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Molecular oxygen (O 2 )-utilizing enzymes are among the most important in biology. The abundance of O 2 , its thermodynamic power, and the benign nature of its end products have raised interest in oxidases and oxygenases for biotechnological applications. Although most O 2 -dependent enzymes have an absolute requirement for an O 2 -activating cofactor, several classes of oxidases and oxygenases accelerate direct reactions between substrate and O 2 using only the protein environment. Nogalamycin monooxygenase (NMO) from Streptomyces nogalater is a cofactor-independent enzyme that catalyzes rate-limiting electron transfer between its substrate and O 2 Here, using enzyme-kinetic, cyclic voltammetry, and mutagenesis methods, we demonstrate that NMO initially activates the substrate, lowering its p K a by 1.0 unit (Δ G * = 1.4 kcal mol -1 ). We found that the one-electron reduction potential, measured for the deprotonated substrate both inside and outside the protein environment, increases by 85 mV inside NMO, corresponding to a ΔΔ G 0 ' of 2.0 kcal mol -1 (0.087 eV) and that the activation barrier, Δ G ‡ , is lowered by 4.8 kcal mol -1 (0.21 eV). Applying the Marcus model, we observed that this suggests a sizable decrease of 28 kcal mol -1 (1.4 eV) in the reorganization energy (λ), which constitutes the major portion of the protein environment's effect in lowering the reaction barrier. A similar role for the protein has been proposed in several cofactor-dependent systems and may reflect a broader trend in O 2 -utilizing proteins. In summary, NMO's protein environment facilitates direct electron transfer, and NMO accelerates rate-limiting electron transfer by strongly lowering the reorganization energy., (© 2019 Machovina et al.)

Nogalamycin is an anthracycline polyketide antibiotic that contains two deoxysugars, at positions C-1 and C-7. Previous biosynthetic studies conducted in vivo affiliated snoaL2 with an unusual C-1 hydroxylation reaction, but in vitro activity was not established. Here, we demonstrate that inactivation of either snoaL2 or snoaW resulted in accumulation of two nonhydroxylated metabolites, nogalamycinone and a novel anthracycline 3',4'-demethoxy-nogalose-nogalamycinone. The C-1 hydroxylation activity was successfully reconstructed in vitro in the presence of the two enzymes, NAD(P)H and the substrates. Based on relative reaction efficiencies, 3',4'-demethoxy-nogalose-nogalamycinone was identified as the likely natural substrate. A biosynthetic model was established where the atypical short-chain alcohol dehydrogenase SnoaW reduces the anthraquinone to a dihydroquinone using NADPH, which enables activation of oxygen and formation of a hydroperoxy intermediate. Finally, protonation of the intermediate by SnoaL2 yields the 1-hydroxylated product., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Vaccinia DNA topoisomerase forms a covalent DNA-(3'-phosphotyrosyl)-enzyme intermediate at a specific target site 5'-C(+5)C(+4)C(+3)T(+2)T(+1)p downward arrow N(-1) in duplex DNA. Here we study the effects of position-specific DNA intercalators on the rate and extent of single-turnover DNA transesterification. Chiral C-1 R and S trans-opened 3,4-diol 1,2-epoxide adducts of benzo[c]phenanthrene (BcPh) were introduced at single N2-deoxyguanosine and N6-deoxyadenosine positions within the 3'-G(+5)G(+4)G(+3)A(+2)A(+1)T(-1)A(-2) sequence of the nonscissile DNA strand. Transesterification was unaffected by BcPh intercalation between the +6 and +5 base pairs, slowed 4-fold by intercalation between the +5 and +4 base pairs, and virtually abolished by BcPh intercalation between the +4 and +3 base pairs and the +3 and +2 base pairs. Intercalation between the +2 and +1 base pairs by the +2R BcPh dA adduct abolished transesterification, whereas the overlapping +1S BcPh dA adduct slowed the rate of transesterification by a factor of 2700, with little effect upon the extent of the reaction. Intercalation at the scissile phosphodiester (between the +1 and -1 base pairs) slowed transesterification by a factor of 450. BcPh intercalation between the -1 and -2 base pairs slowed cleavage by two orders of magnitude, but intercalation between the -2 and -3 base pairs had little effect. The anthracycline drug nogalamycin, a non-covalent intercalator with preference for 5'-TG dinucleotides, inhibited the single-turnover DNA cleavage reaction of vaccinia topoisomerase with an IC50 of 0.7 microM. Nogalamycin was most effective when the drug was pre-incubated with DNA and when the cleavage target site was 5'-CCCTT/G instead of 5'-CCCTT/A. These findings demarcate upstream and downstream boundaries of the functional interface of vaccinia topoisomerase with its DNA target site.

Telomeres are the ends of the linear chromosomes of eukaryotes and consist of tandem GT-rich repeats in telomere sequence i.e. 500-3000 repeats of 5'-TTAGGG-3' in human somatic cells, which are shortened gradually with age. The G-rich overhang of telomere sequence can adopt different intramolecular fold-backs and tetra-stranded DNA structures, in vitro, which inhibit telomerase activity. In this report, DNA binding agents to telomere sequence were studied novel therapeutic possibility to destabilize telomeric DNA sequences. Oligonucleotides containing the guanine repeats in human telomere sequence were synthesized and used for screening potential antitumor drugs. Telomeric DNA sequence was characterized using spectral measurements and CD spectroscopy. CD spectrum indicated that the double-stranded telomeric DNA is in a right-handed conformation. Polyacrylamide gel electrophoresis was performed for binding behaviors of antitumor compounds with telomeric DNA sequence. Drugs interacted with DNA sequence caused changes in the electrophoretic mobility and band intensity of the gels. Depending on the binding mode of the anticancer drugs, telomeric DNA sequence was differently recognized and the efficiency of cleavage of DNA varies in the bleomycin-treated samples under different conditions. DNA cleavage occurred at about 1% by the increments of 1 micromM bleomycin-Fe(III). These results imply that the stability of human telomere sequence is important in conjunction with the cancer treatment and aging process.

Previous work has demonstrated that sequence-selective DNA-binding drugs can inhibit transcription factors from binding to their target sites on gene promoters. In this study, the potency and effectiveness of DNA-binding drugs to inhibit transcription were assessed using the c-fos promoter's serum response element (SRE) as a target. The drugs chosen for analysis included the minor groove binding agents chromomycin A(3) and Hoechst 33342, which bind to G/C-rich and A/T-rich regions, respectively, and the intercalating agent nogalamycin, which binds G/C-rich sequences in the major groove. The transcription factors targeted, Elk-1 and serum response factor (SRF), form a ternary complex (TC) on the SRE that is necessary and sufficient for induction of c-fos by serum. The drugs' abilities to prevent TC formation on the SRE in vitro were nogalamycin > Hoechst 33342 > chromomycin. Their potencies in inhibiting cell-free transcription and endogenous c-fos expression in NIH3T3 cells, however, were chromomycin > nogalamycin > Hoechst 33342. The latter order of potency was also obtained for the drugs' cytotoxicity and inhibition of general transcription as measured by [(3)H]uridine incorporation. These systematic analyses provide insight into how drug and transcription factor binding characteristics are related to drugs' effectiveness in inhibiting gene expression.

