Selective cytostatic and cytotoxic effects of glucosinolates hydrolysis products on human colon cancer cells in vitro

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.

A Comprehensive Review of Health-Benefiting Components in Rapeseed Oil

Rapeseed oil is the third most consumed culinary oil in the world. It is well-known for its high content of unsaturated fatty acids, especially polyunsaturated fatty acids, which make it of great nutritional value. There is increasing evidence that a diet rich in unsaturated fatty acids offers health benefits. Although the consumption of rapeseed oil cuts across many areas around the world, the nutritional elements of rapeseed oil and the exact efficacy of the nutrients remain unclear. In this review, we systematically summarized the latest studies on functional rapeseed components to ascertain which component of canola oil contributes to its function. Apart from unsaturated fatty acids, there are nine functional components in rapeseed oil that contribute to its anti-microbial, anti-inflammatory, anti-obesity, anti-diabetic, anti-cancer, neuroprotective, and cardioprotective, among others. These nine functional components are vitamin E, flavonoids, squalene, carotenoids, glucoraphanin, indole-3-Carbinol, sterols, phospholipids, and ferulic acid, which themselves or their derivatives have health-benefiting properties. This review sheds light on the health-benefiting effects of rapeseed oil in the hope of further development of functional foods from rapeseed.

Cruciferous vegetables as a treasure of functional foods bioactive compounds: Targeting p53 family in gastrointestinal tract and associated cancers

In the past few years, phytochemicals from natural products have gotten the boundless praise in treating cancer. The promising role of cruciferous vegetables and active components contained in these vegetables, such as isothiocyanates, indole-3-carbinol, and isothiocyanates, has been widely researched in experimental in vitro and in vivo carcinogenesis models. The chemopreventive agents produced from the cruciferous vegetables were recurrently proven to affect carcinogenesis throughout the onset and developmental phases of cancer formation. Likewise, findings from clinical investigations and epidemiological research supported this statement. The anticancer activities of these functional foods bioactive compounds are closely related to their ability to upregulate p53 and its related target genes, e.g., p21. As the “guardian of the genome,” the p53 family (p53, p63, and p73) plays a pivotal role in preventing the cancer progression associated with DNA damage. This review discusses the functional foods bioactive compounds derived from several cruciferous vegetables and their use in altering the tumor-suppressive effect of p53 proteins. The association between the mutation of p53 and the incidence of gastrointestinal malignancies (gastric, small intestine, colon, liver, and pancreatic cancers) is also discussed. This review contains crucial information about the use of cruciferous vegetables in the treatment of gastrointestinal tract malignancies.

3,3'-Diindolylmethane Suppresses the Growth of Hepatocellular Carcinoma by Regulating Its Invasion, Migration, and ER Stress-Mediated Mitochondrial Apoptosis

Hepatocellular carcinoma (HCC) is the leading cause of cancer-related death worldwide with limited treatment options. Biomarker-based active phenolic flavonoids isolated from medicinal plants might shed some light on potential therapeutics for treating HCC. 3,3′-diindolylmethane (DIM) is a unique biologically active dimer of indole-3-carbinol (I3C), a phytochemical compound derived from Brassica species of cruciferous vegetables—such as broccoli, kale, cabbage, and cauliflower. It has anti-cancer effects on various cancers such as breast cancer, prostate cancer, endometrial cancer, and colon cancer. However, the molecular mechanism of DIM involved in reducing cancer risk and/or enhancing therapy remains unknown. The aim of the present study was to evaluate anti-cancer and therapeutic effects of DIM in human hepatoma cell lines Hep3B and HuhCell proliferation was measured with MTT and trypan blue colony formation assays. Migration, invasion, and apoptosis were measured with Transwell assays and flow cytometry analyses. Reactive oxygen species (ROS) intensity and the loss in mitochondrial membrane potential of Hep3B and Huh7 cells were determined using dihydroethidium (DHE) staining and tetramethylrhodamine ethyl ester dye. Results showed that DIM significantly suppressed HCC cell growth, proliferation, migration, and invasion in a concentration-dependent manner. Furthermore, DIM treatment activated caspase-dependent apoptotic pathway and suppressed epithelial–mesenchymal transition (EMT) via ER stress and unfolded protein response (UPR). Taken together, our results suggest that DIM is a potential anticancer drug for HCC therapy by targeting ER-stress/UPR.

Sulforaphane as a Promising Natural Molecule for Cancer Prevention and Treatment

Tumorigenicity-inhibiting compounds have been identified in our daily diet. For example, isothiocyanates (ITCs) found in cruciferous vegetables were reported to have potent cancer-prevention activities. The best characterized ITC is sulforaphane (SF). SF can simultaneously modulate multiple cellular targets involved in carcinogenesis, including (1) modulating carcinogen-metabolizing enzymes and blocking the action of mutagens; (2) inhibition of cell proliferation and induction of apoptosis; and (3) inhibition of neo-angiogenesis and metastasis. SF targets cancer stem cells through modulation of nuclear factor kappa B (NF-κB), Sonic hedgehog (SHH), epithelial-mesenchymal transition, and Wnt/β-catenin pathways. Conventional chemotherapy/SF combination was tested in several studies and resulted in favorable outcomes. With its favorable toxicological profile, SF is a promising agent in cancer prevention and/or therapy. In this article, we discuss the human metabolism of SF and its effects on cancer prevention, treatment, and targeting cancer stem cells, as well as providing a brief review of recent human clinical trials on SF.

Structure-based virtual screening, molecular dynamics and binding affinity calculations of some potential phytocompounds against SARS-CoV-2

COVID-19 caused by a positive-sense single stranded RNA virus named as severe acute respiratory syndrome-Coronavirus-2 (SARS-CoV-2) triggered the global pandemic. This virus has infected about 10.37 Crores and taken lives of 2.24 Crores people of 213 countries to date. To cope-up this emergency clinical trials are undergoing with some existing drugs like remdesivir, flavipiravir, lopinavir-ritonavir, nafamostat, doxycycline, hydroxy-chloroquine, dexamethasone, etc., despite their severe toxicity and health hazards among diabetics, hypertensive, cardiac patients or normal individuals. The lack of safe and approved treatment for COVID-19 has forced the scientific community to find novel and safe compounds with potential efficacy. This study evaluates a few selective herbal compounds like glucoraphanin, vitexin, niazinin, etc., as a potential inhibitor of the spike protein and 3-chymotrypsin-like protease (3CLpro) or main protease (Mpro) of SARS-COV-2 through in-silico virtual studies such as molecular docking, target analysis, toxicity prediction and ADME prediction and supported by a Molecular-Dynamic simulation. Selective phytocompounds were docked successfully in the binding site of spike glycoprotein and 3CLpro (Mpro) of SARS-CoV-2. In-silico approaches also predict this molecule to have good solubility, pharmacodynamic property and target accuracy through MD simulation and ADME studies. These hit molecules niazinin, vitexin, glucoraphanin also obey Lipinski's rule along with their stable binding towards target protein of the virus, which makes them suitable for further biochemical and cell-based assays followed by clinical investigations to highlight their potential use in COVID-19 treatment.Communicated by Ramaswamy H. Sarma.

