Aminomethylation of heliomycin: Preparation and anticancer characterization of the first series of semi-synthetic derivatives

Water-soluble 4-(dimethylaminomethyl)heliomycin exerts greater antitumor effects than parental heliomycin by targeting the tNOX-SIRT1 axis and apoptosis in oral cancer cells

The antibiotic heliomycin (resistomycin), which is generated from Streptomyces resistomycificus, has multiple activities, including anticancer effects. Heliomycin was first described in the 1960s, but its clinical applications have been hindered by extremely low solubility. A series of 4-aminomethyl derivatives of heliomycin were synthesized to increase water solubility; studies showed that they had anti-proliferative effects, but the drug targets remained unknown. In this study, we conducted cellular thermal shift assays (CETSA) and molecular docking simulations to identify and validate that heliomycin and its water-soluble derivative, 4-(dimethylaminomethyl)heliomycin (designated compound 4-dmH) engaged and targeted with sirtuin-1 (SIRT1) in p53-functional SAS and p53-mutated HSC-3 oral cancer cells. We further addressed the cellular outcome of SIRT1 inhibition by these compounds and found that, in addition to SIRT1, the water-soluble 4-dmH preferentially targeted a tumor-associated NADH oxidase (tNOX, ENOX2). The direct binding of 4-dmH to tNOX decreased the oxidation of NADH to NAD+ which diminished NAD+-dependent SIRT1 deacetylase activity, ultimately inducing apoptosis and significant cytotoxicity in both cell types, as opposed to the parental heliomycin-induced autophagy. We also observed that tNOX and SIRT1 were both upregulated in tumor tissues of oral cancer patients compared to adjacent normal tissues, suggesting their clinical relevance. Finally, the better therapeutic efficacy of 4-dmH was confirmed in tumor-bearing mice, which showed greater tNOX and SIRT1 downregulation and tumor volume reduction when treated with 4-dmH compared to heliomycin. Taken together, our in vitro and in vivo findings suggest that the multifaceted properties of water-soluble 4-dmH enable it to offer superior antitumor value compared to parental heliomycin, and indicated that it functions through targeting the tNOX-NAD+-SIRT1 axis to induce apoptosis in oral cancer cells.

Overview of the New Bioactive Heterocycles as Targeting Topoisomerase Inhibitors Useful Against Colon Cancer

Colorectal cancer (CRC) is the third most common cancer globally, with high mortality. Metastatic CRC is incurable in most cases, and multiple drug therapy can increase patients' life expectancy by 2 to 3 years. Efforts are being made to understand the relationship between topoisomerase enzymes and colorectal cancer. Some studies have shown that higher expression of these enzymes is correlated to a poor prognosis for this type of cancer. One of the primary drugs used in the treatment of CRC is Irinotecan, which can be used in monotherapy or, more commonly, in therapeutic schemes such as FOLFIRI (Fluorouracil, Leucovorin, and Irinotecan) and CAPIRI (Capecitabine and Irinotecan). Like Camptothecin, Irinotecan and other compounds have a mechanism of action based on the formation of a ternary complex with topoisomerase I and DNA providing damage to it, therefore leading to cell death. Thus, this review focused on the principal works published in the last ten years that demonstrate a correlation between the inhibition of different isoforms of topoisomerase and in vitro cytotoxic activity against CRC by natural products, semisynthetic and synthetic compounds of pyridine, quinoline, acridine, imidazoles, indoles, and metal complexes. The results revealed that natural compounds, semisynthetic and synthetic derivatives showed potential in vitro cytotoxicity against several colon cancer cell lines, and this activity was often accompanied by the ability to inhibit both isoforms of topoisomerase (I and II), highlighting that these enzymes can be promising targets for the development of new chemotherapy against CRC. Pyridine analogs were considered the most promising for this study, while the evaluation of the real potential of natural products was limited by the lack of information in their work. Moreover, the complexes, although promising, presented as the main limitation the lack of selectivity.

