Enhancement by indole-3-carbinol of liver and thyroid gland neoplastic development in a rat medium-term multiorgan carcinogenesis model

Do Brassica Vegetables Affect Thyroid Function?-A Comprehensive Systematic Review

Brassica vegetables are widely consumed all over the world, especially in North America, Asia, and Europe. They are a rich source of sulfur compounds, such as glucosinolates (GLSs) and isothiocyanates (ITCs), which provide health benefits but are also suspected of having a goitrogenic effect. Adhering to PRISMA guidelines, we conducted a systematic review to assess the impact of dietary interventions on thyroid function, in terms of the potential risk for people with thyroid dysfunctions. We analyzed the results of 123 articles of in vitro, animal, and human studies, describing the impact of brassica plants and extracts on thyroid mass and histology, blood levels of TSH, T3, T4, iodine uptake, and the effect on thyroid cancer cells. We also presented the mechanisms of the goitrogenic potential of GLSs and ITCs, the limitations of the studies included, as well as further research directions. The vast majority of the results cast doubt on previous assumptions claiming that brassica plants have antithyroid effects in humans. Instead, they indicate that including brassica vegetables in the daily diet, particularly when accompanied by adequate iodine intake, poses no adverse effects on thyroid function.

Evaluation of Pendrin Expression Using Nuclear Imaging Modalities and Immunohistochemistry in Animal Thyroid Cancer Model

Context

The impaired ability of thyroid cancer (TC) cells to uptake and concentrate iodine represents a major therapeutic challenge in malignant TC management. This has been reported probably due to reduced or loss of expression of pendrin in thyroid tumors.

Aims

In view of this, we evaluated the pendrin expression in the chemically induced (using N-bis[2-hydroxypropyl] nitrosamine [DHPN]) TC model in Wistar rats.

Methods

Uptake in the thyroid gland was evaluated by positron emission tomography with computed tomography (PET-CT) and scintigraphy imaging. Further histopathology (HP) and immunohistochemistry (IHC) were performed for confirming malignancy.

Results

The altered uptake in the thyroid gland was observed by PET-CT and scintigraphy imaging. Significant pathological changes in the thyroid were observed using 2-deoxy-2-(fluorine-18) fluoro-D-glucose PET-CT, technetium-99m pertechnetate imaging, and reduced iodine-131 uptake (n = 4) in DHPN-induced animals compared to control indicative of thyroid cell proliferation. In treated groups, tissue HP revealed hyperplastic follicular to papillary cell proliferation with variable mitotic activity. The malignant nature of the tissue and variable uptake of the tracer were further reconfirmed by IHC. IHC revealed reduced pendrin expression in malignant thyroid tissue.

Conclusions

Hence, nuclear imaging techniques can be of aid in the early identification and evaluation of cellular changes during the early development of tumor models in laboratory animals. In conclusion, our study reveals that pendrin expression plays a vital role in thyroid uptake, and its reduction was observed in TC in a chemically induced TC model.

Bisphenol A drives di(2-ethylhexyl) phthalate promoting thyroid tumorigenesis via regulating HDAC6/PTEN and c-MYC signaling

Bisphenol A (BPA) and di-(2-ethylhcxyl) phthalate (DEHP) are exist widespread in the environment and produce adverse effect to human as environmental disruptors (EDCs). Epidemiological studies have found that the exposure of DEHP and BPA could increase the susceptibility to thyroid diseases including thyroid cancer and benign thyroid nodules. Due to the existence of multiple pollutants in our daily life, the mixed toxic effects of exposure and their interrelationships may distinguish from the exposure to a single chemical, so it is of great significance to explore the mixed toxic effect of DEHP and BPA co-exposure. Thyroid, as one of the target organs of EDCs, is prone to tumor occurrence, however, whether the mixture of BPA and DEHP will affect the occurrence of thyroid cancer is still obscure. We aim to investigate the effect of single or combined exposure to BPA and DEHP on the occurrence of thyroid cancer. An animal model of exposure to BPA and DEHP was firstly established to evaluate their effect on DMD-induced thyroid cancer. Additionally, human thyroid cancer cells BCPAP and thyroid cells Nthy-ori3-1 were used to further clarify some possible mechanisms of BPA and MEHP, the main metabolite of DEHP. Consequently, we found that BPA alone could increase the incidence of thyroid tumors in female rats compared with DEHP, and DEHP enhanced the effect of BPA on cancer promotion. BPA alone and in combination with DEHP mainly induced the expression of HDAC6, inhibited tumor suppressor gene PTEN upregulated the expression of oncogene c-MYC, and eventually elevate the susceptibility to thyroid tumors. Mechanistically, BPA alone and in combination with MEHP could significantly induce the proliferation of BCPAP cells depending on HDAC6, which could modulate H3K9ac to inhibit PTEN, activate AKT signaling pathway, and simultaneously upregulate the expression of c-MYC. Interestingly, we found that BPA alone and in combination with MEHP could significantly induce the proliferation of Nthy-ori3-1 cells independent on HDAC6 via activating ERK signaling pathway. Taken together, these findings not only provide new evidence of the promoting effect of BPA and DEHP on thyroid cancer but also discusses some possible mechanisms underlying these effects.

