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PubMed2005

[Reverse effect of genetically modified adenovirus H101 on drug-resistance of A549/DDP cells to cisplatin].

BACKGROUND & OBJECTIVE: Multidrug resistance is one of the main causes of treatment failure of chemotherapy. Reversal agents may be used to reverse drug-resistance. To date, no appropriate reversal agent is used clinically. This study was to evaluate reverse effect of genetically modified adenovirus H101 on drug-resistance of A549/DDP cells to cisplatin (DDP), and to explore its mechanisms. METHODS: Lung adenocarcinoma cell line A549 and its DDP-resistant cell line A549/DDP were treated with DDP and H101. Reverse effect of H101 on drug-resistance of A549/DDP to DDP was tested by MTT assay. The levels of cellular multidrug resistant protein 1 (MRP1), glutathione-S-transferase (GST), and topoisomerase-II (TOPO-II) were detected by flow cytometry (FCM). The level of intracellular glutathione (GSH) was measured by fluorescence-Coomassie light blue method. The intracellular concentration of platinum was measured by atomic absorption spectrometry. RESULTS: The resistance index of A549/DDP cells to DDP was 14.3. After infection of H101, the 50% inhibitory concentration (IC(50)) of DDP to A549/DDP cells reduced from 352.4 micromol/L to 61.6 micromol/L by 5.7 folds. Protein levels of GST and TOPO-II were higher in A549/DDP cells than in A549 cells, which were markedly decreased in A549/DDP cells after infection of H101. No MRP1 protein was detected in both A549 cells and A549/DDP cells. Intracellular amount of GSH in A549/DDP cells was 2 times higher than that in A549 cells, which was significantly decreased after infection of H101. The concentration of platinum in A549 cells was 3 times higher than that in A549/DDP cells. After infection of H101, the concentration of platinum in A549 cells had no significant change, but that in A549/DDP cells was significantly increased. CONCLUSION: H101 may reverse drug-resistance of A549/DDP cells to DDP through down-regulating GST and TOPO-IIand increasing intracellular cumulation of platinum.

Adenocarcinoma↗

PubMed2006

Gene-specific effects of antisense phosphorodiamidate morpholino oligomer-peptide conjugates on Escherichia coli and Salmonella enterica serovar typhimurium in pure culture and in tissue culture.

The objective was to improve efficacy of antisense phosphorodiamidate morpholino oligomers (PMOs) by improving their uptake into bacterial cells. Four different bacterium-permeating peptides, RFFRFFRFFXB, RTRTRFLRRTXB, RXXRXXRXXB, and KFFKFFKFFKXB (X is 6-aminohexanoic acid and B is beta-alanine), were separately coupled to two different PMOs that are complementary to regions near the start codons of a luciferase reporter gene (luc) and a gene required for viability (acpP). Luc peptide-PMOs targeted to luc inhibited luciferase activity 23 to 80% in growing cultures of Escherichia coli. In cell-free translation reactions, Luc RTRTRFLRRTXB-PMO inhibited luciferase synthesis significantly more than the other Luc peptide-PMOs or the Luc PMO not coupled to peptide. AcpP peptide-PMOs targeted to acpP inhibited growth of E. coli or Salmonella enterica serovar Typhimurium to various extents, depending on the strain. The concentrations of AcpP RFFRFFRFFXB-PMO, AcpP RTRTRFLRRTXB-PMO, AcpP KFFKFFKFFKXB-PMO, and ampicillin that reduced CFU/ml by 50% after 8 h of growth (50% inhibitory concentration [IC(50)]) were 3.6, 10.8, 9.5, and 7.5 microM, respectively, in E. coli W3110. Sequence-specific effects of AcpP peptide-PMOs were shown by rescuing growth of a merodiploid strain that expressed acpP with silent mutations in the region targeted by AcpP peptide-PMO. In Caco-2 cultures infected with enteropathogenic E. coli (EPEC), 10 microM AcpP RTRTRFLRRTXB-PMO or AcpP RFFRFFRFFXB-PMO essentially cleared the infection. The IC(50) of either AcpP RTRTRFLRRTXB-PMO or AcpP RFFRFFRFFXB-PMO in EPEC-infected Caco-2 culture was 3 microM. In summary, RFFRFFRFFXB, RTRTRFLRRTXB, or KFFKFFKFFXB, when covalently bonded to PMO, significantly increased inhibition of expression of targeted genes compared to PMOs without attached peptide.