Resistomycin Suppresses Prostate Cancer Cell Growth by Instigating Oxidative Stress, Mitochondrial Apoptosis, and Cell Cycle Arrest

Globally, prostate cancer is among the most threatening and leading causes of death in men. This study, therefore, aimed to search for an ideal antitumor strategy with high efficacy, low drug resistance, and no or few adverse effects. Resistomycin is a natural antibiotic derived from marine actinomycetes, and it possesses various biological activities. Prostate cancer cells (PC3) were treated with resistomycin (IC12.5: 0.65 or IC25: 1.3 µg/mL) or 5-fluorouracil (5-FU; IC25: 7 µg/mL) for 24 h. MTT assay and flow cytometry were utilized to assess cell viability and apoptosis. Oxidative stress, apoptotic-related markers, and cell cycle were also assessed. The results revealed that the IC50 of resistomycin and 5-FU on PC3 cells were 2.63 µg/mL and 14.44 µg/mL, respectively. Furthermore, treated cells with the high dose of resistomycin showed an increased number of apoptotic cells compared to those treated with the lower dose. Remarkable induction of reactive oxygen species generation and lactate dehydrogenase (LDH) leakage with high malondialdehyde (MDA), carbonyl protein (CP), and 8-hydroxyguanosine (8-OHdG) contents were observed in resistomycin-treated cells. In addition, marked declines in glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) in PC3 cells subjected to resistomycin therapy were observed. Resistomycin triggered observable cell apoptosis by increasing Bax, caspase-3, and cytosolic cytochrome c levels and decreasing Bcl-2 levels. In addition, notable downregulation of proliferating cell nuclear antigen (PCNA) and cyclin D1 was observed in resistomycin-treated cancerous cells. According to this evaluation, the antitumor potential of resistomycin, in a concentration-dependent manner, in prostate cancer cells was achieved by triggering oxidative stress, mitochondrial apoptosis, and cell cycle arrest in cancer cells. In conclusion, our investigation suggests that resistomycin can be considered a starting point for developing new chemotherapeutic agents for human prostate cancer.

Anticancer activity of Mannich bases: a review of recent literature

This report summarizes the latest published data on the antiproliferative action and cytotoxic activity of Mannich bases, a structurally heterogeneous category of chemical entities that includes compounds which are synthesized via the grafting of an aminomethyl function onto diverse substrates by means of the Mannich reaction. The present overview of the topic is an update to the information assembled in a previously published review that covered the literature up to 2014.

Water-Soluble Heliomycin Derivatives to Target i-Motif DNA

Heliomycin (also known as resistomycin) is an antibiotic with a broad spectrum of biological activities. However, low aqueous solubility and poor knowledge of its chemical properties have limited the development of this natural product. Here, we present an original scheme for the introduction of aminoalkylamine residues at positions 3, 5, and 7 of heliomycin and, using this, have prepared a series of novel water-soluble derivatives. The addition of side chains to the heliomycin scaffold significantly improves their interaction with different DNA secondary structures. One derivative, 7-deoxy-7-(2-aminoethyl)amino-10-O-methylheliomycin (8e), demonstrated affinity, stabilization potential, and good selectivity toward i-motif-forming DNA sequences over the duplex and G-quadruplex. Heliomycin derivatives therefore represent promising molecular scaffolds for further development as DNA-i-motif interacting ligands and potential chemotherapeutic agents.

Simplistic perylene-related compounds as inhibitors of tick-borne encephalitis virus reproduction

Rigid amphipathic fusion inhibitors are potent broad-spectrum antivirals based on the perylene scaffold, usually decorated with a hydrophilic group linked via ethynyl or triazole. We have sequentially simplified these structures by removing sugar moiety, then converting uridine to aniline, then moving to perylenylthiophenecarboxylic acids and to perylenylcarboxylic acid. All these polyaromatic compounds, as well as antibiotic heliomycin, still showed pronounced activity against tick-borne encephalitis virus (TBEV) with limited toxicity in porcine embryo kidney (PEK) cell line. 5-(Perylen-3-yl)-2-thiophenecarboxylic acid (5a) showed the highest antiviral activity with 50% effective concentration of approx. 1.6 nM.

