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

---

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

Drug resistance is a major problem in patients with small cell lung cancer; in fact, most die of resistant disease, despite an initial response. Several markers of drug resistance have been described in preclinical models, but the mechanism of drug resistance in lung cancer patients remains unknown. The objective of this study was to evaluate the role of the expression of a number of markers of drug resistance, proliferation, and apoptosis in relation to response to chemotherapy and survival in patients with small cell lung cancer. Tumor samples were derived from 93 previously untreated patients who were randomized in a Phase III study to receive cyclophosphamide, epirubicine, and etoposide or cyclophosphamide, epirubicine and vincristine alternating with carboplatin and etoposide. Paraffin-embedded samples, derived from the primary tumor site prior to chemotherapy, were analyzed by immunohistochemistry for expression of markers implicated in drug resistance [topoisomerase (topo) IIalpha, topo IIbeta, and multidrug resistance-associated protein], apoptosis (p53, p21, and bcl-2), or proliferation (Ki67). Response prediction was analyzed by chi2 test and logistic regression analysis; overall and disease-free survival curves were compared by log-rank test and Cox regression analysis. Shorter survival was observed in patients with extensive disease (P = 0.037) and poorer performance status (P = 0.028) and in patients whose tumors expressed high topo IIalpha levels (P = 0.01) and high Ki67 (P = 0.024). By multivariate analysis, the following factors were found to be predictive for worse survival: high expression levels of topo IIalpha, Ki67, and bcl-2; male sex; and extensive disease. High topo IIbeta expression was found to be predictive for lower overall and complete response rate. No relationship between apoptotic pathway markers or MRP and response to chemotherapy was observed. In conclusion, high expression of topo IIalpha was predictive of worse survival, and high expression of topo IIbeta was predictive of lower response rates. Furthermore, lower survival probability was observed in patients with bcl-2-positive tumors. Immunohistochemical assessment of these markers in diagnostic biopsies may give important prognostic information and may help selecting patients in the worse prognostic categories for new therapeutic strategies.
...
PMID:Expression of DNA topoisomerase IIalpha and topoisomerase IIbeta genes predicts survival and response to chemotherapy in patients with small cell lung cancer. 1047 85

Molecular analysis of hereditary nonpolyposis colorectal carcinomas (HNPCC) has identified DNA mismatch repair deficiencies with resulting microsatellite instability (MSI) as a pathway of carcinogenesis that appears to be relevant for prognosis, treatment, and possibly prevention. In this study, expression of cell cycle proteins and other known prognostic markers is correlated with the microsatellite status of colorectal cancers (CRC). One hundred consecutive cases from the CRC Registry at Thomas Jefferson University were analyzed for MSI. Immunohistochemistry was performed for the mismatch repair proteins hMLH1 and hMSH2, tumor suppressor p53, apoptosis inhibitor bcl-2, cell cycle proteins p21(WAF1/CIP1), and p27 and the proliferation markers Ki-67 and topoisomerase II. High MSI (MSI-H) is significantly correlated with loss of either hMLH1 or hMSH2, presence of bcl-2, and absence of p53. p21(WAF1/CIP1) is positive in all tumors with MSI-H. Previous findings of a lower proliferation rate were confirmed with a topoisomerase II stain. Microsatellite stable (MSS) tumors generally express both MSH2 and MLH1. Other highly significant differences are positive p53 in 56% of MSS cases and negative bcl-2 in 98% of MSS cases. p27 expression is found in approximately 50% of all CRCs irrespective of the microsatellite status. MSI-H tumors follow the mutator pathway, with loss of expression of one mismatch repair protein, wild-type p53, lower proliferation, and positivity for p21(WAF1/CIP1). MSS tumors follow the suppressor pathway, characterized by p53 overexpression, higher proliferation, and absence of bcl-2 expression; p21(WAF1/CIP1) expression can be variable. These data provide a molecular basis for the clinical observation that patients with HNPCC appear to have a more favorable prognosis. HUM PATHOL 31:1506-1514.
...
PMID:Colorectal carcinomas with high microsatellite instability: defining a distinct immunologic and molecular entity with respect to prognostic markers. 1115 Mar 76