The Impact of Domestic Cooking Methods on Myrosinase Stability, Glucosinolates and Their Hydrolysis Products in Different Cabbage (Brassica oleracea) Accessions

Glucosinolate hydrolysis products are responsible for the health-promoting properties of Brassica vegetables. The impact of domestic cooking on the myrosinase stability, glucosinolates and hydrolysis products in 18 cabbage accession was investigated. Cabbages were steamed, microwaved, and stir-fried before analysis. Cooking significantly affected myrosinase stability and glucosinolate concentrations within and between cabbage morphotypes. Myrosinase was most stable after stir-frying, with up to 65% residual activity. Steaming and microwaving resulted in over 90% loss of myrosinase activity in some accessions. Stir-frying resulted in the greatest decrease in glucosinolate concentration, resulting in up to 70% loss. Steamed cabbages retained the highest glucosinolates after cooking (up to 97%). The profile and abundance of glucosinolate hydrolysis products detected varied across all cooking methods studied. Cooking reduced the amounts of nitriles and epithionitriles formed compared to raw samples. Steaming led to a significant increase in the concentration of beneficial isothiocyanates present in the cabbage and a significantly lower level of nitriles compared to other samples. Microwaving led to a reduction in the concentrations of both nitriles and isothiocyanates when compared to other cooking methods and raw cabbage. The results obtained help provide information on the optimal cooking methods for cabbage, suggesting that steaming may be the best approach to maximising beneficial isothiocyanate production.

Indoles Derived From Glucobrassicin: Cancer Chemoprevention by Indole-3-Carbinol and 3,3'-Diindolylmethane

Hydrolysis of glucobrassicin by plant or bacterial myrosinase produces multiple indoles predominantly indole-3-carbinol (I3C). I3C and its major in vivo product, 3,3'-diindolylmethane (DIM), are effective cancer chemopreventive agents in pre-clinical models and show promise in clinical trials. The pharmacokinetics/pharmacodynamics of DIM have been studied in both rodents and humans and urinary DIM is a proposed biomarker of dietary intake of cruciferous vegetables. Recent clinical studies at Oregon State University show surprisingly robust metabolism of DIM in vivo with mono- and di-hydroxylation followed by conjugation with sulfate or glucuronic acid. DIM has multiple mechanisms of action, the most well-characterized is modulation of aryl hydrocarbon receptor (AHR) signaling. In rainbow trout dose-dependent cancer chemoprevention by dietary I3C is achieved when given prior to or concurrent with aflatoxin B1, polycyclic aromatic hydrocarbons, nitrosamines or direct acting carcinogens such as N-methyl-N'-nitro-nitrosoguanidine. Feeding pregnant mice I3C inhibits transplacental carcinogenesis. In humans much of the focus has been on chemoprevention of breast and prostate cancer. Alteration of cytochrome P450-dependent estrogen metabolism is hypothesized to be an important driver of DIM-dependent breast cancer prevention. The few studies done to date comparing glucobrassicin-rich crucifers such as Brussels sprouts with I3C/DIM supplements have shown the greater impact of the latter is due to dose. Daily ingestion of kg quantities of Brussels sprouts is required to produce in vivo levels of DIM achievable by supplementation. In clinical trials these supplement doses have elicited few if any adverse effects. Sulforaphane from glucoraphanin can act synergistically with glucobrassicin-derived DIM and this may lead to opportunities for combinatorial approaches (supplement and food-based) in the clinic.