Sulforaphane suppresses the viability and metastasis, and promotes the apoptosis of bladder cancer cells by inhibiting the expression of FAT‑1

FAT atypical cadherin 1 (FAT1) regulates complex mechanisms for the promotion of oncogenesis or the suppression of malignancies. Sulforaphane (SFN) has antioxidant and anti-tumor activities. The present study investigated the roles of SFN and FAT1 in bladder cancer (BC). The expression of FAT1 in BC cell lines and tissues was measured by western blot analysis and reverse transcription-quantitative PCR (RT-qPCR). The association between FAT1 expression and the 5-year survival rate of patients with BC was evaluated. The viability of and FAT1 expression in T24 and SW780 cells exposed to various concentrations of SFN were detected by MTT assay, and western blot analysis and RT-qPCR, respectively. Furthermore, the viability, migration, invasion and apoptosis of and FAT1 expression in BC cells subjected to FAT1 overexpression or knockdown, and with or without SFN stimulation, were examined. The results revealed that FAT1 expression in BC cells and tissues was increased, and patients with a high FAT-1 expression had a shorter 5-year survival time than those with a low FAT-1 expression. BC cell viability and FAT1 expression were suppressed by SFN in a concentration-dependent manner. The knockdown of FAT1 inhibited the viability, migration and invasion, and promoted the apoptosis of BC cells, whereas the overexpression of FAT1 produced opposite effects. In addition, cells exposed to SFN exhibited a reduced viability, migration, invasion and an increased apoptosis, effects which were promoted by FAT1 knockdown; however, the overexpression of FAT1 blocked the above-mentioned effects of SFN on the cells. On the whole, the present study demonstrates that SFN suppresses the progression of BC by inhibiting the expression of FAT-1; thus, SFN may be used as a potential drug for the treatment of BC.

Chemopreventive Agent 3,3'-Diindolylmethane Inhibits MDM2 in Colorectal Cancer Cells

3,3′-Diindolylmethane (DIM) is a naturally derived chemopreventive compound. It comes from glucobrassicin, an indole glucosinolate enriched in cruciferous vegetables, and is formed in the acidic environment of the stomach after ingestion. Mouse double minute 2 homolog (MDM2) is an important, multi-functional oncogenic protein and it has been well recognized for its negative regulation of the tumor suppressor protein p53. We discovered a novel mechanism of action of DIM, that it directly inhibits MDM2 in multiple colorectal cancer (CRC) cell lines. Treatment with DIM decreased MDM2 at messenger RNA (mRNA) and protein levels, inhibited cancer cell proliferation, and induced cell cycle arrest and apoptosis. DIM-induced decrease of MDM2 is p53-independent and is partly mediated by proteasome degradation of MDM2, as blocking of the proteasome activity reversed MDM2 protein inhibition. Overexpression of MDM2 blocked DIM’s effects in growth suppression and apoptosis induction. When combined with imidazoline MDM2 inhibitors (Nutlin-3a and Idasanutlin/RG-7388), synergism was observed in cancer cell growth inhibition. In summary, our data support a new mechanism of action for DIM in direct inhibition of MDM2. The identification of MDM2 as a novel DIM target may help develop a new strategy in CRC prevention.

Crucifera sulforaphane (SFN) inhibits the growth of nasopharyngeal carcinoma through DNA methyltransferase 1 (DNMT1)/Wnt inhibitory factor 1 (WIF1) axis

BACKGROUND

Sulforaphane (SFN), a natural compound present in cruciferous vegetable, has been shown to possess anti-cancer activities. Cancer stem cell (CSC) in bulk tumor is generally considered as treatment resistant cell and involved in cancer recurrence. The effects of SFN on nasopharyngeal carcinoma (NPC) CSCs have not yet been explored.

PURPOSE

The present study aims to examine the anti-tumor activities of SFN on NPC cells with CSC-like properties and the underlying mechanisms.

METHODS

NPC cells growing in monolayer culture, CSCs-enriched NPC tumor spheres, and also the NPC nude mice xenograft were used to study the anti-tumor activities of SFN on NPC. The population of cells expressing CSC-associated markers was evaluated using flow cytometry and aldehyde dehydrogenase (ALDH) activity assay. The effect of DNA methyltransferase 1 (DNMT1) on the growth of NPC cells was analyzed by using small interfering RNA (siRNA)-mediated silencing method.

RESULTS

SFN was found to inhibit the formation of CSC-enriched NPC tumor spheres and reduce the population of cells with CSC-associated properties (SRY (Sex determining Region Y)-box 2 (SOX2) and ALDH). In the functional study, SFN was found to restore the expression of Wnt inhibitory factor 1 (WIF1) and the effect was accompanied with the downregulation of DNMT1. The functional activities of WIF1 and DNMT1 were confirmed using exogenously added recombinant WIF1 and siRNA knockdown of DNMT1. Moreover, SFN was found to inhibit the in vivo growth of C666-1 cells and enhance the anti-tumor effects of cisplatin.

CONCLUSION

Taken together, we demonstrated that SFN could suppress the growth of NPC cells via the DNMT1/WIF1 axis.

Comparative transcriptome analyses of genes involved in sulforaphane metabolism at different treatment in Chinese kale using full-length transcriptome sequencing

Background

Sulforaphane is a natural isothiocyanate available from cruciferous vegetables with multiple characteristics including antioxidant, antitumor and anti-inflammatory effect. Single-molecule real-time (SMRT) sequencing has been used for long-read de novo assembly of plant genome. Here, we investigated the molecular mechanism related to glucosinolates biosynthesis in Chinese kale using combined NGS and SMRT sequencing.

Results

SMRT sequencing produced 185,134 unigenes, higher than 129,325 in next-generation sequencing (NGS). NaCl (75 mM), methyl jasmonate (MeJA, 40 μM), selenate (Se, sodium selenite 100 μM), and brassinolide (BR, 1.5 μM) treatment induced 6893, 13,287, 13,659 and 11,041 differentially expressed genes (DEGs) in Chinese kale seedlings comparing with control. These genes were associated with pathways of glucosinolates biosynthesis, including phenylalanine, tyrosine and tryptophan biosynthesis, cysteine and methionine metabolism, and glucosinolate biosynthesis. We found NaCl decreased sulforaphane and glucosinolates (indolic and aliphatic) contents and downregulated expression of cytochrome P45083b1 (CYP83b1), S-alkyl-thiohydroximatelyase or carbon–sulfur lyase (SUR1) and UDP-glycosyltransferase 74B1 (UGT74b1). MeJA increased sulforaphane and glucosinolates contents and upregulated the expression of CYP83b1, SUR1 and UGT74b1; Se increased sulforaphane; BR increased expression of CYP83b1, SUR1 and UGT74b1, and increased glucosinolates contents. The desulfoglucosinolate sulfotransferases ST5a_b_c were decreased by all treatments.

