New anthra[2,3-b]furancarboxamides: A role of positioning of the carboxamide moiety in antitumor properties

In silico screening and synthesis of stable tilmicosin-hydrazone derivatives as potential DNA disruptors towards Staphylococcus aureus

In this study, 30 tilmicosin-hydrazone derivatives were designed using MOE software. Six candidate molecules with strong binding affinity to DNA or DNA-Topo II complexes, as indicated by molecular docking results, were synthesized. These candidates were evaluated for their in vitro antibacterial activities against common Gram-positive and Gram-negative bacteria. Compounds Z-12 and Z-22 demonstrated superior inhibitory effects against most tested strains compared to reference drugs tilmicosin and erythromycin, with minimum inhibitory concentrations (MIC) of 1 μg/mL against S. aureus 25,923 and S. aureus 29,213. HPLC results indicated that Z-12 and Z-22 exhibited improved stability in acidic aqueous solutions compared to tilmicosin. UV-vis, fluorescence spectroscopy, and gel electrophoresis studies confirmed their intercalation into DNA base pairs via a static quenching mechanism. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) revealed irreversible oxidation processes on the glassy carbon electrode, providing insights into their potential metabolic pathways. Finally, a mouse wound infection model demonstrated that Z-12 and Z-22 exhibited good antibacterial efficacy, biocompatibility, and enhanced wound healing effects, surpassing those of tilmicosin. These findings, coupled with their prolonged metabolic half-life, highlight their potential as effective antibacterial agents.

Naphthoindole-2-carboxamides as a lipophilic chemotype of hetarene-anthraquinones potent against P-gp resistant tumor cells

The acquisition of multidrug resistance (MDR) to chemotherapy is a major obstacle to successful cancer treatment. Aiming to improve the potency of anthraquinone-derived antitumor compounds against MDR cancer cells, we employed a rational design approach to develop new heteroarene-fused anthraquinones. Shifting the carboxamide group in the naphtho[2,3-f]indole scaffold from the 3-position to 2 increased the lipophilicity and P-glycoprotein (P-gp) binding of the derivatives, potentially enhancing their ability to circumvent P-gp-mediated MDR. To validate the computations, we developed a scheme for heterocyclization into esters of naphtho[2,3-f]indole-2-carboxylic acid, based on the 5-endo-dig cyclization of 2-alkynyl-3-amino-1,4-dimethoxyanthraquinone under mild basic conditions using tetra-n-butylammonium fluoride (TBAF). The synthesized naphthoindole-2-carboxamides, particularly compound 1a bearing (S)-3-aminopyrrolidine in the carboxamide fragment, demonstrated the highest antiproliferative activity. Most importantly, 1a suppressed the growth of the P-gp-positive K562/4 leukemia tumor cell line (resistance index = 2.4), while its 3-isomer LCTA-2640 and Dox did not (RI = 125 and 140, respectively). Studies of intracellular uptake and distribution showed that 1a, unlike its 3-substituted isomer, effectively accumulated in resistant tumor cells, confirming the correlation between in silico and experimental data. The lead compound 1a interacts with DNA duplex and inhibits topoisomerase 1 but does not induce oxidative stress. Treatment with 1a increases the population of apoptotic cells in both K562 and K562/4 sublines, regardless of the cell cycle phase. Taken together, this work provides an interesting example of how a little modification in chemical structure can lead to striking differences in antitumor properties. In conclusion, we have identified a potent class of compounds that offer distinct advantages in combating resistant tumor cells.

A Spin-Labeled Derivative of Gossypol

Gossypol and its derivatives arouse interest due to their broad spectrum of biological activities. Despite its wide potential application, there is no reported example of gossypol derivatives bearing stable radical functional groups. The first gossypol nitroxide hybrid compound was prepared here via formation of a Schiff base. By this approach, synthesis of a gossypol nitroxide conjugate was performed by condensation of gossypol with a 4-amino-TEMPO (4-amino-2,2,6,6-tetramethylpiperidin-1-oxyl) free radical, which afforded the target product in high yield. Its structure was proven by a combination of NMR and EPR spectroscopy, infrared spectroscopy, mass spectrometry, and high-resolution mass spectrometry. In addition, the structure of the gossypol nitroxide was determined by single-crystal X-ray diffraction measurements. In crystals, the paramagnetic Schiff base exists in an enamine-enamine tautomeric form. The tautomer is strongly stabilized by the intra- and intermolecular hydrogen bonds promoted by the resonance of π-electrons in the aromatic system. NMR analyses of the gossypol derivative proved that in solutions, the enamine-enamine tautomeric form prevailed. The gossypol nitroxide at micromolar concentrations suppressed the growth of tumor cells; however, compared to gossypol, the cytotoxicity of the obtained conjugate was substantially lower.

