Effect of organic isothiocyanates on the P-glycoprotein- and MRP1-mediated transport of daunomycin and vinblastine

Nano Strategies for Artemisinin Derivatives to Enhance Reverse Efficiency of Multidrug Resistance in Breast Cancer

Artemisinin (ART) has been found to exert anti-tumor activity by regulating the cell cycle, inducing apoptosis, inhibiting angiogenesis and tumor invasion and metastasis. Its derivatives (ARTs) can regulate the expression of drug-resistant proteins and reverse the multidrug resistance (MDR) of tumor cells by inhibiting intracellular drug efflux, inducing apoptosis and autophagy of tumor cells, thus enhancing the sensitivity of tumor cells to chemotherapy and radiotherapy. Recent studies have shown that nanodrugs play an important role in the diagnosis and treatment of cancer, which can effectively solve the shortcomings of poor hydrophilicity and low bioavailability of ARTs in the human body, prolong the in vivo circulation time, improve the targeting of drugs (including tumor tissues or specific organelles), and control the release of drugs in target tissues, thereby reducing the side effect. This review systematically summarized the latest research progress of nano-strategies of ARTs to enhance the efficiency of MDR reversal in breast cancer (BC) from the following two aspects: (1) Chemicals encapsulated in nanomaterials based on innovative anti-proliferation mechanism: non-ABC transporter receptor candidate related to ferroptosis (dihydroartemisinin/DHA analogs). (2) Combination therapy strategy of nanomedicine (drug-drug combination therapy, drug-gene combination, and chemical-physical therapy). Self-assembled nano-delivery systems enhance therapeutic efficacy through increased drug loading, rapid reactive release, optimized delivery sequence, and realization of cascade-increasing effects. New nanotechnology methods must be designed for specific delivery routines to achieve targeting administration and overcome MDR without affecting normal cells. The significance of this review is to expect that ART and ARTs can be widely used in clinical practice. In the future, nanotechnology can help people to treat multidrug resistance of breast cancer more accurately and efficiently.

Phenethyl Isothiocyanate Enhances the Cytotoxic Effects of PARP Inhibitors in High-Grade Serous Ovarian Cancer Cells

While PARP inhibitor (PARPi) therapies have shown promising results in the treatment of high-grade serous ovarian cancer (HGSOC) harboring homologous recombination deficiencies, primary resistance to PARPi frequently occurs and even initial responders may eventually become resistant. Therefore, the development of novel effective combinatorial strategies to treat HGSOC is urgently needed. Here, we report that H₂O₂-induced oxidative stress sensitized HGSOC cells to PARPi BMN 673. Furthermore, Phenethyl isothiocyanate (PEITC) as a ROS-inducing agent significantly enhanced the cytotoxic effects of BMN 673. Mechanistically, combined use of PEITC and BMN 673 resulted in ROS overproduction and accumulation, enhanced DNA damage, G2/M arrest and apoptosis, all of which were significantly reversed by the ROS scavenger N-Acetyl-L-cysteine. We also showed that while PEITC did not further enhance the ability of BMN 673 on PARP1 trapping in HGSOC cells, the therapeutic effects of the PEITC/BMN 673 combination were at least in part dependent on the presence of PARP1. Importantly, the PEITC/BMN 673 combination potently abrogated the growth of HGSOC tumor spheroids and patient-derived organoid models of HGSOC and cervical cancer. Our findings provide a basis for further investigation of the utility of PARPi combination regimen in HGSOC and cervical cancer through ROS-mediated mechanisms.

Metabolic and biotransformation effects on dietary glucosinolates, their bioavailability, catabolism and biological effects in different organisms

Glucosinolate-producing plants have long been recognized for both their distinctive benefits to human nutrition and their resistance traits against pathogens and herbivores. Despite the accumulation of glucosinolates (GLS) in plants is associated with their resistance to various biotic and abiotic stresses, the defensive and biological activities of GLS are commonly conveyed by their metabolic products. In view of this, metabolism is considered the driving factor upon the interactions of GLS-producing plants with other organisms, also influenced by plant and plant attacking or digesting organism characteristics. Several microbial pathogens and insects have evolved the capacity to detoxify GLS-hydrolysis products or inhibit their formation via different means, highlighting the relevance of their metabolic abilities for the plants' defense system activation and target organism detoxification. Strikingly, some bacteria, fungi and insects can likewise produce their own myrosinase (MYR)-like enzymes in one of the most important adaptation strategies against the GLS-MYR plant defense system. Knowledge of GLS metabolic pathways in herbivores and pathogens can impact plant protection efforts and may be harnessed upon for genetically modified plants that are more resistant to predators. In humans, the interest in the implementation of GLS in diets for the prevention of chronic diseases has grown substantially. However, the efficiency of such approaches is dependent on GLS bioavailability and metabolism, which largely involves the human gut microbiome. Among GLS-hydrolytic products, isothiocyanates (ITC) have shown exceptional properties as chemical plant defense agents against herbivores and pathogens, along with their health-promoting benefits in humans, at least if consumed in reasonable amounts. Deciphering GLS metabolic pathways provides critical information for catalyzing all types of GLS towards the generation of ITCs as the biologically most active metabolites. This review provides an overview on contrasting metabolic pathways in plants, bacteria, fungi, insects and humans towards GLS activation or detoxification. Further, suggestions for the preparation of GLS containing plants with improved health benefits are presented.

Brassica Nigra: Ethopharmacological Review of a Routinely Used Condiment

BACKGROUND

Brassica nigra belonging to the family Brassicaceae (syn - black mustard) comprises of dried seeds and is widely cultivated in Mediterranean region and various other countries like India and Europe. The Plant is neither reported in any official book nor reported systematically for pharmacological effects.

METHODS

We undertook a structured search of all the official books including pharmacopoeias and ayurvedic textbooks. The data was collected, sorted and compiled to bring the chemical constituents and uses of B. nigra.

