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D Kerrigan

Publications and source records attributed to D Kerrigan.

At least 37 records · Page 2Linked to original sources
PubMed1990

10,11-Methylenedioxycamptothecin, a topoisomerase I inhibitor of increased potency: DNA damage and correlation to cytotoxicity in human colon carcinoma (HT-29) cells.

We had previously shown that 10,11-methylenedioxy-20-(RS)-camptothecin (MDO-CPT) is a more potent inhibitor of purified DNA topoisomerase I than 20-(S)-camptothecin (CPT). The current studies compared the cytotoxicity and DNA damage induced by MDO-CPT and CPT in the human colon carcinoma cell line, HT-29. MDO-CPT was 7- to 10-fold more potent than CPT both for cytotoxicity (ID50 = 25 vs. 180 nM) and production of DNA single-strand breaks (SSB). Kinetics of SSB formation and reversal were similar for MDO-CPT and CPT. DNA-protein crosslinks (DPC) were also produced by both drugs with a SSB/DPC ratio of 1/1. Moreover, no SSB were detected under non-deproteinizing conditions, indicating that both CPT and MDO-CPT produced protein-linked DNA single-strand breaks. A good correlation between cytotoxic potency and protein-linked DNA single-strand break production was observed for CPT and MDO-CPT, implying a causal relationship between drug-induced cytotoxicity and topoisomerase I inhibition. The sensitivity of human colon HT-29 cancer cells to camptothecins may be a selective phenomenon since these cells normally express natural resistance to current chemotherapeutic drugs, including topoisomerase II inhibitors.

Camptothecin↗
PubMed1990

Malignant carcinoid within a recurrent sacrococcygeal teratoma in childhood.

Sacrococcygeal teratomas are uncommon tumors of childhood carrying a good prognosis if histologically benign and completely excised, especially if the coccyx is also excised. Carcinoids are also rare in children and only rarely associated with teratomas. We report the findings in a girl who had a malignant carcinoid within a recurrent malignant sacrococcygeal teratoma following its incomplete excision in the neonatal period. We believe that this is the first such case occurring in childhood.

Carcinoid Tumor↗
PubMed1989

Differential requirement of DNA replication for the cytotoxicity of DNA topoisomerase I and II inhibitors in Chinese hamster DC3F cells.

The cytotoxicity of topoisomerase inhibitors is thought to result from the induction of enzyme-mediated DNA breaks. The fact that these breaks reverse rapidly in cells programmed to die, led us to investigate further the cytotoxic mechanisms of topoisomerase I (camptothecin) and topoisomerase II inhibitors (VP-16 and amsacrine) in Chinese Hamster lung fibroblasts (DC3F). Exposures (30 min) to camptothecin produced limited cell killing with approximately 20% of the cells naturally resistant. This resistance was overcome by increasing the drug exposure time. Inhibition of DNA synthesis by 5-min pretreatments with aphidicolin or hydroxyurea abolished the cytotoxicity of camptothecin without changing the level of camptothecin-induced DNA breaks. A good correlation was found between the degree of DNA synthesis inhibition by aphidicolin and the reduction of camptothecin cytotoxicity. In similar experiments performed with topoisomerase II inhibitors, aphidicolin prevented only partially against VP-16- and amsacrine-induced cytotoxicities, yet had no effect upon drug-induced DNA breaks. These results indicate that the production of topoisomerase-mediated DNA breaks by antitumor drugs is not sufficient for cell killing. Instead, an interference of moving DNA replication forks with drug-stabilized topoisomerase-DNA complexes is critical for cell death. The cytotoxicity of camptothecin seemed to be completely related to this process, while that of topoisomerase II inhibitors seemed to involve additional mechanisms in DC3F cells.

Amsacrine↗
PubMed1989

Topological complexes between DNA and topoisomerase II and effects of polyamines.

The polyamines spermine and spermidine were found to enhance the formation of a stable noncovalent complex between mammalian topoisomerase II and DNA. This complex is not associated with DNA strand breaks and forms to a greater extent with supercoiled than with relaxed circular or with linear DNA. Polyamine-induced complex formation is associated with a stimulation of the enzymatic relaxation of DNA supercoils. In these respects, the polyamine-enhanced complex differs from the covalent cleavable complexes stabilized by DNA intercalators such as amsacrine (m-AMSA) or epipodophylotoxins such as teniposide (VM-26). In the polyamine-enhanced complex, the topoisomerase II may be a donutlike structure topologically bound to the DNA and able to migrate and dissociate from the ends of linear DNA molecules. At relatively high concentrations, spermine (1 mM) enhances topoisomerase II induced cleavage at certain sites on the SV40 genome that could have regulatory significance.

