Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P04626 (erbB-2)
 5,251 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The epidermal growth factor (EGF) receptor (EGFR) promoter is negatively regulated by thyroid hormone and retinoic acid. This regulation can be mapped to a 36-basepair GC-rich region of the promoter (EGFR P/E) that functions autonomously as a promoter and an enhancer when placed in front of the thymidine kinase gene TATA element. Direct high affinity binding of the thyroid hormone receptor (T3R) to this element requires a nuclear protein. Through ion exchange chromatography and gel filtration of HeLa nuclear extract, this activity was identified as a protein of approximately 67 kilodaltons. This protein did not bind to DNA alone, but greatly augmented T3R binding to the EGFR P/E sequence in gel mobility shift and DNA precipitation assays. When combined with the T3R auxillary protein (TRAP), the T3R migrated as a larger complex on the DNA. Chemical cross-linking identified this complex as a heterodimer between T3R and TRAP. T3R-TRAP binds to a 7-basepair site in the EGFR P/E (GGGACTC) that has weak homology to a consensus thyroid response element half-site. Thus, on this element, T3R-TRAP heterodimers contact the DNA primarily on a single site that comprises an inhibitory thyroid response element.
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PMID:A nuclear protein is required for thyroid hormone receptor binding to an inhibitory half-site in the epidermal growth factor receptor promoter. 158 25

To determine the location of sites that may be important for the function of the promoter of the epidermal growth factor (EGF) receptor gene and to characterize the factors that bind to these sites, the promoter region was analyzed by deletion analysis, exonuclease III protection and gel retardation assays with crude and fractionated nuclear extracts and DNase I footprinting using purified Sp1. Transfection of chimeric chloramphenicol acetyltransferase plasmids containing various deletions of the EGF receptor gene promoter into CV-1 cells indicated that the region between -178 and -16 (initiator ATG is +1) is sufficient for promoter activity. Exonuclease III protection assays revealed the presence of eight specific nuclear protein binding sites in the region between -481 and -16. Gel retardation assays confirmed that multiple protein binding sites exist in this region (-481 to -16) and quantitatively agree with exonuclease III protection. DNase I footprinting using purified Sp1 showed that this transcription factor can bind to four sites (-457 to -440, -365 to -286, -214 to -200, and -110 to -84) in the EGF receptor gene promoter and therefore may play a role in its regulation.
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PMID:Epidermal growth factor receptor gene promoter. Deletion analysis and identification of nuclear protein binding sites. 283 11

The epidermal growth factor (EGF) receptor is the functional target of the mitogen EGF and the cellular homolog of the avian erythroblastosis virus erbB oncogene product. Regulation of expression of the proto-oncogene encoding the EGF receptor can be elucidated by studying the structure and function of the gene promoter outside the confines of the cell. Previously, we reported the isolation of the human EGF receptor gene promoter. The promoter is highly GC rich, contains no TATA or CAAT box, and has multiple transcription start sites. An S1 nuclease-sensitive site has now been found 80 to 110 base pairs (bp) upstream from the major in vivo transcription initiation site. Two sets of direct repeat sequences were found in this area; both conform to the motif TCCTCCTCC. When deletion mutations were made in this region of the promoter by using either Bal 31 exonuclease or S1 nuclease, we found that in vivo activity dropped three- to fivefold, on the basis of transient-transfection analysis. Examination of nuclear protein binding to normal and mutated promoter DNAs by gel retardation analysis and DNase I footprinting revealed that two specific factors bind to the direct repeat region but cannot bind to the S1 nuclease-mutated promoter. One of the specific factors is the transcription factor Sp1. The results suggest that these nuclear trans-acting factors interact with the S1 nuclease-sensitive region of the EGF receptor gene promoter and either directly or indirectly stimulate transcription.
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PMID:Modulation of epidermal growth factor receptor proto-oncogene transcription by a promoter site sensitive to S1 nuclease. 284 30

We evaluated the intra- and inter-observer reproducibility of quantitative immunohistochemical (IHC) analyses using the Cell Analysis Systems (CAS) 200/486 image analyzer of Estrogen Receptor (ER), Progesterone Receptor (PR), proliferation-associated nuclear protein (Ki67), HER-2/neu (c-erbB-2) protein over-expression and cathepsin D (CD) in 20 randomly-selected invasive breast carcinomas. Qualitative analysis of IHC Epidermal Growth Factor Receptor (EGF-R) was also assessed in this study for comparative purposes. Duplicate blind assessments by the same observer showed excellent correlations for all quantitative IHC features (P < 0.001; P = 0.004 for neu). However, the immuno-quantitative analyses results between the 3 different operators showed lower correlation coefficient values, thus being less reproducible. This resulted in systematic differences and bias between the observers. This was also clear from the overall agreement between the 3 observers which was 70% for ER, 70% for PR, 56% for Ki67, 79% for c-erbB-2 and 75% for CD. The qualitative visual assessments of EGF-R, expressed as either positive or negative, showed a 75% agreement between observers and 85% intra-observer agreement (comparable to quantitative digital image processing results). The same results were obtained with kappa statistics. A further analysis of the factors causing the lack of reproducibility was performed. For quantitative IHC, segmentation of stored and retrieved digitized images was quite reproducible between and within well-trained observers. However, variation between different fields of vision of one and the same section showed large variations for most cases. Therefore, differences in sampling of fields within a section appeared to be the major cause of lack of reproducibility between observers, although segmentation differences still added slightly to the inter-observer variations. Accordingly, a strict sampling protocol of fields of vision is mandatory to obtain reproducible quantitative IHC results. It is clear from the present study that so-called random (but in fact, at convenience) selection of fields of vision for measurement is not a sufficient guarantee of adequacy of the sampling.
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PMID:Quantitative immunohistochemistry using the CAS 200/486 image analysis system in invasive breast carcinoma: a reproducibility study. 754 96

