mainly because patients with advanced-stage disease often develop resistance to chemotherapeutics. In breast cancer cells, several studies suggest that overexpression of the human epidermal growth factor receptor-2 (HER-2) leads to increased resistance against certain, but not all cytotoxic drugs. In ovarian carcinoma, conflicting data on the correlation of HER-2 expression and tumor cell sensitivity exist. In this paper, we explore the role of HER-2 expression and signaling levels pertaining to paclitaxel (Taxol) chemoresistance by applying three different and independent strategies in SKOV-3 ovarian carcinoma cells. Firstly, we show that treatment with the HER-2 inhibitory antibody trastuzumab (Herceptin), which is well established in tumor therapy, results in markedly increased, rather than decreased, cellular paclitaxel resistance. Next, we present two newly developed low molecular weight inhibitors of HER-2 tyrosine kinase activity, D-69491 and D-70166. With both drugs, the decrease in cellular paclitaxel sensitivity upon HER-2 inhibition is confirmed. Finally, for more detailed analysis we stably downregulate HER-2 expression by ribozyme-targeting. Using clonal ribozyme-transfected SKOV-3 cells with different residual HER-2 levels, we establish a 'HER-2 gene dose effect' of paclitaxel cytotoxicity. We show that this effect is due to differential induction of apoptosis and differential cell cycle inhibition by paclitaxel. Finally, paclitaxel- or HER-2-mediated alterations in the phosphorylation of MAP kinases p42/44, Stress-activated protein kinase/Jun-terminal kinase (SAPK/JNK), and p38, and effects on the activation of caspase-3, caspase-7, and bcl-2 are discussed. We conclude that paclitaxel cytotoxicity in SKOV-3 cells is 'HER-2 dose-dependent' and identify cell proliferation as one underlying cellular event of this effect.

Cytotoxicity of the novel anti-cancer drug rViscumin depends on HER-2 levels in SKOV-3 cells.

rViscumin is a recombinant mistletoe lectin under clinical investigation as new anti-cancer drug. The relationship between oncogene, e.g., HER-2/neu (c-erbB2) receptor activation and tumor cell chemosensitivity, is of considerable importance to better predict the response to chemotherapy. Here, we analyze the cellular and molecular effects of HER-2 expression on rViscumin chemotoxicity in SKOV-3 cells. We show that selective depletion of HER-2 by ribozyme-targeting markedly decreases cellular sensitivity towards rViscumin. These findings are confirmed by treatment with the well-established inhibitory HER-2 antibody trastuzumab (Herceptin). Using clonal ribozyme-transfected cell lines, we establish a 'HER-2 gene dose' dependence of rViscumin cytotoxicity, which is due to differential induction of apoptosis and is not mediated by cell cycle alterations or altered cellular rViscumin binding/internalization. We further demonstrate an rViscumin-mediated, HER-2-dependent down-regulation of bcl-2 and the dose-dependent activation of members of the MAPK family, p42/44, SAPK/JNK, and p38, but not of caspases-3 and -7.