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)

Genetic abnormalities leading to infant leukemias already occur during fetal development and often involve rearrangements of the mixed-lineage leukemia (MLL) gene. These rearrangements resemble the aberrations observed in therapy-related leukemias following treatment with topoisomerase II (topoII)-inhibiting agents such as etoposide. Since flavonoids are potent topoII inhibitors, we examined the role of three widely consumed dietary flavonoids (quercetin, genistein and kaempferol) on the development of MLL rearrangements in primary human CD34(+) cells. Using the neutral Comet assay, we demonstrated a dose-dependent double-strand break (DSB) formation after exposure to flavonoids. An incorrect repair of these DSBs resulted in chromosomal translocations that co-localized with those identified in infant leukemias. Most of these translocations were formed by microhomology-mediated end joining. Moreover, in all but one translocation, SINE/Alu or LINE/L1 repetitive elements were present in at least one side of the breakpoint junction. Beside MLL translocations, fluorescence in situ hybridization analysis demonstrated monosomy or trisomy of MLL in 8-10% of the quercetin-exposed CD34(+) cells. Our study demonstrates that biologically relevant concentrations of flavonoids can induce MLL abnormalities in primary hematopoietic progenitor cells. This is particularly alarming knowing that the differences in metabolism and excretion rate between mother and fetus can lead to a higher flavonoid concentration on the fetal side. Therefore, it is important to raise public awareness and set guidelines for marketing flavonoid supplements to reduce the risk of infant leukemias.
Carcinogenesis 2007 Aug
PMID:Dietary flavonoids induce MLL translocations in primary human CD34+ cells. 1746 13

alpha-Methylacyl coenzyme A racemase (AMACR), Ki-67, and topoisomerase IIalpha were immunohisto-chemically evaluated in prostate carcinoma (PCa), high-grade prostatic intraepithelial neoplasia (HPIN), normal-looking epithelium (NEp), and atrophy in 20 cystoprostatectomy (CyP) and 20 radical prostatectomy (RP) specimens with pT2a Gleason score 6 PCa. The aim was to see whether there were differences in marker expression between CyP and RP specimens. The results showed that the proportions of AMACR-, Ki-67-, and topoisomerase IIalpha-positive cells in the CyP and RP specimens increased from NEp and atrophy through HPIN, away from and adjacent to PCa, to PCa. AMACR expression in PCa in CyP specimens was slightly lower than in RP specimens, but the differences were not significant; there were significant differences in Ki-67 and topoisomerase IIalpha indices. Our findings in marker expression in NEp, atrophy, and HPIN suggest that there are some differences in the field effects in terms of prostatic carcinogenesis between CyP and RP specimens.
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PMID:alpha-Methylacyl coenzyme A racemase, Ki-67, and topoisomerase IIalpha in cystoprostatectomies with incidental prostate cancer. 1787 19

The involvement of cyclooxygenase (COX)-2 in oral carcinogenesis and outcome of the patients is not fully understood. To determine whether COX-2 expression could serve as an indicator for them, we examined the expression of COX-2 and DNA topoisomerase (DNA-Topo) II alpha as an index of cell proliferating activity in precancerous and cancerous lesions of the oral mucosa. A 164 samples composed of 60 intraepithelial dysplasias (IEDs), 12 carcinomas in situ (CISs), 72 squamous cell carcinomas (SCCs) including 12 early invasive SCCs, 10 undifferentiated carcinomas (UCs), and 10 epithelial hyperplasias (EHPs) in the oral mucosa were examined immunohistochemically for COX-2 and DNA-Topo II alpha. Normal squamous epithelium as the control showed no COX-2 expression, whereas 41% of IEDs, 67% of CISs, 74% of SCCs, and 86% of UCs demonstrated increased COX-2 expression with elevated DNA-Topo II alpha labeling index (LI). High COX-2 expression was also observed in 61% of EHPs, but DNA-Topo II alpha LI was very low. Increased expression of COX-2 protein correlated with elevated DNA-Topo II alpha LI, indicating that COX-2 may contribute to malignant transformation and tumor growth. These two enzyme activities were increased as T, N, and M categories and stages proceeded. The patients with high expression of both COX-2 and DNA-Topo II alpha showed poor prognosis. Our results suggested that COX-2 expression become a possible indicator in oral carcinogenesis and may reflect the outcome of the patients.
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PMID:Expression of cyclooxygenase-2 and DNA topoisomerase II alpha in precancerous and cancerous lesions of the oral mucosa. 1799 82