Amsacrine↗
PubMed1989

Progressive resistance to doxorubicin in mouse leukemia L1210 cells with multidrug resistance phenotype: reductions in drug-induced topoisomerase II-mediated DNA cleavage.

Cells selected for resistance to doxorubicin (DOX) express the multidrug resistance (MDR) phenotype, and resistance has been suggested to be due primarily to enhanced cellular efflux of drug. A progressively DOX-resistant (10- and 40-fold) L1210 mouse leukemia model system, which does not exhibit enhanced DOX efflux as a primary mechanism of resistance, was found to display the MDR phenotype, based on overexpression of P-glycoprotein in western blots and cross-resistance to vinca alkaloids. Cross-resistance to another topoisomerase II inhibitor, etoposide (VP-16), was similar to that of DOX (10- and 40-fold), whereas resistance to N-[4-(9-acridinylamino)-3-methoxyphenyl]methanesulfonamide (m-AMSA) was 5-fold lower. In contrast, no cross-resistance to camptothecin, an inhibitor of topoisomerase I, was observed. Topoisomerase II decatenation activity in nuclear extracts from 10- and 40-fold DOX-resistant cells was 2- and 4-fold lower, respectively, when compared to sensitive cells. In these cells, however, marked reductions in m-AMSA- and VP-16-induced topoisomerase II mediated DNA cleavage were found to exceed decreases in the catalytic activity of the enzyme. Results from this study demonstrated that, in progressively DOX-resistant L1210 mouse leukemia cells with the MDR phenotype, a better relation existed between the degree of resistance and reduced VP-16- and m-AMSA-induced topoisomerase II mediated DNA cleavage, than between increases in P-glycoprotein and concomitant reduction in DOX accumulation.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1988

DNA strand breaks produced by etoposide (VP-16,213) in sensitive and resistant human breast tumor cells: implications for the mechanism of action.

Pleotropic resistant human breast cancer cells (MCF-7), selected for resistance to Adriamycin, were used to study the production of DNA strand breaks by etoposide (VP-16) and its relationship to drug cytotoxicity. It was shown that the resistant MCF-7 cell line was cross-resistant to VP-16, and the degree of resistance was found to be 125-200-fold. Alkaline elution studies indicated that the parental cell line was very sensitive to VP-16 which caused extensive DNA strand breakage. In contrast, little DNA strand breakage was detected in the resistant MCF-7 cells, even at very high drug concentrations, indicating a good agreement between strand breaks and cytotoxicity. Further studies indicated that the nuclei isolated from the parental cell line were more resistant to VP-16-induced DNA strand breaks than the intact cells, while the opposite was found in the resistant cell line. In addition, the alkaline elution studies in isolated nuclei showed only a 2-fold reduction of VP-16-induced DNA breaks in nuclei from the resistant cells. In agreement with this result, it was found that nuclear extract from the resistant cells produced 2-3-fold less VP-16-induced DNA breaks than that from the sensitive cells in 32P-end-labeled SV40 DNA. VP-16 uptake and efflux studies indicated that there was a 2-3-fold decrease in net cellular accumulation of VP-16 in the resistant cells. Although the reduced uptake of VP-16 and decreased drug sensitivity of topoisomerase II appear to contribute to the mechanism of action and the development of resistance to VP-16, they do not completely explain the degree of resistance to VP-16 in this multidrug-resistant MCF-7 cell line indicating that other biochemical factors, such as activation of VP-16, are also involved in drug resistance and suggesting that the resistance is multifactorial.

Breast Neoplasms↗
PubMed1988

Topoisomerase II-mediated DNA damage produced by 4'-(9-acridinylamino)methanesulfon-m-anisidide and related acridines in L1210 cells and isolated nuclei: relation to cytotoxicity.

