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A 12.6-kb DNA fragment from Streptomyces glaucescens GLA.0 containing the 12 genes for tetracenomycin (TCM) C biosynthesis and resistance enabled Streptomyces lividans to produce TCM C. Transcriptional analysis of the tcmPG intergenic region in this cluster established the presence of two divergent promoters. The tcmIc mutation, a T-to-G transversion in the -10 region of the tcmG promoter, decreased promoter activity drastically at the stationary growth stage and time of maximum TCM C accumulation. This promoter may direct the transcription of a tcmGHIJKLMNO operon, while the other promoter is for tcmP.

The nucleotide sequence of the tcmIII, tcmIc, and tcmVII region of the tetracenomycin (TCM) C gene cluster of Streptomyces glaucescens ETH 22794 (GLA.0) revealed the presence of two genes, tcmP and tcmG. The deduced product of tcmG resembles flavoprotein hydroxylases found in several other bacteria, whereas the predicted amino acid sequence of tcmP is not significantly similar to those of any known proteins in the available data bases. Southern blot hybridization revealed an approximately 180-bp deletion in a tcmIII (tcmG) mutant and a 1,800-bp insertion in a tcmVII (tcmP) mutant. Heterologous expression of tcmG and tcmP in Streptomyces lividans and tcmP in Escherichia coli established that tcmP encodes an O-methyltransferase, catalyzing the methylation of the C-9 carboxy group of TCM E to yield TCM A2, and that tcmG is responsible for the hydroxylation of TCM A2 at positions C-4, C-4a, and C-12a to give TCM C. These are the final two steps of TCM C biosynthesis.

A clear role for quinone reduction in the mechanism of action of doxorubicin has still to be established. There are three possible outcomes of this form of doxorubicin metabolism: (1) drug free radical formation, redox cycling and generation of reactive oxygen species (ROS) resulting in lipid peroxidation and DNA damage; (2) covalent binding of reactive drug intermediates to DNA; and (3) formation of an inactive 7-deoxyaglycone metabolite. In this work, the occurrence of each of these pathways has been studied in vivo in a subcutaneously growing rat mammary carcinoma (Sp 107). Doxorubicin was administered by direct intratumoural injection either as the free drug or incorporated in albumin microspheres (10-40 microns diameter). There was no evidence of an increase in lipid peroxidation over background after either treatment at any time point studied. In fact, doxorubicin administration resulted in a statistically significant reduction in lipid peroxidation at the later time points studied compared to control (no drug treatment), e.g. 24 hr: control, 21.7 +/- 2.8 SD nmol malondialdehyde/g tissue; free doxorubicin (70 micrograms drug), 14.5 +/- 4.0 SD nmol/g (P < 0.01 Student's t-test) and doxorubicin microspheres (70 micrograms drug), 17.4 +/- 1.1 nmol/g (P < 0.05). Covalent binding to DNA was measured by a 32P-post-labelling technique. Low levels of four putative drug-DNA adducts were detected; however, there were no qualitative or quantitative differences in profiles between free drug and microspheres. High 7-deoxyaglycone metabolite concentrations comparable to the parent drug itself were detected after administration of microspheres (3.0 micrograms/g +/- 1.7 SD at 24 hr and 3.1 micrograms/g +/- 1.1 SD at 48 hr). In contrast, these metabolites were present at levels close to the limit of detection of our HPLC assay after free drug (0.04 microgram/g +/- 0.03 SD at 24 hr and 0.02 microgram/g +/- 0.03 SD at 48 hr). Thus, 7-deoxyaglycone metabolite formation can occur in tumour tissue (indicating active drug quinone reduction) without concomitant increases in the level of lipid peroxidation or the levels of drug-DNA adducts. In conclusion, the main biological consequence of doxorubicin quinone reduction in vivo in tumour tissue would appear to be drug inactivation to a 7-deoxyaglycone metabolite rather than drug activation to DNA reactive species or ROS.

We have reported previously that enzymes present in the Sp 107 rat mammary carcinoma catalyse doxorubicin quinone reduction (QR) to 7-deoxyaglycone metabolites in vivo [Willmott and Cummings, Biochem Pharmacol 36: 521-526, 1987]. In order to provide insights into the role of QR in the antitumour mechanism of action of doxorubicin, we have attempted in this work to identify the enzyme(s) responsible. NAD(P)H: (quinone acceptor) oxidoreductase (DT-diaphorase) was the major quinone reductase in the tumour accounting for approximately 70% of all the activity measured in microsomes and cytosols (microsomal activity, 28.4 +/- 4.6 nmol/min/mg; cytosolic activity, 94.3 +/- 11.9 nmol/min/mg). Its presence was confirmed by western blot analysis. Low levels of NADH cytochrome b5 reductase (15.6 +/- 6.3 nmol/min/mg) and NADPH cytochrome P450 reductase (14.5 +/- 4.0 nmol/min/mg) were detectable in microsomes. The presence of the latter was confirmed by western blot analysis. Pretreatment of tumours with doxorubicin (48 hr) at a therapeutic dose decreased the level of activity of all the reductases studied by at least 2-fold (P < 0.01, Student's t-test). Doxorubicin was shown not to be a substrate for purified rat Walker 256 tumour DT-diaphorase with either NADH or NADPH as co-factor and utilizing up to 20,000 units of enzyme/incubation but was confirmed to be a substrate for purified rat liver cytochrome P450 reductase. 7-Deoxyaglycone metabolite formation by purified cytochrome P450 reductase had an absolute requirement for NADPH as co-factor, was inhibited by molecular oxygen and dicoumarol (IC50 approx. 50 microM), and modulated by specific reductase antiserum. Reductive deglycoslation of doxorubicin to 7-deoxyaglycones was localized to the microsomal fraction of the Sp 107 tumour, with negligible activity being found in cytosols (NADH, NADPH and hypoxanthine as co-factors) and mitochondria (NADH and NADPH). The tumour microsomal enzyme had an absolute co-factor requirement for NADPH, was inhibited by oxygen and dicoumarol, and modulated by cytochrome P450 reductase antiserum. These data indicate strongly that NADPH cytochrome P450 reductase is the principal enzyme responsible for catalysing doxorubicin QR in the Sp 107 tumour.