RESULTS

B. nigra contains glycosinolates which undergoes hydrolysis in the presence of myrosinase enzyme yields allyl isothiocyante. The bitter taste and pungent odor is due to the isothiocyanates. B. Nigra shows various activities that are medically important such as anticancer, anti-bacterial, antifungal, anti-helminthic, protection against renal and hepatic toxicity and can also be used in diabetes treatment. Black mustards are also used in cardiovascular and neurological disorders.

CONCLUSION

The present review explores the historical background including the macroscopic and microscopic characteristics, chemical constituents, pharmacological action, various evaluation parameters, formulations and uses of black mustard.

Mustard Seed (Brassica nigra) Extract Exhibits Antiproliferative Effect against Human Lung Cancer Cells through Differential Regulation of Apoptosis, Cell Cycle, Migration, and Invasion

Lung cancer is the primary cause of cancer-related death worldwide, and development of novel lung cancer preventive and therapeutic agents are urgently needed. Brassica nigra (black mustard) seeds are commonly consumed in several Asian and African countries. Mustard seeds previously exhibited significant anticancer activities against several cancer types. In the present study, we have investigated various cellular and molecular mechanisms of anticancer effects of an ethanolic extract of B. nigra seeds against A549 and H1299 human non-small cell lung cancer cell lines. B. nigra extract showed a substantial growth-inhibitory effect as it reduced the viability and clonogenic survival of A549 and H1299 cells in a concentration-dependent manner. B. nigra extract induced cellular apoptosis in a time- and concentration-dependent fashion as evidenced from increased caspase-3 activity. Furthermore, treatment of both A549 and H1299 cells with B. nigra extract alone or in combination with camptothecin induced DNA double-strand breaks as evidenced by upregulation of γH2A histone family member X, Fanconi anemia group D2 protein, Fanconi anemia group J protein, ataxia-telangiectesia mutated and Rad3-related protein. Based on cell cycle analysis, B. nigra extract significantly arrested A549 and H1299 cells at S and G2/M phases. Additionally, B. nigra extract suppressed the migratory and invasive properties of both cell lines, downregulated the expression of matrix metalloproteinase-2 (MMP2), MMP9, and Snail and upregulated the expression of E-cadherin at mRNA and protein levels. Taken together, these findings indicate that B. nigra seed extract may have an important anticancer potential against human lung cancer which could be mediated through simultaneous and differential regulation of proliferation, apoptosis, DNA damage, cell cycle, migration, and invasion.

Glucosinolate-Degradation Products as Co-Adjuvant Therapy on Prostate Cancer in Vitro

Glucosinolate-degradation products (GS-degradation products) are believed to be responsible for the anticancer effects of cruciferous vegetables. Furthermore, they could improve the efficacy and reduce side-effects of chemotherapy. The aim of the present study was to determine the cytotoxic effects of GS-degradation products on androgen-insensitive human prostate cancer (AIPC) PC-3 and DU 145 cells and investigate their ability to sensitize such cells to chemotherapeutic drug Docetaxel (DOCE). Cells were cultured under growing concentrations of allyl-isothiocyanate (AITC), sulforaphane (SFN), 4-pentenyl-isothiocyanate (4PI), iberin (IB), indole-3-carbinol (I3C), or phenethyl-isothiocyanate (PEITC) in absence or presence of DOCE. The anti-tumor effects of these compounds were analyzed using the trypan blue exclusion, apoptosis, invasion and RT-qPCR assays and confocal microscopy. We observed that AITC, SFN, IB, and/or PEITC induced a dose- and time-dependent cytotoxic effect on PC-3 and DU 145 cells, which was mediated, at least, by apoptosis and cell cycle arrest. Likewise, we showed that these GS-degradation products sensitized both cell lines to DOCE by synergic mechanisms. Taken together, our results indicate that GS-degradation products can be promising compounds as co-adjuvant therapy in prostate cancer.

Overcoming transporter-mediated multidrug resistance in cancer: failures and achievements of the last decades

Multidrug resistance (MDR) is a complex phenomenon caused by numerous reasons in cancer chemotherapy. It is related to the abnormal tumor metabolism, precisely increased glycolysis and lactic acid production, extracellular acidification, and drug efflux caused by transport proteins. There are few strategies to increase drug delivery into cancer cells. One of them is the inhibition of carbonic anhydrases or certain proton transporters that increase extracellular acidity by proton extrusion from the cells. This prevents weakly basic chemotherapeutic drugs from ionization and increases their penetration through the cancer cell membrane. Another approach is the inhibition of MDR proteins that pump the anticancer agents into the extracellular milieu and decrease their intracellular concentration. Physical methods, such as ultrasound-mediated sonoporation, are being developed, as well. To increase the efficacy of sonoporation, various microbubbles are used. Ultrasound causes microbubble cavitation, i.e., periodical pulsation of the microbubble, and destruction which results in formation of temporary pores in the cellular membrane and increased permeabilization to drug molecules. This review summarizes the main approaches to reverse MDR related to the drug penetration along with its applications in preclinical and clinical studies.

Advances in molecular signaling mechanisms of β-phenethyl isothiocyanate antitumor effects

β-Phenethyl isothiocyanate (PEITC) is an important phytochemical from cruciferous vegetables and is being evaluated for chemotherapeutic activity in early phase clinical trials. Moreover, studies in cell culture and in animals found that the anticarcinogenic activities of PEITC involved all the major stages of tumor growth: initiation, promotion, and progression. A number of mechanisms have been proposed for the chemopreventive activities of this compound. Here, we focus on the major molecular signaling pathways for the anticancer activities of PEITC. These include (1) activation of apoptosis pathways; (2) induction of cell cycle arrest; and (3) inhibition of the survival pathways. Furthermore, we also discussed the regulation of drug-metabolizing enzymes, including cytochrome P450s, metabolizing enzymes, and multidrug resistance.

