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:2.7.7.7 (DNA polymerase)
17,007 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A new cytotoxic acridine alkaloid that exhibited antitumor activity in vivo was isolated from a marine Dercitus species sponge collected at a depth of 160 m in the Bahamas. This violet alkaloid, designated dercitin, inhibited the proliferation of cultured murine and human leukemia, lung, and colon tumor cells at nM concentrations (IC50 values of 63-150 nM) and prolonged the life of mice bearing ascitic P388 tumors (%T/C = 170, 5 mg/kg, i.p., QD1-9). Dercitin was also active against i.p. B16 melanoma and modestly inhibited the growth of s.c. Lewis lung carcinoma on the same schedule. DNA blocked the antiproliferative effects of the agent in culture, and incorporation studies indicated that dercitin disrupted DNA and RNA synthesis with less effects on protein synthesis, similar to the effects of known DNA intercalators. After 1-h exposure to 400 nM dercitin, the rates of incorporation of [3H]uridine, [3H]thymidine, and [3H]leucine by cultured P388 cells were inhibited 83, 61, and 23%, respectively. Equilibrium dialysis indicated that dercitin bound calf thymus DNA with an affinity of 3.1 microM and maximal binding of 0.20 mol dercitin/mol base pair. Binding involved intercalation as evidenced by ability to relax supercoiled phi X174 DNA (half maximal concentration for dercitin relaxation was 36 nM). The effects of dercitin on DNA mobility were reversible, and complete relaxation of DNA with topoisomerase I in the presence of dercitin followed by phenol extraction resulted in the appearance of supercoiled DNA. Dercitin, at microM concentrations, had a small effect in the K+-sodium dodecyl sulfate assay using cultured P388 cells, suggesting minimal inhibition of topoisomerase activity. But, dercitin completely inhibited DNA polymerase I/DNase nick translation of DNA at 1 microM. Relaxation of DNA at a given concentration was greater than inhibition of nick translation suggesting that the effects of dercitin on enzyme activity were secondary to changes in DNA conformation. Results indicate that dercitin is a new marine natural product that probably exerts its biological effects through intercalation into nucleic acids.
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PMID:Antitumor activity and nucleic acid binding properties of dercitin, a new acridine alkaloid isolated from a marine Dercitus species sponge. 254 17

A tumor-derived factor that inhibits cellular DNA synthesis was identified. The factor was extractable from a small-cell lung carcinoma cell line grown in either chemically defined medium or nu/nu mice and inhibited tritiated thymidine ([3H]dThd) incorporation by tumor cell lines of autologous, allogeneic, and xenogeneic origins. The viability of nonproliferating cells from normal tissue was not affected. Tumor extract inhibitory activity was trypsin labile but was resistant to other proteases, neuraminidase, lipase, DNase, RNase, glucosidase, extremes of pH-temperature, and reducing conditions. Inhibitory activity was reversibly bound to helix pomatia lectin but not to lentil, wheat germ, or concanavalin A lectins. Purification by size-exclusion high-performance liquid chromatography yielded a bioactive unimodal 12-kilodalton (kd) peak. The bioactive 12-kd moiety could be eluted from sodium dodecyl sulfate-polyacrylamide gels. Redosing of populations of the T-lymphoblastoid cell line CEM achieved an early (24 hr) sustained depression of pulse [3H]dThd incorporation and ultimately led to decreased population density of factor-treated populations. DNA histogram analysis demonstrated no change in cell cycle phase distribution after factor treatment. 5-Bromo-2'-deoxyuridine (BrdUrd) vs. propidium iodide with the two-parameter Fluorescence-Activated Cell Sorter analysis showed relative inhibition of non-S-phase BrdUrd uptake at 24 hours. A cell-free DNA polymerase assay demonstrated significant inhibition of non-alpha-polymerase-associated DNA synthesis in factor-treated cells. These studies suggest that this tumor-derived inhibitor of DNA synthesis represents a class of cellular products involved in the autoregulation of growth by regulation of DNA synthetic activity.
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PMID:Inhibition of DNA synthesis by a small-cell lung carcinoma-derived protein. 302 Mar 1