Triplex-forming oligonucleotides (TFOs) have been shown to bind to target DNA sequences in several human gene promoters such as the c-myc oncogene, the epidermal growth factor receptor, and the dihydrofolate reductase genes. TFOs have been shown to inhibit transcription in vitro and gene expression in cell culture of the c-myc and other genes. The HER-2/neu oncogene, which is overexpressed in breast cancer and other human malignancies, contains a purine-rich sequence in its promoter, which is favorable for purine:purine:pyrimidine (R:R:Y) triplex formation. Although its function in the HER-2/neu promoter is unknown, this purine-rich site is homologous to a protein-binding sequence in the promoter of the epidermal growth factor receptor that is necessary for efficient transcription of this gene. We have shown that this sequence is a site for nuclear protein binding by incubation with a crude nuclear extract. We describe the formation of an interstrand triplex using a purine-rich oligonucleotide antiparallel to this purine-rich target sequence of the HER-2/neu promoter. Triplex formation by the oligonucleotide prevents protein binding to the target site in the HER-2/neu promoter in vitro. We have shown that this oligonucleotide is a potent and specific inhibitor of HER-2/neu transcription in an in vitro assay. The triplex target site contains a single pyrimidine base that does not conform to the R:R:Y triplex motif. In an attempt to abrogate the potentially destabilizing effects of this pyrimidine base on triplex formation, we have substituted an abasic linker for the pyrimidine residue in the triplex forming oligonucleotide. Triplex formation with the modified oligonucleotide appears to occur with approximately equivalent binding affinity. Triplex formation in the HER-2/neu oncogene promoter prevents transcription in vitro and may represent a future modality for specific inhibition of this gene in vivo.
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PMID:Triplex formation inhibits HER-2/neu transcription in vitro. 790 Dec 37

The development of human adenocarcinoma of the lung involves multiple genetic changes including activation of oncogenes and loss of tumor suppressor genes. Patients whose lung tumors contain K-ras oncogene mutation, accumulation of the protein product of the tumor suppressor gene p53, or erbB-2/neu oncoprotein overexpression have been shown to have a worse prognosis. We examined these three genetic indicators in 29 lung adenocarcinomas to determine whether these markers are present in the same tumors or if they represent molecular changes that define different subsets of patients. P53 nuclear protein accumulation and erbB-2/neu protein overexpression were determined by immunohistochemical analysis of cryostat sections of tumor specimens and corresponding normal lung tissue. K-ras mutations were detected by radiolabeled oligonucleotide probes, specific for the various twelfth codon mutations, hybridized to exon 1 of K-ras, which was amplified by the polymerase chain reaction. Increased nuclear accumulation of p53 protein was found in 11 adenocarcinomas (38%). All of the p53 positive tumors were found to show high level staining and homogeneous expression of erbB-2/neu protein. K-ras mutations were detected in seven tumors (24%), all of which overexpressed erbB-2/neu. The presence of a K-ras mutation did not correlate with p53 accumulation. In total, 93% of the tumors were found to overexpress erbB-2/neu, the highest being in one tumor with erbB-2/neu gene amplification. The presence of K-ras twelfth codon mutation was associated with increased cigarette smoking. In conclusion, erbB-2/neu overexpression is a common event in lung adenocarcinomas. Furthermore, the presence of K-ras mutation and p53 protein accumulation define separate groups of patients. The mechanisms by which these genetic alterations interact or adversely affect prognosis is unknown.
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PMID:Alterations of K-ras, p53, and erbB-2/neu in human lung adenocarcinomas. 790 43