Cruciferous vegetables, isothiocyanates, and prevention of bladder cancer

Approximately 80% of human bladder cancers (BC) are non-muscle invasive when first diagnosed and are usually treated by transurethral tumor resection. But 50-80% of patients experience cancer recurrence. Agents for prevention of primary BC have yet to be identified. Existing prophylactics against BC recurrence, e.g., Bacillus Calmette-Guerin (BCG), have limited efficacy and utility; they engender significant side effects and require urethral catheterization. Many cruciferous vegetables, rich sources of isothiocyanates (ITCs), are commonly consumed by humans. Many ITCs possess promising chemopreventive activities against BC and its recurrence. Moreover, orally ingested ITCs are selectively delivered to bladder via urinary excretion. This review is focused on urinary delivery of ITCs to the bladder, their cellular uptake, their chemopreventive activities in preclinical and epidemiological studies that are particularly relevant to prevention of BC recurrence and progression, and their chemopreventive mechanisms in BC cells and tissues.

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.

Exploring the effects of isothiocyanates on chemotherapeutic drugs

INTRODUCTION

Chemoprevention has emerged as a promising strategy to reduce the risk and to control cancer. In this context, isothiocyanates (ITCs), found in abundance in the form of glucosinolates in cruciferous vegetables, have gained increasing consideration for their chemopreventive activity. ITCs exert their effects mainly by inducing carcinogen metabolism or by inhibiting tumor cell proliferation.

AREAS COVERED

In recent years, novel combination treatments, by coupling chemopreventive agents and typical chemotherapeutics, have been exploited to increase the antitumor activities. The aim of this article is to examine the foremost studies carried out, so far, on the effects of dietary and synthetic ITCs on different signaling pathways involved in the pharmacokinetics and pharmacodynamics of chemotherapeutic agents, in order to enhance their effectiveness.

EXPERT OPINION

Undoubtedly, the beneficial anticarcinogenic potential of ITCs, both singly and in combination, has emerged in in vitro and in vivo studies. However, only a few clinical trials have been carried out so far with ITCs, which try to better define both the pharmacokinetic and pharmacodynamic impacts in humans. More toxicological evaluations after long-term administration of ITCs in different species are required for the clinical development of ITCs as anticarcinogenic agents.

Chemopreventive and anti-angiogenic effects of dietary phenethyl isothiocyanate in an N-methyl nitrosourea-induced breast cancer animal model

The effect of phenethyl isothiocyanate (PEITC), a component of cruciferous vegetables, on the initiation and progression of cancer was investigated in a chemically induced estrogen-dependent breast cancer model. Breast cancer was induced in female Sprague Dawley rats (8 weeks old) by the administration of N-methyl nitrosourea (NMU). Animals were administered 50 or 150 µmol/kg oral PEITC and monitored for tumor appearance for 18 weeks. The PEITC treatment prolonged the tumor-free survival time and decreased the tumor incidence and multiplicity. The time to the first palpable tumor was prolonged from 69 days in the control, to 84 and 88 days in the 50 and 150 µmol/kg PEITC-treated groups. The tumor incidence in the control, 50 µmol/kg, and 150 µmol/kg PEITC-treated groups was 56.6%, 25.0% and 17.2%, while the tumor multiplicity was 1.03, 0.25 and 0.21, respectively. Differences were statistically significant (p < 0.05) from the control, but there were no significant differences between the two dose levels. The intratumoral capillary density decreased from 4.21 ± 0.30 vessels per field in the controls to 2.46 ± 0.25 in the 50 µmol/kg and 2.36 ± 0.23 in the 150 µmol/kg PEITC-treated animals. These studies indicate that supplementation with PEITC prolongs the tumor-free survival, reduces tumor incidence and burden, and is chemoprotective in NMU-induced estrogen-dependent breast cancer in rats. For the first time, it is reported that PEITC has anti-angiogenic effects in a chemically induced breast cancer animal model, representing a potentially significant mechanism contributing to its chemopreventive activity.

Engineering glucosinolates in plants: current knowledge and potential uses

Glucosinolates (GSL) and their derivatives are well known for the characteristic roles they play in plant defense as signaling molecules and as bioactive compounds for human health. More than 130 GSLs have been reported so far, and most of them belong to the Brassicaceae family. Several enzymes and transcription factors involved in the GSL biosynthesis have been studied in the model plant, Arabidopsis, and in a few other Brassica crop species. Recent studies in GSL research have defined the regulation, distribution, and degradation of GSL biosynthetic pathways; however, the underlying mechanism behind transportation of GSLs in plants is still largely unknown. This review highlights the recent advances in the metabolic engineering of GSLs in plants and discusses their potential applications.

Cancer chemoprevention with dietary isothiocyanates mature for clinical translational research

Inverse association between dietary intake of cruciferous vegetables and cancer risk observed in population-based case-control studies is partly attributable to structurally simple but mechanistically complex phytochemicals with an isothiocyanate (-N=C=S) functional group. Cancer protective role for dietary isothiocyanates (ITCs) is substantiated by preclinical studies in rodent models. A common feature of many naturally occurring ITCs relates to their ability to cause growth arrest and cell death selectively in cancer cells. At the same time, evidence continues to accumulate to suggest that even subtle change in chemical structure of the ITCs can have a profound effect on their activity and mechanism of action. Existing mechanistic paradigm stipulates that ITCs may not only prevent cancer initiation by altering carcinogen metabolism but also inhibit post-initiation cancer development by suppressing many processes relevant to tumor progression, including cellular proliferation, neoangiogenesis, epithelial-mesenchymal transition, and self-renewal of cancer stem cells. Moreover, the ITCs are known to suppress diverse oncogenic signaling pathways often hyperactive in human cancers (e.g. nuclear factor-κB, hormone receptors, signal transducer and activator of transcription 3) to elicit cancer chemopreventive response. However, more recent studies highlight potential adverse effect of Notch activation by ITCs on their ability to inhibit migration of cancer cells. Mechanisms underlying ITC-mediated modulation of carcinogen metabolism, growth arrest, and cell death have been reviewed extensively. This article provides a perspective on bench-cage-bedside evidence supporting cancer chemopreventive role for some of the most promising ITCs. Structure-activity relationship and mechanistic complexity in the context of cancer chemoprevention with ITCs is also highlighted.