A limited biosynthetic conversion of some known anthracyclinones using a specific daunorubicin-nonproducing mutant provided four new anthracycline antibiotics: 1-Hydroxy-10-methoxycarbonyl-13-deoxocarminomycin; 1-hydroxy-13-deoxocarminomycin; 1-hydroxyoxaunomycin and 6-deoxyoxaunomycin. Their isolation and purification from bioconversion broth, structural determination and antitumor activities against leukemic L1210 cells are described.

Aklavinone is an aglycone of aclacinomycin A which is an important antitumor drug. Genes for the biosynthesis of aklavinone were cloned from Streptomyces galilaeus 3AR-33, an aklavinone-producing mutant, by use of the actI and actIII polyketide synthase gene probes. Restriction mapping and Southern analysis of the DNA cloned in a lambda phage vector established that the DNA represented three different regions of the S. galilaeus 3AR-33 genome that contained 3.4, 2.5, and 4.1 kb BamHI fragments which hybridized with actIII. Of those, only the 3.4 kb fragment also hybridized with actI. Complementation experiments with specifically blocked mutants confirmed that the cloned 3.4 kb BamHI fragment contains the genes required for the early stage of polyketide synthesis in aklavinone biosynthesis.

Sequence analysis of the tcmA tetracenomycin C resistance gene from Streptomyces glaucescens GLA.O (ETH 22794) identifies one large open reading frame whose deduced product has sequence similarity to the mmr methylenomycin resistance gene from Streptomyces coelicolor, the Streptomyces rimosus tet347 (otrB) tetracycline resistance gene, and the atr1 aminotriazole resistance gene from Saccharomyces cerevisiae. These genes are thought to encode proteins that act as metabolite export pumps powered by transmembrane electrochemical gradients. A divergently transcribed gene, tcmR, is located in the region upstream of tcmA. The deduced product of tcmR resembles the repressor proteins encoded by tetR regulatory genes from Escherichia coli and the actII-orf1 gene from S. coelicolor. Transcriptional analysis of tcmA and tcmR indicates that these genes have back-to-back and overlapping promoter regions.

Preliminary evidence has been presented by Guilfoile and Hutchinson (J. Bacteriol. 174:3651-3658, 1992) suggesting that the Streptomyces glaucescens TcmR protein is a transcriptional repressor. Here, we extend that work by showing that transcription of the S. glaucescens tcmA gene is inducible by tetracenomycin C and that inactivation of the tcmR gene results in constitutive transcription of the tcmA gene. Gel retardation studies show that the TcmR protein binds to the tcmA-tcmR intergenic region in vitro and that this binding is inhibited by tetracenomycin C. Footprinting experiments demonstrate that the TcmR protein binds to an operator region that encompasses both the tcmA and the tcmR promoters. This genetic and biochemical evidence strongly supports the model of the TcmR protein acting as a repressor in inhibiting transcription of both the tcmA and the tcmR genes, in much the same way that TetR from Tn10 inhibits transcription of tetA and tetR.

The acyl carrier protein (ACP) of the tetracenomycin C polyketide synthase, encoded by the tcmM gene, has been expressed in both Streptomyces glaucescens and Escherichia coli and purified to homogeneity. Expression of the tcmM gene in E. coli results mainly in the TcmM apo-ACP, whereas expression in S. glaucescens yields solely the holo-ACP. The purified holo-TcmM is active in a malonyl coenzyme A:ACP transacylase assay and is labeled by radioactive beta-alanine, confirming that it carries a 4'-phosphopantetheine prosthetic group.

Mutations in the tcmII-tcmIV region of the Streptomyces glaucescens chromosome block the C-3 and C-8 O-methylations of the polyketide antibiotic tetracenomycin C (Tcm C). The nucleotide sequence of this region reveals the presence of two genes, tcmN and tcmO, whose deduced protein products display similarity to the hydroxyindole O-methyl transferase of the bovine pineal gland, an enzyme that catalyzes a phenolic O-methylation analogous to those required for the biosynthesis of Tcm C. The deduced product of the tcmN gene also has an N-terminal domain that shows similarity to the putative ActVII and WhiE ORFVI proteins of Streptomyces coelicolor. The tcmN N-terminal domain can be separated from the remainder of the tcmN gene product, and when coupled on a plasmid with the Tcm C polyketide synthase genes (tcmKLM), this domain enables high-level production of an early, partially cyclized intermediate of Tcm C in a Tcm C- null mutant or in a heterologous host (Streptomyces lividans). By analogy to fatty acid biosynthesis, the tcmKLM polyketide synthase gene products are probably sufficient to produce the linear decaketide precursor of Tcm C; thus, the tcmN N-terminal domain is most likely responsible for one or more of the early cyclizations and, perhaps, the attendant dehydrations that lead to the partially cyclized intermediate. The tcmN gene therefore appears to encode a multifunctional cyclase-dehydratase-3-O-methyl transferase. The tcmO gene encodes the 8-O-methyl transferase.

Two DNA fragments, ric1 and ric2, were isolated from the Streptomyces peucetius 7600 mutant, which produces daunorubicin and doxorubicin, on the basis of their abilities to confer doxorubicin and daunorubicin resistance to Streptomyces lividans. These two fragments are unrelated by restriction mapping and do not show any homology by Southern analysis, yet both of them increase the level of resistance 10-fold in transformed S. lividans. Functional analysis revealed that ric1 also contains two genes of daunorubicin biosynthesis: one coding for the aklavinone C-11 hydroxylase and the other corresponding to the putative dnrR2 regulatory gene of wild-type S. peucetius ATCC 29050 (K. J. Stutzman-Engwall, S. L. Otten, and C. R. Hutchinson, J. Bacteriol. 174:144-154, 1992). Northern (RNA) blot experiments, performed with a ric1 fragment containing daunorubicin-doxorubicin resistance gene(s), revealed a transcript of about 2,100 nucleotides that is present only during the phase of anthracycline metabolite production. The amount of this transcript is higher in strain 7600 than in strain 7900, a mutant which produces 5-fold more daunorubicin and 10-fold less doxorubicin than 7600. Furthermore, two 7900-derived blocked mutants, 8600 and 9700, do not express the 2,100-nucleotide transcript in spite of the absence of gross rearrangements in the ric1 region such as occur with the 7900 parental strain.

