Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:5.99.1.3 (topoisomerase)
9,911 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have shown previously that the Epstein-Barr virus nuclear antigen-1 (EBNA1) can act as a transforming suppressor in the HER2/neu-overexpressing ovarian cancer cells. In the present study, by using flow cytometric analysis, we demonstrate that EBNA1 could prolong G(2)/M phase and sensitize to Taxol-induced apoptosis in the EBNA1-expressing ovarian cancer cell stable transfectants. In addition, EBNA1 could also significantly increase topoisomerase IIalpha protein expression, indicating that the up-regulation of topoisomerase IIalpha may be one of the mechanisms by which EBNA1 enhances the sensitivity of ovarian cancer cells to topoisomerase II-targeting anticancer drugs, such as VP-16 and Adriamycin. These data suggest that EBNA1 not only prolongs cell cycle at G(2)/M phase and up-regulates topoisomerase IIalpha expression in HER2/neu-overexpressing ovarian cancer cells, but also increases cellular apoptosis through sensitization of cancer cells to topoisomerase II-directing anticancer drugs.
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PMID:EBNA1 may prolong G(2)/M phase and sensitize HER2/neu-overexpressing ovarian cancer cells to both topoisomerase II-targeting and paclitaxel drugs. 1289 73

This article attempts to provide the reader with a complete overview of topoisomerase (topo) II alpha as a marker for predicting the efficacy of anthracyclines in patients with breast cancer. In the first section of this article, in vitro data supporting the predictive value of topo II alpha are reviewed. Interestingly, these data suggest that the interaction between HER2 and anthracycline efficacy, which has been hypothesized in several clinical studies performed in the past decade, might depend on the concomitant topo II alpha status. Molecular pathology studies further reinforce the concept that HER2 might not be directly involved in the prediction of response to anthracyclines. They report that topo II alpha gene amplification can be found in 25%-40% of HER2/neu-amplified tumors, while no topo II gene amplification is detected in the absence of HER2/neu gene amplification. In the second part of this article, a series of clinical studies are reviewed and interpreted. These studies have attempted to correlate topo II alpha status with anthracycline efficacy in the adjuvant, neoadjuvant, and metastatic settings. All of the studies evaluating the topo II alpha gene suggest that gene amplification might be associated with an increased efficacy of anthracyclines, and some of the studies evaluating topo II alpha protein find that protein overexpression might correlate with an increased sensitivity to these compounds. Despite these findings, however, the reported studies do not provide the proof of principle needed to authorize the use of topo II alpha as a predictive marker for standard practice. A new generation of research is currently testing the predictive value of topo II alpha. It is hoped that these projects, which are described in the last section of the article, will clarify the role of topo IIa in the prediction of response to anthracyclines.
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PMID:Topoisomerase II alpha as a marker predicting the efficacy of anthracyclines in breast cancer: are we at the end of the beginning? 1449 10

In solid tumours the predominant genetic mechanism for oncogene activation is through amplification of genes. The HER-2 (also known as ErbB2/c-erbB2/HER-2/neu) oncogene is the most frequently amplified oncogene in breast cancer and is also commonly amplified in other forms of cancer. The HER-2 amplicon also contains other biologically relevant genes with altered copy numbers, among these genes is the topoisomerase IIalpha (TOP2A). TOP2A gene is located adjacent to the HER-2 oncogene at the chromosome location 17q12-q21 and is either amplified or deleted, with equal frequency, in almost 90% of HER-2 amplified primary breast tumours. Recent data suggest that amplification and deletion of TOP2A may account for both sensitivity and resistance to topoII-inhibitor-chemotherapy, depending on the specific genetic defect at the TOP2A locus. In this issue of the Cytopathology, Bofin et al. present preliminary evidence for high prevalance of TOP2A amplification and deletion not only in the HER-2 amplified breast tumours, but also in the primary breast tumours without the HER-2 amplification. This finding together with the concept that TOP2A gene amplification and deletion seem to account for both relative chemosensitivity and resistance to topoII-inhibitor therapy further highlights the importance of screening for TOP2A gene copy number aberrations when topoII-inhibitors are considered either alone or in combination of other chemotherapeutic drugs for the treatment of cancer patients.
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PMID:Topoisomerase IIalpha gene (TOP2A) amplification and deletion in cancer--more common than anticipated. 1463 28

