Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0006142 (breast cancer)
 160,383 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Tight control of cell proliferation and morphogenesis is required to ensure normal tissue patterning and prevent cancer formation. Overexpression of the ErbB-2/Neu receptor tyrosine kinase is associated with increased progression in human breast cancer, yet in breast explant cultures, the ErbB-2/Neu receptor contributes to alveolar differentiation. To examine the consequence of deregulated ErbB-2/Neu activation on epithelial morphogenesis, we have expressed a constitutively activated mutant of ErbB-2/Neu in a Madin-Darby canine kidney (MDCK) epithelial cell model. Using two-dimensional cultures we demonstrate that activated ErbB-2/Neu induces breakdown of cell-cell junctions, increased cell motility and dispersal of epithelial colonies. This correlates with reorganization of the actin cytoskeleton and focal adhesions and loss of insoluble cell-cell junction complexes involving E-cadherin. Interestingly, a constitutively activated ErbB-2/Neu receptor promotes an invasive morphogenic program in MDCK cells in a three-dimensional matrix. We show that two tyrosines in the carboxy-terminal tail of ErbB-2/Neu, involved in the phosphorylation of the Shc adapter protein, are each sufficient to promote epithelial-mesenchymal like transition and enhanced cell motility in two-dimensional culture and cell invasion rather than a morphogenic response in matrix culture. This provides a model system to investigate ErbB-2/Neu induced signaling pathways required for epithelial cell dispersal and invasion versus morphogenesis.
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PMID:Distinct tyrosine autophosphorylation sites mediate induction of epithelial mesenchymal like transition by an activated ErbB-2/Neu receptor. 1131 13

Hypoxia-inducible factor 1 (HIF-1) is a transcriptional activator composed of HIF-1alpha and HIF-1beta subunits. Several dozen HIF-1 targets are known, including the gene encoding vascular endothelial growth factor (VEGF). Under hypoxic conditions, HIF-1alpha expression increases as a result of decreased ubiquitination and degradation. The tumor suppressors VHL (von Hippel-Lindau protein) and p53 target HIF-1alpha for ubiquitination such that their inactivation in tumor cells increases the half-life of HIF-1alpha. Increased phosphatidylinositol 3-kinase (PI3K) and AKT or decreased PTEN activity in prostate cancer cells also increases HIF-1alpha expression by an undefined mechanism. In breast cancer, increased activity of the HER2 (also known as neu) receptor tyrosine kinase is associated with increased tumor grade, chemotherapy resistance, and decreased patient survival. HER2 has also been implicated as an inducer of VEGF expression. Here we demonstrate that HER2 signaling induced by overexpression in mouse 3T3 cells or heregulin stimulation of human MCF-7 breast cancer cells results in increased HIF-1alpha protein and VEGF mRNA expression that is dependent upon activity of PI3K, AKT (also known as protein kinase B), and the downstream kinase FRAP (FKBP-rapamycin-associated protein). In contrast to other inducers of HIF-1 expression, heregulin stimulation does not affect the half-life of HIF-1alpha but instead stimulates HIF-1alpha synthesis in a rapamycin-dependent manner. The 5'-untranslated region of HIF-1alpha mRNA directs heregulin-inducible expression of a heterologous protein. These data provide a molecular basis for VEGF induction and tumor angiogenesis by heregulin-HER2 signaling and establish a novel mechanism for the regulation of HIF-1alpha expression.
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PMID:HER2 (neu) signaling increases the rate of hypoxia-inducible factor 1alpha (HIF-1alpha) synthesis: novel mechanism for HIF-1-mediated vascular endothelial growth factor expression. 1135 7

