Phenethyl isothiocyanate induces calcium mobilization and mitochondrial cell death pathway in cholangiocarcinoma KKU-M214 cells

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.

Corosolic Acid Induced Apoptosis via Upregulation of Bax/Bcl-2 Ratio and Caspase-3 Activation in Cholangiocarcinoma Cells

Cholangiocarcinoma (CCA), an aggressive malignancy arising from the biliary epithelium, exhibits a high incidence in Thailand. CCA usually lacks specific symptoms and is typically diagnosed in its advanced stages, presenting significant treatment challenges. Current CCA therapeutic options, including surgery, chemotherapy, and radiation, have limited success rates and often cause side effects. Nature-derived compounds hold promise for reducing undesirable adverse effects and are an excellent source of anticancer drugs. Corosolic acid (CA), a triterpenoid found in Lagerstroemia speciosa L. leaves, exhibits anticancer properties; however, the effectiveness of CA against CCA and its molecular mechanisms remained unexplored. Herein, the anti-CCA and apoptosis-inducing effects of CA were investigated using various techniques, i.e., the MTT assay, flow cytometry with FITC-labeled Annexin V (Annexin V-FITC) and propidium iodide double staining, JC-1 staining, western blot analysis, caspase-3 activity assay, and molecular dynamics (MD) simulations. CA inhibited the proliferation of KKU-213A and KKU-213B CCA cells and triggered apoptosis through alterations in mitochondrial membrane potential (ΔΨm), and increases in the Bax/Bcl-2 expression ratio, cytochrome c release, and caspase-3 activity. As indicated by MD simulations, CA has the potential to bind to Bcl-2 through hydrogen bonds between amino acid residues R146 and N143. These findings underscore the potential of CA as a promising candidate for treatment of CCA.

A Naturally Derived Watercress Flower-Based Phenethyl Isothiocyanate-Enriched Extract Induces the Activation of Intrinsic Apoptosis via Subcellular Ultrastructural and Ca2+ Efflux Alterations in an In Vitro Model of Human Malignant Melanoma

The aim of the current study was to (i) extract isolated fractions of watercress flowers enriched in polyphenols, phenethyl isothiocyanate and glucosinolates and (ii) characterize the anticancer mode of action of non-lethal, sub-lethal and lethal concentrations of the most potent extract fraction in primary (A375) and metastatic (COLO-679) melanoma cells as well as non-tumorigenic immortalized keratinocyte (HaCaT) cells. Cytotoxicity was assessed via the Alamar Blue assay, whereas ultrastructural alterations in mitochondria and the endoplasmic reticulum were determined via transmission electron microscopy. Mitochondrial membrane depolarization was determined using Mito-MP dye, whereas apoptosis was evaluated through the activation of caspases-3, -8 and -9. Among all extract fractions, the phenethyl isothiocyanate-enriched one (PhEF) possessed significant cytotoxicity against A375 and COLO-679 cells, while HaCaT cells remained relatively resistant at sub-lethal and lethal concentrations. Additionally, ultrastructural subcellular alterations associated with apoptosis were observed by means of increased mitochondrial area and perimeter, decreased cristae density and a shorter distance of the endoplasmic reticulum to the mitochondria, all taking place during "early" time points (2-4 h) of exposure. Moreover, PhEF induced mitochondrial membrane depolarization associated with "late" time points (24 h) of exposure, thereby leading to the activation of intrinsic apoptosis. Finally, the inhibition of cytosolic Ca2+ efflux reduced levels of caspases-9 and -3 activity, suggesting the involvement of Ca2+ efflux in modulating the activation of intrinsic apoptosis. To conclude, our data demonstrate an association of "early" ultrastructural alterations in mitochondria and the endoplasmic reticulum with the "late" induction of intrinsic apoptosis via the modulation of Ca2+ efflux.