Thiadiazole-, selenadiazole- and triazole-fused anthraquinones as G-quadruplex targeting anticancer compounds

G-quadruplex (G4) ligands attract considerable attention as potential anticancer therapeutics. In this study we proposed an original scheme for synthesis of azole-fused anthraquinones and prepared a series of G4 ligands carrying amino- or guanidinoalkylamino side chains. The heterocyclic core and structure of the terminal groups strongly affect on binding to G4-forming oligonucleotides, cellular accumulation and antitumor potency of compounds. In particular, thiadiazole- and selenadiazole- but not triazole-based ligands inhibit the proliferation of tumor cells (e.g. K562 leukemia) and stabilize primarily telomeric and c-MYC G4s. Anthraselenadiazole derivative 11a showed a good affinity to c-MYC G4 in vitro and down-regulated expression of c-MYC oncogene in cellular conditions. Further studies revealed that anthraselenadiazole 11a provoked cell cycle arrest and apoptosis in a dose- and time-dependent manner inhibiting K562 cells growth. Taken together, this work gives a valuable example that the closely related heterocycles may cause a significant difference in biological properties of G4 ligands.

Synthesis and antitumor activity of cyclopentane-fused anthraquinone derivatives

In our pursuit of developing novel analogs of anthracyclines with enhanced antitumor efficacy and safety, we have designed a synthesis scheme for 4,11-dihydroxy-5,10-dioxocyclopenta[b]anthracene-2-carboxamides. These newly synthesized compounds exhibit remarkable antiproliferative potency against various mammalian tumor cell lines, including those expressing activated mechanisms of multidrug resistance. The structure of the diamine moiety in the carboxamide side chain emerges as a critical determinant for anticancer activity and interaction with key targets such as DNA, topoisomerase 1, and ROS induction. Notably, the introduced modification to the doxorubicin structure results in significantly increased lipophilicity, cellular uptake, and preferential distribution in lysosomes. Consequently, while maintaining an impact on anthracyclines targets, these novel derivatives also demonstrate the potential to induce cytotoxicity through pathways associated with lysosomes. In summary, derivatives of cyclic diamines, particularly 3-aminopyrrolidine, can be considered a superior choice compared to aminosugars for incorporation into natural and semi-synthetic anthracyclines or new anthraquinone derivatives, aiming to circumvent efflux-mediated drug resistance.

Comparative Evaluation of the Antibacterial and Antitumor Activities of 9-Phenylfascaplysin and Its Analogs

Based on the results of our own preliminary studies, the derivative of the marine alkaloid fascaplysin containing a phenyl substituent at C-9 was selected to evaluate the therapeutic potential in vivo and in vitro. It was shown that this compound has outstandingly high antimicrobial activity against Gram-positive bacteria, including antibiotic-resistant strains in vitro. The presence of a substituent at C-9 of the framework is of fundamental importance, since its replacement to neighboring positions leads to a sharp decrease in the selectivity of the antibacterial action, which indicates the presence of a specific therapeutic target in bacterial cells. On a model of the acute bacterial sepsis in mice, it was shown that the lead compound was more effective than the reference antibiotic vancomycin seven out of nine times. However, ED50 value for 9-phenylfascaplysin (7) was similar for the unsubstituted fascaplysin (1) in vivo, despite the former being significantly more active than the latter in vitro. Similarly, assessments of the anticancer activity of compound 7 against various variants of Ehrlich carcinoma in mice demonstrated its substantial efficacy. To conduct a structure-activity relationship (SAR) analysis and searches of new candidate compounds, we synthesized a series of analogs of 9-phenylfascaplysin with varying aryl substituents. However, these modifications led to the reduced aqueous solubility of fascaplysin derivatives or caused a loss of their antibacterial activity. As a result, further research is required to explore new avenues for enhancing its pharmacokinetic characteristics, the modification of the heterocyclic framework, and optimizing of treatment regimens to harness the remarkable antimicrobial potential of fascaplysin for practical usage.

