Production of a new hybrid anthracycline 4-O-methylepelmycin by heterologous expression of dnrK in epelmycin-producing Streptomyces violaceus.

A new hybrid anthracycline antibiotic was produced by heterologous expression of dnrK encoding carminomycin 4-O-metyltransferase in an epelmycin-producing Streptomyces violaceus. pMK100 was constructed by insertion of Steptomyces peucetius dnrK gene in Steptomyces-expression vector pIJ6021 and introduced to the epelmycin producer. The transformant produced a hybrid anthracycline antibiotic together with host epelmycins when cultured in antibiotic production medium in the presence of thiostrepton. The hybrid anthracycline was determined to be 7-O-L-rhodosaminyl-4-O-methyl-epsilon-rhodomycinone (4-O-methylepelmycin D). However, the attempts on production of hybrid 4-O-methylaclarubicin and 4-O-methyl-1-deoxyobelmycin by the transformants of aclarubicin and 1-deoxyobelmycin producers with pMK 100 were unsuccessful.

New betaclamycin and aclarubicin analogs obtained by prolonged microbial conversion with an aclarubicin-negative mutant.

Microbial conversion of beta-rhodomycinone and aklavinone using an aclarubicin-negative Streptomyces galilaeus mutant afforded new anthracycline antibiotics CG21-C and CG1-C which had a rednosyl-2-deoxyfucosyl-rhodosaminyl trisaccharide residue at C-7 of each added aglycone. They were produced only when a prolonged conversion culture took place. Because the usual conversion products containing a cinerulosyl-2-deoxyfucosyl-rhodosaminyl residue were at first accumulated and then decreased during further cultivation, it was evident that they occurred by the modification of terminal cinerulose. The isolation, purification, and structural determination are described, and cytotoxicity in vitro against cultured L1210 cells and the formation mechanism are discussed.

The antitumor drug aclacinomycin A, which inhibits the degradation of ubiquitinated proteins, shows selectivity for the chymotrypsin-like activity of the bovine pituitary 20 S proteasome.

The antitumor drug aclacinomycin A was previously shown to inhibit the degradation of ubiquitinated proteins in rabbit reticulocyte lysates with an IC50 of 52 microM (Isoe, T., Naito, M., Shirai, A., Hirai, R., and Tsuruo, T.(1992) Biochim. Biophys. Acta 1117, 131-135). We report here that from all the catalytic activities of the 20 S proteasome tested, the chymotrypsin-like activity was the only one affected by the antitumor drug. An important requirement for inhibition of the chymotrypsin-like activity seemed to be the presence of hydrophobic nonpolar residues in positions P1 to P3. Degradation of Z-E(OtBu)AL-pNA and Z-LLL-AMC at pH 7.5 was dramatically (87-98%) inhibited by 50 microM of the drug, while that of Z-GGL-pNA (containing uncharged polar residues in positions P2 and P3) and succinyl-LLVY-AMC (containing an uncharged polar residue in the P1 position) was inhibited only 11 and 24%, respectively. Aclacinomycin A had no effect on cathepsin B, stimulated trypsin, and inhibited chymotrypsin and, to a lesser extent, calpain. The aglycone and sugar moieties of the cytotoxic drug are essential for inhibition. The results presented here support a major role for the chymotrypsin-like activity in the degradation of ubiquitinated proteins. Aclacinomycin A is the first described non-peptidic inhibitor showing discrete selectivity for the chymotrypsin-like activity of the 20 S proteasome.

New anthracycline antibiotics 10-epi-oxaunomycin and 10-epi-11-deoxyoxaunomycin.

Two new anthracycline antibiotics, 10-epi-oxaunomycin and 10-epi-11-deoxyoxaunomycin, were photochemically obtained from anthracycline metabolites D788-1 (10-carboxy-13-deoxocarminomy-cin) and D788-3 (10-carboxy-11-deoxy-13-deoxocarminomycin) and were examined for their growth inhibitory activities on cultured L1210 leukemic cells. Effects of the S configuration of C-10 and a hydroxyl group at C-11 on the bioactivity are discussed in comparison with oxaunomycin and 11-deoxyoxaunomycin.