Bacterial Proteins↗

PubMed2003

Lamivudine can exert a modest antiviral effect against human immunodeficiency virus type 1 containing the M184V mutation.

The M184V mutation in human immunodeficiency virus (HIV) reverse transcriptase is associated with high-level resistance to both (-)2',3'-dideoxy-3'-thiacytidine (3TC) and (-)2',3'-dideoxy-5-fluoro-3'-thiacytidine as well as low-level resistance to 2',3'-dideoxyinosine, 2',3'-dideoxycytidine, and abacavir. This mutation is also associated with diminished HIV replicative fitness as well as several functional changes in enzyme activity, including diminutions in polymerase processivity, pyrophosphorylysis, and nucleotide primer unblocking. Despite the fact that M184V encodes up to 1,000-fold resistance to 3TC, we asked whether this drug might still display some antiviral effect in regard to viruses containing this mutation. Cell-free assays revealed that high concentrations of 3TC triphosphate (i.e., >100 micro M) could affect chain termination and/or inhibit purified reverse transcriptase containing the M184V substitution. This effect became more pronounced with elongation of reverse transcriptase products. In newly infected cells (i.e., peripheral blood mononuclear cells), we found that the amount of full-length reverse transcriptase product was diminished in the presence of 2 to 10 micro M 3TC, although no decrease in the first product of the reverse transcriptase reaction, i.e., minus strong-stop DNA, was observed. In the presence of two other HIV inhibitors, e.g., nevirapine and indinavir, 3TC exerted additive effects in tissue culture at concentrations only marginally higher than the 50% inhibitory concentration (IC(50)). Reverse transcriptases cloned from clinical isolates harboring M184V in the context of multidrug resistance had similar IC(50) values for 3TC triphosphate compared to reverse transcriptase containing only the M184V mutation. These results suggest that viruses containing M184V can retain a higher degree of sensitivity to 3TC than previously assumed.

HIV Reverse Transcriptase↗

PubMed2001

Comparison of minimum inhibitory concentration values for fluoroquinolones against Escherichia coli causing urinary tract infection in both hospitalized patients and outpatients.

OBJECTIVE: To determine the resistance among Escherichia coli isolates causing urinary tract infections in hospitalized patients and outpatients. METHODS: This study was carried out in the Department of Microbiology, Dokuz Eylul University, Medical Faculty Hospital, Inciralti, Ismir, Turkey, from February 1997 through to June 1998. A total of 300 Escherichia coli strains were isolated from urine specimens of 111 hospitalized and 189 elderly outpatients (more than 20 years of age). We determined the minimum inhibitory concentrations of the test drugs nalidixic acid, pefloxacin, ofloxacin, norfloxacin and ciprofloxacin by the microdilution method, recommended by the National Committee for Clinical Laboratory Standards. RESULTS: Minimum inhibitory concentrations(50) and minimum inhibitory concentrations(90) values of strains tested against fluoroquinolones, pefloxacin and nalidixic acid were the same for strains isolated from hospitalized and outpatients (0.125 microg/ml outpatients (0.03 microg/ml). Twenty-six (9%) of 300 Escherichia coli strains were resistant to all drugs used. Twenty (77%) of these 26 strains were isolated from hospitalized patients. We found that the resistance to nalidixic acid is much higher than other fluoroquinolones. At the same time, the resistance in the strains that were isolated from hospitalized patients is again higher than outpatient strains (46%). CONCLUSION: Resistance among Escherichia coli isolates from patients to quinolones used in the treatment of urinary tract infections was rare during this period. Our study, like many other reports showed the increased resistance to fluoroquinolones for clinical isolates. However the appearance of multi resistant clones and the elevated prevalence of quinolones resistance in the hospital studied are warning signals for an increase in resistant strains as seen in many other countries. Therefore, it is important for physicians to use fluoroquinolones carefully so as to prevent, or delay, the emergence of resistant strains.

Ambulatory Care↗

PubMed1998

Antimicrobial susceptibility patterns of fungi isolated from horses with ulcerative keratomycosis.