Several studies have shown that extracellular matrix reduces chemotherapeutic drugs-induced apoptosis in small cell lung cancer cells, myelomas and gliomas. We have investigated the protective effect of defined extracellular matrix components and of extracellular matrix from different cell types (fibroblasts, hepatocytes and intestinal epithelial cells) on the toxicity of three types of chemotherapeutic drugs on colon cancer cells. Human colon cancer cell lines LS174T and LiM6 were plated on plastic, on hepatocyte-derived ECM or on stromal ECM and in the presence of the antimetabolite 5-fluorouracil (5-FU). the topoisomerase I inhibitor camptothecin and the topoisomerase II inhibitor etoposide. We determined IC50 for the drugs for each of these culture conditions. We also determined the expression of the anti-apoptotic proteins bcl-2 and bcl-x (L) under these culture conditions. We found that stromal ECM protected LiM6 cells from the toxicity of etoposide and LS174T, but not LiM6 cells, from the toxicity of camptothecin. Collagen 1, fibronectin and fibroblast-derived ECM rendered LiM6 cells, but not LS174T, more sensitive to the harmful effect of 5-FU. Both colon cell lines had increased expression of anti-apoptotic proteins bcl-2 and bcl-x(L) when cultured on the various ECMs and with the drugs, but there was no correlation between a protective ECM effect and expression of the anti-apoptotic proteins. Stromal-derived ECM may protect colon cancer cells from etoposide and camptothecin-induced apotosis, through a mechanism that is not bcl-2 or bcl-x(L) dependant.
...
PMID:Stromal extracellular matrix reduces chemotherapy-induced apoptosis in colon cancer cell lines. 1191 83

Several studies have shown that hexavalent chromium [Cr(VI)] induces apoptosis in a variety of in vitro test systems. We instilled intra-tracheally either saline or sodium dichromate (0.25 mg/kg body weight), for three consecutive days, to Sprague-Dawley rats. TUNEL analyses showed a marked increase of the apoptotic index in both bronchial epithelium and lung parenchyma of Cr(VI)-treated rats, but no effect was detected in their liver. In parallel, the expression of 13 out of 18 apoptosis-related genes, evaluated by cDNA array analysis, was significantly enhanced in rat lung. The overexpressed genes included c-Jun N-terminal kinases 1, 2 and 3, bcl-x, bcl-2-associated death promoter and bcl-2-related ovarian killer protein, caspases 1, 3 and 6, DNase I precursor, DNA topoisomerases I and II alpha, and poly(ADP-ribose) polymerase. The enhancement of p53 expression in the lung was borderline to statistical significance. Expressions of bcl-2, bax-alpha, mdm2 and DNA topoisomerase IIB were not enhanced to a significant extent in lung. No induction of gene expression was observed in rat liver. RT-PCR analyses confirmed that Cr(VI) enhances the expression of c-Jun N-terminal kinase 1, caspase 6, and DNase I precursor but not that of bcl-2 in lung, while none of these genes was overexpressed in the liver of Cr(VI)-treated rats. The lack of stimulation of apoptosis in the liver parallels the failure of Cr(VI) to produce genotoxic damage, as we previously observed under identical experimental conditions. These negative findings may be ascribed to reduction of Cr(VI) to Cr(III) when traveling from the respiratory tract to the liver. On the other hand, induction of apoptosis in the respiratory tract parallels the occurrence of genotoxic effects and oxidative DNA damage produced by Cr(VI) in the same tissue. As previously shown in another laboratory, Cr(VI) did not induce lung tumors after 30 months of administration of the same daily dose. Therefore, apoptosis is likely to provide a protective mechanism at a post-genotoxic stage of Cr(VI) carcinogenesis.
...
PMID:Induction of apoptosis in the lung but not in the liver of rats receiving intra-tracheal instillations of chromium(VI). 1196 Sep 10