The X-ray crystal structure of d(TGCGCA)2 has been determined at 120 K to a resolution of 1.3 A. Hexamer duplexes, in the Z-DNA conformation, pack in an arrangement similar to the 'pure spermine form' [Egli et al. (1991). Biochemistry, 30, 11388-11402] but with significantly different cell dimensions. The phosphate backbone exists in two equally populated discrete conformations at one nucleotide step, around phosphate 11. The structure contains two ordered cobalt hexammine molecules which have roles in stabilization of both the Z-DNA conformation of the duplex and in crystal packing. A comparison of d(TGCGCA)2 with other Z-DNA hexamer structures available in the Nucleic Acid Database illustrates the elusive nature of crystal packing. A review of the interactions with the metal cations Na+, Mg2+ and Co3+ reveals a relatively small proportion of phosphate binding and that close contacts between metal ions are common. A prediction of the water structure is compared with the observed pattern in the reported structure.

The sno gene cluster in Streptomyces nogalater ATCC 27451 contains the nogalamycin biosynthesis genes. A set of plasmid constructions carrying fragments of the sno cluster that lie downstream of snoD were used to complement the S. galilaeus mutant H039, which is blocked in rhodosamine and 2-deoxyfucose biosynthesis in the aclacinomycin pathway. Sequence analysis of this cluster revealed three contiguous open reading frames (ORFs) that were designated snoF, snoG, and snoH. Only those plasmid constructs that expressed SnoG were able to complement H039. SnoG shows similarity to GalE, a UDP-glucose-4-epimerase catalyzing the epimerization of UDP-glucose to UDP-galactose. The putative SnoF protein is similar to 3,5-epimerases involved in rhamnose biosynthesis. The deduced product of snoH is a 489-amino acid polypeptide. It is similar to the product of dau ORF3 found in the daunomycin cluster. However its function is still unclear. Based on the complementation experiments and sequence analysis, this part of the sno cluster is suggested to be involved in the biosynthesis of the sugar portion of nogalamycin. Interestingly, SnoA, a transcriptional activator for the sno minimal polyketide synthase, is also needed to express this cluster.

As part of an investigation into the sequence selectivity of the nogalamycin-DNA interaction, the 1.58 A structure of nogalamycin complexed with d5'(TGTACA)2 has been determined by single-crystal X-ray analysis. The complex crystallised in the orthorhombic space group P2(1)2(1)2(1) with cell dimensions a = 26.3 A, b = 52.0 A and c = 67.1 A, incorporating two B-DNA duplexes and four nogalamycin molecules in the asymmetric unit. The final refined structure included 97 water molecules, one spermine molecule, two acetate ions and one sodium ion, yielding an overall R factor of 19.2% (calculated using all 12,358 reflections in the resolution range 10.7 to 1.6 A) and an Rtree of 23.7% (using 1229 test reflections). The d5'(TGTACA)2 sequence was designed to include the d5'(TpG) pyrimidine-purine base step that has been ascertained as a preferential intercalation site. The complexes in the asymmetric unit are globally similar; one nogalamycin molecule intercalates between each d5'(TpG) step in each duplex. The DNA of each complex exists as a distorted B-DNA duplex displaying some Z-DNA character in the form of C3' endo sugars at some residues. Structural comparisons between the d5'(TGTACA)2-nogalamycin2 complex and the complexes of this drug with the sequences d5'(TGATCA)2 and d5'(5MeCGT(pS)A5MeCG)2 highlight differences in binding interactions between nogalamycin and these various triplet DNA binding sites, with regards to the stability of drug intercalation, which in turn is correlated to effective levels of cytotoxicity towards tumour cells. The number of both direct and water-mediated hydrogen bonds and van der Waal's interactions between substituents of nogalamycin and the d5'(TGTACA)2 and d5'(5MeCGT(pS)A5MeCG)2 sequences are significantly greater than those made with the d5'(TGATCA)2 sequence, suggesting that the central d5'(TpA) in the former confers additional stability to the complex once the drug has bound.

We have used a modification of the footprinting technique to measure the dissociation of mithramycin, echinomycin and nogalamycin from their binding sites in a natural DNA fragment. Complexes with radiolabelled DNA were dissociated by addition of unlabelled DNA. Samples were removed at various times and subjected to DNase I digestion, and the rate of dissociation from each site was estimated from the time-dependent disappearance of the footprints. For echinomycin the slowest rate of dissociation is from ACGT, while the slowest site for mithramycin contains four contiguous guanines. The dissociation of nogalamycin is extremely slow, even from its weaker sites; the slowest rate was from ACGTA, which took longer than 4 h, even at 37 degrees C.

Defects in DNA, e.g., unpaired/bulged nucleotides, are repaired by specific repair enzymes. Understanding the dynamics and structure of DNA defects is important. Two DNA heptamers, CTb-GTACG and CGTACTbG, each containing a bulged T nucleotide embedded in the CpG step, have been studied by NMR. Both duplexes are significantly destabilized, and the bulged T remains intrahelical. Binding of the anthracycline antitumor antibiotic nogalamycin (Ng) to these two heptamers stabilizes the duplex structure. The solution structures of the 2:1 complexes of Ng-d(CTbGTACG) and Ng-d(CGTACTbG) have been determined by the NOE-restrained refinement procedure. In both structures the elongated aglycon of Ng is intercalated between base pairs, and the nogalose and aminoglucose lie in the minor and major grooves, respectively. The bulged T behaves differently upon the binding of Ng. In Ng-CTbGTACG wobble G6:Tb base pairs are formed, leaving two dangling 5'-C1 nucleotides; whereas in Ng-CGTACTbG weak C1:Tb base pairs are formed, leaving two dangling 3'-G6 nucleotides. Thus Ng induces the bulged T and the opposing base in the duplex to stack on the aglycon and causes the base next to Tb to unpair, mimicking a "frame-shift". Such structural rearrangement of a bulged DNA site due to the binding of an intercalator drug may perturb the recognition of DNA defects by repair enzymes or may cause mutation during replication.

