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Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Defining specific biochemical targets of active antineoplastic agents could aid in discovering better anticancer therapy and more thoroughly understanding the biochemical basis of malignancy. Through a series of cellular and biochemical studies, we and others have identified the nuclear enzyme topoisomerase II as the target of several active agents, including 4'-(9-acridinylamino) methanesulfon-m-anisidide (m-AMSA). The interference with topoisomerase II produced by m-AMSA can be quantified in whole cells exposed to m-AMSA by using the alkaline elution technique to measure DNA cleavage. Antimetabolites such as ara-C, hydroxyurea, and 5-azacytidine can augment m-AMSA-induced, topoisomerase II-mediated DNA cleavage and, concurrently, m-AMSA-induced cell killing. Studies in proliferating and quiescent human cells and an m-AMSA-sensitive/resistant human leukemia cell pair further support the hypothesis that a connection exists between topoisomerase II-mediated DNA cleavage and the mechanism by which m-AMSA kills cells. Pharmacologic or hormonal modification of specific biochemical processes critical to drug-induced cytotoxicity may enhance the therapeutic index of clinically useful agents.
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PMID:Intercalator-induced, topoisomerase II-mediated DNA cleavage and its modification by antineoplastic antimetabolites. 242 89

The relationship between DNA topoisomerase II activity and drug resistance was studied in cloned cell lines of Adriamycin (ADR)-sensitive and -resistant P388 leukemia; drug resistant P388/ADR/3 (clone 3) and P388/ADR/7 (clone 7) cells are 5- and 10-fold more resistant to ADR than the sensitive cell line P388/4 (Cancer Res., 46: 2978, 1986). Topoisomerase II catalytic activity in crude nuclear extracts was reduced in drug-resistant cells as determined qualitatively by decatenation of kDNA. Using the centrifugal method fo quantitative analysis, topoisomerase II catalytic activity (mean +/- SE) was 81 +/- 10 units/mg total nuclear protein in sensitive cells, 29 +/- 2 units/mg total nuclear protein in resistant clone 3 cells, and 16 +/- 2 units/mg total nuclear protein in resistant clone 7 cells; these differences were highly significant (P less than 0.005). Similarly, quantitative analysis of DNA cleavage activity using 3' 32P-end-labeled pBR322 restriction fragments showed that drug-stimulated topoisomerase II cleavage activity in nuclear extracts from sensitive cells was approximately 1.7- and 2.9-fold greater than that from resistant clone 3 and 7 cells, respectively. Western blot analysis of nuclear extracts from the three cell lines using antibody against the C-terminal half of recombinant-prepared human topoisomerase II polypeptide revealed reduced immunoreactivity of topoisomerase II protein in the drug-resistant cells. These data suggest that reduced topoisomerase II activity in resistant cells, which may represent quantitative reduction of the enzyme, may be another property contributing to multifactorial drug resistance in these cells.
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PMID:Direct correlation between DNA topoisomerase II activity and cytotoxicity in adriamycin-sensitive and -resistant P388 leukemia cell lines. 253 93

Studies were conducted to determine the possible involvement of DNA topoisomerase II (Topo II) in the induction of differentiation in two human promyelocytic HL-60 leukemia cell variants that are either susceptible or resistant to differentiation induced by phorbol-12-myristate-13-acetate (PMA), a protein kinase C activator. The acquisition of maturation markers and changes in the activity, level, and phosphorylation of Topo II were determined after treatment with either novobiocin, a Topo II inhibitor, or PMA. Novobiocin at 50-150 microM induced differentiation in the HL-205 cells but not in the HL-525 cells, although both cell types were equally susceptible to novobiocin-evoked cytotoxicity. In both cell types, novobiocin induced similar reductions in topoisomerase I activity but different reductions in Topo II activity. Treatment with novobiocin at 150 microM for 6 h or at 2 mM for 30 min resulted in a 4-fold or higher reduction in Topo II activity in the differentiation-susceptible HL-205 cells but not in the differentiation-resistant HL-525 cells. A differential response in Topo II activity was also observed after treatment with PMA. The novobiocin-evoked decrease in Topo II activity seems to be due to an enhanced enzyme proteolysis, whereas the PMA-elicited decrease in Topo II activity is associated with an increase in Topo II phosphorylation. 1-(5-Isoquinolinesulfonyl)-2-methylpiperazine, which is an inhibitor of protein kinases, including protein kinase C, diminished the novobiocin-elicited proteolysis of Topo II and the PMA-induced Topo II phosphorylation, as well as the decrease in Topo II activity and the acquisition of differentiation markers induced by either novobiocin or PMA. These results suggest that induction of differentiation in HL-60 cells by novobiocin or PMA is associated with a reduction in Topo II activity, mediated directly or indirectly by a protein kinase(s), perhaps protein kinase C.
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PMID:Novobiocin- and phorbol-12-myristate-13-acetate-induced differentiation of human leukemia cells associated with a reduction in topoisomerase II activity. 253 41