Conclusions

We confirmed that NaCl inhibited the biosynthesis of both indolic and aliphatic glucosinolates, while MeJA and BR increased them. MeJA and BR treatments, conferred the biosynthesis of glucosinolates, and Se and MeJA contributed to sulforaphane in Chinese kale via regulating the expression of CYP83b1, SUR1 and UGT74b1.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5758-2) contains supplementary material, which is available to authorized users.

Comparison of the anti-inflammatory effects of Sinapis alba and Brassica juncea in mouse models of inflammation

BACKGROUND

Sinapis Semen is derived from the dried mature seeds of Sinapis alba L. or Brassica juncea (L.) Czern. et Coss. Traditionally, the seeds from S. alba are called "White Sinapis Semen" while those from B. juncea are called "Yellow Sinapis Semen".

PURPOSE

The present study aimed to compare the chemical composition and the anti-inflammatory effects of 50% aqueous ethanol extracts of the White Sinapis Semen (EWSS) and Yellow Sinapis Semen (EYSS) using both acute (12-O-tetradecanoylphorbol-acetate (TPA)- and arachidonic acid (AA)-induced mouse ear edema) and chronic (multiple applications of croton oil (CO)) inflammatory models.

METHODS

The anti-inflammatory effects of EWSS and EYSS were determined by measuring the ear thickness and myeloperoxidase (MPO) activity. The anti-inflammatory mechanism was explored by measuring the protein and mRNA levels of tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-6 in the ear of the TPA-treated mice.

RESULTS

The results showed that both EWSS and EYSS significantly decreased the ear thickness in both the TPA- and AA-induced acute models, as well as in the CO-induced chronic model. In addition, EWSS and EYSS could markedly inhibit the MPO activity in the ears of TPA-, AA- or CO-treated mice. Moreover, EWSS and EYSS also remarkably inhibited the protein and mRNA levels of TNF-α and IL-6 in the ears of TPA-treated mice. Comparatively, EWSS exerted more potent anti-inflammatory effect than that of EYSS.

CONCLUSION

Our results revealed that both EWSS and EYSS are effective anti-inflammatory agents against acute and chronic inflammatory processes, and EWSS possess more potent anti-inflammatory effect than EYSS. The anti-inflammatory effect of the two herbs may be mediated, at least in part, by suppressing the mRNA expression of a panel of inflammatory mediators including TNF-α, IL-6 and IL-1β.

Targeting Colorectal Cancer Proliferation, Stemness and Metastatic Potential Using Brassicaceae Extracts Enriched in Isothiocyanates: A 3D Cell Model-Based Study

Colorectal cancer (CRC) recurrence is often attributable to circulating tumor cells and/or cancer stem cells (CSCs) that resist to conventional therapies and foster tumor progression. Isothiocyanates (ITCs) derived from Brassicaceae vegetables have demonstrated anticancer effects in CRC, however little is known about their effect in CSCs and tumor initiation properties. Here we examined the effect of ITCs-enriched Brassicaceae extracts derived from watercress and broccoli in cell proliferation, CSC phenotype and metastasis using a previously developed three-dimensional HT29 cell model with CSC-like traits. Both extracts were phytochemically characterized and their antiproliferative effect in HT29 monolayers was explored. Next, we performed cell proliferation assays and flow cytometry analysis in HT29 spheroids treated with watercress and broccoli extracts and respective main ITCs, phenethyl isothiocyanate (PEITC) and sulforaphane (SFN). Soft agar assays and relative quantitative expression analysis of stemness markers and Wnt/β-catenin signaling players were performed to evaluate the effect of these phytochemicals in stemness and metastasis. Our results showed that both Brassicaceae extracts and ITCs exert antiproliferative effects in HT29 spheroids, arresting cell cycle at G₂/M, possibly due to ITC-induced DNA damage. Colony formation and expression of LGR5 and CD133 cancer stemness markers were significantly reduced. Only watercress extract and PEITC decreased ALDH1 activity in a dose-dependent manner, as well as β-catenin expression. Our research provides new insights on CRC therapy using ITC-enriched Brassicaceae extracts, specially watercress extract, to target CSCs and circulating tumor cells by impairing cell proliferation, ALDH1-mediated chemo-resistance, anoikis evasion, self-renewal and metastatic potential.

Sulforaphane suppresses the growth of glioblastoma cells, glioblastoma stem cell-like spheroids, and tumor xenografts through multiple cell signaling pathways

OBJECTIVE Defects in the apoptotic machinery and augmented survival signals contribute to drug resistance in glioblastoma (GBM). Moreover, another complexity related to GBM treatment is the concept that GBM development and recurrence may arise from the expression of GBM stem cells (GSCs). Therefore, the use of a multifaceted approach or multitargeted agents that affect specific tumor cell characteristics will likely be necessary to successfully eradicate GBM. The objective of this study was to investigate the usefulness of sulforaphane (SFN)-a constituent of cruciferous vegetables with a multitargeted effect-as a therapeutic agent for GBM. METHODS The inhibitory effects of SFN on established cell lines, early primary cultures, CD133-positive GSCs, GSC-derived spheroids, and GBM xenografts were evaluated using various methods, including GSC isolation and the sphere-forming assay, analysis of reactive oxygen species (ROS) and apoptosis, cell growth inhibition assay, comet assays for assessing SFN-triggered DNA damage, confocal microscopy, Western blot analysis, and the determination of in vivo efficacy as assessed in human GBM xenograft models. RESULTS SFN triggered the significant inhibition of cell survival and induced apoptotic cell death, which was associated with caspase 3 and caspase 7 activation. Moreover, SFN triggered the formation of mitochondrial ROS, and SFN-triggered cell death was ROS dependent. Comet assays revealed that SFN increased single- and double-strand DNA breaks in GBM. Compared with the vehicle control cells, a significantly higher amount of γ-H2AX foci correlated with an increase in DNA double-strand breaks in the SFN-treated samples. Furthermore, SFN robustly inhibited the growth of GBM cell-induced cell death in established cell cultures and early-passage primary cultures and, most importantly, was effective in eliminating GSCs, which play a major role in drug resistance and disease recurrence. In vivo studies revealed that SFN administration at 100 mg/kg for 5-day cycles repeated for 3 weeks significantly decreased the growth of ectopic xenografts that were established from the early passage of primary cultures of GBM10. CONCLUSIONS These results suggest that SFN is a potent anti-GBM agent that targets several apoptosis and cell survival pathways and further preclinical and clinical studies may prove that SFN alone or in combination with other therapies may be potentially useful for GBM therapy.

Cellular and Molecular Mechanisms of 3,3'-Diindolylmethane in Gastrointestinal Cancer

Studies in humans have shown that 3,3′-diindolylmethane (DIM), which is found in cruciferous vegetables, such as cabbage and broccoli, is effective in the attenuation of gastrointestinal cancers. This review presents the latest findings on the use, targets, and modes of action of DIM for the treatment of human gastrointestinal cancers. DIM acts upon several cellular and molecular processes in gastrointestinal cancer cells, including apoptosis, autophagy, invasion, cell cycle regulation, metastasis, angiogenesis, and endoplasmic reticulum (ER) stress. In addition, DIM increases the efficacy of other drugs or therapeutic chemicals when used in combinatorial treatment for gastrointestinal cancer. The studies to date offer strong evidence to support the use of DIM as an anticancer and therapeutic agent for gastrointestinal cancer. Therefore, this review provides a comprehensive understanding of the preventive and therapeutic properties of DIM in addition to its different perspective on the safety of DIM in clinical applications for the treatment of gastrointestinal cancers.