Synthesis and Biological Evaluation of Chalconesulfonamides: En Route to Proapoptotic Agents with Antiestrogenic Potency

Breast and other estrogen receptor α-positive cancers tend to develop resistance to existing drugs. Chalcone derivatives possess anticancer activity based on their ability to form covalent bonds with targets acting as Michael acceptors. This study aimed to evaluate the anticancer properties of a series of chalcones (7a-l) with a sulfonamide group attached to the vinyl ketone moiety. Chalconesulfonamides showed a potent antiproliferative effect at low micromolar concentrations against several cancer cell lines, including ERα-positive 4-hydroxytamoxifen-resistant MCF7/HT2. Immunoblotting of samples treated with the lead compound 7e revealed its potent antiestrogenic activity (ERα/GREB1 axis) and induction of PARP cleavage (an apoptosis marker) in breast cancer cells. The obtained compounds represent a promising basis for further development of targeted drugs blocking hormone pathways in cancer cells.

Computational and Biophysical Characterization of Heterocyclic Derivatives of Anthraquinone against Human Aurora Kinase A

Human Aurora kinase A (AurA) has recently garnered the attention of researchers worldwide as a promising effective mitotic drug target for its involvement in cancer and related inflammatory anomalies. This study has explored the binding affinity of newly identified heteroarene-fused anthraquinone derivatives against AurA. Molecular docking analyses showed that all the heteroanthraquinone compounds bind to AurA with different affinities. Molecular dynamics simulation studies revealed that the compounds maintained relatively stable binding modes in the active site pocket while inducing minimal conformational changes in the AurA structure, interacting with key residues through several noncovalent interactions, including hydrogen bonds. Fluorescence spectroscopy and biolayer interferometry binding assays with synthesized compounds against recombinantly expressed AurA further verified their binding efficacy. Naphthoisatine 3 proved to be the best binder, with compounds anthraimidazole 5 and anthrathiophene 2 showing comparable results. Overall, this study indicates decent binding of heterocyclic derivatives of anthraquinone with the target AurA, which can further be assessed by performing enzymatic assays and cellular studies. The studies also highlight the applicability of the heteroarene-fused anthraquinone scaffold to construct selective and potent inhibitors of Aurora kinases after necessary structural modifications for the development of new anticancer drugs.

Bis(chloroacetamidino)-Derived Heteroarene-Fused Anthraquinones Bind to and Cause Proteasomal Degradation of tNOX, Leading to c-Flip Downregulation and Apoptosis in Oral Cancer Cells

Simple Summary

New-generation anthraquinone derivatives attached with different heterocycles and bearing chloroacetamidines in the side chains have been synthesized to reduce side effects and drug resistance. In this study, we identified the cellular target of the studied compounds through ligand binding assays and in silico simulations. Our results illustrate that the studied compounds bound to and targeted the tumor-associated NADH oxidase (tNOX) in oral cancer cells. tNOX is a growth-related protein and is found to be expressed in cancer cells but not in non-transformed cells, and its knockdown by RNA interference in tumor cells overturns cancer phenotypes, supporting its role in cellular growth. We also identified that tNOX bound to the studied compounds and underwent degradation, which was correlated with apoptosis induction in oral cancer cells.