4'-(9-Acridinylamino)methanesulfon-m-anisidide (m-AMSA) is a DNA intercalating 9-aminoacridine with clinical activity in adult acute leukemia. m-AMSA has been shown to produce protein-linked DNA strand breaks in mammalian cells through an interaction with the nuclear enzyme DNA topoisomerase II. We have compared the effects of m-AMSA and several acridine analogues (9-aminoacridine; A, NSC 343499; B, SN 16507; C, NSC 140701; D, SN 13553) on DNA integrity and cell survival in L1210 leukemia in vitro. Cells (or isolated nuclei) were treated with drugs (0.1-50 microM) for 0.5-1.0 h and subsequently analyzed using the alkaline elution technique. All drugs, except Compound D, produced DNA-protein cross-links (DPC) in L1210 cells. At 1 microM, potency was in the order, C greater than m-AMSA greater than B greater than A much greater than 9-aminoacridine. In isolated nuclei, DPC and single-strand breaks were produced in essentially a 1:1 ratio, which is consistent with topoisomerase II-mediated protein-linked DNA breaks. Potency differences were less pronounced in nuclei than in cells. In isolated nuclei, Compound D produced extensive DPC not associated with single-strand breaks, which suggests a more complex activity for this compound. Colony formation assays demonstrated the cytotoxicity of most of these acridine analogues (C greater than B greater than A approximately equal to m-AMSA much greater than D = 9-aminoacridine). Correlation of DPC with cell kill gave similar curves for each compound. These results are evidence for a causal relationship between drug-induced topoisomerase II-mediated DNA breaks and cytotoxicity.

Aminoacridines↗
PubMed1988

Sister chromatid exchanges, chromosomal aberrations, and cytotoxicity produced by antitumor topoisomerase II inhibitors in sensitive (DC3F) and resistant (DC3F/9-OHE) Chinese hamster cells.

4'-(9-Acridinylamino)methanesulfon-m-anisidide, etoposide, and 2-methyl-9-hydroxyellipticinium are antitumor topoisomerase II (topo II) inhibitors. The relationship between drug-induced sister chromatid exchanges (SCEs) or chromosomal aberrations and cytotoxicity was investigated in Chinese hamster cells sensitive (DC3F) and resistant (DC3F/9-OHE) to topo II inhibitors. Thirty-min drug treatments produced SCEs and chromosomal aberrations in sensitive (DC3F) cells, 4'-(9-acridinylamino)methanesulfon-m-anisidide being more potent than etoposide or 2-methyl-9-hydroxyellipticinium at equimolar concentrations. Comparable treatments of resistant (DC3F/9-OHE) cells did not produce chromosomal damage. The cytotoxicity of 4'-(9-Acridinylamino)-methanesulfon-m-anisidide was also greater than that of etoposide or 2-methyl-9-hydroxyellipticinium in DC3F cells, and no cytotoxicity was observed in DC3F/9-OHE at drug concentrations that produced more than two logs of cell kill in DC3F cells. A plot of cytotoxicity versus SCEs showed a good correlation between the two parameters. Therefore, short treatments of mammalian cells with topo II inhibitors produce reversible topo II-mediated DNA breaks which are associated with chromosomal aberrations and SCEs whose number correlates with cytotoxicity. In addition, topo II mutant DC3F/9-OHE cells were more sensitive than DC3F cells to the chromosomal, DNA cross-linking and cytotoxic effects of mitomycin C and were equally sensitive to the cytotoxic effect of camptothecin.

Amsacrine↗
PubMed1987

Role of DNA intercalation in the inhibition of purified mouse leukemia (L1210) DNA topoisomerase II by 9-aminoacridines.

An attempt was made to analyze the mechanism by which 4'-(9-acridinylamino)methanesulfon-m-anisidide (m-AMSA) inhibits mammalian DNA topoisomerase II. The effects of various 9-aminoacridine derivatives differing by their DNA affinities and DNA sequence selectivity of binding were compared in the presence of purified mouse leukemia L1210 DNA topoisomerase II. No correlation was found between DNA unwinding and topoisomerase II inhibition. 9-Aminoacridine was inactive as a topoisomerase II inhibitor and o-AMSA was only weakly active. The location of L1210 topoisomerase II mediated DNA breaks produced in the absence or presence of 9-aminoacridines were studied in [32P]-end-labeled pBR 322 DNA. All 9-aminoacridines, even those differing by their DNA sequence selectivity of binding, produced similar DNA cleavage patterns. Most drug-induced topoisomerase II mediated DNA breaks appeared at sites that were already cleaved by the enzyme in the absence of drug. The present results suggest that 9-aminoacridines inhibit L1210 DNA topoisomerase II by interacting at or near enzyme-DNA complexes by some unknown DNA effect or by direct protein interaction.

