Contributions of NMR to the understanding of the coordination chemistry and DNA interactions of metallo-bleomycins

Anti-cancer property and DNA binding interaction of first row transition metal complexes: A decade update

Metal ions carry out a wide variety of functions, including acid-base/redox catalysis, structural functions, signaling, and electron transport. Understanding the interactions of transition metal complexes with biomacromolecules is essential for biology, medicinal chemistry, and the production of synthetic metalloenzymes. After the coincidental discovery of cisplatin, importance of the metal complexes in biochemistry became a top priority for inquiry. In this review, a decade update on various synthetic strategies to first row transition metal complex and their interaction with DNA through non-covalent binding are explored. Moreover, this effort provides an excellent analysis on the efficacy of theoretical and practical approaches to the systematic generation of new non-platinum based metallodrugs for anti-cancer therapeutics.

Interaction of Blenoxane and Congeners Bleomycins A2 and B2 with Human Plasma Proteins Using Circular Dichroism Spectroscopy

Bleomycin is a glycopeptide congeners' family of antitumor antibiotics employed for the treatment of several types of tumors such as squamous cell carcinomas and malignant lymphomas. The general chemical structure is constituted by three main portions: (i) a metal binding domain that is recognized to be responsible for the DNA cleavage activity; (ii) a DNA binding domain via the 1-4' bithiazole moiety; and (iii) a carbohydrate domain thought to be responsible for the accumulation of bleomycin in some cancer cells. To date, a limited number of protein interactions with bleomycin have been studied, but the plasma binding has not yet been determined. Here, we explore this aspect of the protein binding capacity of bleomycin to the two most abundant plasma proteins, human serum albumin (HSA) and α1-acid glycoprotein (AGP), which are known to bind and to be carriers of many drug molecules using spectroscopic techniques, such as circular dichroism, UV-vis absorbance, and fluorescence. The results showed that bleomycin binds to plasma proteins with an order-of-magnitude higher affinity for AGP than HSA. This is particularly important as AGP is an acute phase protein and is overexpressed in cancer patients. This should be taken into consideration as it could affect the therapeutic effect of the bleomycin dosage.

Polyphosphate Reverses the Toxicity of the Quasi-Enzyme Bleomycin on Alveolar Endothelial Lung Cells In Vitro

The anti-cancer antitumor antibiotic bleomycin(s) (BLM) induces athyminic sites in DNA after its activation, a process that results in strand splitting. Here, using A549 human lung cells or BEAS-2B cells lunc cells, we show that the cell toxicity of BLM can be suppressed by addition of inorganic polyphosphate (polyP), a physiological polymer that accumulates and is released from platelets. BLM at a concentration of 20 µg ml-1 causes a decrease in cell viability (by ~70%), accompanied by an increased DNA damage and chromatin expansion (by amazingly 6-fold). Importantly, the BLM-caused effects on cell growth and DNA integrity are substantially suppressed by polyP. In parallel, the enlargement of the nuclei/chromatin in BLM-treated cells (diameter, 20-25 µm) is normalized to ~12 µm after co-incubation of the cells with BLM and polyP. A sequential application of the drugs (BLM for 3 days, followed by an exposure to polyP) does not cause this normalization. During co-incubation of BLM with polyP the gene for the BLM hydrolase is upregulated. It is concluded that by upregulating this enzyme polyP prevents the toxic side effects of BLM. These data might also contribute to an application of BLM in COVID-19 patients, since polyP inhibits binding of SARS-CoV-2 to cellular ACE2.

