Multi-targeted prevention of cancer by sulforaphane

Antimutagenic potential of glucosinolate-rich seed extracts of broccoli (Brassica oleracea L var italica Plenck)

In the current study, isolation of glucosinolate degradation products was done in 4 different incubation solutions with different pHs based on the fact that distinct hydrolytic products are formed at different pHs. All the extracts were tested against direct-acting mutagens (4 nitro-o-phenylenediamine [NPD]), sodium azide, and indirect-acting mutagen (2-aminofluorene [2AF]). It was observed that extracts inhibited mutagenesis induced by the S9-dependent mutagen (2AF) more significantly than direct-acting mutagens. Two different modes of experimentation (pre-incubation and co-incubation) were used, and it was observed that the extracts showed better results in the pre-incubation mode of experimentation. Out of the 4 extracts tested, 0.1 mol/L of HCl extract was found to be the most effective in inhibiting mutagenesis with both TA 98 and TA 100 strains of Salmonella typhimurium. All other extracts also showed pronounced antimutagenic potential. The results of this study indicate the presence of potent antigenotoxic factors in broccoli, which are being explored further for their mechanism of action.

Cruciferous vegetable intake and lung cancer risk: a nested case-control study matched on cigarette smoking

BACKGROUND

Due predominantly to cigarette smoking, lung cancer is the leading cancer-related cause of death worldwide. Cruciferous vegetables may reduce lung cancer risk. The association between intake of cruciferous vegetables and lung cancer risk was investigated in the CLUE II study, a community-based cohort established in 1989.

METHODS

We matched 274 incident cases of lung cancer diagnosed from 1990 to 2005 to 1,089 cancer-free controls on age, sex, and cigarette smoking. Dietary information was collected at baseline. Multivariable odds ratios (OR) and 95% confidence intervals (95% CI) were calculated using conditional logistic regression.

RESULTS

Intake of cruciferous vegetables was inversely associated with lung cancer risk (highest-versus-lowest fourth: OR (Q4vsQ1), 0. 57; 95% CI, 0.38-0.85; P-trend = 0.01). The inverse associations held true for former smokers (OR(Q4vsQ1), 0.49; 95% CI, 0.27-0.92; P-trend = 0.05) and current smokers (OR(Q4vsQ1), 0.52; 95% CI, 0.29-0.95; P-trend = 0.02).

CONCLUSIONS

After carefully controlling for cigarette smoking, higher intake of cruciferous vegetable was associated with lower risk of lung cancer.

IMPACT

The observed inverse association coupled with accumulating evidence suggests that intake of cruciferous vegetables is inversely associated with lung cancer risk, and this association seems to hold true beyond the confounding effects of cigarette smoking.

Epigenetic tools in potential anticancer therapy

Human cancer represents a heterogeneous group of diseases that are driven by progressive genetic and epigenetic abnormalities. The latter alterations involve hypermethylation and hypomethylation of DNA, and changed patterns of histone modification, with resultant remodeling of the chromatin structure that cause deregulation of the transcription activity of many genes. Unlike the remarkable progress in understanding the processes by which DNA methyltransferases can regulate gene expression and histone deacetylases can induce alteration of chromatin structure, the roles of epigenetic events in tumors remain insufficiently explained. In contrast to genetic changes, the epigenetic alterations in cancer cells can be reversed by the inhibition of DNA methylation and histone deacetylation. Therefore, many inhibition agents for re-expression, predominantly of tumor-suppressor genes, have been identified and tested in laboratory models and numerous clinical trials. Despite in-vitro evidence that a single drug can lead to reactivation of methylated genes, inhibitors of DNA methyltransferases and histone deacetylases have been investigated in combination, or together with cytotoxic chemotherapy, radiotherapy, immunotherapy, or hormonal therapy to improve the therapeutic effect. Ongoing trials are recognizing that the identification of a target group of patients who are more likely to respond to the epigenetic therapy, defining of an optimal dose and schedule of treatment, and the development of more specific inhibitors with minimal unwanted side effects are necessary. Thus, new combinations of anticancer agents, including epigenetic modulators, may lead to a more effective control of cancer.