Our human T-cell leukemia line, CEM/VM-1, selected for resistance to VM-26 (teniposide), is cross-resistant to several drugs that interact with topoisomerase II, including VP-16 (etoposide), 4'-(9-acridinylamino)methanesulphon-m-anisidide, daunorubicin, and mitoxantrone. However, in contrast to cell lines exhibiting multidrug resistance (MDR) associated with overexpression of P-glycoprotein, this line is not cross-resistant to the Vinca alkaloids, is not impaired in drug accumulation, and does not overexpress the mdrl gene (Cancer Res., 47: 1297, 5455, 1987). More recently we found that nuclear extracts of these cells exhibit decreased topoisomerase II catalytic and cleavage activity, compared to the drug-sensitive line (Biochemistry, 1988). These results suggest that an alteration in topoisomerase II or a modulator of this enzyme may be responsible for this altered topoisomerase II-form of multidrug resistance (at-MDR). In the present work, we studied the somatic cell genetics of at-MDR. We produced hybrid cell lines by polyethylene glycol-mediated fusion of the CEM/VM-1 line with a hypoxanthine-guanine phosphoribosyl transferase-deficient, ouabain-resistant CEM line (CEM.AG1.OU1.5) that exhibits VM-26 sensitivity. Ten of the hybrid lines that grew in selective medium were randomly chosen for expansion and four were analyzed for both DNA content by flow cytometry and VM-26 sensitivity in a 72-h growth inhibition assay. The hybrid lines all contained approximately 2x DNA compared to unfused controls, indicating that the fusions were successful. The IC50 for VM-26 in 3 of the 4 lines was the same as that of the sensitive controls, ranging from 4.7 to 7.4 x 10(-8) M, and another was 76 x 10(-8) M. These data indicate that drug sensitivity was reconstituted by the hybridization procedure. By comparison, the VM-26 IC50 values in the CEM/VM-1 cells and CEM/VM-1 x CEM/VM-1 control "fusions" were 360 and 750 x 10(-8) M, respectively. To determine whether a topoisomerase II-mediated function was reconstituted in the hybrids, we measured drug-stimulated DNA cleavage ("cleavable complex formation"). Using 32P-labeled pBR322 DNA as substrate with nuclear extracts from drug sensitive cells, 100 microM VM-26 maximally stimulated DNA cleavage by approximately 11-fold compared to no-drug controls.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Genetic characterization of the multidrug-resistant phenotype of VM-26-resistant human leukemic cells. 253 2

Several fused tri- and tetracyclic quinolines (I and II) with [2-methoxy-4-[(methylsulfonyl)amino]phenyl]amino or [3-(N,N-dimethylamino)propyl]amino side chains were prepared, and their DNA intercalative properties, KB cytotoxicity, antitumor activity (P388 leukemia), and ability to induce topoisomerase II dependent DNA cleavage were investigated. Some compounds having both intercalative ability and KB cytotoxicity were found to be inactive in vivo. However, a positive correlation was seen between the ability to induce topoisomerase II dependent DNA cleavage and antitumor activity in vivo. The indeno- (13a), benzofuro- (21a), and benzothieno- (22a) quinoline derivatives exhibited potent antitumor activities in vitro and in vivo, comparable to those of m-AMSA. They also intercalate DNA and induce topoisomerase II dependent DNA cleavage. Extended screening of 13a showed it to be active against solid tumors such as M5076 sarcoma, B16 melanoma, and colon 38 carcinoma.
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PMID:Synthesis and antitumor activity of fused tetracyclic quinoline derivatives. 1. 254 58

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

HL-60/AMSA is a human leukemia cell line that is 100 times more resistant to the cytotoxic actions of the antineoplastic, topoisomerase II-reactive DNA intercalating acridine derivative amsacrine (m-AMSA) than is its parent HL-60 line. HL-60/AMSA cells are minimally resistant to etoposide, a topoisomerase II-reactive drug that does not intercalate. Previously we showed that HL-60 topoisomerase II activity in cells, nuclei, or nuclear extracts was sensitive to m-AMSA and etoposide, while HL-60/AMSA topoisomerase II was resistant to m-AMSA but sensitive to etoposide. Now we show that purified topoisomerase II from the two cell lines exhibits the same drug sensitivity or resistance as that in the nuclear extracts although the magnitude of the m-AMSA resistance of HL-60/AMSA topoisomerase II in vitro is not as great as the resistance of the intact HL-60/AMSA cells. In addition HL-60/AMSA cells are cross-resistant to topoisomerase II-reactive intercalators from the anthracycline and ellipticine families and the pattern of sensitivity or resistance to the cytotoxic actions of the various topoisomerase II-reactive drugs is paralleled by topoisomerase II-reactive drug-induced DNA cleavage and protein cross-link production in cells and the production of drug-induced, topoisomerase II-mediated DNA cleavage and protein cross-linking in isolated biochemical systems. In addition to its lowered sensitivity to intercalators, HL-60/AMSA differed from HL-60 in 1) the susceptibility of its topoisomerase II to stimulation of DNA topoisomerase II complex formation by ATP, 2) the catalytic activity of its topoisomerase II in an ionic environment chosen to reproduce the environment found within the living cell, and 3) the observed restriction enzyme pattern on a Southern blot probed with a cDNA for human topoisomerase II. These data indicate that an m-AMSA-resistant form of topoisomerase II contributes to the resistance of HL-60/AMSA to m-AMSA and to other topoisomerase II-reactive DNA intercalating agents. The drug resistance is associated with additional biochemical and molecular alterations that may be important determinants of cellular sensitivity or resistance to topoisomerase II-reactive drugs.
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PMID:Characterization of an amsacrine-resistant line of human leukemia cells. Evidence for a drug-resistant form of topoisomerase II. 255 Apr 42

