The inactivation of human CYP2E1 by phenethyl isothiocyanate, a naturally occurring chemopreventive agent, and its oxidative bioactivation

Urinary odor molecules in the Otassha Study can distinguish patients with sarcopenia: A pilot study

AIM

To identify sarcopenia markers in urinary odor.

METHODS

We performed solid-phase microextraction from the headspace and gas chromatography-mass spectrometry analysis of urinary volatile organic compounds (VOCs) in 71 healthy individuals and 68 patients diagnosed with sarcopenia according to the Asian Working Group on Sarcopenia 2019 criteria. The mass-to-charge ratios (m/z) of 10 VOCs with a significant difference in the total ion chromatogram of 220 VOCs detected in this study were compared by U-test. To calculate the predictive values for sarcopenia, binomial logistic regression analyses were conducted with sarcopenia (0, 1) as the dependent variable and the m/z values of each of the 10 VOCs and all 10 VOCs as independent variables. Receiver operating characteristic (ROC) curves for predictive values were generated to evaluate diagnostic accuracy. The correlations between the predictive value and handgrip strength, usual gait speed, and skeletal muscle mass were assessed using Pearson's r.

RESULTS

We identified 10 VOCs (p-xylene, 1-butanol, d-limonene, nonanal, pyrrole, γ-butyrolactone, texanol isomer, octanoic acid, nonanoic acid, and diisobutyl phthalate) as candidate biomarkers in urine. The ROC curve analysis showed high diagnostic accuracy of the predictive values of the 10 VOCs for sarcopenia (area under the curve = 0.866, 95% confidence interval: 0.829-0.942; sensitivity, 80.9%; specificity, 81.7%). Additionally, the predictive values significantly correlated with handgrip strength (male: r = -0.505, P < 0.0001; female: r = -0.568, P < 0.0001).

CONCLUSIONS

This study identified 10 urinary VOCs as possible non-invasive biomarkers for sarcopenia, offering insights into its onset mechanism and potential therapeutic targets. Geriatr Gerontol Int 2025; 25: 307-315.

Nutritional Sources and Anticancer Potential of Phenethyl Isothiocyanate: Molecular Mechanisms and Therapeutic Insights

Phenethyl isothiocyanate (PEITC), a compound derived from cruciferous vegetables, has garnered attention for its anticancer properties. This review synthesizes existing research on PEITC, focusing on its mechanisms of action in combatting cancer. PEITC has been found to be effective against various cancer types, such as breast, prostate, lung, colon, and pancreatic cancers. Its anticancer activities are mediated through several mechanisms, including the induction of apoptosis (programmed cell death), inhibition of cell proliferation, suppression of angiogenesis (formation of new blood vessels that feed tumors), and reduction of metastasis (spread of cancer cells to new areas). PEITC targets crucial cellular signaling pathways involved in cancer progression, notably the Nuclear Factor kappa-light-chain-enhancer of activated B cells (NF-κB), Protein Kinase B (Akt), and Mitogen-Activated Protein Kinase (MAPK) pathways. These findings suggest PEITC's potential as a therapeutic agent against cancer. However, further research is necessary to determine the optimal dosage, understand its bioavailability, and assess potential side effects. This will be crucial for developing PEITC-based treatments that are both effective and safe for clinical use in cancer therapy.

Brassica-derived isothiocyanates as anticancer therapeutic agents and their nanodelivery

The isothiocyanates (ITCs) derived from the precursor glucosinolate molecules present in Brassica vegetables are bioactive organo-sulfur compounds with numerous pharmacologically important properties such as antioxidant, antiinflammatory, antimicrobial, and anticancer. Over the years, ITCs have been the focus of several research investigations associated with cancer treatment. Due to their potent chemo-preventive action, ITCs have been considered to be promising therapeutics for cancer therapy in place of the already existing conventional anticancer drugs. However, their wide spread use at the clinical stage is greatly restricted due to several factors such as low solubility in an aqueous medium, low bioavailability, low stability, and hormetic effect. To overcome these hindrances, nanotechnology can be exploited to develop nano-scale delivery systems that have the potential to enhance stability, and bioavailability and minimize the hermetic effect of ITCs.