The production of immunoreactive somatomedin-C/insulin-like growth factor I (Sm-C/IGF-I) by the established cell line derived from a human lung carcinoma CALU-6 has been evidenced in the serum-free medium in increasing concentrations as a function of the incubation time. Gel filtration in acid conditions of cell-conditioned medium collected after 72 h showed peaks of immunoreactive Sm-C/IGF-I in the elution volume corresponding to the molecular weight of the synthetic Sm-C/IGF-I, and in the high molecular weight region, where specific binding sites for Sm-C/IGF-I could be also demonstrated. These results indicate that this established cell line produces high amounts of immunoreactive Sm-C/IGF-I and of Sm-C/IGF-I carrier protein. The pooled fractions corresponding to the molecular weight of synthetic Sm-C/IGF-I showed a competitive binding curve parallel to the standard in the Sm-C/IGF-I RIA system, and a mitogenic activity on cells from the same line similar to the one observed using two different pure Sm-C/IGF-I preparations, obtained by chemical synthesis or by DNA recombinant technology. When a monoclonal antibody (sm-1.2) raised against Sm-C/IGF-I was added into the medium, the mitogenic effect observed by both synthetic and cell-derived Sm-C/IGF-I peptide was completely abolished; the monoclonal antibody also partially inhibited the effect of 10% fetal calf serum and the thymidine incorporation observed in serum-free medium without growth factors. In serum-free medium the monoclonal antibody produced a 45% reduction of cells in S phase by thymidine labeling index without modification of the growth fraction as determined by primer-dependent alpha-DNA polymerase labeling index. In conclusion it seems that Sm-C/IGF-I has a critical role in the autocrine stimulation of the replication of this cell line.
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PMID:Evidence for autocrine mitogenic stimulation by somatomedin-C/insulin-like growth factor I on an established human lung cancer cell line. 337 14

A new class of fragile sites termed common fragile sites is induced by aphidicolin, an inhibitor of DNA polymerase alpha. Analysis of these common fragile sites and cancer chromosome breakpoints indicates that eight fragile sites are in bands with cancer breakpoints. This is unlikely to be due to chance (p less than 0.01). Common fragile sites are in both bands where breaks occur in carcinoma of the lung and in carcinoma of the ovary. Common fragile sites are in bands with breaks leading to constitutional chromosome abnormalities associated with cancer: hereditary renal cell carcinoma and aniridia-Wilms' tumor complex. Common fragile sites, thus, may predispose to chromosome breaks and rearrangements in cancer.
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PMID:Cancer chromosome breakpoints and common fragile sites induced by aphidicolin. 643 79

Metastatic tumor burden in the lung of C57BL/6 or BDF1 mice was quantitated by measuring DNA polymerase alpha activity in the lung of tumor-bearing animals. DNA polymerase activity in the lung increased time-dependently following the inoculation of Lewis lung carcinoma (s.c.) or B16 melanoma variant B16-B2 (i.v.). In the Lewis lung carcinoma system, the number of metastatic modules and the weight of lung also increased time-dependently. Results from the B16 melanoma showed that the increase in lung nodules occurred 10 to 20 days after i.v. inoculation of tumor cells. DNA polymerase activity increased significantly during this period. Because the lung nodules were very small there was no obvious concomitant increase in lung weight. Since no significant infiltration of host cells was observed in the lung in response to metastatic foci, the rise in DNA polymerase activity should be due to tumor cells and not to infiltrating host cells. When the metastasis of Lewis lung carcinoma was inhibited by adriamycin and cyclophosphamide, decrease in DNA polymerase activity in the lung occurred. These results indicate that the degree of tumor metastasis can be quantitated by measuring DNA polymerase activity.
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PMID:Quantitative estimation of tumor metastasis by measurement of DNA polymerase activity. 654 83

