Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.3.1.21 (CPT)
 4,580 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

CPT-11, 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxy camptothecin, is a well-known DNA topoisomerase I inhibitor. SN-38 is a metabolite of this compound. Both emit fluorescence when activated by a laser beam. With a confocal laser scanning microscope (CLSM), we determined the intracellular distribution of CPT-11 and SN-38 and the chronological changes in drug-treated PC-7, a cell line of human non-small cell lung cancer, and its CPT-11 resistant variant, PC-7/CPT cells. There were many more granules in the cytoplasm in PC-7/CPT than in the parent cell line (PC-7). The granule formation of the resistant cell could indicate a different drug metabolism in the cytoplasm from that of the parent cell. This technique would provide a new way of investigating the mechanism of resistance of cancer cells to anticancer drugs.
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PMID:Intracellular distribution of CPT-11 in CPT-11-resistant cells with confocal laser scanning microscopy. 133 95

We established a cisplatin-resistant human ovarian cancer cell line (HAC2/0.1) from the parent cell line (HAC2/P) by continuous exposure of HAC2/P to 0.1 microgram of cisplatin/ml. Drug sensitivity determined by colony assay revealed that HAC2/0.1 was 2.4 times as resistant to cisplatin as the parental cell line. HAC2/0.1 was 12.1 and 2.0 times as resistant to (4s)-4,11-diethyl-4-hydroxy-9-[(4-piperidinopiperidino)-carbony loxy]dione hydrochloride trithydrate (CPT-11) and 7-ethyl-10-hydroxy-CPT (SN-38; an active metabolite of CPT-11), respectively, than HAC2/P. We studied the mechanism of cross-resistance to CPT-11 in HAC2/0.1. The glutathione (GSH) content was higher in HAC2/0.1 than in HAC2/P. The activity of DNA topoisomerase I and the accumulation of CPT-11 and SN-38 were also the same. On the other hand, the conversion of CPT-11 to SN-38 in HAC2/0.1 was about 3-fold less than in HAC2/P. Treatment of the parent and resistant cell lines with buthionine sulfoxamine (BSO) decreased the GSH content of both cell lines and decreased the 50% inhibitory concentrations of all the tested drugs for HAC2/0.1. The accumulation of CPT-11 in HAC2/0.1 but not in HAC2/P was increased by BSO treatment. On the other hand, in HAC2/P the 50% inhibitory concentrations of SN-38 and CPT-11 were not influenced by BSO treatment. The 50% inhibitory concentration of CPT-11 for HAC2/0.1 was not reduced by BSO treatment to the level for HAC2/P, even though the GSH content had been reduced more than in HAC2/P. These results show that there is no clear relationship between GSH and resistance to CPT-11. The decreased conversion of CPT-11 to SN-38 is considered to be the main cause of resistance to CPT-11 in this cell line.
Cancer Res 1992 Jan 15
PMID:Mechanism of cross-resistance to a camptothecin analogue (CPT-11) in a human ovarian cancer cell line selected by cisplatin. 134 10

To determine whether there exists cross-resistance between anticancer drugs and radiation, six drug-resistant human lung cancer cell lines and their parental cell lines were examined for radiosensitivity using a growth-inhibition assay. Only one cisplatin-resistant cell line, PC-9/CDDP, showed cross-resistance to radiation. The other three cisplatin-resistant cell lines (PC-7/CDDP, PC-4/CDDP, and H69/CDDP), an etoposide-resistant cell line (H69/VP) and a camptothecin-resistant cell line (PC-7/CPT) did not show cross-resistance to radiation. To analyze the mechanism of radiation resistance in PC-9/CDDP cells, the formation and repair of radiation-induced DNA single-strand breaks (ssb) and double-strand breaks (dsb) were examined by alkaline elution and neutral elution respectively. Although the formation of DNA ssb and repair of both DNA ssb and DNA dsb were the same for both cell lines, the formation of DNA dsb in PC-9/CDDP cells was significantly less than those in PC-9 cells. Measurement of intracellular glutathione content in all of the cell lines revealed that only PC-9/CDDP cells had a significant increase of glutathione content compared to the parental cells. Buthionine sulfoximine treatment of PC-9/CDDP cells caused an increase of DNA dsb to the same levels as in PC-9 cells after irradiation and caused a complete radiosensitization. These results indicate that cross-resistance to radiation in drug-resistant cells in a rare phenomenon, and increased glutathione content may play a crucial role in the emergence of cross-resistance to radiation in the drug-resistant cells.
J Cancer Res Clin Oncol 1992
PMID:Radiation sensitivities in various anticancer-drug-resistant human lung cancer cell lines and mechanism of radiation cross-resistance in a cisplatin-resistant cell line. 140 May 62