Sulforaphane Preconditioning Sensitizes Human Colon Cancer Cells towards the Bioreductive Anticancer Prodrug PR-104A

The chemoprotective properties of sulforaphane (SF), derived from cruciferous vegetables, are widely acknowledged to arise from its potent induction of xenobiotic-metabolizing and antioxidant enzymes. However, much less is known about the impact of SF on the efficacy of cancer therapy through the modulation of drug-metabolizing enzymes. To identify proteins modulated by a low concentration of SF, we treated HT29 colon cancer cells with 2.5 μM SF. Protein abundance changes were detected by stable isotope labeling of amino acids in cell culture. Among 18 proteins found to be significantly up-regulated, aldo-keto reductase 1C3 (AKR1C3), bioactivating the DNA cross-linking prodrug PR-104A, was further characterized. Preconditioning HT29 cells with SF reduced the EC50 of PR-104A 3.6-fold. The increase in PR-104A cytotoxicity was linked to AKR1C3 abundance and activity, both induced by SF in a dose-dependent manner. This effect was reproducible in a second colon cancer cell line, SW620, but not in other colon cancer cell lines where AKR1C3 abundance and activity were absent or barely detectable and could not be induced by SF. Interestingly, SF had no significant influence on PR-104A cytotoxicity in non-cancerous, immortalized human colonic epithelial cell lines expressing either low or high levels of AKR1C3. In conclusion, the enhanced response of PR-104A after preconditioning with SF was apparent only in cancer cells provided that AKR1C3 is expressed, while its expression in non-cancerous cells did not elicit such a response. Therefore, a subset of cancers may be susceptible to combined food-derived component and prodrug treatments with no harm to normal tissues.

Glucosinolates, myrosinase hydrolysis products, and flavonols found in rocket (Eruca sativa and Diplotaxis tenuifolia)

Rocket species have been shown to have very high concentrations of glucosinolates and flavonols, which have numerous positive health benefits with regular consumption. This review highlights how breeders and processors of rocket species can utilize genomic and phytochemical research to improve varieties and enhance the nutritive benefits to consumers. Plant breeders are increasingly looking to new technologies such as HPLC, UPLC, LC-MS, and GC-MS to screen populations for their phytochemical content to inform plant selections. This paper collates the research that has been conducted to date in rocket and summarizes all glucosinolate and flavonol compounds identified in the species. The paper emphasizes the importance of the broad screening of populations for phytochemicals and myrosinase degradation products, as well as unique traits that may be found in underutilized gene bank resources. This review also stresses that collaboration with industrial partners is becoming essential for long-term plant breeding goals through research.

Dietary cyclic dipeptides, apoptosis and psychiatric disorders: a hypothesis

Cyclic dipeptides from food and intestinal yeast cyclic dipeptides may play a role in causing psychiatric disorders such as schizophrenia. From cancer research, cyclic dipeptides such as cyclo (proline-phenylalanine) have been found to activate the pathways of apoptosis and to cause programmed cell death. Activation of such pathways is also thought to be important in causing the neurodevelopmental abnormalities seen in disorders such as schizophrenia and autistic disorder, and also may be important in Alzheimer's. Cyclic dipeptides are found in foods such as malt and cocoa and beer. The intestinal yeast Candida albicans also synthesizes cyclic dipeptides. These dipeptides may be activating apoptosis pathways throughout fetal development and postnatal development, leading to some of the changes seen in brain in schizophrenia and in other psychiatric disorders. These compounds should be researched further to see if they play a role in causing these brain changes. In addition, these cyclic dipeptides are considered within the larger context of research on amino acids and other cyclic dipeptides in neurotransmission and neurophysiology. A better understanding of the role of these cyclic dipeptides in psychiatric disorders could lead to strategies for prevention and treatment of these disorders.

Sulforaphane as a promising molecule for fighting cancer

Cancer is a complex disease characterized by multiple genetic and molecular alterations involving transformation, deregulation of apoptosis, proliferation, invasion, angiogenesis, and metastasis. To grow, invade, and metastasize, tumors need host components and primary dysfunction in the tumor microenvironment, in addition to cell dysfunction, can be crucial for carcinogenesis. A great variety of phytochemicals have been shown to be potentially capable of inhibiting and modulating several relevant targets simultaneously and is therefore non-specific. Because of the enormous biological diversity of cancer, this pleiotropism might constitute an advantage. Phytochemicals, in particular diet-derived compounds, have therefore been proposed and applied in clinical trials as cancer chemopreventive/chemotherapeutic agents. Sulforaphane (SFN) is an isothiocyanate found in cruciferous vegetables. SFN has proved to be an effective chemoprotective agent in cell culture, in carcinogen-induced and genetic animal cancer models, as well as in xenograft models of cancer. It promoted potent cytostatic and cytotoxic effects orchestrated by the modulation of different molecular targets. Cell vulnerability to SFN-mediated apoptosis was subject to regulation by cell-cycle-dependent mechanisms but was independent of a mutated p53 status. Moreover, combination of SFN with cytotoxic therapy potentiated the cytotoxic effect mediated by chemotherapy in vitro, thus suggesting its potential therapeutic benefit in clinical settings. Overall, SFN appears to be an effective and safe chemopreventive molecule and a promising tool to fight cancer.

Insights into the mode of action of benzyl isothiocyanate on Campylobacter jejuni

Campylobacter jejuni is a widespread pathogen responsible for most of the food-borne gastrointestinal diseases in Europe. The use of natural antimicrobial molecules is a promising alternative to antibiotic treatments for pathogen control in the food industry. Isothiocyanates are natural antimicrobial compounds, which also display anticancer activity. Several studies described the chemoprotective effect of isothiocyanates on eukaryotic cells, but the antimicrobial mechanism is still poorly understood. We investigated the early cellular response of C. jejuni to benzyl isothiocyanate by both transcriptomic and physiological approaches. The transcriptomic response of C. jejuni to benzyl isothiocyanate showed upregulation of heat shock response genes and an impact on energy metabolism. Oxygen consumption was progressively impaired by benzyl isothiocyanate treatment, as revealed by high-resolution respirometry, while the ATP content increased soon after benzyl isothiocyanate exposition, which suggests a shift in the energy metabolism balance. Finally, benzyl isothiocyanate induced intracellular protein aggregation. These results indicate that benzyl isothiocyanate affects C. jejuni by targeting proteins, resulting in the disruption of major metabolic processes and eventually leading to cell death.

