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Query: UMLS:C0027627 (metastases)
 103,950 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The ErbB2 receptor tyrosine kinase is often overexpressed in human malignancies and causally involved in transformation. High levels of ErbB2 in tumor cells correlate with an unfavorable prognosis. This makes the ErbB2 receptor an interesting target for tumor therapy, and several strategies have been designed to direct drugs to ErbB2-expressing cells. We established a novel cellular model that allows preclinical evaluation of ErbB2-directed drugs in immunocompetent animals. Renal carcinoma (Renca) cells are an established tumor cell line that originated in Balb/c mice. Upon intravenous transplantation, these cells form pulmonary metastases in Balb/c mice. The transforming genetic lesions in these cells are not fully characterized, but do not seem to involve alterations in ErbB2 gene expression. We transfected Renca cells with the gene encoding the human ErbB2 receptor to provide a target structure for specific drugs and with the bacterial lacZ gene to provide a sensitive means of detection of the tumor cells in the transplanted animals. These genetically modified cells form lung metastasis and can be easily visualized on the surface of lung tissue by staining with an X-gal solution. This allows a quantitative analysis of the number of ErbB2-expressing pulmonary metastasis. We previously used these Renca cells to evaluate the efficacy of an ErbB2-specific tumor toxin on pulmonary metastases in an adjuvant and a palliative treatment setting. In both cases, we achieved a dramatic reduction of disseminated lung lesions. Here we show that even at an advanced stage of metastasis formation, the ErbB2-specific toxin is able to efficiently reduce the number of pulmonary tumors.
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PMID:A novel animal model for the evaluation of the efficacy of drugs directed against the ErbB2 receptor on metastasis formation. 1021 91

Mutations of the RET gene, encoding a receptor tyrosine kinase, have been associated with the inherited cancer syndromes MEN 2A and MEN 2B. They have also further been associated with both familial and sporadic medullary thyroid carcinomas. Missense mutations affecting cysteine residues within the extracellular domain of the receptor causes constitutive tyrosine kinase activation through the formation of disulfide-bonded homodimers. We have recently reported that a somatic 6 bp in-frame deletion, originally coding for Glu632-Leu633, potently activates the RET gene. This activation is increased with respect to the frequent MEN 2A-associated missense mutation Cys634Arg. This finding specifically correlated to the clinic behavior of the corresponding tumor, which was characterized by an unusually aggressive progression with both multiple and recurrent metastases. By examining the possibility that this deletion acts in a manner similar to cysteine substitution, we have analysed the molecular mechanism by which this oncogenic activation occurs. Phosphorylated dimers of the deleted Ret receptor were detected in immunoprecipitates separated under non-reducing conditions. Like other Cys point mutations, this 6 bp deletion affecting two amino acid residues between two adjacent Cys, is capable of activating the transforming ability of Ret by promoting receptor dimerization. These results suggest that alteration to cysteine residue position or pairing is capable of inducing ligand independent dimerization. Furthermore, we present data demonstrating that the processing and sorting of the Ret membrane receptor to the cell surface is affected by mutation type.
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PMID:The Glu632-Leu633 deletion in cysteine rich domain of Ret induces constitutive dimerization and alters the processing of the receptor protein. 1049 Aug 16

In recent years developmental biology has contributed a great deal to cancer research. This is in part because both fields address the question of how genes control the three-dimensional organisation of tissues, and how mutation of genes alters this. But also in recent years, the discovery that signalling pathways are conserved from worms to man, combined with the power of developmental biology's model organisms, principally Drosophila and C. elegans, to reveal signalling pathways that control tissue growth and organisation, has had a huge impact. Examples of this are the subject of the reviews in this issue, including the EGF-receptor, Wnt/APC/catenin, TGF-beta/Smad and hedgehog/patched/smoothened pathways, all of which were discovered and/or pieced together in model organisms, and all of which are disrupted by mutation in human cancer. Other topics considered are the control and execution of apoptosis; the search for tumour-suppressor-like genes in Drosophila; and genes of the Polycomb and Trithorax Groups that regulate the commitment of cells to patterns of differentiation, and that are among the targets for chromosome translocations. These stories illustrate how developmental biology has shown that there are many more signalling pathways relevant to neoplasia than the receptor tyrosine kinase pathways that first dominated the field; and that the signalling is more than just mitogenic or anti-mitogenic, and should be viewed as providing cells with information about their position and neighbours, that determines their role, differentiation and behaviour.
Cancer Metastasis Rev 1999
PMID:The impact of developmental biology on cancer research: an overview. 1072 82

