An in vitro comparative study with furyl-1,4-quinones endowed with anticancer activities

Vitamin C (Ascorbate) and Redox Topics in Cancer

Significance: Vitamin C (ascorbate), in regard to its effectiveness against malignancies, has had a controversial history in cancer treatment. It has been shown that in vitro and in vivo anticancer efficacy of ascorbate relies on its pro-oxidant effect mainly from an increased generation of reactive oxygen species (ROS). A growing understanding of its anticancer activities and pharmacokinetic properties has prompted scientists to re-evaluate the significance of ascorbate in cancer treatment. Recent Advances: A recent resurge in ascorbate research emerged after discovering that, at high doses, ascorbate preferentially kills Kirsten-Ras (K-ras)- and B-raf oncogene (BRAF)-mutant cancer cells. In addition, some of the main hallmarks of cancer cells, such as redox homeostasis and oxygen-sensing regulation (through inhibition of hypoxia-inducible factor-1 alpha [HIF-1α] activity), are affected by vitamin C. Critical Issues: Currently, there is no clear consensus from the literature in regard to the beneficial effects of antioxidants. Results from both human and animal studies provide no clear evidence about the benefit of antioxidant treatment in preventing or suppressing cancer development. Since pro-oxidants may affect both normal and tumor cells, the extremely low toxicity of ascorbate represents a main advantage. This guarantees the safe inclusion of ascorbate in clinical protocols to treat cancer patients. Future Directions: Current research could focus on elucidating the wide array of reactions between ascorbate and reactive species, namely ROS, reactive nitrogen species as well as reactive sulfide species, and their intracellular molecular targets. Unraveling these mechanisms could allow researchers to assess what could be the optimal combination of ascorbate with standard treatments.

Caspase-3: A primary target for natural and synthetic compounds for cancer therapy

Caspases, a group of protease enzymes (cysteine proteases), exist as inactive zymogens in the cells and execute apoptosis (programmed cell death). Caspase-3, an executioner caspase, plays an imperative role in apoptosis and becomes a primary target for cancer treatment. A number of analogues of quinazoline, quinazolinone, indoloquinazolines, quinone, naphthoquinones, pyrroloiminoquinones, styrylquinolines, tetheredtetrahydroquinoline, fluoroquinolone, thiosemicarbazones, benzotriazole, pyrimidines, chalcone, and carbazoles have been reported till date, representing caspase-3 mediated apoptosis for cancer therapy. Simultaneously, plant isolates, including lysicamine, podophyllotoxin, and majoranolide, have also been claimed for caspase-3-mediated apoptosis-induced cytotoxicity. Procaspase-activating compound-1 (PAC-1) is the first FDA approved orphan drug, and its synthetic derivative WF-208 also showed fascinating caspase-3 mediated anticancer activity. Till date, a large number of compounds have been reported and patented for their caspase-3-mediated cytotoxicity and now scientist is also focusing to introduce new compounds in market to encompass anticancer activity.

In Vitro Inhibition of Hsp90 Protein by Benzothiazoloquinazolinequinones Is Enhanced in The Presence of Ascorbate. A Preliminary In Vivo Antiproliferative Study

A series of benzo[g]benzothiazolo[2,3-b]quinazoline-7,12-quinones were prepared from 2-acylnaphthohydroquinones and 2-aminobenzothiazoles and were evaluated for their in vitro antiproliferative activity. After screening using the MTT reduction assay, their IC50 values were calculated on a panel of cancer cells (T24, DU-145, MCF-7). Current standard anticancer drugs were included as control, and their calculated IC50 values were 7.8 and 23.5 µM for 5-fluorouracil and tamoxifen, respectively. Non-cancer cells (AG1523) were included to assess cancer cell sensitivity and drug selectivity. Four members of the series, with IC50 values from 0.11 to 2.98 µM, were chosen for further assays. The selected quinones were evaluated regarding their effects on cancer cell proliferation (clonogenic assay) and on Hsp90 and poly(ADPribose)polymerase (PARP) protein integrity. The most active compound (i.e., 15) substantially inhibited colony forming unit (CFU) formation at 0.25 µM. In the presence of ascorbate, it induced an oxidative cleavage of Hsp90 but had no effect on PARP protein integrity. In an in vivo animal model, it discreetly increased the mean survival time (m.s.t.) of tumor-bearing mice. In light of these results, compound 15 represents a potential lead-molecule to be further developed.