Comprehensive multivariate models were used to disclose whether any of our previously analyzed 13 markers would be independent predictors of intermediate end point markers in cervical carcinogenesis. The expression of the following biomarkers, E-cadherin, extracellular signal-regulated kinase 1, 67-kd laminin receptor (LR67), matrix metalloproteinase 2, tissue inhibitor of metalloproteinase 2, nuclear factor-kappaB, nm23-H1, p16, proliferating cell nuclear antigen, survivin, human telomerase reverse transcriptase, topoisomerase 2alpha, and vascular endothelial growth factor (VEGF) C in 150 cervical cancer (CC) and 152 cervical intraepithelial neoplasia (CIN) lesions were determined immunohistochemically. Multivariate models were constructed to test predictive power of the markers for 3 outcomes: (1) high-grade CIN, (2) high-risk human papillomavirus (HR-HPV), and (3) CC survival. Performance indicators were calculated and compared by the areas under receiver operating characteristic (ROC) curve. Three marker panels were identified consisting of 5 independent predictors of CIN2 (E-cadherin, extracellular signal-regulated kinase 1, LR67, topoisomerase 2alpha, and VEGF-C), 3 predictors of HR-HPV (survivin, p16, and human telomerase reverse transcriptase), and 2 predictors of CC survival (nm23-H1 and tissue inhibitor of metalloproteinase 2). In predicting CIN2, the best balance between sensitivity (SE) and specificity (SP) was obtained by combining the 2 most powerful predictors in panel 1 (VEGF-C and LR67), giving the area under ROC curve, 0.897 (95% confidence interval [CI], 0.847-0.947); odds ratio, 86.27 (95% CI, 19.71-377.47); SE, 86.0%; SP, 93.3%; positive predictive value (PPV), 99.1%; and negative predictive value (NPV), 43.1%. In a hypothetical screening setting (10,000 women; CIN2 prevalence, 1%), this marker combination should theoretically detect CIN2 with 86.0% SE, 100% SP, 99.1% PPV, and 99.6% NPV, area under ROC curve of 0.930 (95% CI, 0.909-0.951), and odds ratio, 29998.0 (95% CI, 7,879.0-37,338.0). Combining 2 markers (LR67 and VEGF-C) enables accurate detection of high-grade CIN in a clinical setting. However, testing the performance of this marker combination in a screening setting necessitates their analysis in cytological samples.
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PMID:Predicting high-risk human papillomavirus infection, progression of cervical intraepithelial neoplasia, and prognosis of cervical cancer with a panel of 13 biomarkers tested in multivariate modeling. 1831 13

Despite major advances in the molecular biology of the cancer cell over the past two decades, the great majority of patients are still treated by conventional cytotoxic drugs. The chemotherapy regimens employed frequently include platinating agents, taxanes, intercalating agents and topoisomerase inhibitors. Attempts to predict the therapeutic efficacy of such drugs by molecular profiling (theranostics) have up to the present time had limited success. Genes responsible for the control of cell division, senescence and apoptosis whose normal functions become corrupted during carcinogenesis, might potentially play a part in determining chemotherapeutic response. Here we have examined the relationships between the chemoresponsiveness of 18 human in vitro cancer cell lines and proteomic expression of Ras, cyclins B1 and D1 and cyclin-dependent kinases Cdk1 and Cdk4. When all 18 cell lines were examined as a single group, proteomic expression did not provide any helpful theranostic predictors. Clear relationships between proteomic expression and drug efficacy emerged, however, when Ras, cyclin B1, cyclin D1, Cdk1 and Cdk4 were examined separately in p53 wild-type and p53 mutant cell subsets. We suggest that the theranostic relationships we have detected in vitro may have potential relevance in vivo and should prompt clinical theranostic studies which take account of p53 mutational status.
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PMID:Theranostic proteomic profiling of cyclins, cyclin dependent kinases and Ras in human cancer cell lines is dependent on p53 mutational status. 1836 Jul 17