The HER-2/neu oncogene, a member of the epidermal growth factor receptor or erb gene family, encodes a transmembrane tyrosine kinase receptor that has been linked to prognosis and response to therapy with the anti-HER-2-humanized monoclonal antibody, trastuzumab (Herceptin, Genentech, South San Francisco, CA) in patients with advanced metastatic breast cancer. HER-2/neu status has also been tested for its ability to predict the response of breast cancer to other therapies including hormonal therapies, topoisomerase inhibitors, and anthracyclines. This review includes an analysis of 80 published studies encompassing more than 25,000 patients designed to consider the relative advantages and disadvantages of the various methods of measuring HER-2/neu in clinical breast cancer specimens. Southern blotting, PCR amplification detection, and fluorescence in situ hybridization assays designed to detect HER-2/neu gene amplification are compared with HER-2/neu protein overexpression assays performed by immunohistochemical techniques applied to frozen and paraffin-embedded tissues and enzyme immunoassays performed on tumor cytosols. The significance of HER-2/neu overexpression in ductal carcinoma in situ and the HER-2/neu status in uncommon female breast conditions and male breast cancer are also considered. The role of HER-2/neu testing for the prediction of response to trastuzumab therapy in breast cancer is reviewed along with the current studies designed to test whether HER-2/neu status can predict the response to standard and newer hormonal therapies, cytotoxic chemotherapy, and radiation. The review will also evaluate the status of serum-based testing for circulating HER-2/neu receptor protein and its ability to predict disease outcome and therapy response.
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PMID:Targeted therapy in breast cancer: the HER-2/neu gene and protein. 1476 15

New strategies for improving treatment of patients with breast carcinoma have focused on the HER2 oncoprotein with regard to response to traditional therapy regimes and the effect of a new drug specifically directed against the protein. Furthermore, the status of the topoisomerase IIalpha (TOP2A) gene has been suggested as a predictive marker of anthracycline treatment. In this study of 120 tumours, immunohistochemically detected HER2 overexpression with HercepTest has been compared to the HER2 gene amplification investigated with a new HER2 probe for fluorescence in situ hybridization (FISH). In addition, the HercepTest was evaluated as a screening tool for choosing cases for FISH investigation of TOP2A gene aberrations. The HercepTest score 3+ identified HER2 gene amplification in 27 of 30 amplified tumours (sensitivity of 0.90) with a false-negative rate of 0.10 and a false-positive rate of 0.06. TOP2A gene amplification or deletion was found in 20 cases. Sixteen (80%) of these carcinomas were in the HercepTest 3+ group, but four tumours had alterations in the TOP2A gene with normal HER2 status. Traditionally, in the FISH technique the result has been based on counting 60 cells. However, we found that a much less time-consuming method of counting 60 signals gave equally good results.
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PMID:Amplification of HER2 and TOP2A and deletion of TOP2A genes in breast cancer investigated by new FISH probes. 1506 18

