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Query: UMLS:C0178874 (tumor progression)
 40,807 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Overexpression and autocrine activation of the epidermal growth factor receptor (EGF-R) cause transformation of cultured cells and correlate with tumor progression in cancer patients. Dimerization and transphosphorylation are crucial events in the process by which receptors with tyrosine kinase activity generate normal and transforming cellular signals. Interruption of this process by inactive receptor mutants offers the potential to inhibit ligand-induced cellular responses. Using recombinant retroviruses, we have examined the effects of signalling-incompetent EGF-R mutants on the growth-promoting and transforming potential of ligand-activated, overexpressed wild-type EGF-R and the v-erbB oncogene product. Expression of a soluble extracellular EGF-R domain had little if any effect on the growth and transformation of NIH 3T3 cells by either tyrosine kinase. However, both a kinase-negative EGF-R point mutant (HERK721A) and an EGF-R lacking 533 C-terminal amino acids efficiently inhibited wild-type EGF-R-mediated, de novo DNA synthesis and cell transformation in a dose-dependent manner. Furthermore, coexpression with the v-erbBES4 oncogene product in NIH 3T3 cells resulted in transphosphorylation of the HERK721A mutant receptor and reduced soft-agar colony growth but had no effect in a focus formation assay. These results demonstrate that signalling-defective receptor tyrosine kinase mutants differentially interfere with oncogenic signals generated by either overexpressed EGF-R or the retroviral v-erbBES4 oncogene product.
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PMID:Anti-oncogenic activity of signalling-defective epidermal growth factor receptor mutants. 134 34

The HER2 protooncogene encodes a 185-kDa transmembrane protein (p185HER2) with extensive homology to the epidermal growth factor (EGF) receptor. Clinical and experimental evidence supports a role for overexpression of the HER2 protooncogene in the progression of human breast, ovarian, and non-small cell lung carcinoma. These data also support the hypothesis that p185HER2 present on the surface of overexpressing tumor cells may be a good target for receptor-targeted therapeutics. The anti-p185HER2 murine monoclonal antibody (muMAb) 4D5 is one of over 100 monoclonals that was derived following immunization of mice with cells overexpressing p185HER2. The monoclonal antibody is directed at the extracellular (ligand binding) domain of this receptor tyrosine kinase and presumably has its effect as a result of modulating receptor function. In vitro assays have shown that muMAb 4D5 can specifically inhibit the growth of tumor cells only when they overexpress the HER2 protooncogene. MuMAb 4D5 has also been shown to enhance the TNF-alpha sensitivity of breast tumor cells that overexpress this protooncogene. Relevant to its clinical application, muMAb 4D5 may enhance the sensitivity of p185HER2-overexpressing tumor cells to cisplatin, a chemotherapeutic drug often used in the treatment of ovarian cancer. In vivo assays with a nude mouse model have shown that the monoclonal antibody can localize at the tumor site and can inhibit the growth of human tumor xenografts which overexpress p185HER2. Modulation of p185HER2 activity by muMAb 4D5 can therefore reverse many of the properties associated with tumor progression mediated by this putative growth factor receptor. Together with the demonstrated activity of muMAb 4D5 in nude mouse models, these results support the clinical application of muMAb 4D5 for therapy of human cancers characterized by the overexpression of p185HER2.
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PMID:Monoclonal antibody therapy of human cancer: taking the HER2 protooncogene to the clinic. 167 63

Neuregulin, the putative ligand of the c-neu receptor tyrosine kinase, can induce differentiation or growth of epithelia and other cells. To gain insight into the biological role of this factor, we have analyzed the expression of neuregulin during mouse embryogenesis and in the perinatal animal by a combination of in situ hybridization and RNase protection experiments. We identify sites of expression that correspond to mesenchymal cells of various parenchymal organs. Our finding implies a function of neuregulin as a mesenchymal factor that acts on epithelia. The mesenchymal expression of neuregulin could thus provide a molecular basis for the biological phenomenon of mesenchymal-epithelial interactions. It also has implications on the molecular mechanism by which amplification of c-neu can affect tumor progression of carcinomas. In addition, neuregulin expression is found in neuronal cells during development. We show by RNase protection experiments that distinct isoforms of neuregulin are expressed in the brain. Therefore, our data indicate in vivo a dual role for neuregulin as mesenchymal and neuronal factor.
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PMID:Distinct isoforms of neuregulin are expressed in mesenchymal and neuronal cells during mouse development. 830 32