Allyl Isothiocianate Induces Ca2+ Signals and Nitric Oxide Release by Inducing Reactive Oxygen Species Production in the Human Cerebrovascular Endothelial Cell Line hCMEC/D3

Nitric oxide (NO) represents a crucial mediator to regulate cerebral blood flow (CBF) in the human brain both under basal conditions and in response to somatosensory stimulation. An increase in intracellular Ca2+ concentrations ([Ca2+]i) stimulates the endothelial NO synthase to produce NO in human cerebrovascular endothelial cells. Therefore, targeting the endothelial ion channel machinery could represent a promising strategy to rescue endothelial NO signalling in traumatic brain injury and neurodegenerative disorders. Allyl isothiocyanate (AITC), a major active constituent of cruciferous vegetables, was found to increase CBF in non-human preclinical models, but it is still unknown whether it stimulates NO release in human brain capillary endothelial cells. In the present investigation, we showed that AITC evoked a Ca2+-dependent NO release in the human cerebrovascular endothelial cell line, hCMEC/D3. The Ca2+ response to AITC was shaped by both intra- and extracellular Ca2+ sources, although it was insensitive to the pharmacological blockade of transient receptor potential ankyrin 1, which is regarded to be among the main molecular targets of AITC. In accord, AITC failed to induce transmembrane currents or to elicit membrane hyperpolarization, although NS309, a selective opener of the small- and intermediate-conductance Ca2+-activated K+ channels, induced a significant membrane hyperpolarization. The AITC-evoked Ca2+ signal was triggered by the production of cytosolic, but not mitochondrial, reactive oxygen species (ROS), and was supported by store-operated Ca2+ entry (SOCE). Conversely, the Ca2+ response to AITC did not require Ca2+ mobilization from the endoplasmic reticulum, lysosomes or mitochondria. However, pharmacological manipulation revealed that AITC-dependent ROS generation inhibited plasma membrane Ca2+-ATPase (PMCA) activity, thereby attenuating Ca2+ removal across the plasma membrane and resulting in a sustained increase in [Ca2+]i. In accord, the AITC-evoked NO release was driven by ROS generation and required ROS-dependent inhibition of PMCA activity. These data suggest that AITC could be exploited to restore NO signalling and restore CBF in brain disorders that feature neurovascular dysfunction.

Plant pathogenic bacterium can rapidly evolve tolerance to an antimicrobial plant allelochemical

Crop losses to plant pathogens are a growing threat to global food security and more effective control strategies are urgently required. Biofumigation, an agricultural technique where Brassica plant tissues are mulched into soils to release antimicrobial plant allelochemicals called isothiocyanates (ITCs), has been proposed as an environmentally friendly alternative to agrochemicals. Whilst biofumigation has been shown to suppress a range of plant pathogens, its effects on plant pathogenic bacteria remain largely unexplored. Here, we used a laboratory model system to compare the efficacy of different types of ITCs against Ralstonia solanacearum plant bacterial pathogen. Additionally, we evaluated the potential for ITC‐tolerance evolution under high, intermediate, and low transfer frequency ITC exposure treatments. We found that allyl‐ITC was the most efficient compound at suppressing R. solanacearum growth, and its efficacy was not improved when combined with other types of ITCs. Despite consistent pathogen growth suppression, ITC tolerance evolution was observed in the low transfer frequency exposure treatment, leading to cross‐tolerance to ampicillin beta‐lactam antibiotic. Mechanistically, tolerance was linked to insertion sequence movement at four positions in genes that were potentially associated with stress responses (H‐NS histone like protein), cell growth and competitiveness (acyltransferase), iron storage ([2‐Fe‐2S]‐binding protein) and calcium ion sequestration (calcium‐binding protein). Interestingly, pathogen adaptation to the growth media also indirectly selected for increased ITC tolerance through potential adaptations linked with metabolism and antibiotic resistance (dehydrogenase‐like protein) and transmembrane protein movement (Tat pathway signal protein). Together, our results suggest that R. solanacearum can rapidly evolve tolerance to allyl‐ITC plant allelochemical which could constrain the long‐term efficiency of biofumigation biocontrol and potentially shape pathogen evolution with plants.

Evaluation of Bioactive Properties of Lipophilic Fractions of Edible and Non-Edible Parts of Nasturtium officinale (watercress) in a Model of Human Malignant Melanoma Cells