Numerous studies demonstrate that the chemopreventive effect of non-steroidal anti-inflammatory drugs on colon cancer is mediated through inhibition of cell growth and induction of apoptosis. For these effects non-steroidal anti-inflammatory drugs have been recently employed as sensitising agents in chemotherapy. We have shown previously that treatments with aspirin and NS-398, a cyclo-oxygenase-2 selective inhibitor, affect proliferation, differentiation and apoptosis of the human colon adenocarcinoma Caco-2 cells. In the present study, we have evaluated the effects of aspirin and NS-398 non-steroidal anti-inflammatory drugs on sensitivity of Caco-2 cells to irinotecan (CPT 11) and etoposide (Vp-16) topoisomerase poisons. We find that aspirin co-treatment is able to prevent anticancer drug-induced toxicity, whereas NS-398 co-treatment poorly affects anticancer drug-induced apoptosis. These effects correlate with the different ability of aspirin and NS-398 to interfere with cell cycle during anticancer drug co-treatment. Furthermore, aspirin treatment is associated with an increase in bcl-2 expression, which persists in the presence of the anticancer drugs. Our data indicate that aspirin, but not NS-398, determines a cell cycle arrest associated with death suppression. This provides a plausible mechanism for the inhibition of apoptosis and increase in survival observed in anticancer drug and aspirin co-treatment.
...
PMID:Effect of non-steroidal anti-inflammatory drugs on colon carcinoma Caco-2 cell responsiveness to topoisomerase inhibitor drugs. 1198 87

The topoisomerase-I inhibitor irinotecan (CPT-11) is currently used in Phase I/II trials for the treatment of patients with recurrent malignant gliomas. Protein kinase C (PKC) inhibitors such as high-dose tamoxifen and hypericin also have been used in the treatment of malignant gliomas. The current study examined the role of PKC inhibitors as chemosensitizers for CPT-11 and their proposed mechanism of action. Two glioma cell lines (A-172 and U-87) and one primary glioma cell culture (LA-567) were used. Proliferation ((3)H-thymidine) and cytotoxicity (methylthiotetrazole) studies were performed using CPT-11 (0-100 microM) alone, 7-ethyl-10-hydroxy camptothecin (SN-38) (0-1000 nM) alone or in the presence of a PKC inhibitor, tamoxifen (10 microM), hypericin (10 microM), calphositin C (400 nM), or staurosporine (10 nM). The terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling(TUNEL) assay was used to determine apoptosis as the mechanism of cytotoxicity; alterations in bcl-2 and bax expression were determined using Western blot analysis. Conversion of CPT-11 to SN-38 by glioma cells was determined using high-performance liquid chromatography (HPLC) analysis. Increasing CPT-11 and SN-38 concentrations induced cytotoxic morphologic changes, decreased proliferation, and increased cytotoxicity on all glioma cell lines tested. These changes were increased in the presence of a PKC inhibitor. The mechanism of the cytotoxicity was determined to be apoptosis by the TUNEL assay. The combination of a PKC inhibitor with CPT-11 or SN-38 led to decreased expression of the antiapoptotic protein bcl-2, and increased expression of the proapoptotic protein bax. HPLC analysis demonstrated conversion of CPT-11 to SN-38 by glioma cells. A combination of CPT-11 or SN-38 with a PKC inhibitor was found to lead to a decrease in proliferation and an increase in apoptosis in malignant glioma cells. The induction of apoptosis was secondary to a decrease in bcl-2 and an increase in bax expression. Glioma cells are capable of converting CPT-11 to SN-38 by intrinsic tumor carboxylesterases.
...
PMID:Combination therapy with irinotecan and protein kinase C inhibitors in malignant glioma. 1271 58