Preclinical evaluation of 4-methylthiobutyl isothiocyanate on liver cancer and cancer stem cells with different p53 status

Isothiocyanates from plants of the order Brassicales are considered promising cancer chemotherapeutic phytochemicals. However, their selective cytotoxicity on liver cancer has been barely researched. Therefore, in the present study, we systematically studied the chemotherapeutic potency of 4-methylthiobutyl isothiocyanate (MTBITC). Selective toxicity was investigated by comparing its effect on liver cancer cells and their chemoresistant subpopulations to normal primary hepatocytes and liver tissue slices. Additionally, in a first assessment, the in vivo tolerability of MTBITC was investigated in mice. Growth arrest at G2/M and apoptosis induction was evident in all in vitro cancer models treated with MTBITC, including populations with cancer initiating characteristics. This was found independent from TP53; however cell death was delayed in p53 compromised cells as compared to wt-p53 cells which was probably due to differential BH3 only gene regulation i. e. Noxa and its antagonist A1. In normal hepatocytes, no apoptosis or necrosis could be detected after repeated administration of up to 50 µM MTBITC. In mice, orally applied MTBITC was well tolerated over 18 days of treatment for up to 50 mg/kg/day, the highest dose tested. In conclusion, we could show here that the killing effect of MTBITC has a definite selectivity for cancer cells over normal liver cells and its cytotoxicity even applies for chemoresistant cancer initiating cells. Our study could serve for a better understanding of the chemotherapeutic properties of isothiocyanates on human liver-derived cancer cells.

Selenium influences glucosinolate and isothiocyanates and increases sulfur uptake in Arabidopsis thaliana and rapid-cycling Brassica oleracea

This study investigated the impact of Se on glucosinolates (GSs) and isothiocyanates (ITCs). Plants of Arabidopsis thaliana cv. Columbia and a rapid-cycling base population of Brassica oleracea were grown hydroponically under different Se and S concentrations. The objective was to determine the effects of increasing Se and S concentrations on the GSs and ITCs. The results indicate that S and Se concentrations increased in A. thaliana and B. oleracea leaf tissue in response to increasing Se treatments. Aliphatic and total GSs decreased significantly (P ≤ 0.001) from 0.0 to 3.2 mg Se L(-1) in B. oleracea and A. thaliana leaf tissues. Consequently, aliphatic and total ITCs decreased significantly (P ≤ 0.001) from 0.0 to 3.2 mg Se L(-1) in B. oleracea and A. thaliana leaf tissues. Data demonstrate that high levels of anticarcinogenic GSs can be maintained as the Se concentration is increased to 0.8 mg L(-1). Thus, it is feasible to increase Se to beneficial dietary levels without compromising GS concentrations.

Sulforaphane inhibits prostaglandin E2 synthesis by suppressing microsomal prostaglandin E synthase 1

Sulforaphane (SFN) is a dietary cancer preventive with incompletely characterized mechanism(s) of cancer prevention. Since prostaglandin E2 (PGE2) promotes cancer progression, we hypothesized that SFN may block PGE2 synthesis in cancer cells. We found that SFN indeed blocked PGE2 production in human A549 cancer cells not by inhibiting COX-2, but rather by suppressing the expression of microsomal prostaglandin E synthase (mPGES-1), the enzyme that directly synthesizes PGE2. We identified the Hypoxia Inducible Factor 1 alpha (HIF-1α) as the target of SFN-mediated mPGES-1 suppression. SFN suppressed HIF-1α protein expression and the presence of HIF-1α at the mPGES-1 promoter, resulting in reduced transcription of mPGES-1. Finally, SFN also reduced expression of mPGES-1 and PGE2 production in A549 xenograft tumors in mice. Together, these results point to the HIF-1α, mPGES-1 and PGE2 axis as a potential mediator of the anti-cancer effects of SFN, and illustrate the potential of SFN for therapeutic control of cancer and inflammation. Harmful side effects in patients taking agents that target the more upstream COX-2 enzyme render the downstream target mPGES-1 a significant target for anti-inflammatory therapy. Thus, SFN could prove to be an important therapeutic approach to both cancer and inflammation.

Evaluation of antiulcer activity of indole-3-carbinol and/or omeprazole on aspirin-induced gastric ulcer in rats

The present work is an attempt to elucidate the antiulcer activity of indole-3-carbinol (I3C), which is one of the anticarcinogenic phytochemicals found in the vegetables of Cruciferae family such as broccoli and cauliflower, alone or in combination with omeprazole (OMP), a proton pump inhibitor, to diminish the effects of induced acute gastric ulcer by aspirin (ASA) in male albino rats. A total of 48 adult male albino rats were used in the present study. Animals were divided into eight experimental groups (six animals each group). They were given different experimental inductions of ASA at a dose of 500 mg/kg/body weight, OMP at a dose of 20 mg/kg/body weight and I3C at a dose of 20 mg/kg/body weight either alone or in combination with each other orally for a duration of 7 days. Inner stomach features, ulcer index, pH activity, body weight, stomach weight, hematological investigations, serum total protein albumin and reduced glutathione activity  were investigated in addition to the histological, histochemical and immunohistochemical stain of cyclooxygenase-2 to the stomach tissue of normal control, ulcerated and treated ulcerated rats. The results of this study revealed that oral administration of ASA to rats produced the expected characteristic mucosal lesions. OMP accelerated ulcer healing but the administration of I3C either alone or in combination with OMP to ASA-ulcerated rats produced a profound protection to the gastric mucosa from injury induced by ASA. Our results suggested that administration of antiulcer natural substances such as I3C in combination with the perused treatment such as OMP is a very important initiative in the development of new strategies in ulcer healing.

Role of 4-hydroxynonenal in chemopreventive activities of sulforaphane

Chemoprevention of cancer via herbal and dietary supplements is a logical approach to combating cancer and currently it is an attractive area of research investigation. Over the years, isothiocyanates, such as sulforaphane (SFN) found in cruciferous vegetables, have been advocated as chemopreventive agents, and their efficacy has been demonstrated in cell lines and animal models. In vivo studies with SFN suggest that in addition to protecting normal healthy cells from environmental carcinogens, it also exhibits cytotoxicity and apoptotic effects against various cancer cell types. Among several mechanisms for the chemopreventive activity of SFN against chemical carcinogenesis, its effect on drug-metabolizing enzymes that cause activation/neutralization of carcinogenic metabolites is well established. Recent studies suggest that SFN exerts its selective cytotoxicity to cancer cells via reactive oxygen species-mediated generation of lipid peroxidation products, particularly 4-hydroxynonenal (HNE). Against the background of the known biochemical effects of SFN on normal and cancer cells, in this article we review the underlying molecular mechanisms responsible for the overall chemopreventive effects of SFN, focusing on the role of HNE in these mechanisms, which may also contribute to its selective cytotoxicity to cancer cells.

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.

A Novel pH-Sensitive Microsphere Composed of CM-Chitosan and Alginate for Sulforaphane Delivery

Sulforaphane (SF) has been proved to be an effective anticancer agent according to its experiments bothin vitroandin vivo. To date, there is few reported method to deliver SF for increasing its bioactivity and stability. In this study, a novel pH-sensitive microsphere composed of water-soluble carboxymethylated chitosan (CMCS) and alginate mixed with sodium sulfate was developed for SF delivery. Swelling studies and release characteristics under different pH values of microspheres were investigated. Then, the release of SF from test microspheres was studied in simulated gastric and segmented intestinal media. It has been found that the SF cumulated release in 5h was increased from 55.89% to 76.73% when the microspheres mixed with sodium sulfate. In addition, the stability of SF embedded in CMCS/alginate microspheres was also significantly improved. Under pH 7.4, free SF had a severe degradation of approximate 100% within 210 min, whereas the change of the SF in microspheres was only a decrease of about 10%. The results suggested that the microspheres of CMCS and alginate could be a suitable pH-sensitive carrier to increase the stability of SF in the segmented intestine.