Analysis of the proximal promoter of the human erbB-2 gene identified a 100 bp region that enhanced activity of the proximal TATA box 200-fold. DNase I footprinting mapped three Sp1 binding sites within this 100 bp region but only one of these sites was of high affinity and strongly correlated to Sp1-dependent activity in vivo. This Sp1 site overlapped the distal of two similar palindromic sequences. The proximal palindrome did not bind Sp1 but overlaps the CAAT box. When placed in the context of a heterologous promoter, the palindrome functioned as a positive response element. However, removal of the 5' half of the proximal palindrome increased promoter activity indicating that it functions as an inhibitory element within the erbB-2 context. Using electrophoretic mobility shift assays, a nuclear protein was detected that bound to either the 5' or 3' half of the palindrome but not to both. Analysis of the function of mutant sequences revealed maximal activity when both halves of the palindrome were intact with decreased but significant activity persisting when the 3' half of the palindrome was disrupted. Disruption of the 5' half of the palindrome impaired activity to a greater extent. These studies indicate erbB-2 promoter activity is positively regulated by Sp1 and negatively regulated in a position-dependent context by a protein that binds to a palindromic sequence.
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PMID:Positive and negative regulatory elements in the human erbB-2 gene promoter. 791 45

The expression of both the nuclear protein p53 tumor suppressor gene product and the transmembrane C-erbB-2 protein oncogene product (p185) correlates to risk factors and outcomes in different tumor types. Their value as prognosticators in endometrial adenocarcinoma of endometrioid type (EC) has not been determined. Paraffin sections were examined immunohistochemically to study the expression of p53 protein and p185 in 112 patients with EC. p53 protein was overaccumulated in 34% and p185 in 13% of the tumors. p53 protein correlated with mitotic count and nuclear grade. Both p53 protein and p185 correlated significantly with outcome. However, they did not correlate with each other or with architectural grade or stage (which defines a high risk group), indicating a role as adjuvant prognosticators in EC. Stage and outcome did correlate, however. Both p53 protein and p185 antibodies work well on routine, formalin-fixed, paraffin-embedded tissue and are easily used in routine diagnostic procedures.
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PMID:p53 protein and c-erbB-2 protein (p185) expression in endometrial adenocarcinoma of endometrioid type. An immunohistochemical examination on paraffin sections. 791 77

The breast cancer susceptibility gene BRCA1 encodes an 1863-amino acid protein that acts as a tumor suppressor. The biochemical function of BRCA1 is unknown, and there are conflicting results describing its subcellular location. We have identified a 220-kDa protein, which is reactive with three antibodies raised against the amino- and carboxyl-terminal regions of BRCA1. Immunoflourescence staining with an antibody to the carboxyl terminus of BRCA1 localized the protein to the nucleus of breast, ovarian, and cervical carcinoma-derived cell lines. A similar result was observed by biochemical subcellular fractionation that indicated that the 220-kDa protein was localized primarily to the nucleus of cell lines established from breast carcinomas. In addition to the 220-kDa protein, one antibody, C-20, also recognized a 180-kDa protein in MDA-MB-468 total cell lysates that was not detected by the other two antibodies. Several observations suggest the 180-kDa protein is the epidermal growth factor (EGF) receptor: (i) C-20 reacted avidly with a 180-kDa protein immunoprecipitated by an antibody to the EGF receptor; (ii) an EGF receptor antibody detected a 180-kDa protein immunoprecipitated by C-20; (iii) the affinity purified EGF receptor was both immunoprecipitated and detected on immunoblots by the C-20 antibody but not another BRCA1 antibody; (iv) similar phosphopeptide maps were generated from the EGF receptor and the 180-kDa protein immunoprecipitated by C-20, and this peptide map was distinct from the 220-kDa phosphoprotein; and (v) the C-20 immunizing peptide bears sequence identity to the EGF receptor. These results indicate that BRCA1 is a 220-kDa nuclear protein and that the 180-kDa protein reported previously may be unrelated to BRCA1.
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PMID:Subcellular localization and analysis of apparent 180-kDa and 220-kDa proteins of the breast cancer susceptibility gene, BRCA1. 891 Apr 95

Molecular biomarkers for breast cancer are of several types. Risk biomarkers are those associated with increased cancer risk and include mammographic abnormalities, proliferative breast disease with or without atypia, family clustering and inherited germ-line abnormalities. Surrogate endpoint biomarkers are tissue, cellular or molecular alterations that occur between cancer initiation and progression. These biomarkers are utilized as endpoints in short-term chemoprevention trials. Prognostic biomarkers provide information regarding outcome irrespective of therapy, while predictive biomarkers provide information regarding response to therapy. Candidate prognostic biomarkers for breast cancer include elevated proliferation indices such as Ki-67 and proliferating cell nuclear antigen (PCNA); ER and PR overexpression; markers of oncogene overexpression such as c-erbB-2, TGF-a and EGFr; indicators of apoptotic imbalance including overexpression of bcl-2 and an increased bax/bcl-2 ratio; markers of disordered cell signaling such as p53 nuclear protein accumulation; alteration of differentiation signals such as overexpression of c-myc and related proteins; loss of differentiation markers such as TGF-b II receptor and retinoic acid receptor; and alteration of angiogenesis proteins such as VEGF overexpression. As our knowledge regarding molecular biomarkers for breast cancer increases, prognostic indices will be developed that combine the predictive power of individual molecular biomarkers with specific clinical and pathologic factors.
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PMID:Biomarkers for breast cancer. 1214 73


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