MUC4 is a one of the membrane mucins of the mucin gene (MUC) family, characterized by mucin tandem repeat domains and a transmembrane domain which associates it with the cell plasma membrane. Although MUC4 is encoded by a single gene, it is produced by epithelial cells as a heterodimer through a proteolytic cleavage mechanism. This heterodimer is found in both membrane and soluble forms associated with epithelia. Functionally, MUC4 is proposed to provide a protective mechanism for vulnerable epithelia, such as those of the airway, eye, female reproductive tract and mammary gland. The protective mechanism(s) may be highjacked by some carcinomas, such as those of the breast, to increase tumor progression. Two mechanisms are proposed to contribute to the MUC4 functions. First, MUC4 acts as an anti-adhesive or anti-recognition barrier at epithelial or tumor cell surfaces. Second, MUC4 can bind the receptor tyrosine kinase ErbB2 and alter its cellular signaling. Expression of MUC4 in mammary gland is repressed by posttranscriptional mechanisms involving basement membrane and TGF-beta, which are relieved during pregnancy to permit secretion of MUC4 into milk. These mechanisms are also abrogated in some breast cancers, providing a scenario for promotion of tumor progression. These observations imply important functions for MUC4 in both normal mammary function and in breast cancer.
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PMID:Muc4/sialomucin complex in the mammary gland and breast cancer. 1154 1

The ErbB2 receptor tyrosine kinase (RTK) has been intensely pursued as a cancer therapy target due to its association with breast cancer. In this study we used the HC11 mammary epithelial cell line to develop an orthotopic, ErbB2-driven tumor model for testing efficacy of anti-cancer compounds. HC11 cells were infected with a retrovirus encoding oncogenic NeuT, the rat homolog of ErbB2. Drug-selected populations were introduced into mammary fat pads of Balb/c syngeneic mice cleared of host tissue. The majority of glands injected with HC11-NeuT cells developed mammary tumors which appeared after a 3-4 week latency period and grew rapidly. HC11 cells infected with the control retrovirus showed no tumor growth after injection. Tumor-bearing mice were used to compare the in vivo efficacy of two anti-cancer agents: PKI166, a kinase inhibitor selective for EGF receptor and ErbB2, and Taxol, a microtubule assembly blocker. PKI166 inhibited NeuT-induced mammary tumor growth in a dose-dependent manner and at a dose below the maximum tolerated dose (MTD) was significantly more inhibitory than Taxol at its MTD (57% vs. 25% tumor regression). Importantly, there was a dose-dependent decrease in the phosphotyrosine content of NeuT isolated from PKI166-treated, tumor-bearing mice, providing a mechanistic link between kinase inhibition and its anti-tumor activity. Thus, implantation of genetically manipulated HC11 cells into mammary glands appears to be an excellent model for studying effects of anti-cancer agents in an orthotopic site.
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PMID:Mammary glands reconstituted with Neu/ErbB2 transformed HC11 cells provide a novel orthotopic tumor model for testing anti-cancer agents. 1157 43

The ErbB2 gene encodes a transmembrane growth factor receptor that belongs to the ErbB receptor tyrosine kinase subfamily. ErbB2 protein is overexpressed in approximately 30% of breast cancers. Although controversies exist, data from our laboratory and from clinical trials of trastuzumab indicate that ErbB2 overexpression confers chemoresistance to certain chemotherapeutic agents such as paclitaxel. One of the molecular mechanisms of ErbB2-mediated paclitaxel resistance is that overexpression of the ErbB2 receptor leads to deregulation of the G2/M cell cycle check-point that inhibits paclitaxel-induced apoptosis. Several promising ErbB2-targeting strategies have now been developed to conquer the adverse consequences of ErbB2 overexpression such as paclitaxel resistance. Among these, trastuzumab has brought great promise. We have recently shown that trastuzumab can effectively sensitize ErbB2-overexpressing breast cancer cells to paclitaxel by reversing the antiapoptotic function of ErbB2. Our studies provide additional support for chemotherapy combined with trastuzumab for ErbB2-overexpressing breast cancers, and it may bring insights into designing more effective and specific therapies that could offer great benefits to patients.
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PMID:Mechanisms of ErbB2-mediated paclitaxel resistance and trastuzumab-mediated paclitaxel sensitization in ErbB2-overexpressing breast cancers. 1170 91