In vivo modulation of 4E binding protein 1 (4E-BP1) phosphorylation by watercress: a pilot study

Dietary intake of isothiocyanates (ITC) has been associated with reduced cancer risk. The dietary phenethyl ITC (PEITC) has previously been shown to decrease the phosphorylation of the translation regulator 4E binding protein 1 (4E-BP1). Decreased 4E-BP1 phosphorylation has been linked to the inhibition of cancer cell survival and decreased activity of the transcription factor hypoxia-inducible factor (HIF), a key positive regulator of angiogenesis, and may therefore contribute to potential anti-cancer effects of PEITC. In the present study, we have investigated the in vitro and in vivo effects of watercress, which is a rich source of PEITC. We first demonstrated that, similar to PEITC, crude watercress extracts inhibited cancer cell growth and HIF activity in vitro. To examine the effects of dietary intake of watercress, we obtained plasma and peripheral blood mononuclear cells following the ingestion of an 80 g portion of watercress from healthy participants who had previously been treated for breast cancer. Analysis of PEITC in plasma samples from nine participants demonstrated a mean maximum plasma concentration of 297 nm following the ingestion of watercress. Flow cytometric analysis of 4E-BP1 phosphorylation in peripheral blood cells from four participants demonstrated significantly reduced 4E-BP1 phosphorylation at 6 and 8 h following the ingestion of watercress. Although further investigations with larger numbers of participants are required to confirm these findings, this pilot study suggests that flow cytometry may be a suitable approach to measure changes in 4E-BP1 phosphorylation following the ingestion of watercress, and that dietary intake of watercress may be sufficient to modulate this potential anti-cancer pathway.

Sulforaphane, a dietary component of broccoli/broccoli sprouts, inhibits breast cancer stem cells

PURPOSE

The existence of cancer stem cells (CSCs) in breast cancer has profound implications for cancer prevention. In this study, we evaluated sulforaphane, a natural compound derived from broccoli/broccoli sprouts, for its efficacy to inhibit breast CSCs and its potential mechanism.

EXPERIMENTAL DESIGN

Aldefluor assay and mammosphere formation assay were used to evaluate the effect of sulforaphane on breast CSCs in vitro. A nonobese diabetic/severe combined immunodeficient xenograft model was used to determine whether sulforaphane could target breast CSCs in vivo, as assessed by Aldefluor assay, and tumor growth upon cell reimplantation in secondary mice. The potential mechanism was investigated using Western blotting analysis and beta-catenin reporter assay.

RESULTS

Sulforaphane (1-5 micromol/L) decreased aldehyde dehydrogenase-positive cell population by 65% to 80% in human breast cancer cells (P < 0.01) and reduced the size and number of primary mammospheres by 8- to 125-fold and 45% to 75% (P < 0.01), respectively. Daily injection with 50 mg/kg sulforaphane for 2 weeks reduced aldehyde dehydrogenase-positive cells by >50% in nonobese diabetic/severe combined immunodeficient xenograft tumors (P = 0.003). Sulforaphane eliminated breast CSCs in vivo, thereby abrogating tumor growth after the reimplantation of primary tumor cells into the secondary mice (P < 0.01). Western blotting analysis and beta-catenin reporter assay showed that sulforaphane downregulated the Wnt/beta-catenin self-renewal pathway.

CONCLUSIONS

Sulforaphane inhibits breast CSCs and downregulates the Wnt/beta-catenin self-renewal pathway. These findings support the use of sulforaphane for the chemoprevention of breast cancer stem cells and warrant further clinical evaluation.

Cancer stem cells: a novel paradigm for cancer prevention and treatment

Cancer is the second leading cause for mortality in US only after heart disease and lacks a good or effective therapeutic paradigm. Despite the emergence of new, targeted agents and the use of various therapeutic combinations, none of the treatment options available is curative in patients with advanced cancer. A growing body of evidence is supporting the idea that human cancers can be considered as a stem cell disease. Malignancies are believed to originate from a fraction of cancer cells that show self renewal and pluripotency and are capable of initiating and sustaining tumor growth. The cancer-initiating cells or cancer stem cells were originally identified in hematological malignancies but is now being recognized in several solid tumors. The hypothesis of stem cell-driven tumorigenesis raises questions as to whether the current treatments, most of which require rapidly dividing cells are able to efficiently target these slow cycling tumorigenic cells. Recent characterization of cancer stem cells should lead to the identification of key signaling pathways that may make cancer stem cells vulnerable to therapeutic interventions that target drug-effluxing capabilities, anti-apoptotic mechanisms, and induction of differentiation. Dietary phytochemicals possess anti-cancer properties and represent a promising approach for the prevention and treatment of many cancers.