OBJECTIVES: To evaluate in vitro susceptibility to topical antifungal medications, as measured by minimum inhibitory concentration (MIC) and 50% inhibitory concentration (IC50%), of fungal isolates from horses with ulcerative keratomycosis in Florida; to compare results with those of other studies to identify differences in susceptibility patterns among fungi isolated from horses in different geographic regions; and to note indications of fungal resistance to drugs tested in other studies. SAMPLE POPULATION: Corneal fungal cultures from client-owned horses from Florida with ulcerative keratomycosis (n = 22). PROCEDURE: Fungal cultures were plated on Emmons modified Sabouraud dextrose agar and mycobiotic agar, examined weekly for growth, and kept for a total of 30 days. In vitro MIC and IC50% of fluconazole, itraconazole, ketoconazole, miconazole, and natamycin were measured for each fungal isolate. RESULTS: Aspergillus (n = 9; 41%), Fusarium (7; 32%), Penicillium (2; 9%), Cylindrocarpon (1; 4%), Scytalidium (1; 4%), and Torulopsis (1; 4%) spp and an unidentified yeast (1; 4%) were isolated. Fungi were most susceptible to antifungal drugs in the following order: natamycin and miconazole equally, itraconazole, and ketoconazole, although no significant difference was found among drugs. Fungi were significantly less susceptible to fluconazole (P < 0.0001) than to the other 4 drugs. CONCLUSIONS: Initial antifungal therapy with topically applied natamycin, miconazole, itraconazole, or ketoconazole is recommended for ulcerative keratomycosis in horses in the subtropical environment of Florida. CLINICAL RELEVANCE: Specific antifungal treatment of horses with ulcerative keratomycosis should be based on history, results of ophthalmic examination, cytologic findings, isolation of the pathogenic fungus, and known prevalence of unique ocular fungi in specific geographic areas. In vitro antifungal susceptibility testing may be most beneficial in aiding documentation of pharmacologic susceptibility patterns of fungi in specific geographic regions.

Analysis of Variance↗

PubMed2006

Effects of p73 gene overexpression on apoptosis and chemosensitivity of human lung adenocarcinoma cell line A549.

BACKGROUND & OBJECTIVE: It is important to overcome gene therapy resistance caused by wt-p53 in non-small cell lung cancer (NSCLC) . The p53 family member p73 is a p53 homolog. This study was to observe the apoptosis and chemosensitivity effect of p53-resistant human lung adenocarcinoma cell line A549 following wild-type p73 gene transfection alone or combined with chemotherapeutic agents. METHODS: Plasmids pcDNA3-HA-p53 or pcDNA3-HA-p73alpha were transfected into A549 cells with Dosper. Positive cell clones were selected using G418. The exogenous p53 or p73alpha gene expressions were examined by Western blot. MTT assay was used to analyze the response of transfected cells to cisplatin (DDP) or adriamycin (ADM). The drug-induced apoptosis of transfected cells was measured by flow cytometry, TUNEL technique and DNA fragmentation. The biological behavior change of transfected cells was investigated by colony formation assay. RESULTS: Transfected A549 cells stably overexpressed p53 or p73alpha. Low concentration of chemotherapeutic agents (6.25 micromol/L DDP or 0.25 micromol/L ADM) which had no obvious effects on non-transfected cells, suppressed p73-transfected cell growth significantly; the 50% inhibitory concentration (IC(50)) of DDP for A549 cells decreased from 22.65 micromol/L to 3.75 micromol/L, and the IC(50) of ADM decreased from 4.20 micromol/L to 0.06 micromol/L after p73alpha transfection. p73, but not p53, sensitized A549 cells to DDP and ADM: DDP-induced apoptosis rate was increased from 10.6% to 36.8% (P<0.01), ADM-induced apoptosis rate was increased from 13.0% to 41.1% (P<0.01) after p73 transfection. DDP and ADM significantly suppressed colony formation of p73-transfected cells compared with parental cells (P<0.01). The sensitive enhancement ratios for DDP and ADM were 2.0 and 2.4, respectively. CONCLUSIONS: Exogenous p73 gene enhances the sensitivity of A549 cells to chemotherapeutic agents by inducing apoptosis through p53-independent pathway. p73 gene could be used to treat p53-resistant tumors.

