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OBJECTIVE Lapachol is a natural naphthoquinone compound that possesses extensive biological activities. The aim of this study is to investigate the inhibitory effects of lapachol on rat C6 glioma both in vitro and in vivo, as well as the potential mechanisms. METHODS The antitumor effect of lapachol was firstly evaluated in the C6 glioma model in Wistar rats. The effects of lapachol on C6 cell proliferation, apoptosis and DNA damage were detected by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS)/ phenazinemethosulfate (PMS) assay, hoechst 33358 staining, annexinⅤ-FITC/PI staining, and comet assay. Effects of lapachol on topoisomerase I (TOP I) and topoi?somerase Ⅱ (TOP Ⅱ) activities were detected by TOP Ⅰ and TOP Ⅱ mediated supercoiled pBR322 DNA relaxation assays and molecular docking. TOPⅠ and TOPⅡ expression levels in C6 cells were also determined. RESULTS High dose lapachol showed significant inhibitory effect on the C6 glioma in Wistar rats (P<0.05). It was showed that lapachol could inhibit proliferation, induce apoptosis and DNA damage of C6 cells in dose dependent manners. Lapachol could inhibit the activities of both TOPⅠ and Ⅱ. Lapachol-TOPⅠ showed relatively stronger interaction than that of lapachol-TOPⅡ in molecular docking study. Also, lapachol could inhibit TOPⅡ expression levels, but not TOPⅠ expression levels. CONCLUSION These results showed that lapachol could significantly inhibit C6 glioma both in vivo and in vitro, which might be related with inhibiting TOPⅠ and TOPⅡ activities, as well as TOPⅡ expression.
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DNA topoisomerases (Tops) are essential enzymes that regulate the cellular processes such as replication , transcription ,recombination and repair .DNA Tops can be classified into two types ,topoisomerase Ⅰ (TopⅠ ) and topoi-somerase Ⅱ (TopⅡ) .They catalyze the breakage and religation of DNA ,maintaining the topological changes of DNA and va-rious DNA metabolic processes .Due to their important role in DNA metabolism ,the ability to interfere with the functions of Tops or generating Top-mediated DNA damage is an effective strategy for cancer chemotherapy .Tops have been considered as the most important targets for tumor chemotherapy .In this review ,we used examples to describe the development of dual to-poisomerase Ⅰ and Ⅱ inhibitors .
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Tyrosyl-DNA phosphodiesterase Ⅰ (TdpⅠ ) is a recently discovered proteinthat catalyzes the hydrolysis of 3′-phosphotyrosyl bonds .Such linkages form in vivo during the interaction of DNA and topoisomerase Ⅰ (TopⅠ) .TdpⅠ has been regarded as a potential therapeutic co-target of TopⅠ because it has the functions of repairing Top Ⅰ compound and coun-teracting the effects of Top Ⅰ inhibitors .TdpⅠ inhibitors can not only synergizing with Top Ⅰ-targeting drugs (camptoth-ecins) ,but also strength the function of bleomycin ,topoisomerase Ⅱ (TopⅡ ) inhibitors (etoposide ,doxorubicin) and DNA alkylating agents .We summarized the researching advance of TdpⅠ inhibitors and focused on the introduction of the mecha-nism ,bioactivity and structure-activity relationship .
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Background and purpose:The cinobufacini injection is a traditional antitumor drug.However,its mechanism iS still unclear.The purpose of this study was to observe the effect of cinobufacini injections in DNA TOPO Ⅰ of human hepatocellular carcinoma HcpG-2 cells.Methods:The cells that were proliferated were assessed by MTT assay.Cell cycles were shown through FCM.TOPO Ⅰ mRNA expression was analyzed through RT-PCR.The activity of TOPO Ⅰ was measured by TOPO Ⅰ mediated super coiled PHR322 relaxation.Supercoiled PBR322 was also used to determine the direct DNA breakages.Results:Cinobufacini injections significantly inhibited HepG-2 cells proliferation in ways that were dependent on dosages and time.Induced tumor cells arrest at the S-phase.TOPO ⅠmRNA expression decreased in a manner that was dependent on dosages which inhibited the TOPO Ⅰ mediated DNA relaxations.However,the cinobufacini injections could not directly induce DNA breakage at any concentration.Conclusion:Cinobufacini injections can inhibit human hepatocellular carcinoma HepG-2 cells proliferation.The regulation of topoisomerase Ⅰ activity and mRNA expression may be one of the mechanisms that causes the cinobufacini injection to contribute against tumor.
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9-Nitrocamptothcin(9-NC)is an orally available new type camptothecinanalog with antineoplastic activity that results from inhibition of DNA topoisomerase Ⅰ.In the study we reviewed the feature of the drug,mechanism of action,update studies of preclinical and pancreas cancer clinical trial.
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Objective To study the liver cancer specific DNA damage response/repair/recombination gene expression profile and the difference between liver cancer tissues and their adjacent normal tissues. Methods The cDNA probes labeled with ? 32 P dATP were synthesized from total RNA of cancer tissue and adjacent liver tissues. The cDNA probes were differentially hybridized to two identical Atlas human cancer cDNA expression array membranes containing 588 known genes. A gene specific semiquantitative reverse transcription polymerase chain reaction (RT PCR) method and Northern blot were used to check the expression pattern of two known genes. Results Autoradiographic result analyzed by specific Atlas Image TM (version1.01a) showed among the 588 genes analyzed, 33 genes were related to damage response/repair/recombination and the expression of 4 genes including DNA dependent protein kinase, and DNA topoisomerase Ⅰ were found to be up regulated in liver cancer. The results of RT PCR and Northern blot confirmed the expression pattern of two genes which were detected by Atlas human cancer cDNA expression array. Conclusion The result obtained from Atlas microarray provides a liver cancer specific expression profile comprehensively and systematically. The findings about genes related to DNA damage response/repair/recombination may lead to understanding of the pathogenesis of liver cancer and the mechanism of drug resistant.
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Following the realization that involved in all of the key process within the cell nucleus such as DNA replication,transcription,reorganization,repair,human DNA topoisomerase Ⅰ(Topo Ⅰ) is a useful therapeutic target against tumor growth.Topo Ⅰ inhibitors represent a class of effective agents that have been extensively exploited and used for carcinomachemotherapy.Current Topo Ⅰ inhibitors being clinically used or developed are classified as campotothecins and non-camptothecins.This presentation introduces current status and trends of Topo Ⅰ inhibitors as anti-tumor agents with an emphasis on bioactive and pharmacological properties of these agents.