Daunorubicin is a highly potent trypanocide in-vitro but is inactive in-vivo. When daunorubicin is conjugated to bovine serum albumin or horse spleen ferritin using Schiffs base linkages, the complex is trypanocidal in-vitro and in-vivo. We have developed novel analytical methods, using HPLC with fluorimetric detection, for the quantitation of daunorubicin and doxorubicin in biological samples, either as unconjugated drug, or when covalently linked to macromolecules or particles. Ferritin-daunorubicin conjugate (25 mg kg-1) was administered intraperitoneally to mice infected with monomorphic Trypanosoma brucei rhodesiense; peak plasma levels occurred after 1.5 h, and were 5 times higher than those resulting from administration of an equivalent amount of unconjugated daunorubicin. Plasma levels then declined rapidly (t1/2 for 1-6 h period was 0.58 and 0.86 h respectively for conjugated and unconjugated daunorubicin). However, higher plasma levels were seen 24 h after treatment, suggesting the distribution profile of daunorubicin when conjugated to ferritin is multiphasic with resultant high levels of daunorubicin obtained for a prolonged time period.

Three proteins, including the beta-keto acyl synthase and the acyl carrier protein, involved in the synthesis of the polyketide antibiotic tetracenomycin C by Streptomyces glaucescens GLA.0 were produced in Escherichia coli by using the T7 RNA polymerase-dependent pT7-7 expression vector. Changing the N-terminal codon usage of two of the genes greatly increased the level of protein produced without affecting mRNA levels, suggesting improvements in translational efficiency. Western immunoblot analysis of cytoplasmic and membrane fractions of S. glaucescens with antibodies raised to synthetic oligopeptides corresponding to the two presumed components of the beta-keto acyl synthase indicated that both proteins were membrane bound; one appears to be proteolytically cleaved before or during association with the membrane. The beta-keto acyl synthase could be detected in stationary-phase cultures but not in rapidly growing cultures, correlating with the time of appearance of tetracenomycin C in the medium.

Adriamycin (AdM) and related anthracyclines are potent antineoplastic agents, the clinical utility of which is limited by severe cardiotoxicity. Aglycone derivatives of AdM have recently been reported to trigger the release of Ca2+ from isolated, preloaded rat heart mitochondria and to modify mitochondrial sulfhydryl (-SH) groups. Both mitochondrial Ca2+ retention and -SH status are sensitive to mitochondrial NAD(P)+/NAD(P)H ratios. This investigation examined the effects of AdM and its aglycone derivatives on the pyridine nucleotide redox status of isolated, intact heart mitochondria with the following results. (i) AdM aglycones induced the slow, Ca2(+)-independent oxidation of mitochondrial NAD(P)H. Oxidation was proportional to aglycone concentration between 5 and 60 microM. (ii) In terms of potency, 7-deoxy AdM aglycone greater than or equal to 7-hydroxy AdM aglycone much greater than AdM. (iii) Inhibitor data suggested that NAD(P)H oxidation reflects the rotenone-insensitive reduction of AdM aglycone and subsequent electron transfer to O2 generating superoxide. (iv) NAD(P)H oxidation mediated by AdM aglycone could be distinguished from the Ca2(+)-dependent NAD(P)H oxidation associated with mitochondrial Ca2+ release. This communication is the first to describe redox interactions of AdM with intact mitochondria.

An anthracycline-resistant subline of HL-60 promyelocytic leukemia cells (HL-60/AR) has been isolated in vitro by subculturing in progressively higher concentrations of Adriamycin. The resistant cells are capable of sustaining continuous growth in 10(-6) M Adriamycin which is more than 50 times the 50% inhibitory dose for the parent line. HL-60/AR expressed variable degrees of cross-resistance to daunorubicin, dihydroxyanthracenedione, vincristine, vinblastine, and actinomycin D, but it remained sensitive to methotrexate and 1-beta-D-arabinofuranosylcytosine. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of glycoproteins of HL-60/AR revealed two prominent glycoproteins with molecular weights of 160,000 +/- 10,000 and 110,000 +/- 10,000 which were not detected in the sensitive cells. Cellular uptake and retention of daunorubicin was studied in the resistant and sensitive cells utilizing digitized video fluorescence microscopy. The sensitive cells accumulated more drug and showed at least 2-fold greater levels of brightness than the resistant cells. Studies of total intracellular accumulation, utilizing 10(-6) M [14C]-daunorubicin as a marker, showed a 1-h accumulation of 98 +/- 20 pmol/10(6) cells in HL-60/AR versus 255 +/- 25 pmol/10(6) cells in HL-60. Exposure to nontoxic concentrations of the calcium channel blocker Verapamil (10(-5) M) led to enhanced accumulation (175 +/- 8 pmol/10(6) cells) and retention of the drug in HL-60/AR, resulting in increased cytotoxicity in HL-60/AR. These anthracycline-resistant leukemic cells may serve as a valuable experimental model in studying the phenomenon of multiple drug resistance as well as strategies to circumvent it in human myeloid leukemia.

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.