The growth of human tumors and development of metastases depend on the de novo formation of blood vessels. The formation of new blood vessels is tightly regulated by specific growth factors that target receptor tyrosine kinases (RTKs). Vascular endothelial growth factor (VEGF) and the Flk-1/KDR RTK have been implicated as the key endothelial cell-specific factor signaling pathway required for pathological angiogenesis, including tumor neovascularization. Inhibition of the VEGF tyrosine kinase signaling pathway blocks new blood vessel formation in growing tumors, leading to stasis or regression of tumor growth. Advances in understanding the biology of angiogenesis have led to the development of several therapeutic modalities for the inhibition of the VEGF tyrosine kinase signaling pathway. A number of these modalities are under investigation in clinical studies to evaluate their potential to treat human cancers.
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PMID:VEGF receptor signaling in tumor angiogenesis. 1080 84

Evidence suggests that there is an association between the abnormal expression of members of the c-erbB receptor tyrosine kinase family and poor prognosis in head and neck squamous cell carcinomas (HNSCC). Until now, the relative contributions of different c-erbB ligands to HNSCC progression have not been clearly defined. In this paper we examined the effects of ligands with different c-erbB receptor specificities in terms of their stimulation of HNSCC proliferation, expression of matrix metalloproteinases (MMPs) and invasion. Heregulin-beta1 (HRG-beta1; selective c-erbB3/B4 ligand) was found to stimulate proliferation in the majority of cell lines, whereas epidermal growth factor (EGF; EGFR ligand) and betacellulin (BTC; EGFR/B4 ligand) induced variable responses. All three ligands up-regulated multiple MMPs including collagenases, stromelysins, matrilysin and gelatinase B (MMP-9) but had minimal or no effects on gelatinase A (MMP-2), MT1-MMP and tissue inhibitors of MMPs (TIMPs). MMP-9 mRNA was induced to a higher level than other MMPs, although with slower kinetics. HRG-beta1 was less active than EGF and BTC at the optimal concentration (relative potency of EGF:BTC:HRG = 3:4:1). In vitro invasion through Matrigel was also increased by all three ligands in proportion to their MMP up-regulation. A specific anti-EGFR monoclonal antibody (mAb ICR62) inhibited MMP up-regulation, migration and invasion induced by all three ligands, whereas an anti-c-erbB-2 mAb ICR12 inhibited mitogenic and motogenic responses following ligand stimulation but had no effect on MMP expression. These results suggest that c-erbB ligands may differentially potentiate the invasive phenotype of HNSCC via co-operative induction of cell proliferation, migration and proteolysis. The EGFR signalling pathway appears to be the dominant component controlling the proteolytic and invasive phenotype in HNSCC, whereas the c-erbB-2 signalling pathway is responsible, in part, for the mitogenic and motogenic effects of ligands.
Clin Exp Metastasis 1999
PMID:Differential modulation of proliferation, matrix metalloproteinase expression and invasion of human head and neck squamous carcinoma cells by c-erbB ligands. 1084 63