Abstract

Anthraquinone-based intercalating compounds, namely doxorubicin and mitoxantrone, have been used clinically based on their capacity to bind DNA and induce DNA damage. However, their applications have been limited by side effects and drug resistance. New-generation anthraquinone derivatives fused with different heterocycles have been chemically synthesized and screened for higher anticancer potency. Among the compounds reported in our previous study, 4,11-bis(2-(2-chloroacetamidine)ethylamino)anthra[2,3-b]thiophene-5,10-dione dihydrochloride (designated 2c) was found to be apoptotic, but the direct cellular target responsible for the cytotoxicity remained unknown. Here, we report the synthesis and anticancer properties of two other derivatives, 4,11-bis(2-(2-chloroacetamidine)ethylamino)naphtho[2,3-f]indole-5,10-dione dihydrochloride (2a) and 4,11-bis(2-(2-chloroacetamidine)ethylamino)-2-methylanthra[2,3-b]furan-5,10-dione dihydrochloride (2b). We sought to identify and validate the protein target(s) of these derivatives in oral cancer cells, using molecular docking simulations and cellular thermal shift assays (CETSA). Our CETSA results illustrate that these derivatives targeted the tumor-associated NADH oxidase (tNOX, ENOX2), and their direct binding downregulated tNOX in p53-functional SAS and p53-mutated HSC-3 cells. Interestingly, the compounds targeted and downregulated tNOX to reduce SIRT1 deacetylase activity and increase Ku70 acetylation, which triggers c-Flip ubiquitination and induces apoptosis in oral cancer cells. Together, our data highlight the potential value of these heteroarene-fused anthraquinones in managing cancer by targeting tNOX and augmenting apoptosis.

DNA Intercalators as Anticancer Agents

Cancer is one of the most prevailing disease conditions which occurs due to uncontrolled cell division either due to natural mutation to the genes or due to changes induced by physical, chemical, or biological carcinogens. According to WHO, it is the second leading cause of death worldwide and has reported 10 million deaths in 2020. Hence there arises the need for better chemotherapies and DNA intercalators are one such emerging therapy for cancer. DNA intercalating agents reversibly intercalate with the double-helical structure of DNA by interacting with adjacent base pairs and disrupting the structure of DNA and thereby causing cell death. Here we discuss the different classes of organo-intercalators used in cancer therapy describing their anticancer and intercalation ability by different methods along with their structure-activity relationship and mechanism of action.

Heterocyclic ring expansion yields anthraquinone derivatives potent against multidrug resistant tumor cells

Chemical modifications of anthraquiones are aimed at novel derivatives with improved antitumor properties. Emergence of multidrug resistance (MDR) due to overexpression of transmembrane ATP binding cassette transporters, in particular, MDR1/P-glycoprotein (Pgp), can limit the use of anthraquinone based drugs. Previously we have demonstrated that annelation of modified five-membered heterocyclic rings with the anthraquinone core yielded a series of compounds with optimized antitumor properties. In the present study we synthesized a series of anthraquinone derivatives with six-membered heterocycles. Selected new compounds showed the ability to kill parental and MDR tumor cell lines at low micromolar concentrations. Molecular docking into the human Pgp model revealed a stronger interaction of 2-methylnaphtho[2,3-g]quinoline-3-carboxamide 17 compared to naphtho[2,3-f]indole-3-carboxamide 3. The time course of intracellular accumulation of compound 17 in parental K562 leukemia cells and in Pgp-positive K562/4 subline was similar. In contrast, compound 3 was readily effluxed from K562/4 cells and was significantly less potent for this subline than for K562 cells. Together with reported strategies of drug optimization of the anthracycline core, these results add ring expansion to the list of perspective modifications of heteroarene-fused anthraquinones.

An approach to pharmacological targets of pyrrole family from a medicinal chemistry viewpoint

Pyrrole is one of the most widely used heterocycles in the pharmaceutical industry. Due to the importance of pyrrole structure in drug design and development, herein, we tried to conduct an extensive review of the bioactive pyrrole based compounds reported recently. The bioactivity of pyrrole derivatives varies, so in the review, we categorized them based on their direct pharmacologic targets. Therefore, readers are able to find the variety of biologic targets for pyrrole containing compounds easily. This review explains around seventy different biologic targets for pyrrole based derivatives, so, it is helpful for medicinal chemists in design and development novel bioactive compounds for different diseases. This review presents an extensive meaningful structure activity relationship for each reported structure as much as possible. The review focuses on papers published between 2018 and 2020.