Post-translational modifications of histone and non-histone proteins in epigenetic regulation and translational applications in alcohol-associated liver disease: Challenges and research opportunities

Epigenetic regulation is a process that takes place through adaptive cellular pathways influenced by environmental factors and metabolic changes to modulate gene activity with heritable phenotypic variations without altering the DNA sequences of many target genes. Epigenetic regulation can be facilitated by diverse mechanisms: many different types of post-translational modifications (PTMs) of histone and non-histone nuclear proteins, DNA methylation, altered levels of noncoding RNAs, incorporation of histone variants, nucleosomal positioning, chromatin remodeling, etc. These factors modulate chromatin structure and stability with or without the involvement of metabolic products, depending on the cellular context of target cells or environmental stimuli, such as intake of alcohol (ethanol) or Western-style high-fat diets. Alterations of epigenetics have been actively studied, since they are frequently associated with multiple disease states. Consequently, explorations of epigenetic regulation have recently shed light on the pathogenesis and progression of alcohol-associated disorders. In this review, we highlight the roles of various types of PTMs, including less-characterized modifications of nuclear histone and non-histone proteins, in the epigenetic regulation of alcohol-associated liver disease (ALD) and other disorders. We also describe challenges in characterizing specific PTMs and suggest future opportunities for basic and translational research to prevent or treat ALD and many other disease states.

A novel set of volatile urinary biomarkers for late-life major depressive and anxiety disorders upon the progression of frailty: a pilot study

Mood and anxiety disorders are frequent in the elderly and increase the risk of frailty. This study aimed to identify novel biomarkers of major depressive disorder (MDD) and anxiety in the elderly. We examined 639 participants in the community-dwelling Otassha Study (518 individuals considered healthy control, 77 with depression, anxiety, etc.), mean age 75 years, 58.4% of female. After exclusion criteria, we analyzed VOCs from 18 individuals (9 healthy control, 9 of MDD/agoraphobia case). Urinary volatile and semi-volatile organic compounds (VOCs) were profiled using solid-phase microextraction and gas chromatography-mass spectrometry. Six urinary VOCs differed in the absolute area of the base peak between participants with MDD and/or agoraphobia and controls. High area under the receiver-operating characteristic curve (AUC) values were found for phenethyl isothiocyanate (AUC: 0.86, p = 0.009), hexanoic acid (AUC: 0.85, p = 0.012), texanol (AUC: 0.99, p = 0.0005), and texanol isomer (AUC: 0.89, p = 0.005). The combined indices of dimethyl sulfone, phenethyl isothiocyanate, and hexanoic acid, and texanol and texanol isomer showed AUCs of 0.91 (p = 0.003) and 0.99 (p = 0.0005) and correlated with the GRID-HAMD and the Kihon Checklist (CL score), respectively. These VOCs may be valuable biomarkers for evaluating MDD and/or agoraphobia in the elderly.

Ellagic Acid Prevents Binge Alcohol-Induced Leaky Gut and Liver Injury through Inhibiting Gut Dysbiosis and Oxidative Stress

Alcoholic liver disease (ALD) is a major liver disease worldwide and can range from simple steatosis or inflammation to fibrosis/cirrhosis, possibly through leaky gut and systemic endotoxemia. Many patients with alcoholic steatohepatitis (ASH) die within 60 days after clinical diagnosis due to the lack of an approved drug, and thus, synthetic and/or dietary agents to prevent ASH and premature deaths are urgently needed. We recently reported that a pharmacologically high dose of pomegranate extract prevented binge alcohol-induced gut leakiness and hepatic inflammation by suppressing oxidative and nitrative stress. Herein, we investigate whether a dietary antioxidant ellagic acid (EA) contained in many fruits, including pomegranate and vegetables, can protect against binge alcohol-induced leaky gut, endotoxemia, and liver inflammation. Pretreatment with a physiologically-relevant dose of EA for 14 days significantly reduced the binge alcohol-induced gut barrier dysfunction, endotoxemia, and inflammatory liver injury in mice by inhibiting gut dysbiosis and the elevated oxidative stress and apoptosis marker proteins. Pretreatment with EA significantly prevented the decreased amounts of gut tight junction/adherent junction proteins and the elevated gut leakiness in alcohol-exposed mice. Taken together, our results suggest that EA could be used as a dietary supplement for alcoholic hepatitis patients.