The metabolism and tissue distribution of aclacinomycin A (ACL), marcellomycin (MCM), and musettamycin (MST), three new anthracycline antibiotics, were compared after IV administration to mice. In plasma, total MCM- and ACL-derived fluorescence declined according to first-order kinetics, whereas an initial decline followed by a rebound was observed for MST. In plasma, MCM remained the predominant compound. ACL was eliminated more quickly, and was replaced by two metabolites, the reduced glycoside M1, and an aglycone. In the case of MST, two unidentified metabolites were observed in concentrations equivalent to that of the parent drug. The three drugs were distributed widely to organs, but only ACL achieved measurable concentrations in the brain. Initially, high concentrations of all three drugs were present in the lungs, but these decreased quickly to values similar to those present in the liver and kidneys. Intermediate concentrations of the three drugs were measured in heart and skeletal muscle. Splenic concentrations of all three drugs rose progressively, reaching a maximum at 8 h after injection in the case of ACL and MST, and at 24 h after injection in the case of MCM. Concentrations of the metabolites of MCM and MST were low in all organs except liver and kidney, where the aglycones 7-deoxypyrromycinone and bisanhydropyrromycinone were seen. The metabolism of ACL was extensive. Aglycones were dominant in the liver and kidneys, whereas reduced glycosides predominated in the spleen. These observations indicate that the murine pharmacology of these three structurally similar drugs differs markedly.

Rat liver cytosol and buttermilk xanthine oxidase both converted 7-deoxypyrromycinone, the 7-deoxyaglycone of marcellomycin, a new anthracycline antibiotic, to a nonfluorescent compound under anaerobic conditions and in the presence of an electron donor. Reduced nicotinamide adenine dinucleotide and reduced nicotinamide adenine dinucleotide phosphate were equally effective electron donors for liver cytosol, and xanthine was the best cofactor for xanthine oxidase. However, xanthine was inactive with liver cytosol. Reactions with xanthine oxidase obeyed Menten-Michaelis kinetics and were inhibited by allopurinol. No xanthine oxidase activity was detected in liver cytosol. Xanthine oxidase also induced a loss of fluorescence when incubated with 7-deoxydaunorubicin aglycone. The nonfluorescent metabolite of 7-deoxypyrromycinone was tentatively identified as the dihydroquinonic derivative of the parent deoxyaglycone on the basis of its spectrophotometric, fluorescent, thin layer chromatographic, and mass spectral characteristics. Our data demonstrate that more than one enzymatic activity, xanthine oxidase, and an unidentified rat liver cytosolic enzyme convert the 7-deoxyaglycones of anthracycline antibiotics to nonfluorescent metabolites.

Levels of radioactivity and total anthracycline fluorescence in tissues of A/JAX mice were compared 1 h after IV administration of unlabeled or [14C]-labeled AD 32 (50 mg/kg). Highest levels of both fluorescence and radioactivity were found in the small intestine (including contents) and liver, a result consistent with the known hepatobiliary excretion of AD 32 and metabolites. Significant accumulations of radioactivity and fluorescence were found in kidney, spleen, large intestine (including contents), lung, and heart. Lesser levels were found in muscle and fat. Little radioactivity and fluorescence were found in brain. Liquid chromatographic analysis of extracts of small intestine and liver homogenates showed N-trifluoroacetyladriamycin (AD 41) as the major fluorescent species, and also revealed N-trifluoroacetyladriamycinol (AD 92) and occasional low levels of AD 32. In addition, there was a major peak of nonfluorescent radioactive material and two fluorescent nonradioactive signals (unknowns 1 and 2), indicative of cleavage of the radiolabel from the chromophore.

Fluorescence anisotropy titration was used to determine the equilibrium binding affinities of several anthracycline antitumor antibiotics for sonicated dimyristoylphosphatidylcholine (DMPC) and dipalmitoylphosphatidylcholine (DPPC) vesicles at 27.5 degrees C. Eight daunomycin analogues, all differing from the parent by one structural change in the aglycon portion of the molecule, as well as four anthracycline congeners modified in the amino sugar were studied. Double-reciprocal plots were used to determine overall binding affinities (K). It was shown that structural changes in both the aglycon and amino sugar portions of the daunomycin molecule strongly modulated K values for DMPC and DPPC bilayers. For modifications in the aglycon portion of an anthracycline, a correlation between drug hydrophobicity and membrane affinity was observed. The number of binding sites per phospholipid molecule (n) and the apparent association constant (Kapp) where K = nKapp, were determined at several temperatures for adriamycin, daunomycin, and carminomycin. The n values were found to be independent of temperature for fluid-phase DMPC or solid-phase DPPC bilayers. The Kapp values (25 degrees C) ranged from (0.82-4.4) X 10(5) M-1 for DMPC vesicles to (4.4-7.3) X 10(5) M-1 for DPPC vesicles. Although the Kapp values for the three drugs were similar for a particular bilayer, major differences were noted in the values of n and, therefore, in the overall vesicle affinities (nKapp). van't Hoff plots showed that anthracycline binding was exothermic; in all cases but one binding was accompanied by a decrease in entropy.(ABSTRACT TRUNCATED AT 250 WORDS)

The present study shows that a human malignant glioma cell line (U-251 MG) accumulates and degrades low-density lipoprotein (LDL) by a saturable, high-affinity process (Km approximately equal to 5 micrograms/ml). Accumulation and degradation could be enhanced by preincubating the cells in a lipoprotein-deficient medium. The LDL degradation rate was highest when the cells were proliferating rapidly. An aclacinomycin A:LDL complex containing 150 to 450 drug molecules per LDL particle could be obtained by incubating LDL with a large excess of aclacinomycin A at 40 degrees. When the glioma cells were incubated with the aclacinomycin A:LDL complex, cellular drug accumulation was dependent on the LDL receptor activity. There are four reasons for drawing this conclusion. (a) U-251 MG cells with high LDL receptor activity accumulated more drug than U-251 MG cells with low LDL receptor activity. (b) U-251 MG cells accumulated more drug than a mutant fibroblast line (GM 1915) lacking LDL receptor activity. (c) Aclacinomycin A accumulation was increased when U-251 MG cells were incubated in the presence of chloroquine, an agent that inhibits LDL degradation. (d) Aclacinomycin A accumulation was reduced when U-251 MG cells were incubated in the presence of either an excess of native LDL or heparin, which has been demonstrated to inhibit receptor-mediated binding and degradation of LDL. The aclacinomycin A:LDL complex also inhibited growth of the glioma cells. Our results suggest that the glioma cells studied have LDL receptors and that it may be possible to use LDL as a vehicle for lipophilic antineoplastic drugs in order to increase the drug accumulation in tumor cell populations with high LDL receptor activity.