Camptothecin-11 (CPT-11) is a new derivative of camptothecin, a plant alkaloid antitumor agent, and a good candidate for clinical trials because of higher antitumor activity, less toxicity, and high aqueous solubility. CPT-11 is known to be altered into an active form, SN-38, by esterase in in vivo. CPT-11-resistant cells (PC-7/CPT) established from a human non-small cell lung cancer cell (PC-7) by stepwise, continuous treatment with CPT-11 exhibit about a 10-fold increase in resistance to the drug. CPT-11-resistant cells show a moderate cross-resistance to camptothecin (x8.6) and SN-38 (x8.6), and weak cross-resistance to Adriamycin (x2.2) and 5-fluorouracil (x2.4). The comparative studies between the parent (PC-7) and resistant (PC-7/CPT) cell lines with respect to their growth characterization shows a longer cell doubling time (45.8 versus 35.5 h), a lower cloning efficiency (3.2 versus 7.1%), and a lower population of S-phase cells (26.4 versus 36.0%) in the CPT-11-resistant cells. This observation may partly explain the resistance to CPT-11, a drug whose activity is cell cycle specific. Accumulation of CPT-11 is nearly the same in both cell lines. However, the intracellular concentration of SN-38 formed in the parent cells was 2-fold greater than in the CPT-11-resistant cells. This alteration may affect to some extent to the resistance. As assayed by relaxation of supercoiled plasmid DNA, the total activity of DNA topoisomerase I from the CPT-11-resistant cells was shown to be reduced to one-fourth its level in sensitive cells. The reduced activity was caused by a reduction of amount of DNA topoisomerase I. Furthermore, the enzyme from the resistant cells was shown to be 5-fold more resistant to CPT-11 than the enzyme from the parent cells. Thus, decreased total activity of topoisomerase I may play an important role in cellular resistance to CPT-11, and it appears that this decreased activity is due to a resistant form of topoisomerase I in CPT-11 resistant cells.
Cancer Res 1990 Sep 15
PMID:Establishment of a camptothecin analogue (CPT-11)-resistant cell line of human non-small cell lung cancer: characterization and mechanism of resistance. 216 85

A new water-soluble derivative of camptothecin, 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (CPT-11), did not exhibit potent antitumor activity in vitro against experimental tumor cells. The 50% effective doses of CPT-11 against KB and L1210 cells were 1100 and 5500 ng/ml, respectively. These values were markedly higher than those of camptothecin (CPT, 0.98 and 3.7 ng/ml) or 7-ethyl-10-hydroxycamptothecin (SN-38, 0.37 and 3.6 ng/ml). CPT-11 was found to be converted into SN-38 in mouse serum. In vitro incubation of CPT-11 in mouse serum or tissue homogenate enhanced the growth-inhibitory activity much more than that expected from the concentration of CPT-11. This enhancement of the activity coincided with that expected from the SN-38 concentration in incubated serum or homogenate, though the contribution of CPT-11 could not be refuted. SN-38 is considered to play a major role in the antitumor activity when CPT-11 is incubated in serum or homogenate. The plasma CPT-11 concentration decreased biexponentially after i.v. administration of CPT-11 into mice with a biological half-life of 0.8 to 1.1 h. The area under the plasma CPT-11 concentration-time curve showed dose dependency. The SN-38 concentration decreased for the first 30 min after administration and was then maintained for a few hours at about 0.1 microgram/ml after i.v. administration of 20 and 40 mg/kg of CPT-11 followed by the log-linear terminal phase with a half-life of about 2 h which was independent of the dose. It is suggested that the maintenance of plasma SN-38 concentration might be necessary for it to exhibit antitumor activity in vivo.
Cancer Res 1990 Mar 15
PMID:Metabolism and pharmacokinetics of the camptothecin analogue CPT-11 in the mouse. 230 25