Natural isothiocyanates: genotoxic potential versus chemoprevention

Isothiocyanates, occurring in many dietary cruciferous vegetables, show interesting chemopreventive activities against several chronic-degenerative diseases, including cancer, cardiovascular diseases, neurodegeneration, diabetes. The electrophilic carbon residue in the isothiocyanate moiety reacts with biological nucleophiles and modification of proteins is recognized as a key mechanism underlying the biological activity of isothiocyanates. The nuclear factor-erythroid-2-related factor 2 system, which orchestrates the expression of a wide array of antioxidant genes, plays a role in the protective effect of isothiocyanates against almost all the pathological conditions reported above. Recent emerging findings suggest a further common mechanism. Chronic inflammation plays a central role in many human diseases and isothiocyanates inhibit the activity of many inflammation components, suppress cyclooxygenase 2, and irreversibly inactivate the macrophage migration inhibitory factor. Due to their electrophilic reactivity, some isothiocyanates are able to form adducts with DNA and induce gene mutations and chromosomal aberrations. DNA damage has been demonstrated to be involved in the pathogenesis of various chronic-degenerative diseases of epidemiological relevance. Thus, the genotoxicity of the isothiocyanates should be carefully considered. In addition, the dose-response relationship for genotoxic compounds does not suggest evidence of a threshold. Thus, chemicals that are genotoxic pose a greater potential risk to humans than non-genotoxic compounds. Dietary consumption levels of isothiocyanates appear to be several orders of magnitude lower than the doses used in the genotoxicity studies and thus it is highly unlikely that such toxicities would occur in humans. However, the beneficial properties of isothiocyanates stimulated an increase of dietary supplements and functional foods with highly enriched isothiocyanate concentrations on the market. Whether such concentrations may exert a potential health risk cannot be excluded with certainty and an accurate evaluation of the toxicological profile of isothiocyanates should be prompted before any major increase in their consumption be recommended or their clinical use suggested.

The molecular basis that unifies the metabolism, cellular uptake and chemopreventive activities of dietary isothiocyanates

Organic isothiocyanates (ITCs), which are characterized by the presence of an -N=C=S group, are among the most extensively studied cancer chemopreventive agents and show highly promising chemopreventive activities. Numerous studies have shown that ITCs can inhibit both carcinogenesis and cancer growth in a variety of animal models. Many cruciferous vegetables, which are commonly consumed by humans, are rich sources of these compounds. Of particular interest are their high bioavailability, their shared metabolic profile and their ability to target a wide array of cancer-related cellular proteins. This review is focused on discussing the molecular basis of these intriguing properties of ITCs, with a particular emphasis on the concept that cellular uptake and metabolism of ITCs and at least some of their major chemopreventive activities are all initiated through direct reaction of the carbon atom of the -N=C=S group of the ITCs with cysteine sulfhydryl groups of glutathione (GSH) and of proteins. This knowledge deepens our understanding about the biological activities of ITCs and may facilitate further research and development of these compounds for cancer prevention and treatment.

Proteins as binding targets of isothiocyanates in cancer prevention

Isothiocyanates are versatile cancer-preventive compounds. Evidence from animal studies indicates that the anticarcinogenic activities of ITCs involve all the major stages of tumor growth: initiation, promotion and progression. Epidemiological studies have also shown that dietary intake of ITCs is associated with reduced risk of certain human cancers. A number of mechanisms have been proposed for the chemopreventive activities of ITCs. To identify the molecular targets of ITCs is a first step to understand the molecular mechanisms of ITCs. Studies in recent years have shown that the covalent binding to certain protein targets by ITCs seems to play an important role in ITC-induced apoptosis and cell growth inhibition and other cellular effects. The knowledge gained from these studies may be used to guide future design and screen of better and more efficacious compounds. In this review, we intend to cover all potential protein targets of ITCs so far studied and summarize what are known about their binding sites and the potential biological consequences. In the end, we also offer discussions to shed light onto the relationship between protein binding and reactive oxygen species generation by ITCs.

Interactions of dietary phytochemicals with ABC transporters: possible implications for drug disposition and multidrug resistance in cancer

Common foods, such as fruits and vegetables, contain a large variety of secondary metabolites known as phytochemicals, many of which have been associated with health benefits. However, there is a limited knowledge of the processes by which these, mainly charged, phytochemicals (and/or their metabolites) are absorbed into the body, reach their biological target, and how they are eliminated. Recent studies have indicated that some of these phytochemicals are substrates and modulators of specific members of the superfamily of ABC transporting proteins. In this review, we present the reported interactions between the different classes of phytochemicals and ABC transporters and the mechanism by which they modulate the activity of these transporters. We also discuss the implications that such interactions may have on the pharmacokinetics of xenobiotics and the possible role of phytochemicals in the reversal of multidrug resistance in cancer chemotherapy.

Description of the cytotoxic effect of a novel drug Abietyl-Isothiocyanate on endometrial cancer cell lines

The objective of the present study was to determine the in-vitro effect of Abietyl-Isothiocyanate (ABITC), a representative of a new class of anti-cancer drugs, on endometrial cancer (EC) cell lines. ABITC at concentrations ≥1 μM displayed dose-dependent and selective cytotoxicity to EC cell lines (ECC-1, AN3CA, RL95-2) in comparison to other cancer cell lines. After treatment with ABITC, ECC-1 unlike control cells displayed hallmark features of apoptosis including chromatin condensation and nuclear fragmentation. At concentrations below the IC50, ABITC exerted anti-proliferative effects by blocking cell-cycle progression through G0/G1 and S-phase. In addition, cells attempted to counteract drug treatment by pro-survival signaling such as deactivation of JNK/SAPK and p38 MAPK and activation of AKT and ErK1/2. ABITC also altered EGF-receptor phosphorylation. At a concentration of 5 μM ABITC generated an excess amount of reactive oxygen species (ROS) and displayed pro-apoptotic signaling such as activation of caspase-8, JNK-SAPK and deactivation of PARP-1. Co-treatment with an antioxidant blocked the drug effects by reducing ROS generation, cytotoxicity and pro-apoptotic signaling. In summary, novel isothiocyanate ABITC is an anti-proliferative and selectively cytotoxic drug to EC cells in-vitro. Key mechanisms during cell death are predominantly correlated to excess generation of ROS. We suggest the further development of ABITC as a potential therapeutic by studying the drug efficacy in EC in-vivo models.

