Efficient nuclear DNA cleavage in human cancer cells by synthetic bleomycin mimics

Role of apoptosis and autophagy in folic acid-induced cytotoxicity of human breast cancer cells in vitro

Obstacles to the successful treatment of breast cancer patients with chemotherapeutic agents can be overcome with effective new strategies. It is still unclear how folic acid affects the onset and spread of breast cancer. The purpose of this study was to determine how folic acid affected the apoptotic and autophagic pathways of the breast cancer cell lines MCF-7 and MDA-MB-231. In the present study, folic acid was applied to MCF-7 and MDA-MB-231 breast cancer cell lines at different concentrations and for different durations. MTT analysis was used to investigate cytotoxic activity. All groups underwent the Tunel staining procedure to identify apoptosis and the immunofluorescence staining approach to identify the autophagic pathway. 24-hour folic acid values were accepted as the most appropriate cytotoxic dose. In MCF-7, cell cycle arrest was observed in the S phase and MDA-MB-231 G1/G0 phases. When apoptotic TUNEL staining was evaluated in both cell lines, folic acid significantly increased apoptosis. While a significant difference was observed between the groups in terms of Beclin 1 immunoreactivity in the MDA-MB-231 cell line, there was no significant difference in the MCF-7 cell line. In addition, statistical significance was not observed LC3 immunoreactivity in both cell lines. In the study, it was observed that folic acid induced autophagy at the initial stage in the MDA-MB-231 cell line but had no inductive effect in the MCF-7 cell line. In conclusion, our findings showed that folic acid has a potential cytotoxic and therapeutic effect on MCF-7 and MDA-MB-231 breast cancer cell lines.

The most reactive iron and manganese complexes with N-pentadentate ligands for dioxygen activation—synthesis, characteristics, applications

The iron and manganese complexes that activate oxygen atom play multiple role in technologically relevant reactions as well as in biological transformations, in which exist in different redox states. Among them, high-valent oxo intermediate seems to be the most important one. Iron, and/or manganese-based processes have found application in many areas, starting from catalysis and sustainable technologies, through DNA oxidative cleavage, to new substances useful in chemotherapeutic drugs. This review is not only the latest detailed list of uses of homogeneous N-pentadentate iron and manganese catalysts for syntheses of valuable molecules with huge applications in green technologies, but also a kind of "a cookbook", collecting "recipes" for the discussed complexes, in which the sources necessary to obtain a full characterization of the compounds are presented. Following the catalytic activity of metalloenzymes, and taking into account the ubiquity of iron and manganese salts, which in combination with properly designed ligands may show similarity to natural systems, the discussed complexes can find application as new anti-cancer drugs. Also, owing to ability of oxygen atom to exchange in reaction with H₂O, they can be successfully applied in photodriven reactions of water oxidation, as well as in chemically regenerated fuel cells as a redox catalyst.

Syntheses, crystal structures of two Fe(III) Schiff base complexes with chelating o-vanillin aroylhydrazone and exploration of their bio-relevant activities

Two novel Fe(III) complexes, Fe(HL¹)₂Cl·1.25H₂O (1) and Fe(HL²)₂·Et₃NH·H₂O (2) (H₂L¹ = o-vanillin benzoylhydrazone, H₃L² = o-vanillin salicylhydrazone) are prepared. X-ray single crystal diffraction confirms that the hydrazone ligands can be chelated to iron centre resulting in a six-coordinate octahedral configuration. Both complexes show major intercalation effect to the herring sperm deoxyribonucleic acid (HS-DNA) with high binding constants of 2.01 × 10⁴ M^-1 and 2.24 × 10⁴ M^-1, respectively. Molecular docking studies reveal both complexes can intercalate at the gap of DC5-DG2 and DG6-DC1 base pairs of DNA hexamer (1Z3F). The interaction of the complex 1 with plasmid pBR322 DNA induces distinguishable alterations of the DNA morphology. Further, the structure of plasmid pBR322 DNA treated with complex 1 in the presence of ascorbic acid has been damaged probably due to the reactive oxygen species (ROS) generation. What's more, both complexes show high affinity with bovine serum albumin (BSA), the binding constants measured by fluorescence techniques are 5.75 × 10⁶ M^-1 and 4.39 × 10⁷ M^-1, respectively. Molecular docking demonstrates that the complexes prefer the binding pocket of site III (subdomain IIB) of BSA (PDB ID: 4F5S). Similarly, dynamic light scattering (DLS) reveals that the complexes not only bind to BSA but also induce bigger size aggregates as the concentration increases.

