novobiocin and Adenocarcinoma

To explore the mechanism of cisplatin resistance and its reversion in human ovarian cancer.. A cisplatin resistant cell subline of SKOV3, SKOV3/cp, was established, and a xenograft mice model of human ovarian cancer was established by microencapsulation technology. Various biochemical changes and the effects of modulators on the resistance in the model were observed.. The intracellular platinum accumulation. Pt-DNA adducts and interstrand cross links of DNA (ISC) in SKOV3 was 5.1, 2.4 and 4.8 times respectively of those in SKOV3/cp cell line. Amphotericin B (AmB) and Novobiocin (NVB) could raise platinum accumulation and Pt-DNA adducts concentration in SKOV3/cp and this resulted in reversion of cisplatin resistance.. The primary factors resulting in SKOV3/cp resistance to cisplatin are the reduction of intracellular drugs and the augmentation of the ability to remove Pt-DNA adducts. AmB and NVB can reverse cisplatin resistance in SKOV3/cp cells.

Topics: Adenocarcinoma; Amphotericin B; Animals; Antibiotics, Antineoplastic; Cisplatin; DNA Adducts; Drug Resistance, Neoplasm; Female; Humans; Mice; Mice, Inbred BALB C; Neoplasm Transplantation; Novobiocin; Ovarian Neoplasms; Tumor Cells, Cultured

Previous reports from this laboratory have demonstrated that novobiocin produces supraadditive cytotoxicity and increases the formation of drug-stabilized topoisomerase II-DNA covalent complexes in WEHI-3B myelomonocytic leukemia and A549 lung carcinoma cells when combined with etoposide (VP-16). Inhibition of the efflux of VP-16 by novobiocin is responsible for the increase in VP-16 accumulation, which in turn leads to increased formation of VP-16-stabilized topoisomerase II-DNA covalent complexes and increased cytotoxicity. We now report that novobiocin synergistically enhanced the sensitivity of the multidrug resistant variants, WEHI-3B/NOVO and A549(VP)28, to VP-16, causing almost complete reversal of the resistance to the epipodophyllotoxin. These two tumor cell variants are resistant to several topoisomerase II-targeted drugs, particularly VP-16, but not to Vinca alkaloids; this finding corresponds to the fact that they do not overexpress the P-glycoprotein. The effects of novobiocin in these resistant sublines are mediated through the intracellular accumulation of VP-16, resulting in an increase in the formation of lethal VP-16-induced topoisomerase II-DNA covalent complexes. In the P-glycoprotein expressing multidrug resistant HCT116(VM)34 colon carcinoma and L1210/VMDRC0.06 leukemia cell lines, the latter being transfected with the human mdr-1 gene, novobiocin did not potentiate the cytotoxic activity of VP-16 nor increase the intracellular accumulation of VP-16 and the formation of covalent complexes, whereas their normal counterparts were sensitive to the potentiating activity of novobiocin when used in combination with VP-16. These results indicate that the action of novobiocin on the intracellular transport of VP-16 is not directed at the level of the P-glycoprotein, but that the action of novobiocin is antagonized by the presence of the P-glycoprotein. Since novobiocin is a clinically available antibiotic, has numerous structural analogues available for comparative studies, and has a relatively low toxicity profile, this drug, as well as structurally related agents, would appear to have significant clinical potential in combination with an epipodophyllotoxin for the treatment of non-P-glycoprotein expressing multidrug resistant tumors.

Topics: Adenocarcinoma; Animals; ATP Binding Cassette Transporter, Subfamily B, Member 1; Carrier Proteins; Colonic Neoplasms; DNA Topoisomerases, Type II; DNA, Neoplasm; Drug Resistance; Etoposide; Flow Cytometry; Humans; Leukemia L1210; Lung Neoplasms; Membrane Glycoproteins; Mice; Novobiocin; Tumor Cells, Cultured

