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Query: UMLS:C0006142 (breast cancer)
 160,383 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We previously demonstrated that antiestrogen 4-hydroxytamoxifen (OH-Tam) blocks the mitogenic activity of growth factors in breast cancer. We now investigate this mechanism by evaluating how OH-Tam affects growth factor binding and receptor tyrosine kinase activity. We show here that OH-Tam has an opposite effect on epidermal growth factor (EGF) and insulin-like growth factor-1 (IGF-1) binding in estrogen receptor (ER) positive cells. A decrease in IGF-1 binding sites may explain the reduced IGF-I mitogenic effect, whereas an increase in high affinity EGF binding associated with a decrease in in vitro receptor autophosphorylation rather favors the possibility of an alteration in EGF receptor tyrosine kinase activity. We conclude that OH-Tam may prevent growth factor action in ER+ cells both by modulating the concentration of growth factor binding sites and by altering growth factor receptor functionality.
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PMID:Mechanisms of 4-hydroxytamoxifen anti-growth factor activity in breast cancer cells: alterations of growth factor receptor binding sites and tyrosine kinase activity. 226 52

The use of Schwann cell (SC) autotransplantation to influence neural repair in humans is dependent upon identifying mitogens that will effectively expand human Schwann cells (SCs) in culture. The recent purification and molecular cloning of glial growth factor (GGF), a potent mitogen for rat Schwann cells, has led to the recognition that a family of proteins (GGF/HRG/NDF/ARIA) are alternatively spliced products of a single gene. The heregulins (HRGs) have been characterized with respect to their influence on human breast cancer cell lines; here we examined whether the HRGs have mitogenic activity for human SCs. Using DNA synthesis assays and serial passaging of cells in culture, we demonstrate that HRG is an effective mitogen for human SCs and that, in the presence of agents that elevate cAMP, it is possible to expand these cells over multiple passages without overwhelming fibroblast contamination. One putative target for this family of proteins is p185erbB2, and EGF-like receptor tyrosine kinase that is encoded by the erbB2 protooncogene. In this report we also demonstrate that the erbB2/3/4 messages as well as the erbB2/3 receptor proteins are present within cultured human SCs. The addition of HRG to human SCs results in tyrosine phosphorylation of a 185 kDa protein. In the presence of stimulatory concentrations of HRG, a blocking monoclonal antibody (2C4) to p185erbB2 is capable of significantly inhibiting phosphorylation of a 185 kDa protein as well as the subsequent incorporation of 3H-thymidine within the human SC. These latter results implicate an important role for p185erbB2 in mediating the mitogenic response of human SCs to HRGs.
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PMID:The influence of heregulins on human Schwann cell proliferation. 786 1

Amplification of the Neu/c-erbB-2 receptor tyrosine kinase has been implicated as an important event in the genesis of human breast cancer. Indeed, transgenic mice bearing either an activated form of neu or the wild-type proto-oncogene under the transcriptional control of the mouse mammary tumor virus promoter-enhancer frequently develop mammary carcinomas (L. Bouchard, L. Lamarre, P. J. Tremblay, and P. Jolicoeur, Cell 57:931-936, 1989; C. T. Guy, M. A. Webster, M. Schaller, T. J. Parson, R. D. Cardiff, and W. J. Muller, Proc. Natl. Acad. Sci. USA 89:10578-10582, 1992; W. J. Muller, E. Sinn, R. Wallace, P. K. Pattengale, and P. Leder, Cell 54:105-115, 1988). Induction of mammary tumors in transgenic mice expressing the wild-type Neu receptor is associated with activation of the receptor's intrinsic tyrosine kinase activity (Guy et al., Proc. Natl. Acad. Sci. USA 89:10578-10582, 1992). Here, we demonstrate that activation of Neu in these transgenic mice occurs through somatic mutations located within the transgene itself. Sequence analyses of these mutations revealed that they contain in-frame deletions of 7 to 12 amino acids in the extracellular region proximal to the transmembrane domain. Introduction of these mutations into a wild-type neu cDNA results in an increased transforming ability of the altered Neu tyrosine kinase. These observations suggest that oncogenic activation of Neu in mammary tumorigenesis frequently occurs by somatic mutation.
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PMID:Novel activating mutations in the neu proto-oncogene involved in induction of mammary tumors. 793 22

