elsamicin-a and chartreusin

Chartreusin and elsamicin A are structurally related antibiotics that bind to GC-rich tracts in DNA, with a clear preference for B-DNA over Z-DNA. They inhibit RNA synthesis and cause single-strand scission of DNA via the formation of free radicals. Elsamicin A can also be regarded as the most potent inhibitor of topoisomerase II reported so far. It can inhibit the formation of several DNA-protein complexes. Elsamicin A binding to the P1 and P2 promoter regions of the c-myc oncogene inhibits the binding of the Sp1 transcription factor, thus inhibiting transcription. Despite the pharmacological interest in chartreusin, elsamicin A and their derivatives, there is no experimental data on the structure of their complexes with DNA. This shortcoming has been partially solved by a theoretical approach, which provided some details about the DNA-elsamicin A interaction, and the thermodynamic characterization of the binding of chartreusin and elsamicin A to DNA. Elsamicin A but not chartreusin is being developed clinically as an anti-cancer agent. IST-622 (6-O-(3-ethoxypropylonyl)-3',4'-O-exo-benzylidene-chartreusin), a novel semi-synthetic derivative of chartreusin, which has shown a promising anti-cancer activity in a phase II study, appears to be a pro-drug with a more suitable pharmacokinetic profile than chartreusin.

Topics: Aminoglycosides; Animals; Antibiotics, Antineoplastic; Benzopyrans; Binding Sites; DNA; Glycosides; Humans

The antitumor drug elsamicin A contains a coumarin-related chartarin chromophore that intercalates into DNA. It differs from other related molecules in its disaccharide moiety, which bears an amino sugar. Its binding to DNA was analyzed using isothermal titration calorimetry and UV thermal denaturation, and characterized thermodynamically. For the association of elsamicin A with DNA we found DeltaG degrees = -8.6 kcal mol(-1), DeltaH = -10.4 kcal mol(-1), DeltaS = -6.1 cal mol(-1) K(-1), and Kobs = 2.8(+/- 0.2) x 10(6) M(-1) at 20 degrees C in 18 mM Na+. The contributions to the free energy of binding that lead to the DNA-elsamicin complex are compared with the binding to DNA of chartreusin, another chartarin-containing drug. The results are discussed in terms of the contributions of the disaccharide moieties into the strength of binding.

Topics: Aminoglycosides; Antibiotics, Antineoplastic; Benzopyrans; Calorimetry; Disaccharides; DNA; Glycosides; Molecular Structure; Nucleic Acid Denaturation; Temperature; Thermodynamics

Topics: Aminoglycosides; Anti-Bacterial Agents; Antibiotics, Antineoplastic; Benzopyrans; DNA Topoisomerases, Type I; DNA, Circular; DNA, Superhelical; Electrophoresis, Agar Gel; Escherichia coli; Ethidium; Eukaryotic Cells; Glycosides; Humans; Inhibitory Concentration 50; Magnesium; Molecular Structure; Nucleic Acid Conformation; Nucleic Acid Denaturation; Oxazines; Plasmids; Polyamines; Quinolines; Topoisomerase I Inhibitors; Tumor Cells, Cultured

The cytostatic agent Elsamitrucin is a new fermentation product active in a variety of in vivo tumor models of murine and human origin. To determine its pharmacokinetics during the clinical phase I trial, an HPLC procedure was developed and validated. Plasma samples were extracted after addition of the internal standard, i.e. the analog Chartreusin. Urine samples were injected without extraction of the samples. Because of the wide concentration range of Elsamitrucin in the plasma samples two standard curves were used: up to 100 nM and from 100-1000 nM. Recoveries of Elsamitrucin from plasma were 87% and 74% for concentrations lower and higher than 100 nM, respectively. The detection limits were 1 nM in plasma and 7.5 nM in urine at a signal-to-noise ratio of 3. The accuracy ranged from 95-107% for plasma and from 96-104% for urine. The within-day precision was < or = 4.8% and < or = 2.8% in plasma and urine, respectively. The between-day precision was < or = 4.4% and < or = 7.1% in plasma and urine, respectively. The method proved to be sufficiently sensitive, specific and accurate for analysis of clinical samples for pharmacokinetic purposes.