H 615, the first transplantable mouse liver carcinoma model established in China, was derived from a spontaneous hepatocellular carcinoma of an inbred 615 mouse and has been successfully propagated for 52 generations during the past 7 years and more. Its biologic and pathologic features are relatively stable. H 615 was a syngenic transplantable tumor model of 615-strain mice with a successful transplantation rate of 85.6% without spontaneous regression. The course of tumor growth after subcutaneous inoculation was divided into 4 stages: latent, slowly growing, rapidly growing and terminal stages. Cancer metastasis was rare. The tumor-bearing host would die of cachexia finally. The mean survival time was 62.2 +/- 11.0 days regardless of sex or age. Histologically and ultrastructurally, H 615 was a well-differentiated hepatocellular carcinoma, rather resembling human liver carcinoma. The short-term primary passage culture of H 615 showed that, in vitro, tumor tissue could easily grow into monolayer, the majority of which appeared as epithelioid cells in cytomorphology. Therapeutic tests of 15 anticancer drugs showed that H 615 was sensitive, in varying degrees, to 5 drugs, i. e. MMC, Thio-Tepa, 5FU, CPT and DACT. The inhibition rate of MMC and Thio-Tepa could be as high as 100%. These experimental results are similar to those of the human liver cancer chemotherapy. Hence, the authors believe that H 615 may be a useful model in experimental study of the liver cancer and screening of anticancer drugs.
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PMID:[Establishment and experimental study of a transplantable hepatocellular carcinoma model in 615-strain mice (H 615)]. 344 59

A method for the detection and quantitation of 1-beta-D-arabinofuranosylcytosine 5'-triphosphate (ara-CTP), the active metabolite cells and leukemic cells of the peripheral blood from patients receiving ara-C therapy is described. ara-CTP is separated from normal cellular nucleotides by high-pressure liquid chromatography and is quantitated by its absorbance of ultraviolet light at 280 nm with a lower limit of sensitivity of 25 pmol/2 x 10(7) cell equivalents. During separate courses of continuous infusion of different therapeutic doses of ara-C, ara-CTP accumulated in the leukemic bone marrow cells of a patient with acute myelogenous leukemia in proportion to the dose of ara-C. Continuous infusion of ara-C (90 mg/sq m/day) resulted in plateau levels of ara-CPT in peripheral blast cells after 24 hr (115 pmol/1 x 10(7) cell equivalents). A priming dose of ara-C(125 to 250 mg/sq m) followed by a 1-hr infusion of an equal dose of ara-C to patients with acute myelogenous leukemia facilitated the determination of ara-CTP retention in bone marrow and peripheral blood leukemic cells in vivo. This procedure should be useful for extended studies of the biochemical pharmacology of ara-CTP in vivo.
Cancer Res 1980 Mar
PMID:Quantitation of 1-beta-D-arabinofuranosylcytosine 5'-triphosphate in the leukemic cells from bone marrow and peripheral blood of patients receiving 1-beta-D-arabinofuranosylcytosine therapy. 693 39