Dietary regulation of P-gp function and expression

Food-drug interactions have been associated with clinically important pharmacokinetic and pharmacodynamic changes of a drug. The aim of this paper is to review the regulation of P-glycoprotein (P-gp) by dietary components and to correlate the changes in cellular P-gp function and expression with drug bioavailability. In summary, the published literature has provided extensive data supporting the modulation of drug bioavailability through P-gp regulation by components in food groups such as fruit juices, spices, herbs, cruciferous vegetables and green tea. Most of these data were, however, derived from in vitro cell models and, except for the St John's wort, the clinical significance of most reported interactions remains to be clarified. Studies on piperine and capsaicin have underscored an often poor correlation between in vivo and in vitro data, whereas experiments involving curcumin highlighted differences between acute and chronic consumption of a dietary component on P-gp function and expression in vivo. A better understanding of the pharmacokinetic and pharmacodynamic profiles of the dietary components will aid in addressing these knowledge gaps.

ABC transporters and isothiocyanates: potential for pharmacokinetic diet-drug interactions

Isothiocyanates, a class of anti-cancer agents, are derived from cruciferous vegetables such as broccoli, cabbage and watercress, and have demonstrated chemopreventive activity in a number of cancer models and epidemiologic studies. Due to public interest in cancer prevention and alternative therapies in cancer, the consumption of herbal supplements and vegetables containing these compounds is widespread and increasing. Isothiocyanates interact with ATP-binding cassette (ABC) efflux transporters such as P-glycoprotein, MRP1, MRP2 and BCRP, and may influence the pharmacokinetics of substrates of these transporters. This review discusses the pharmacokinetic properties of isothiocyanates, their interactions with ABC transporters, and presents some data describing the potential for isothiocyanate-mediated diet-drug interactions.

Pancreatic cancer stem cells: fact or fiction?

The terms cancer-initiating or cancer stem cells have been the subject of great interest in recent years. In this review we will use pancreatic cancer as an overall theme to draw parallels with historical findings to compare to recent reports of stem-like characteristics in pancreatic cancer. We will cover such topics as label-retaining cells (side-population), ABC transporter pumps, telomerase, quiescence, cell surface stem cell markers, and epithelial-mesenchymal transitions. Finally we will integrate the available findings into a pancreatic stem cell model that also includes metastatic disease.

Sulforaphane and erucin increase MRP1 and MRP2 in human carcinoma cell lines

Multidrug resistance (MDR) transporters have been termed the Phase III detoxification system because they not only export endogenous metabolites but provide protection from xenobiotic insult by actively secreting foreign compounds and their metabolites from tissues. However, MDR overexpression in tumors can lead to drug resistance, a major obstacle in the treatment of many cancers, including lung cancer. Isothiocyanates from cruciferous vegetables, such as sulforaphane (SF) and erucin (ER), are known to enhance the expression of Phase II detoxification enzymes. Here we evaluated the ability of SF and ER to modulate MDR mRNA and protein expressions, as well as transporter activity. The expression of P-glycoprotein (P-gp), multidrug resistance protein 1 (MRP1) and multidrug resistance protein 2 (MRP2) in liver (HepG2), colon (Caco-2) and lung (A549) cancer cells treated with ER or SF was analyzed by Western blotting. Neither SF nor ER affected P-gp expression in any of the cell lines tested. Both SF and ER increased the protein levels of MRP1 and MRP2 in HepG2 cells and of MRP2 in Caco-2 cells in a dose-dependent manner. In A549 lung cancer cells, SF increased MRP1 and MRP2 mRNA and protein levels; ER caused a similar yet smaller increase in MRP1 and MRP2 mRNA. In addition, SF and ER increased MRP1-dependent efflux of 5-carboxyfluorescein diacetate in A549 cells, although again the effect of SF was substantially greater than that of ER. The implication of these findings is that dietary components that modulate detoxification systems should be studied carefully before being recommended for use during chemotherapy, as these compounds may have additional influences on the disposition of chemotherapeutic drugs.

Predicting drug disposition, absorption/elimination/transporter interplay and the role of food on drug absorption

The ability to predict drug disposition involves concurrent consideration of many chemical and physiological variables and the effect of food on the rate and extent of availability adds further complexity due to postprandial changes in the gastrointestinal (GI) tract. A system that allows for the assessment of the multivariate interplay occurring following administration of an oral dose, in the presence or absence of meal, would greatly benefit the early stages of drug development. This is particularly true in an era when the majority of new molecular entities are highly permeable, poorly soluble, extensively metabolized compounds (BDDCS Class 2), which present the most complicated relationship in defining the impact of transporters due to the marked effects of transporter-enzyme interplay. This review evaluates the GI luminal environment by taking into account the absorption/transport/elimination interplay and evaluates the physiochemical property issues by taking into account the importance of solubility, permeability and metabolism. We concentrate on the BDDCS and its utility in predicting drug disposition. Furthermore, we focus on the effect of food on the extent of drug availability (F), which appears to follow closely what might be expected if a significant effect of high fat meals is inhibition of transporters. That is, high fat meals and lipidic excipients would be expected to have little effect on F for Class 1 drugs; they would increase F of Class 2 drugs, while decreasing F for Class 3 drugs.