Scatter factor (SF), a secretory protein of fibroblasts, dissociates and increases the motility of epithelial cells and may be involved in cell migration processes during embryogenesis and tumor progression. Hepatocyte growth factor (HGF) is a potent mitogen for hepatocytes and other cells, and is thought to play a role in liver regeneration. We have presented structural and functional evidence that human SF and human HGF are identical proteins encoded by a single gene, since (i) no differences could be found by protein sequencing, by cDNA analysis, or by immunological comparison, and (ii) SF acts as a hepatocyte growth factor--i.e., stimulates DNA synthesis of primary hepatocytes and is a morphogen of kidney epithelial cells--whereas HGF exhibits SF activity--i.e., dissociates and induces invasiveness of various epithelial cells. Furthermore, there exists only one gene for human HGF-SF which is located on chromosome 7, bands q11.2-21 (Weidner et al., Proc. Natl. Acad. Sci. USA 88, 7001-7005, 1991). HGF-SF has been found to be the ligand of the c-met receptor tyrosine kinase (Naldini et al., EMBO J. 10, 2867-2878, 1991b). We have recently used transient expression of naturally occurring and in vitro mutagenized cDNAs of HGF-SF in order to delineate the protein domains necessary for biological activity and c-met receptor activation. (i) A single-chain HGF-SF resulting from the destruction of the protease cleavage site between heavy and light chain (Arg494 to Gln) was largely inactive, indicating that proteolytic cleavage is essential for acquisition of the biologically active conformation. (ii) A HGF-SF splice variant encoding a protein with a 5 amino acid deletion in the first kringle domain was as highly active as the wild type molecule. (iii) The separately expressed light chain (with serine protease homology) was inactive in all assays tested. (iv) The separate heavy chain as well as a naturally occurring splice variant consisting of the N-terminus and the first two kringle domains bound the met receptor, stimulated its tyrosine phosphorylation, and induced dissociation of epithelial cells but not mitogenesis. These data indicate that a functional domain in the N-terminal region and/or the first two kringle domains of HGF-SF is sufficient for binding to and activation of the met receptor (Hartmann et al., Proc. Natl. Acad. Sci. USA, in press).
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PMID:Molecular characteristics of HGF-SF and its role in cell motility and invasion. 838 Jul 39

Arteriovenous malformations (AVMs) are congenital lesions composed of abnormal vasculature, with no capillary component, and are clinically significant due to their tendency to spontaneously hemorrhage. The mechanisms regulating the genesis and progression of these lesions are unknown. In order to study the role of angiogenesis in AVMs, we have analyzed the expression of the endothelial cell mitogen vascular endothelial growth factor (VEGF) and a novel endothelial cell-specific receptor tyrosine kinase, Tie, by in situ hybridization and immunohistochemistry in these malformations and surrounding brain tissue. We have previously shown upregulation of Tie accompanying wound healing and tumor progression. In this study, we demonstrate significantly elevated levels of Tie mRNA and protein in AVM and surrounding brain vasculature. Upregulation of VEGF mRNA was observed in the cells of brain parenchyma adjacent to the AVM, and VEGF protein was detected in this tissue as well as in AVM endothelia. Normal brain, in comparison, expressed little or no Tie or VEGF. The significant upregulation of VEGF and Tie in AVMs may indicate some ongoing angiogenesis, possibly contributing to the slow growth and maintenance of the AVM, and could be of potential use in the therapeutic targeting of these lesions.
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PMID:Tie endothelial cell-specific receptor tyrosine kinase is upregulated in the vasculature of arteriovenous malformations. 893 95