The c-erbB-2 proto-oncogene encodes a receptor tyrosine kinase (RTK) closely related to the epidermal growth factor receptor (EGFR). Overexpression of erbB-2 occurs in approximately 20% of human breast tumours, where increased expression correlates with poor patient prognosis. The EGFR is coupled to the Ras signalling pathway by interaction with the adaptor protein Grb2, and Sos, a Ras GDP-GTP exchange factor. In this study, activation of the erbB-2 receptor and its association with Grb2 and Sos was investigated in breast cancer cell lines which overexpress erbB-2. The receptor was found to be tyrosine phosphorylated in all cell lines in which it is overexpressed. Western blotting of Grb2 and Sos immuneprecipitates from such cells revealed co-precipitation of erbB-2, demonstrating association of the Grb2/Sos complex with erbB-2 in vivo. Furthermore, a fusion protein containing only the SH2 domain of Grb2 bound to erbB-2 immobilized on nitrocellulose, indicating that association with Grb2 is direct and mediated by the SH2 domain of Grb2. The degree of association between the erbB-2 receptor and Grb2 in vivo was related to erbB-2 overexpression, and MAP kinase, which functions downstream from Ras, displayed markedly increased activity in cell lines overexpressing erbB-2. These results demonstrate that erbB-2 is coupled to Ras signalling via the Grb2/Sos complex, and that overexpression of this receptor in breast cancer cells leads to amplification of the Ras signalling pathway.
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PMID:Activation of the Ras signalling pathway in human breast cancer cells overexpressing erbB-2. 797 Jul 20

We have studied the effect of activation of the c-erbB-2 receptor tyrosine kinase on protein kinase C (PKC) in cultured SKBR-3 human breast cancer cells. Treatment with the agonistic anti-receptor monoclonal antibody TAb 250 induces receptor autophosphorylation and stimulates phospholipase C-gamma 1 (L. K. Shawver et al. Cancer Res., 54: 1367-1373, 1994). TAb 250 induced a rapid and marked translocation of PKC histone phosphorylation activity to the particulate fraction of SKBR-3 cells. By immunoblot, however, this translocation was limited to specific PKC isozymes. beta PKC and zeta PKC translocated to the particulate fraction, whereas epsilon PKC underwent "partial reversed translocation" to the cell soluble fraction after receptor stimulation. Furthermore, beta PKC was rapidly degraded following TAb 250 treatment. By immunocytochemistry, beta IPKC translocated from the perinuclear area to the cytosol and into the nucleus, whereas zeta PKC translocated to the perinuclear region and into the nucleus. Consistent with the Western blot results, epsilon PKC translocated from the nucleus to the perinuclear area and the cytosol. These changes in the localization of PKC isozymes were not observed after addition of normal IgG1 or a nonagonistic anti-c-erbB-2 monoclonal antibody to SKBR-3 cells. alpha, beta II, or delta PKC present in these cells did not translocate following receptor stimulation. These data indicate that c-erbB-2 signal transduction may involve the activation of specific PKC isozymes. The biological role of these enzymes in the phenotype and cellular responses of c-erbB-2-overexpressing carcinoma cells remains to be studied.
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PMID:Distinct responses of protein kinase C isozymes to c-erbB-2 activation in SKBR-3 human breast carcinoma cells. 798 52