Indole-3-carbinol induces apoptosis-like death in Escherichia coli on different contribution of respective reactive oxygen species

AIMS

Indole-3-carbinol (I3C) is a natural compound derived from brassica vegetables, displaying antibacterial activity. The study aims to elucidate the antibacterial mode of action(s) induced by indole-3-carbionol in Escherichia coli and enhance the understandings on the respective contribution of each reactive oxygen species (ROS), superoxide anion (O₂^-), hydrogen peroxide (H₂O₂), hydroxyl radical (OH^-) during the process.

MAIN METHODS

The antibacterial activity of I3C was assessed through kinetic assay. The generation of ROS was measured by flow cytometer using H₂DCFDA dye, while further analysis of respective contribution was done through application of each scavenger: tiron, thiourea and sodium pyruvate. DNA fragmentation and chromatin condensation were observed by TUNEL and DAPI staining agent. Finally, Annexin V/PI, FITC-VAD-FMK and DiBAC₄(3) was applied for detection of apoptosis-like death.

KEY FINDINGS

I3C exhibited antibacterial activity in E. coli through accumulation of ROS and DNA damage, eventually leading to apoptosis-like death. Contribution of each ROS displayed respective manner, OH^- exerting the most potent influence whereas O₂^- showed least impact.

SIGNIFICANCE

Our study is the first to link I3C to the bacterial apoptosis-like death and displays the potential of this agent as a candidate for potential drugs that could help regulating the E. coli, an opportunistic human pathogen. Moreover, the study focused on investigating the individual contribution of each ROS during the process, trying to enhance the understanding regarding ROS and cellular processes followed by oxidative stress in bacteria.

Maternal Epigenetic Regulation Contributes to Prevention of Estrogen Receptor-negative Mammary Cancer with Broccoli Sprout Consumption

Cruciferous vegetables have been of special interest due to the rich presence of bioactive compounds such as sulforaphane which show promising potential on cancer prevention and therapy as an epigenetic dietary strategy. Abnormal epigenetic alteration as one of the primary contributors to tumor development is closely related to breast cancer initiation and progression. In the present study, we investigated the effect of dietary broccoli sprouts (BSp), a common cruciferous vegetable, on prevention of estrogen receptor (ER)-negative mammary tumors at three different temporal exposure windows using a spontaneous breast cancer mouse model. Our findings indicate that maternal BSp treatment exhibited profound inhibitory and preventive effects on mammary cancer formation in the nontreated mouse offspring. The BSp diet administered to adult mice also showed suppressive effects on mammary cancer but was not as profound as the maternal BSp preventive effects. Moreover, such protective effects were linked with differentially expressed tumor- and epigenetic-related genes, as well as altered global histone acetylation, DNA methylation, and DNA hydroxymethylation levels. We also found that the expression changes of tumor-related genes were associated with the levels of histone methylation of H3K4 and H3K9 in the gene promoter regions. In addition, BSp-enriched sulforaphane was shown to increase protein expression of tumor suppressor genes such as p16 and p53 and inhibit the protein levels of Bmi1, DNA methyltransferases, and histone deacetylases in ERα-negative breast cancer cell lines. Collectively, these results suggest that maternal exposure to key phytochemicals may contribute to ER-negative mammary tumor prevention in their offspring through epigenetic regulations.

Synthesis and biological evaluation of new bisindole-imidazopyridine hybrids as apoptosis inducers

A series of diindolylmethanes (5a-t) were designed, synthesized, and examined for their cytotoxicity against four human cancer cell lines like prostate (DU-145), lung (A549), breast (MCF-7) and cervical cancer (HeLa). These results revealed that among all the hybrids, two (5k and 5r) were identified and exhibited significant cytotoxic effect against A549 cancer cells with IC₅₀ values of 1.65 ± 0.3 and 1.80 ± 0.8 µM respectively. To investigate the reasons for the cytotoxic activity, the conventional biological assays were carried out with 5k and 5r on the A549 cancer cells. Both hybrids led to the arrest of A549 cell lines at the G2/M phase of the cell cycle and strongly induced apoptosis. Further the apoptotic effects of 5k and 5r were confirmed by ROS, annexin-V FITC, and mitochondrial membrane potential. Moreover, structure-activity relationships were elucidated with various substitutions on these hybrids.