Mouse models for unraveling the importance of diet in colon cancer prevention

Diet and genetics are both considered important risk determinants for colorectal cancer, a leading cause of death worldwide. Several genetically engineered mouse models have been created, including the ApcMin mouse, to aid in the identification of key cancer related processes and to assist with the characterization of environmental factors, including the diet, which influence risk. Current research using these models provides evidence that several bioactive food components can inhibit genetically predisposed colorectal cancer, while others increase risk. Specifically, calorie restriction or increased exposure to n-3 fatty acids, sulforaphane, chafuroside, curcumin and dibenzoylmethane were reported protective. Total fat, calories and all-trans retinoic acid are associated with an increased risk. Unraveling the importance of specific dietary components in these models is complicated by the basal diet used, the quantity of test components provided and interactions among food components. Newer models are increasingly available to evaluate fundamental cellular processes, including DNA mismatch repair, immune function and inflammation as markers for colon cancer risk. Unfortunately, these models have been used infrequently to examine the influence of specific dietary components. The enhanced use of these models can shed mechanistic insights about the involvement of specific bioactive food and components and energy as determinants of colon cancer risk. However, the use of available mouse models to exactly represent processes important to human gastrointestinal cancers will remain a continued scientific challenge.

Enhancement of arsenic trioxide cytotoxicity by dietary isothiocyanates in human leukemic cells via a reactive oxygen species-dependent mechanism

Although clearly effective in acute promyelocytic leukemia (APL), arsenic trioxide (ATO) demonstrates little clinical benefit as a single agent in the treatment of non-APL hematological malignancies. We screened a library of 2000 marketed drugs and naturally occurring compounds to identify agents that potentiate the cytotoxic effects of ATO in leukemic cells. Here, we report the identification of three isothiocyanates (sulforaphane, erysolin and erucin) found in cruciferous vegetables as enhancers of ATO cytotoxicity. Both erysolin and sulforaphane significantly enhanced ATO-mediated cytotoxicity and apoptosis in a panel of leukemic cell lines; erucin activity was variable among cell types. Cellular exposure to sulforaphane in combination with ATO resulted in a dramatic increase in levels of reactive oxygen species (ROS) compared to treatment with either agent alone. Sulforaphane, alone or with ATO, decreased intracellular glutathione (GSH) content. Furthermore, addition of the free radical scavenger N-acetyl-l-cysteine (NAC) rescued cells from ATO/isothiocyanate-mediated cytotoxicity. Our data suggest that isothiocyanates enhance the cytotoxic effects of ATO through a ROS-dependent mechanism. Combinatorial treatment with isothiocyanates and ATO might provide a promising therapeutic approach for a variety of myeloid malignancies.

Redox-directed cancer therapeutics: molecular mechanisms and opportunities

Redox dysregulation originating from metabolic alterations and dependence on mitogenic and survival signaling through reactive oxygen species represents a specific vulnerability of malignant cells that can be selectively targeted by redox chemotherapeutics. This review will present an update on drug discovery, target identification, and mechanisms of action of experimental redox chemotherapeutics with a focus on pro- and antioxidant redox modulators now in advanced phases of preclinal and clinical development. Recent research indicates that numerous oncogenes and tumor suppressor genes exert their functions in part through redox mechanisms amenable to pharmacological intervention by redox chemotherapeutics. The pleiotropic action of many redox chemotherapeutics that involves simultaneous modulation of multiple redox sensitive targets can overcome cancer cell drug resistance originating from redundancy of oncogenic signaling and rapid mutation.Moreover, some redox chemotherapeutics may function according to the concept of synthetic lethality (i.e., drug cytotoxicity is confined to cancer cells that display loss of function mutations in tumor suppressor genes or upregulation of oncogene expression). The impressive number of ongoing clinical trials that examine therapeutic performance of novel redox drugs in cancer patients demonstrates that redox chemotherapy has made the crucial transition from bench to bedside.