We have studied the DNA sequence binding preference of the antitumour antibiotic nogalamycin by DNase-I footprinting using a variety of DNA fragments. The DNA fragments were obtained by cloning synthetic oligonucleotides into longer DNA fragments and were designed to contain isolated ligand-binding sites surrounded by repetitive sequences such as (A)n.(T)n and (AT)n. Within regions of (A)n.(T)n, clear footprints are observed with low concentrations of nogalamycin (< 5 microM), with apparent binding affinities for tetranucleotide sequences which decrease in the order TGCA > AGCT = ACGT > TCGA. In contrast, within regions of (AT)n, the ligand binds best to AGCT; binding to TCGA and TGCA is no stronger than to alternating AT. Within (ATT)n, the preference is for ACGT > TCGA. Although each of these binding sites contains all four base pairs, there is no apparent consensus sequence, suggesting that the selectivity is affected by local DNA dynamic and structural effects. At higher drug concentrations (> 25 microM), nogalamycin prevents DNAse-I cleavage of (AT)n but shows no interaction with regions of (AC)n.(GT)n. Regions of (A)n.(T)n, which are poorly cut by DNase I, show enhanced rates of cleavage in the presence of low concentrations of nogalamycin, but are protected from cleavage at higher concentrations. We suggest that this arises because drug binding to adjacent regions distorts the DNA to a structure which is more readily cut by the enzyme and which is better able to bind further ligand molecules.

The interaction of the anthracycline antibiotic nogalamycin with the single 5'-CpG binding site at the centre of the hexamer duplex d(GACGTC)2 has been investigated in solution by NMR spectroscopy. 41 NOE constrains between antibiotic and nucleotide protons provide input parameters for the determination of a family of conformers computed using energy minimisation and restrained molecular dynamics. Nogalamycin adopts a 'threaded' binding orientation in which the drug chromophore passes through the DNA helix positioning the nogalose sugar in the minor groove and the positively charged bicycloamino sugar in the major groove. The complex is stabilised by hydrogen bonding, electrostatic and van der Waals interactions. In the major groove hydrogen bonding interactions are identified between the 2'-OH and 4'-OH groups, on the rigidly oriented bicyclo sugar, and the guanine N7 and cytosine 4-NH2 of one G.C base pair and appear to account for the requirement for a G.C base pair at the intercalation site. In the minor groove we identify a hydrogen bond between the carbonyl oxygen of the methyl ester group on ring A and the 2-NH2 group of guanine at the intercalation site. The nogalose and ring A form a continuous domain that interacts through van der Waals contacts with the floor and walls of the minor groove over a span of four basepairs, d(GACGTC)2. The NOE data together with energy-minimised structures reveal distortions of the DNA conformation involving a total helix unwinding of about 16 degrees and buckling of the G.C base pairs by about 22 degrees and -9 degrees at the intercalation site. The base pairs effectively wrap around the drug chromophore optimising van der Waals contacts between the two and minimising cavities in the structure. The solution data also reveal that the bound antibiotic substantially slows the rate of exchange of the imino protons of not only the G.C base pairs forming the intercalation site but also that of an A.T base pair which is occluded by the sugar moieties lying in each groove. The data present an opportunity for comparison with two crystal structures of nogalamycin-DNA complexes in which ligand molecules are bound at terminal 5'-CpG sites.

Heteronuclear chemical shift correlation experiments confirm that the two down-field shifted 31P resonances in the spectrum of the (nogalamycin)2-d(GCATGC)2 complex correspond to the phosphodiesters CpA and TpG at the intercalation sites. 31P relaxation measurements (R1, R2 and [1H]-31P NOE) at 4.7 and 9.4 T permit the correlation time of each phosphate to be determined together with their chemical shift anisotropies. Significant differences in deoxyribose H3'-31P coupling constants and chemical shift anisotropy contributions are observed, consistent with an asymmetric DNA backbone conformation for the phosphate groups at the intercalation sites. Large amplitude internal motions of the phosphates do not appear to contribute significantly to relaxation.

The three-dimensional molecular structures of the complexes between a novel antitumor drug nogalamycin and its derivative U-58872 with a modified DNA hexamer d[m5CGT(pS)Am5CG] have been determined at 1.7- and 1.8-A resolution, respectively, by X-ray diffraction analyses. Both structures (in space group P6(1)) have been refined with constrained refinement procedure to final R factors of 0.208 (3386 reflections) and 0.196 (2143 reflections). In both complexes, two nogalamycins bind to the DNA hexamer double helix in a 2:1 ratio with the elongated aglycon chromophore intercalated between the CpG steps at both ends of the helix. The aglycon chromophore spans across the GC Watson-Crick base pairs with its nogalose lying in the minor groove and the aminoglucose lying in the major groove of the distorted B-DNA double helix. Most of the sugars remain in the C2'-endo pucker family, except three deoxycytidine residues (terminal C1, C7, and internal C5). All nucleotides are in the anti conformation. Specific hydrogen bonds are found in the complex between the drug and guanine-cytosine bases in both grooves of the helix. One hydroxyl group of the aminoglucose donates a hydrogen bond to the N7 of guanine, while the other receives a hydrogen bond from the N4 amino group of cytosine. The orientation of these two hydrogen bonds suggests that nogalamycin prefers a GC base pair with its aglycon chromophore intercalating at the 5'-side of a guanine (between NpG), or at the 3'-side of a cytosine (between CpN) with the sugars pointing toward the GC base pair. The binding of nogalamycin to DNA requires that the base pairs in DNA open up transiently to allow the bulky sugars to go through, suggesting that nogalamycin prefers GC sequences embedded in a stretch of AT sequences.

The interactions between a novel antitumor drug nogalamycin with the self-complementary DNA hexamer d(CGTACG) have been studied by 500 MHz two dimensional proton nuclear magnetic resonance spectroscopy. When two nogalamycins are mixed with the DNA hexamer duplex in a 2:1 ratio, a symmetrical complex is formed. All non-exchangeable proton resonances (except H5' & H5") of this complex have been assigned using 2D-COSY and 2D-NOESY methods at pH 7.0. The observed NOE cross peaks are fully consistent with the 1.3 A resolution x-ray crystal structure (Liaw et al., Biochemistry 28, 9913-9918, 1989) in which the elongated aglycone chromophore is intercalated between the CpG steps at both ends of the helix. The aglycone chromophore spans across the GC Watson-Crick base pairs with its nogalose lying in the minor groove and the aminoglucose lying in the major groove of the distorted B-DNA double helix. The binding conformation suggests that specific hydrogen bonds exist in the complex between the drug and guanine-cytosine bases in both grooves of the helix. When only one drug per DNA duplex is present in solution, there are three molecular species (free DNA, 1:1 complex and 2:1 complex) in slow exchange on the NMR time scale. This equilibrium is temperature dependent. At high temperature the free DNA hexamer duplex and the 1:1 complex are completely destabilized such that at 65 degrees C only free single-stranded DNA and the 2:1 complex co-exist. At 35 degrees C the equilibrium between free DNA and the 1:1 complex is relatively fast, while that between the 1:1 complex and the 2:1 complex is slow. This may be rationalized by the fact that the binding of nogalamycin to DNA requires that the base pairs in DNA open up transiently to allow the bulky sugars to go through. A separate study of the 2:1 complex at low pH showed that the terminal GC base pair is destabilized.

