Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.24 (mitogen-activated protein kinase)
 95,810 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previously, we have identified a panel of breast cancer antiestrogen resistance (BCAR) genes. Several of these genes have clinical relevance because mRNA or protein levels associate with tamoxifen resistance or tumor aggressiveness. We postulated that changes in activation status of protein signaling networks induced by BCAR genes may provide better insight into the mechanisms underlying antiestrogen resistance. Key signal transduction pathways were analyzed for changes in activation or expression using reverse-phase protein microarrays probed with 78 antibodies against signaling proteins with known roles in tumorigenesis. We used ZR-75-1-derived cell lines transduced with AKT1, AKT2, BCAR1, BCAR3, BCAR4, EGFR, GRB7, HRAS, HRAS(v12) or HEF1 and MCF7-derived cell lines transduced with BCAR3, BCAR4 or EGFR. In the antiestrogen-resistant cell lines, we observed increased phosphorylation of several pathways involved in cell proliferation and survival. All tamoxifen-resistant cell lines contained high levels of phosphorylated AKT and its biochemically linked substrates Forkhead box O1/3. The activation of ERBB2, ERBB3 and the downstream modulators focal adhesion kinase and SHC were activated in cells with overexpression of BCAR4. Remarkable differences were observed for the levels of activated AMPK alpha1, cyclins, STAT5, STAT6, ERK1/2 and BCL2. The comparison of the cell signaling networks in estrogen-dependent and -independent cell lines revealed biochemically linked kinase-substrate markers that comprised systemically activated signaling pathways involved in tamoxifen resistance. Our results show that this model provides insights into the molecular and cellular mechanisms of breast cancer progression and antiestrogen resistance. This knowledge may help the development of novel targeted treatments.
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PMID:Protein pathway activation mapping reveals molecular networks associated with antiestrogen resistance in breast cancer cell lines. 2232 89

The ERBB proteins are cell membrane tyrosine kinase receptors. Among these receptors, ERBB1 (EGFR or HER1) and ERBB2 (HER2/Neu) have been reported to be the most important in terms of the development and progression of squamous cell carcinoma of the esophagus (SCC). Thus, targeting of ERBB1 and ERBB2 may become a promising strategy to treat SCC. In the present study, we examined ERBB1 and ERBB2 expression of SCC cell lines (TT, TE2, TE6 and TE10) and tumor samples. In addition, we evaluated the effect of the anti-ERBB1 antibody cetuximab and the anti-ERBB2 antibody trastuzumab for SCC in vitro and in vivo. Biological activities (receptor downregulation, the phosphorylation of MAPK and AKT) induced by the two agents were also investigated. Immunohistochemistry of SCC samples showed that ERBB1 was detected in 84%, while ERBB2 was detected in 30%. RT-PCR analysis revealed that ERBB1 and ERBB2 mRNA were detectable in all four cell lines. MTT cell proliferation analysis showed that cetuximab, but not trastuzumab, inhibited growth in each of the SCC cell lines in a dose-dependent manner. Further, cetuximab and trastuzumab used together produced stronger inhibition of growth compared to cetuximab alone. Cetuximab downregulated ERBB1, but not ERBB2, at the TE6 cell surface. However, neither ERBB1 nor ERBB2 showed any downregulation by trastuzumab at the TE6 cell surface. Cetuximab, not but trastuzumab, inhibited the phosphorylation of MAPK and Akt. When administered in combination, the two agents inhibited Akt phosphorylation to a greater degree compared to treatment with cetuximab alone. In the in vivo study, cetuximab, but not trastuzumab, significantly inhibited the TT tumors. Additionally, the combination of cetuximab with trastuzumab induced a synergistic inhibitory antitumor effect in the TT tumors. In conclusion, combination of cetuximab and trastuzumab revealed a synergistic antitumor effect for SCC in vitro and in vivo. The antitumor effect may be induced by the inhibition of the phosphorylation of Akt. These findings suggest that combination therapy including cetuximab and trastuzumab may be a promising strategy to treat SCC.
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PMID:Concurrent biological targeting therapy of squamous cell carcinoma of the esophagus with cetuximab and trastuzumab. 2256 13