Sulforaphane suppresses oligomerization of TLR4 in a thiol-dependent manner

TLRs are pattern recognition receptors that detect invading microorganisms and nonmicrobial endogenous molecules to trigger immune and inflammatory responses during host defense and tissue repair. TLR activity is closely linked to the risk of many inflammatory diseases and immune disorders. Therefore, TLR signaling pathways can provide efficient therapeutic targets for chronic diseases. Sulforaphane (SFN), an isothiocyanate, has been well known for its anti-inflammatory activities. In this study, we investigated the modulation of TLR activity by SFN and the underlying mechanism. SFN suppressed ligand-induced and ligand-independent TLR4 activation because it prevented IL-1R-associated kinase-1 degradation, activation of NF-kappaB and IFN regulatory factor 3, and cyclooxygenase-2 expression induced by LPS or overexpression of TLR4. Receptor oligomerization, which is one of the initial and critical events of TLR4 activation, was suppressed by SFN, resulting in the downregulation of NF-kappaB activation. SFN formed adducts with cysteine residues in the extracellular domain of TLR4 as confirmed by liquid chromatography-tandem mass spectrometry analysis and the inhibitory effects of SFN on oligomerization and NF-kappaB activation were reversed by thiol donors (DTT and N-acetyl-L-cysteine). These suggest that the reactivity of SFN to sulfhydryl moiety contributes to its inhibitory activities. Blockade of TLR4 signaling by SFN resulted in the reduced production of inflammatory cytokines and the decreased dermal inflammation and edema in vivo in experimental inflammatory animal models. Collectively, our results demonstrated that SFN downregulated TLR4 signaling through the suppression of oligomerization process in a thiol-dependent manner. These present a novel mechanism for beneficial effects of SFN and a novel anti-inflammatory target in TLR4 signaling.

Hybrid anticancer agents: isothiocyanate-progesterone conjugates as chemotherapeutic agents and insights into their cytotoxicities

New hybrid molecules of isothiocyanate and progesterone and their metal complexes were synthesized exhibiting promising anti-proliferative and pro-apoptotic activity against breast and prostate cancer cells. These metal complex compounds exploited an existing cellular transport pathway for delivery of cytotoxic isothiocyanate moiety across cell membrane resulting in the inhibition of cell viability and inducing apoptosis. The highest apoptotic action was shown by the copper complex, which was mediated through the inhibition of Akt signaling similar to the one shown by isothiocyanate compounds. Our results underscore the possible role of metal redox cycling, and thus it is likely will open newer avenues for further optimization for the synthesis of novel active compounds through appropriate isothiocyanate pharmacophores.

Human gut bacterial communities are altered by addition of cruciferous vegetables to a controlled fruit- and vegetable-free diet

In the human gut, commensal bacteria metabolize food components that typically serve as energy sources. These components have the potential to influence gut bacterial community composition. Cruciferous vegetables, such as broccoli and cabbage, contain distinctive compounds that can be utilized by gut bacteria. For example, glucosinolates can be hydrolyzed by certain bacteria, and dietary fibers can be fermented by a range of species. We hypothesized that cruciferous vegetable consumption would alter growth of certain bacteria, thereby altering bacterial community composition. We tested this hypothesis in a randomized, crossover, controlled feeding study. Fecal samples were collected from 17 participants at the end of 2 14-d intake periods: a low-phytochemical, low-fiber basal diet (i.e. refined grains without fruits or vegetables) and a high ("double") cruciferous vegetable diet [basal diet + 14 g cruciferous vegetables/(kg body weightd)]. Fecal bacterial composition was analyzed by the terminal restriction fragment length polymorphism (tRFLP) method using the bacterial 16S ribosomal RNA gene and nucleotide sequencing. Using blocked multi-response permutation procedures analysis, we found that overall bacterial community composition differed between the 2 consumption periods (delta = 0.603; P = 0.011). The bacterial community response to cruciferous vegetables was individual-specific, as revealed by nonmetric multidimensional scaling ordination analysis. Specific tRFLP fragments that characterized each of the diets were identified using indicator species analysis. Putative species corresponding to these fragments were identified through gene sequencing as Eubacterium hallii, Phascolarctobacterium faecium, Burkholderiales spp., Alistipes putredinis, and Eggerthella spp. In conclusion, human gut bacterial community composition was altered by cruciferous vegetable consumption, which could ultimately influence gut metabolism of bioactive food components and host exposure to these compounds.

Glucosinolate engineering identifies a gamma-glutamyl peptidase

Consumption of cruciferous vegetables is associated with reduced risk of developing cancer, a phenomenon attributed to glucosinolates, which are characteristic of these vegetables. We report production of the bioactive benzylglucosinolate in the noncruciferous plant Nicotiana benthamiana through metabolic engineering. The study includes identification of gamma-glutamyl peptidase 1 (GGP1), which substantially increased glucosinolate production by metabolizing an accumulating glutathione conjugate, an activity not previously described for glucosinolate biosynthesis or for proteins containing glutamine amidotransferase domains.

