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:5.99.1.2 (topoisomerase)
9,166 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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

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

Adjuvant chemotherapy has been shown to provide survival benefits in patients with breast cancer, but some patients still relapse despite this. There is therefore a need for molecular markers present within the primary tumour that can predict for chemotherapy sensitivity or resistance. Until now, no single marker has emerged into routine clinical practice, but several candidate pathways are being extensively investigated. This paper summarises the current status of growth factor singalling and p53 function in this context. The data on human epidermal growth factor receptor-2, topoisomerase II and p53 expression in a variety of breast cancer treatment settings are discussed.
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PMID:Growth factor signalling in clinical breast cancer and its impact on response to conventional therapies: a review of chemotherapy. 1611 89

There have been many recent advances in the field of systemic chemotherapy for metastatic colorectal cancer. Each treatment affects a different target, including thymidylate synthase, topoisomerase, DNA, the epidermal growth factor receptor, and vascular endothelial growth factor. These treatments have been used in multiple combinations, schedules, and as first-line, second-line, and third-line therapies. The current clinical trials reported can help guide the clinician to determine the appropriate timing, combination, and schedule of chemotherapy agents. Although the decision regarding colorectal cancer chemotherapy is now more complicated, our patients have certainly benefited from better response rates and most importantly, longer survival times.
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PMID:Target practice: figuring out which, when, and why to use systemic therapies for metastatic colon cancer. 1646 98

In this study, we evaluated, for the first time, the antiproliferative and cytotoxic effects induced by a combination of a selective epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, gefitinib, with other chemotherapeutic drugs including estrogen receptor-beta (ER-beta) antagonist (tamoxifen) and topoisomerase II inhibitor (etoposide) on some metastatic prostate cancer (PC) cell lines. Immunohistochemial analyses revealed that EGFR expression was enhanced in 38% of primary prostatic adenocarcinomas (Gleason scores 4-10) as compared to the corresponding normal tissues of the same prostate gland from 32 PC patients. The RT-PCR and Western blot data have also indicated the higher expression levels of EGFR and ER-beta transcripts and proteins in metastatic LNCaP, DU145 and PC3 cells relative to nonmalignant normal prostate cells. Moreover, the results from MTT and FACS analyses revealed that the drugs, alone or in combination at lower concentrations, inhibited the growth of 17beta-estradiol (E2) plus EGF and serum-stimulated androgen-responsive LNCaP-C33 and androgen-independent LNCaP-C81, DU145 and PC3 cells. Importantly, the combined gefitinib, tamoxifen and etoposide also caused a higher rate of apoptotic death of PC cells as compared to single agents. The cytotoxic effects induced by these drugs in PC3 cells appear to be mediated through the accumulation of cellular ceramide and activation of caspase cascades via a mitochondrial pathway. These findings indicate that the combined use of inhibitors of EGF-EGFR and E2-ER-beta signaling with etoposide, which act by increasing the cellular ceramide levels and caspase activity, represents a promising strategy for a more effective treatment of metastatic PC forms.
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PMID:Novel combination therapy against metastatic and androgen-independent prostate cancer by using gefitinib, tamoxifen and etoposide. 1701 95

The HER-2 (also known as ERBB2/ErbB2/c-erbB2/HER-2/neu) oncogene is the most frequently amplified oncogene in breast cancer and is also amplified in other forms of cancer. Beside its important role in tumor induction, growth and progression, HER-2 is also a target for new therapeutic approaches such as Herceptin (trastuzumab), a recombinant antibody designed to block signaling through the HER-2 receptor. In addition to Herceptin, which is in a wide clinical use for HER-2 amplified breast cancer, a number of various HER-2 directed immunological and genetic strategies, either targeting the HER-2 receptor, its signaling pathways or both HER-2 and epidermal growth factor receptor (EGFR) simultaneously, have demonstrated promising pre-clinical activity in HER-2 amplified carcinomas. Moreover, the HER-2 amplicon is known to contain more than 30 genes with altered copy numbers that could be therapeutic targets for chemotherapy. The topoisomerase IIalpha gene, TOP2A, is located adjacent to the HER-2 oncogene at the chromosome location 17q12-q21 and is either amplified or deleted (with equal frequency) in a great majority of HER-2 amplified primary breast tumors and also in tumors without HER-2 amplification. Recent experimental as well as numerous, large, multi-center trials suggest that amplification (and/or deletion) of TOP2A may account for both sensitivity or resistance to commonly used cytotoxic drugs, i.e. topoII-inhibitors (anthracyclines etc.), depending on the specific genetic defect at the TOP2A locus. The understanding of HER-2 amplification and its role in the pathogenesis of cancer is expanding, and a number of therapeutic strategies targeting either the HER-2 or its signaling pathways in cancer therapy are being investigated. Combining HER-2 targeting therapies with conventional forms of cytotoxic chemotherapy, where additional diagnostic tests such as those ascertaining TOP2A status, may be helpful for the ideal selection of patients for the combination therapy of an HER-2 targeting drug together with a cytotoxic drug such as topoII-inhibitor especially in the case of TOP2A amplification.
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PMID:Simultaneous amplification of HER-2 (ERBB2) and topoisomerase IIalpha (TOP2A) genes--molecular basis for combination chemotherapy in cancer. 1710 May 65

