Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.49 (reverse transcriptase)
 31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A camptothecin analog, ((4s)-4,11-diethyl-4-hydroxy-9-[(4- piperidinopiperidino)carbonyloxy]dione hydrochloride trihydrate), (CPT-11), is a recently developed topoisomerase I (Topo I) inhibitor which attracts the attention of clinicians because of its high antitumor activity. We established a CPT-11-resistant human ovarian cell line, HAC2/CPT, from the parental HAC2 cell line. An in vitro drug sensitivity assay revealed that HAC2/CPT was 9.7 and 4.7 times as resistant as HAC2 to CPT-11 and 7-ethyl-10-hydroxy-CPT-11 (SN-38), an active metabolite of CPT-11, respectively. HAC2/CPT showed no cross-resistance to other drugs tested (adriamycin, etoposide, cisplatin and Taxol), suggesting that HAC2/CPT acquired a phenotype specifically resistant to the Topo I inhibitor. In order to elucidate the mechanism of the resistance, we measured Topo I activity of HAC2 and HAC2/CPT. The activity of Topo I of HAC2/CPT was reduced to half of that of the parental HAC2 cells. To determine the cause of the decreased activity of Topo I, the mutation of the Topo I gene was searched for by the polymerase chain reaction and the reverse transcriptase analysis. Topo I gene mutation was not detected. The amount of Topo I protein was measured by immunoblotting and a marked decrease of Topo I protein was observed in HAC2/CPT. These results suggest that the decreased protein content of Topo I causes the decreased activity of Topo I and the decreased sensitivity of HAC2/CPT to Topo I inhibitors.
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PMID:Establishment of a CPT-11-resistant human ovarian cancer cell line. 807 81

Esophagitis is a major toxicity of radiation therapy for nonsmall-cell lung cancer. Intraesophageal injection of manganese superoxide dismutase (MnSOD) plasmid/liposome complexes (1 mg of the pRK5-MnSOD plasmid containing the human MnSOD transgene in a 0.15 ml volume of lipofectin) before irradiation was carried out to attempt to prevent irradiation esophagitis. In control noninjected male C3H/HeNsd mice, esophagitis was induced by single fraction 3,500 cGy irradiation. Histopathology at 4 days revealed vacuole formation in squamous lining cells, separation of the squamous layer from the underlying muscle layer, ulceration at 7 days, and dehydration and death by 30 days. MnSOD plasmid/liposome complex-injected mice showed transcription of the human MnSOD transgene message in esophageal squamous lining cells by nested reverse transcriptase-polymerase chain reaction (RT-PCR) increased MnSOD biochemical activity 24 h after injection, decreased vacuole formation at day 4 (P < 0.001) after 3,500 cGy thoracic irradiation, and improved survival (P = 0.0009). In contrast, groups of mice receiving LacZ (bacterial beta-galactosidase gene) plasmid/liposome complexes or liposomes containing no DNA before 3,500 cGy irradiation showed an unaltered irradiation histopathology and decreased survival. Mice receiving intraesophageal MnSOD plasmid/liposomes followed 8 h later by human equivalent doses of Taxol (1.4 mg/kg) and carboplatin (2.5 mg/kg), then 15 h later 3,300 cGy irradiation, showed increased survival, compared with irradiated control or LacZ plasmid/liposome groups. Thus, overexpression of the human MnSOD transgene in the esophagus can prevent irradiation-induced esophagitis in the mouse model.
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PMID:Prevention of irradiation-induced esophagitis by plasmid/liposome delivery of the human manganese superoxide dismutase transgene. 1049 61

