Naturally-derived phenethyl isothiocyanate modulates apoptotic induction through regulation of the intrinsic cascade and resulting apoptosome formation in human malignant melanoma cells.

Malignant melanoma is the most aggressive type of skin cancer with increasing incidence rates worldwide. On the other hand, watercress is a rich source of phenethyl isothiocyanate (PEITC), among others, which has been widely investigated for its anticancer properties against various cancers. In the present study, we evaluated the role of a watercress extract in modulating apoptotic induction in an in vitro model of human malignant melanoma consisting of melanoma (A375, COLO-679, COLO-800), non-melanoma epidermoid carcinoma (A431) and immortalized, non-tumorigenic keratinocyte (HaCaT) cells. Moreover, the chemical composition of the watercress extract was characterized through UPLC MS/MS and other analytical methodologies. In addition, cytotoxicity was assessed by the alamar blue assay whereas apoptosis was determined, initially, by a multiplex activity assay kit (measuring levels of activated caspases -3, -8 and -9) as well as by qRT-PCR for the identification of major genes regulating apoptosis. In addition, protein expression levels were evaluated by western immunoblotting. Our data indicate that the extract contains various phytochemicals (e.g. phenolics, flavonoids, pigments, etc.) while isothiocyanates (ITCs; especially PEITC) were the most abundant. In addition, the extract was shown to exert a significant time- and dose-dependent cytotoxicity against all malignant melanoma cell lines while non-melanoma and non-tumorigenic cells exhibited significant resistance. Finally, expression profiling revealed a number of genes (and corresponding proteins) being implicated in regulating apoptotic induction through activation of the intrinsic apoptotic cascade. Overall, our data indicate the potential of PEITC as a promising anti-cancer agent in the clinical management of human malignant melanoma.

Naturally Derived Phenethyl Isothiocyanate Modulates Induction of Oxidative Stress via Its N-Acetylated Cysteine Conjugated form in Malignant Melanoma.

Phenethyl isothiocyanate (PEITC) is a secondary metabolic product yielded upon the hydrolysis of gluconasturtiin and it is highly accumulated in the flowers of watercress. The aim of the current study was to assess the role of a naturally derived PEITC-enriched extract in the induction of oxidative stress and to evaluate its anti-melanoma potency through the regulation of its metabolism with the concurrent production of the N-acetyl cysteine conjugated by-product. For this purpose, an in vitro melanoma model was utilized consisting of human primary (A375) cells as well as metastatic (COLO-679) malignant melanoma cells together with non-tumorigenic immortalized keratinocytes (HaCaT). Cytotoxicity was assessed via the Alamar Blue assay whereas the antioxidant/prooxidant activity of PEITC was determined via spectrophotometric assays. Finally, kinetic characterization of the end-product of PEITC metabolism was monitored via UPLC coupled to a tandem mass spectrometry (MS/MS). Our results indicate that although PhEF showed very minor antioxidant activity in a cell-free system, in a cell-based system, it can modulate the activity of key enzyme(s) involved in cellular antioxidant defense mechanism(s). In addition, we have shown that PhEF induces lipid and protein oxidation in a concentration-dependent manner, while its cytotoxicity is not only dependent on PEITC itself but also on its N-acetylated cysteine conjugated form.

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.

Polyphenolics, glucosinolates and isothiocyanates profiling of aerial parts of Nasturtium officinale (Watercress).

Watercress (Nasturtium officinale) is a rich source of secondary metabolites with disease-preventing and/or health-promoting properties. Herein, we have utilized extraction procedures to isolate fractions of polyphenols, glucosinolates and isothiocyanates to determine their identification, and quantification. In doing so, we have utilized reproducible analytical methodologies based on liquid chromatography with tandem mass spectrometry by either positive or negative ion mode. Due to the instability and volatility of isothiocyanates, we followed an ammonia derivatization protocol which converts them into respective ionizable thiourea derivatives. The analytes' content distribution map was created on watercress flowers, leaves and stems. We have demonstrated that watercress contains significantly higher levels of gluconasturtiin, phenethyl isothiocyanate, quercetin-3-O-rutinoside and isorhamnetin, among others, with their content decreasing from flowers (82.11 ± 0.63, 273.89 ± 0.88, 1459.30 ± 12.95 and 289.40 ± 1.37 ng/g of dry extract respectively) to leaves (32.25 ± 0.74, 125.02 ± 0.52, 1197.86 ± 4.24 and 196.47 ± 3.65 ng/g of det extract respectively) to stems (9.20 ± 0.11, 64.7 ± 0.9, 41.02 ± 0.18, 65.67 ± 0.84 ng/g of dry extract respectivbely). Pearson's correlation analysis has shown that the content of isothiocyanates doesn't depend only on the bioconversion of individual glucosinolates but also on other glucosinolates of the same group. Overall, we have provided comprehensive analytical data of the major watercress metabolites thereby providing an opportunity to exploit different parts of watercress for potential therapeutic applications.

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.

The Role of Isothiocyanates as Cancer Chemo-Preventive, Chemo-Therapeutic and Anti-Melanoma Agents.

Many studies have shown evidence in support of the beneficial effects of phytochemicals in preventing chronic diseases, including cancer. Among such phytochemicals, sulphur-containing compounds (e.g., isothiocyanates (ITCs)) have raised scientific interest by exerting unique chemo-preventive properties against cancer pathogenesis. ITCs are the major biologically active compounds capable of mediating the anticancer effect of cruciferous vegetables. Recently, many studies have shown that a higher intake of cruciferous vegetables is associated with reduced risk of developing various forms of cancers primarily due to a plurality of effects, including (i) metabolic activation and detoxification, (ii) inflammation, (iii) angiogenesis, (iv) metastasis and (v) regulation of the epigenetic machinery. In the context of human malignant melanoma, a number of studies suggest that ITCs can cause cell cycle growth arrest and also induce apoptosis in human malignant melanoma cells. On such basis, ITCs could serve as promising chemo-therapeutic agents that could be used in the clinical setting to potentiate the efficacy of existing therapies.

From chemo-prevention to epigenetic regulation: The role of isothiocyanates in skin cancer prevention.

Skin cancer incidence is rapidly growing over the last decades and is generally divided into malignant melanoma and non-melanoma (NMSC) with the latter being subdivided into squamous (SCC) and basal cell carcinoma (BCC). Among them, melanoma is the most aggressive type with high mortality rates. On the other hand, aberrant gene expression is a critical step towards malignant transformation. To this end, epigenetic modifications like changes in DNA methylation patterns and miRNA expression profile as well as histone modifications are all capable of inducing an altered gene expression profile involved in various cellular cascades including cell cycle, proliferation and apoptosis. In general, there is an interest about the beneficiary effect of various phytochemicals in the prevention and treatment of skin malignancies. Among them, glucosinolates are an important type of compounds, abundant in cruciferous vegetables, which are hydrolysed by an endogenous enzyme called myrosinase to a range of bioactive compounds including isothiocyanates (ITCs). These are the major biologically active products capable of mediating the anti-cancer effect of cruciferous vegetables. Their chemo-preventive action is mainly attributed to a plurality of anti-cancer properties including regulation of the epigenetic machinery. Current evidence supports the view that ITCs are potent compounds in interacting with the epigenome in order to restore the normal epigenetic landscape in malignant cells. This review article summarizes the current state of knowledge on the epigenetic modifications that lead to malignant transformation and the role of ITCs with respect to their ability to restore the epigenetic landscape that contributes to skin carcinogenesis.