Examination of tumor biological factors for prognostic and predictive indicators is not part of routine testing in ovarian cancer. As in other tumors, the detection of hematogenous tumor spread could help to estimate the risk of metastatic disease. We examined the expression of p53, KI67, topoisomerase IIalpha (Top IIa), epidermal growth factor receptor (EGFR), human epithelial growth factor receptor 2 (HER2) and nm23 in tumor tissues from 90 patients with ovarian cancer. All underwent bone marrow (BM) aspiration and screening for disseminated tumor cells in the bone marrow (DTC-BM) at primary diagnosis. BM aspiration, cytospin preparation, and immunocytochemical staining with the anticytokeratin antibody (A45-B/B3) were done following a standardized protocol. The expression of p53, KI67, Top IIa, EGFR, HER2, and nm23 was evaluated by immunohistochemistry on paraffin-embedded tissue samples and classified by percentage of stained cells or immunoreactive score (IRS). The prognostic impact of the individual factors together with standard histologic parameters was calculated by univariate and multivariate analyses. Expression rates for HER2 (2+/3+: 34.5%), KI67 (median 30%), p53 (median IRS 5), and Top IIa (median IRS 4) were relatively high, whereas nm23 (median IRS 2) and EGFR (IRS 0: 61%) showed weak staining. In 21/90 patients (23.3%), DTC-BM (>/=1/2 x 10(6) cells) could be detected. The presence of DTC-BM was inversely related to nodal status (P = .015) but not to the other factors examined. Tumor stage (P = .02), lymph node involvement (P = .003), grade (P = .046), postoperative tumor residue (P < .001), peritoneal seeding (P = .02), and KI67 (P = .046) significantly correlated with overall survival (OS) after a median observation time of 28 months (2-105). The finding of ascites was borderline significant (P = .050). The presence of DTC-BM (P = .04) and KI67 positivity (P = .02) predicted reduced distant disease-free survival. By multivariate analysis, postoperative tumor residue remained an independent factor for OS (P = .02, relative risk = 4.6). As a primarily locoregional disease, tumor stage and postoperative tumor residue are the main determinants of prognosis in patients with ovarian cancer. However, even in advanced stages, examination of tumor biological factors could help to stratify subgroups of patients and establish targeted therapies.
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PMID:Prognostic impact of KI67, p53, human epithelial growth factor receptor 2, topoisomerase IIalpha, epidermal growth factor receptor, and nm23 expression of ovarian carcinomas and disseminated tumor cells in the bone marrow. 1743 65

The selection of therapy for a particular breast cancer patient is traditionally based on average results from randomized clinical trials. Rational pharmacotherapy is in essence about selecting the right drug(s) for the right patient, and in order to guide this selection process pharmacodiagnostic tests are indispensable. A number of tests have been developed or are under development for targeted therapies, such as antiestrogens, human epidermal growth factor receptor 2 inhibitors, and topoisomerase inhibitors. Based on a biopsy from the tumor, the tests are able to identify patients with a high probability to benefit from these therapies. The detection of the predictive biomarkers is based on different technologies, such as immunohistochemistry, fluorescence in situ hybridization, and chromogenic in situ hybridization. Pharmacodiagnostic tests will play an important role in the further development of targeted therapies and may be seen as a prerequisite for the introduction of individualized medicine in oncology.
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PMID:Pharmacodiagnostics and targeted therapies - a rational approach for individualizing medical anticancer therapy in breast cancer. 1747 Jun 82

The management of colorectal cancer relies heavily on the combination of the pyrimidine analog antimetabolite 5-fluorouracil with the platinum-based drug oxaliplatin or the topoisomerase inhibitor irinotecan. Optimization of dosing and scheduling of these agents to improve response and survival continues to evolve. Meanwhile, the rational targeting of molecular signaling pathways that are involved in the etiology of malignancies is currently one of the most promising strategies in novel anticancer drug development. New classes of drugs that target the epidermal growth factor receptor are among the most clinically advanced molecular-targeted therapies and have shown efficacy in colorectal cancer. The current status of epidermal growth factor receptor-targeted therapeutic agents is reviewed, with emphasis on their role in the management of colorectal cancer.
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PMID:EGFR-targeted therapies in colorectal cancer. 1756 32


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