Cardiotoxicity is a common and potentially devastating side effect of antineoplastic drug therapy. This empiric observation is seen as paradoxical given that the cardiomyocyte is considered to be a terminally differentiated cell. Despite the fact that these cells do not divide after birth, adult cardiomyocytes may become "innocent bystander" targets of anticancer drugs designed to interfere with cell signaling pathways in rapidly proliferating cells. In breast cancer clinical trials, treatment with the erbB2 receptor antibody trastuzumab combined with anthracyclines has been associated with an increased risk for the development of cardiac pump failure. Trastuzumab/anthracycline cardiomyopathy may be the first clinically significant cardiotoxicity to emerge from signal transduction therapeutics. The erbB2 receptor tyrosine kinase is known to have a critical role in cardiac development. In addition, erbB2 is thought to participate in an important pathway for growth, repair, and survival of adult cardiomyocytes as part of a signaling network that involves neuregulins and the neuregulin receptor erbB4. However, erbB2 levels in the adult heart are low when compared with the levels found in erbB2-overexpressing breast cancer cells that are the intended targets of trastuzumab therapy. Thus, trastuzumab-associated cardiotoxicity must be explained by some alternative mechanism. After confirming that trastuzumab is capable of inducing tyrosine phosphorylation of the human cardiomyocyte erbB2 protein, a novel system for culturing human myocardium was developed in our laboratory. We used this system to study the effects of trastuzumab on human cardiomyocytes in vitro and observed trastuzumab-induced structural and functional changes in human cardiomyocytes that were at least partially reversible with the addition of recombinant neuregulins. The results obtained in these experiments support a direct action of trastuzumab on human cardiomyocytes. In addition, these data provide insight regarding potential molecular mechanisms. Most importantly, these data draw attention to the inherent risk of cardiotoxicity associated with a newly emerging class of antineoplastic drugs that interfere with signal transduction pathways.
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PMID:Cardiotoxicity in signal transduction therapeutics: erbB2 antibodies and the heart. 1170 92

The factors controlling epithelial proliferation in ductal carcinoma in situ (DCIS) are unclear. Antiestrogens are effective in the prevention of the majority of estrogen receptor-positive, but not estrogen receptor (ER)-negative breast cancers, which suggests that other factor(s) are promoting proliferation in ER-negative DCIS. Mutated or overexpressed tyrosine kinases are frequently associated with tumor development. Epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase that is involved with mitogenesis and is expressed in ER-negative DCIS. We hypothesized that EGFR is central in driving proliferation in ER-negative/EGFR-positive DCIS. The purpose of this study was to establish whether the EGFR tyrosine kinase inhibitor (EGFR-TKI), ZD1839 (Iressa), can reduce epithelial proliferation and increase apoptosis in EGFR-positive DCIS. Breast tissue from 16 women undergoing surgery for DCIS were implanted into 16-32 immunosuppressed mice/experiment (8 xenografts/mouse). Treatment commenced 2 weeks after implantation and consisted of once daily oral gavage with ZD1839 at doses ranging from 10 to 200 mg/kg for 14-28 days; appropriate controls were present. Xenografts were removed on days 14, 21, 28, and 42 after implantation and then assessed for proliferation (LI) by Ki67 immunostaining and apoptosis index (AI) by morphology. All Ps reported are two-sided. Overall, a 56% reduction in epithelial proliferation was seen with Iressa in EGFR-positive DCIS. EGFR-TK inhibition compared with vehicle controls resulted in a fall in Geometric Mean Labeling Index (LI) after 14 days (day 28) of treatment both in ER-negative/EGFR-positive DCIS [6.5% interquartile range (IQR, 3.8-11.1) versus 13.9% (IQR, 12.0-16.3%); F(1,3) = 103; P = 0.002] and ER-positive/EGFR-positive DCIS [4.6% (IQR, 3.9-5.2%) versus 11.7% (IQR, 9.2-15.5); F(1,2) = 32.3; P = 0.03]. EGFR-TK inhibition had similar effects on the "at risk" normal breast epithelium adjacent to DCIS in the treated epithelium LI day 28 [ZD1839 2.2% (IQR, 1.7-3.3%) compared with control 3.8% (IQR, 2.4-5.4%); F(1,14) = 29.2; P = 0.00009] and in addition increased epithelial apoptotic index at day 21 [ZD1839 0.38 (0.23-0.83) compared with control 0.19 (0.1-0.25); F(1,6) = 12.2; P = 0.013]. The effect on epithelial proliferation was still significant after 28 days of treatment [for both DCIS (F1,29) = 24; P = 0.039 and normal breast F(1,6) = 47.3; P = 0.0005]. EGFR-TK inhibition with ZD1839 offers a novel approach to the treatment of EGFR-positive DCIS, regardless of ER status, and provides a potential new chemopreventative approach in patients at high risk of breast cancer.
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PMID:Effect of epidermal growth factor receptor tyrosine kinase inhibition on epithelial proliferation in normal and premalignant breast. 1178 68