Subchronic Toxicity Study of Oral Anthrafuran on Rabbits

A new antitumor multi-target drug anthrafuran, with cellular targets such as topoisomerase I/II and some protein kinases, was obtained in Gause Institute of New Antibiotics and was demonstrated to have a reliable specific effect on different murine and human tumor models by oral administration. In this study, we focused on the evaluation of subchronic toxicity of oral anthrafuran drug formulation (AF) on Chinchilla rabbits. The absence of any changes in the condition or behavior of animals was shown for oral anthrafuran. Changes with reversible and dose-dependent hepato- and nephrotoxicity at low doses, as well as hemato- and gastrointestinal toxicity at high doses, were confirmed pathomorphologically. The identified toxic properties are extremely valuable, since oral anthrafuran does not have the limiting cardio- and myelotoxicity. Anthrafuran with 2 mg/kg/day or 6 mg/kg/day doses was administrated orally over 15 days. Investigations include assessment of the body weight, hematological and serum biochemical parameters and urinalysis, electrocardiography and pathomorphological evaluation of the internal organs. Quantitative data were processed statistically with Student’s t-Test, p < 0.05. Revealed during the subchronic study were the favorable toxicological properties of oral anthrafuran as opposed to clinical anthracyclines, oral idarubicin, or parenteral doxorubicin, which allows it to be considered promising for further research.

Thiophene-2-carboxamide derivatives of anthraquinone: A new potent antitumor chemotype

The anthraquinone scaffold has long been known as a source of efficacious antitumor drugs. In particular, the various chemical modifications of the side chains in this scaffold have yielded the compounds potent for the wild type tumor cells, their counterparts with molecular determinants of altered drug response, as well as in vivo settings. Further exploring the chemotype of anticancer heteroarene-fused anthraquinones, we herein demonstrate that derivative of anthra[2,3-b]thiophene-2-carboxamide, (compound 8) is highly potent against a panel of human tumor cell lines and their drug resistant variants. Treatment with submicromolar or low micromolar concentrations of 8 for only 30 min was sufficient to trigger lethal damage of K562 chronic myelogenous leukemia cells. Compound 8 (2.5 μM, 3-6 h) induced an apoptotic cell death as determined by concomitant activation of caspases 3 and 9, cleavage of poly(ADP-ribose) polymerase, increase of Annexin V/propidium iodide double stained cells, DNA fragmentation (subG1 fraction) and a decrease of mitochondrial membrane potential. Neither a significant interaction with double stranded DNA nor strong inhibition of the DNA dependent enzyme topoisomerase 1 by 8 were detectable in cell free systems. Laser scanning confocal microscopy revealed that some amount of 8 was detectable in mitochondria as early as 5 min after the addition to the cells; exposure for 1 h caused significant morphological changes and clustering of mitochondria. The bioisosteric analog 2 in which the thiophene ring was replaced with furan was less active although the patterns of cytotoxicity of both derivatives were similar. These results point at the specific role of the sulfur atom in the antitumor properties of carboxamide derivatives of heteroarene-fused anthraquinone.

Furan-2-carboxamide derivative, a novel microtubule stabilizing agent induces mitotic arrest and potentiates apoptosis in cancer cells

The vital role played by microtubules in the cell division process, marks them as a potential druggable target to decimate cancer. A novel furan-2-carboxamide based small molecule, is a selective microtubule stabilizing agent (MSA) with IC₅₀ ranging from 4 µM to 8 µM in different cancer cell lines. Inhibition of tubulin polymerization or stabilization of tubulin polymers abrogates chromosomal segregation during cell division, results in cell cycle arrest and leads to cell death due to the delayed repair mechanism. A novel furan-2-carboxamide based small molecule exhibited potent anti-proliferative and anti-metastatic property In-Vitro against the panel of cancer cells. Annexin V-FITC/PI, double staining reveals potent cytotoxic effect of SH09 against HeLa cells. FACS analysis displays induction of G2/M arrest and accumulation of subG1 population of cells upon treatment with SH09. Molecular docking study unveils SH09 binding affinity to the Taxol binding pocket of tubulin proteins and MM-GBSA also confirms strong binding energies of SH09 with tubulin proteins.