The conformation and dynamics of the deoxyribose rings of a (nogalamycin)2-d(5'-GCATGC)2 complex have been determined from an analysis of 1H-1H vicinal coupling constants and sums of coupling constants (J1'-2',J1'-2",epsilon 1', epsilon 2' and epsilon 2") measured from one-dimensional n.m.r. spectra and from H-1'-H-2' and H-1'-H-2" cross-peaks in high-resolution phase-sensitive two-dimensional correlation spectroscopy (COSY) and double-quantum-filtered correlation spectroscopy (DQF-COSY) experiments. The value of J3'-4' has also been estimated from the magnitude of H-3'-H-4' cross-peaks in DQF-COSY spectra and H-1'-H-4' coherence transfer cross-peaks in two-dimensional homonuclear Hartman-Hahn spectroscopy (HOHAHA) spectra. The data were analysed, in terms of a dynamic equilibrium between North (C-3'-endo) and South (C-2'-endo) conformers, by using the graphical-analysis methods described by Rinkel & Altona [(1987) J. Biomol. Struct. Dyn. 4,621-649]. The data reveal that the sugars of the 2C-5G and 3A-4T base-pairs, which form the drug-intercalation site, have strikingly different properties. The deoxyribose rings of the 2C-5G base-pair are best described in terms of an equilibrium heavily weighted in favour of the C-2'-endo geometry (greater than 95% 'S'), with a phase angle, P, lying in the range 170-175 degrees and amplitude of pucker between 35 and 40 degrees, as typically found for B-DNA. For the deoxyribose rings of the 3A-4T base-pair, however, the analysis shows that, for 3A, the C-2'-endo and C3'-endo conformers are equally populated, whereas a more limited data set for the 4T nucleotide restricts the equilibrium to within 65-75% C-2'-endo. The deoxyribose rings of the 1G-6C base-pair have populations of 70-80% C-2'-endo, typical of nucleotides at the ends of a duplex. Although drug-base-pair stacking interactions are an important determinant of the enhanced duplex stability of the complex [Searle, Hall, Denny, & Wakelin (1988) Biochemistry 27, 4340-4349], the current findings make it clear that the same interactions can be associated with considerable variations in the degree of local structural dynamics at the level of the sugar puckers.

The kinetics of association between nogalamycin and DNA have been measured by stopped-flow spectrometry. With a naturally occurring DNA (calf thymus) the reaction profile requires not less than three exponentials for its complete description. By contrast, binding to poly(dA-dT) is fully described by two exponentials which correspond to the two faster components seen with the natural DNA, whereas binding to poly(dG-dC) is a single exponential process whose time constant is about the same as the slowest component measured with calf thymus DNA. In all cases the amplitude of each component in the decay varies considerably with polynucleotide concentration. The results are consistent with a model in which the antibiotic is only able to bind directly to regions of the DNA which are transiently perturbed, probably non-basepaired. As a result, the antibiotic interacts much faster with AT-rich rather than GC-rich DNA sequences, which may provide a basis for its apparent sequence selectivity.

We have used a laser flow cytometer to excite and quantitate the intracellular fluorescence of cells exposed in vitro and in vivo to various anthracyclines. In cells exposed to Adriamycin (ADR), intracellular drug fluorescence appeared slowly and reached a peak after 4 hr of incubation. Cells incubated with 10 micrograms/ml were 5 times more fluorescent than were cells incubated with 1 microgram/ml. Cells exposed to daunomycin were 2 to 4 times more fluorescent than were cells similarly exposed to ADR, and the intracellular appearance of daunomycin fluorescence was much more rapid. Cells exposed to N-trifluoroacetyladriamycin and carminomycin had higher amounts of intracellular fluorescence (2 to 4 times), and peak values were reached much more rapidly than in cells exposed to ADR. In cells exposed to rubidazone, fluorescence increased 2- to 4-fold with increased drug concentration and length of exposure. In contrast, nogalamycin fluorescence reached a peak after 60 min of incubation, and a 10-fold increase in drug concentration increased fluorescence only 2-fold. In animals given injections of ADR (4 mg/kg) and sacrificed after 3 hr, drug fluorescence could be detected in tumor and spleen cells. In contrast, fluorescence in heart nuclei was barely recognizable. However, incubation of isolated nuclei in ADR (1 microgram/ml) showed that bone marrow and heart nuclei had greater amounts of ADR fluorescence (2- to 3-fold) than did spleen or liver nuclei similarly treated. The use of laser flow cytometry for monitoring intracellular anthracycline transport, binding, and efflux is demonstrated.

Nogalamycin, an antitumor antibiotic, has been converted to a series of analogs by removal of the carbomethoxy group at C-10 and replacement of the neutral sugar at C-7 by other groups. Removal of the carbomethoxy group to give disnogamycin (6) followed by acidic alcoholysis gave pairs of isomeric 7-alkoxy compounds differing in configuration at C-7. Treatment of 6 with trifluoroacetic acid followed by nucleophiles gave a series of analogs having substituents at C-7 with a configuration at C-7 opposite to that of nogalamycin. Among the analogs prepared, 7-con-O-methylnogarol (7) is a highly active antitumor agent.

Menogaril is a new anthracycline analog of nogalamycin. When administered as a 72-hour continuous iv infusion the dose-limiting toxic effect of menogaril was venous irritation at dose levels that cause only mild leukopenia and minimal gastrointestinal toxicity. Pharmacokinetic studies showed that the rise in plasma concentration during infusion was first-order, with a half-life of 11.9 hours. Total-body clearance of menogaril was 204 ml/minute/m2. There were no detectable metabolites of menogaril in plasma. Urinary excretion of unchanged menogaril was 17.3% of the dose and N-demethylmenogaril was 0.5% over 72 hours. Since menogaril does not appear to be metabolized, a high degree of tissue binding is likely.