We compared the effects of paclitaxel (Taxol) in human renal cell carcinoma (RCC) of different histologic types. The growth inhibitory effects of paclitaxel on 34 human RCC cell lines of strictly defined different histologic types were determined by 3-[4,5-dimethylthiazolyl]-2,5-diphenyltetrazoliumbromide (MTT) assays. Paclitaxel-induced morphologic alterations were visualized by light and immunofluorescence and by transmission electron microscopy. The expression and function of P-glycoprotein and multidrug resistance-associated protein (MRP) were defined by reverse transcriptase polymerase chain reaction and fluorescence-activated cell sorting (FACS) analysis, respectively. Modulation of P-glycoprotein function was performed by verapamil or Cremophor EL. A significant (p < 0.05) dose-dependent paclitaxel-induced growth inhibition could be demonstrated in all cell lines, with the effects of paclitaxel dissolved in Cremophor EL/ethanol (= Taxol) exceeding the effects of paclitaxel dissolved in dimethyl sulfoxide. The extent of response markedly varied between the different cell lines, although chromophilic RCCs exhibited a more pronounced response to Taxol (IC50: 0.03-0.38 microM) than clear cell RCCs (IC50: 0.01-36.69 microM). Exposure to paclitaxel/Taxol induced an increase of microtubule bundles in the clear cell and the chromophobe RCCs but not in the chromophilic RCCs. The expression of the MRP was low in RCC cell lines and was not found to be related to paclitaxel/Taxol sensitivity. In contrast, the expression level of P-glycoprotein was much more pronounced and showed a positive correlation (p < 0.05) with the response to paclitaxel. Reversal of P-glycoprotein function by verapamil or Cremophor EL enhanced the growth inhibitory effects of paclitaxel and further supported the role of P-glycoprotein for paclitaxel sensitivity of human RCCs. Paclitaxel/Taxol effectively inhibits proliferation of human RCCs in vitro, irrespective of their histologic types. Moreover, expression and function of P-glycoprotein markedly contribute to paclitaxel responsiveness, although other as yet undefined drug resistance mechanisms are effective in human RCCs as well.
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PMID:Multidrug resistance phenotype and paclitaxel (Taxol) sensitivity in human renal carcinoma cell lines of different histologic types. 1103 69

Analyses of CYP1A1 mRNA were used to monitor the responsiveness of murine hepatoma 1c1c7 and human monocytic U937 cells in different phases of the cell cycle to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Concentrations of TCDD capable of inducing CYP1A1 were not cytostatic to either cell line. Steady-state CYP1A1 mRNA contents were reduced (45-90%) in TCDD-treated cultures arrested in G2/M as a consequence of exposure to microtubule disrupters (Colcemid, estramustine, vinblastine) or the microtubule stabilizer Taxol, relative to TCDD-treated asynchronous 1c1c7 cultures. The accumulation of mRNAs corresponding to Nmo1, another TCDD-inducible gene of the Ah battery, was also reduced in TCDD-treated G2/M cultures. Quantitative reverse transcriptase-polymerase chain reaction analyses of CYP1A1 heterogeneous nuclear RNA (hnRNA) revealed that Cyp1a1 transcription was suppressed in G2/M cells. This suppression reflected neither changes in the relative content of the proteins comprising the aryl hydrocarbon receptor (AHR) complex nor a suppression of AHR activation and translocation to the nucleus. Release of 1c1c7 cultures arrested in G2/M restored TCDD responsiveness. Centrifugal elutriation of TCDD-treated asynchronously growing U937 cells was used to prepare populations of cells in specific phases of the cell cycle. Within 3 h of TCDD exposure late G1/early S phase cells had CYP1A1 mRNA contents approximately 1.4- and 3-fold higher than the contents of asynchronous/early G1 and G2/M cultures, respectively. These studies suggest that the transcriptional activation of members of the Ah battery by TCDD is cell cycle-dependent, and markedly suppressed in G2/M cells.
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PMID:Regulation of Cyp1a1 induction by dioxin as a function of cell cycle phase. 1160 86