Watercress is an enriched source of phenethyl isothiocyanate (PEITC), among other phytochemicals, with an antioxidant capacity. The aim of this study was to (i) chemically characterize and (ii) biologically evaluate the profile of the main health-promoting compounds contained in edible (i.e., mixture of leaves and lateral buds) and non-edible (i.e., stems) parts of watercress in an in vitro model of malignant melanoma consisting of human malignant melanoma (A375), non-melanoma (A431) and keratinocyte (HaCaT) cells. The extraction of the main constituents of watercress was performed by subjecting the freeze-dried edible and non-edible samples through different extraction protocols, whereas their concentration was obtained utilizing analytical methodologies. In addition, cell viability was evaluated by the Alamar Blue assay, whereas levels of oxidative stress and apoptosis were determined by commercially available kits. The edible watercress sample contained a higher amount of various nutrients and phytochemicals in the hexane fraction compared to the non-edible one, as evidenced by the presence of PEITC, phenolics, flavonoids, pigments, ascorbic acid, etc. The cytotoxicity potential of the edible watercress sample in the hexane fraction was considerably higher than the non-edible one in A375 cells, whereas A431 and HaCaT cells appeared to be either more resistant or minimally affected, respectively. Finally, levels of oxidative stress and apoptotic induction were increased in both watercress samples, but the magnitude of the induction was much higher in the edible than the non-edible watercress samples. Herein, we provide further evidence documenting the potential development of watercress extracts (including watercress waste by-products) as promising anti-cancer agent(s) against malignant melanoma cells.

Phenylethyl isothiocyanate induces oxidative damage of porcine kidney cells mediated by reactive oxygen species

The aim of this study is to confirm the toxic effect of phenylethyl isothiocyanate (PEITC) on porcine kidney cells (PK-15) and explore the effect of oxidative damage mediated by reactive oxygen species (ROS) induced by PEITC in PK-15 cells. Porcine kidney cell line (PK-15) was treated with PEITC (2, 5, and 10  µM) for 24 hours, and the oxidative damage mediated by PEITC through ROS was investigated. The survival rate of PK-15 cells decreased in a dose-dependent manner after the treatment of PEITC in a dose-dependent manner. A high concentration of PEITC (10 µM) can change cell morphology, increase the content of malondialdehyde, ROS, and lactate dehydrogenase, and decrease the activity of SOD, CAT, GSH-PX, and GSH. PEITC has a toxic effect on PK-15 cells by inducing oxidative stress in PK-15 cells through the generation of ROS.

Mitochondrial division inhibitor-1 potentiates cisplatin-induced apoptosis via the mitochondrial death pathway in cholangiocarcinoma cells

AIMS

Mdivi-1, a selective Drp-1 inhibitor, impedes mitochondrial dynamics and suppresses cancer proliferation and progression. Cholangiocarcinoma (CCA) is a very aggressive malignancy which is refractory to chemotherapy. The study investigated the mechanism of the chemosensitizing effect of mdivi-1 in cholangiocarcinoma.

MAIN METHODS

CCA cells and HEK293 T cells were employed in the study. Cell viability and induction of apoptotic cell death were determined by the MTT and acridine orange-ethidium bromide methods. Cellular glutathione content and reactive oxygen species (ROS) formation were assessed using thiol green and 2',7'-dichlorofluorescin diacetate fluorescent probes, respectively. Mitochondrial transmembrane potential and autophagy were detected by JC-1 dye and autophagy assay. Cell cycle progression was analyzed by flow cytometry. Cell migration was measured using the wound healing assay. Proteins involved in cell proliferation and cell cycle were analyzed by western immunoblotting.

KEY FINDINGS

Mdivi-1 enhanced cisplatin-induced cytotoxicity in CCA cells but not in HEK293 T cells. Mdivi-1 enhanced cisplatin induced glutathione redox stress, ROS formation, and loss of mitochondrial transmembrane potential. Moreover, mdivi-1 also inhibited autophagic flux and suppressed CCA cell migration.

SIGNIFICANCE

Mdivi-1 sensitized CCA cells to cytotoxicity of cisplatin in association with increases of oxidative stress and autophagosomes, and induced cell death via the mitochondrial pathway. Disruption of mitochondrial dynamics may be a novel strategy to improve the efficacy of chemotherapy to treat CCA.

Metformin sensitizes cholangiocarcinoma cell to cisplatin-induced cytotoxicity through oxidative stress mediated mitochondrial pathway

AIMS

Metformin (Met), an essential antidiabetic agent, shows antitumor activity in some cancers. A previous study showed that Met enhanced cytotoxic activity of cisplatin (Cis) in cholangiocarcinoma (CCA) in association with the activation of AMP-activated protein kinase and suppression of Akt-mTOR. However, these effects do not entirely explain the observed chemosensitizing effect. The present study investigated the interaction of Met and Cis over the enhanced antitumor effect.