A novel indole ethyl isothiocyanate (7Me-IEITC) with anti-proliferative and pro-apoptotic effects on platinum-resistant human ovarian cancer cells

OBJECTIVE

A novel indole ethyl isothiocyanate derivative (7Me-IEITC) was defined as a potent growth-suppressing agent to cell lines derived from ovarian cancers. Key mechanisms of the cellular response in vitro were studied and suggest a potential of 7Me-IEITC as a therapeutic drug.

METHODS

The viability of ovarian cancer cell lines (SKOV-3, OVCAR-3) in comparison to pancreatic and prostate cancer cell lines, primary fibroblast and immortalized trophoblasts after treatment with 7Me-IEITC was analyzed. Morphological and apoptotic responses of SKOV-3 were studied by fluorescence microscopy (DAPI staining, TUNEL assay). SKOV-3 proliferation was estimated by a standardized BrdU incorporation assay. The phosphorylation of MAP-Kinases, pro-survival factors and the activation of caspases and PARP-1 were analyzed by western blotting. Changes of the mitochondrial transmembrane-potential and in cell-cycle progression were studied by FACS analysis. MAP-Kinase and caspase inhibitors were employed in cytotoxicity studies.

RESULTS

7Me-IEITC selectively reduced the viability of SKOV-3, OVCAR-3, BXPC-3 and PC-3 cells (IC(50) values < or = 5 microM), while the viability of fibroblasts or trophoblasts remained un-affected at concentrations below 20 microM. 7Me-IEITC treatment down-regulated pro-survival kinases and transcription factors (STAT-3, IKKalpha and NF-kappaB), caused rapid loss of the mitochondrial transmembrane-potential and inactivation of PARP-1 along with activation of caspases. The use of p38 MAP-Kinase-and caspase inhibitors suppressed the cytotoxicity of the drug. 7Me-IEITC acted as an anti-proliferative agent and arrested the cell-cycle progression of SKOV-3 in G2/M phase.

CONCLUSION

7Me-IEITC is a potent and growth-suppressing agent to cell lines derived from ovarian cancers by causing deactivation of survival signals, apoptosis, and cell-cycle arrest.

Identification of Nrf2-regulated genes induced by chemopreventive isothiocyanate PEITC by oligonucleotide microarray

Electrophiles generated during metabolic activation of carcinogens and reactive oxygen species formed from endogenous and exogenous sources might play a significant role in carcinogenesis. Cancer chemoprevention by induction of phase II detoxifying enzymes to counteract the insults of these reactive intermediates is under intensive investigation. Nrf2, a bZIP transcription factor, plays a central role in the regulation of phase II genes by binding to the antioxidant response element (ARE) in their promoters. Identification of novel Nrf2-regulated genes is likely to provide insight into cellular defense systems against the toxicities of electrophiles and oxidants and may define effective targets for achieving cancer chemoprevention. Phenethyl isothiocyanate (PEITC) is a promising chemopreventive agent that exerts its effects by induction of phase II enzymes via activation of Nrf2. In the present study, a transcriptional profile of liver of the wild-type (Nrf2+/+) and knock-out (Nrf2-/-) mice after treatments with vehicle or PEITC at 3 h and at 12 h was generated using the Affymetrix Mouse Genome 430 2.0 Array. Comparative analysis of gene expression changes between different treatment groups of wild-type and Nrf2-deficient mice facilitated identification of numerous genes regulated by Nrf2. These Nrf2-dependent and PEITC-inducible genes include known detoxication enzymes, as well as novel xenobiotic-metabolizing genes regulated by Nrf2 such as CYP 2c55, CYP 2u1 and aldehyde oxidase. Unexpected clusters included genes for heat shock proteins, ubiquitin/26 S proteasome subunits, and lipid metabolism molecules. Collectively, the identification of these genes not only provides novel insight into the effect of PEITC on global gene expression and chemoprevention, but also reveals the role of Nrf2 in those processes, which would confer cancer chemopreventive future.

Quantitative evaluation of isothiocyanates as substrates and inhibitors of P-glycoprotein

The ATP-binding cassette transporter P-glycoprotein (P-gp) exerts a critical role in the systemic disposition of, and exposure to, lipophilic and amphipathic drugs, carcinogens, toxins and other xenobiotics. The ability of P-gp to transfer a wide variety of structurally unrelated compounds from the cell interior across the membrane bilayer remains intriguing. Since dietary chemicals in cruciferous and several other foods appear to exert anticarcinogenic effects by inducing phase II enzymes and inhibiting some phase I enzymes, the isothiocyanate constituents are frequently studied for interactions with various biomacromolecules as well as cytotoxins or isolated cells. Several prominent dietary isothiocyanates were characterized for their interaction with P-gp and their specific effects on the P-gp export activity of several marker substrates. Some of these compounds inhibit the active P-gp-mediated efflux of the fluorescent markers LDS-751 and daunorubicin with low potency, with the most potent among them, phenethyl isothiocyanate, inhibiting transport of the LDS-751 substrate with an IC(50) of approximately 240 microM. Overall, these isothiocyanates are unlikely to impede the xenobiotic defence function of P-gp even in the intestine where the concentrations are potentially high.