Topoisomerase inhibitors comprise an important group of agents that is used in cancer treatment. Because the development of resistance to cancer chemotherapeutic agents represents a major limitation of cancer chemotherapy, we investigated the mechanism of resistance by murine P388 leukemia to camptothecin (topoisomerase I inhibitor) or amsacrine (topoisomerase II inhibitor). The resistant cells contained reduced levels of topoisomerase activity and messenger RNA. The topoisomerase gene of these cells was rearranged (only in one allele) and hypermethylated. These topoisomerase gene alterations probably resulted in reduced transcription and, thus, enzyme production, which was correlated with resistance to the topoisomerase inhibitor.
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PMID:Nonproductive rearrangement of DNA topoisomerase I and II genes: correlation with resistance to topoisomerase inhibitors. 255 92

Previous studies have shown that DNA topoisomerase II enzyme activity and protein levels are reduced in cloned lines of Adriamycin-resistant P388 leukemia cells relative to drug-sensitive cells (Deffie et al., Cancer Res., 49: 58-62, 1989). The molecular basis of the reduced topoisomerase II levels in these resistant cells has been investigated. Northern blot analysis of total cellular RNA from drug-sensitive and -resistant cells using a 1.8-kilobase human topoisomerase II complementary DNA revealed the presence of two mRNA species: a 6.6-kilobase transcript that was strongly expressed in drug-sensitive cells but reduced 7- to 8-fold in resistant cells; and a 5.5-kilobase transcript detected only in drug-resistant cells. Southern blot analysis of genomic DNA digested with BamHI, StuI, or PvuII and probed with the 1.8-kilobase complementary DNA for human topoisomerase II showed that, in Adriamycin-resistant cells, there were two different alleles for topoisomerase II, one identical to the native allele but with a lower gene copy number than that found in sensitive cells, and a second allele containing a mutation present only in resistant cells. These findings suggest that the reduced levels of topo II protein in drug-resistant cells may be due to reduced amounts of the native 6.6-kilobase mRNA. The unique 5.5-kilobase mRNA in resistant cells may represent a shortened transcript of the mutated topoisomerase II allele.
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PMID:Evidence for a mutant allele of the gene for DNA topoisomerase II in adriamycin-resistant P388 murine leukemia cells. 255 55

The formation and disappearance of DNA single-strand breaks (SSB) produced by 4-demethoxydaunorubicin (4-dmDR) in P388 murine leukemia cells and in a resistant subline were examined by alkaline elution methods in relation to cellular pharmacokinetics. DNA strand breaks produced by this intercalating agent were essentially DNA lesions mediated by topoisomerase II, even at very high drug concentrations, since they were detected as protein-associated breaks by filter elution. Similarly, the appearance of delayed DNA breaks in cells exposed to high concentrations, following drug removal, showed predominance of protein-associated breaks, thus supporting a similar mechanism of breakage induction. This finding indirectly suggests that, in this experimental model, free radical production makes little (if any) contribution to DNA damage, and also that DNA effects are not the consequence of early cell death. In contrast to a rapid disappearance of protein-associated strand breaks produced by intercalating agents and topoisomerase II inhibitors of different classes, DNA breaks induced by low concentrations of the anthracycline derivative are only partially reversible following drug removal, but they persisted and even increased with high concentrations. Thus, not only the extent of DNA breaks but also their persistence may contribute to the cytotoxic potency of anthracyclines. The importance of DNA lesions to cytotoxic action of the anthracycline is also emphasized by drug effect on the resistant line. A negligible effect on DNA of resistant cells was detected at drug concentrations lethal to sensitive cells. However, exposure to equitoxic drug concentrations resulted in a comparable amount of DNA breaks in sensitive and resistant cells. Although faster DNA rejoining in resistant cells may be in part attributable to increased efflux of drug, no correlation exists between cell drug accumulation and extent of DNA lesions. With equitoxic drug concentrations cellular drug content was higher in resistant cells, suggesting an intrinsic insensitivity of this variant to DNA cleavage effects of the anthracycline.
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PMID:Formation, resealing and persistence of DNA breaks produced by 4-demethoxydaunorubicin in P388 leukemia cells. 255 70


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