We characterized the structure and the function of insulin receptors isolated from 10 human breast cancer specimens. We observed that the insulin receptor content, as determined by a specific radioimmunoassay, was four fold increased in human breast cancer tissue when compared to normal breast tissues. In both cancer and normal breast tissues, insulin receptor mRNA consisted of two major species of approximately 11.0 and 8.5 kilobases. The size of the insulin receptor alpha subunit was determined by 125I-insulin cross-linking followed by immunoprecipitation and polyacrylamide gel electrophoresis; a value of 135kDa was observed for receptors from both breast cancer and normal breast tissues. The functional binding ability of insulin receptors from cancer tissues was slightly lower as compared to normal tissue derived insulin receptor (% B/T = 2.22 +/- 0.50 per ng of insulin receptor as determined by radioimmunoassay vs. 2.96 +/- 0.49, mean +/- S.E.M.). The concentration of insulin that caused half maximal inhibition of 125I-insulin binding was very similar for both cancer and normal breast receptors (80pM). The size of the insulin receptor beta subunit as determined by receptor autophosphorylation was 95kDa. Basal and maximal insulin (100nM) stimulated receptor tyrosine kinase activity, in terms of both receptor autophosphorylation and phosphorylation of an exogenous substrate, was similar in malignant and normal breast tissue derived insulin receptor. Also, a very similar insulin stimulated Km value for ATP was showed by the tyrosine kinase of insulin receptors from breast cancer and normal breast tissue (11.1 and 10.8 microM ATP, respectively). However, in insulin receptors from breast cancer tissue the average tyrosine kinase sensitivity to insulin, as calculated on the exogenous substrate, was higher, although not significantly, with respect to normal breast tissue (ED50 at 0.28 +/- 0.09 and 1.08 +/- 0.33 nM insulin, respectively). A similarly different sensitivity to insulin was observed also for receptor autophosphorylation. In conclusion, this study demonstrates that breast cancer tissues have an increased number of structurally and functionally normal insulin receptors. In some breast cancer tissues, however, the sensitivity of the receptor tyrosine kinase activity to insulin is greatly increased. These data suggest that, in vivo, the mitogenic effect of insulin may play a role in the biology of certain breast cancers.
Breast Cancer Res Treat 1993
PMID:Structural and functional studies of insulin receptors in human breast cancer. 851 10

A series of 36 nitrothiophene tyrphostins were synthesized, 32 of which were novel structures. Their ability to inhibit the epidermal growth factor (EGF) receptor tyrosine kinase was assessed in a cell-free assay. Compounds containing a dinitrile, 2-aminoethene-1, 1-dinitrile or a thioamide group were good inhibitors of the receptor tyrosine kinase. Although anti-proliferative and cytotoxic activity was seen, no evidence of inhibition of EGF receptor autophosphorylation in intact cells was observed. The compounds showed no preferential inhibition of EGF-dependent proliferation of fibroblasts transfected with the EGF receptor. Furthermore, in a panel of squamous cell carcinoma cell lines with varying levels of EGF receptor expression, there was no selective cell kill of lines with the highest EGF receptor expression. The 2-nitro-5-substituted-thiophenes and the 2-nitro-3-substituted-thiophenes showed reduction potentials falling within the range likely to be reduced by cellular reducing agents, while the 2-nitro-4-substituted-thiophenes and 4-nitro-2-substituted-thiophenes did not. Compounds from the 2-nitro-5-substituted-thiophene series were shown to induce DNA damage, while no evidence of DNA damage was demonstrated with compounds from the 2-nitro-4-substituted-thiophene series. The 2-nitro-5-substituted-thiophene compound 4 showed significant tumour-type selectivity in the US National Cancer Institute human tumour cell line panel. The leukaemia cell lines were particularly sensitive to the compound, as were the majority of the colon cancer, melanoma and breast cancer cell lines, while the central nervous system-derived lines and the non-small cell lung cancer lines were particularly resistant. Further work is required to determine the precise mechanisms involved in these effects.
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PMID:Synthesis and biological evaluation of a series of tyrphostins containing nitrothiophene moieties as possible epidermal growth factor receptor tyrosine kinase inhibitors. 867 52