Increased activation of the epidermal growth factor receptor (EGFR) is frequently observed in tumors, and inhibition of the signaling pathways originated in the EGFR normally renders tumor cells more sensitive to apoptotic stimuli. However, we show that inhibition of EGFR signaling in non-transformed breast epithelial cells by EGF deprivation or gefitinib, an inhibitor of EGFR tyrosine kinase, causes the upregulation of the long isoform of caspase-8 inhibitor FLICE-inhibitory protein (FLIP(L)) and makes these cells more resistant to the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). We demonstrate that the extracellular signal-regulated kinase (ERK)1/2 pathway plays a pivotal role in the regulation of FLIP(L) levels and sensitivity to TRAIL-induced apoptosis by EGF. Upregulation of FLIP(L) upon EGF deprivation correlates with a decrease in c-Myc levels and c-Myc knockdown by siRNA induces FLIP(L) expression. FLIP(L) upregulation and resistance to TRAIL in EGF-deprived cells are reversed following activation of an estrogen activatable form of c-Myc (c-Myc-ER). Finally, constitutive activation of the ERK1/2 pathway in HER2/ERBB2-transformed cells prevents EGF deprivation-induced FLIP(L) upregulation and TRAIL resistance. Collectively, our results suggest that a regulated ERK1/2 pathway is crucial to control FLIP(L) levels and sensitivity to TRAIL in non-transformed cells, and this mechanism may explain the increased sensitivity of tumor cells to TRAIL, in which the ERK1/2 pathway is frequently deregulated.
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PMID:Control of FLIP(L) expression and TRAIL resistance by the extracellular signal-regulated kinase1/2 pathway in breast epithelial cells. 2272 37

The EGFR (ERBB) family provides a model system for receptor signaling, oncogenesis, and the development of targeted therapeutics. Heterodimers of the ligand-binding-deficient ERBB2 (HER2) receptor and the kinase impaired ERBB3 (HER3) create a potent mitogenic signal, but the phosphorylation of ERBB2 in this context presents a challenge to established models of phosphorylation in trans. Higher order complexes of ERBB receptors have been observed biophysically and offer a theoretical route for ERBB2 phosphorylation, but it is not clear whether such complexes provide functionality beyond the constituent dimers. We now show that a previously selected inhibitory RNA aptamer that targets the extracellular domain (ECD) of ERBB3 acts by sterically disrupting these higher order interactions. Ligand binding, heterodimerization, phosphorylation of ERBB3, and AKT signaling are only minimally affected, whereas ERBB2 phosphorylation and MAPK signaling are selectively inhibited. The mapping of the binding site and creation of aptamer-resistant point mutants are consistent with a model of side-by-side oriented heterodimers to facilitate proxy phosphorylation, even at very low endogenous levels of receptors (below 10,000 receptors per cell). Additional modes of signaling with relevance to pathological ERBB expression states emerge at high receptor levels. Hence, higher order complexes of nonoverexpressed ERBB receptors are an integral and qualitatively distinct part of normal ERBB2/ERBB3 signaling. This mechanism of activation has implications for models of allosteric control, specificity of interactions, possible mechanisms of cross-talk, and approaches to therapeutic intervention that at present often generate experimental and clinical outcomes that do not reconcile with purely canonical, dimer-based models.
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PMID:Functional isolation of activated and unilaterally phosphorylated heterodimers of ERBB2 and ERBB3 as scaffolds in ligand-dependent signaling. 2285 69

Epidermal growth factor receptor (EGFR) signaling is strongly implicated in glioblastoma (GBM) tumorigenesis. However, molecular agents targeting EGFR have demonstrated minimal efficacy in clinical trials, suggesting the existence of GBM resistance mechanisms. GBM cells with stem-like properties (CSCs) are highly efficient at tumor initiation and exhibit therapeutic resistance. In this study, GBMCSC lines showed sphere-forming and tumor initiation capacity after EGF withdrawal from cell culture media, compared with normal neural stem cells that rapidly perished after EGF withdrawal. Compensatory activation of related ERBB family receptors (ERBB2 and ERBB3) was observed in GBM CSCs deprived of EGFR signal (EGF deprivation or cetuximab inhibition), suggesting an intrinsic GBM resistance mechanism for EGFR-targeted therapy. Dual inhibition of EGFR and ERBB2 with lapatinib significantly reduced GBM proliferation in colony formation assays compared to cetuximab-mediated EGFR-specific inhibition. Phosphorylation of downstream ERBB signaling components (AKT, ERK1/2) and GBM CSC proliferation were inhibited by lapatinib. Collectively, these findings show that GBM therapeutic resistance to EGFR inhibitors may be explained by compensatory activation of EGFR-related family members (ERBB2, ERBB3) enabling GBM CSC proliferation, and therefore simultaneous blockade of multiple ERBB family members may be required for more efficacious GBM therapy.
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PMID:Activation of multiple ERBB family receptors mediates glioblastoma cancer stem-like cell resistance to EGFR-targeted inhibition. 2274 88