Tea polyphenols are promising chemopreventive anticancer agents, the properties of which have been studied both in vitro and in vivo, providing evidence that - within this group of compounds - the tea flavanols are able to inhibit carcinogenesis, an effect that in some cases could be correlated with increased cell apoptosis and decreased cell proliferation. Of four main tea flavanols, namely (-)-epigallocatechin-3-gallate (EGCG), (-)-epigallocatechin (EGC), (+)-catechin (CA) and (-)-epicatechin (EC), it was found that EGCG was the most potent to inhibit dose dependently the topoisomerase II (TOPO II) catalytic activity isolated from hamster ovary AA8 cells. In the range of concentrations that caused TOPO II inhibition, a high level of endoreduplication, a rare phenomenon that consists in two successive rounds of DNA replication without intervening mitosis, was observed, while neither micronuclei nor DNA strand breaks (Comet assay) were detected at the same doses. We propose that the anticarcinogenic effect of tea flavanols can be partly explained by their potency and effectiveness to induce endoreduplication. Concerning such an induction, maximum effect seems to require a pyrogallol structure at the B-ring. Additional substitution with a galloylic residue at the C3 hydroxyl group leads to further augmentation of the effect. Thus, we suggest that the chemopreventive properties of tea flavanols can be at least partly due to their ability to interfere with the cell cycle and block cell proliferation at early stages of mitosis.
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PMID:Tea flavanols inhibit cell growth and DNA topoisomerase II activity and induce endoreduplication in cultured Chinese hamster cells. 1854 53

Topoisomerases are targets of several anticancer agents because their inhibition impedes the processes of cell proliferation and differentiation in carcinogenesis. With very limited information available on the inhibitory activities of peptides derived from dietary proteins, the objectives of this study were to employ co-immunoprecipitation to identify inhibitory peptides in soy protein hydrolysates in a single step and to investigate their molecular interactions with topoisomerase II. For this, soy protein isolates were subjected to simulated gastrointestinal digestion with pepsin and pancreatin, and the human topoisomerase II inhibitory peptides were co-immunoprecipitated and identified on a CapLC- Micromass Q-TOF Ultima API system. The inhibitory activity of these peptides from soy isolates toward topoisomerase II was confirmed using three synthetic peptides, FEITPEKNPQ, IETWNPNNKP,and VFDGEL, which have IC 50 values of 2.4, 4.0, and 7.9 mM, respectively. The molecular interactions of these peptides evaluated by molecular docking revealed interaction energies with the topoisomerase II C-terminal domain (CTD) (-186 to -398 kcal/mol) that were smaller than for the ATPase domain (-169 to -357 kcal/mol) and that correlated well with our experimental IC 50 values ( R (2) = 0.99). In conclusion, three peptides released from in vitro gastrointestinal enzyme digestion of soy proteins inhibited human topoisomerase II activity through binding to the active site of the CTD domain.
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PMID:Identification and characterization of topoisomerase II inhibitory peptides from soy protein hydrolysates. 1859 77