Nanodelivery of natural isothiocyanates as a cancer therapeutic

Natural isothiocyanates (ITCs) are phytochemicals abundant in cruciferous vegetables with the general structure, R-NCS. They are bioactive organosulfur compounds derived from the hydrolysis of glucosinolates by myrosinase. A significant number of isothiocyanates have been isolated from different plant sources that include broccoli, Brussels sprouts, cabbage, cauliflower, kale, mustard, wasabi, and watercress. Several ITCs have been demonstrated to possess significant pharmacological properties including: antioxidant, anti-inflammatory, anti-cancer and antimicrobial activities. Due to their chemopreventive effects on many types of cancer, ITCs have been regarded as a promising anti-cancer therapeutic agent without major toxicity concerns. However, their clinical application has been hindered by several factors including their low aqueous solubility, low bioavailability, instability as well as their hormetic effect. Moreover, the typical dietary uptake of ITCs consumed for promotion of good health may be far from their bioactive (or cytotoxic) dose necessary for cancer prevention and/or treatment. Nanotechnology is one of best options to attain enhanced efficacy and minimize hormetic effect for ITCs. Nanoformulation of ITCs leads to enhance stability of ITCs in plasma and emphasize on their chemopreventive effects. This review provides a summary of the potential bioactivities of ITCs, their mechanisms of action for the prevention and treatment of cancer, as well as the recent research progress in their nanodelivery strategies to enhance solubility, bioavailability, and anti-cancer efficacy.

Advanced glycation end products (AGEs) and other adducts in aging-related diseases and alcohol-mediated tissue injury

Advanced glycation end products (AGEs) are potentially harmful and heterogeneous molecules derived from nonenzymatic glycation. The pathological implications of AGEs are ascribed to their ability to promote oxidative stress, inflammation, and apoptosis. Recent studies in basic and translational research have revealed the contributing roles of AGEs in the development and progression of various aging-related pathological conditions, such as diabetes, cardiovascular complications, gut microbiome-associated illnesses, liver or neurodegenerative diseases, and cancer. Excessive chronic and/or acute binge consumption of alcohol (ethanol), a widely consumed addictive substance, is known to cause more than 200 diseases, including alcohol use disorder (addiction), alcoholic liver disease, and brain damage. However, despite the considerable amount of research in this area, the underlying molecular mechanisms by which alcohol abuse causes cellular toxicity and organ damage remain to be further characterized. In this review, we first briefly describe the properties of AGEs: their formation, accumulation, and receptor interactions. We then focus on the causative functions of AGEs that impact various aging-related diseases. We also highlight the biological connection of AGE-alcohol-adduct formations to alcohol-mediated tissue injury. Finally, we describe the potential translational research opportunities for treatment of various AGE- and/or alcohol-related adduct-associated disorders according to the mechanistic insights presented.

Mechanisms Underlying Biological Effects of Cruciferous Glucosinolate-Derived Isothiocyanates/Indoles: A Focus on Metabolic Syndrome

An inverse correlation between vegetable consumption and the incidence of cancer has long been described. This protective effect is stronger when cruciferous vegetables are specifically consumed. The beneficial properties of vegetables are attributed to their bioactive components like fiber, antioxidants vitamins, antioxidants, minerals, and phenolic compounds. Cruciferous vegetables contain all these molecules; however, what makes them different are their sulfurous components, called glucosinolates, responsible for their special smell and taste. Glucosinolates are inactive biologically in the organism but are hydrolyzed by the enzyme myrosinase released as a result of chewing, leading to the formation of active derivatives such as isothiocyanates and indoles. A considerable number of in vitro and in vivo studies have reported that isothiocyanates and indoles elicit chemopreventive potency through multiple mechanisms that include modulation of phases I and II detoxification pathway enzymes, regulation of cell cycle arrest, and control of cell growth, induction of apoptosis, antioxidant activity, anti-angiogenic effects, and epigenetic regulation. Nuclear erythroid 2-related factor 2 (Nrf2) and Nuclear factor-κB (NF-κB) are key and central regulators in all these processes with a main role in oxidative stress and inflammation control. It has been described that isothiocyanates and indoles regulate their activity directly and indirectly. Today, the metabolic syndrome (central obesity, insulin resistance, hyperlipidemia, and hypertension) is responsible for a majority of deaths worldwide. All components of metabolic syndrome are characterized by chronic inflammation with deregulation of the PI3K/AKT/mTOR, MAPK/EKR/JNK, Nrf2, and NF-κB signaling pathways. The effects of GLSs derivatives controlling these pathways have been widely described in relation to cancer. Changes in food consumption patterns observed in the last decades to higher consumption of ultra-processed foods, with elevation in simple sugar and saturated fat contents and lower consumption of vegetables and fruits have been directly correlated with metabolic syndrome prevalence. In this review, it is summarized the knowledge regarding the mechanisms by which cruciferous glucosinolate derivatives (isothiocyanates and indoles) directly and indirectly regulate these pathways. However, the review places a special focus on the knowledge of the effects of glucosinolates derivatives in metabolic syndrome, since this has not been reviewed before.