Disposition kinetics of Adriamycin (ADR), adriamycinol (AOL) and their 7-deoxyaglycones (ADR-DONE and AOL-DONE) have been studied in AKR mice bearing a s.c. growing ROS tumour after i.v. administration of 10 mg/kg. ADR and its metabolites were extracted from tissues by two different methods, separated and identified by HPLC. Tissue 7-deoxyaglycones were isolated, purified and then identified by HPLC, TLC and mass spectrometry. Kinetic profiles of ADR showed rapid equilibration of the drug with well perfused tissues but a slower and complex equilibration of the drug with the ROS tumour. Serum and tissue profiles of AOL were similar to the parent drug. From the kinetic profiles of the 7-deoxyaglycones it appeared that in the tissues their formation was rapid, with ADR-DONE always appearing first. Maximum concentrations of ADR-DONE were reached in the liver and heart only 10 min after drug administration. Estimated half lives of ADR-DONE were in liver, 1.1 hr and in heart, 2.8 hr and for AOL-DONE in liver, 5.4 hr, in heart, 5.1 hr and in serum, 4.1 hr.

We studied the intracellular distribution of drugs within anthracycline-sensitive and -resistant cells by computer-assisted digitized video fluorescence microscopy. We found that the antitumor antibiotic, daunorubicin, distributes differently in anthracycline-sensitive and -resistant human leukemia cells (HL-60). Verapamil and other agents known to circumvent resistance in pleiotropic drug-resistant cell lines were able to change the pattern of distribution of daunorubicin in the anthracycline-resistant HL-60 cells back to the distribution found in anthracycline-sensitive HL-60 cells. To investigate the biochemical basis for this effect, we studied the distribution of daunorubicin and doxorubicin in a hydrophobic/hydrophilic (membrane/cytoplasmic) environment using the two-compartment cell-free system of Folch. Our results demonstrate that various unrelated drugs known to overcome resistance will also change the distribution of the anthracyclines in the hydrophobic/hydrophilic compartments. Our data allow the hypothesis that various unrelated agents known to circumvent resistance may act by altering the hydrophobic/hydrophilic solubility of anthracyclines in the resistant cell.

Human neutrophils exposed to 10(-4) M doxorubicin and the derivatives epirubicin and thepirubicin revealed a different intracellular penetration and distribution pattern as demonstrated by fluorescence microscopy and fluorimetric determination of drug intracellular concentration. While doxorubicin was found to be a potent inducer of superoxide generation from resting cells, epirubicin exhibited less superoxide-inducing power. Thepirubicin on the contrary did not show any superoxide-inducing effect. Moreover the anthracyclines tested all inhibited the phorbol ester-stimulated chemiluminescent response to the same extent, which suggested a common target for the drug action. Anthracycline-stimulated superoxide production seems to correlate with the cardiotoxic effects. The most cardiotoxic drug, doxorubicin, is the most potent inducer of superoxide generation, while epirubicin, which is less cardiotoxic, has a relatively limited effect on superoxide production. Thepirubicin which has been shown not to induce delayed cardiomyopathy has no effect on superoxide release from the cells.

Streptomyces nogalater, UC-2783, and Streptomyces peucetius var. caesius, IMRU-3920/UC-5633, catalyze ketonic carbonyl reduction of steffimycinone (1, Scheme 1). Using cell-free preparations of S. nogalater, the process of ketonic carbonyl reduction has been shown to be TPNH linked. The product, steffimycinol (2), is reduced further by Aeromonas hydrophila, 2C/UC-6303, by the process of microaerophilic conversion of anthracyclinones previously reported1,2) with the result being the formation of 7-deoxysteffimycinol (3). The products (2 and 3) were isolated by extraction from the fermentations followed by chromatographic purification. Identification was by comparison of various physical properties and spectral data with those of authentic materials obtained by chemical means. Catalytic activity of the crude enzyme preparations of S. nogalater was lost by dialysis by restored by addition of TPNH although not by addition of DPNH demonstrating TPNH dependence. The reaction rate increased linearly with added crude enzyme protein up to 4 mg/ml and was highest between pH 6.5 and 7.0.

The detection of low amounts of anthracyclines in single cells was attained with a microscope-photometer by employing an argon laser as a fluorescence excitation source. The time course of drug uptake was followed by incubating the cells under the microscope and measuring the increase of fluorescence intensity from the beginning of the drug penetration. An intracellular distribution map of the drug fluorescence was obtained by scanning measurements, through which the more specific sites of binding were visualized. This means of detection is compared with two of the most commonly employed biochemical techniques.

The intracellular metabolism of daunorubicin (DNR) has been studied in sensitive and resistant Ehrlich ascites tumor (EAT) cells. The subcellular localization of metabolites has been followed by normal-phase and reverse-phase high-pressure liquid chromatography (HPLC). The metabolism of DNR by either sensitive or resistant EAT cells is not significant; unmetabolized DNR is always the main intracellular compound. Daunorubicinol (DOL) accounts for less than 5% after 24 h and an unidentified product is also observed. This highly apolar compound, having an intrinsic fluorescence one order of magnitude greater than that of DNR is formed in acellular conditions and could be a chemical artifact. DNR and DOL are mainly associated with DNA-containing fractions. No significant differences can be observed in the metabolism of DNR in sensitive and resistant EAT cells.