The RET proto-oncogene encodes a receptor tyrosine kinase for transforming growth factor-beta-related neurotrophic factors, which include GDNF and neurturin. The expression of RET proto-oncogene was detected in several tissues, such as spleen, thymus, lymph nodes, salivary gland, and spinal cord, and in several neural crest-derived cell lines. RET expression in the thyroid gland was reported to be restricted to neural crest-derived C cells. The presence of RET mRNA or protein has not yet been reported in thyroid follicular cells. We previously demonstrated the expression of oncogenic rearranged versions of RET in papillary thyroid carcinomas: tumors derived from thyroid follicular cells. To assess the expression of the normal RET proto-oncogene in follicular cells, we analyzed its expression in a panel of neoplasias originating from thyroid follicular epithelial cells: papillary carcinomas and both follicular adenomas and carcinomas. We also demonstrated the presence of RET normal transcripts in two follicular thyroid carcinoma lymph node metastases. Moreover, we found the presence of the RET/ELE1 transcript, the reciprocal complementary form of the oncogenic fusion transcript ELE1/RET, in a papillary thyroid carcinoma specimen expressing the RET/PTC3 oncogene, thus demonstrating that the RET promoter is active in those cells after rearrangement. Finally, we show that in a papillary carcinoma-derived cell line expressing the proto-RET receptor and the related GFRalpha2 co-receptor, GDNF treatment induced RET tyrosine phosphorylation and subsequent signal transduction pathway, indicating that RET could be active in thyroid follicular cells.
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PMID:RET receptor expression in thyroid follicular epithelial cell-derived tumors. 1085 Apr 26

In colorectal cancer patients, prognosis is not determined by the primary tumor but by the formation of distant metastases. Molecules that have been implicated in the metastatic process are the proto-oncogene product c-Met and CD44 glycoproteins. Recently, we obtained evidence for functional collaboration between these two molecules: CD44 isoforms decorated with heparan sulfate chains (CD44-HS) can bind the c-Met ligand, the growth and motility factor hepatocyte growth factor/scatter factor (HGF/SF). This interaction strongly promotes signaling through the receptor tyrosine kinase c-Met. In the present study, we explored the expression of CD44-HS, c-Met, and HGF/SF in the normal human colon mucosa, and in colorectal adenomas and carcinomas, as well as their interaction in colorectal cancer cell lines. Compared to the normal colon, CD44v3 isoforms, which contain a site for HS attachment, and c-Met, were both overexpressed on the neoplastic epithelium of colorectal adenomas and on most carcinomas. Likewise, HGF/SF was expressed at increased levels in tumor tissue. On all tested colorectal cancer cell lines CD44v3 and c-Met were co-expressed. As was shown by immunoprecipitation and Western blotting, CD44 on these cells lines was decorated with HS. Interaction with HS moieties on colorectal carcinoma (HT29) cells promoted HGF/SF-induced activation of c-Met and of the Ras-MAP kinase pathway. Interestingly, survival analysis showed that CD44-HS expression predicts unfavorable prognosis in patients with invasive colorectal carcinomas. Taken together, our findings indicate that CD44-HS, c-Met, and HGF/SF are simultaneously overexpressed in colorectal cancer and that HS moieties promote c-Met signaling in colon carcinoma cells. These observations suggest that collaboration between CD44-HS and the c-Met signaling pathway may play an important role in colorectal tumorigenesis.
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PMID:Expression of c-Met and heparan-sulfate proteoglycan forms of CD44 in colorectal cancer. 1107 15