Topics: Aminoglycosides; Anti-Bacterial Agents; Antibiotics, Antineoplastic; Benzopyrans; Chromatography, High Pressure Liquid; Glycosides; Humans; Spectrometry, Fluorescence

Elsamicin (EM) is a recently discovered antitumour agent that is structurally related to several other compounds displaying anticancer activities, including chartreusin (CT), chrysomycin V (CV) and M (CM), gilvocarcin V (GV) and ravidomycin (RM). The biochemical events resulting in cytotoxicity for most of these compounds have not been clearly elucidated. There is some evidence that GV and CT bind to DNA and that GV is photosensitive, causing DNA damage. Therefore, we investigated the effects of these chemicals on DNA in cells and on pBR322 plasmid DNA. Using alkaline elution techniques, we found that all these compounds induced, to a different extent, DNA breakage in the human lung adenocarcinoma A549 cell line. In addition, all either bound to or intercalated into DNA, as indicated by their ability to alter the electrophoretic migration of DNA in agarose gels. Using the P4 unknotting assay, EM, CT, CV, CM, GV and RM were found to be potent inhibitors of the catalytic activity of topoisomerase II (topo II). Their potencies were compared with the known topo II inhibitors teniposide (VM-26) and doxorubicin (DX). EM was the most potent, with an IC50 of 0.4 mumol/l followed in order by CV, GV, and CT. VM-26 was the least potent with an IC50 of 15 mumol/l. It was concluded from these results that EM, GV, CV, CM and CT are capable of inhibiting topo II and that EM is the most potent inhibitor of topo II yet discovered.

Topics: Adenocarcinoma; Aminoglycosides; Anti-Bacterial Agents; Antibiotics, Antineoplastic; Benzopyrans; Cell Division; Coumarins; DNA Damage; DNA, Neoplasm; Glycosides; Humans; Lung Neoplasms; Topoisomerase II Inhibitors; Tumor Cells, Cultured

The in vitro activity of elsamicin A (ELS) was investigated compared with that of doxorubicin (DX) on two sensitive breast cancer cell lines: one estrogen receptor-positive (ER+, MCF7) and one estrogen receptor-negative (ER-, MDA-MB-231) line, and on a DX-resistant subline (MCF7DX). The activity of the two drugs was also investigated on 19 clinical breast cancer specimens from untreated patients. The drugs were tested at pharamcologically relevant concentrations, as calculated from the area under the curve for a 3 h exposure to the lethal dose producing 10% mortality (LD10) in mice, and at 10- and 100-fold concentrations. In DX-sensitive lines, a greater inhibition of RNA and DNA precursor incorporation, as well as of cell proliferation, was caused by ELS than by DX. Moreover, the antiproliferative effect was 10-fold higher in the ER+ MCF7 than in the ER- MDA-MB-231 cell line (IC50: 0.25 versus 0.21 micrograms/ml). ELS was cross-resistant to DX in the MCF7DX subline. In clinical specimens, effects on DNA precursor incorporation were more often observed for ELS than for DX at the same drug concentrations. The in vitro sensitivity to ELS was more pronounced for ER+ than for ER- tumors: minimal inhibiting concentrations of the drug were 0.1 and 3.5 micrograms/ml, respectively, in the two groups. If confirmed in a larger series of human breast tumors, these in vitro results would indicate a promising role for ELS in clinical treatment, mainly of ER+ breast cancer patients.