Heteroarene-fused anthraquinone derivatives as potential modulators for human aurora kinase B

The quest for effective anticancer therapeutics continues to be extensively pursued. Over the past century, several drugs have been developed, however, a majority of these drugs have a poor therapeutic index and increased toxicity profile. Hence, there still exists ample opportunity to discover safe and effective anticancer drugs. Aurora Kinase B (AurB), a member of the Aurora kinase family and a key regulator of mitotic cell division, is found to be frequently overexpressed in a variety of human cancers and has thus emerged as an attractive target for the design of anticancer therapeutics. In the present study, a structure-based scaffold hopping approach was utilized to modify the heterocyclic moiety of (S)-3-(3-aminopyrrolidine-1-carbonyl)-4,11-dihydroxy-2-methylanthra [2,3-b]furan-5,10-dione (anthrafuran 1) to generate a series of heteroarene-fused anthraquinone derivatives, which were then subjected to virtual screening for the identification of potential AurB inhibitors. The obtained hits were subsequently synthesized and evaluated by using a combination of in silico and biophysical techniques for elucidating their in vitro binding and inhibition activity with recombinantly expressed AurB. Four identified hits presented an improved binding profile as compared to their parent analog anthrafuran 1. One derivative, anthrathiophene 2 demonstrated excellent in vitro inhibition of AurB (7.3 μM).

Akt and Src mediate the photocrosslinked fibroin-induced neural differentiation

Neural transplantation is a promising modality for treatment of neurodegenerative diseases, traumatic brain injury and stroke. Biocompatible scaffolds with optimized properties improve the survival of transplanted neural cells and differentiation of progenitor cells into the desired types of neurons. Silk fibroin is a biocompatible material for tissue engineering. Here, we describe thin-film scaffolds based on photocrosslinked methacrylated silk fibroin (FBMA). These scaffolds exhibit an increased mechanical stiffness and improved water stability. Photocrosslinking of fibroin increased its rigidity from 25 to 480 kPa and the contact angle from 59.7 to 70.8, the properties important for differentiation of neural cells. Differentiation of SH-SY5Y neuroblastoma cells on FBMA increased the length of neurites as well as the levels of neural differentiation markers MAP2 and βIII-tubulin. Growth of SH-SY5Y cells on the unmodified fibroin and FBMA substrates led to a spontaneous phosphorylation of Src and Akt protein kinases critical for neuronal differentiation; this effect was paralleled by neural cell adhesion molecule elevation. Thus, FBMA is an easily manufactured, cytocompatible material with improved and sustainable properties applicable for neural tissue engineering.

Amides of pyrrole- and thiophene-fused anthraquinone derivatives: A role of the heterocyclic core in antitumor properties

Heteroarene-fused anthraquinone derivatives represent a class of perspective anticancer drug candidates capable of targeting multiple vital processes including drug resistance. Taking advantage of previously demonstrated potential of amide derivatives of heteroarene-fused anthraquinones, we herein dissected the role of the heterocyclic core in antitumor properties. A new series of naphtho[2,3-f]indole-3- and anthra[2,3-b]thiophene-3-carboxamides was synthesized via coupling the respective acids with cyclic diamines. New compounds demonstrated a submicromolar antiproliferative potency close to doxorubicin (Dox) against five tumor cell lines of various tissue origin. In contrast to Dox, the new compounds were similarly cytotoxic for HCT116 colon carcinoma cells (wild type p53) and their isogenic p53 knockout counterparts. Modification of the heterocyclic core changed the targeting properties: the best-in-series naphtho[2,3-f]indole-3-carboxamide 8 formed more affine complexes with DNA duplex than furan and thiophene analogs, a property that can be translated into a stronger inhibition of topoisomerase 1 mediated DNA unwinding. At tolerable doses the water soluble derivative 8 significantly inhibited tumor growth (up to 79%) and increased the lifespan (153%) of mice bearing P388 lymphoma transplants. Together with better solubility for parenteral administration and well tolerance by animals of the indole derivative 8 indicates prospects for further search of new antitumor drug candidates among the heteroarene-fused anthraquinones.