MAIN METHODS

KKU-100 and KKU-M156 cells were used in the study. Cytotoxicity was assessed by acridine orange-ethidium bromide staining. Reactive oxygen species (ROS) and mitochondrial transmembrane potential (Δψ_m) were measured by dihydroethidium and JC-1 fluorescent methods. Cellular glutathione (GSH) and redox ratio were analyzed by enzymatic coupling assay. Proteins associated with antioxidant system and cell death were evaluated by western immunoblot.

KEY FINDINGS

Cytotoxicity of Cis was enhanced by Met in association with ROS formation and GSH redox stress. The antioxidants, N-acetylcysteine and TEMPOL, and MPTP inhibitor, cyclosporine, attenuated cytotoxicity in association with suppression of ROS formation and the losses of Δψ_m. Met in combination with Cis suppressed expression of Nrf2 and altered the expression of Bcl2 family proteins.

SIGNIFICANCE

The chemosensitizing effect of Met in combination with Cis is causally associated with increased oxidative stress-mediated mitochondrial cell death pathway. Met may improve the efficacy of Cis in the treatment of cancer.

Suppression of glutathione S-transferases potentiates the cytotoxic effect of phenethyl isothiocyanate in cholangiocarcinoma cells

Phenethyl isothiocyanate (PEITC) is a potential cancer prevention agent that is found in cruciferous vegetables. Previous studies have shown that the effect of PEITC-induced cell death declines rapidly after administration. The metabolic fate of PEITC is modulated by glutathione S-transferases (GST). In this study, we investigated whether GST activity modulates PEITC-induced cytotoxicity on cholangiocarcinoma (CCA) cells. The sensitivity of KKU-M214 and KKU-100 cells to PEITC was associated with GST activity. Two GST inhibitors, ethacrynic acid (EA) and cibacron blue, potentiated the cytotoxic effect of PEITC in CCA cells. PEITC-induced glutathione (GSH) depletion and redox stress, whereas EA itself or in combination with PEITC did not alter GSH redox status. The enhanced cytotoxic effect of EA may be due to inhibition of GST activity. This idea was validated by using siRNA directed against GSTP1 mRNA in KKU-M214 cells, and GSTP1 and GSTT1 mRNA in KKU-100 cells. These GST isoforms were abundantly expressed in the cell lines. Knockdown of GSTs in CCA cell lines potentiated the cytotoxic effect of PEITC. The present study shows that the antitumor effect of PEITC was potentiated by the suppression of GST activity. The inhibition of GST could be a crucial strategy to potentiate chemotherapeutic effect of PEITC on CCA.

Suppression of Nrf2 confers chemosensitizing effect through enhanced oxidant-mediated mitochondrial dysfunction

AIMS

Transcription factor Nrf2, which regulates the expression of cytoprotective and antioxidant enzymes, contributes to proliferation and resistance to chemotherapy in cancer. The inhibition of Nrf2 can sensitize cholangiocarcinoma (CCA) cells to the cytotoxicity of several chemotherapeutic agents. In this study, we investigated the mechanism of this chemosensitizing effect.

MAIN METHODS

KKU-100 cells were used in the study. Nrf2 expression was knocked down by siRNA and expression was validated by reverse transcription and polymerase chain reaction. Cytotoxicity was assessed by sulforhodamine B method. Intracellular reactive oxygen species (ROS) was examined by fluorescent dye, dichlorofluorescin diacetate method and mitochondrial transmembrane potential was assessed by JC1 dye assay.

KEY FINDINGS

Cytotoxicity of cisplatin (Cis) in KKU-100 cells was enhanced by knockdown of Nrf2 expression. The enhanced cytotoxic effect was abolished by treatment with N-acetylcysteine, TEMPOL and MnTBAP. Cells with Nrf2 knockdown or Cis treatment increased production of ROS, and ROS was markedly enhanced by a combination of Nrf2 knockdown and Cis. The increased ROS formation was associated with a decrease in mitochondrial transmembrane potential (Δψ_m), where this decrease was prevented by antioxidant compounds. The loss of Δψ_m and cell death were prevented by cyclosporine, an inhibitor of mitochondrial permeability transition pore (MPTP). Luteolin inhibited Nrf2 and markedly enhanced cytotoxicity in combination with Cis.

SIGNIFICANCE

Inhibition of Nrf2 is a feasible strategy in enhancing antitumor activity of chemotherapeutic agents and improving efficacy of chemotherapy in CCA.