Sulforaphane: Its "Coming of Age" as a Clinically Relevant Nutraceutical in the Prevention and Treatment of Chronic Disease

A growing awareness of the mechanisms by which phytochemicals can influence upstream endogenous cellular defence processes has led to intensified research into their potential relevance in the prevention and treatment of disease. Pharmaceutical medicine has historically looked to plants as sources of the starting materials for drug development; however, the focus of nutraceutical medicine is to retain the plant bioactive in as close to its native state as possible. As a consequence, the potency of a nutraceutical concentrate or an extract may be lower than required for significant gene expression. The molecular structure of bioactive phytochemicals to a large extent determines the molecule's bioavailability. Polyphenols are abundant in dietary phytochemicals, and extensive in vitro research has established many of the signalling mechanisms involved in favourably modulating human biochemical pathways. Such pathways are associated with core processes such as redox modulation and immune modulation for infection control and for downregulating the synthesis of inflammatory cytokines. Although the relationship between oxidative stress and chronic disease continues to be affirmed, direct-acting antioxidants such as vitamins A, C, and E, beta-carotene, and others have not yielded the expected preventive or therapeutic responses, even though several large meta-analyses have sought to evaluate the potential benefit of such supplements. Because polyphenols exhibit poor bioavailability, few of their impressive in vitro findings have been replicated in vivo. SFN, an aliphatic isothiocyanate, emerges as a phytochemical with comparatively high bioavailability. A number of clinical trials have demonstrated its ability to produce favourable outcomes in conditions for which there are few satisfactory pharmaceutical solutions, foreshadowing the potential for SFN as a clinically relevant nutraceutical. Although myrosinase-inert broccoli sprout extracts are widely available, there now exist myrosinase-active broccoli sprout supplements that yield sufficient SFN to match the doses used in clinical trials.

Food as Pharma? The Case of Glucosinolates

BACKGROUND

Glucosinolates (GLSs) are dietary plant secondary metabolites occurring in the order Brassicales with potential health effects, in particular as anti-carcinogenic compounds. GLSs are converted into a variety of breakdown products (BPs) upon plant tissue damage and by the gut microbiota. GLS biological activity is related to BPs rather than to GLSs themselves.

METHODS

we have reviewed the most recent scientific literature on the metabolic fate and the biological effect of GLSs with particular emphasis on the epidemiological evidence for health effect and evidence from clinical trials. An overview of potential molecular mechanisms underlying GLS biological effect is provided. The potential toxic or anti-nutritional effect has also been discussed.

RESULTS

Epidemiological and human in vivo evidence point towards a potential anti-cancer effect for sulforaphane, indole-3-carbinol and 3,3-diindolylmethane. A number of new human clinical trials are on-going and will likely shed further light on GLS protective effect towards cancer as well as other diseases. BPs biological effect is the results of a plurality of molecular mechanisms acting simultaneously which include modulation of xenobiotic metabolism, modulation of inflammation, regulation of apoptosis, cell cycle arrest, angiogenesis and metastasis and regulation of epigenetic events. BPs have been extensively investigated for their protective effect towards cancer but in recent years the interest also includes other diseases.

CONCLUSION

It appears that certain BPs may protect against and may even represent a therapeutic strategy against several forms of cancer. Whether this latter effect can be achieved through diet or supplements should be investigated more thoroughly.

Preventive Potential of Resveratrol in Carcinogen-Induced Rat Thyroid Tumorigenesis