Truncated-ERBB2 isoforms (t-ERBB2s), resulting from receptor proteolysis or alternative translation of the ERBB2 mRNA, exist in a subset of human breast tumors. t-ERBB2s lack the receptor extracellular domain targeted by therapeutic anti-ERBB2 antibodies and antibody-drug conjugates, including trastuzumab, trastuzumab-DM1 and pertuzumab. In clinical studies, expression of t-ERBB2 in breast tumors correlates with metastasis as well as trastuzumab resistance. By using a novel immuno-microarray method, we detect a significant t-ERBB2 fraction in 18 of 31 (58%) of immunohistochemistry (IHC)3+ ERBB2+ human tumor specimens, and further show that t-ERBB2 isoforms are phosphorylated in a subset of IHC3+ samples (10 of 31, 32%). We investigated t-ERBB2 biological activity via engineered expression of full-length and truncated ERBB2 isoforms in human mammary epithelial cells (HMECs), including HMEC and MCF10A cells. Expression of p110 t-ERBB2, but not p95m (m=membrane, also 648CTF) or intracellular ERBB2s, significantly enhanced cell migration and invasion in multiple cell types. In addition, only expression of the p110 isoform led to human breast epithelial cell (HMLE) xenograft formation in vivo. Expression of t-ERBB2s did not result in hyperactivation of the phosphoinositide kinase-3/AKT or mitogen-activated protein kinase signaling pathways in these cells; rather, phosphoproteomic array profiling revealed attenuation of phosphorylated signal transducer and activator of transcription 5 (STAT5) in p110-t-ERBB2-expressing cells compared to controls. Short hairpin-mediated silencing of STAT5 phenocopied p110-t-ERBB2-driven cell migration and invasion, while expression of constitutively active STAT5 reversed these effects. Thus, we provide novel evidence that (1) expression of p110 t-ERBB2 is sufficient for full transformation of HMEC, yielding in vivo xenograft formation, and (2) truncated p110 t-ERBB2 expression is associated with decreased phosphorylation of STAT5.
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PMID:Truncated p110 ERBB2 induces mammary epithelial cell migration, invasion and orthotopic xenograft formation, and is associated with loss of phosphorylated STAT5. 2275 Nov 12

The anticancer drug lapatinib (Tykerb) is a dual tyrosine kinase inhibitor targeting the HER2 (ERBB2) and EGFR (ERBB1, HER1) pathways that have been shown in clinical trials to display some cardiotoxicity. Because trastuzumab also targets HER2 receptors, the lapatinib/doxorubicin combination provides a good model to probe the mechanism of the increased cardiotoxicity caused by the concurrent use of trastuzumab and doxorubicin. Using a neonatal rat cardiac myocyte model, we have investigated the ability of lapatinib alone and in combination with doxorubicin to damage myocytes. Lapatinib treatment alone only slightly induced myocyte damage. However, doxorubicin-induced myocyte damage was greatly potentiated by the addition of nanomolar lapatinib concentrations. Lapatinib alone treatment decreased phosphorylated ERK (MAPK), which may have, in part, contributed to the increased myocyte damage. As measured by flow cytometry, lapatinib-treated myocytes displayed an increased accumulation of doxorubicin. As lapatinib is a strong inhibitor of several ATP-dependent ABC-type efflux transporters, this likely occurred because lapatinib blocked doxorubicin efflux, thereby increasing intracellular doxorubicin concentrations and, thus, increasing myocyte damage. These results suggest that the clinical use of concurrent doxorubicin and lapatinib should be approached with care due to the possibility of lapatinib increasing doxorubicin cardiotoxicity.
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PMID:The dual-targeted HER1/HER2 tyrosine kinase inhibitor lapatinib strongly potentiates the cardiac myocyte-damaging effects of doxorubicin. 2294 10