Structural changes of Zn(II)bleomycin complexes when bound to DNA hairpins containing the 5'-GT-3' and 5'-GC-3' binding sites studied through NMR spectroscopy

Bleomycins are antitumor antibiotics that can chelate a metal center and cause site-specific DNA cleavage at 5'-Gpyrimidine-3' regions of DNA. These antibiotics are successful in the treatment of various cancers, but are known to cause pulmonary fibrosis to patients under bleomycin regimes. Substantial research has resulted in the development of over 300 bleomycin analogs, aiming to improve the therapeutic index of the drug. Previous studies have proposed that the lung toxicity caused by bleomycin is related to the C-terminal regions of these drugs, which have been shown to closely interact with DNA in metal-bleomycin-DNA complexes. Some of the research studying metallo-bleomycin-DNA interactions have suggested three different binding modes of the metal form of the drug to DNA, including total and/or partial intercalation, and minor groove binding. However, there is still lack of consensus regarding this matter, and solid conclusions on the subject have not yet been established. Previously we investigated the diverse levels of disruption caused to DNA hairpins containing 5'-GC-3' and 5'-GT-3' binding sites, which are consequence of the binding of bleomycins with different C-termini. The results of these investigation indicate that both the DNA-binding site and the bleomycin C-termini have an impact on the final conformations of drug and target. The present study focuses on the structural alterations exhibited by Zn(II)bleomycin-A₂, -B₂, -A₅ and Zn(II)peplomycin upon binding to DNA hairpins containing 5'-GC-3' and 5'-GT-3' binding sites. Evidence that each Zn(II)bleomycin is structurally affected depending on both its C-terminus and the DNA-binding site present in the hairpin is provided.

The Interaction of the Metallo-Glycopeptide Anti-Tumour Drug Bleomycin with DNA

The cancer chemotherapeutic drug, bleomycin, is clinically used to treat several neoplasms including testicular and ovarian cancers. Bleomycin is a metallo-glycopeptide antibiotic that requires a transition metal ion, usually Fe(II), for activity. In this review, the properties of bleomycin are examined, especially the interaction of bleomycin with DNA. A Fe(II)-bleomycin complex is capable of DNA cleavage and this process is thought to be the major determinant for the cytotoxicity of bleomycin. The DNA sequence specificity of bleomycin cleavage is found to at 5′-GT* and 5′-GC* dinucleotides (where * indicates the cleaved nucleotide). Using next-generation DNA sequencing, over 200 million double-strand breaks were analysed, and an expanded bleomycin sequence specificity was found to be 5′-RTGT*AY (where R is G or A and Y is T or C) in cellular DNA and 5′-TGT*AT in purified DNA. The different environment of cellular DNA compared to purified DNA was proposed to be responsible for the difference. A number of bleomycin analogues have been examined and their interaction with DNA is also discussed. In particular, the production of bleomycin analogues via genetic manipulation of the modular non-ribosomal peptide synthetases and polyketide synthases in the bleomycin gene cluster is reviewed. The prospects for the synthesis of bleomycin analogues with increased effectiveness as cancer chemotherapeutic agents is also explored.

Schiff bases in medicinal chemistry: a patent review (2010-2015)

INTRODUCTION

Schiff bases are synthetically accessible and structurally diverse compounds, typically obtained by facile condensation between an aldehyde, or a ketone with primary amines. Schiff bases contain an azomethine (-C = N-) linkage that stitches together two or more biologically active aromatic/heterocyclic scaffolds to form various molecular hybrids with interesting biological properties. Schiff bases are versatile metal complexing agents and have been known to coordinate all metals to form stable metal complexes with vast therapeutic applications. Areas covered: This review aims to provide a comprehensive overview of the various patented therapeutic applications of Schiff bases and their metal complexes from 2010 to 2015. Expert opinion: Schiff bases are a popular class of compounds with interesting biological properties. Schiff bases are also versatile metal complexing ligands and have been used to coordinate almost all d-block metals as well as lanthanides. Therapeutically, Schiff bases and their metal complexes have been reported to exhibit a wide range of biological activities such as antibacterial including antimycobacterial, antifungal, antiviral, antimalarial, antiinflammatory, antioxidant, pesticidal, cytotoxic, enzyme inhibitory, and anticancer including DNA damage.