Life-threatening irreversible cardiomyopathy is a major complication of anthracycline therapy, particularly in the pediatric population. The pediatric cardiologist, in concert with the primary oncologist, should therefore play a major role in the care of patients receiving these agents and in clinical trials involving their use. Many risk factors and their relationships to drug pharmacokinetics, mechanisms of action, and toxicity have been identified. These data provide a rational basis for present-day recommendations regarding anthracycline administration and dosage scheduling. They furthermore provide potential avenues for clinical investigation aimed at improving the therapeutic index of these agents: alpha-tocopherol, cytochrome Q10, and other free radical scavengers may decrease the deleterious effects of free radical generation on the myocardium without apparent interference with tumoricidal effect. The cardiac glycosides may decrease cardiac toxicity by specific myocardial exclusion. Anthracycline analogs have been designed to specifically inhibit myocardial binding and/or free radical generation. Clinical trials involving these agents are difficult to interpret because of variability in front end risk factors and dosage schedules in the study population. Furthermore, the relatively low (5 to 10%) incidence of affected patients implies the need for large numbers to demonstrate a statistically significant benefit. Pediatric protocols addressing these issues are urgently needed. Guidelines for present-day management and future studies are outlined.

In an attempt to establish a relationship between the pharmacokinetics in mouse heart of new anthracycline derivatives and their potential chronic cardiotoxicity and on this way to provide a useful and economical test for screening of new analogs, we followed the accumulation and metabolism of six anthracyclines in the mouse heart after single IV administrations of these drugs at equimolar doses. We found that the six drugs, i.e., daunorubicin (DNR), doxorubicin (DOX), rubidazone (RBZ), detorubicin (DET), N-L-leucyl-DNR (LEU-DNR) and N-L-leucyl-DOX (LEU-DOX), accumulate at various levels in the cardiac tissue and are metabolized to different extents, leading to the appearance in the heart of variable amounts of DNR or DOX. The total exposure of the mouse heart, as evaluated by calculation of the areas under the CXt curves, can be correlated qualitatively with the chronic cardiotoxicity of the six anthracyclines, as recently determined in the rabbit model. We therefore think that our study provides a simple, rapid, and inexpensive predictive test for the screening of new analogs for potential cardiotoxicity. Moreover, it offers the advantage of using the same species for determining the most favorable ratio between therapeutic activity and toxic side-effects.

Daunorubicin (daunomycin; NSC 82151) is a fermentation-derived anthracycline antibiotic that is clinically useful in the treatment of human leukemias. Daunorubicin itself is found rarely in microbial fermentations, but is present normally in the form of glycoside derivatives that yield the free drug on simple acid hydrolysis. A major by-product of daunorubicin fermentations is usually the structurally related anthracyclinone epsilon-rhodomycinone. We have used mutants of a daunorubicin-producing Streptomyces species to study the biosynthetic relationship between epsilon-rhodomycinone and daunorubicin. We found that exogenously added epsilon-rhodomycinone can be converted to daunorubicin glycosides by a nonproducing mutant and by a mutant that produces daunorubicin glycosides but not epsilon-rhoeomycinone. Molar conversion efficiences were in the 15 to 30% range. The latter mutant was also shown to convert exogenous 14C-labeled epsilon-rhodomycinone to 14C-labeled daunorubicin glycosides, again at conversion efficiencies of about 25%. The same biotransformation was observed with daunorubicin production strain C5, which normally accumulates both epsilon-rhodomycinone and daunorubicin glycosides. A significant percentage (16 to 37%) of exogenously added epsilon-[14C]rhodomycinone was metabolized by strain C5, and 22 to 32% of the metabolized radioactivity could be recovered as daunorubicin glycosides. A mathematical model of epsilon-rhodomycinone metabolism was constructed based on plausible assumptions concerning the kinetics of epsilon-rhodomycinone accumulation and catabolsim. When analyzed according to this model, our data indicate that most (63 to 73%), but not all, of the daunorubicin glycosides accumulated in the experiments with production strain C5 derived from epsilon-rhodomycinone. A pathway network for the biosynthesis of daunorubicin glycosides is proposed that is in agreement with these data. In this proposed pathway network, epsilon-rhodomycinone is an intermediate in one of at least two pathways which yield daunorubicin glycosides.

The quantitative aspects of drug disposition in man of the commonly used antineoplastic agents, including cyclophosphamide, the nitrosoureas, cisplatin, methotrexate, cytarabine, 5-fluorouracil, doxorubicin, daunorubicin, bleomycin, vincristine, vinblastine, and vindesine are reviewed. Although the pharmacokinetic behaviour of these drugs has been adequately described in man, the chemical reactivity, the complexity of metabolism and disposition, the lack of simple, rapid and sensitive assays to measure plasma concentration, and the lack of defined therapeutic and toxic plasma concentrations have limited the application of routine drug monitoring in clinical oncology. With the exception of high dose methotrexate, drug doses and administration schedules remain empirical with a standard starting dose and subsequent dosage modifications determined by ensuing drug toxicities. However, many of the pharmacological characteristics of the drugs, such as their low therapeutic index, potentially life-threatening toxicities and wide individual variability in drug disposition, necessitate pharmacological monitoring. Comprehensive pharmacokinetic analysis of new and established antineoplastic agents does play a role in defining dosage, administration schedule, route of administration, and dosage modification in the presence of organ dysfunction. Consideration of the kinetics of these drugs in planning treatment regimens could lead to more rational, safer and possibly more efficacious use.

Pharmacokinetic measurements to monitor and design cytotoxic treatments in cancer patients are being used more and more in order to optimize dosage and administration schedules. Ideally, information on drug concentrations over time should help reveal dose-response correlations. The cytotoxic drugs carmustine, etoposide, cyclophosphamide, iphosphamide, cis-diammineplatinum, Adriamycin (doxorubicin), and 4'-epi-Adriamycin have been monitored on different treatment programs of patients with advanced lung cancers. The collected experience emphasizes the many individual variables encountered in clinical practice complicating the effort of correlating pharmacokinetic data with clinical results. The examples, presented on the basis of the authors' experiences, pertain to drug instability, gastrointestinal absorption, enzymatic induction in the liver, drug interaction, and drug tissue concentrations.