We have further defined mechanism(s) by which the drug OSU-03012 (OSU) kills brain cancer cells. OSU toxicity was enhanced by the HSP90 inhibitor 17-N-Allylamino-17-demethoxygeldanamycin (17AAG) that correlated with reduced expression of ERBB1 and ERBB2. Inhibition of the extrinsic apoptosis pathway blocked the interaction between 17AAG and OSU. OSU toxicity was enhanced by the inhibitor of ERBB1/2/4, lapatinib. Knock down of ERBB1/2/4 in a cell line specific fashion promoted OSU toxicity. Combined exposure of cells to lapatinib and OSU resulted in reduced AKT and ERK1/2 activity; expression of activated forms of AKT and to a lesser extent MEK1 protected cells from the lethal effects of the drug combination. Knock down of PTEN suppressed, and expression of PTEN enhanced, the lethal interaction between OSU and lapatinib. Downstream of PTEN, inhibition of mTOR recapitulated the effects of lapatinib. Knock down of CD95, NOXA, PUMA, BIK or AIF, suppressed lapatinib and OSU toxicity. Knock down of MCL-1 enhanced, and overexpression of MCL-1 suppressed, drug combination lethality. Lapatinib and OSU interacted in vivo to suppress the growth of established tumors. Collectively our data argue that the inhibition of ERBB receptor function represents a useful way to enhance OSU lethality in brain tumor cells.
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PMID:OSU-03012 interacts with lapatinib to kill brain cancer cells. 2299 Feb 4

Genetic and epigenetic alterations are induced during gastric carcinogenesis. Infection by H. pylori markedly increases induction of both alterations, and inflammation triggered by the infection is critical for induction of aberrant DNA methylation (epigenetic alterations). Oncogenes, such as PIK3CA, CTNNB1, KRAS, and ERBB2, are activated by point mutations and gene amplification. Tumor-suppressor genes, such as TP53, CDH1, CDKN2A, and MLH1, are inactivated by mutations, and more frequently by aberrant methylation if they have promoter CpG islands. The information on the activated signaling pathway, such as the ERBB2-MAPK signaling pathway, is now becoming useful for patient stratification. Comprehensive analysis of genetic and epigenetic alterations in gastric cancers is expected to lead to more occasions of translation.
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PMID:[Genetic and epigenetic alterations in gastric carcinogenesis]. 2319 49

Aberrant expression and activation of EGFR and ERBB2 (HER2) have been successfully targeted for cancer therapeutics. Recent evidence from both basic and clinical studies suggests that ERBB3 (HER3) serves as a key activator of downstream signaling through dimerization with other ERBB proteins and plays a critical role in the widespread clinical resistance to EGFR and HER2 targeting cancer therapies. As a result, HER3 is actively pursued as an antibody therapeutic target for cancer. Ligand binding is thought to be a prerequisite for dimerization of HER3 with other ERBB proteins, which results in phosphorylation of its c-terminal tyrosine residues and activation of downstream AKT and MAPK signaling pathways. In this study, we report that an anti-HER2 monoclonal antibody (HER2Mab), which blocks HER2 dimerization with HER3, induces HER3 dimerization with EGFR in both low and high HER2 expressing cancer cells. Treatment of the low HER2 expressing MCF7 cancer cells with HER2Mab promoted cell proliferation and migration in the absence of HER3 ligand stimulation. Follow-up studies revealed that HER2Mab-induced HER3 signaling via EGFR/HER3 dimerization and activation of downstream AKT signaling pathways. These results suggest that equilibrium of dimerization among the ERBB proteins can be perturbed by HER2Mab and HER3 plays a key role in sensing the perturbation.
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PMID:ERBB3 (HER3) is a key sensor in the regulation of ERBB-mediated signaling in both low and high ERBB2 (HER2) expressing cancer cells. 2334 51


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