Binding of nogalamycin and adriamycin with Sarcoma-180 ascites tumor cell chromatin was studied by a spectrofluorometric method. There was significant reduction in the number of available drug binding sites per nucleotide when the chromatin was digested with DNase I for a period which releases only 7% of the chromosomal DNA. Results indicate preferential binding of these drugs with DNase I hypersensitive sites of chromatin. The DNase-I hypersensitive sites of chromatin were shown to correlate to the sequences required for gene expression. Further digestion with DNase I increases availability of drug binding sites, probably due to relaxation of the compact chromatin.

Reductive conversion of several anthracycline glycosides to their 7-deoxyaglycones occurs during their microaerophilic incubation with strains of Aeromonas hydrophila, Citrobacter freundii, and Escherichia coli. Further, extracts of microaerophilically grown A. hydrophilia catalyze DPNH-dependent reductive conversion of the same compounds. Anthracycline substrates cleaved by both whole cells and by the cell-free system include steffimycin, steffimycin B, nogalamycin, cinerubin A, and daunomycin. Investigation of glycoside cleavage as a function of both time and anthracycline concentration demonstrated the superiority of A. hydrophila over C. freundii and E. coli in regard to reaction rate and efficiency of conversion. Interestingly, some degree of anaerobicity was required for glycoside cleavage by all three organisms. Evidence supporting 7-deoxyaglycone formation via direct reductive cleavage, as opposed to a multienzyme-catalyzed process involving hydrolysis followed by dehydration and reduction, includes the following. Equilibrium mixtures of glycoside substrate and 7-deoxyaglycone product prepared using both whole cells and their extracts display no anthracycline hydrolysis products. Further, authentic steffimycinone (aglycone), the expected product of hydrolytic sugar cleavage of steffimycin, was shown to be converted to 7-deoxysteffimycinone (7-deoxyaglycone) at a rate slower than steffimycin. These data indicate that, if steffimycinone were present as an unbound metabolic intermediate, it should have been visible in the equilibrium mixture, but none was detected.

The hypothesis that sequence-selective DNA-binding antibiotics locate their preferred binding sites by a process involving migration from nonspecific sites has been tested by footprinting with DNAase I. Footprinting patterns on the tyrT DNA fragment produced by nogalamycin and actinomycin change with time after mixing the antibiotic with the DNA. Sites of protection as well as enhanced cleavage are seen to develop in a fashion which is both temperature and concentration-dependent. At certain sites cutting is transiently enhanced, then blocked. Limited evidence for slow reaction with echinomycin and mithramycin is presented, but the kinetics of footprinting with daunomycin and distamycin appear instantaneous. The feasibility of adducing direct evidence for shuffling by footprinting seems to be governed by slow dissociation of the antibiotic-DNA complex. It may also be dependent upon the mode of binding, be it intercalative or non-intercalative in character.

Stopped-flow spectrometry and simple mixing techniques have been employed to investigate the detergent-induced dissociation of anthracycline antibiotics from natural and synthetic DNAs. Both daunomycin and nogalamycin dissociate more slowly from poly(dG-dC) than from poly(dA-dT) but the difference is much more marked for nogalamycin. With an equimolar mixture of poly(dG-dC) and poly(dA-dT), or with poly(dA-dC).poly(dG-dT), dissociation of nogalamycin occurs very slowly. In all cases the release of antibiotic from a synthetic polynucleotide is a one-step process following a single exponential. Dissociation of daunomycin, adriamycin and iremycin from calf thymus DNA is a more complex reaction which requires a two-exponential fit, in contrast to earlier reports, but differences between the behaviour of the three antibiotics are minor. Dissociation of nogalamycin from natural DNA requires a three-exponential fit, is in general far slower, and depends upon the base composition, the level of binding and the time allowed for the complex to equilibrate. It is concluded that sequence selectivity is minimal or lacking for daunomycin, whereas nogalamycin binding is sequence dependent and probably involves migration of the antibiotic between DNA binding sites. There is an inverse correlation between dissociation rate constants and antibacterial potency in simple tests.

1H resonance assignments in the NMR spectra of the self-complementary hexadeoxyribonucleoside pentaphosphate d(5'-GCATGC)2 and its complex with the antibiotic nogalamycin, together with interproton distance constraints obtained from two-dimensional nuclear Overhauser effect (NOE) spectra, have enabled us to characterize the three-dimensional structure of these species in solution. In the complex described, two drug molecules are bound per duplex, in each of two equivalent binding sites, with full retention of the dyad symmetry. Twenty-eight NOE distance constraints between antibiotic and nucleotide protons define the position and orientation of the bound drug molecule. Nogalamycin intercalates at the 5'-CA and 5'-TG steps with the major axis of the anthracycline chromophore aligned approximately at right angles to the major axes of the base pairs. The nogalose sugar occupies the minor groove of the helix and makes many contacts with the deoxyribose moieties of three nucleotides along one strand of the duplex in the 5'-TGC segment. The charged dimethylamino group and hydroxyl functions of the bicyclic sugar lie in the major groove juxtaposed to the guanine base, the bridging atoms of the bicyclic sugar making contacts with the methyl group of the thymine. Thus the antibiotic is not symmetrically disposed in the intercalation site but is in close contact in both grooves with atoms comprising the 5'-TGC strand. The intercalation cavity is wedge-shaped, the major axes of the base pairs forming the site being tilted with respect to one another. All base-pair hydrogen-bonding interactions are maintained in the complex, and there is no evidence for Hoogsteen pairing. The free duplex adopts a regular right-handed B-type conformation in which all glycosidic bond angles are anti and all sugar puckers lie in the C2'-endo range. In the complex the glycosidic bond angles and the sugar puckers deviate little from those observed for the duplex alone. The presence of two bound nogalamycin molecules substantially slows the "breathing" motions of the base pairs forming the intercalation cavity, and the observation of two downfield-shifted resonances in the 31P NMR spectrum of the complex suggests a pronounced local helix unwinding at the drug binding site. The footprinting data of Fox and Waring [Fox, K.R., & Waring, M.J. (1986) Biochemistry 25, 4349-4356] imply that the highest affinity binding sites of nogalamycin have the sequence 5'-GCA (or 5'-TGC).(ABSTRACT TRUNCATED AT 400 WORDS)

The cutting pattern produced by micrococcal nuclease on three DNA fragments has been determined in the absence and presence of various DNA-binding drugs. The enzyme itself cuts almost exclusively at pA and pT bonds, showing a greater activity at (A-T)n than in homopolymeric runs of A and T. Each drug produces distinct changes in the cleavage pattern. The protected regions can not be pinpointed with sufficient precision to assess the exact drug-binding sites on account of the sequence selectivity of the enzyme, although where a direct comparison is possible these include most of those seen as DNAase I footprints. The enzyme is most useful for assessing the selectivity of drugs which bind to AT-rich regions. Several drugs protect the DNA from micrococcal nuclease attack in regions which do not contain their acknowledged best binding sites. It appears that micrococcal nuclease is sensitive to the existence of secondary drug-binding sites which are not evident with other footprinting techniques.