Activation of several concurrent proapoptic pathways by sulforaphane in human colon cancer cells SW620

Despite the reported cytotoxicity and apoptosis-inducing properties of sulforaphane (SF) in colon cancer cells, the details concerning individual mechanisms and signaling cascades underlying SF-mediated apoptosis remain unclear. To understand different aspects of SF-induced proapoptic signaling in advanced colon carcinoma, we investigated its mechanisms in metastatic SW620 cell line. Our results indicate that in SW620 cells SF acts to induce multivariate cascades including DNA-damage response pathway whose proapoptotic signaling is nevertheless reduced owing to the mutant status of p53 and caspase-2-JNK pathway which seems to complement and enhance p53-dependent signaling, however only in wild-type p53. Furthermore, both pathways require the active role of mitochondria and do not depend on generation of ROS, making SF an attractive chemopreventive agent whose antitumor properties should be further investigated in colon cancer.

GST polymorphism and excretion of heterocyclic aromatic amine and isothiocyanate metabolites after Brassica consumption

Brassica vegetable intake has been associated with decreased risk and well-done meat intake has been associated with increased risk of cancers at multiple organ sites in epidemiologic studies. Experimental studies suggest a role of modulation of phase I and phase II metabolizing enzymes as one mechanism for these associations. Heterocyclic aromatic amines (HAAs) are carcinogens formed in meat that has been cooked to well-done and at high temperatures. Phase I metabolizing enzymes catalyze the activation of HAAs, and phase II metabolizing enzymes serve to detoxify the active carcinogens. The glutathione S-transferases (GSTs) are a family of phase II metabolizing enzymes that are induced by, and act to conjugate, isothiocyanates (ITCs), phytochemicals found in Brassica vegetables. This review summarizes the results of feeding studies in humans that examine effects of polymorphisms in GSTs on ITC metabolite excretion, reviews the evidence for modulation of HAA mutagenicity by ITCs, and discusses the need for feeding studies examining potential interactions among polymorphic genes encoding phase I and phase II metabolizing enzymes, meat intake, and Brassica intake to elucidate their role in cancer etiology.

Modulation of histone deacetylase activity by dietary isothiocyanates and allyl sulfides: studies with sulforaphane and garlic organosulfur compounds

Histone deacetylase (HDAC) inhibitors reactivate epigenetically-silenced genes in cancer cells, triggering cell cycle arrest and apoptosis. Recent evidence suggests that dietary constituents can act as HDAC inhibitors, such as the isothiocyanates found in cruciferous vegetables and the allyl compounds present in garlic. Broccoli sprouts are a rich source of sulforaphane (SFN), an isothiocyanate that is metabolized via the mercapturic acid pathway and inhibits HDAC activity in human colon, prostate, and breast cancer cells. In mouse preclinical models, SFN inhibited HDAC activity and induced histone hyperacetylation coincident with tumor suppression. Inhibition of HDAC activity also was observed in circulating peripheral blood mononuclear cells obtained from people who consumed a single serving of broccoli sprouts. Garlic organosulfur compounds can be metabolized to allyl mercaptan (AM), a competitive HDAC inhibitor that induced rapid and sustained histone hyperacetylation in human colon cancer cells. Inhibition of HDAC activity by AM was associated with increased histone acetylation and Sp3 transcription factor binding to the promoter region of the P21WAF1 gene, resulting in elevated p21 protein expression and cell cycle arrest. Collectively, the results from these studies, and others reviewed herein, provide new insights into the relationships between reversible histone modifications, diet, and cancer chemoprevention.

Erucin, a new promising cancer chemopreventive agent from rocket salads, shows anti-proliferative activity on human lung carcinoma A549 cells

Erucin (ER) is a dietary isothiocyanate present in cruciferous vegetables, such as rocket salads (Erucasativa Mill., Diplotaxis sp.), that has been recently considered a promising cancer chemopreventive phytochemical. Biological activity of ER was investigated on human lung adenocarcinoma A549 cells, analyzing its effects on molecular pathways involved in apoptosis and cell cycle arrest, such as PARP-1 cleavage, p53 and p21 protein expression. Our results show that ER affects the A549 cell proliferation, enhancing significantly p53 and p21 protein expression in a dose-dependent manner (p<0.001). PARP-1 cleavage occurs only after exposure to high concentrations of ER (50 microM), in accordance to previous studies showing similar bioactivity of other isothiocyanates (ITCs). Our study reports for the first time that the induction of p53, p21 and PARP-1 cleavage may participate in the anti-proliferative activity of ER in human lung adenocarcinoma A549 cells. Comparison of data with those obtained with the isothiocyanate sulforaphane (SF), structurally related to ER, underlines the strong relationship between structural analogy of ITCs and their biological activity. The ability of dietary compounds to modulate molecular mechanisms that affect cancer cell proliferation is certainly a key point of the cancer prevention potential by functional foods.