Salvicine, a novel topoisomerase II inhibitor and a diterpenoid quinone compound, exerts potent in vitro and in vivo antitumor effects. In our study, we show that salvicine effectively kills multidrug-resistant (MDR) sublines, such as K562/A02, KB/VCR and MCF-7/ADR, and parental K562, KB and MCF-7 cell lines to an equivalent degree. These cytotoxic activities of salvicine were much more potent than those of several classical anticancer drugs (average resistance factor: 1.42 for salvicine vs. 344.35, 233.19 and 71.22 for vincristine, doxorubicin and etoposide, respectively). Flow cytometry and DNA agarose gel electrophoresis demonstrated that salvicine induced similar levels of apoptosis in MDR K562/A02 and parental cells. The compound activated caspase-1 and -3 (but not caspase-8) and increased the ratio of bax to bcl-2 mRNA via reduction of bcl-2 mRNA expression in the same cells. Furthermore, salvicine induced the downregulation of mdr-1 gene and P-gp expression but had no effect on MRP and LRP gene expression in MDR K562/A02 cells. These results suggest that the reduction of mdr-1 and bcl-2 expression by salvicine possibly contributes to its cytotoxicity and apoptotic induction in this system. The effectiveness, broad-spectrum activity and possibly novel mechanism of killing MDR tumor cells in vitro of salvicine signify promising in vivo and clinical activity. The novel chemical structure of this compound further implies a role for salvicine in future MDR tumor therapy.
...
PMID:Cytotoxicity, apoptosis induction and downregulation of MDR-1 expression by the anti-topoisomerase II agent, salvicine, in multidrug-resistant tumor cells. 1279 65

The etiology and pathogenesis of Hodgkin lymphoma (HL) are not yet known. There are implications of genes involved in programmed cell death (apoptosis), and there have been repeated suggestions of an association with Epstein-Barr virus (EBV). The aim of this study was to investigate the protein expression patterns of key cell cycle-related genes, together with evidence of apoptosis and EBV status, in relation to clinical stage in HLs. A double immunohistochemical and in situ hybridization technique was used to detect the expression of bcl-2, p53, retinoblastoma (Rb), p21, Ki67 (MIB 1), and topoisomerase IIalpha (TopoIIalpha), together with latent membrane protein-1 and EBER for EBV status and TdT-mediated dUTP-FITC nick end-labeling (TUNEL) as a measure of apoptosis, on tissue microarray sections of 62 cases of classic HL (35 NS, 17 MC, 8 LR, and 2 LD). A panel of phenotypic markers was used to facilitate recognition of Hodgkin and Reed-Sternberg (H-RS) cells: CD3, CD20, CD30, CD15, and EMA. The H-RS cells of 62 classic Hodgkin lymphomas were bcl-2-positive in 35 cases (56.45%), p53-positive in 14 (22.58%), and positive for both EBV latent membrane protein-1 and EBER in 37 (59.68%); there was complete concordance of results for EBV by both procedures. No correlation was found between expression of bcl-2, p53, or EBV markers in H-RS cells and clinical stage (P > 0.05). Expression of Rb, Ki67, p21, and TopoIIalpha did, however, show significant differences with clinical stage. Expression of Rb and p21 in CD30-positive H-RS cells decreased with more advanced stage (P < 0.001). In contrast, Ki67 and ToPoIIalpha expression increased with later stage (P < 0.01). No correlation was found between expression of any of these markers in H-RS cells and the subtypes of nodular sclerosis HL, mixed cellularity HL, and LRHL (P > 0.05). TUNEL was found in the nonneoplastic cellular background in all cases and in H-RS cells in only 10 of 62 cases (16.12%) (8 nodular sclerosis HL, 1 mixed cellularity HL, and 1 LRHL). There was a significant correlation between high expression of bcl-2 and a low score by TUNEL (P < 0.05). These data are consistent with the notion that overexpression of bcl-2 may be linked to blockage of apoptosis-mediated death of H-RS cells in classic HL. Abnormal expression of p53-related protein may not play a major role in HL, because it is present in H-RS cells in only a minority of cases. Increased expression of Ki67 and TopoIIalpha by H-RS cells is significantly associated with advanced stage and may indicate aggressive disease. Adverse clinical outcome in HL also is associated with loss of Rb and p21 protein expression, consistent with the possible roles of Rb and p21 in inhibition of the growth of H-RS cells. Within the limitations of the methods used, almost two thirds of cases of HL provide evidence of an association with EBV. The tissue microarray technique is valuable not only for examination of large numbers of cases of a disease by a complex panel of markers but also potentially as a control for staining quality in immunohistochemistry and in situ hybridization.
...
PMID:Apoptosis and cell cycle-related genes and proteins in classical Hodgkin lymphoma: application of tissue microarray technique. 1296 46