Topoisomerase I and topoisomerase II allow a metabolically active cell to mobilize its supercoiled chromosomal DNA and undergo replication, transcription, recombination, and repair. Several topoisomerase inhibitors have recently been shown to be active in preclinical systems. Topotecan (SK&F 104,864), a water-soluble camptothecin analog, is an inhibitor of topoisomerase I. Novobiocin is an inhibitor of topoisomerase II. Lonidamine depletes cellular adenosine 5'-triphosphate (ATP) and may impede energy-dependent DNA repair, MCF-7 human breast-cancer cells were treated in vitro with topotecan, novobiocin, and lonidamine alone, in paired combinations, and in combination with CDDP and melphalan. The three enzyme inhibitors alone and in combination did not increase tumor cell sensitivity to CDDP. However, the combinations of topotecan/novobiocin and lonidamine/novobiocin did enhance the cytotoxicity of melphalan. Mice bearing the FSaII fibrosarcoma were treated in vivo with topotecan, novobiocin, and lonidamine alone, in paired combinations, and in combination with CDDP, melphalan, BCNU, and cyclophosphamide. The combination of topotecan/novobiocin had the greatest impact on tumor cell sensitivity to each cytotoxic agent tested in both tumor cell-survival and tumor growth-delay assays. This sensitization was greatest at the highest concentrations of the cytotoxic agent tested. Combinations of topoisomerase I and topoisomerase II inhibitors may be useful as modulators of antitumor alkylating agents.

Topics: Adenocarcinoma; Alkylating Agents; Animals; Antineoplastic Combined Chemotherapy Protocols; Breast Neoplasms; Camptothecin; Drug Synergism; Female; Fibrosarcoma; Humans; Indazoles; Male; Mice; Mice, Inbred C3H; Novobiocin; Topotecan; Tumor Cells, Cultured

The coumermycin antibiotic novobiocin, which interacts with the nuclear enzyme topoisomerase II, produced supra-additive toxicity to WEHI-3B D+ leukemia cells at clinically achievable concentrations, when combined with teniposide (VM-26) or etoposide (VP-16). Simultaneous exposure of cells to both agents was required for maximum efficacy of the combination. Novobiocin also produced supra-additive toxicity to A549 human lung carcinoma cells when combined with VM-26 or VP-16. At concentrations above the peak plasma levels achievable in patients, novobiocin lost its potentiating activity. Exposure of WEHI-3B D+ cells to novobiocin did not modify the cytotoxicity produced by the topoisomerase II inhibitor m-AMSA, whereas, in contrast, novobiocin antagonized the cytotoxicity of m-AMSA in A549 cells. Although it has been suggested that inhibitors of the syntheses of DNA and RNA interfere with the cytotoxic activity of the epipodophyllotoxins, maximum potentiation of the cytotoxicities of VP-16 and VM-26 occurred at novobiocin concentrations that decreased the rates of synthesis of both DNA and RNA in WEHI-3B D+ cells by about 50%. The number of DNA-topoisomerase-II covalent complexes stabilized by VM-26 in WEHI-3B D+ cells was greatly increased when cells were exposed simultaneously to VM-26 and novobiocin for 1 hr, but not when cells were treated with m-AMSA and novobiocin for the same period of time. Novobiocin did not affect the amount of covalent complexes produced by VM-26 in isolated nuclei, suggesting that the potentiating activity of novobiocin was not due to its direct interaction with the nuclear topoisomerase II enzyme. Our findings suggest that therapeutic levels of novobiocin may be capable of enhancing the clinical activities of VP-16 and VM-26.

Topics: Adenocarcinoma; Amsacrine; Antineoplastic Combined Chemotherapy Protocols; Cell Survival; DNA; DNA Topoisomerases, Type II; Drug Synergism; Etoposide; Humans; Leukemia; Lung Neoplasms; Novobiocin; RNA; Teniposide; Topoisomerase II Inhibitors; Tumor Cells, Cultured

The effect of novobiocin, a coumarin class antibiotic, on rat ribosomal gene (rDNA) transcription in a fractionated extract derived from adenocarcinoma ascites cells (fraction DE-B) was studied. This drug inhibited transcription of rDNA by blocking initiation of transcription, whereas it had no effect on the elongation of the rRNA transcript. Order of addition experiments indicated that the novobiocin effect was at a step(s) in preinitiation complex formation. Preincubation of fraction DE-B with ATP before exposure to this antibiotic prevented inhibition of rDNA transcription. Since novobiocin has been shown to inhibit RNA polymerases II- and III-directed transcription of linear DNAs by interfering with a step(s) in the initiation reaction, these data suggest that initiation of transcription of all classes of RNA is inhibited by novobiocin by a mechanism independent of its effect on DNA topoisomerase II.

Topics: Adenocarcinoma; Animals; DNA Topoisomerases, Type II; DNA, Ribosomal; Novobiocin; Plasmids; Rats; RNA Polymerase I; Transcription, Genetic