In a Phase I study, menogaril (7-OMEN) was administered daily for 5 days/course, every 21-28 days. Dosages of 3.5, 7, 11.5, 17, and 31.5 mg/m2 were infused over 1 h, and dosages of 42, 50, and 56 mg/m2 were infused over 2 h. Pharmacokinetics was studied at all dosages. Plasma and urine samples were collected from 24 patients, and bile samples were also collected from 2 patients. 7-OMEN and metabolites were measured by high performance liquid chromatography. 7-OMEN was the major plasma fluorescent species at all times, with only trace amounts of N-demethyl menogaril observed. 7-OMEN disappeared from plasma biexponentially with t1/2 alpha 0.19 +/- 0.04 (mean +/- SE) h and t1/2 beta 13.22 +/- 1.54 h. Plasma pharmacokinetics of 7-OMEN was linear from 3.5-56 mg/m2; area under the curve increased proportionally with dosage. Total body clearance of 7-OMEN was 28.18 +/- 3.33 liter/m2/h, Vc was 224 +/- 30.8 liter/m2, and Vss was 370 +/- 25.7 liter/m2. Plasma pharmacokinetics of 7-OMEN studied on multiple days of a given course were similar. Urinary excretion of 7-OMEN and fluorescent metabolites accounted for 5.4 +/- 0.4% of the daily dose. Parent compound still represented greater than or equal to 80% of urinary drug fluorescence after 24 h. N-demethyl menogaril was the only other fluorescent drug species detected in urine. In two patients with biliary tract drains, biliary excretion of drug fluorescence accounted for 2.2-4.2% of the daily dose. Only 7-OMEN and N-demethyl menogaril were detected in bile by high performance liquid chromatography and thin layer chromatography. 7-OMEN was the major fluorescent biliary species, but, by 24 h, N-demethyl menogaril accounted for approximately 40% of biliary drug fluorescence. When considered in light of each patient's observed toxicities, excellent relationships were observed between the plasma area under the curve of 7-OMEN and the percentage of decreases in WBC and absolute neutrophil count. These latter findings should be useful in developing more precise and intelligent dosing schemes for 7-OMEN.

Thirty-three adult patients with solid tumors were treated with menogaril, a new anthracycline antibiotic. The drug was given as a two-hour infusion every 4 to 5 weeks at doses ranging from 17 to 250 mg/m2. The maximum tolerated dose was 250 mg/m2. Reversible and dose-related leukopenia was the dose-limiting toxicity. Thrombocytopenia was less frequent. Hematologic toxicity was maximal 2 weeks after treatment, and recovery usually occurred within 4 weeks. There was no dissociation between WBC and neutrophil counts, and myelosuppression did not appear to be cumulative up to 200 mg/m2. Myelosuppression was more severe for patients with heavy pretreatment and/or bone marrow involvement. Local toxicity consisting of phlebitis and/or erythema was the most common nonhematologic toxicity, especially at 250 mg/m2 (eight out of nine patients). Usually, erythema appeared within 24 hours after treatment at or near the infusion site and resolved within a few days. Occasionally, a more persistent (several weeks) orange discoloration suggesting cutaneous deposits of menogaril was observed. Nausea and vomiting were uncommon and never severe. Alopecia and mucositis were rare. Minor arrhythmias were seen in several patients during treatment, but their relationship with menogaril therapy was unclear, and in no patient did heart failure develop. Plasma concentrations were best described by a tricompartmental model with a mean terminal half-life of 29.5 hours and a mean total-body clearance of 20.2 L/h/m2. Doses of 160 and 200 mg/m2 are recommended for phase II trials in poor- and good-risk patients, respectively.

Daunomycin and adriamycin were previously found to produce Q-like banding patterns on chromosomes. The interaction of several anthracyclines with both natural and synthetic DNAs and chromosomes has been investigated in more detail. Daunomycin fluorescence is almost completely quenched by natural DNAs with varying base composition from 31 to 72% G-C and by the alternating polymer poly-d(G-C).poly-d(G-C). In contrast, daunomycin fluorescence is quenched by only 50% when the dye interacts with synthetic A-T polymers. Thus, differential quenching of daunomycin fluorescence can account for the production of bright bands at contiguous A-T sequences along the chromosome. Slight differences in fluorescence quenching between the repeating and homopolymeric A-T duplex DNAs were observed which can be attributed to differences in affinity of daunomycin for these DNAs. The aminosugar moiety of daunomycin, daunosamine, increases the binding of daunomycin to DNA and also enhances chromosome banding.--Nogalamycin, which displays no differential quenching with the different DNAs in solution, also fails to produce bands on chromosomes.--These findings suggest that non-random nucleotide sequence arrangements along the chromosome are a basic determinant for dye interaction to produce the observed banding patterns. Specific banding procedures may determine the accessibility of these sites within the chromosomal DNA.

The molecular aspects of drug-DNA interactions are presented, with special reference to anticancer drugs. The current status of, and results from, X-ray crystallographic studies on drug-oligonucleotide complexes are reviewed. The conformational features of these complexes are given in relation to the geometry of the drug binding site. Computerized molecular modelling for the rational analysis and design of DNA-binding drugs is discussed, taking the X-ray information as a starting point. Recent results from the author's laboratory on anthraquinones and anthracyclines are presented.