Ochratoxin A (OTA) is a potent renal carcinogen, but little is known regarding the mechanism of OTA carcinogenicity. Early histopathological alterations induced by OTA in rat kidney include single cell death, stimulation of cell proliferation and prominent karyomegaly indicative of blocked nuclear division during mitosis. Based on these observations, it has been suggested that disruption of mitosis by OTA may be the principal cause of cell death and subsequent trigger for cell proliferation to compensate for cell loss. To gain further insight into the molecular mechanism of OTA toxicity, we used targeted quantitative real-time polymerase chain reaction arrays to investigate the expression of genes involved in cell cycle control and mitosis in kidneys of male F344 rats treated with 0, 21, 70 and 210 microg/kg body wt OTA for up to 90 days. Treatment with OTA resulted in overexpression of key regulators of mitosis, including the mitotic protein kinases Polo-like kinase 1, Aurora B and cyclin-dependent kinase 1 (Cdk1Cdc2), several cyclins and cyclin-dependent kinase inhibitors, topoisomerase II and survivin. Immunohistochemical analysis confirmed upregulation of Cdk1, p21(WAF1/CIP1), topoisomerase II and survivin in S3 proximal tubule cells, from which OTA-induced tumors in rats arise, and demonstrated increased phosphorylation of histone H3, a target of Aurora B. Importantly, many of the genes found to be deregulated in response to OTA have been linked to chromosomal instability and malignant transformation, supporting the hypothesis that aberrant mitosis, resulting in blocked or asymmetric cell division, accompanied by an increased risk of aneuploidy acquisition, may play a critical role in OTA carcinogenicity.
Carcinogenesis 2009 Apr
PMID:Modulation of key regulators of mitosis linked to chromosomal instability is an early event in ochratoxin A carcinogenicity. 1923 4

Natural products represent a rich reservoir of potential small chemical molecules exhibiting antiproliferation and anticancer properties. An example is berberine, a protoberberine alkaloid widely distributed in medical plants used in traditional Chinese prescriptions. Recent advances have shown that berberine exerts anticancer activities both in vitro and in vivo through different mechanisms. Berberine shows inhibitory effects on the proliferation and reproduction of certain tumorigenic microorganisms and viruses, such as Heliobacter pylori and hepatitis B virus. Transcriptional regulation of some oncogene and carcinogenesis-related gene expression and interaction with both DNA and RNA are also well documented. Besides, berberine is a broad spectrum enzyme inhibitor, which affects N-acetyltransferase, cyclooxygenase-2, and topoisomerase activities and gene/protein expression. These actions, together with the regulation of reactive oxygen species production, mitochondrial transmembrane potential, and nuclear factor-kappaB activation might underlie its antiproliferative and proapoptotic effects. More importantly, the suppression of tumor growth and metastasis, the beneficial application in combined medication, and the improvement of multidrug resistance both in vivo and in vitro clearly show its potential as an alternative medicine for tumor chemotherapy.
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PMID:A systematic review of the anticancer properties of berberine, a natural product from Chinese herbs. 1970 71

Despite their individual key roles in promoting head and neck squamous cell carcinoma (HNSCC) progression and treatment resistance, little is known about the impact of intratumoral hypoxia on the activity of the epidermal growth factor receptor (EGFR) signaling pathway in this cancer type. Here, we show that in highly EGFR-expressing HNSCC cells, hypoxic stress triggers the activation of the EGFR and downstream targets, including Akt and phospholipase C (PLC) gamma1. In support of these findings, we also demonstrate that EGFR activation takes place within hypoxic foci in a subset of human HNSCC tissues. Whereas hypoxia had no major effect on HNSCC cell proliferation, it markedly altered tumor cell shape by inducing morphological changes consistent with a more spindle-shaped, fibroblast-like morphology together with an enhanced migratory capacity. We found that hypoxia-induced EGFR activation and cell migration could be prevented by targeting EGFR signaling with the tyrosine kinase inhibitor tyrphostin, the phospholipase C inhibitor U73122, or by inhibiting the expression of the alpha subunit of hypoxia-inducible factor 2 via RNA interference or the topoisomerase II inhibitor etoposide. Our results position hypoxia-inducible factor-2alpha as a novel regulator of EGFR activation under low oxygen conditions, and suggest that hypoxia-induced EGFR signaling may promote a more aggressive phenotype in a fraction of HNSCC tumors. Because EGFR continues in the forefront as a highly attractive target in clinical oncology, further studies are warranted to define the mechanistic and therapeutic implications of the hypoxic response relative to the EGFR signaling pathway in head and neck cancer.
Carcinogenesis 2010 Jul
PMID:HIF-2alpha-mediated activation of the epidermal growth factor receptor potentiates head and neck cancer cell migration in response to hypoxia. 2039 90


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