In this study, we examined alterations in the apoptotic response of tamoxifen (TAM)-resistant breast cancer cells. We used an in vitro selection approach for TAM resistance by means of long-term culture of MCF-7 breast cancer cells with increasing concentrations of TAM. The apoptotic response to TAM was determined by means of ELISA measurement of apoptotic DNA-histone complexes in cytoplasm and by Annexin-V staining. MCF-7(LT) cells isolated after 5 months of long-term treatment with TAM exhibited a significantly reduced apoptotic response to this drug, even if administered in high concentrations up to 20 microM. This reduced apoptotic response was also observed after treatment with the topoisomerase II inhibitor etoposide, a pro-apoptotic antineoplastic drug. Microarray experiments comparing the transcriptome of MCF-7(LT) and wild-type cells revealed both the down-regulated expression of several genes coding for pro-apoptotic proteins and the up-regulation of genes coding for apoptosis inhibitors. Further experiments to determine expression changes of the receptor tyrosine kinases HER2 and epidermal growth factor receptor did not reveal any alterations in MCF-7(LT) if compared to wild-type cells. Our findings suggest that long-term treatment with TAM in vitro does not necessarily change the expression of receptor tyrosine kinases, but can modulate the expression of apoptotic key genes impairing the apoptotic response of MCF-7 breast cancer cells.
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PMID:Tamoxifen long-term treatment in vitro alters the apoptotic response of MCF-7 breast cancer cells. 1549 41

In the wake of recent progress in understanding the genetic pathways involved in the development of brain tumors, a major goal is to correlate molecular data with clinical outcome, survival, and response to treatment modalities. This is of particular importance among the pediatric population. Reliable prognostic factors could potentially permit a tailoring of therapy in that only patients with the most aggressive tumors would receive the most intense treatments. A survey of publications about prognosis-related molecular features among pediatric brain tumors revealed 74 series, of which 46 presented statistically significant outcome-associated parameters as defined by a p value <0.05. Most investigations revealing significant prognosis-related features were performed on medulloblastomas (34 publications), followed by astrocytic tumors (6 publications) and ependymomas (5 publications). Promising approaches and molecular markers include gene expression profiles, DNA ploidy, loss of heterozygosity and chromosomal aberrations as detected by CGH and FISH (1q, 17p, 17q), as well as oncogenes/ tumor suppressor genes and their proteins (TP53, PTEN, c-erbB2, N-myc, c-myc), growth factor and hormonal receptors (PDGFRA, VEGF, EGFR, HER2, HER4, ErbB-2, hTERT, TrkC), cell cycle genes (p27) and cell adhesion molecules, as well as factors potentially related to therapeutic resistance (multi-drug resistance, DNA topoisomerase IIalpha, metallothionein, P-glycoprotein, tenascin). This review discusses the predictive potential of molecular markers for clinical outcome and their influence on therapeutic decision-making among children with brain tumors.
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PMID:Prognosis-related molecular markers in pediatric central nervous system tumors. 1562 58

Brain tumors account for approximately 20% of all childhood cancers, and are the leading cause of cancer morbidity and mortality among children. Although numerous demographic, clinical and therapeutic parameters have been identified over the past few years that have significant prognostic bearing for some pediatric brain tumors, predicting the clinical course and outcome among children with central nervous system tumors is still difficult. A survey of publications on prognosis-related histopathological and immunohistochemical features among pediatric brain tumors revealed 172 series, of which 91 presented statistically significant outcome-associated parameters as defined by a P value of less than 0.05. Most investigations revealing significant prognosis-related markers were performed on medulloblastomas (30 publications), ependymomas (25) and astrocytic tumors (18). In total, 16 cohorts consisted of more than 100 cases (5 on ependymomas, 3 each on medulloblastomas and astrocytic tumors). On the other hand, there were also 13 series with fewer than 20 cases (5 on medulloblastomas). Potentially prognostic histopathological markers vary among different entities and consist of assessment of necroses, mitoses, differentiation, vascular proliferation, and growth pattern, whereas immunohistochemical features include proliferation markers (Ki-67, MIB-1), expression of oncogenes/tumor suppressor genes and their proteins (TP53, c-erbB2), growth factor and hormonal receptors (VEGF, EGFR, HER2, HER4, ErbB-2), cell cycle genes (p27, p14ARF) and cell adhesion molecules, as well as factors potentially related to therapeutic resistance (DNA topoisomerase IIalpha, metallothionein, P-glycoprotein, tenascin). This review discusses the prognostic potential of histopathological and immunohistochemical markers that can be investigated by the practicing neuropathologist as part of the routine diagnostic workload, and scrutinizes their benefit for predicting therapy response and patient outcome among children with brain tumors.
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PMID:Prognosis-related histomorphological and immunohistochemical markers in central nervous system tumors of childhood and adolescence. 1564 46