Establishment of cholangiocarcinoma cell lines from patients in the endemic area of liver fluke infection in Thailand

Cholangiocarcinoma is a rare type of cancer which is an increasingly discernible health threat. The disease is usually very difficult in diagnosis and various treatment modalities are typically not effective. Cholangiocarcinoma is a complex and very heterogeneous malignancy characterized by tumor location, different risk factors, molecular profiling, and prognosis. Cancer cell lines represent an important tool for investigation in various aspects of tumor biology and molecular therapeutics. We established two cell lines, KKU-452 and KKU-023, which were derived from patients residing in the endemic area of liver fluke infection in Thailand. Both of tumor tissues have gross pathology of perihilar and intrahepatic mass-forming cholangiocarcinoma. Two cell lines were characterized for their biological, molecular and genetic properties. KKU-452 and KKU-023 cells are both adherent cells with epithelium morphology, but have some differences in their growth pattern (a doubling time of 17.9 vs 34.8 h, respectively) and the expression of epithelial bile duct markers, CK7 and CK19. Cytogenetic analysis of KKU-452 and KKU-023 cells revealed their highly complex karyotypes; hypertriploid and hypotetraploid, respectively, with multiple chromosomal aberrations. Both cell lines showed mutations in p53 but not in KRAS. KKU-452 showed a very rapid migration and invasion properties in concert with low expression of E-cadherin and high expression of N-cadherin, whereas KKU-023 showed opposite characters. KKU-023, but not KKU-452, showed in vivo tumorigenicity in xenografted nude mice. Those two established cholangiocarcinoma cell lines with unique characters may be valuable for better understanding the process of carcinogenesis and developing new therapeutics for the patients

PEITC in End-Stage B-Cell Prolymphocytic Leukemia: Case Report of Possible Sensitization to Salvage R-CHOP

INTRODUCTION

B-cell prolymphocytic leukemia (B-PLL) is a rare, aggressive leukemia distinct from chronic lymphocytic leukemia, with median survival of only 3 years. B-PLL is resistant to most chemotherapy and newer targeted therapies such as alemtuzumab and thalidomide. Phenylethyl isothiocyanate (PEITC) is a natural compound from horseradish with evidence for therapeutic potential in multiple leukemia types.

CASE PRESENTATION

Here we present a case report of a 53-year-old man whose chronic lymphocytic leukemia transformed to end-stage B-PLL, disqualifying him for allogenic stem cell transplantation. He was treated with PEITC followed by salvage R-CHOP (Rituximab, Cyclophosphamide, Hydroxydaunorubicin [doxorubicin hydrochloride], Oncovin [vincristine sulfate], Prednisone or Prednisolone) chemotherapy, which led to normalized white blood cell count and disease stabilization that requalified him for allogenic peripheral stem-cell transplant therapy. We conducted a systematic review to analyze and interpret the potential contribution of PEITC to his unexpectedly favorable R-CHOP response. Following sequential 8 weeks of PEITC/pentostatin and 6 cycles of R-CHOP, the patient received allogenic peripheral blood stem cell transplant on an outpatient basis and remains well at the time of this publication, with no evidence of CD20+ small B-cells.

DISCUSSION

Given the limited data for R-CHOP in B-PLL, this patient's recovery suggests presensitization of B-PLL cells toward R-CHOP, potentially justifying further investigation.

SIRT2 mediates NADH-induced increases in Nrf2, GCL, and glutathione by modulating Akt phosphorylation in PC12 cells

SIRT2 plays important roles in multiple biological processes. It is unclear whether SIRT2 affects antioxidant capacity by modulating Nrf2, a key transcription factor for multiple antioxidant genes. By studying NADH-treated differentiated PC12 cells, we found that NADH induced a significant increase in the nuclear Nrf2, which was prevented by both SIRT2 siRNA and SIRT2 inhibitor, AGK2. SIRT2 siRNA also blocked the NADH-induced increases in glutamate cysteine ligase (GCL) and glutathione. Moreover, SIRT2 siRNA and AGK2 blocked NADH-induced Akt phosphorylation, and inhibition of Akt phosphorylation prevented NADH-induced increases in the nuclear Nrf2 and glutathione. Collectively, our study shows that SIRT2 regulates nuclear Nrf2 levels by modulating Akt phosphorylation, thus modulating the levels of GCL and total glutathione.