Susceptibility to the acute toxicity of acrylonitrile in streptozotocin-induced diabetic rats: protective effect of phenethyl isothiocyanate, a phytochemical CYP2E1 inhibitor

Diabetes mellitus is a significant global public health issue. The diabetic state not only precipitates chronic disease but also has the potential to change the toxicity of drugs and chemicals. Acrylonitrile (AN) is a potent neurotoxin widely used in industrial products. This study used a streptozotocin (STZ)-induced diabetic rat model to examine the role of cytochrome P450 2E1 (CYP2E1) in acute AN toxicity. The protective effect of phenethyl isothiocyanate (PEITC), a phytochemical inhibitor of CYP2E1, was also investigated. A higher incidence of convulsions and loss of the righting reflex, and decreased rates of survival, as well as elevated CYP2E1 activity, were observed in diabetic rats treated with AN when compared to those in non-diabetic rats, suggesting that diabetes confers susceptibility to the acute toxicity of AN. Pretreatment with PEITC (20-80 mg/kg) followed by AN injection alleviated the acute toxicity of AN in diabetic rats as evidenced by the decreased incidence of convulsions and loss of righting reflex, and increased rates of survival. PEITC pretreatment at 40 and 80 mg/kg decreased hepatic CYP2E1 activity in AN-exposed diabetic rats. PEITC pretreatment (20 mg/kg) increased the glutathione (GSH) content and glutathione S-transferase (GST) activity and further decreased ROS levels in AN-exposed diabetic rats. Collectively, STZ-induced diabetic rats were more sensitive to AN-induced acute toxicity mainly due to CYP2E1 induction, and PEITC pretreatment significantly alleviated the acute toxicity of AN in STZ-induced diabetic rats. PEITC might be considered as a potential effective chemo-preventive agent against AN-induced acute toxicity in individuals with an underlying diabetic condition.

Comparing the protective effects of three sulfur compounds against acrylonitrile-induced acute toxicity in CYP2E1-induced rats

Cytochrome P450 2E1 (CYP2E1) can be induced by diabetes mellitus, nonalcoholic liver disease, and obesity. This study assessed the protective effects of three sulfur compounds, namely phenethyl isothiocyanate (PEITC), dimethyl trisulfide (DMTS), and sodium thiosulfate (STS), on acrylonitrile (ACN)-induced acute toxicity in rats enriched with CYP2E1. PEITC and DMTS were administered intragastrically (i.g.), whereas STS was injected intraperitoneally (i.p.) at an identical dose of 0.5 mmol/kg for 3 days in acetone-pretreated rats before ACN (90 mg/kg) injection (i.p.). Acetone-treated rats that expressed high levels of CYP2E1 were more susceptible to ACN-induced acute toxicity. The sulfur compounds reduced the rate of convulsions and loss of the righting reflex in acute ACN-exposed CYP2E1-induced rats; PEITC and DMTS also increased the survival rates. PEITC inhibited hepatic CYP2E1 activity and protected hepatic and cerebral cytochrome c oxidase (CcOx) activities in acute ACN-exposed CYP2E1-enriched rats; DMTS protected hepatic CcOx activity. DMTS attenuated ACN-induced oxidative injury by reducing malondialdehyde (MDA) levels and increasing glutathione content in the brain. STS only reduced cerebral MDA levels, whereas PEITC did not exhibit any antioxidant effects. Collectively, PEITC provided superior protective effects against ACN-induced acute toxicity in rats with increased CYP2E1 activity, followed by DMTS; STS provided limited effects. PEITC and DMTS might be considered as promising chemopreventive agents against ACN-induced acute toxicity in vulnerable subpopulations with increased CYP2E1 activity.