8-Cl-cAMP and 8-NH2-cAMP induced MCF-7 cell death. The type(s) of cell death were studied in more detail and compared with the cell death type (apoptosis) induced by okadaic acid, an inhibitor of serine/threonine phosphatases. By morphological criteria dying cells showed loss of cell-cell interactions and microvilli, condensation of nuclear chromatin and segregation of cytoplasmic organelles. By in situ nick end-labelling, using digoxigenin-conjugated dUTP as probe, a large fraction of 8-Cl-cAMP, 8-NH2-cAMP and 8-Cl-adenosine-exposed cells stained positively in the advanced stages of death. In the early phase of chromatin condensation the cells stained negatively. Specific (internucleosomal) DNA fragmentation was not observed. The MCF-7 cell death induced by 8-Cl-cAMP and 8-NH2-cAMP was not mediated by activation of the cAMP kinase since more stable cAMP analogues (8-CPT-cAMP and N6-benzoyl-cAMP) or forskolin failed to induce death. Furthermore, 8-Cl-cAMP action was counteracted by adenosine deaminase and 3-isobutyl-1-methylxanthine, and mimicked by 8-Cl-adenosine, a major metabolite of 8-Cl-cAMP. It is concluded that 8-Cl- and 8-NH2-cAMP can induce morphological and biochemical effects resembling apoptotic cell death in MCF-7 cells through their conversion into potent cytotoxic metabolite(s).
Br J Cancer 1995 Nov
PMID:8-Chloro-cAMP induces apoptotic cell death in a human mammary carcinoma cell (MCF-7) line. 757 61

Camptothecins belong to a group of anticancer agents with a specific mechanism of action: stabilization and trapping of eukaryotic DNA topoisomerase I (top1) cleavable complexes. Two water-soluble camptothecin derivatives are in clinical trial, and their anticancer activity appears promising: topotecan and CPT-11. The latter is hydrolyzed to its active metabolite, SN-38. We have previously reported that SN-38 is among the most cytotoxic camptothecin derivatives and that the cleavable complexes induced by SN-38 are more stable than those induced by CPT in human colon carcinoma cells [Tanizawa et al. (1994) J. Natl. Cancer Inst, 86, 836-842]. Top1 inhibition was further investigated by determining the salt-induced religation rates of top1-cleavable complexes in fragments from the top1 cDNA. Religation depended on both the local DNA base sequence and the drug structure. Cleavable complexes induced by SN-38 and 10,11-methylenedioxycamptothecin were markedly more stable (less rapidly reversible) than those induced by CPT, topotecan, and 9-aminocamptothecin. The stability of 10-hydroxycamptothecin-induced cleavable complexes was intermediate to those of CPT and SN-38, indicating that both the 10-hydroxy and the 7-ethyl group of SN-38 probably interact with the drug binding site of top1-cleavable complexes. A DNA oligonucleotide containing a single top1 cleavage site was also used to compare the camptothecin derivatives. The salt stability of drug-induced cleavable complexes in the top1 oligonucleotide was correlated with the drug potencies to induce top1 cleavage. Cell killing requires that trapped cleavable complexes be converted to DNA damage as a result of replication fork collision.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Differential stabilization of eukaryotic DNA topoisomerase I cleavable complexes by camptothecin derivatives. 776 31

The kinetics of the in vivo interconversion of the carboxylate and lactone forms of the prodrug irinotecan, 7-ethyl-10-[4-(1-piperidino)-1- piperidino]carbonyloxycamptothecin (CPT-11), and its active metabolite SN-38 were studied in five patients using a HPLC method that allows the simultaneous determination of all four compounds and detects any hydrolysis of lactones due to inadequate sample handling and storage. The apparent conversion of CPT-11 lactone to the carboxylate in vivo was rapid with a mean half-life of 9.5 min; the carboxylate became the predominant form of plasma CPT-11 soon after the end of the infusion. The ratio of the area under the plasma concentration-time curves of the lactone to total CPT-11 was 36.8 +/- 3.5% (SD). In contrast, SN-38 was present predominantly as the lactone at all times and with little interpatient variability (lactone/total area under the plasma concentration-time curve ratio, 64.0 +/- 3.4%). This may explain in part the promising activity of CPT-11 because CPT derivatives are active against their target, topoisomerase I, only in their lactone form.
Cancer Res 1994 Dec 15
PMID:Kinetics of the in vivo interconversion of the carboxylate and lactone forms of irinotecan (CPT-11) and of its metabolite SN-38 in patients. 798 23


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