Six human alpha-tubulin and seven human beta-tubulin isotypes, each of which can undergo posttranslational modifications, have been detected by the reverse transcriptase-polymerase chain reaction. This repertoire of tubulin isotypes plays a role in development and in the building of specialized microtubule-based structures. In cell lines, the relationship between resistance to microtubule-interacting drugs and altered tubulin isotype expression profiles is often established by quantitation of cDNA and/or Western blot analysis. Tubulin mutations in major isotypes are detected by sequencing cDNA, but more analysis of expression of tubulin mutations at the protein level, to assess their role in drug resistance, is needed. We utilized a Taxol-based purification and high-resolution isoelectrofocusing combined with a mass spectrometry-based analysis of tubulin. This approach has allowed the separation and relative quantitation of tubulin isotypes having a difference in isoelectric point values of 0.01, without the need for two-dimensional gel electrophoresis. The specificity of tubulin isotype antibodies also has been established. In cell lines resistant to microtubule-stabilizing drugs that express heterozygous tubulin mutations, the relative amount of mutant tubulin expression has been determined. In these cell lines, the absence of betaII- and betaIVa-tubulin has been demonstrated, and an increased level of expression of betaIII-tubulin in resistant cells has been confirmed, indicating that this tubulin isotype is a unique marker of resistance.
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PMID:Analysis of tubulin isotypes and mutations from taxol-resistant cells by combined isoelectrofocusing and mass spectrometry. 1273 76

Hyaluronan (HA) is a major glycosaminoglycan in the extracellular matrix whose expression is tightly linked to multidrug resistance and tumor progression. In this study we investigated HA-induced interaction between CD44 (a HA receptor) and Nanog (an embryonic stem cell transcription factor) in both human breast tumor cells (MCF-7 cells) and human ovarian tumor cells (SK-OV-3.ipl cells). Using a specific primer pair to amplify Nanog by reverse transcriptase-PCR, we detected the expression of Nanog transcript in both tumor cell lines. In addition, our results reveal that HA binding to these tumor cells promotes Nanog protein association with CD44 followed by Nanog activation and the expression of pluripotent stem cell regulators (e.g. Rex1 and Sox2). Nanog also forms a complex with the "signal transducer and activator of transcription protein 3" (Stat-3) in the nucleus leading to Stat-3-specific transcriptional activation and multidrug transporter, MDR1 (P-glycoprotein) gene expression. Furthermore, we observed that HA-CD44 interaction induces ankyrin (a cytoskeletal protein) binding to MDR1 resulting in the efflux of chemotherapeutic drugs (e.g. doxorubicin and paclitaxel (Taxol)) and chemoresistance in these tumor cells. Overexpression of Nanog by transfecting tumor cells with Nanog cDNA stimulates Stat-3 transcriptional activation, MDR1 overexpression, and multidrug resistance. Down regulation of Nanog signaling or ankyrin function (by transfecting tumor cells with Nanog small interfering RNA or ankyrin repeat domain cDNA) not only blocks HA/CD44-mediated tumor cell behaviors but also enhances chemosensitivity. Taken together, these findings suggest that targeting HA/CD44-mediated Nanog-Stat-3 signaling pathways and ankyrin/cytoskeleton function may represent a novel approach to overcome chemotherapy resistance in some breast and ovarian tumor cells displaying stem cell marker properties during tumor progression.
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PMID:Hyaluronan-CD44 interaction activates stem cell marker Nanog, Stat-3-mediated MDR1 gene expression, and ankyrin-regulated multidrug efflux in breast and ovarian tumor cells. 1844 25

Target identification remains a major challenge for modern drug discovery programs aimed at understanding the molecular mechanisms of drugs. Computational target prediction approaches like 2D chemical similarity searches have been widely used but are limited to structures sharing high chemical similarity. Here, we present a new computational approach called chemical similarity network analysis pull-down 3D (CSNAP3D) that combines 3D chemical similarity metrics and network algorithms for structure-based drug target profiling, ligand deorphanization, and automated identification of scaffold hopping compounds. In conjunction with 2D chemical similarity fingerprints, CSNAP3D achieved a >95% success rate in correctly predicting the drug targets of 206 known drugs. Significant improvement in target prediction was observed for HIV reverse transcriptase (HIVRT) compounds, which consist of diverse scaffold hopping compounds targeting the nucleotidyltransferase binding site. CSNAP3D was further applied to a set of antimitotic compounds identified in a cell-based chemical screen and identified novel small molecules that share a pharmacophore with Taxol and display a Taxol-like mechanism of action, which were validated experimentally using in vitro microtubule polymerization assays and cell-based assays.
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PMID:3D Chemical Similarity Networks for Structure-Based Target Prediction and Scaffold Hopping. 2728 61