Apoptosis as a Mechanism of the Cancer Chemopreventive Activity of Glucosinolates: a Review

Cruciferous vegetables are a rich source of glucosinolates that have established anti-carcinogenic activity. Naturally-occurring glucosinolates and their derivative isothiocyanates (ITCs), generated as a result of their enzymatic degradation catalysed by myrosinase, have been linked to low cancer incidence in epidemiological studies, and in animal models isothiocyanates suppressed chemically-induced tumorigenesis. The prospective effect of isothiocyanates as anti-carcinogenic agent has been much explored as cytotoxic against wide array of cancer cell lines and being explored for the development of new anticancer drugs. However, the mechanisms of isothiocyanates in inducing apoptosis against tumor cell lines are still largely disregarded. A number of mechanisms are believed to be involved in the glucosinolate-induced suppression of carcinogenesis, including the induction of apoptosis, biotransformation of xenobiotic metabolism, oxidative stress, alteration of caspase activity, angiogenesis, histone deacytylation and cell cycle arrest. The molecular mechanisms through which isothiocyanates stimulate apoptosis in cancer cell lines have not so far been clearly defined. This review summarizes the underlying mechanisms through which isothiocyanates modify the apoptotic pathway leading to cell death.

Intersection of the Roles of Cytochrome P450 Enzymes with Xenobiotic and Endogenous Substrates: Relevance to Toxicity and Drug Interactions

Today much is known about cytochrome P450 (P450) enzymes and their catalytic specificity, but the range of reactions catalyzed by each still continues to surprise. Historically, P450s had been considered to be involved in either the metabolism of xenobiotics or endogenous chemicals, in the former case playing a generally protective role and in the latter case a defined physiological role. However, the line of demarcation is sometimes blurred. It is difficult to be completely specific in drug design, and some P450s involved in the metabolism of steroids and vitamins can be off-targets. In a number of cases, drugs have been developed that act on some of those P450s as primary targets, e.g., steroid aromatase inhibitors. Several of the P450s involved in the metabolism of endogenous substrates are less specific than once thought and oxidize several related structures. Some of the P450s that primarily oxidize endogenous chemicals have been shown to oxidize xenobiotic chemicals, even in a bioactivation mode.

Clinical Trial of 2-Phenethyl Isothiocyanate as an Inhibitor of Metabolic Activation of a Tobacco-Specific Lung Carcinogen in Cigarette Smokers

2-Phenethyl isothiocyanate (PEITC), a natural product found as a conjugate in watercress and other cruciferous vegetables, is an inhibitor of the metabolic activation and lung carcinogenicity of the tobacco carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in F344 rats and A/J mice. We carried out a clinical trial to determine whether PEITC also inhibits the metabolic activation of NNK in smokers. Cigarette smokers were recruited and asked to smoke cigarettes containing deuterium-labeled [pyridine-D4]NNK for an acclimation period of at least 1 week. Then subjects were randomly assigned to one of two arms: PEITC followed by placebo, or placebo followed by PEITC. During the 1-week treatment period, each subject took PEITC (10 mg in 1 mL of olive oil, 4 times per day). There was a 1-week washout period between the PEITC and placebo periods. The NNK metabolic activation ratio [pyridine-D4]hydroxy acid/total [pyridine-D4]NNAL was measured in urine samples to test the hypothesis that PEITC treatment modified NNK metabolism. Eighty-two smokers completed the study and were included in the analysis. Overall, the NNK metabolic activation ratio was reduced by 7.7% with PEITC treatment (P = 0.023). The results of this trial, while modest in effect size, provide a basis for further investigation of PEITC as an inhibitor of lung carcinogenesis by NNK in smokers. Cancer Prev Res; 9(5); 396-405. ©2016 AACR.