Difference between the resistance mechanisms of aclacinomycin- and adriamycin-resistant P388 cell lines.

Aclacinomycin (ACR) is an anthracycline anticancer drug that shows marked effects in Adriamycin (ADM)-resistant tumors. ADM, however, is not effective against ACR-resistant tumor cells. When tumor cells acquire resistance to ACR, though the resistance is not easily acquired, they show strong cross-resistance to ADM. To study the mechanism underlying these phenomena, we studied the resistance mechanism of ACR- and ADM-resistant P388 leukemia cells. The P388/ACR cells showed 4.9- and 100-fold resistance to ACR and ADM, respectively, whereas the P388/ADM cells showed respectively 2.0- and 270-fold resistance. Both P388/ACR and P388/ADM cells expressed large amounts of P-glycoprotein, and the amount was 3-fold higher in the P388/ACR than in the P388/ADM cells. As a result, the accumulation of vincristine and ADM were greatly reduced in P388/ACR and P388/ADM cells, as compared with the parental P388 cells. The accumulation of ACR, however, was moderately reduced in both the resistant cell lines. ACR accumulation in P388/ACR and P388/ADM cells was reduced to respectively 37 and 64% of the level in P388 cells. The amount and the activity of topoisomerase II were comparable in P388 and P388/ACR cells, but they were reduced in P388/ADM cells. Consequently, the formation of protein (topoisomerase II)-DNA cross-links induced by a topoisomerase II inhibitor was more prominent in the P388 and P388/ACR nuclei than in the P388/ADM nuclei. Notably, ACR could reduce the protein-DNA cross-links equally in the nuclei of P388, P388/ACR, and P388/ADM cells.(ABSTRACT TRUNCATED AT 250 WORDS)

New rhodomycin analogs, SS-288A and SS-288B, produced by a Streptomyces violaceus A262 mutant.

Two new rhodomycin metabolites, SS-288A and SS-288B, were specifically produced by a blocked mutant obtained from Streptomyces violaceus A262 and were respectively identified as 7,10-di(O-rhodosaminyl-deoxyfucosyl-deoxyfucosyl)-beta -rhodomycinone and -beta-isorhodomycinone.

Microbial glycosidation of some anthracycline antibiotics by an antibiotic-negative mutant of aclarubicin producer.

Microbial conversion of anthracyclinone monosaccharides using aclarubicin-negative mutant of Streptomyces galilaeus was found to produce anthracyclinone disaccharides which had either rhodinose or 2-deoxyfucose as an additional sugar. By this conversion we obtained twelve new anthracyclines from seven anthracyclines which had rhodosamine, N-monomethyldaunosamine or daunosamine at C-7 as a glycosidic sugar. All products had a reduced cytotoxic activity in comparison with those of parent compounds. However, some of them showed a therapeutically improved antitumor effects against L1210 leukemia in vivo.

Anthracycline metabolites from baumycin-producing Streptomyces sp. D788. II. New anthracycline metabolites produced by a blocked mutant strain RPM-5.

A daunorubicin-blocked mutant strain RPM-5 derived from a new baumycin-producing Streptomyces sp. D788 accumulated a major precursor metabolite D788-1 (10-carboxyl-13-deoxocarminomycin) and nine minor metabolites in the culture broth. Five among them were new with a substituent at C-10 or the altered side chains at C-9. Isolation, purification and identification of all anthracycline metabolites produced by strain RPM-5 are described with their antitumor activities against L1210 cells.

Production of new anthracycline antibiotics by microbial 4-O-methylation using a specific daunorubicin-negative mutant.

Microbial 4-O-methylation using a specific daunorubicin-blocked, nonproducing mutant provided the new anthracycline antibiotics 4-O-methylbetaclamycin T, 4-O-methylyellamycin A and 4-O-methyl-13-hydroxyoxaunomycin, from which 4-O-methyloxaunomycin and 4-O-methyl-6-deoxyoxaunomycin were then prepared by further photochemical N-demethylation. Antitumor activities in vitro and in vivo against L1210 cells were compared with those of their 4-O-demethyl derivatives. It was found that all the 4-O-methyl derivatives had a markedly reduced cytotoxicity in vitro as compared with the 4-O-demethyl compounds. However, some of them were endowed with a significantly improved antitumor activity in vivo.

