Functional characterization of tlmH in Streptoalloteichus hindustanus E465-94 ATCC 31158 unveiling new insight into tallysomycin biosynthesis and affording a novel bleomycin analog

Activities of recombinant human bleomycin hydrolase on bleomycins and engineered analogues revealing new opportunities to overcome bleomycin-induced pulmonary toxicity

The bleomycins (BLMs) are widely used in combination therapies for the treatment of various cancers. Dose-dependent and cumulative pulmonary toxicity is the major cause of BLM-associated morbidity, limiting the broad uses of BLMs as anticancer drugs. The organ specificity of BLM-induced toxicity has been correlated with the expression of the hBLMH gene, encoding the human bleomycin hydrolase (hBLMH), which is poorly expressed in the lung. hBLMH hydrolyzes BLMs into the biologically inactive deamido BLMs, thereby protecting organs from BLM-induced toxicity. Here we report (i) expression of hBLMH and production and isolation of recombinant human bleomycin hydrolase (rhBLMH) from E. coli, (ii) structural characterization of deamido BLM A2 and B2 isolated from rhBLMH-catalyzed hydrolysis of BLM A2 and B2, and (iii) kinetic characterization of the rhBLMH-catalyzed hydrolysis of BLM A2 and B2, in comparison with five BLM analogues. rhBLMH from E. coli catalyzes rapid and efficient hydrolysis of all BLMs tested, exhibiting a superior catalytic efficiency for BLM B2. These findings reveal new opportunities to overcome BLM-induced pulmonary toxicity in chemotherapies, potentially by exploring BLM B2 as the preferred congener, engineering designer BLMs with optimized activity for rhBLMH, or co-administrating rhBLMH directly into the lung as a potential protein therapeutic.

Strain improvement by combined UV mutagenesis and ribosome engineering and subsequent fermentation optimization for enhanced 6'-deoxy-bleomycin Z production

The bleomycins (BLMs) are important clinical drugs extensively used in combination chemotherapy for the treatment of various cancers. Dose-dependent lung toxicity and the development of drug resistance have restricted their wide applications. 6'-Deoxy-BLM Z, a recently engineered BLM analogue with improved antitumor activity, has the potential to be developed into the next-generation BLM anticancer drug. However, its low titer in the recombinant strain Streptomyces flavoviridis SB9026 has hampered current efforts, which require sufficient compound, to pursue preclinical studies and subsequent clinical development. Here, we report the strain improvement by combined UV mutagenesis and ribosome engineering, as well as the fermentation optimization, for enhanced 6'-deoxy-BLM production. A high producer, named S. flavoviridis G-4F12, was successfully isolated, producing 6'-deoxy-BLM at above 70 mg/L under the optimized fermentation conditions, representing a sevenfold increase in comparison with that of the original producer. These findings demonstrated the effectiveness of combined empirical breeding methods in strain improvement and set the stage for sustainable production of 6'-deoxy-BLM via pilot-scale microbial fermentation.

Engineered production and evaluation of 6'-deoxy-tallysomycin H-1 revealing new insights into the structure-activity relationship of the anticancer drug bleomycin

The bleomycins (BLMs), a family of glycopeptide antibiotics, are currently used clinically in combination with a number of other agents for the treatment of malignant tumors. Other members of the BLM family include tallysomycins (TLMs), phleomycins and zorbamycin (ZBM). We previously cloned and characterized the biosynthetic gene clusters for BLMs, TLMs and ZBM. Applications of combinatorial biosynthesis strategies to the three biosynthetic machineries enabled the engineered production of several BLM analogs with unique structural characteristics and varying DNA cleavage activities, thereby providing an outstanding opportunity to study the structure-activity relationship (SAR) for the BLM family of anticancer drugs. We now report the engineered production of a new BLM-TLM-ZBM hybrid metabolite, named 6'-deoxy-TLM H-1, which consists of the 22-desmethyl-BLM aglycone, the TLM A C-terminal amine and the ZBM disaccharide, by heterologous expression of the zbmGL genes from the ZBM biosynthetic gene cluster in the Streptoalloteichus hindustanus ΔtlmH mutant strain SB8005. Evaluation of the DNA cleavage activities of 6'-deoxy-TLM H-1 as a measurement for its potential anticancer activity, in comparison with TLM H-1 and BLM A2, reveals new insight into the SAR of BLM family of anticancer drugs.The Journal of Antibiotics advance online publication, 23 August 2017; doi:10.1038/ja.2017.93.

Genome Mining of Streptomyces mobaraensis DSM40847 as a Bleomycin Producer Providing a Biotechnology Platform To Engineer Designer Bleomycin Analogues

Streptomyces mobaraensis DSM40847 has been identified by genome mining and confirmed to be a new bleomycin (BLM) producer. Manipulation of BLM biosynthesis in S. mobaraensis has been demonstrated, as exemplified by the engineered production of 6'-deoxy-BLM A2, providing a biotechnology platform for BLM biosynthesis and engineering. Comparison of DNA cleavage efficiency and kinetics among 6'-deoxy-BLM A2 and selected analogues supports the wisdom of altering the disaccharide moiety to fine-tune BLM activity.