Adenocarcinoma↗

PubMed1990

5-Fluorouracil enhances azidothymidine cytotoxicity: in vitro, in vivo, and biochemical studies.

Preliminary in vitro studies suggest that the combination of 5-fluorouracil (FUra) and 3'-azido-3'-deoxythymidine (AZT) is more cytotoxic than either agent alone. Therefore, a biochemical and therapeutic evaluation of this combination was initiated. Quantitation of the cytotoxicity of FUra plus AZT against the growth of HCT-8 cells in vitro revealed that 1 microM FUra (approximately 10% inhibitory concentration) increased the cytotoxicity of AZT and decreased its 50% inhibitory concentration by 60%. Similarly, incubating HCT-8 cells in 5 microM AZT (approximately 10% inhibitory concentration) decreased the 50% inhibitory concentration of FUra by over 50%. Biochemical analysis indicated that AZT did not affect FUra-induced inhibition of thymidylate synthase or [3H]-FUra incorporation into nucleic acids. In contrast, incubation in 5 microM FUra increased the incorporation of [3H]-AZT (5 microM) into the nucleic acid fraction of these cells by 52% (P less than 0.05). Therapeutic evaluation of this combination in athymic (nude) mice bearing HCT-8 xenographs revealed that, while weekly FUra (85 mg/kg) or AZT (600 mg/kg) exerts minimal antineoplastic activity (after 4 courses, treatment/control = 0.81 and 0.70, respectively), their combination, at the same doses, inhibited tumor growth by nearly 70% (P less than 0.01 versus FUra alone). FUra-related host toxicity was not increased by the addition of AZT. Higher doses of FUra alone were not more effective than FUra plus AZT. In vivo, AZT did not affect the incorporation of [3H]-FUra into the nucleic acid fraction of various murine tissues, including HCT-8 xenografts. FUra, however, increased [3H]-AZT incorporation into nucleic acids in a tissue-specific manner. In the presence of FUra, the incorporation of [3H]-AZT in spleen, liver, and gut increased 40, 21, and 4%, respectively, while in HCT-8 xenografts [3H]-AZT incorporation increased more than 2-fold. Analysis of the activities of selected enzymes involved in pyrimidine metabolism suggests that this tissue-specific effect may be related to the pyrimidine salvage capacity of these tissues. These findings are described in light of their potential impact on human colon cancer chemotherapy.

Animals↗

PubMed2002

Cytotoxic activity of amooranin and its derivatives.

Amooranin, 25-hydroxy-3-oxoolean-12-en-28-oic acid, is a triterpene acid isolated from Amoora rohituka stem bark. The cytotoxic effects of amooranin and its derivatives were studied. Amooranin and its methyl ester showed greater cytotoxicity against MCF-7 and HeLa cells derived from tumour tissues with a 50% inhibitory concentration (IC(50)) of 1.8-3.4 microg/mL, compared with Chang liver cells from normal tissue with an IC(50) of 6.2-6.4 microg/mL, but amooranin exhibited no activity on HEp-2 and L-929 cells. However, its monoacetate derivative showed no inhibitory activity at 1-10 microg/mL dose levels. Of the cytotoxic isolates, the methyl ester derivative was inactive in in vivo evaluations in the Ehrlich ascites tumour cells at 50 and 100 mg/kg/day, demonstrating T/C values of 106% and 114%, respectively.

Animals↗

PubMed2001

Inhibitory activity of quinolones against DNA gyrase of Mycobacterium tuberculosis.

The in vitro inhibitory activities of quinolones against Mycobacterium tuberculosis DNA gyrase were measured. The 50% inhibitory concentrations (IC(50)s) of sitafloxacin (DU-6859a), sparfloxacin, ciprofloxacin and levofloxacin against supercoiling activity of DNA gyrase were 1.67, 4.80, 12.2 and 13.9 mg/L, respectively, and correlated well with their MICs. Two altered proteins of GyrA containing Ala-90Val, or Ala-90Val and Asp-94Gly were also purified and the inhibitory activities of the quinolones ranged from 12 to >83 times weaker than those against the wild-type enzyme. These results suggest that mutations in the corresponding genes confer quinolone resistance.

