Anti-cancer activity of nitrones in the Apc(Min/+) model of colorectal cancer

Tunable Zinc-Mediated Reductive Cyclization of Diastereomeric 3-Nitro-4-phenacyl-2-(trihalomethyl)chromanes to Fused Pyrroline N-Oxides, Pyrrolines, and Pyrrolidines

Reductive cyclization of trans,trans- and trans,cis-isomers of the 2-CF3-substituted 3-nitro-4-phenacylchromanes with Zn-based reductive systems, depending on the conditions, affords 4-CF3-substituted 1,3a,4,9b-tetrahydrochromeno[3,4-b]pyrrole 3-oxides, 1,3a,4,9b-tetrahydrochromeno[3,4-b]pyrroles, or 1,2,3,3a,4,9b-hexahydrochromeno[3,4-b]pyrroles in good yields without changing the relative configuration of the pyran ring. A similar process involving the 2-CCl3-substituted 3-nitro-4-phenacylchromanes is accompanied by reductive dehalogenation to form the corresponding 4-dichloromethyl-substituted fused chromanes along with the 3-(2-hydroxyaryl)-2-(2,2-dichlorovinyl)-5-phenyl-2H-pyrroline 1-oxides as pyran ring opening products. The structure and relative configuration of the obtained products was reliably confirmed by X-ray diffraction analysis and 2D NMR spectroscopy.

Animal Models of Colorectal Cancer: From Spontaneous to Genetically Engineered Models and Their Applications

Colorectal cancer is one of the most common gastrointestinal malignancies in humans, affecting approximately 1.8 million people worldwide. This disease has a major social impact and high treatment costs. Animal models allow us to understand and follow the colon cancer progression; thus, in vivo studies are essential to improve and discover new ways of prevention and treatment. Dietary natural products have been under investigation for better and natural prevention, envisioning to show their potential. This manuscript intends to provide the readers a review of rodent colorectal cancer models available in the literature, highlighting their advantages and disadvantages, as well as their potential in the evaluation of several drugs and natural compounds’ effects on colorectal cancer.

Novel quinoline derivatives carrying nitrones/oximes nitric oxide donors: Design, synthesis, antiproliferative and caspase-3 activation activities

Novel quinoline derivatives carrying nitrones and oxime as nitric oxide donors were prepared and characterized using different spectroscopic techniques. Nitrones can release nitric oxide in larger amounts compared to corresponding oximes. Antiproliferative screening results showed that the 2-benzylthioquinoline nitrones 6e and 6f and the 2-methylthio analogues 6g and 6h exhibited promising antiproliferative activity especially against leukemia and colon cancer cell lines. Compounds 6c, 6e, and 6f exhibited higher potency as anticancer agents compared to doxorubicin, with IC₅₀ ranging from 0.45 to 0.91 μM. A remarkable overexpression of caspase-3 protein levels was observed in cells treated with the tested compounds. Compound 6e exhibited more pre-G1 apoptosis and cell cycle arrest at the G2/M phase than in other phases. These results revealed that the tested compounds can cause programmed cell death through overexpression of caspase 3, which may be attributed to the release of nitric oxide.

Antiproliferative activity of novel isatinyl/indanyl nitrones (INs) as potential spin trapping agents of free radical intermediates

A series of ketonitrones derived from isatin and indanone (INs) were synthesized and evaluated for their antiproliferative activities against several human cancer cell lines. Then, the antioxidant properties of these substrates were measured by the DPPH test to report their biological activity in terms of their spin trapping action. In particular, one substrate has showed very high biological and scavenging activity, probably due to the strong correlation between its spin trapping activity and structure.

NO and HNO donors, nitrones, and nitroxides: Past, present, and future

The biological effects attributed to nitric oxide (^• NO) and nitroxyl (HNO) have been extensively studied, propelling their array of putative clinical applications beyond cardiovascular disorders toward other age-related diseases, like cancer and neurodegenerative diseases. In this context, the unique properties and reactivity of the N-O bond enabled the development of several classes of compounds with potential clinical interest, among which ^• NO and HNO donors, nitrones, and nitroxides are of particular importance. Although primarily studied for their application as cardioprotective agents and/or molecular probes for radical detection, continuous efforts have unveiled a wide range of pharmacological activities and, ultimately, therapeutic applications. These efforts are of particular significance for diseases in which oxidative stress plays a key pathogenic role, as shown by a growing volume of in vitro and in vivo preclinical data. Although in its early stages, these efforts may provide valuable guidelines for the development of new and effective N-O-based drugs for age-related disorders. In this report, we review recent advances in the chemistry of NO and HNO donors, nitrones, and nitroxides and discuss its pharmacological significance and potential therapeutic application.