Complete genome sequence of the actinomycete Actinoalloteichus hymeniacidonis type strain HPA 177T isolated from a marine sponge

Actinoalloteichus hymeniacidonis HPA 177T is a Gram-positive, strictly aerobic, black pigment producing and spore-forming actinomycete, which forms branching vegetative hyphae and was isolated from the marine sponge Hymeniacidon perlevis. Actinomycete bacteria are prolific producers of secondary metabolites, some of which have been developed into anti-microbial, anti-tumor and immunosuppressive drugs currently used in human therapy. Considering this and the growing interest in natural products as sources of new drugs, actinomycete bacteria from the hitherto poorly explored marine environments may represent promising sources for drug discovery. As A. hymeniacidonis, isolated from the marine sponge, is a type strain of the recently described and rare genus Actinoalloteichus, knowledge of the complete genome sequence enables genome analyses to identify genetic loci for novel bioactive compounds. This project, describing the 6.31 Mbp long chromosome, with its 5346 protein-coding and 73 RNA genes, will aid the Genomic Encyclopedia of Bacteria and Archaea project.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: an update for 2009-2010

This review is the sixth update of the original article published in 1999 on the application of MALDI mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2010. General aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, arrays and fragmentation are covered in the first part of the review and applications to various structural typed constitutes the remainder. The main groups of compound that are discussed in this section are oligo and polysaccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals. Many of these applications are presented in tabular form. Also discussed are medical and industrial applications of the technique, studies of enzyme reactions and applications to chemical synthesis.

A designer bleomycin with significantly improved DNA cleavage activity

The bleomycins (BLMs) are used clinically in combination with a number of other agents for the treatment of several types of tumors, and the BLM, etoposide, and cisplatin treatment regimen cures 90-95% of metastatic testicular cancer patients. BLM-induced pneumonitis is the most feared, dose-limiting side effect of BLM in chemotherapy, which can progress into lung fibrosis and affect up to 46% of the total patient population. There have been continued efforts to develop new BLM analogues in the search for anticancer drugs with better clinical efficacy and lower lung toxicity. We have previously cloned and characterized the biosynthetic gene clusters for BLMs from Streptomyces verticillus ATCC15003, tallysomycins from Streptoalloteichus hindustanus E465-94 ATCC31158, and zorbamycin (ZBM) from Streptomyces flavoviridis SB9001. Comparative analysis of the three biosynthetic machineries provided the molecular basis for the formulation of hypotheses to engineer novel analogues. We now report engineered production of three new analogues, 6'-hydroxy-ZBM, BLM Z, and 6'-deoxy-BLM Z and the evaluation of their DNA cleavage activities as a measurement for their potential anticancer activity. Our findings unveiled: (i) the disaccharide moiety plays an important role in the DNA cleavage activity of BLMs and ZBMs, (ii) the ZBM disaccharide significantly enhances the potency of BLM, and (iii) 6'-deoxy-BLM Z represents the most potent BLM analogue known to date. The fact that 6'-deoxy-BLM Z can be produced in reasonable quantities by microbial fermentation should greatly facilitate follow-up mechanistic and preclinical studies to potentially advance this analogue into a clinical drug.

Comparative analysis of the biosynthetic gene clusters and pathways for three structurally related antitumor antibiotics: bleomycin, tallysomycin, and zorbamycin

The biosynthetic gene clusters for the glycopeptide antitumor antibiotics bleomycin (BLM), tallysomycin (TLM), and zorbamycin (ZBM) have been recently cloned and characterized from Streptomyces verticillus ATCC15003, Streptoalloteichus hindustanus E465-94 ATCC31158, and Streptomyces flavoviridis ATCC21892, respectively. The striking similarities and differences among the biosynthetic gene clusters for the three structurally related glycopeptide antitumor antibiotics prompted us to compare and contrast their respective biosynthetic pathways and to investigate various enzymatic elements. The presence of different numbers of isolated nonribosomal peptide synthetase (NRPS) domains in all three clusters does not result in major structural differences of the respective compounds. The seemingly identical domain organization of the NRPS modules responsible for heterocycle formation, on the other hand, is contrasted by the biosynthesis of two different structural entities, bithiazole and thiazolinyl-thiazole, for BLM/TLM and ZBM, respectively. Variations in sugar biosynthesis apparently dictate the glycosylation patterns distinct for each of the BLM, TLM, and ZBM glycopeptide scaffolds. These observations demonstrate nature's ingenuity and flexibility in achieving structural differences and similarities via various mechanisms and will surely inspire combinatorial biosynthesis efforts to expand on natural product structural diversity.

Natural products for cancer chemotherapy

For over 40 years, natural products have served us well in combating cancer. The main sources of these successful compounds are microbes and plants from the terrestrial and marine environments. The microbes serve as a major source of natural products with anti‐tumour activity. A number of these products were first discovered as antibiotics. Another major contribution comes from plant alkaloids, taxoids and podophyllotoxins. A vast array of biological metabolites can be obtained from the marine world, which can be used for effective cancer treatment. The search for novel drugs is still a priority goal for cancer therapy, due to the rapid development of resistance to chemotherapeutic drugs. In addition, the high toxicity usually associated with some cancer chemotherapy drugs and their undesirable side‐effects increase the demand for novel anti‐tumour drugs active against untreatable tumours, with fewer side‐effects and/or with greater therapeutic efficiency. This review points out those technologies needed to produce the anti‐tumour compounds of the future.