Iron-Based Catalytically Active Complexes in Preparation of Functional Materials

Iron complexes are particularly interesting as catalyst systems over the other transition metals (including noble metals) due to iron’s high natural abundance and mediation in important biological processes, therefore making them non-toxic, cost-effective, and biocompatible. Both homogeneous and heterogeneous catalysis mediated by iron as a transition metal have found applications in many industries, including oxidation, C-C bond formation, hydrocarboxylation and dehydration, hydrogenation and reduction reactions of low molecular weight molecules. These processes provided substrates for industrial-scale use, e.g., switchable materials, sustainable and scalable energy storage technologies, drugs for the treatment of cancer, and high molecular weight polymer materials with a predetermined structure through controlled radical polymerization techniques. This review provides a detailed statement of the utilization of homogeneous and heterogeneous iron-based catalysts for the synthesis of both low and high molecular weight molecules with versatile use, focusing on receiving functional materials with high potential for industrial application.

Iron Compounds as Anticancer Agents

Many ferrocene complexes have been prepared for their oncological potential. Some derive from molecules with known biological effects (taxanes, podophyllotoxine, artemisine, SAHA, etc.) while others are synthetic molecules selected for their cytotoxic effects (N-alkylaminoferrocenes and ferrocenyl alkylpyridinium). Although these complexes have received a great deal of attention, the field of iron metallodrugs is not limited to them. A number of inorganic complexes of iron(ii) and iron(iii) with possible anticancer effects have also been published, although research into their biological effects is often only at an early stage. This chapter also includes iron chelators, molecules that are administered in non-metallic form but whose cytotoxic species are their coordination complexes of iron generated in vivo. The most emblematic molecule of this family is bleomycin, used as an anticancer agent in many chemotherapies. To these can be added the iron chelates originally synthesized to treat iron overload, some of which have been shown to possess interesting anticancer properties. They have been, and continue to be, the subject of many clinical trials, whether alone or in combination. Thus, the area of iron metallodrugs includes molecules with very different structures and reactivity, studied from a number of different perspectives, but focused on increasing the number of molecules at our disposal for combatting cancer.

Folate receptors and transporters: biological role and diagnostic/therapeutic targets in cancer and other diseases

Folate receptors and transporters and one-carbon metabolism continue to be important areas of study given their essential roles in an assortment of diseases and as targets for treatment of cancer and inflammation. Reflecting this, every 2 years, the Folate Receptor Society organizes an international meeting, alternating between North America and Europe, where basic and translational scientists, clinical oncologists and rheumatologists from both academia and industry convene in an informal setting. The 7th International Symposium on Folate Receptors and Transporters was held in Sant’Alessio Siculo (ME), Taormina, Italy from 1st to 5th of October 2018, organized by Dr. Mariangela Figini from Fondazione IRCCS Istituto Nazionale dei Tumori, Milan. Following the format of previous meetings, more than 50 scientists from 9 different countries attended the 2018 meeting to share ongoing developments, discuss current research challenges and identify new avenues in basic and translational research. An important feature of this meeting was the participation of young investigators and trainees in this area, two (A. Dekhne and N. Verweij) of whom were awarded fellowships to attend this meeting as a recognition of the high scientific quality of their work. This report provides a synopsis of the highlights presented in the following sessions: Barton Kamen Lecture; Targeting one-carbon metabolism in cytosol and mitochondria; Structure and biology of the one-carbon solute transporters; Physiology and pathophysiology of folate receptors and transporters; Folate receptors for targeting tumors and inflammatory diseases; Conventional and new anti-folate drugs for treating inflammatory diseases and cancer; Imaging; Ongoing clinical trials; and Chimeric Antigen Receptor cell therapies of cancer.

Importance of Metal-Ion Exchange for the Biological Activity of Coordination Complexes of the Biomimetic Ligand N4Py

Metal coordination complexes can display interesting biological activity, as illustrated by the bleomycins (BLMs), a family of natural antibiotics that when coordinated to a redox-active metal ion, show antitumor activity. Yet, which metal ion is required for the activity in cells is still subject to debate. In this study, we described how different metal ions affect the intracellular behavior and activity of the synthetic BLM-mimic N, N-bis(2-pyridylmethyl)- N-bis(2-pyridyl)methylamine (N4Py). Our study shows that a mixture of iron(II), copper(II), and zinc(II) complexes can be generated when N4Py is added to cell cultures but that the metal ion can also be exchanged by other metal ions present in cells. Moreover, the combination of chemical data, together with the performed biological experiments, shows that the active complex causing oxidative damage to cells is the FeII-N4Py complex and not per se the metal complex that was initially added to the cell culture medium. Finally, it is proposed that the high activity observed upon the addition of the free N4Py ligand is the result of a combination of scavenging of biologically relevant metals and oxidative damage caused by the iron(II) complex.