Amplification and/or overexpression of the receptor tyrosine kinase HER2/Neu and the cell cycle regulatory gene cyclin D1 are frequently associated with human breast cancer. We studied the functional significance of cyclin D1 in Neu-induced mammary oncogenesis by developing mice overexpressing either wild-type or mutant Neu in a cyclin D1 deficient background. The absence of cyclin D1 suppresses mammary tumor formation induced by the wild-type or activated mutant form of Neu, which promote multi- and single-step progression of tumorigenesis, respectively. These data indicate that cyclin D1 is preferentially required for Neu-mediated signal transduction pathways in mammary oncogenesis. Significantly, 35% of mutant Neu/cyclin D1(-/-) mice regained mammary tumor potential due to compensation by cyclin E. Thus, shared targets of cyclins D1 and E are important in modulating Neu function in mammary tumorigenesis. Our results imply that the combinatorial inhibition of cyclins D1 and E might be useful in the treatment of malignancies induced by Neu.
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PMID:Suppression of Neu-induced mammary tumor growth in cyclin D1 deficient mice is compensated for by cyclin E. 1180 72

ErbB-2, a member of the epidermal growth factor(EGF) receptor tyrosine kinase family, is often overexpressed and/or amplified in breast, ovarian and gastric cancers, and other malignancies. ErbB-2 is a candidate as one of the best target molecules for cancer therapy. Many anti-ErbB-2 monoclonal antibodies(MoAbs) have been developed. An inhibitory humanized MoAb shows clinical responses in some breast cancer patients, both with MoAb alone and in combination with Cisplatinum or other anti-cancer drugs. A mouse-human chimeric anti-ErbB-2 MoAb CH401 was established and characterized in our laboratory. CH401 is able to kill cancer cells overexpressing ErbB-2 both in vitro and in vivo. The analysis of this tumor growth inhibition by CH401 made it clear that the cytotoxicity was induced by apoptosis. These results may suggest that CH401 has a therapeutic potential for ErbB-2 overexpressing cancers. This approach may be particularly valuable as a new type of cancer therapy.
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PMID:[Monoclonal antibody induces apoptosis against cancer cells]. 1190 57

Amplification of the gene encoding the ErbB2 (Her2/neu) receptor tyrosine kinase is critical for the progression of several forms of breast cancer. In a large-scale clinical trial, treatment with Herceptin (trastuzumab), a humanized blocking antibody against ErbB2, led to marked improvement in survival. However, cardiomyopathy was uncovered as a mitigating side effect, thereby suggesting an important role for ErbB2 signaling as a modifier of human heart failure. To investigate the physiological role of ErbB2 signaling in the adult heart, we generated mice with a ventricular-restricted deletion of Erbb2. These ErbB2-deficient conditional mutant mice were viable and displayed no overt phenotype. However, physiological analysis revealed the onset of multiple independent parameters of dilated cardiomyopathy, including chamber dilation, wall thinning and decreased contractility. Additionally, cardiomyocytes isolated from these conditional mutants were more susceptible to anthracycline toxicity. ErbB2 signaling in cardiomyocytes is therefore essential for the prevention of dilated cardiomyopathy.
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PMID:ErbB2 is essential in the prevention of dilated cardiomyopathy. 1198 89


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