Using Sensors and Generators of H2O2 to Elucidate the Toxicity Mechanism of Piperlongumine and Phenethyl Isothiocyanate

AIMS

Chemotherapeutics target vital functions that ensure survival of cancer cells, including their increased reliance on defense mechanisms against oxidative stress compared to normal cells. Many chemotherapeutics exploit this vulnerability to oxidative stress by elevating the levels of intracellular reactive oxygen species (ROS). A quantitative understanding of the oxidants generated and how they induce toxicity will be important for effective implementation and design of future chemotherapeutics. Molecular tools that facilitate measurement and manipulation of individual chemical species within the context of the larger intracellular redox network present a means to develop this understanding. In this work, we demonstrate the use of such tools to elucidate the roles of H2O2 and glutathione (GSH) in the toxicity mechanism of two ROS-based chemotherapeutics, piperlongumine and phenethyl isothiocyanate.

RESULTS

Depletion of GSH as a result of treatment with these compounds is not an important part of the toxicity mechanisms of these drugs and does not lead to an increase in the intracellular H2O2 level. Measuring peroxiredoxin-2 (Prx-2) oxidation as evidence of increased H2O2, only piperlongumine treatment shows elevation and it is GSH independent. Using a combination of a sensor (HyPer) along with a generator (D-amino acid oxidase) to monitor and mimic the drug-induced H2O2 production, it is determined that H2O2 produced during piperlongumine treatment acts synergistically with the compound to cause enhanced cysteine oxidation and subsequent toxicity. The importance of H2O2 elevation in the mechanism of piperlongumine promotes a hypothesis of why certain cells, such as A549, are more resistant to the drug than others.

INNOVATION AND CONCLUSION

The approach described herein sheds new light on the previously proposed mechanism of these two ROS-based chemotherapeutics and advocates for the use of both sensors and generators of specific oxidants to isolate their effects. Antioxid. Redox Signal. 24, 924-938.

Calcium efflux from the endoplasmic reticulum regulates cisplatin-induced apoptosis in human cervical cancer HeLa cells

The function of calcium efflux from the endoplasmic reticulum (ER) in cisplatin-induced apoptosis is not fully understood in cancer cells. The present study used western blot analysis, flow cytometry, immunofluorescence and 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide assay to investigate calcium signaling in human cervical cancer cells exposed to cisplatin. In the present study, treatment with cisplatin increased free Ca²⁺ levels in the cytoplasm and mitochondria of human cervical cancer HeLa cells, which further triggers the mitochondria-mediated and ER stress-associated apoptosis pathways. Notably, blocking calcium signaling using the calcium chelating agent bis-(o-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid acetoxymethyl ester inhibited cisplatin-induced apoptosis via downregulation of the calcium-dependent proteases, the calpains, and innate apoptosis proteins, such as caspsae-3, caspase-4 and C/EBP homologous protein (CHOP). In addition, use of the inositol triphosphate receptor inhibitor, 2-aminoethyl diphenylborinate, to inhibit calcium efflux from the ER resulted in similar effects. This data indicated that calcium efflux from the ER plays a significant role in cisplatin-induced apoptosis in human cervical cancer HeLa cells, which provides further mechanistic insights into the tumor cell-killing effect of cisplatin and potential therapeutic strategies to improve cisplatin chemotherapy.

Glucosinolate-derived isothiocyanates impact mitochondrial function in fungal cells and elicit an oxidative stress response necessary for growth recovery

Glucosinolates are brassicaceous secondary metabolites that have long been considered as chemical shields against pathogen invasion. Isothiocyanates (ITCs), are glucosinolate-breakdown products that have negative effects on the growth of various fungal species. We explored the mechanism by which ITCs could cause fungal cell death using Alternaria brassicicola, a specialist Brassica pathogens, as model organism. Exposure of the fungus to ICTs led to a decreased oxygen consumption rate, intracellular accumulation of reactive oxygen species (ROS) and mitochondrial-membrane depolarization. We also found that two major regulators of the response to oxidative stress, i.e., the MAP kinase AbHog1 and the transcription factor AbAP1, were activated in the presence of ICTs. Once activated by ICT-derived ROS, AbAP1 was found to promote the expression of different oxidative-response genes. This response might play a significant role in the protection of the fungus against ICTs as mutants deficient in AbHog1 or AbAP1 were found to be hypersensitive to these metabolites. Moreover, the loss of these genes was accompanied by a significant decrease in aggressiveness on Brassica. We suggest that the robust protection response against ICT-derived oxidative stress might be a key adaptation mechanism for successful infection of host plants by Brassicaceae-specialist necrotrophs like A. brassicicola.