Spinach NADPH:ferredoxin oxidoreductase (EC 1.6.7.1) catalyzes the NADPH-dependent reduction of the anthracyclines daunomycin, aclacinomycin A, and nogalamycin and their respective 7-deoxyanthracyclinones. Under anaerobic conditions, the endogenous rate of O2 reduction by NADPH catalyzed by ferredoxin reductase (0.12 s-1 at pH 7.4) is augmented by the anthracyclines and 7-deoxyanthracyclinones. The catalytic constants are approximately equivalent for this augmentation for all substrates (approximate V of 2 s-1 and KM of 75 microM). Both O2- and H2O2 are made. Under anaerobic conditions, anthracycline reduction catalyzed by ferredoxin reductase results in the elimination of the C-7 substituent to provide a quinone methide intermediate. Following tautomerization by C-7 protonation, 7-deoxyanthracyclinones are obtained. Under appropriate conditions these may be further reduced to the 7-deoxyanthracyclinone hydroquinones. For daunomycin, the quinone methide is formed rapidly after reduction and is easily monitored at 600 nm. It may react with electrophiles other than H+, as demonstrated by its competitive trapping by p-carboxybenzaldehyde. It may also react with nucleophiles, as demonstrated by its competitive trapping by N-acetylcysteine. For aclacinomycin, quinone methide formation is also rapid although no distinct transient near 600 nm occurs. In addition to protonation, it reacts with itself providing the 7,7'-dimer. With ethyl xanthate as a thiolate nucleophile, adducts derived from addition to C-7 are obtained. For nogalamycin, quinone methide formation is not rapid. Nogalamycin is reduced to its hydroquinone, which slowly converts in a first-order process [k = (1.2 +/- 0.2) X 10(-3) s-1, pH 8.0, 30 degrees C] to the quinone methide, which is then quenched by protonation. Spinach ferredoxin in its reduced form is chemically competent for anthracycline reduction. Its effect on both the aerobic and anaerobic reactions catalyzed by ferredoxin reductase is to increase severalfold the overall velocity for anthracycline reduction. In conclusion, the aerobic reaction pathways for the anthracyclines as mediated by ferredoxin reductase are remarkably similar, while the anaerobic reactions are remarkably different. If these anthracyclines exert their antitumor activity by a common anaerobic pathway, it is most likely that the pathway is determined by the properties of the anthracycline as complexed to its in vivo target. The behavior of ferredoxin further suggests that not only low-potential flavin centers but also iron-sulfur centers should be regarded as important loci for anthracycline reductive activation.

The three-dimensional molecular structures of the complexes between an interesting antitumor drug, nogalamycin, and two DNA hexamers, d[CGT(pS)ACG] and d[m5CGT(pS)Am5CG], were determined at high resolution by X-ray diffraction analyses. Two nogalamycins bind to the DNA double helix in a 2:1 ratio with the aglycon chromophore intercalated between the CpG steps at both ends of the helix. The nogalose and aminoglucose sugars lie in the minor and major grooves, respectively, of the distorted B-DNA double helix. The binding of nogalamycin to DNA requires that the base pairs in DNA open up transiently to allow the bulky sugars to go through. Specific hydrogen bonds are found in the complex between the drug and guanine bases. We suggest that nogalamycin may prefer GC sequences embedded in a stretch of AT sequences.

We have investigated the metabolism and disposition, in rabbits, of menogaril (7-OMEN), a new anthracycline antibiotic recently introduced into clinical trials. 7-OMEN was administered by rapid i.v. injection at a dosage of 2.5 mg/kg. 7-OMEN and metabolites were assayed by high performance liquid chromatography. Plasma concentrations of 7-OMEN declined in biexponential fashion with a terminal half-life of 2.7 h. The area under the plasma concentration versus time curve was 1.3 microM X h. The systemic clearance of 7-OMEN was 57.6 ml/min/kg. No metabolite of 7-OMEN was detected in plasma. At 8 h after treatment, the cumulative urinary and biliary excretions of 7-OMEN equivalents amounted to 1.3 and 3.4% of the total administered dose, respectively. 7-OMEN was the predominant fluorescent compound in urine, but four metabolites were also seen. In bile, 7-OMEN represented only 9.6% of the cumulative excretion and six metabolites were observed. Among the organs, lungs contained the highest concentrations of parent drug. Substantial concentrations of metabolites were observed in the kidneys, liver, duodenum, and small intestine. Three of the observed metabolites of 7-OMEN have been tentatively identified as N-demethylmenogaril, 7-deoxynogarol, and N-demethyl-7-deoxynogarol.

We have investigated the metabolism and disposition, in mice, of 7-con-O-methylnogarol ( menogarol ; 7-OMEN), a new anthracycline antibiotic entering clinical trials. 7-OMEN, dissolved in 0.01 M glucuronic acid, was administered iv to mice (10 mg/kg). At specified times after injection, groups of mice were killed and 7-OMEN and metabolites were assayed in plasma and organs by HPLC. Plasma concentrations of 7-OMEN declined in triexponential fashion. The terminal t1/2 was 10.6 hr; the AUC was 10.13 microM X hr; the apparent Vc was 0.4 liter/m2, and the systemic clearance was 91.2 ml/min/m2. One metabolite, with the same HPLC characteristics as N- demethylmenogarol , was seen in plasma during the first 30 min after injection. 7-OMEN was distributed extensively to all tissues except brain. Initially, pulmonary concentrations of 7-OMEN were 15 times higher than those in any other organ and 30 times higher than those in plasma. Concentrations of 7-OMEN were the most persistent in spleen, kidney, and pancreas, and the least persistent in heart and liver. The AUC for 7-OMEN in organs was the greatest in lungs (605 nmol/g X hr), spleen (522 nmol/g X hr), and pancreas (430 nmol/g X hr), and least in heart (33 nmol/g X hr) and liver (60 nmol/g X hr). Kidneys and skeletal muscles had intermediate AUC values. In liver, two metabolites, one of which had the HPLC characteristics of N- demethylmenogarol , were seen. In other organs, the same metabolites were seen later and in small quantities.

Menogaril is an antitumor agent of the anthracycline type which is less cardiotoxic than doxorubicin in a chronic rabbit model and is active in experimental tumor systems when given by p.o. or parenteral routes. It is currently undergoing i.v. and p.o. Phase II clinical evaluation. We report here the results of pharmacokinetic and systemic bioavailability studies of menogaril in three species (mouse, dog, and monkey). Upon i.v. administration, menogaril plasma concentration-time curves declined in a biexponential (dog) or triexponential (mouse and monkey) manner, with the terminal disposition half-life (t1/2) being considerably shorter in the dog (2.86 +/- 0.47 h) than in the mouse and monkey (21.6 and 19.0 +/- 3.7 h, respectively). The systemic clearance (CL, in liters/h/kg) was highest in mouse (6.2), followed by dog (2.9) and then monkey (1.4). The drug was extensively distributed in all three species, with steady state volumes of distribution being 88.5, 9.8, and 27.9 liters/kg in the mouse, dog, and monkey, respectively. One, two, and three metabolites were detected in the plasma of mice, monkeys, and dogs, respectively, using reverse phase high performance liquid chromatography. The major fluorescent metabolite in all species coeluted with authentic N-demethyl-menogaril; the other two metabolites were present at low concentrations relative to unchanged menogaril and its putative N-demethylated metabolite. One of these metabolites, which was found in both the dog and monkey, eluted with authentic (7R)-nogarol. Mean maximum plasma concentrations of the putative N-demethylmenogaril metabolite were approximately one-tenth those of menogaril in all three species following i.v. drug administration. Upon p.o. treatment, first-pass metabolism or incomplete absorption reduced the systemic bioavailability to 12% in the dog and 33% in the mouse and monkey. N-Demethylmenogaril was the major fluorescent metabolite observed in the plasma of p.o. treated animals. Interspecies comparison of menogaril pharmacokinetic parameters in mice, dogs, monkeys, and humans using allometric techniques indicated that the parameters for mice, monkeys, and humans were highly correlated; in each of these species presystemic metabolism of p.o. administered menogaril reduced its systemic bioavailability to an equivalent extent (30-35%). To determine if metabolically formed N-demethylmenogaril might contribute to the overall antitumor activity of menogaril, we determined the effect of synthetic N-demethylmenogaril on the life span of mice bearing P388 leukemia. Results indicated that the metabolite is marginally active compared to menogaril itself.