Membrane transport of dietary phenethyl isothiocyanate by ABCG2 (breast cancer resistance protein)

Isothiocyanates (ITCs) are non-nutrient constituents abundant in cruciferous vegetables and are effective in blocking carcinogenesis in a variety of tissues. ITCs permeate into cells rapidly and accumulate in cells primarily as glutathione (GSH) conjugates. We have demonstrated recently that certain ITCs are inhibitors of ABCG2 (breast cancer resistance protein, BCRP), an ATP-binding cassette transporter that plays an important role in drug absorption and disposition as well as in the development of multidrug resistance in cancer cells. The purpose of this study was to investigate the mechanisms of interactions between ITCs and BCRP and elucidate the transport of phenethyl isothiocyanate (PEITC) by BCRP. Inside-out membrane vesicles were prepared from human breast cancer BCRP-overexpressing MCF-7/MX100 and the parental MCF-7/sensitive cells. The ATPase study using 100 muM ITCs showed that ITCs are potential inhibitors of BCRP ATPase activity. The transport of (14)C-PEITC into BCRP-overexpressing MCF-7/MX100 cell vesicles was ATP-dependent and inhibited by fumitremorgin C (FTC), a specific inhibitor of BCRP, indicating that PEITC is a substrate for BCRP. In the control MCF-7/sensitive cell vesicles, no ATP-dependent and FTC-inhibited transport of (14)C-PEITC was observed. Taken together, the results of this investigation provided evidence that ITCs are potential inhibitors of BCRP ATPase and PEITC, in its unchanged form, is transported by BCRP. These data may be important in elucidating the interaction of ITCs and cellular transporters and in understanding the potential food-drug interaction.

Pharmacokinetics of alpha-naphthyl isothiocyanate in rats

Many naturally occurring and synthetic isothiocyanates can inhibit chemical carcinogenesis in animal models. Recently, we found that alpha-naphthyl isothiocyanate (1-NITC) inhibited P-glycoprotein- and multidrug resistance associated protein 1-mediated efflux, indicating the potential application of 1-NITC as a chemosensitizing agent for cancer chemotherapy. The objective of this study was to explore the pharmacokinetic characteristics of 1-NITC in rats. A single dose of 10, 25, 50, or 75 mg/kg of 1-NITC was administered intravenously or orally to female Sprague-Dawley rats (n = 4 for each group). Dose-normalized concentration-time profiles were not superimposable following intravenous or oral dosing, indicating that the disposition of 1-NITC in rats was nonlinear. As doses increased from 10 to 75 mg/kg following iv administration, the total clearance decreased from 2.2 +/- 0.9 to 0.8 +/- 0.3 L/h/kg; oral availability averaged 0.46 for oral doses of 10-75 mg/kg. A nonlinear two-compartment open model with capacity-limited absorption and capacity-limited elimination from the central compartment best fit the data, based on goodness-of-fit criteria. The mechanism underlying the nonlinear elimination of 1-NITC in rats is most likely due to the capacity-limited metabolism of 1-NITC. This study represents the first report of the pharmacokinetics of 1-NITC.

Pharmacokinetics of Dietary Phenethyl Isothiocyanate in Rats

PURPOSE

Phenethyl isothiocyanate (PEITC) is a dietary component present in cruciferous vegetables and reported to have chemopreventive properties. Previous reports of PEITC pharmacokinetics have measured total ITC (PEITC and its metabolites) in plasma. Our objective was to examine the dose-dependent pharmacokinetics and oral bioavailability of unchanged PEITC, as well as its pH- and temperature-dependent stability and its serum protein binding.

METHODS

Stability was studied at different pH values at room temperature and 4 degrees C. Protein binding was determined by equilibrium dialysis. For the pharmacokinetics study, male Sprague-Dawley rats were administered with PEITC at doses of 2, 10, 100, or 400 micromol/kg intravenously or 10 or 100 micromol/kg orally. Plasma samples were analyzed by liquid chromatography-tandem mass spectrometry. Pharmacokinetic analysis was conducted by WinNonlin and ADAPT II.

RESULTS

Phenethyl isothiocyanate was stable in aqueous buffers at pH 7.4 with half-lives of 56.1 and 108 h at room temperature and 4 degrees C, respectively. The free fraction of PEITC in rat serum was 0.019. The clearance (Cl) at a low dose of PEITC (2 micromol/kg) was 0.70 +/- 0.17 L h(-1) kg(-1) with an apparent volume of distribution (Vss) of 1.94 +/- 0.42 L/kg. At higher doses, Cl tended to decrease, whereas Vss increased. Oral bioavailability of PEITC was 115 and 93% at doses of 10 and 100 micromol/kg, respectively. A three-compartment model with Michaelis-Menten elimination and distribution was found to best characterize the plasma concentration profiles.

CONCLUSIONS

Phenethyl isothiocyanate is stable in biological samples, with increased stability under refrigerated conditions. It has high oral bioavailability, low clearance, and high protein binding in rats; nonlinear elimination and distribution occur following the administration of high doses. This investigation represents the first report of the pharmacokinetics of dietary PEITC.

Transport of dietary phenethyl isothiocyanate is mediated by multidrug resistance protein 2 but not P-glycoprotein

We demonstrated recently that phenethyl isothiocyanate (PEITC), a potent anticarcinogen present in cruciferous vegetables, inhibited P-glycoprotein (P-gp) and multidrug resistance protein 1 (MRP1) and that MRP1 can transport PEITC and/or its metabolites. In this study, we have examined whether PEITC is transported by P-gp and MRP2, two transporters with high expression in human intestine, liver and kidney. Using (14)C-PEITC, no significant difference was observed for the intracellular accumulation of PEITC in human breast cancer MCF-7/sensitive (control) and MCF-7/ADR (P-gp overexpressing) cells at PEITC concentrations of 1, 10 and 50 microM. Moreover, the presence of verapamil or PSC833, two P-gp inhibitors, had no significant effect on the intracellular accumulation of PEITC in P-gp overexpressing MCF-7/ADR and MDA435/LCC6MDR1 cells, indicating that PEITC may not be a substrate for P-gp. In contrast, (14)C-PEITC intracellular accumulation in the kidney epithelial MDCK II/MRP2 cells (transfected with human MRP2) was significantly lower than in the wild-type MDCK II/wt cells at PEITC concentrations of 1, 5, 10 and 50 microM. The presence of MK571, an MRP inhibitor, significantly enhanced (14)C-PEITC accumulation in MDCK II/MRP2 but not MDCK II/wt cells. Furthermore, depletion of intracellular glutathione (GSH) following treatment with buthionine sulphoximine, an inhibitor of GSH biosynthesis, significantly increased (14)C-PEITC intracellular accumulation in a concentration-dependent manner. Transcellular transport studies also demonstrated that depletion of intracellular GSH reduced the mean ratio of basal-to-apical transport to apical-to-basal transport of PEITC in MDCK II/MRP2, but not MDCK II/wt cell monolayers. These results indicate that GSH plays an important role in the MRP2-mediated transport of PEITC. The findings provide new information concerning the interactions between PEITC and membrane transporters and suggest the possibility of PEITC interactions with xenobiotics that are MRP2 substrates.