3,3'-Diindolylmethane but not indole-3-carbinol activates Nrf2 and induces Nrf2 target gene expression in cultured murine fibroblasts

There is increasing interest in the gene-regulatory activity of Brassica vegetable derived phytochemicals such as 3,3'-diindolylmethane (DIM) and indole-3-carbinol (I3C). DIM is formed under acidic conditions by dimerization of I3C. This study compared the Nrf2 activating potential of DIM and I3C in murine fibroblasts (NIH3T3). In contrast to its precursor I3C, DIM induces the transactivation of Nrf2. Furthermore, Nrf2 targets such as HO-1, γGCS and NQO1 were increased on the mRNA and protein levels following DIM treatment. DIM was less potent than sulforaphane (used as positive control) in inducing Nrf2-dependent gene expression. The present data suggest that the dimerization of I3C to DIM increases its Nrf2 inducing activity.

Glucosinolates in Brassica vegetables: the influence of the food supply chain on intake, bioavailability and human health

Glucosinolates (GLSs) are found in Brassica vegetables. Examples of these sources include cabbage, Brussels sprouts, broccoli, cauliflower and various root vegetables (e.g. radish and turnip). A number of epidemiological studies have identified an inverse association between consumption of these vegetables and the risk of colon and rectal cancer. Animal studies have shown changes in enzyme activities and DNA damage resulting from consumption of Brassica vegetables or isothiocyanates, the breakdown products (BDP) of GLSs in the body. Mechanistic studies have begun to identify the ways in which the compounds may exert their protective action but the relevance of these studies to protective effects in the human alimentary tract is as yet unproven. In vitro studies with a number of specific isothiocyanates have suggested mechanisms that might be the basis of their chemoprotective effects. The concentration and composition of the GLSs in different plants, but also within a plant (e.g. in the seeds, roots or leaves), can vary greatly and also changes during plant development. Furthermore, the effects of various factors in the supply chain of Brassica vegetables including breeding, cultivation, storage and processing on intake and bioavailability of GLSs are extensively discussed in this paper.

Sulforaphane destabilizes the androgen receptor in prostate cancer cells by inactivating histone deacetylase 6

High consumption of cruciferous vegetables is associated with a reduced risk of prostate cancer in epidemiological studies. There is preliminary evidence that sulforaphane, derived from glucoraphanin found in a number of crucifers, may prevent and induce regression of prostate cancer and other malignancies in preclinical models, but the mechanisms that may explain these effects are not fully defined. Recent reports show that sulforaphane may impair prostate cancer growth through inhibition of histone deacetylases, which are up-regulated in cancer. Indeed, one of these enzymes, histone deacetylase 6 (HDAC6), influences the acetylation state of a key androgen receptor (AR) chaperone, HSP90. AR is the central signaling pathway in prostate cancer, and its inhibition is used for both prevention and treatment of this disease. However, it is not known whether the effects of sulforaphane involve suppression of AR. We hypothesized that sulforaphane treatment would lead to hyperacetylation of HSP90 and that this would destabilize AR and attenuate AR signaling. We confirmed this by demonstrating that sulforaphane enhances HSP90 acetylation, thereby inhibiting its association with AR. Moreover, AR is subsequently degraded in the proteasome, which leads to reduced AR target gene expression and reduced AR occupancy at its target genes. Finally, sulforaphane inhibits HDAC6 deacetylase activity, and the effects of sulforaphane on AR protein are abrogated by overexpression of HDAC6 and mimicked by HDAC6 siRNA. The inactivation by sulforaphane of HDAC6-mediated HSP90 deacetylation and consequent attenuation of AR signaling represents a newly defined mechanism that may help explain this agent's effects in prostate cancer.

Induction of G1 and G2/M cell cycle arrests by the dietary compound 3,3'-diindolylmethane in HT-29 human colon cancer cells

Background

3,3'-Diindolylmethane (DIM), an indole derivative produced in the stomach after the consumption of broccoli and other cruciferous vegetables, has been demonstrated to exert anti-cancer effects in both in vivo and in vitro models. We have previously determined that DIM (0 – 30 μmol/L) inhibited the growth of HT-29 human colon cancer cells in a concentration-dependent fashion. In this study, we evaluated the effects of DIM on cell cycle progression in HT-29 cells.

Methods

HT-29 cells were cultured with various concentrations of DIM (0 – 30 μmol/L) and the DNA was stained with propidium iodide, followed by flow cytometric analysis. [³H]Thymidine incorporation assays, Western blot analyses, immunoprecipitation and in vitro kinase assays for cyclin-dependent kinase (CDK) and cell division cycle (CDC)2 were conducted.

Results

The percentages of cells in the G1 and G2/M phases were dose-dependently increased and the percentages of cells in S phase were reduced within 12 h in DIM-treated cells. DIM also reduced DNA synthesis in a dose-dependent fashion. DIM markedly reduced CDK2 activity and the levels of phosphorylated retinoblastoma proteins (Rb) and E2F-1, and also increased the levels of hypophosphorylated Rb. DIM reduced the protein levels of cyclin A, D1, and CDK4. DIM also increased the protein levels of CDK inhibitors, p21^CIP1/WAF1 and p27^KIPI. In addition, DIM reduced the activity of CDC2 and the levels of CDC25C phosphatase and cyclin B1.

Conclusion

Here, we have demonstrated that DIM induces G1 and G2/M phase cell cycle arrest in HT-29 cells, and this effect may be mediated by reduced CDK activity.

MTBITC mediates cell cycle arrest and apoptosis induction in human HepG2 cells despite its rapid degradation kinetics in the in vitro model

Despite the great variety of structure homologous, experimental research on the cancer preventive properties of isothiocyanates (ITCs) is limited to only a fractional amount thereof so far. Especially the degradation of these compounds in the experimental system has not been investigated so far. In this study, we investigated the effect of 4-methylthiobutyl isothiocyante (MTBITC) on the proliferation of human hepatoma (HepG2) cells and underlying mechanisms. A concentration and time-dependent reduction in proliferation activity could be observed in cells treated with MTBITC exceeding 10 microM. At these concentrations MTBITC-induced apoptosis in HepG2 cells could be observed by internucleosomal DNA fragmentation, flow cytometry analysis, and the detection of single-stranded apoptotic DNA. In all the three assays, clear apoptotic events were present after 6-hr exposure to MTBITC. Apoptosis induction was accompanied by a time-dependent arrest of HepG2 cells at the G2/M phase of the cell cycle. This study shows for the first time the inhibitory potency of MTBITC on metabolically competent hepatoma cells, whereas the loss of reduced glutathione and its impact on mitochondria seem to be the major processes involved in the initiation and execution of the apoptotic cell death. The results of this study also showed that irrespective of the intense degradation kinetics of MTBITC, the strong cytostatic effect of the ITC was not markedly affected by it and suggests that although ITCs are only present at maximum concentrations in a living system for a rather short time, this might be sufficient to exert their therapeutic effects.