Mechanisms of the Anticancer Effects of Isothiocyanates

Cancer results from aberrant signaling pathways that result in uncontrolled cellular proliferation. The epidemiological studies have shown a strong inverse correlation between dietary consumption of cruciferous vegetables and incidences of cancer. Isothiocyanates (ITCs) are present in cruciferous vegetables like broccoli, cabbage, watercress, etc. and are identified as the major active constituents. Several mechanistic studies have demonstrated chemopreventive and chemotherapeutic activity of ITCs against various tumor types. ITCs exert anticancer activity by suppressing various critical hallmarks of cancer like cellular proliferation, angiogenesis, apoptosis, metastasis, etc., in vitro as well as in preclinical animal model. ITCs also generate reactive oxygen species to induce apoptosis in cancer cells. Due to promising preclinical results, few ITCs have also advanced to clinical trials. This chapter provides a candid review on the chemopreventive and chemotherapeutic activity of various major ITCs.

A principal mechanism for the cancer chemopreventive activity of phenethyl isothiocyanate is modulation of carcinogen metabolism

Isothiocyanates are small molecules characterized by high chemical reactivity that allows them to interact readily with cellular constituents eliciting a plethora of biological activities. They are present exclusively in cruciferous vegetables, as glucosinolates, the intake of which has been associated with cancer chemoprevention. When the physical structure of these vegetables is disturbed, e.g. during mastication, the enzyme myrosinase is released and converts the glucosinolates to isothiocyanates (R-N=C=S), where R can be aliphatic or aromatic. Although sulforaphane, an aliphatic isothiocyanate, has received most attention worldwide, the most extensively studied aromatic isothiocyanate is phenethyl isothiocyanate (PEITC), and there are substantial differences in biological activity between the two sub-classes. In animal cancer models, PEITC effectively antagonized the carcinogenicity of chemicals, especially nitrosocompounds. A principal mechanism of their action is to protect the integrity of DNA by decreasing the levels of the genotoxic metabolites of chemical carcinogens. Extensive studies established that PEITC modulates the metabolism of the tobacco-specific carcinogenic nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) by inhibiting its cytochrome P450-mediated bioactivation. Moreover, PEITC is a potent inducer of detoxification enzymes such as quinone reductase, glutathione S-transferase and glucuronosyl transferase. PEITC is rapidly absorbed and is characterized by a large bioavailability; Cmax concentrations achieved in plasma after dietary intake are sufficient to modulate carcinogen metabolism. PEITC is primarily metabolized by glutathione conjugation and is excreted in the urine and bile as the mercapturate. The ability of PEITC to perturb carcinogen metabolism through modulation of cytochrome P450 and phase II detoxification enzymes is comprehensively and critically reviewed.

Translational Implications of the Alcohol-Metabolizing Enzymes, Including Cytochrome P450-2E1, in Alcoholic and Nonalcoholic Liver Disease

Fat accumulation (hepatic steatosis) in alcoholic and nonalcoholic fatty liver disease is a potentially pathologic condition which can progress to steatohepatitis (inflammation), fibrosis, cirrhosis, and carcinogenesis. Many clinically used drugs or some alternative medicine compounds are also known to cause drug-induced liver injury, which can further lead to fulminant liver failure and acute deaths in extreme cases. During liver disease process, certain cytochromes P450 such as the ethanol-inducible cytochrome P450-2E1 (CYP2E1) and CYP4A isozymes can be induced and/or activated by alcohol and/or high-fat diets and pathophysiological conditions such as fasting, obesity, and diabetes. Activation of these P450 isozymes, involved in the metabolism of ethanol, fatty acids, and various drugs, can produce reactive oxygen/nitrogen species directly and/or indirectly, contributing to oxidative modifications of DNA/RNA, proteins and lipids. In addition, aldehyde dehydrogenases including the mitochondrial low Km aldehyde dehydrogenase-2 (ALDH2), responsible for the metabolism of acetaldehyde and lipid aldehydes, can be inactivated by various hepatotoxic agents. These highly reactive acetaldehyde and lipid peroxides, accumulated due to ALDH2 suppression, can interact with cellular macromolecules DNA/RNA, lipids, and proteins, leading to suppression of their normal function, contributing to DNA mutations, endoplasmic reticulum stress, mitochondrial dysfunction, steatosis, and cell death. In this chapter, we specifically review the roles of the alcohol-metabolizing enzymes including the alcohol dehydrogenase, ALDH2, CYP2E1, and other enzymes in promoting liver disease. We also discuss translational research opportunities with natural and/or synthetic antioxidants, which can prevent or delay the onset of inflammation and liver disease.