We sought to identify the frequency of amplification of the topoisomerase IIalpha gene (TOP2A) in pancreatic cancer and determine the usefulness of TOP2A immunolabeling in screening for TOP2A and human epidermal growth factor receptor (HER)2/neu amplification. We examined 55 pancreatic adenocarcinoma specimens for TOP2A immunolabeling and identified TOP2A protein expression in all specimens with a nuclear labeling index (NLI; positive nuclei/total nuclei x 100) of 5% to 80%. Normal pancreatic ductal epithelium, proposed to give rise to pancreatic adenocarcinoma, did not demonstrate detectable TOP2A expression. In a subset of specimens selected for fluorescence in situ hybridization analysis of TOP2A and HER2/neu amplification using a recently developed multicolor probe, 7 of 8 lesions with an NLI of 25% or more demonstrated TOP2A amplification, in contrast with 2 of 14 lesions with a TOP2A NLI of less than 25%. In 8 of 9 TOP2A-amplified cases, coamplification of HER2/neu was present, suggesting a potential relationship between TOP2A and HER2/neu in pancreatic adenocarcinoma. We propose that TOP2A immunolabeling be used in conjunction with a newly developed multicolor probe to screen patients with pancreatic adenocarcinoma to determine the best potential therapeutic modalities, such as TOP2A inhibitors, trastuzumab, or both.
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PMID:A subset of pancreatic adenocarcinomas demonstrates coamplification of topoisomerase IIalpha and HER2/neu: use of immunolabeling and multicolor FISH for potential patient screening andtreatment. 1576 77

Clinical and in vitro evidence supports the concept that human epidermal growth factor receptor-2 ( HER2 ) gene amplification prediction of response to anthracycline-based chemotherapy in breast cancer is not a direct effect of HER2 overexpression, but the result of coamplification of topoisomerase II-alpha ( TOP2A ). We investigated the relationship of TOP2A to HER2 genomic alterations by fluorescence in situ hybridization (FISH) and the correlations with polysomic states for chromosome 17 (CEP17). One hundred thirty-eight cases of breast cancer HER2 gene amplified by 2-color FISH ( HER2 /CEP17) were reevaluated with a 3-color probe set ( HER2 /CEP17/ TOP2A ) to investigate the frequency of coamplification and deletion of TOP2A . TOP2A was never amplified in the absence of HER2 amplification and was coamplified with HER2 in 68 (50%) of 137 cases; HER2 gene copy number was higher than the TOP2A copy number ( P < .01). Of the 137 cases with HER2 amplification, 23 (16%) showed a monoallelic deletion of TOP2A . Of the 43 cases not amplified for HER2 , 27 (63%) were CEP17 eusomic, 13 (30%) polysomic, and 3 (7%) monosomic. Of the HER2 nonamplified cases, 2 (5%) showed monoallelic deletion of both the HER2 and TOP2A . The current study demonstrates the complex interrelationship between the HER2 and TOP2A genes in breast cancer. The clinical implications of TOP2A amplification and deletion in breast cancer need to be further defined. If TOP2A gene dosage can be confirmed to correlate with tumor responsiveness to anthracycline-based therapy in the clinical setting, FISH testing for TOP2A status may be warranted to aid in the selection of the most appropriate therapy.
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PMID:The incidence of topoisomerase II-alpha genomic alterations in adenocarcinoma of the breast and their relationship to human epidermal growth factor receptor-2 gene amplification: a fluorescence in situ hybridization study. 1589 95


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