Main trends in the design of semi-synthetic antibiotics of a new generation

This review summarizes main advances achieved by Russian researchers in the synthesis and characterization of semi-synthetic antibiotics of a new generation in the period from 2004 to 2019. The following classes of compounds are considered as the basis for modification: polycyclic antibacterial glycopeptides of the vancomycin group, classical macrolides, antifungal polyene macrolides, the antitumour antibiotic olivomycin A, antitumour anthracyclines and broad-spectrum antibiotics, in particular, oligomycin A, heliomycin and some other. Main trends in the design of modern anti-infective and antitumour agents over this period are considered in relation to original natural antibiotics, which have been independently discovered by Russian researchers. It is shown that a new type of hybrid structures can, in principle, be synthesized based on glycopeptides, macrolides and other antibiotics, including heterodimers containing a new benzoxaborole pharmacophore. The review addresses the influence of the length of the spacer between two antibiotic molecules on the biological activity of hybrid structures. A combination of genetic engineering techniques and methods of organic synthesis is shown to be useful for the design of new potent antifungal antibiotics based on polyenes of the amphotericin B group. Many new semi-synthetic analogues exhibit important biological properties, such as a broad spectrum of activity and low toxicity. Emphasis is given to certain aspects related to investigation of a broad range of biological activity and mechanisms of action of new derivatives.

The bibliography includes 101 references.

New Derivatives of Bacteriopurpurin with Thiolated Au (I) Complexes: Dual Darkand Light Activated Antitumor Potency

BACKGROUND

Conventional antitumor Photosensitizers (PS) are normally low toxic in the dark whereas light activation triggers massive cell death (photodynamic therapy, PDT).

OBJECTIVE

To expand the therapeutic potential of PS to dual potency cytocidal agents, taking advantage of the use of bacteriopurpurin for a deeper tissue penetration of light, and suitability of the tetrapyrrolic macrocycle for chemical modifications at its periphery.

METHODS

Conjugation of a pro-oxidant thiolate Au (I) moiety to the bacteriopurpurin core and evaluation of cytotoxicity in cell culture and in vivo.

RESULTS

New water-soluble derivatives showed micromolar cytotoxicity for cultured human tumor cell lines in the dark, including the subline with an altered drug response due to p53 inactivation. Cellular PDT with the selected conjugate, thiolate Au (I)-dipropoxybacteriopurpurinimide (compound 6) with two triphenylphosphine Au fragments, triggered rapid (within minutes) cell death. Damage to the plasma membrane (necrosis) was a hallmark of cell death by compound 6 both in the dark and upon light activation. Furthermore, one single i.v. injection of compound 6 caused retardation of transplanted syngeneic tumors at the tolerable dose. Illumination of tumors that accumulated compound 6 significantly synergized with the effect of 6 in the dark.

CONCLUSION

Complexes of virtually non-toxic, photoactivatable bacteriopurpurin with the gold-containing organic moiety are considered the dual potency antitumor agents, tentatively applicable for intractable tumors.

A Unique Prototypic Device for Radiation Therapy: The p53-Independent Antiproliferative Effect of Neutron Radiation

Radiation therapy with heavy particles including neutrons, an otherwise therapeutically perspective because of its high tissue penetration and efficient tumor damage, is currently limited by the lack of adequate equipment. An NG-24 generator (140 kg, 42 × 110 cm, ~1011 particles/s, > 14 MeV) has been designed and engineered to replace the huge and environmentally harmful neutron reactors, cyclotrons, and accelerators with a compact, portable, safe, and potent source of high-energy neutrons. We demonstrate that the neutron beam produced by NG-24 causes a significant antiproliferative effect on human tumor cell lines regardless of the status of the anti-apoptotic p53 protein. Phosphorylation of histone 2A and increased amounts of p21, cyclin D, and phospho-p53 were detectable in HCT116 colon carcinoma cells (wild-type p53) irradiated with 4 Gy several days post-treatment, accompanied by G2/M phase arrest. These treatments dramatically reduced the ability of single cells to form colonies. In the HCT116p53KO subline (p53 -/-), the G2/M arrest was independent of the aforementioned mechanisms. Hence, the NG-24 generator is a source of a powerful, therapeutically relevant neutron flux that triggers a p53-independent antiproliferative response in tumor cells.