A retroviral vector system was developed to transduce a K-ras antisense construct efficiently into human cancer cells. A 2-kb fragment of K-ras gene DNA in antisense orientation was linked to a beta-actin promoter and inserted into retroviral vector LNSX in two different orientations. The constructs were transfected into amphotropic packaging cell line GP+envAm12 followed by alternating transduction between the ecotropic packaging cell line psi-2 and GP+envAm12. Titers up to 9.7 x 10(7) colony-forming units (cfu)/ml were achieved without detectable replication-competent virus. The human large cell lung carcinoma cell line H460a, which has a homozygous codon 61 K-ras mutation, was transduced with an efficiency of 95% after five to seven repeated transductions. DNA polymerase chain reaction (PCR) and genomic DNA Southern blot analysis showed that the retroviral construct was integrated into the genome of H460a cells. K-ras antisense RNA expression was detected in the cells by Northern analysis, slot blot hybridization, and reverse transcriptase-PCR. Translation of the mutated K-ras p21 protein RNA was specifically inhibited, whereas expression of other p21 species was unchanged. Proliferation of H460a cells was suppressed 10-fold following transduction by the antisense construct. Colony formation in soft agarose and tumorigenicity in an orthotopic lung cancer model in nu/nu mice were dramatically reduced in H460a cells expressing antisense K-ras. We conclude that an antisense construct for K-ras can be expressed effectively in a retroviral vector that can efficiently transduce human cancer cells.
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PMID:Retroviral vector-mediated transduction of K-ras antisense RNA into human lung cancer cells inhibits expression of the malignant phenotype. 839 92

In situ PCR is a new technique for the localization of low copy number sequences. We report here a method for the in situ visualization of a point mutation in K-ras codon 12 by indirect in situ PCR. Twenty-five primers were examined to select mutant-specific primers. Harvested cell lines were fixed and suspended in PCR mixture. Forty cycles of PCR in cell suspension was performed in a thermal cycler using a hot start method. Cells were cytocentrifuged onto slides, and post-fixation was performed. The specimens on the slides were then hybridized with a digoxigenin-labeled probe, followed by color reaction. Both Calu-1 (mutated: TGT) and NCI-H460 (wild type: GGT) cells had strong hybridization signals in the nuclei with general primers. But with mutant-specific primers, only Calu-1 cells had hybridization signals. No signal was observed without primers or Taq DNA polymerase. Southern blotting of the same preparation confirmed desired amplification. We also applied direct in situ PCR, but this method failed to detect the point mutation. We conclude that our indirect in situ PCR method shows the feasibility of in situ identification of single cells carrying point mutations.
Lung Cancer 1997 Jul
PMID:Detection of K-ras point mutation by in situ PCR in cell suspensions: comparison of the indirect and direct methods. 923 54

The acridine derivative m-AMCA (methyl-N-[4-(9-acridinylamino)-2-methoxyphenyl]carbamate hydrochloride), a carbamate analogue of the topoisomerase II poison amsacrine, is distinguished by its high cytotoxicity against non-cycling tumour cells. We compared the response of cultured Lewis lung carcinoma cells to m-AMCA, amsacrine and the topoisomerase I poison camptothecin. The DNA polymerase inhibitor aphidicolin reversed the cytotoxicity of camptothecin fully, that of amsacrine partially, and that of m-AMCA minimally. The ability of m-AMCA to induce the enzyme poly(ADP-ribose)polymerase (PARP) was markedly lower than that of camptothecin or amsacrine. Cell cycle responses to m-AMCA and amsacrine were similar, with slowing of progress through S-phase and arrest in G2-phase. These cell cycle changes were also observed when plateau phase cultures were exposed to drug for 1 h, washed free of drug and cultured in fresh medium, with m-AMCA having a more pronounced effect than amsacrine and camptothecin having no effect. We also examined the role of p53 protein in the response using cultured human H460 cells. Both m-AMCA and amsacrine induced p53 protein expression in proliferating but not in non-proliferating H460 cells, and induced p21WAF1 regardless of proliferation status. Both induced G1-phase cell cycle arrest. It is suggested that two cytotoxicity mechanisms can be distinguished using these drugs. The first is specific for S-phase cells, is reversed by aphidicolin and induces PARP activity. The second is cell cycle non-specific, does not induce PARP and is unaffected by aphidicolin. Camptothecin activates only the first, m-AMCA primarily the second and amsacrine activates both.
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PMID:Cellular responses to methyl-N-[4-9-acridinylamino)-2-methoxyphenyl] carbamate hydrochloride, an analogue of amsacrine active against non-proliferating cells. 938 32