Melatonin and Nitrones As Potential Therapeutic Agents for Stroke

Stroke is a disease of aging affecting millions of people worldwide, and recombinant tissue-type plasminogen activator (r-tPA) is the only treatment approved. However, r-tPA has a low therapeutic window and secondary effects which limit its beneficial outcome, urging thus the search for new more efficient therapies. Among them, neuroprotection based on melatonin or nitrones, as free radical traps, have arisen as drug candidates due to their strong antioxidant power. In this Perspective article, an update on the specific results of the melatonin and several new nitrones are presented.

A comprehensive spectroscopic investigation of α-(2-naphthyl)-N-methylnitrone: a computational study on photochemical nitrone–oxaziridine conversion and thermal E–Z isomerization processes

CASSCF and 2-layer hybrid ONIOM-based computational studies on α-(2-naphthyl)-N-methylnitrone have proposed its photochemical oxaziridine formation and thermal E–Z isomerization mechanisms.

SOD therapeutics: latest insights into their structure-activity relationships and impact on the cellular redox-based signaling pathways

SIGNIFICANCE

Superoxide dismutase (SOD) enzymes are indispensable and ubiquitous antioxidant defenses maintaining the steady-state levels of O2·(-); no wonder, thus, that their mimics are remarkably efficacious in essentially any animal model of oxidative stress injuries thus far explored.

RECENT ADVANCES

Structure-activity relationship (half-wave reduction potential [E1/2] versus log kcat), originally reported for Mn porphyrins (MnPs), is valid for any other class of SOD mimics, as it is dominated by the superoxide reduction and oxidation potential. The biocompatible E1/2 of ∼+300 mV versus normal hydrogen electrode (NHE) allows powerful SOD mimics as mild oxidants and antioxidants (alike O2·(-)) to readily traffic electrons among reactive species and signaling proteins, serving as fine mediators of redox-based signaling pathways. Based on similar thermodynamics, both SOD enzymes and their mimics undergo similar reactions, however, due to vastly different sterics, with different rate constants.

CRITICAL ISSUES

Although log kcat(O2·(-)) is a good measure of therapeutic potential of SOD mimics, discussions of their in vivo mechanisms of actions remain mostly of speculative character. Most recently, the therapeutic and mechanistic relevance of oxidation of ascorbate and glutathionylation and oxidation of protein thiols by MnP-based SOD mimics and subsequent inactivation of nuclear factor κB has been substantiated in rescuing normal and killing cancer cells. Interaction of MnPs with thiols seems to be, at least in part, involved in up-regulation of endogenous antioxidative defenses, leading to the healing of diseased cells.

FUTURE DIRECTIONS

Mechanistic explorations of single and combined therapeutic strategies, along with studies of bioavailability and translational aspects, will comprise future work in optimizing redox-active drugs.

Genetic variations in stem cell-related genes and colorectal cancer prognosis

BACKGROUND

Many properties of cancer cells are reminiscent of those in normal stem cells. Genes important to stem cell development have been significantly implicated in the etiology and clinical outcome of colorectal cancer (CRC). However, the associations of genetic variations in these genes with CRC prognosis have not yet been elucidated.

METHODS

We analyzed the effects of eight potentially functional single nucleotide polymorphisms (SNPs) in six stem cell-related genes on the prognosis of a well-characterized population of 380 Chinese CRC patients diagnosed from February 2006 to January 2010.

RESULTS

The most significant finding was related to rs879882, a variant in the 5' region of POU5F1 gene which encodes a protein essential for embryonic stem cell self-renewal and pluripotency, and induced pluripotent stem cell reprogramming. The variant-containing genotypes of rs879882 were associated with an increased risk of recurrence (hazard ratio [HR] = 2.10, 95% confidence interval [CI] 1.17-3.76, P = 0.01). In chemotherapy-stratified analysis, the association remained borderline significant in patients receiving chemotherapy (HR = 1.97, 95% CI 0.89-4.34, P = 0.09). In addition, a nonsynonymous SNP of APC gene was also significantly associated with recurrence risk in chemotherapy-treated patients (HR = 2.63, 95% CI 1.14-6.06 P = 0.02). Further analyses showed a combined effect of the two SNPs in predicting CRC recurrence in patients receiving chemotherapy (P = 0.04) but not in those without chemotherapy (P = 0.43). Moreover, an exploratory multivariate assessment model indicated that these two variants enhanced the power to predict recurrence after chemotherapy.