Aminoacridines↗
PubMed1987

DNA unwinding and inhibition of mouse leukemia L1210 DNA topoisomerase I by intercalators.

The DNA unwinding effects of some 9-aminoacridine derivatives were compared under reaction conditions that could be used to study drug-induced topoisomerase II inhibition. An assay was designed to determine drug-induced DNA unwinding by using L1210 topoisomerase I. 9-aminoacridines could be ranked by decreasing unwinding potency: compound C greater than or equal to 9-aminoacridine greater than o-AMSA greater than or equal to compound A greater than compound B greater than m-AMSA. Ethidium bromide was more potent than any of the 9-aminoacridines. This assay is a fast and simple method to compare DNA unwinding effects of intercalators. It led to the definition of a drug intrinsic unwinding constant (k). An additional finding was that all 9-aminoacridines and ethidium bromide inhibited L1210 topoisomerase I. Enzyme inhibition was detectable at low enzyme concentrations (less than or equal to 1 unit) and when the kinetics of topoisomerase I-mediated DNA relaxation was studied. Topoisomerase I inhibition was not associated with DNA swivelling or cleavage.

Aminacrine↗
PubMed1987

Topoisomerase II-mediated DNA breaks and cytotoxicity in relation to cell proliferation and the cell cycle in NIH 3T3 fibroblasts and L1210 leukemia cells.

The DNA intercalator, 4'-(9-acridinylamino)methanesulfon-m-anisidide (m-AMSA) and the nonintercalator, etoposide (VP-16) produce topoisomerase II-mediated protein-linked DNA strand breaks. This function of topoisomerase II was investigated in relation to cell proliferation and cell cycle. Mouse fibroblasts NIH 3T3 and mouse leukemia L1210 cells stop proliferation when they reach a certain density. Nuclei were isolated from proliferative or quiescent cells and then treated with drug for 30 min. DNA modifications were assayed by alkaline elution. We found that the frequencies of m-AMSA- or VP-16-induced DNA-protein links were higher in nuclei from exponentially growing than in those from quiescent cells in both the 3T3 and the L1210 lines. Drug-induced protein-associated DNA breaks were also studied as a function of the cell cycle in 3T3 cells that had been arrested by contact inhibition in medium containing 1% calf serum and then stimulated to proliferate by raplating at a lower cell density in medium containing 10% serum. In these synchronized cells, a large peak of [3H]thymidine incorporation occurred 18-30 h after replating. The yield of DNA-protein cross-links produced by 30-min drug treatments of nuclei isolated at various times after growth initiation increased concomitantly with the peak of the DNA synthesis. The topoisomerase II activity of nuclear extracts, as measured by kinetoplast DNA decatenation followed a similar pattern. Using colony-forming assays, we also observed that m-AMSA and VP-16 were most cytotoxic in proliferative cells and during DNA synthesis. These results suggest that alkaline elution measurement of m-AMSA- or VP-16-induced protein-linked DNA breaks reflects the association of topoisomerase II with DNA. This association is increased during DNA replication, making the cells more vulnerable to m-AMSA and VP-16 at this time.

Amsacrine↗
PubMed1987

Protein-linked DNA strand breaks produced by etoposide and teniposide in mouse L1210 and human VA-13 and HT-29 cell lines: relationship to cytotoxicity.

The two demethylepipodophyllotoxin glycosides, teniposide (VM-26) and etoposide (VP-16), have previously been reported to interact with DNA topoisomerase II by stabilizing a topoisomerase II-DNA covalent intermediate. This study examined the protein-associated aspect of the topoisomerase II-DNA-epipodophyllotoxin lesion. We found that in mouse (L1210) and human (VA-13 and HT-29) log-phase cell cultures, all DNA strand breaks produced by VP-16 or VM-26 were protein-associated. We found also that these protein-associated breaks occurred with a frequency which correlated with cytotoxicity in all three cell lines. For all three cell lines and for both compounds the regression lines were similar. Therefore, for a given class of topoisomerase II inhibitors, it may be possible to generate a characteristic line from which DNA-protein crosslink frequency predicts cytotoxicity.

Animals↗
PubMed1986

Isolation of intercalator-dependent protein-linked DNA strand cleavage activity from cell nuclei and identification as topoisomerase II.