(E)-2'-deoxy-2'-(fluoromethylene) cytidine (MDL101,731) is a new deoxycytidine analog which shows potent antitumor activity against several human tumor models. We previously showed that MDL101,731 inhibited human ribonucleotide reductase (RNR) in HeLa S3 human cervical carcinoma cells. Recently, it has been reported that another deoxycytidine analog, 2'-deoxy-2'-methylidenecytidine (DMDC) which also inhibits RNR from Escherichia coli, does not inhibit RNR in intact L1210 murine leukemia cells. MDL101,731 was designed as an inhibitor of RNR, so it is important to know the contribution of the RNR inhibitory activity of the drug on its antitumor efficacy in vivo. Therefore, we examined the relationship between the antitumor activity and RNR inhibitory activity of MDL101,731 using LX-1 human lung carcinoma which was highly sensitive to this drug. MDL101,731 showed strong inhibition of RNR activity in LX-1 lung carcinoma by both i.v. and p.o. administration. Administration of 15 mg/kg i.v. and 30 mg/kg p.o. of MDL101,731, doses which showed almost the same degree of antitumor activity against LX-1 lung carcinoma on a daily 5 day schedule, caused a similar degree and similar kinetics of inhibition of RNR in LX-1 lung carcinoma at least for 12 h after administration. On the other hand, DMDC as well as 1-beta-D-arabinofuranosyl-cytosine (ara-C), which is a well-known deoxycytidine analog and inhibits DNA polymerase alpha, did not inhibit RNR in LX-1 lung carcinoma at doses demonstrating antitumor activity. These results indicate that MDL101,731 exhibited antitumor activity through inhibition of RNR activity in tumor cells in vivo and the mechanism of antitumor action of MDL 101,731 might be different from those of DMDC and ara-C, at least in part.
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PMID:The relationship between the antitumor activity and the ribonucleotide reductase inhibitory activity of (E)-2'-deoxy-2'-(fluoromethylene) cytidine, MDL 101,731. 977 10

Telomerase is a ribonucleoprotein DNA polymerase that maintains the telomeric region of chromosomes lost during successive rounds of cell division. We used the telomeric repeat amplification protocol (TRAP) assay to examine telomerase activity in bronchial lavage (BL) samples from individuals undergoing diagnosis of lung cancer. Telomerase activity was detected in 17 (47%) of 36 samples examined. In particular, 16 (70%) of 23 BL specimens obtained from lung cancer patients showed detectable telomerase activity, while only 1 of 13 (8%) specimens obtained from patients without lung cancer demonstrated activity (P=0.00038). Moreover, 9 (90%) of 10 BL specimens, which were cytologically positive for lung cancer, were also positive for telomerase activity, while 7 (54%) of 13 cytologically negative BL specimens for lung cancer showed detectable telomerase activity. Detection of telomerase activity combined with cytology were able to identify 17 (74%) of 23 lung cancer cases whereas cytology alone identified 10 (43%) of 23 such cases (P=0.035). Our findings indicate that telomerase is a specific marker for malignant lung disease and a potential complementary tool to cytology in the diagnosis of certain lung cancer cases.
Lung Cancer 2000 Apr
PMID:Evaluation of telomerase activity in bronchial lavage as a potential diagnostic marker for malignant lung disease. 1070 7


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