4-Quinolones↗

PubMed1990

Increased sensitivity to Vinca alkaloids in cells overexpressing calmodulin by gene transfection.

Mouse C127 cells, transfected with the chicken calmodulin (CaM) gene and overexpressing CaM protein, were used to evaluate the effect of elevated levels of CaM on the sensitivity of these cells to various anticancer drugs. Clones C2 and C3 overexpress CaM mRNA by 40- and 80-fold, respectively, and CaM protein 3- and 8-fold, respectively. These cell lines were tested for their sensitivity to vincristine, vinblastine, bleomycin, and Adriamycin by comparing the 50% inhibitory concentration in a 72-h growth inhibition assay. The 50% inhibitory concentration values for vincristine with C2 and C3 cells were 6.27 +/- 0.56 nM and 6.60 +/- 0.96 nM, respectively. These values were significantly lower than 13.9 +/- 0.79 nM for the parental C127 cells and 14.0 +/- 1.55 nM for clone 6.8 (the control cell line for transfection without the chicken CaM gene) at P less than or equal to 0.005. The proliferation of C2 and C3 cells was inhibited at lower concentrations of vinblastine as well. The 50% inhibitory concentration values for the C2 and C3 cell lines were approximately one-half those required for C127 or clone 6.8 cells. However, no significant difference in the sensitivity to the DNA-binding drugs, bleomycin and Adriamycin, was observed between the different cell lines. The uptake of [3H]vinblastine was evaluated and found to be increased 1.6- and 2.8-fold in C2 and C3 cells, respectively, as compared with that value obtained for C127 cells. Moreover, the efflux of [3H]vinblastine from vinblastine-loaded cells was also observed to be decreased in the C2 and C3 cell lines. These data suggest that the increase in CaM expression in the C2 and C3 cell lines might be related to the higher sensitivity of these cells to Vinca alkaloids. This increased sensitivity appears to be due to the increase in intracellular concentration of the Vinca alkaloids as a result of an increase in drug uptake and a decrease in efflux. Moreover, the increased sensitivity of clones C2 and C3 to Vinca alkaloids appears to be specific to this class of drugs in that no collateral effects were observed for the DNA-damaging drugs, Adriamycin and bleomycin.

Animals↗

PubMed2005

Benzo[1,2-c]1,2,5-oxadiazole N-oxide derivatives as potential antitrypanosomal drugs. Part 3: Substituents-clustering methodology in the search for new active compounds.

The results of a study on the use of Hansch's series design, cluster methodology, for the generation of new benzo[1,2-c]1,2,5-oxadiazole N-oxide derivatives as antitrypanosomal compounds are described. In vitro activity of these compounds was tested against Tulahuen 2 strain of Trypanosoma cruzi. Clearly, the Hansch methodology allowed identifying two cluster-substituents suitable for further structural modifications. The most effective drugs, derivatives 11, 18, and 21, with 50% inhibitory concentration (IC(50)) of the same order as that of the reference drug, represent an excellent structural point of chemical modifications for the design of future drugs. Preliminary results from the study of the mechanism of action of these benzofuroxans point to perturbation of the mitochondrial electron chain, inhibiting parasite respiration.

Animals↗

PubMed2001

Inhibition of ganciclovir-susceptible and -resistant human cytomegalovirus clinical isolates by the benzimidazole L-riboside 1263W94.

The average 50% inhibitory concentration (IC(50)) values for AD169 were 0.22 +/- 0.09 microM 1263W94 and 5.36 +/- 0.12 microM ganciclovir. For 35 human cytomegalovirus (HCMV) clinical isolates the average IC(50) was 0.42 +/- 0.09 microM 1263W94, and for 26 ganciclovir-susceptible HCMV clinical isolates the average IC(50) was 3.78 +/- 1.62 microM ganciclovir. Nine HCMV clinical isolates that were resistant to ganciclovir were completely susceptible to 1263W94.

Anti-HIV Agents↗

PubMed2000

Inhibition of inositol phosphorylceramide synthase by aureobasidin A in Candida and Aspergillus species.