CONCLUSION

We presented one of the first epidemiologic studies showing that stem cell-related genetic variants may impact CRC clinical outcomes, especially in chemotherapy-treated patients.

Potential implication of the chemical properties and bioactivity of nitrone spin traps for therapeutics

Nitrone therapeutics has been employed in the treatment of oxidative stress-related diseases such as neurodegeneration, cardiovascular disease and cancer. The nitrone-based compound NXY-059, which is the first drug to reach clinical trials for the treatment of acute ischemic stroke, has provided promise for the development of more robust pharmacological agents. However, the specific mechanism of nitrone bioactivity remains unclear. In this review, we present a variety of nitrone chemistry and biological activity that could be implicated for the nitrone's pharmacological activity. The chemistries of spin trapping and spin adduct reveal insights on the possible roles of nitrones for altering cellular redox status through radical scavenging or nitric oxide donation, and their biological effects are presented. An interdisciplinary approach towards the development of novel synthetic antioxidants with improved pharmacological properties encompassing theoretical, synthetic, biochemical and in vitro/in vivo studies is covered.

Anti-cancer activity of nitrones and observations on mechanism of action

The nitrone compound PBN, α-phenyl-tert-butylnitrone, and closely related nitrones have anti-cancer activity in several experimental cancer models. The three experimental models most extensively studied include A) the rat choline deficiency liver cancer model, B) the rat C6 glioma model and C) the mouse APC(Min/+) colon cancer model. The two PBN-nitrones mostly studied are PBN and a PBN derivative 2,4-disulfophenyl-tert-butylnitrone, referred as OKN-007. OKN-007 is a proprietary compound that has had extensive commercial development (designated as NXY-059) for another indication, acute ischemic stroke, and after extensive clinical studies was shown to lack efficacy for this indication but was shown to be very safe for human use. This compound administered orally in the rat glioma model has potent activity in treating fully formed gliomas. In this report observations made on the PBN-nitrones in experimental cancer models will be summarized. In addition the experimental results will be discussed in the general framework of the properties of the compounds with a view to try to understand the mechanistic basis of how the PBN-nitrones act as anti-cancer agents. Possible mechanisms related to the suppression of NO production, S-nitrosylation of critical proteins and inhibition of NF-κB activation are discussed.

Translational research involving oxidative stress and diseases of aging

There is ample mounting evidence that reactive oxidant species are exacerbated in inflammatory processes, many pathological conditions, and underlying processes of chronic age-related diseases. Therefore there is increased expectation that therapeutics can be developed that act in some fashion to suppress reactive oxidant species and ameliorate the condition. This has turned out to be more difficult than at first expected. Developing therapeutics for indications in which reactive oxidant species are an important consideration presents some unique challenges. We discuss important questions including whether reactive oxidant species should be a therapeutic target, the need to recognize the fact that an antioxidant in a defined chemical system may be a poor antioxidant operationally in a biological system, and the importance of considering that reactive oxidant species may accompany the disease or pathological system rather than being a causative factor. We also discuss the value of having preclinical models to determine if the processes that are important in causing the disease under study are critically dependent on reactive oxidant species events and if the therapeutic under consideration quells these processes. In addition we discuss measures of success that must be met in commercial research and development and in preclinical and clinical trials and discuss as examples our translational research effort in developing nitrones for the treatment of acute ischemic stroke and as anti-cancer agents.

Conformational and configurational analysis of an N,N carbonyl dipyrrinone-derived oximate and nitrone by NMR and quantum chemical calculations

The geometries and relative energies of new N,N carbonyl dipyrrinone-derived oxime molecules (E/Z-s-cis 4a and E/Z-s-cis 4b) have been investigated. The calculated energies, molecular geometries, and (1) H/(13) C NMR chemical shifts agree with experimental data, and the results are presented herein. The E-s-cis conformations of 4a and 4b and the Z-s-cis conformation of 5b were found to be the thermodynamically most stable isomers with the oxime hydrogen atom or the methyl functional group adopting an anti-orientation with respect to the dipyrrinone group. This conformation was unambiguously supported by a number of 2D NMR experiments.