Xiphophorus fish have been the subject of intensive genetic research for more than 60 yr, primarily because of the availability of a number of interspecific hybrids that are malignant melanoma models with apparently simple oncogene and tumor suppressor gene determinants. The gene map of Xiphophorus is one of the most extensive among nonhuman vertebrates, with about 100 genes assigned to at least 20 independently assorting linkage groups (LGs), as well as more than 250 anonymous DNA sequence markers, providing coverage for most of the genome for genetic mapping studies. This characteristic has resulted in the mapping of a tumor suppressor locus, DIFF, which is one of two genetic determinants of melanoma formation in the best-studied hybrid melanoma, the Gordon-Kosswig melanoma model. The other gene responsible for melanoma formation in this model is a sex-linked tyrosine kinase gene related to EGFR and called Xiphophorus melanoma receptor kinase (Xmrk). The cellular oncogene homologues of the non-receptor tyrosine kinase family orthologous toyes and fyn have also been found to be overexpressed in malignant melanomas of Xiphophorus and may be involved in tumor progression. We report here the map location of a Xiphophorus yes gene, YES1, in LG VI, closest to the EGFR gene and the assignment of a fyn gene homologue to newly designated LG XV, linked to the gene for cytosolic alpha-galactosidase. We also confirmed that an EGFR-related sequence (EGFRL1) that we previously assigned to Xiphophorus LG VI by cross-hybridization to a viral erbB probe was the EGFR orthologue. Our results suggest that the presence of expressed duplicates of members of the tyrosine kinase gene family in teleost fishes may increase the potential number of targets in oncogenic cascades in fish tumor models.
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PMID:Mapping of tyrosine kinase gene family members in a Xiphophorus melanoma model. 968 40

CD44 has been implicated in tumor progression and metastasis, but the mechanism(s) involved is as yet poorly understood. Recent studies have shown that CD44 isoforms containing the alternatively spliced exon v3 carry heparan sulfate side chains and are able to bind heparin-binding growth factors. In the present study, we have explored the possibility of a physical and functional interaction between CD44 and hepatocyte growth factor/scatter factor (HGF/SF), the ligand of the receptor tyrosine kinase c-Met. The HGF/SF-c-Met pathway mediates cell growth and motility and has been implicated in tumor invasion and metastasis. We demonstrate that a CD44v3 splice variant efficiently binds HGF/SF via its heparan sulfate side chain. To address the functional relevance of this interaction, Namalwa Burkitt's lymphoma cells were stably co-transfected with c-Met and either CD44v3 or the isoform CD44s, which lacks heparan sulfate. We show that, as compared with CD44s, CD44v3 promotes: (i) HGF/SF-induced phosphorylation of c-Met, (ii) phosphorylation of several downstream proteins, and (iii) activation of the MAP kinases ERK1 and -2. By heparitinase treatment and the use of a mutant HGF/SF with greatly decreased affinity for heparan sulfate, we show that the enhancement of c-Met signal transduction induced by CD44v3 was critically dependent on heparan sulfate moieties. Our results identify heparan sulfate-modified CD44 (CD44-HS) as a functional co-receptor for HGF/SF which promotes signaling through the receptor tyrosine kinase c-Met, presumably by concentrating and presenting HGF/SF. As both CD44-HS and c-Met are overexpressed on several types of tumors, we propose that the observed functional collaboration might be instrumental in promoting tumor growth and metastasis.
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PMID:Heparan sulfate-modified CD44 promotes hepatocyte growth factor/scatter factor-induced signal transduction through the receptor tyrosine kinase c-Met. 1003 43