Menogaril (7-con-O-methylnogarol) is a semisynthetic anthracycline analogue of nogalamycin that has shown good activity against a variety of experimental tumor systems as well as decreased cardiac toxicity when compared with doxorubicin in preclinical studies. Forty-one patients with refractory solid tumors received menogaril during a phase I trial at The Johns Hopkins Oncology Center (Baltimore). Menogaril was administered as an intravenous (IV) infusion on days 1 and 8 of a 28-day cycle in doses of 8 to 140 mg/m2. Eastern Cooperative Oncology Group (ECOG) grade 3 and 4 leukopenia was the principle dose-limiting toxicity and was occasionally accompanied by thrombocytopenia. Both WBC and platelet nadirs occurred between days 15 and 22. Anemia requiring transfusion was occasionally seen. Nonhematologic toxicities observed included frequent anorexia and malaise that was not dose related and postinfusion phlebitis that was dose related and occasionally dose limiting. Gastrointestinal toxicity and alopecia were infrequent and mild in severity. Three patients with cumulative doses of menogaril greater than 1,400 mg/m2 had no significant changes in ejection fractions as determined by serial gated blood pool scans. Two patients had greater than 10% decrements in ejection fractions without clinical changes at total doses of 128 and 288 mg/m2. One patient with prior anthracycline therapy and chest irradiation decreased her left ventricular ejection fraction from 52% to 30% and developed respiratory failure after two cycles of therapy in the setting of disease progression. No responses to menogaril therapy were observed. The recommended phase II dose for menogaril on this day 1 and 8 schedule is 140 mg/m2. A starting dose of 90 mg/m2 should be considered for heavily pretreated patients. In comparing results of this phase I schedule with those of other schedules, evidence for schedule-dependent toxicity differences should be sought.

Anthracycline antibiotics remain among the most potent anticancer drugs, but their efficacy is limited by the development of a dose-dependent irreversible cardiomyopathy and by the emergence of clones of tumor cells resistant to the effects of the drug. Modifications of the basic anthracycline structure have resulted in molecules that may share the activity of the parent compound, with amelioration of some toxicities, absence of cross-resistance, or activity against tumors insensitive to the parent drug. Epirubicin has a unique metabolic pathway, glucuronidation, that may result in more rapid plasma clearance and reduced toxicity as compared with doxorubicin. Epirubicin has demonstrated comparable activity to doxorubicin in breast cancer, with possibly reduced toxicity. Idarubicin is of interest because of its cytotoxic activity when given orally. Idarubicin has prolonged retention in the plasma and has equal cytotoxic activity to the parent compound. Idarubicin has demonstrated activity against acute leukemia and breast cancer; in the latter tumor category, some doxorubicin-resistant tumors have responded. Esorubicin is of interest because of its nearly absent cardiac toxicity. This agent has some activity against solid tumors and is currently being clinically tested. Aclacinomycin A is an anthracycline in which a trisaccharide is substituted for the aminosugar. Aclacinomycin A and the related compound marcellomycin are of interest as both cytotoxic and differentiating agents. Menogaril is an anthracycline with the aminosugar on the D ring; it does not exhibit cross-resistance with doxorubicin or cardiotoxicity. Mitoxantrone is a compound that is related to the anthracyclines but has a different mechanism of action. This agent has significant activity against acute leukemia and breast cancer and is currently being compared with doxorubicin. Amsacrine is another compound related to the anthracyclines that possesses major activity against acute leukemias. Minor modifications of the anthracycline molecule have had major impact on the biologic activity of these drugs. New anthracycline analogues with up to 100 times the potency of currently available anthracyclines are being developed for clinical testing, and these complex molecules retain a nearly unlimited potential for structural modification.

Number of available nogalamycin binding sites in Sarcoma-180 chromatin is less than that present in Sarcoma-180 DNA. Gradual removal of proteins from chromatin by salt leads to increase in available drug binding sites, without appreciable alteration in binding affinity. Histones restrict the accessibility of nogalamycin to chromosomal DNA, whereas high mobility group (HMG) proteins have no effect. Association of histone H1 with chromosomal DNA has a more marked inhibitory effect on nogalamycin binding than other types of histones. Chromosomal protein induced conformational change in DNA appears to be the main factor in determining the availability of strong binding sites.

Menogaril (7-R-O-methylnogarol) is an anthracycline which has significant antitumor activity in vivo and is in Phase II clinical trial. We report here the drug effect on growth and cell cycle progression of L1210 mouse leukemia cells in vitro and in vivo. At doses which inhibited the growth of L1210 cells in vitro, menogaril slowed the progression of cells through S phase and blocked cells in G2 + M. 7-R-O-Methyl-N-demethylnogarol, the major metabolite of menogaril had the same effects on cell progression in vitro. Menogaril effect on cell progression in vivo was studied with peritoneal L1210 ascites growing in CD2F1 mice. Early in infection, i.e., 3 days after inoculation of 10(5) L1210 cells, DNA histograms of cells from control and drug-treated mice showed only a G1 peak. This presumably represented host diploid G0-G1 cells which predominated in the peritoneal cavity and masked the histogram of L1210 cells. Later in infection, when about 10(8) or more cells were present in the ascites, L1210 cells predominated and DNA histograms were representative of L1210 cells. When menogaril was injected at this time, the cell cycle effects were similar to those seen in vitro. Therefore, the L1210 in vivo model can be used to study cell progression effects only late in infection (when L1210 cells predominate), and due consideration should be given to contamination of the L1210 cells with host G0-G1 cells.

Human chromosome preparations were treated with a group of anthracycline antibiotics. Well-defined, orange-red fluorescent bands were observed on chromosomes after the slide was stained with daunomycin and adriamycin but not with nogalamycin. The characteristic differential bands appeared to be similar to the banding patterns obtained by the quinacrine techniques. Interaction of these antibiotics with DNA could provide information on the general mechanism of fluorescent banding. Further, these bands (D-bands) appeared to be more stable than the Q-bands and may have some usefulness for routine clinical cytogenetic analysis.