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.

Allyl isothiocyanate depletes glutathione and upregulates expression of glutathione S-transferases in Arabidopsis thaliana

Allyl isothiocyanate (AITC) is a phytochemical associated with plant defense in plants from the Brassicaceae family. AITC has long been recognized as a countermeasure against external threats, but recent reports suggest that AITC is also involved in the onset of defense-related mechanisms such as the regulation of stomatal aperture. However, the underlying cellular modes of action in plants remain scarcely investigated. Here we report evidence of an AITC-induced depletion of glutathione (GSH) and the effect on gene expression of the detoxification enzyme family glutathione S-transferases (GSTs) in Arabidopsis thaliana. Treatment of A. thaliana wild-type with AITC resulted in a time- and dose-dependent depletion of cellular GSH. AITC-exposure of mutant lines vtc1 and pad2-1 with elevated and reduced GSH-levels, displayed enhanced and decreased AITC-tolerance, respectively. AITC-exposure also led to increased ROS-levels in the roots and loss of chlorophyll which are symptoms of oxidative stress. Following exposure to AITC, we found that GSH rapidly recovered to the same level as in the control plant, suggesting an effective route for replenishment of GSH or a rapid detoxification of AITC. Transcriptional analysis of genes encoding GSTs showed an upregulation in response to AITC. These findings demonstrate cellular effects by AITC involving a reversible depletion of the GSH-pool, induced oxidative stress, and elevated expression of GST-encoding genes.

Phenethyl isothiocyanate induces DNA damage-associated G2/M arrest and subsequent apoptosis in oral cancer cells with varying p53 mutations

Phenethyl isothiocyanate (PEITC) is a naturally occurring cruciferous vegetable-derived compound that inhibits cell growth and induces apoptosis in oral cancer cells. However, the exact mechanism of PEITC action has not been fully elucidated. This study investigated the molecular mechanism and anticancer potential of PEITC in oral squamous cell carcinoma (OSCC) cells with various p53 statuses. PEITC inhibited the growth of OC2, SCC4, and SCC25 cells (functional p53 mutants) in a dose-dependent manner with low toxicity to normal cells. Treatment with PEITC induced reactive oxygen species production, nitric oxide generation, and GSH depletion and triggered DNA damage response as evidenced by flow cytometry, 8-OHdG formation, and comet assay. Furthermore, the subsequent activation of ATM, Chk2, and p53 as well as the increased expression of downstream proteins p21 and Bax resulted in a G2/M phase arrest by inhibiting Cdc25C, Cdc2, and cyclin B1. The PEITC-induced apoptotic cell death, following a diminished mitochondrial transmembrane potential, reduced the expression of Bcl-2 and Mcl-1, released mitochondrial cytochrome c, and activated caspase 3 and PARP cleavage. The p53 inhibitor pifithrin-α and the antioxidants N-acetylcysteine and glutathione (GSH) protected the cells from PEITC-mediated apoptosis. However, mito-TEMPO, catalase, apocynin, and L-NAME did not prevent PEITC-induced cell death, suggesting that PEITC induced G2/M phase arrest and apoptosis in oral cancer cells via a GSH redox stress and oxidative DNA damage-induced ATM-Chk2-p53-related pathway. These results provide new insights into the critical roles of both GSH redox stress and p53 in the regulation of PEITC-induced G2/M cell cycle arrest and apoptosis in OSCCs.

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.

Diet components can suppress inflammation and reduce cancer risk

Epidemiology studies indicate that diet or specific dietary components can reduce the risk for cancer, cardiovascular disease and diabetes. An underlying cause of these diseases is chronic inflammation. Dietary components that are beneficial against disease seem to have multiple mechanisms of action and many also have a common mechanism of reducing inflammation, often via the NFκB pathway. Thus, a plant based diet can contain many components that reduce inflammation and can reduce the risk for developing all three of these chronic diseases. We summarize dietary components that have been shown to reduce cancer risk and two studies that show that dietary walnut can reduce cancer growth and development. Part of the mechanism for the anticancer benefit of walnut was by suppressing the activation of NFκB. In this brief review, we focus on reduction of cancer risk by dietary components and the relationship to suppression of inflammation. However, it should be remembered that most dietary components have multiple beneficial mechanisms of action that can be additive and that suppression of chronic inflammation should reduce the risk for all three chronic diseases.