Apoptosis induction by sulfur-containing compounds in malignant and nonmalignant human cells

Plants have traditionally represented a main source for the discovery of many biologically active substances with therapeutic values. Sulfur-containing compounds exhibit pleiotropic biological effects supporting their potential use in multitargeted cancer prevention and treatment. As potential anti-cancer agents, they have been shown to inhibit or retard the growth of various cancer cells in culture and implanted tumors in vivo. The compounds significantly inhibit experimental tumorigenesis in a wide range of animal models. A critical and well-elucidated cellular mechanism involved in the anticancer activities of sulfur-containing compounds is the induction of apoptosis through the fine-tuning of orchestrated intracellular signal transduction. This review summarizes the established proapoptotic activities of sulfur-containing compounds in malignant and nonmalignant cells with a special focus on their molecular mechanisms. The potential toxicological implications of proapoptotic effects on normal cells will also be discussed.

Sulforaphane induces cell-cycle arrest and apoptosis in cultured human lung adenocarcinoma LTEP-A2 cells and retards growth of LTEP-A2 xenografts in vivo

Sulforaphane (1), a glucosinolate-derived isothiocyanate found in the cruciferous vegetable broccoli, is considered an anticarcinogenic component. In the present study, the proliferation and apoptosis induction in human lung adenocarcinoma LTEP-A2 cells by 1 was investigated. Compound 1 caused G(2)/M-phase arrest (p < 0.05) and increase of apoptotic cell fraction (p < 0.05) in a time- and dose-dependent manner. Intraperitoneal injection of 1 significantly inhibited growth of LTEP-A2 xenografts in nude mice, and 9 days after tumor cell implantation with 100 mg/kg intraperitoneal injection of 1, the average tumor weights in 1-treated mice was >70% lower than that of the control mice.

Application of high-speed countercurrent chromatography for the isolation of sulforaphane from broccoli seed meal

In order to produce large amounts of pure sulforaphane for research purposes, a novel method using high-speed countercurrent chromatography (HSCCC) was developed. Without any initial cleanup steps, sulforaphane was successfully purified from the ethyl acetate extract of the broccoli seed meal by HSCCC. The separation was performed with two-phase solvent systems: n-hexane/ethyl acetate/methanol/water (1:5:1:5, v/v/v/v). From 850 mg of the ethyl acetate extract, 186 mg of sulforaphane was isolated with the solvent system. The purified compound was over 97% purity as determined by HPLC analysis, and the chemical structure was confirmed by MS and (1)H and (13)C NMR.

Biphasic modulation of cell proliferation by sulforaphane at physiologically relevant exposure times in a human colon cancer cell line

Sulforaphane (SFN), a cancer chemopreventive compound derived from broccoli, is able to induce cell cycle arrest and apoptosis in various tumor cell lines. Here we show that cell growth inhibition by SFN follows a biphasic pattern: Transient exposure of 40-16 human colon carcinoma cells for up to 6 h resulted in reversible G(2)/M cell cycle arrest and cytostatic growth inhibition even at elevated concentrations, whereas a minimum continuous exposure time of 12 h was necessary for SFN to irreversibly arrest cells in G(2)/M phase and subsequently induce apoptosis. IC(50) values after 12 h of exposure followed by drug-free recovery up to 72 h (6.4-8.1 microM) were indistinguishable from those of chronic exposure for 24 to 72 h (5.4-6.6 microM). Low concentrations of SFN caused a transient decrease in glutathione (GSH) levels followed by GSH induction, which may be related to reversible G(2)/M arrest and cytostatic effects. Depletion of GSH does not seem to play a role in SFN-mediated apoptosis induction. Our data clearly contribute to a better understanding of the kinetics of antiproliferative activity of SFN.

Separation and purification of sulforaphane from broccoli seeds by solid phase extraction and preparative high-performance liquid chromatography

A novel, rapid, and economical method to isolate and purify natural sulforaphane from broccoli seeds is described. The procedure involves solvent extraction of autolyzed seed meal, followed by separation by solid phase extraction (SPE) and purification by preparative high-performance liquid chromatography (HPLC). The SPE method provides higher yield of sulforaphane from crude extracts compared to conventional liquid-liquid extraction. High purity and recovery of sulforaphane product can be obtained by preparative HPLC with a C 18 column and 30% methanol in water as the mobile phase. The purified compound was characterized by MS and (1)H and (13)C NMR. The techniques described here are useful tools in the preparative-scale isolation of sulforaphane in a fast, cost-effective, and waste-conscious manner.

Predicting the physiological relevance of in vitro cancer preventive activities of phytochemicals

There is growing interest in the ability of phytochemicals to prevent chronic diseases, such as cancer and heart disease. However, some of these agents have poor bioavailability and many of the in-depth studies into their mechanisms of action have been carried out in vitro using doses which are unachievable in humans. In order to optimize the design of chemopreventive treatment, it is important to determine which of the many reported mechanisms of action are clinically relevant. In this review we consider the physiologically achievable doses for a few of the best studied agents (indole-3-carbinol, diindolylmethane, curcumin, epigallocatechin-3-gallate and resveratrol) and summarize the data derived from studies using these low concentrations in cell culture. We then cite examples of in vitro effects which have been observed in vivo. Finally, the ability of agent combinations to act synergistically or antagonistically is considered. We conclude that each of the compounds shows an encouraging range of activities in vitro at concentrations which are likely to be physiologically relevant. There are also many examples of in vivo studies which validate in vitro observations. An important consideration is that combinations of agents can result in significant activity at concentrations where any single agent is inactive. Thus, for each of the compounds reviewed here, in vitro studies have provided useful insights into their mechanisms of action in humans. However, data are lacking on the full range of activities at low doses in vitro and the benefits or otherwise of combinations in vivo.

Sulforaphane induces cell type–specific apoptosis in human breast cancer cell lines

Sulforaphane, an isothiocyanate found in cruciferous vegetables, has been shown to induce phase 2 detoxication enzymes and inhibit the growth of chemically induced mammary tumors in rats, although the exact mechanisms of action of sulforaphane are not understood. In this study, we evaluated the effects of sulforaphane on cell growth and death in several human breast cancer cell lines and examined the hypothesis that sulforaphane acts as a histone deacetylase (HDAC) inhibitor in these cell lines. Sulforaphane treatment inhibited cell growth, induced a G(2)-M cell cycle block, increased expression of cyclin B1, and induced oligonucleosomal DNA fragmentation in the four human breast cancer cell lines examined, MDA-MB-231, MDA-MB-468, MCF-7, and T47D cells. Activation of apoptosis by sulforaphane in MDA-MB-231 cells seemed to be initiated through induction of Fas ligand, which resulted in activation of caspase-8, caspase-3, and poly(ADP-ribose) polymerase, whereas apoptosis in the other breast cancer cell lines was initiated by decreased Bcl-2 expression, release of cytochrome c into the cytosol, activation of caspase-9 and caspase-3, but not caspase-8, and poly(ADP-ribose) polymerase cleavage. Sulforaphane inhibited HDAC activity and decreased the expression of estrogen receptor-alpha, epidermal growth factor receptor, and human epidermal growth factor receptor-2 in each cell line, although no change in the acetylation of H3 or H4 was seen. These data suggest that sulforaphane inhibits cell growth, activates apoptosis, inhibits HDAC activity, and decreases the expression of key proteins involved in breast cancer proliferation in human breast cancer cells. These results support testing sulforaphane in vivo and warrant future studies examining the clinical potential of sulforaphane in human breast cancer.