Inositol phosphorylceramide (IPC) synthase is an enzyme common to fungi and plants that catalyzes the transfer of phosphoinositol from phosphatidylinositol to ceramide to form IPC. The reaction is a key step in fungal sphingolipid biosynthesis and the target of the antibiotics galbonolide A, aureobasidin A, and khafrefungin. As a first step toward understanding the antifungal spectrum of IPC synthase inhibitors, we examined the sensitivity of IPC synthase to aureobasidin A in membrane preparations of Candida species (Candida albicans, C. glabrata, C. tropicalis, C. parapsilosis, and C. krusei) and Aspergillus species (Aspergillus fumigatus, A. flavus, A. niger, and A. terreus). As expected, preparations from the five Candida species, all exquisitely susceptible to aureobasidin A (MICs, <2 microgram/ml), had IPC synthase activity (specific activity, 50 to 400 pmol/min/mg of protein) sensitive to aureobasidin A (50% inhibitory concentrations [IC(50)s], 2 to 4 ng/ml). Surprisingly, preparations from the four Aspergillus species, including A. fumigatus and A. flavus, which are intrinsically resistant to aureobasidin A (MICs, >50 microgram/ml), had IPC synthase activity (specific activity, 1 to 3 pmol/min/mg of protein) also sensitive to aureobasidin A (IC(50)s, 3 to 5 ng/ml). The mammalian multidrug resistance modulators verapamil, chlorpromazine, and trifluoperazine lowered the MIC of aureobasidin A for A. fumigatus from >50 microgram/ml to 2 to 3 microgram/ml, suggesting that the resistance of this major fungal pathogen is the result of increased efflux.

Antifungal Agents↗

PubMedDate not supplied

Lack of correlation between in vitro susceptibility to Benznidazole and phylogenetic diversity of Trypanosoma cruzi, the agent of Chagas disease.

Chagas disease remains an important health problem in Central and South America. Nitroimidazole derivative drugs like Benznidazole are commonly used to treat Trypanosoma cruzi infection. Natural variation of drug susceptibility between various T. cruzi stocks has been proposed as a possible explanation of treatment failure. Thus, the aim of this work was to determine potential correlations between in vitro Benznidazole susceptibility of different T. cruzi stocks and their genetic diversity. For this purpose, 16 natural stocks representing the overall genetic diversity of the parasite were analysed. Genetic characterisation was assessed by both random amplified polymorphic DNA (RAPD) and multilocus enzyme electrophoresis (MLEE) analyses. Drug activity was determined by two complementary methods, the MTT-PMS micro-method and FACs analysis. The 50% inhibitory concentrations (IC(50)s) were determined. Important variation of IC(50) values (7.3-16.9 microM) among stocks belonging to different discrete typing units (DTUs) was recorded. Further, correlation analysis showed that natural susceptibility to Benznidazole in T. cruzi expressed as IC(50) level was not related with its genetic structure represented by the different DTUs. These results are discussed in relation with the proposed hypothesis establishing a link between genetic diversity and biological behaviour in T. cruzi.

Analysis of Variance↗

PubMed2003

Antiallergic activity of ginseng and its ginsenosides.

In this study, we measured the antiallergic activities of ginsenosides isolated from the root of Panax ginseng ( Araliaceae), and of their metabolites, as produced by human intestinal bacteria. Compound K, which was identified as a main metabolite, had the most potent inhibitory activity on beta-hexosaminidase release from RBL-2H3 cells and on the PCA reaction. The inhibitory activity of compound K was more potent than that of disodium cromoglycate, one of the commercial anti-allergic drugs. This compound demonstrated a membrane stabilizing action on differential scanning calorimetry. However, compound K did not inhibit the activation of hyaluronidase and did not scavenge active oxygen. These results suggest that the antiallergic action of compound K originates from its cell membrane stabilizing activity and that the ginsenosides of ginseng are prodrugs with extensive antiallergic properties. Abbreviations. compound K:20- O-beta- D-glucopyranosyl-20( S)-protopanaxadiol DNP:dinitrophenol DSCG:disodium cromoglycate DPPC:dipalmitoylphosphatidylcholine DPPH:1,1-diphenyl-2-picrylhydrazyl HSA:human serum albumin IC 50 :50% inhibitory concentration EC 50 :50% effective concentration XOD:xanthine oxidase ICR:Institute of Cancer Research PBS:phosphate buffered saline PCA:passive cutaneous anaphylaxis RAW264.7:mouse monocyte leukemiaRBL-2H3: rat basophil leukemia SD:Sprague-Dawley

Administration, Oral↗

PubMed2000

EBV DNA polymerase inhibition of tannins from Eugenia uniflora.