Phenethyl isothiocyanate: a comprehensive review of anti-cancer mechanisms

The epidemiological evidence suggests a strong inverse relationship between dietary intake of cruciferous vegetables and the incidence of cancer. Among other constituents of cruciferous vegetables, isothiocyanates (ITC) are the main bioactive chemicals present. Phenethyl isothiocyanate (PEITC) is present as gluconasturtiin in many cruciferous vegetables with remarkable anti-cancer effects. PEITC is known to not only prevent the initiation phase of carcinogenesis process but also to inhibit the progression of tumorigenesis. PEITC targets multiple proteins to suppress various cancer-promoting mechanisms such as cell proliferation, progression and metastasis. Pre-clinical evidence suggests that combination of PEITC with conventional anti-cancer agents is also highly effective in improving overall efficacy. Based on accumulating evidence, PEITC appears to be a promising agent for cancer therapy and is already under clinical trials for leukemia and lung cancer. This is the first review which provides a comprehensive analysis of known targets and mechanisms along with a critical evaluation of PEITC as a future anti-cancer agent.

Glycogen synthase kinase 3 regulates cell death and survival signaling in tumor cells under redox stress

Targeting tumor-specific metabolic adaptations is a promising anticancer strategy when tumor defense mechanisms are restrained. Here, we show that redox-modulating drugs including the retinoid N-(4-hydroxyphenyl)retinamide (4HPR), the synthetic triterpenoid bardoxolone (2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid methyl ester), arsenic trioxide (As2O3), and phenylethyl isothiocyanate (PEITC), while affecting tumor cell viability, induce sustained Ser9 phosphorylation of the multifunctional kinase glycogen synthase kinase 3β (GSK3β). The antioxidant N-acetylcysteine decreased GSK3β phosphorylation and poly(ADP-ribose) polymerase cleavage induced by 4HPR, As2O3, and PEITC, implicating oxidative stress in these effects. GSK3β phosphorylation was associated with up-regulation of antioxidant enzymes, in particular heme oxygenase-1 (HO-1), and transient elevation of intracellular glutathione (GSH) in cells surviving acute stress, before occurrence of irreversible damage and death. Genetic inactivation of GSK3β or transfection with the non-phosphorylatable GSK3β-S9A mutant inhibited HO-1 induction under redox stress, while tumor cells resistant to 4HPR exhibited increased GSK3β phosphorylation, HO-1 expression, and GSH levels. The above-listed findings are consistent with a role for sustained GSK3β phosphorylation in a signaling network activating antioxidant effector mechanisms during oxidoreductive stress. These data underlie the importance of combination regimens of antitumor redox drugs with inhibitors of survival signaling to improve control of tumor development and progression and overcome chemoresistance.

Molecular targets of isothiocyanates in cancer: recent advances

Cancer is a multistep process resulting in uncontrolled cell division. It results from aberrant signaling pathways that lead to uninhibited cell division and growth. Various recent epidemiological studies have indicated that consumption of cruciferous vegetables, such as garden cress, broccoli, etc., reduces the risk of cancer. Isothiocyanates (ITCs) have been identified as major active constituents of cruciferous vegetables. ITCs occur in plants as glucosinolate and can readily be derived by hydrolysis. Numerous mechanistic studies have demonstrated the anticancer effects of ITCs in various cancer types. ITCs suppress tumor growth by generating reactive oxygen species or by inducing cycle arrest leading to apoptosis. Based on the exciting outcomes of preclinical studies, few ITCs have advanced to the clinical phase. Available data from preclinical as well as available clinical studies suggest ITCs to be one of the promising anticancer agents available from natural sources. This is an up-to-date exhaustive review on the preventive and therapeutic effects of ITCs in cancer.