Adriamycin has been detected by high-pressure liquid chromatography in ascites and pleural fluid within 30 min after intravenous injection of Adriamycin (50 mg/m2). The concentration of Adriamycin was approximately one-half of that in plasma. Significant concentrations of Adriamycin metabolites were seen in the ascites fluid of one patient 4 hr after intravenous drug injection. Individual variability in the achievable ascites and pleural concentrations of cytotoxic drugs may be important in determining the responsiveness of patients to chemotherapy and the described analytical technique should be useful in assessing the concentrations of Adriamycin and its metabolites in malignant ascites and pleural effusions.

The metabolism and disposition of marcellomycin (MCM), a new anthracycline antitumor antibiotic, were studied after iv administration to mice. In plasma, total drug fluroescence decreased according to first order kinetics and was mainly comprised of parent drug. In addition to MCM, five compounds (M2, P1, P2, G1, G2) were seen. M2 reflected the presence of a contaminant in the parent drug. P1 and P2 represented polar conjugates of MCM and M2, respectively; and G1 and G2 proved to be aglycones. P1 and G1 were observed during the first hours after injection, and G2 was more persistent and represented 35-50% of total drug fluorescence by 8 hr after injection. MCM was distributed widely to organs, except the brain. High MCM concentrations were measured in the lungs initially but they decreased quickly and, by 60 min, reached values similar to those present in the liver and kidneys. Low MCM concentrations were observed in heart and muscles. The splenic concentration of fluorescence rose progressively and, by 16 hr, was higher than that in all other organs. The concentrations of MCM metabolites were small in all tissues except in the liver, where an aglycone identified as 7-deoxypyrromycinone, was seen during the first 4 hr after injection. Our results indicate that the metabolism of MCM in the mouse is qualitatively similar to that in man, but that important quantitative differences exist. The significance of this observation as a possible explanation of the differences in observed toxicities between the two species remains to be established.

Several factors are known to modulate the clinical pharmacokinetics of adriamycin (ADR). Biotransformation has not been studied in this context because of problems identifying serum metabolites. We have studied patterns of ADR biotransformation in 25 patients with normal liver and kidney function and in most cases receiving ADR for the first time. Three major serum metabolites were identified by HPLC, TLC and mass spectrometry and their pharmacokinetics were followed over a 24-hr period. The relative amount of each metabolite present in a patient was quantitated by calculating its AUC. Adriamycinol was the major metabolite detected in the majority of patients. Adriamycin 7-deoxyaglycone was detected in the serum of 15 patients where it accounted for a small percentage of the total ADR concentration (1-5%). Its apparent half-life was normally less than 30 min. Adriamycinol 7-deoxyaglycone was detected in the serum of only 13 patients where it accounted for a greater percentage of the total ADR concentration (10-20%). Its pharmacokinetics exhibited marked inter-patient variations, with apparent half-lives ranging from 0.1 to 24 hr. There was a correlation between the AUC of ADR and the relative amount of metabolites present in each patient (r = 0.73). Thus, biotransformation may explain, partly, inter-patient variations in ADR pharmacokinetics. In turn, variations in biotransformation are dictated by whether or not ADR is converted to 7-deoxyaglycones.

Thirteen patients with metastatic brain tumors were treated by combined chemotherapy with cisplatin and aclarubicin hydrochloride. Initial response to this therapy was evaluated by the changes of tumor size on CT scan and clinical state during and after the treatment. The side effects and the causes of death were also studied. Nine cases demonstrated complete remission and 3 cases revealed partial response on CT scan. In short, over all response rate was 92%. Clinical state evaluated by Karnofsky scale was improved in 9 out of 13 cases. As the side effects, there were mild myelosuppression, nausea and vomiting, which didn't persist for a long time. The cause of death was mainly due to recurrence of primary lesion. The tissue concentration of aclarubicin hydrochloride was measured in 6 patients, of which mean value was 0.558 microgram/g at 15 min. The concentration was thought high enough to kill tumor cells.

The in vitro metabolism of the antitumor anthracycline antibiotic, aclacinomycin-A, was studied using rat liver homogenate. In the presence of NADH or NADPH, aclacinomycin-A was converted to aclacinomycin-A analogs, MA144 M1 and MA144 N1, which were stereospecifically reduced at the keto group of the C-4''' position of L-cinerulose in aclacinomycin-A. Subcellular fractionation indicated that the production of MA144 M1, which was reduced to L-amicetose, was catalyzed by NADPH-dependent soluble cinerulose reductase I, and the production of MA144 N1, which was reduced to L-rhodinose, was catalyzed by NADPH-dependent soluble cinerulose reductase II and NADH-dependent microsomal cinerulose reductase. The properties of these three enzymes were studied. Soluble cinerulose reductase I which produces MA144 M1 showed a optimum pH at 6.3, Km values of 3.3 x 10(-4) M for aclacinomycin-A and 3.2 x 10(-5) M for NADPH. Soluble cinerulose reductase II which produces MA144 N1 showed a pH optimum at 6.3 and Km values of 2.0 x 10(-3) M for aclacinomycin-A and 4.0 x 10(-5) M for NADPH. All thesse reductases were sensitive to sulfhydryl reagents and were inhibited by vitamin K3. Microsomal cinerulose reductase showed sensitivity to diconmarol and ferrous ion. The main nondegradative pathways of aclacinomycin-A were discussed from these results.

Auramycinone was subjected to microbial conversion by Streptomyces coeruleorubidus ATCC 31276, a producer of baumycins. As a result, auramycinone was converted to 11-hydroxyauramycinone and 9-methyl-10-hydroxydaunomycin (feudomycin D). The results implicate auramycinone as a presumptive intermediate in the biosynthesis of 9-methyl-10-hydroxydaunomycin by S. coeruleorubidus.

