Barminomycin forms GC-specific adducts and virtual interstrand crosslinks with DNA

Chemistry and biology of specialized metabolites produced by Actinomadura

Covering: up to the end of 2022In recent years rare Actinobacteria have become increasingly recognised as a rich source of novel bioactive metabolites. Actinomadura are Gram-positive bacteria that occupy a wide range of ecological niches. This review highlights about 230 secondary metabolites produced by Actinomadura spp., reported until the end of 2022, including their bioactivities and selected biosynthetic pathways. Notably, the bioactive compounds produced by Actinomadura spp. demonstrate a wide range of activities, including antimicrobial, antitumor and anticoccidial effects, highlighting their potential in various fields.

Doxorubicin and other anthracyclines in cancers: Activity, chemoresistance and its overcoming

Anthracyclines have been important and effective treatments against a number of cancers since their discovery. However, their use in therapy has been complicated by severe side effects and toxicity that occur during or after treatment, including cardiotoxicity. The mode of action of anthracyclines is complex, with several mechanisms proposed. It is possible that their high toxicity is due to the large set of processes involved in anthracycline action. The development of resistance is a major barrier to successful treatment when using anthracyclines. This resistance is based on a series of mechanisms that have been studied and addressed in recent years. This work provides an overview of the anthracyclines used in cancer therapy. It discusses their mechanisms of activity, toxicity, and chemoresistance, as well as the approaches used to improve their activity, decrease their toxicity, and overcome resistance.

Antitumor compounds from actinomycetes: from gene clusters to new derivatives by combinatorial biosynthesis

Covering: up to October 2008. Antitumor compounds produced by actinomycetes and novel derivatives generated by combinatorial biosynthesis are reviewed (with 318 references cited.) The different structural groups for which the relevant gene clusters have been isolated and characterized are reviewed, with a description of the strategies used for the generation of the novel derivatives and the activities of these compounds against tumor cell lines.

Barminomycin functions as a potent pre-activated analogue of Adriamycin

The anthracycline Adriamycin is known to form adducts with DNA, but requires prior activation by formaldehyde. In contrast, the anthracycline barminomycin is also able to form adducts with DNA, but does not require activation by formaldehyde. Barminomycin, therefore, appears to function as a pre-activated form of Adriamycin. The DNA adducts formed by both anthracyclines are bound covalently to only one strand of DNA, but both also stabilise duplex DNA sufficiently that they can be detected as virtual interstrand crosslinks in heat denaturation electrophoretic crosslinking assays. The barminomycin-DNA adducts form extremely rapidly with DNA, and at exceedingly low concentrations (approximately 50-fold lower than with Adriamycin in the presence of excess formaldehyde), both characteristics consistent with barminomycin being in a pre-activated state, hence, undergoing a bimolecular reaction with DNA compared with the trimolecular reaction (drug, formaldehyde and DNA) required with Adriamycin. Surprisingly, barminomycin-DNA adducts are substantially more stable (essentially irreversible) than Adriamycin-DNA adducts (half life of approximately 25 h at 37 degrees C). Due to this understanding of the reactivity of barminomycin and its exceptional cytotoxicity (1000-fold more cytotoxic than Adriamycin), detailed structural studies of barminomycin-DNA adducts are now warranted, both in vitro and in tumour cells.

Formaldehyde activation of mitoxantrone yields CpG and CpA specific DNA adducts

Recently we have found that mitoxantrone, like Adria-mycin, can be activated by formaldehyde and subsequently form adducts which stabilise double-stranded DNA in vitro. This activation by formaldehyde may be biologically relevant since formaldehyde levels are elevated in those tumours in which mitoxan-trone is most cytotoxic. In vitro transcription analysis revealed that these adducts block the progression of RNA polymerase during transcription and cause truncated RNA transcripts. There was an absolute requirement for both mitoxantrone and formaldehyde in transcriptional blockage formation and the activated complex was found to exhibit site specificity, with blockage occurring prior to CpG and CpA sites in the DNA (non-template strand). The stability of the adduct at 37 degrees C was site dependent. The half-lives ranged from 45 min to approximately 5 h and this was dependent on both the central 2 bp blockage site as well as flanking sequences. The CpG specificity of mitoxantrone adduct sites was also confirmed independently by a lambda exonuclease digestion assay.