DNA intercalating agents such as 4'-(9-acridinylamino)methanesulfon-m-anisidide (m-AMSA) have previously been found to induce in mammalian cells the formation of protein-associated DNA single- and double-strand breaks. In the current work, an activity characterized by the production of DNA-protein links associated with DNA strand breaks and by stimulation by m-AMSA was isolated from L1210 cell nuclei and was shown to be due to topoisomerase II. Nuclei were extracted with 0.35 M NaCl, and the extract was fractionated by gel filtration, DNA-cellulose chromatography, and glycerol gradient centrifugation. A rapid filter binding assay was devised to monitor the fractionation procedure on the basis of DNA-protein linking activity. The active DNA-cellulose fraction contained both topoisomerase I and topoisomerase II whereas the glycerol gradient purified material contained only topoisomerase II activity. The properties of the active material were studied at both stages of purification. m-AMSA enhanced the formation of complexes between purified topoisomerase II and SV40 DNA in which the DNA sustained a single- or double-strand cut and the enzyme was covalently linked to the 5' terminus of the DNA. This action was further enhanced by ATP, as well as by nonhydrolyzable ATP analogues. m-AMSA inhibited the topoisomerization and catenation reactions of topoisomerase II, probably because of trapping of the enzyme-DNA complexes. The activity showed a dependence on the type of DNA intercalators used, analogous to what was previously observed in intact cells. m-AMSA had no effect on topoisomerase I.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Reduced formation of protein-associated DNA strand breaks in Chinese hamster cells resistant to topoisomerase II inhibitors.

DNA intercalating drugs and the epipodophyllotoxins etoposide and teniposide interfere with the action of mammalian DNA topoisomerase II by trapping an intermediate complex of the enzyme covalently linked to the 5'-termini of DNA breaks. This effect can be observed in intact cells by alkaline elution measurement of protein-associated DNA strand breaks. To assess the cytotoxic role of this effect, we have studied a subline of DC3F Chinese hamster lung cells selected for resistance to the intercalating agent 9-hydroxyellipticine. This subline (DC3F/9-OHE) was cross-resistant to other intercalators as well as to etoposide. Resistance to Adriamycin was associated with reduced uptake. However, resistance to 4'-(9-acridinylamino)methanesulfon-m-aniside and 2-methyl-9-hydroxyellipticinium was observed in the absence of changes in drug uptake, suggesting a second mode of resistance. DC3F/9-OHE cells formed fewer protein-associated DNA strand breaks in response to 4'-(9-acridinylamino)methanesulfon-m-aniside, 2-methyl-9-hydroxyellipticinium, or etoposide than did the sensitive parental cells. The same was true for isolated nuclei from these cells, which is consistent with a mode of resistance unrelated to drug uptake through the plasma membrane. These data suggest that resistance to DNA topoisomerase II inhibitors exhibited by DC3F/9-OHE cells is due in part to a modification of topoisomerase II activity.

Alkaloids↗
PubMed1986

Altered DNA topoisomerase II activity in Chinese hamster cells resistant to topoisomerase II inhibitors.

Most DNA intercalators and epipodophyllotoxins inhibit mammalian topoisomerase II by trapping the enzyme within DNA cleavage complexes that can be detected in cells as protein-associated DNA strand breaks. We have characterized previously a line of Chinese hamster cells (DC3F/9-OHE cells) the resistance of which to the cytotoxic effect of intercalators and etoposide is associated with a reduced formation of protein-associated DNA strand breaks. In the present study, topoisomerases of these cells were compared to those of the parental sensitive cells (DC3F). NaCl extracts (0.35 M) of isolated DC3F/9-OHE nuclei did not form 4'-(9-acridinylamino)methanesulfon-m-anisidide-induced DNA-protein linking, whereas DC3F nuclear extracts did. In addition, DC3F/9-OHE nuclear extract had an unusually high level of DNA linking activity in the absence of 4'-(9-acridinylamino)methanesulfon-m-anisidide. Topoisomerases II from DC3F/9-OHE and DC3F nuclei appeared similar qualitatively. DC3F/9-OHE nuclear extract had approximately twice less topoisomerase II molecules than did DC3F nuclear extract but similar topoisomerase II activity. Topoisomerase I activities appeared also similar in sensitive and resistant cells. However, part of DC3F/9-OHE topoisomerase I copurified with a DNA linking activity which was not present in DC3F nuclei. This unusual DNA linking activity was not sensitive to the stimulatory effect of 4'-(9-acridinylamino)methanesulfon-m-anisidide.

Adenosine Triphosphate↗