Experimental Evaluation of Anticancer Efficiency and Acute Toxicity of Anthrafuran for Oral Administration

The new antitumor agent anthrafuran has demonstrated a consistent effect in murine tumor models when administered parenterally due to the simultaneous inhibition of multiple cellular targets such as topoisomerases I/II and protein kinases. In this study, we assessed the anticancer efficiency and acute toxicity of anthrafuran administered orally. The action of anthrafuran was studied on transplanted tumor models which included P388 leukemia, Ca755 mammary adenocarcinoma, LLC lung carcinoma, and T47D human breast cancer xenografts on Balb/c nude mice. A significant antitumor efficacy of oral anthrafuran was revealed for all tested tumor models as follows: T/C_max = 219% for P388, TGI_max = 91% for Ca755, TGI_max = 84% with CR_max = 54% for LLC, and T/C = 38% for T47D. The optimal treatment schedule of orally administered anthrafuran was 70–100 mg/kg given daily for five days. The LD₅₀ value of orally administered anthrafuran (306.7 mg/kg) in mice was six times higher than that for i.p. administration (52.5 mg/kg). The rates of antitumor efficacy and acute toxicity indicate the high potential for further research on anthrafuran as a new original oral anticancer multitarget agent with an expected satisfactory tolerability and bioavailability.

Novel anthraquinone compounds as anticancer agents and their potential mechanism

Anthraquinones exhibit a unique anticancer activity. Since their discovery, medicinal chemists have made several structural modifications, resulting in the design and synthesis of a large number of novel anthraquinone compounds with different biological activities. In general, anthraquinone compounds have been considered to have anticancer activity mainly through DNA damage, cycle arrest and apoptosis. However, recent studies have shown that novel anthraquinone compounds may also inhibit cancer through paraptosis, autophagy, radiosensitising, overcoming chemoresistance and other methods. This Review article provides an overview of novel anthraquinone compounds that have been developed as anticancer agents in recent years and focuses on their anticancer mechanism.

Specific stabilization of promoter G-Quadruplex DNA by 2,6-disubstituted amidoanthracene-9,10-dione based dimeric distamycin analogues and their selective cancer cell cytotoxicity

We have designed and synthesized anthraquinone containing compounds which have oligopyrrole side chains of varying lengths. These compounds stabilized the G-quadruplex DNA formed in the promoter regions of c-MYC oncogenes selectively over the duplex DNA. These observations were recorded using UV-vis spectroscopic titrations, fluorescence measurements and circular dichroism (CD) spectral titrations. The potency of the compounds to stabilize the G4 DNA has been shown from the thermal denaturation experiments. The compound interacts with c-MYC G-quadruplex DNA through stacking mode as obtained from ethidium bromide displacement assay, cyclic voltammetric titration, and docking experiments. Molecular modeling studies suggested that the stacking of the anthraquinone moiety over the G-tetrad of the G4 structures are responsible for the stability of such quadruplex secondary structure. Furthermore, polymerase stop assay also supported the formation of stable G4 structures in the presence of the above-mentioned compounds. The compounds have shown selective cancer cell (HeLa and HEK293T) cytotoxicity over normal cells (NIH3T3 and HDFa) under in vitro conditions as determined from MTT based cell viability assay. Apoptosis was found to be the mechanistic pathway underlying the cancer cell cytotoxicity as obtained from Annexin V-FITC and PI dual staining assay which was further substantiated by nuclear morphological changes as observed by AO/EB dual staining assay. Cellular morphological changes, as well as nuclear condensation and fragmentation upon treatment with these compounds, were observed under bright field and confocal microscopy.

Therapeutic strategies for targeting telomerase in cancer

Telomere and telomerase play important roles in abnormal cell proliferation, metastasis, stem cell maintenance, and immortalization in various cancers. Therefore, designing of drugs targeting telomerase and telomere is of great significance. Over the past two decades, considerable knowledge regarding telomere and telomerase has been accumulated, which provides theoretical support for the design of therapeutic strategies such as telomere elongation. Therefore, the development of telomere-based therapies such as nucleoside analogs, non-nucleoside small molecules, antisense technology, ribozymes, and dominant negative human telomerase reverse transcriptase are being prioritized for eradicating a majority of tumors. While the benefits of telomere-based therapies are obvious, there is a need to address the limitations of various therapeutic strategies to improve the possibility of clinical applications. In this study, current knowledge of telomere and telomerase is discussed, and therapeutic strategies based on recent research are reviewed.

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.