Effects of benzyl-, phenethyl-, and alpha-naphthyl isothiocyanates on P-glycoprotein- and MRP1-mediated transport

The objective of this investigation was to evaluate the effects of two dietary isothiocyanates (ITCs), benzyl- (BITC) and phenethyl isothiocyanate (PEITC), and one synthetic ITC, alpha-naphthyl isothiocyanate (1-NITC), on the P-glycoprotein (P-gp)- and multidrug-resistance protein 1 (MRP1)-mediated efflux of daunomycin (DNM), determine whether PEITC is a substrate of P-gp and/or MRP1, and elucidate the mechanism(s) involved in the inhibition of transport. BITC, PEITC, and 1-NITC significantly increased the 2-h accumulation of DNM in MCF-7/ADR (P-gp overexpression), PANC-1 (MRP1 overexpression), and human colon adenocarcinoma Caco-2 cells (except for 1-NITC). The accumulation of (14)C-PEITC was not changed in Caco-2, human breast cancer MDA435/LCC6 and MDA435/LCC6MDR1 (P-gp overexpression) cells in the absence and presence of the P-gp inhibitor verapamil, but significantly increased with the MRP inhibitor MK571 in PANC-1 cells. The isocyanate and amine metabolites had no effect on DNM accumulation in any cell line. After 2- and 24-h ITC treatments, cellular concentrations of glutathione (GSH) in PANC-1 and Caco-2 cells were depleted by BITC and PEITC, but not by 1-NITC; glutathione-S-transferase activity exhibited small changes. Our results suggest that (1) BITC, PEITC, and 1-NITC inhibit the P-gp- and MRP1-mediated efflux of DNM; (2) PEITC and/or its conjugates do not represent P-gp substrates; (3) BITC and PEITC, but not 1-NITC, inhibit MRP1 through the depletion of intracellular GSH, which acts as a cosubstrate for DNM efflux via MRP1; and (4) PEITC and/or its conjugates are MRP1 substrates so binding interactions with DNM represent a second potential mechanism involved in MRP1 inhibition.

Effect of Organic Isothiocyanates on Breast Cancer Resistance Protein (ABCG2)-Mediated Transport

PURPOSE

To investigate the effect of organic isothiocyanates (ITCs), dietary compounds with chemopreventive activity, on breast cancer resistance protein (BCRP)-mediated transport.

METHODS

The effect of 12 ITCs on the cellular accumulation of mitoxantrone (MX) was measured in both BCRP-overexpressing and BCRP-negative human breast cancer (MCF-7) and large cell lung carcinoma (NCI-H460) cells by flow cytometric analysis. The ITCs showing activity in MX accumulation were examined for their effect on MX cytotoxicity, and the intracellular accumulation of radiolabeled phenethyl isothiocyanate (PEITC) was measured in both BCRP-overexpressing and BCRP-negative NCI-H460 cells.

RESULTS

ITCs significantly increased MX accumulation and reversed its cytotoxicity in resistant cells, but had a small or no effect in sensitive cells. The effects of ITCs on MX accumulation and cytotoxicity were ITC-concentration dependent. Significant increases in MX accumulation were observed at ITC concentrations of 10 or 30 microM, and significant reversal of MX cytotoxicity was generally observed at ITC concentrations of 10 microM. Intracellular accumulation of radiolabeled PEITC in BCRP-overexpressing cells was significantly lower than that in BCRP-negative cells and was increased significantly by the BCRP inhibitor fumitremorgin C (FTC).

CONCLUSIONS

Certain ITCs are BCRP inhibitors and PEITC and/or its cellular metabolite(s) may represent BCRP substrates, suggesting the potential for diet-drug interactions.

Determination of alpha-naphthylisothiocyanate and metabolites alpha-naphthylamine and alpha-naphthylisocyanate in rat plasma and urine by high-performance liquid chromatography

A rapid and sensitive high-performance liquid chromatographic (HPLC) assay for the determination of alpha-naphthylisothiocyanate (1-NITC) and two metabolites alpha-naphthylamine (1-NA) and alpha-naphthylisocyanate (1-NIC) in rat plasma and urine has been developed. The chromatographic analysis was carried out using reversed-phase isocratic elution with a Partisphere C(18) 5-microm column, a mobile phase of acetonitrile-water (ACN-H(2)O 70:30, v/v), and detection by ultraviolet (UV) absorption at 305 nm. The lower limits of quantitation (LLQ) in rat plasma, urine, and ACN were 10, 30, and 10 ng/ml for 1-NITC; 30, 100, and 30 ng/ml for 1-NA; and 30 ng/ml in ACN for 1-NIC. At low (10 ng/ml), medium (500 ng/ml), and high (5000 ng/ml) concentrations of quality control samples (QCs), the range of within-day and between-day accuracies were 95-106 and 97-103% for 1-NITC in plasma, respectively. Stability studies showed that 1-NITC was stable at all tested temperatures in ACN, and at -20 and -80 degrees C in plasma, urine, and ACN precipitated plasma and urine, but degraded at room temperature and 4 degrees C. 1-NA was stable in all of the tested matrices at all temperatures. 1-NIC was unstable in plasma, urine, and ACN precipitated plasma and urine, but stable in ACN. The degradation product of 1-NITC and 1-NIC in universal buffer was confirmed to be 1-NA. 1-NITC and 1-NA were detected and quantified in rat plasma and urine, following the administration of a 25 mg/kg i.v. dose of 1-NITC to a female Sprague-Dawley rat.