Production of new anthracycline antibiotics 1-hydroxy-oxaunomycin and 6-deoxyoxaunomycin by limited biosynthetic conversion using a daunorubicin-negative mutant.

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.

Photochemically obtained N-demethyl derivatives of anthracyclines.

New N-monodemethyl and N-didemethyl derivatives were obtained from seven N-dimethylamino sugar (rhodosamine)-containing anthracyclines by photochemical reaction and their in vitro bioactivities against L1210 cell culture were compared with those of their N-dimethyl parent compounds. N-Demethyl derivatives obtained from betaclamycin T (7-O-rhodosaminyl-beta-rhodomycinone) were much more cytotoxic while those from the other six antibiotics were rather less active as compared with their parent compounds. The N-demethylation also gave a considerably greater decrease in the inhibitory activity on RNA synthesis as compared to DNA synthesis, so that the N-demethyl derivatives showed smaller IC50 ratios on DNA/RNA than their parent compounds.

Anthracycline metabolites from baumycin-producing Streptomyces sp. D788. I. Isolation of antibiotic-blocked mutants and their characterization.

Biosynthetically blocked mutants were obtained from a baumycin-producing Streptomyces sp. D788 newly isolated from soil. The first mutant isolated was a baumycin-negative but daunorubicin-accumulating mutant with a loss of 4'-substitution activity, from which all other blocked mutants were successively derived. These included a known 11-deoxydaunorubicin-producing mutant and several new types of mutants which produced mainly 10-carboxy-13-deoxocarminomycin, 10-methoxycarbonyl-13-deoxocarminomycin, their 11-deoxy derivatives or a precursor aglycone, respectively. In this paper, all the anthracycline components produced by the parent strain and its two known blocked mutants, a daunorubicin producer and a 11-deoxydaunorubicin producer, are also determined by HPLC and five new components are isolated. Cytotoxicities in vitro of all the components against L1210 cell culture are also described.

Anthracycline metabolites from Streptomyces violaceus A262. I. Isolation of antibiotic-blocked mutants from Streptomyces violaceus A262.

Five mutant (or variant) strains producing new anthracycline antibiotics were derived from Streptomyces violaceus A262 by mutagenesis treatment. Strain SE1-625 showed a limited production of three known beta-rhodomycinone diglycosides while the parent strain produced numerous unidentified beta-rhodomycinone glycosides. Strain SU2-730 was an antibiotic-blocked mutant which produced only epsilon-rhodomycinone glycosides (named epelmycins). Strains SC-7 and SE2-2385 were variants which produced alpha-citromycinone glycosides (named yellamycins) and beta-isorhodomycinone glycosides (named obelmycins), respectively. Strain SE2-2385-A1 produced alpha 2-rhodomycinone glycosides (named alldimycins). Glycosidation-less mutants which accumulated only aglycone were also obtained. Isolation of these mutants or variants and preliminary identification of their anthracycline products are described.

Anthracycline metabolites from Streptomyces violaceus A262. II. New anthracycline epelmycins produced by a blocked mutant strain SU2-730.

New anthracycline antibiotics, identified as epsilon-rhodomycinone glycosides, were isolated from the culture broth of a blocked mutant of beta-rhodomycin-producing Streptomyces violaceus A262. They were designated as epelmycins A, B, C, D and E, and assayed for their in vitro cytotoxicities against murine leukemic L1210 cell culture and the antimicrobial activities in comparison with known anthracycline antibiotics.

Anthracycline metabolites from Streptomyces violaceus A262. III. New anthracycline obelmycins produced by a variant strain SE2-2385.

New anthracycline antibiotics, designated as obelmycins A, D, E, F and G, were isolated from the culture broth of a variant strain of beta-rhodomycin-producing Streptomyces violaceus A262, identified as beta-isorhodomycinone glycosides and gamma-isorhodomycinone glycosides and assayed for their in vitro cytotoxicities against murine leukemic L1210 cell culture and the antimicrobial activities in comparison with some known anthracyclines.