Hepatocyte growth factor (HGF) is a multifunctional cytokine which is believed to have important roles in tissue development and regeneration, and tumor progression. It is indistinguishable from scatter factor (SF), a motility factor. HGF/SF is believed to be a mesenchymal cell-derived cytokine acting for epithelial cells bearing its receptor tyrosine kinase, c-Met. Recently, we found that glioblastoma multiforme (GBM), a highly malignant brain tumor of astrocytic origin, concomitantly express HGF/SF and c-Met. This finding indicates a presence of autocrine loop of HGF/SF signaling pathway in GBM. Moreover, GBM cells also co-express HGF activator, a recently identified serine proteinase having efficient HGF/SF activating activity. The expression of HGF/SF and c-Met was low or hardly detectable in low-grade astrocytoma, and c-Met immunoreactivity was correlated with the histological grade of the tumor suggesting that the creation of HGF/SF autocrine loop occurs along with the progression of astrocytic brain tumors. Experimental evidence indicated that HGF/SF exhibits potent migration/invasion-inducing activity for GBM cells bearing c-Met receptor. It is also a significant angiogenesis factor in GBM, and may serve as a cellular growth factor for certain GBM cells. These lines of evidence suggest that HGF/SF signaling pathway may serve as a promising new target of therapeutic intervention of GBM.
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PMID:Expression of hepatocyte growth factor/scatter factor and its receptor c-Met in brain tumors: evidence for a role in progression of astrocytic tumors (Review). 1020 87

Prostate cancer is an androgen-dependent tumor which presents an androgen-independent regrowth after clinical regression in response to antiandrogen treatment. Four hypotheses have been developed to understand how androgen signal transduction pathway mediate androgen-independent tumor progression: over expression of the wild-type androgen-receptor gene, androgen-receptor gene mutation, excessive recruitment of transcriptional co-activator ARA-70 and a cross-talk between the androgen-receptor and the growth factor receptor pathways. In this work, C. Sawyers's group elegantly demonstrates, in LAPC-4 androgen-independent prostate cancer sublines, that forced hyperexpression of HER-2/Neu receptor tyrosine kinase allowed androgen-independent growth, that HER-2/Neu activated the androgen-receptor pathway in the absence of androgens and synergized with low levels of androgen to superactivate the pathway. These important data could have therapeutic implications for the management of androgen-independent prostate cancer.
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PMID:[Androgen-independent prostate carcinoma and androgen-receptor: recent progress in molecular genetics]. 1047 78

During past decades, knowledge of melanoma biology has increased considerably. Numerous therapeutic modalities based on this knowledge are currently under investigation. Advanced melanoma, nevertheless, remains a prime example of poor treatment response that may, in part, be the consequence of activated N-Ras oncoproteins. Besides oncogenic Ras, wild-type Ras gene products also play a key role in receptor tyrosine kinase growth factor signaling, known to be of importance in oncogenesis and tumor progression of a variety of human neoplasms, including malignant melanoma; therefore, it is reasonable to speculate that a pharmacological approach that curtails Ras activity may represent a sensible approach to inhibit melanoma growth. To test this concept, the antitumor activity of S-trans, trans-farnesylthiosalicylic acid (FTS), a recently discovered Ras antagonist that dislodges Ras from its membrane-anchoring sites, was evaluated. The antitumor activity of FTS was assessed both in vitro and in vivo in two independent SCID mouse xenotransplantation models of human melanoma expressing either wild-type Ras (cell line 518A2) or activated Ras (cell line 607B). We show that FTS (5-50 microM) reduces the amounts of activated N-Ras and wild-type Ras isoforms both in human melanoma cells and Rat-1 fibroblasts, interrupts the Ras-dependent extracellular signal-regulated kinase in melanoma cells, inhibits the growth of N-Ras-transformed fibroblasts and human melanoma cells in vitro and reverses their transformed phenotype. FTS also causes a profound and statistically significant inhibition of 518A2 (82%) and 607B (90%) human melanoma growth in SCID mice without evidence of drug-related toxicity. Our findings stress the notion that FTS may qualify as a novel and rational treatment approach for human melanoma and possibly other tumors that either carry activated ras genes or rely on Ras signal transduction more heavily than nonmalignant cells.
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PMID:Novel Ras antagonist blocks human melanoma growth. 1057 Jan 91


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