Comparison of growth inhibition profiles and mechanisms of apoptosis induction in human colon cancer cell lines by isothiocyanates and indoles from Brassicaceae

The isothiocyanates sulforaphane and PEITC (beta-phenethyl isothiocyanate) as well as the indoles indole-3-carbinol and its condensation product 3,3'-diindolylmethane are known to inhibit cancer cell proliferation and induce apoptosis. In this study, we compared the cell growth inhibitory potential of the four compounds on the p53 wild type human colon cancer cell line 40-16 (p53(+/+)) and its p53 knockout derivative 379.2 (p53(-/-)) (both derived from HCT116). Using sulforhodamin B staining to assess cell proliferation, we found that the isothiocyanates were strongly cytotoxic, whereas the indoles inhibited cell growth in a cytostatic manner. Half-maximal inhibitory concentrations of all four compounds in both cell lines ranged from 5-15 microM after 24, 48 and 72 h of treatment. Apoptosis induction was analyzed by immunoblotting of poly(ADP-ribose)polymerase (PARP). Treatment with sulforaphane (15 microM), PEITC (10 microM), indole-3-carbinol (10 microM) and 3,3'-diindolylmethane (10 microM) induced PARP cleavage after 24 and 48 h in both 40-16 and the 379.2 cell lines, suggestive of a p53-independent mechanism of apoptosis induction. In cultured 40-16 cells, activation of caspase-9 and -7 detected by Western blotting indicated involvement of the mitochondrial pathway. We detected time- and concentration-dependent changes in protein expression of anti-apoptotic Bcl-x(L) as well as pro-apoptotic Bax and Bak proteins. Of note is that for sulforaphane only, ratios of pro- to anti-apoptotic Bcl-2 family protein levels directly correlated with apoptosis induction measured by PARP cleavage. Taken together, we demonstrated that the glucosinolate breakdown products investigated in this study have distinct profiles of cell growth inhibition, potential to induce p53-independent apoptosis and to modulate Bcl-2 family protein expression in human colon cancer cell lines.

Sulforaphane suppresses angiogenesis and disrupts endothelial mitotic progression and microtubule polymerization

Sulforaphane (SUL), an isothiocyanate derived from broccoli and other cruciferous vegetables, is known to induce phase II detoxification enzymes, disrupt cancer cell microtubule polymerization, and trigger cell cycle arrest in breast and colon cancer cells. Here, we provide the first evidence that SUL also acts to inhibit angiogenesis via suppression of endothelial cell proliferation. Bovine aortic endothelial (BAE) cells were exposed to concentrations of up to 15 microM SUL prior to cell cycle analysis and mitotic index quantification. Within 24 h, 15 microM SUL clearly induced G(2)/M accumulation and pre-metaphase arrest in BAE cells. Moreover, immunofluorescence tubulin staining indicated that this same SUL concentration was efficacious in not only disrupting mitotic progression, but also in perturbing normal polymerization of mitotic (and cytoplasmic) microtubules. Furthermore, daily administration of SUL (100 nmol/day, i.v. for 7 days) to female Balb/c mice bearing VEGF-impregnated Matrigel plugs strongly and significantly (P<0.05) suppressed angiogenesis progression as measured by hemoglobin concentration. Taken together, these findings suggest that the endothelial cell population is a novel target of SUL action both in vitro and in vivo. This mechanism of SUL-induced endothelial microtubule disruption and early mitotic arrest may further discern a potential role of SUL as a chemopreventive agent.

Vegetable-derived isothiocyanates: anti-proliferative activity and mechanism of action

Many isothiocyanates (ITC), which are available to human subjects mainly through consumption of cruciferous vegetables, demonstrate strong cancer-preventive activity in animal models. Human studies also show an inverse association between consumption of ITC and risk of cancer in several organs. Whereas earlier studies primarily focused on the ability of ITC to inhibit carcinogen-activating enzymes and induce carcinogen-detoxifying enzymes, more recent investigations have shown that ITC inhibit the proliferation of tumour cells both in vitro and in vivo by inducing apoptosis and arresting cell cycle progression. ITC cause acute cellular stress, which may be the initiating event for these effects. These findings shed new light on the mechanism of action of ITC and indicate that ITC may be useful both as cancer-preventive and therapeutic agents. ITC activate caspase 9-mediated apoptosis, apparently resulting from mitochondrial damage, and also activate caspase 8, but the mechanism remains to be defined. Cell cycle arrest caused by ITC occurs mainly in the G2/M phase, and both the G2 and M phases are targetted; critical G2-phase regulators, including cyclin B1, cell division cycle (Cdc) 2 and Cdc25C, are down regulated or inhibited, and tubulin polymerization and spindle assembly are disrupted. Moreover, ITC are metabolized in vivo through the mercapturic acid pathway, giving rise to thiol conjugates (dithiocarbamates). Studies show that these dithiocarbamates are similar to their parent ITC in exerting anti-proliferative activity. Taken together, dietary ITC are highly-promising anti-cancer agents, capable of targetting multiple cellular components that are important for tumour cell survival and proliferation.

Chemoprotection by sulforaphane: keep one eye beyond Keap1

Sulforaphane (SFN) is an isothiocyanate found in cruciferous vegetables, with particularly high levels detected in broccoli and broccoli sprouts. Over a decade ago, this phytochemical was identified as a likely chemopreventive agent based on its ability to induce Phase 2 detoxification enzymes, as well as to inhibit Phase 1 enzymes involved in carcinogen activation. Considerable attention has focused on SFN as a 'blocking' agent, with the ability to modulate the Nrf2/Keap1 pathway, but recent evidence suggests that SFN acts by numerous other mechanisms. SFN induces cell cycle arrest and apoptosis in cancer cells, inhibits tubulin polymerization, activates checkpoint 2 kinase, and inhibits histone deacetylase activity. The latter findings suggest that SFN may be effective during the post-initiation stages of carcinogenesis, as a 'suppressing' agent. Moreover, pharmacological administration of SFN may be a promising therapeutic approach to the treatment of cancers, including those characterized by increased inflammation and involving viral or bacterial-related pathologies. The present review discusses the more widely established chemoprotective mechanisms of SFN, but makes the case for additional work on mechanisms that might be of importance during later stages of carcinogenesis, beyond Keap1.