The correlation between the histological features and clinical outcome remains poor in pediatric intracranial ependymomas. We performed a retrospective study of a group of 31 patients (diagnosed from 1985 to 1995) to assess prognostic implications of the current grading system, of histological and immunohistochemical features, and of ploidy status estimated by flow cytometry. Immunoexpression of a broad spectrum of antigens was evaluated, including MIB-1, topoisomerase-IIalpha, cyclin D1, glial and epithelial proteins (GFAP, EMA, cytokeratins), molecules involved in controlling apoptosis (bcl-2, caspase-3/CPP32), and p53 oncoprotein. Univariate and multivariate statistical analyses were performed to evaluate the influence of each variable on both the progression free survival (PFS) and the overall survival (OS) with at least 7-year follow up. Although we showed a significant correlation between histological grade and prognosis, the current grading system failed in predicting outcome in nearly one third of individual cases. Problems with interpathologist reproducibility were also demonstrated. The extent of surgical resection was the only clinical factor that was associated with survival. Both the PFS and the OS were significantly decreased for the following pathological variables: increased cellularity (>300 nuclei per HPF), mitotic activity of >7 per 10 HPF, increased MIB-1 labeling index (LI), topoisomerase-IIalpha LI, S-phase fraction, and p53 and bcl-2 positivity. Increased cyclin D1 LI was demonstrated to have only a marginally significant impact on PFS. A flow chart modeling was further performed to formulate a scheme for discriminating of prognostic subgroups. Based on that, p53 immunopositivity and/or MIB-1 LI of >5% (after subtotal resection) or MIB-1 LI of >15% (after complete resection) were the strongest indicators of the tumor's aggressive behavior and of a poor prognosis of the disease. Foci of hypercellularity should be specifically looked for in ependymomas for assessing the immunohistochemical studies.
...
PMID:Pediatric intracranial ependymomas: prognostic relevance of histological, immunohistochemical, and flow cytometric factors. 1455 80

Defects in apoptosis play a decisive role in both tumorigenesis and drug resistance in tumor treatment. The purpose of this study was to investigate the balance between formation of genomic damage and induction of apoptosis upon genotoxic stress. For this, we influenced the apoptotic response and measured the amount of genomic damage expressed as micronucleus formation after treatment with the topoisomerase II inhibitor etoposide. Apoptosis was reduced by the addition of pifithrin (PFT) alpha and enhanced by transient transfection with bcl-2 antisense-oligonucleotide in Bcl-2-overexpressing cells. We used three human lymphoblastoid cell lines with different p53 status (TK6, wild-type p53; WTK1, mutated p53; NH32, p53 double knockout). Under conditions of reduced apoptosis, micronucleus formation was also reduced. When apoptosis was increased, micronucleus formation remained unchanged or was also increased. Overall, we did not find an expected inverse correlation between induction of apoptosis and genomic damage.
...
PMID:Influence of altered apoptosis in human lymphoblastoid cell lines on micronucleus frequency. 1475 22


<< Previous 1 2 3 4 Next >>

---