The structure of iremycin [10-(alpha-L-rhodosaminyl)-gamma-rhodomycinone] hydrochloride has been confirmed by 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. We studied the interaction of iremycin and the related compound daunomycin with DNA by transient electric dichroism and by sedimentation analysis of supercoiled closed duplex DNA. The apparent length increase of sonicated calf thymus DNA (150 +/- 20 base pairs) in 2.5 mM sodium cacodylate buffer (pH 7) at 12 degrees C was determined to be 0.40 +/- 0.02 nm/bound drug). The Cu(II) complex of iremycin with a metal/drug ratio of 0.7 induces a length increase of DNA of 0.44 +/- 0.02 nm/added drug. The alignment of the iremycin chromophore with respect to the DNA helix axis was determined from the electric dichroism of the complex. The tilt (long axis) and twist (short axis) of the chromophore are both 28 +/- 4 degrees, whereas for daunomycin the long axis is perpendicular to the helix axis and the short axis is twisted by about 25 degrees. Intercalation of iremycin between DNA base pairs is supported by unwinding of the supercoiled closed duplex form of pBR 322 plasmid DNA from Escherichia coli. In 2.5 mM sodium cacodylate buffer at pH 7 and at 25 degrees C, the unwinding induced by iremycin is 15.0 +/- 1.5 degrees/bound drug. Under identical conditions daunomycin shows on unwinding angle of 15.4 +/- 1.5 degrees. The superhelical density of pBR 322 DNA (sigma 0) was determined to be -0.087 +/- 0.002 at standard conditions (0.2 M NaCl, 37 degrees C).

One approach currently being used to target drug action selectively to specific cells and tissues is to link active drugs to proteins and peptides that are preferentially recognized by, distributed to or activated by the target cells. Inasmuch as the kidney proximal tubule cells are very active in recapturing and catabolizing peptides and proteins which appear in the glomerular filtrate, we have examined the cellular pharmacology of daunorubicin (DNR) and doxorubicin (DOX) and selected amino acid and dipeptide derivatives in suspensions of rabbit renal proximal proximal tubules. The tubules accumulated the DNR series of drugs and their metabolites to a greater extent than the DOX series. Although all of the amino acid derivatives of these drugs entered the cells for sequestration and metabolism, the dipeptide derivative, alanyl-leucyl-DNR, was not detected within the cells. Using high-performance liquid chromatography to quantify the various metabolites and isopycnic centrifugation of tubule-derived post-nuclear supernates in linear sucrose gradients to resolve various subcellular organelles, the subcellular sites of metabolism of these drugs were examined. A NADPH-dependent reduction of the C-13 carbonyl group of the parent drugs, which was the primary route of metabolism, was localized to the cytoplasm. Formation of aglycones generated by the cleavage of the daunosamine moiety from the anthracycline core followed the microsomal marker, NADPH-cytochrome reductase, in the sucrose gradients. Removal of the terminal amino acid from alanyl-leucyl-DNR was tentatively assigned to a cysteine-requiring enzyme on the plasma membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

Aclacinomycin is a member of naturally occurring anthracyclines having three sugar moieties in the molecule. It showed antitumour activity on various mouse and rat tumours. Combination therapy with AraC etc. gave remarkable clinical results on acute myeloid leukaemia. Aclacinomycin strongly inhibits RNA synthesis of the tumour cells. It has lower cardiac toxicity than adriamycin and no mutagenicity. THP-Adriamycin is a derivative of adriamycin designed from the structure of baumycins. It showed stronger effects than adriamycin in inhibiting many mouse tumours such as L1210 and P388 leukaemia, B16 melanoma and colon 38 adenocarcinoma. THP-Adriamycin is rapidly taken up by both adriamycin-sensitive and resistant leukaemic cells. Its level of cardiac toxicity is as low as that of aclacinomycin. Ditrisarubicins are new naturally occurring anthracyclines isolated from Streptomyces having six sugar moieties in the molecule. Ditrisarubicin has a potent cytostatic and antitumour activities on adriamycin resistant mouse leukaemia. Its binding constant to DNA is extremely high compared with other anthracyclines.

Aclacinomycin A was observed to effect the thermal denaturation of DNA and to increase Tm. The visible absorption spectrum of the antibiotic showed bathochromic and hypochromic shifts upon reaction with native and heat-denatured DNA. [14C]Aclacinomycin A was demonstrated by equilibrium dialysis to bind to DNA. Native calf thymus DNA appeared to possess one binding site per ca. 6 nucleotides for the antibiotic with an apparent association constant of ca. 1.2 x 10(6) M-1. Heat-denatured DNA showed much less affinity for the antibiotic: one binding site per ca. 6 nucleotides with an apparent binding constant of ca. 3.5 x 10(4) M-1. The difference of association constants between double- and single-stranded DNAs suggested that the antibiotic may be intercalated between base pairs of the DNA double helix. [14C]Aclacinomycin A exhibited higher affinity for poly(dAdT) than for poly(dIdC). The antibiotic showed a significant difference spectrum with porcine tubulin, indicating an interaction with tubulin. The binding to tubulin was also demontstrated by equilibrium dialysis of [14C]aclacinomycin A and tubulin.

An anthracycline antitumor antibiotic, aclacinomycin A, was given to mice, rabbits or dogs intravenously to study the pharmacokinetics by photometric assay based on the absorption of anthracycline ring. The drug was rapidly eliminated from the blood in these animals. Drug levels were much higher in the blood cells than in the plasma. Tissue levels in dogs were 50 approximately 100 times higher than the blood levels, which showed the drug was rapidly transferred from the blood to tissues after administration. Higher levels were observed in the lungs, spleen and lymph nodes, where the drug was present as aclacinomycin A itself and the glycoside-type metabolites that were biologically active. The active form was also detected in the pancreas, heart, thymus, bone marrow and gastrointestinal tract. In the liver and kidneys, biologically inactive aglycone-type metabolites were observed. About 2 approximately 4% of the drug given to rabbits or dogs was recovered in the urine by 72 hours after administration, in which only 10% of the excreted drug was active form in rabbits but about 65% in dogs. The rest was inactive aglycone-type metabolites that were excreted almost in the conjugated form. Biliary excretion also contributed to the total clearance of the drug. Aclacinomycin A was absorbed even by oral administration in rabbits and dogs. Tissue distribution of the drug orally given to dogs was similar to that in intravenous administration, except that higher levels of active form were detected in the gastrointestinal tract and of inactive form in the liver.