Double-strand cleavage of DNA by a polyamide-phenazine-di-N-oxide conjugate

Phenazine and its derivatives have been widely applied as nucleic acid cleavage agents due to active oxygen activating the C-H bond of the substrate. However, diffusion of oxygen radicals limits their potential applications in the DNA-targeted metal-free drug. Introduction of groove binder moiety such as polyamide enhanced the regional stability of radical molecules and reduced cytotoxicity of the drugs. In this work, we described the design and synthesis of a polyamide-modified phenazine-di-N-oxide as a DNA double-strand cleavage agent. The gel assays showed the hybrid conjugates can effectively break DNA double strands in a non-random manner under physiological conditions. The probable binding mode to DNA was investigated by sufficient spectral experiments, revealing weak interaction between hybrid ligand and nucleic acid molecules. The results of our study have implications on the design of groove-binding hybrid molecules as new artificial nucleases and may provide a strategy for developing efficient and safe DNA cleavage reagents.

The application of engineered liver tissues for novel drug discovery

INTRODUCTION

Drug-induced liver injury remains a major cause of drug attrition. Furthermore, novel drugs are being developed for treating liver diseases. However, differences between animals and humans in liver pathways necessitate the use of human-relevant liver models to complement live animal testing during preclinical drug development. Microfabrication tools and synthetic biomaterials now allow for the creation of tissue subunits that display more physiologically relevant and long-term liver functions than possible with declining monolayers.

AREAS COVERED

The authors discuss acellular enzyme platforms, two-dimensional micropatterned co-cultures, three-dimensional spheroidal cultures, microfluidic perfusion, liver slices and humanized rodent models. They also present the use of cell lines, primary liver cells and induced pluripotent stem cell-derived human hepatocyte-like cells in the creation of cell-based models and discuss in silico approaches that allow integration and modeling of the datasets from these models. Finally, the authors describe the application of liver models for the discovery of novel therapeutics for liver diseases.

EXPERT OPINION

Engineered liver models with varying levels of in vivo-like complexities provide investigators with the opportunity to develop assays with sufficient complexity and required throughput. Control over cell-cell interactions and co-culture with stromal cells in both two dimension and three dimension are critical for enabling stable liver models. The validation of liver models with diverse sets of compounds for different applications, coupled with an analysis of cost:benefit ratio, is important for model adoption for routine screening. Ultimately, engineered liver models could significantly reduce drug development costs and enable the development of more efficacious and safer therapeutics for liver diseases.

Replacement of a quinone by a 5-O-acetylhydroquinone abolishes the accidental necrosis inducing effect while preserving the apoptosis-inducing effect of renieramycin M on lung cancer cells

Renieramycin M (1), a bistetrahydroisoquinolinequinone alkaloid isolated from the marine sponge Xestospongia sp., has been reported to possess promising anticancer effects. However, its accidental necrosis inducing effect has limited further development due to concerns of unwanted toxicity. The presence of two quinone moieties in its structure was demonstrated to induce accidental necrosis and increase reactive oxygen species (ROS) levels. Therefore, one quinone of 1 was modified to produce the 5-O-acetylated hydroquinone derivative (2), and 2 dramatically reduced the accidental necrosis inducing effect while preserving the apoptosis-inducing effect of parent 1 on lung cancer H23 cells. Addition of the antioxidant N-acetylcysteine suppressed the accidental necrosis mediated by 1, suggesting that its accidental necrosis inducing effect was ROS-dependent. The fluorescent probe dihydroethidium revealed that the accidental necrosis mediated by 1 was due to its ability to generate intracellular superoxide anions. Interestingly, the remaining quinone in 2 was required for its cytotoxicity, as the 5,8,15,18-O-tetraacetylated bishydroquinone derivative (3) exhibited weak cytotoxicity compared to 1 and 2. The present study demonstrates a simple way to eliminate the undesired accidental necrosis inducing effect of substances that may be developed as improved anticancer drug candidates.