Growth and metastasis of solid tumors depend on the formation of new blood vessels which originate from the existing vascular system. These blood vessels grow into the tumor and thus provide the necessary nutrients and growth factors for tumor progression. At the same time, the newly formed blood vessels allow tumor cells to disseminate and form metastases in distant organs. Normally, vascular homeostasis is regulated by a balance of angiogenic and antiangiogenic mechanisms. Tumor-induced angiogenesis is mainly sustained by the production and secretion of angiogenic factors originating from tumor and stroma cells. The most prominent angiogenic factor is the vascular endothelial growth factor (VEGF). Recently, additional angiogenic factors and their respective receptors have been identified and related to tumor angiogenesis. Among these, the angiopoietins and their receptor TIE-2 have been investigated to some detail. Angiopoietin-1 which binds to and activates TIE-2 is obviously responsible for the stabilization of vessels under homeostatic conditions. Angiopoietin-2 binds to the same receptor as angiopoietin-1 but is antagonistic with respect to angiopoietin-1. It destabilizes blood vessels and, under appropriate conditions, induces complete regression. In the similar situation angiopoietin-2 induces the destabilization of blood vessels, and the angiogenic factor VEGF produced by the tumor induces the massive formation of new vessels. When human melanoma cells A375 are stably transfected to produce the soluble variant of the angiopoietin receptor TIE-2 (sTIE-2), they show a substantial inhibition of tumor growth on nude mice. Similar effects have been seen with the soluble variant of the VEGF receptor FLT-1 (sFLT-1). In both cases, the vessel density of the tumors is significantly reduced. These experiments show that the inhibition of the angiopoietin/TIE-2 system, similar to the inhibition of the VEGF/VEGF receptor system, has an antitumoral effect, most probably due to the inhibition of tumor angiogenesis. Thus, inhibition of both signalling systems seem to be a valid strategy for the development of novel antiangiogenic therapies. Recently, the inhibition of the VEGF receptor tyrosine kinase by the compound PTK787/ZK222584 has been shown to substantially inhibit tumor growth and metastases formation. This compound has now entered clinical trials at the Tumor Biology Center in Freiburg i.Br. A preliminary evaluation of phase I study shows a very promising clinical outcome.
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PMID:[Tumor angiogenesis: new approaches to cancer therapy]. 1144 5

The ultimate target of anti-angiogenic drugs is the genetically stable, activated endothelial cell of a newly forming tumor blood vessel, rather than the genetically unstable tumor cell population per se. This led to the notion that acquired resistance to such drugs may not develop as readily, if at all. While there is some evidence that this lack of resistance development may be the case for some direct-acting angiogenesis inhibitors, it is becoming apparent that resistance can develop over time to many types of angiogenesis inhibitors including, possibly, some direct inhibitors, especially when used as monotherapies. Possible mechanisms for such acquired or induced resistance include: (i) redundancy of pro-angiogenic growth factors when the drug used targets a single such growth factor or its cognate endothelial cell-associated receptor tyrosine kinase; (ii) the anti-apoptotic/pro-survival function of growth factors such as VEGF, which, in high local concentrations, can antagonize the pro-apoptotic effects of various angiogenesis inhibitors; (iii) epigenetic, transient upregulation, or induction, of various anti-apoptotic effector molecules in host-endothelial cells; and (iv) heterogeneous vascular dependence of tumor cell populations. It is suggested that long-term disease control with anti-angiogenic drugs can be best achieved by judicious combination therapy. In this regard, the great molecular diversity of anti-angiogenic drug targets, in contrast to chemotherapy, makes this a particularly attractive therapeutic option, especially when approved, commercially available drugs considered to have anti-angiogenic effects are used in such combination treatment strategies.
Cancer Metastasis Rev 2001
PMID:Possible mechanisms of acquired resistance to anti-angiogenic drugs: implications for the use of combination therapy approaches. 1183 51

The vascular endothelial growth factor (VEGF) receptor fetal liver kinase 1 (flk1; VEGFR-2, KDR) is an endothelial cell-specific receptor tyrosine kinase that mediates physiological and pathological angiogenesis. We hypothesized that an active immunotherapy approach targeting flk1 may inhibit tumor angiogenesis and metastasis. To test this hypothesis, we first evaluated whether immune responses to flk1 could be elicited in mice by immunization with dendritic cells pulsed with a soluble flk1 protein (DC-flk1). This immunization generated flk1-specific neutralizing antibody and CD8+ cytotoxic T cell responses, breaking tolerance to self-flk1 antigen. Tumor-induced angiogenesis was suppressed in immunized mice as measured in an alginate bead assay. Development of pulmonary metastases was strongly inhibited in DC-flk1-immunized mice challenged with B16 melanoma or Lewis lung carcinoma cells. DC-flk1 immunization also significantly prolonged the survival of mice challenged with Lewis lung tumors. Thus, an active immunization strategy that targets an angiogenesis-related antigen on endothelium can inhibit angiogenesis and may be a useful approach for treating angiogenesis-related diseases.
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PMID:Active immunization against the vascular endothelial growth factor receptor flk1 inhibits tumor angiogenesis and metastasis. 1207 Feb 85


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