Breast cancer prognosis has previously been linked to the degree of tumour vascularisation. In order to establish additional markers for tumour angiogenesis, we have used monoclonal antibodies against the endothelial Tie receptor tyrosine kinase to study the degree of vascularisation of breast carcinomas and the regulation of Tie expression in the vascular endothelial cells. Antibodies were used for Tie detection and the results were correlated with other prognostic markers. Of four monoclonal antibodies directed against different epitopes of the Tie extracellular domain, two reacted against Tie in unfixed histopathological sections of breast carcinomas. One of these antibodies (clone 7e8) was specific for the endothelial cells whereas the other (clone 10f11) also reacted with basement membranes and occasional carcinoma cells. When Tie expression was studied with the antibody clone 7e8, all 27 carcinomas, two in situ carcinomas, samples of histologically normal breast tissue (n = 16) or normal skin or lymph node tissue (n = 5) showed staining. Microvessel counts were higher in carcinomas (median 14; range 3-27) than in fibrodenomas (median 10; range 5-18) or histologically normal breast tissue (median 7; range 3-15, P = 0.0006). A similar result was obtained using antibodies against the CD31 (PECAM) antigen. Microvessel counts in 7e8 staining were not significantly associated with primary tumour size, axillary nodal status, histological grade or staining for oestrogen receptor, progesterone receptor, Ki-67 proliferation marker or p53 oncoprotein.
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PMID:Endothelial Tie growth factor receptor provides antigenic marker for assessment of breast cancer angiogenesis. 867 61

Overexpression of the Neu/ErbB-2 receptor tyrosine kinase has been implicated in the genesis of human breast cancer. Indeed, expression of either activated or wild-type neu in the mammary epithelium of transgenic mice results in the induction of mammary tumors. Previously, we have shown that many of the mammary tumors arising in transgenic mice expressing wild-type neu occur through somatic activating mutations within the neu transgene itself. Here we demonstrate that these mutations promote dimerization of the Neu receptor through the formation of disulfide bonds, resulting in its constitutive activation. To explore the role of conserved cysteine residues within the region deleted in these altered Neu proteins, we examined the transforming potential of a series of Neu receptors in which the individual cysteine residues were mutated. These analyses indicated that mutation of certain cysteine residues resulted in the oncogenic activation of Neu. The increased transforming activity displayed by the altered receptors correlated with constitutive dimerization that occurred in a disulfide bond-dependent manner. We further demonstrate that addition of 2-mercaptoethanol to the culture medium interfered with the specific transforming activity of the mutant Neu receptors. These observations suggest that oncogenic activation of Neu results from constitutive disulfide bond-dependent dimerization.
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PMID:Mutations affecting conserved cysteine residues within the extracellular domain of Neu promote receptor dimerization and activation. 879 21

Since the mitogenic action of EGF is mediated by ligand-induced autophosphorylation of the EGF receptor (EGFR), and EGFR is commonly overexpressed in solid human tumours, inhibitors of receptor tyrosine kinase activity (RTK) could prove to be effective antitumour agents. Screening of a compound library using an EGF-RTK enzyme prepared from human tumour derived A431 cells identified a series of potent (IC50 < 1 microM) enzyme inhibitors. These inhibitors are quinazolines bearing a variety of substituted anilines at the 4-position. The most potent 4-anilinoquinazolines (IC50 approximately equal to 20 nM) have small non-polar meta substituents on the aniline ring, and are competitive with ATP and non-competitive with substrate. The growth inhibitory activity of these agents was assessed in vitro using KB cells (human oral squamous tumour) grown in the absence or presence of EGF. A selected compound, 4-(3-chloroanilino)quinazoline (CAQ), inhibited EGF-stimulated growth in a concentration dependent manner and complete blockade was observed at concentrations (1-10 microM) which had no effect on basal growth. Selectivity of growth inhibition by CAQ was further exemplified in IGF1-stimulated KB cells where no effect was detected at concentrations which completely blocked EGF-stimulated growth. Similarly, CAQ blocked TGF alpha-stimulated growth in MCF-7 human breast cancer cells without affecting insulin-stimulated growth. These studies define a novel class of EGF-RTK inhibitors which are also potent and selective inhibitors of EGF-stimulated human tumour cell growth in vitro.
Breast Cancer Res Treat 1996
PMID:Specific inhibition of epidermal growth factor receptor tyrosine kinase by 4-anilinoquinazolines. 882 24


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