Temporal changes in gene expression induced by sulforaphane in human prostate cancer cells

BACKGROUND

Prostate cancer is thought to arise as a result of oxidative stresses and induction of antioxidant electrophile defense (phase 2) enzymes has been proposed as a prostate cancer prevention strategy. The isothiocyanate sulforaphane, derived from cruciferous vegetables like broccoli, potently induces surrogate markers of phase 2 enzyme activity in prostate cells in vitro and in vivo. To better understand the temporal effects of sulforaphane and broccoli sprouts on gene expression in prostate cells, we carried out comprehensive transcriptome analysis using cDNA microarrays.

METHODS

Transcripts significantly modulated by sulforaphane over time were identified using StepMiner analysis. Ingenuity Pathway Analysis (IPA) was used to identify biological pathways, networks, and functions significantly altered by sulforaphane treatment.

RESULTS

StepMiner and IPA revealed significant changes in many transcripts associated with cell growth and cell cycle, as well as a significant number associated with cellular response to oxidative damage and stress. Comparison to an existing dataset suggested that sulforaphane blocked cell growth by inducing G2/M arrest. Cell growth assays and flow cytometry analysis confirmed that sulforaphane inhibited cell growth and induced cell cycle arrest.

CONCLUSIONS

Our data suggest that in prostate cells sulforaphane primarily induces cellular defenses and inhibits cell growth by causing G2/M phase arrest. Furthermore, based on the striking similarities in the gene expression patterns induced across experiments in these cells, sulforaphane appears to be the primary bioactive compound present in broccoli sprouts, suggesting that broccoli sprouts can serve as a suitable source for sulforaphane in intervention trials.

Quantification of sulforaphane mercapturic acid pathway conjugates in human urine by high-performance liquid chromatography and isotope-dilution tandem mass spectrometry

We report validation of the first high-pressure liquid chromatography isotope-dilution mass spectrometry method to measure sulforaphane (SFN) and its glutathione-derived conjugates in human urine. As epidemiological evidence continues to mount that the consumption of a diet rich in cruciferous vegetables may reduce the risk of certain cancers, the development of analytical methodologies to accurately measure isothiocyanates (ITCs) and their subsequent metabolic products becomes paramount. SFN, the principal ITC produced by broccoli, is an effective chemopreventive agent with multiple modes of action. SFN and SFN conjugates have often been measured collectively utilizing a cyclocondensation assay with 1,2-benzenedithiol. More recently, some of the major SFN conjugates have been determined using mass spectrometry. Here, triple-quadrupole mass spectrometry has been coupled with the use of stable isotope-labeled internal standards of D8-SFN and all four D8-SFN mercapturic acid pathway conjugates to provide an accurate, precise, sensitive, and specific method for analysis of these compounds. Using urine samples collected during an earlier intervention with broccoli sprouts, the concentrations of SFN, SFN-cysteine, and the mercapturic acid SFN- N-acetylcysteine were sufficiently high such that as little as 50 nL of urine was required for analysis. Although each study participant received an equivalent dose of broccoli sprout preparation, the interindividual conversion of the precursor glucosinolate to SFN varied over 100-fold. These 98 urines provided an ideal sample set for examining the robustness of the assay. The mean urinary concentrations +/- standard deviations in overnight voids following ingestion of the first dose were 4.7 +/- 5.1, 0.03 +/- 0.05, 0.06 +/- 0.06, 18 +/- 15, and 42 +/- 23 nmol/mg creatinine for SFN, SFN-glutathione, SFN-cysteine-glycine, SFN-cysteine, and SFN- N-acetylcysteine, respectively. This method determines SFN and all four SFN glutathione-derived metabolites with minimal sample preparation and will be extremely useful in understanding the role of SFN-rich foods in preventing cancer and other chronic diseases.