Catalytically Active Single-Chain Polymeric Nanoparticles: Exploring Their Functions in Complex Biological Media

Dynamic single-chain polymeric nanoparticles (SCPNs) are intriguing, bioinspired architectures that result from the collapse or folding of an individual polymer chain into a nanometer-sized particle. Here we present a detailed biophysical study on the behavior of dynamic SCPNs in living cells and an evaluation of their catalytic functionality in such a complex medium. We first developed a number of delivery strategies that allowed the selective localization of SCPNs in different cellular compartments. Live/dead tests showed that the SCPNs were not toxic to cells while spectral imaging revealed that SCPNs provide a structural shielding and reduced the influence from the outer biological media. The ability of SCPNs to act as catalysts in biological media was first assessed by investigating their potential for reactive oxygen species generation. With porphyrins covalently attached to the SCPNs, singlet oxygen was generated upon irradiation with light, inducing spatially controlled cell death. In addition, Cu(I)- and Pd(II)-based SCPNs were prepared and these catalysts were screened in vitro and studied in cellular environments for the carbamate cleavage reaction of rhodamine-based substrates. This is a model reaction for the uncaging of bioactive compounds such as cytotoxic drugs for catalysis-based cancer therapy. We observed that the rate of the deprotection depends on both the organometallic catalysts and the nature of the protective group. The rate reduces from in vitro to the biological environment, indicating a strong influence of biomolecules on catalyst performance. The Cu(I)-based SCPNs in combination with the dimethylpropargyloxycarbonyl protective group showed the best performances both in vitro and in biological environment, making this group promising in biomedical applications.

Re-expression of Selected Epigenetically Silenced Candidate Tumor Suppressor Genes in Cervical Cancer by TET2-directed Demethylation

DNA hypermethylation is extensively explored as therapeutic target for gene expression modulation in cancer. Here, we re-activated hypermethylated candidate tumor suppressor genes (TSGs) (C13ORF18, CCNA1, TFPI2, and Maspin) by TET2-induced demethylation in cervical cancer cell lines. To redirect TET2 to hypermethylated TSGs, we engineered zinc finger proteins (ZFPs), which were first fused to the transcriptional activator VP64 to validate effective gene re-expression and confirm TSG function. ChIP-Seq not only revealed enriched binding of ZFPs to their intended sequence, but also considerable off-target binding, especially at promoter regions. Nevertheless, results obtained by targeted re-expression using ZFP-VP64 constructs were in line with cDNA overexpression; both revealed strong growth inhibition for C13ORF18 and TFPI2, but not for CCNA1 and Maspin. To explore effectivity of locus-targeted demethylation, ZFP-TET2 fusions were constructed which efficiently demethylated genes with subsequent gene re-activation. Moreover, targeting TET2 to TFPI2 and C13ORF18, but not CCNA1, significantly decreased cell growth, viability, and colony formation in cervical cancer cells compared to a catalytically inactive mutant of TET2. These data underline that effective re-activation of hypermethylated genes can be achieved through targeted DNA demethylation by TET2, which can assist in realizing sustained re-expression of genes of interest.

Prolonged re-expression of the hypermethylated gene EPB41L3 using artificial transcription factors and epigenetic drugs

Epigenetic silencing of tumor suppressor genes (TSGs) is considered a significant event in the progression of cancer. For example, EPB41L3, a potential biomarker in cervical cancer, is often silenced by cancer-specific promoter methylation. Artificial transcription factors (ATFs) are unique tools to re-express such silenced TSGs to functional levels; however, the induced effects are considered transient. Here, we aimed to improve the efficiency and sustainability of gene re-expression using engineered zinc fingers fused to VP64 (ZF-ATFs) or DNA methylation modifiers (ZF-Tet2 or ZF-TDG) and/or by co-treatment with epigenetic drugs [5-aza-2'-deoxycytidine or Trichostatin A (TSA)]. The EPB41L3-ZF effectively bound its methylated endogenous locus, as also confirmed by ChIP-seq. ZF-ATFs reactivated the epigenetically silenced target gene EPB41L3 (∼ 10-fold) in breast, ovarian, and cervical cancer cell lines. Prolonged high levels of EPB41L3 (∼ 150-fold) induction could be achieved by short-term co-treatment with epigenetic drugs. Interestingly, for otherwise ineffective ZF-Tet2 or ZF-TDG treatments, TSA facilitated re-expression of EPB41L3 up to twofold. ATF-mediated re-expression demonstrated a tumor suppressive role for EPB41L3 in cervical cancer cell lines. In conclusion, epigenetic reprogramming provides a novel way to improve sustainability of re-expression of epigenetically silenced promoters.