Nasopharyngeal carcinoma (NPC) is one of the high population malignant tumors among Chinese in southern China and southeast Asia. Epstein-Barr virus (EBV) is a human B lymphotropic herpes virus which is known to be closely associated with NPC. EBV DNA polymerase is a key enzyme during EBV replication and is measured by its radioactivity. The addition of phorbol 12-myristate 13-acetate to Raji cell cultures led to a large increase in EBV DNA polymerase, which was purified by sequential DEAE-cellulose, phosphocellulose and DNA-cellulose column chromatography. Four tannins were isolated from the active fractions of Eugenia uniflora L., which were tested for the inhibition of EBV DNA polymerase. The results showed the 50% inhibitory concentration (IC(50)) values of gallocatechin, oenothein B, eugeniflorins D(1) and D(2) were 26.5 62.3, 3.0 and 3.5 microM, respectively. Furthermore, when compared with the positive control (phosphonoacetic acid), an inhibitor of EBV replication, the IC(50) value was 16.4 microM. In view of the results, eugeniflorins D(1) and D(2) are the potency principles in the inhibition of EBV DNA polymerase from E. uniflora.

Carcinogens↗

PubMed2000

Topoisomerase I-mediated antiproliferative activity of enantiomerically pure fluorinated homocamptothecins.

Homocamptothecin (hCPT) is an E-ring modified camptothecin (CPT) analogue bearing a methylene spacer between the alcohol and carboxyl functions of the CPT lactone. Combining pronounced inhibitory activity of topoisomerase I (Topo I) with enhanced plasma stability, hCPT constitutes an attractive template for the elaboration of new anticancer agents. Fluorinated hCPT analogues, prepared in enantiomerically pure form, were assayed by their stimulation of Topo I-mediated DNA cleavage. Translation into cytotoxicity against tumor cells was evaluated on HT29 human colon adenocarcinoma and on the multidrug resistant lung and bladder tumor cell lines, A549 and T24r. Good correlation is observed between the ability of the drugs to stimulate Topo I-mediated DNA cleavage and the respective 50% inhibitory concentrations (IC(50) values) of the HT29, A549, and T24r cell growth. Fluorine substitution in the A-ring of hCPT was found to have a pronounced influence on biological activity, providing several compounds which are up to 100-fold more potent than CPT in terms of IC(50). Among these, 10,11-difluoro-hCPT has been selected for further development.

Antineoplastic Agents↗

PubMed2004

[Establishment of tumor cell membrane model and screening for specific anti-tumor peptides].

BACKGROUND & OBJECTIVE: Some polypeptides have targeting selective anti-tumor effects act on cell membrane, but studies on this field were restricted by lack of peptide information. This study was to establish a tumor cell membrane model, and isolate specific anti-tumor peptides. METHODS: Pore-forming peptides Mast21 and MastoparanX were chosen as positive control peptides to optimize the artificially synthesized tumor liposome cell membrane model, ribosome display system was used to isolate specific anti-tumor peptides from a designed random DNA library with affinity to membrane model. Anti-tumor effects of the isolated peptides on non-small cell lung cancer cell line NCI-H460 were analyzed with MTT assay. RESULTS: After 6-round successive selection with improved membrane model (PE/PS, 3:7) and ribosome display system, some sequences of peptides were obtained. In vitro experiment confirmed that some of them showed anti-tumor effects on NCI-H460 cells, 50% inhibitory concentration (IC(50)) of peptides SeqA3, and SeqB3 of NCI-H460 cells were (22.5+/-1.2) micromol/L,and (11.3+/-0.7) micromol/L, while on normal human fibro cell line CCD-27SK were more than 100 micromol/L. CONCLUSION: Specific anti-tumor peptides may be screened out by suitable tumor cell membrane model and ribosome display system, which will help to develop new anti-tumor drugs.

Antineoplastic Agents↗