Topics: Adenocarcinoma; Aminoglycosides; Animals; Anti-Bacterial Agents; Antibiotics, Antineoplastic; Benzopyrans; Breast Neoplasms; Cell Division; DNA, Neoplasm; Doxorubicin; Drug Resistance; Female; Glycosides; Humans; Mice; Receptors, Estrogen; RNA, Neoplasm; Tumor Cells, Cultured

We report guanine-specific recognition and selective cleavage of DNA by the antitumor antibiotic elsamicin A equipped with an amino sugar and compare these results with cleavage by chartarin and chartreusin antibiotics. The preferential cutting sites of DNA strand scission with elsamicin A are on the bases adjacent to the 3'-side of guanine residues such as 5'-GN sites, in particular 5'-GG sites. The present results also indicate that (1) the aglycon portion binds intercalatively to the 3'-side of guanine in host DNA, (2) the guanine 2-amino group has an important effect on selective DNA binding of elsamicin A, and (3) the amino sugar residue of elsamicin A facilitates the drug binding into the minor groove of B-DNA. In addition, we found that an acetylation of the amino group on the elsamicin A sugar portion plays an interesting switch function for the activity of elsamicin A. The biological implication of this switch has also been discussed.

Topics: Aflatoxin B1; Aflatoxins; Amino Sugars; Aminoglycosides; Anti-Bacterial Agents; Antibiotics, Antineoplastic; Autoradiography; Base Sequence; Benzopyrans; Distamycins; DNA; DNA Damage; DNA Fingerprinting; Electron Spin Resonance Spectroscopy; Electrophoresis, Agar Gel; Glycosides; Lactones; Molecular Sequence Data; Spectrometry, Fluorescence

Three DNA restriction fragments designated tyrT, 102-mer and 70-mer, have been used as substrates for footprinting studies using DNase I in the presence of the structurally similar antibiotics chartreusin and elsamicin A. The sequence-selective binding sites of the antibiotics can be mapped in regions which are rich in guanine + cytosine. Chartreusin and elsamicin appear to recognize and bind preferentially to sequences containing a CpG step. Regions containing a TpG step also seem to be a good binding site. The binding of elsamicin to these sites appears to be more concentration-dependent. A comparative analysis is performed of the sizes and locations of the different binding sites, aimed to infer whether the different biological effects of chartreusin and elsamicin A can be correlated to differences in their sequence-selective binding to DNA.

Topics: Aminoglycosides; Anti-Bacterial Agents; Base Sequence; Benzopyrans; Binding Sites; DNA; DNA Fingerprinting; Glycosides; Molecular Sequence Data; Restriction Mapping

There are a considerable number of DNA binding natural products equipped with amino sugar residues. The amino sugar of elsamicin A significantly takes part in DNA binding and antitumor activity. In addition, we found that an acetylation of the amino group on elsamicin A sugar portion plays an important switch-function for the activity of elsamicin A. The biological implication of this switch has been discussed.

Topics: Acetylation; Amino Sugars; Aminoglycosides; Anti-Bacterial Agents; Antibiotics, Antineoplastic; Benzopyrans; DNA Damage; DNA, Circular; DNA, Superhelical; Electrophoresis, Agar Gel; Glycosides; Molecular Structure

New antitumor antibiotics, elsamicins A and B, were isolated from the culture broth of an unidentified actinomycete strain J907-21 (ATCC 39417). They are structurally related to chartreusin, containing the common aglycone, chartarin, but contain different sugar moieties. Elsamicin A, the major component, has an amino sugar in the molecule which makes the antibiotic much more water-soluble than chartreusin. Elsamicin A exhibits strong inhibitory activity against various murine tumors including leukemia P388, leukemia L1210, and melanoma B16 but elsamicin B which lacks the amino sugar showed only marginal activity. The potency of elsamicin A was 10-30 times more potent than that of chartreusin in terms of minimum effective dose.

Topics: Actinomycetales; Aminoglycosides; Animals; Anti-Bacterial Agents; Antibiotics, Antineoplastic; Bacteria; Benzopyrans; Chemical Phenomena; Chemistry; Fermentation; Glycosides; Mice; Mice, Inbred Strains; Neoplasms, Experimental