Thyroid cancer (TC) is the most common endocrine malignancy without reliable preventive agent. Resveratrol possesses in vitro anti-TC activities; while its effect(s) on thyroid tumorigenesis remains unknown. This study aims to address this issue using DEN/MNU/DHPN-induced rat carcinogenesis model. 50 male Sprague-Dawley rats were separated into four groups as Group-1 (5 rats); normally fed; Group-2 (15 rats); DEN/MNU/DHPN treatment only; Group-3 (15 rats) and -4 (15 rats); DEN/MNU/DHPN treatment; followed by resveratrol intragastric (IG) injection and intraperitoneal (IP) injection; respectively; in two-day intervals for 30 weeks. The results revealed that the average resveratrol concentration in thyroid tissues was 1.278 ± 0.419 nmol/g in IG group and 1.752 ± 0.398 nmol/g in IP group. The final body weights of Group-3 and Group-4 were lighter than that (p > 0.05) of Group-1; but heavier than Group-2 (p < 0.05). TC-related lesions (hyperplasia and adenomas) were found in 53.3% of Group-2; 33.3% Group-3 and 26.7% Group-4. Lower serum carcino-embryonic antigen (CEA) and thyroglobulin (Tg) levels; down-regulated expression of IL-6 and cyclooxygenase-2 (COX-2); reduction of NF-κB/p65 nuclear translocation; and elevated IkBα expression were found in the thyroid tissues of Group-3 and Group-4 in comparison with that of Group-2. These results demonstrate that IG and IP administered resveratrol efficiently reduces the frequency and severity of DEN/MNU/DHPN-caused TC-related lesions and would be of values in thyroid tumor prevention.

Modulation of CYP1A1 metabolism: From adverse health effects to chemoprevention and therapeutic options

The human cytochrome P450 (CYP) 1A1 gene encodes a monooxygenase that metabolizes multiple exogenous and endogenous substrates. CYP1A1 has become infamous for its oxidative metabolism of benzo[a]pyrene and related polycyclic aromatic hydrocarbons, converting these chemicals into very potent human carcinogens. CYP1A1 expression is mainly controlled by the aryl hydrocarbon receptor (AHR), a transcription factor whose activation is induced by binding of persistent organic pollutants, including polycyclic aromatic hydrocarbons and dioxins. Accordingly, induction of CYP1A1 expression and activity serves as a biomarker of AHR activation and associated xenobiotic metabolism as well as toxicity in diverse animal species and humans. Determination of CYP1A1 activity is integrated into modern toxicological concepts and testing guidelines, emphasizing the tremendous importance of this enzyme for risk assessment and regulation of chemicals. Further, CYP1A1 serves as a molecular target for chemoprevention of chemical carcinogenesis, although present literature is controversial on whether its inhibition or induction exerts beneficial effects. Regarding therapeutic applications, first anti-cancer prodrugs are available, which require a metabolic activation by CYP1A1, and thus enable a specific elimination of CYP1A1-positive tumors. However, the application range of these drugs may be limited due to the frequently observed downregulation of CYP1A1 in various human cancers, probably leading to a reduced metabolism of endogenous AHR ligands and a sustained activation of AHR and associated tumor-promoting responses. We here summarize the current knowledge on CYP1A1 as a key player in the metabolism of exogenous and endogenous substrates and as a promising target molecule for prevention and treatment of human malignancies.

Tea polyphenols EGCG and TF restrict tongue and liver carcinogenesis simultaneously induced by N-nitrosodiethylamine in mice

The aim of this study is to understand the molecular mechanisms of N-nitrosodiethylamine (NDEA) induced multi-organ carcinogenesis in tongue and liver of the same mouse and restriction of carcinogenesis by Epigallocatechin gallate (EGCG) and Theaflavin (TF), if any. For that purpose, cellular proliferation/apoptosis, prevalence of CD44 positive stem cell population and expressions of some key regulatory genes of self renewal Wnt and Hedgehog (Hh) pathways and some of their associated genes were analyzed in the NDEA induced tongue and liver lesions in absence or presence of EGCG/TF. Chronic NDEA exposure in oral cavity could decrease mice body weights and induce tongue and liver carcinogenesis with similar histological stages (severe dysplasia up to 30thweeks of NDEA administration). Increasing mice body weights were seen in continuous and post EGCG/TF treated groups. EGCG/TF treatment could restrict both the carcinogenesis at similar histological stages showing potential chemopreventive effect in continuous treated groups (mild dysplasia) followed by pre treatment (moderate dysplasia) and therapeutic efficacy in post treated groups (mild dysplasia) up to 30thweek. The mechanism of carcinogenesis by NDEA and restriction by the EGCG/TF in both tongue and liver were similar and found to be associated with modulation in cellular proliferation/apoptosis and prevalence of CD44 positive population. The up-regulation of self renewal Wnt/β-catenin, Hh/Gli1 pathways and their associated genes Cyclin D1, cMyc and EGFR along with down regulation of E-cadherin seen during the carcinogenesis processes were found to be modulated during the restriction processes by EGCG/TF.

Indole-3-Carbinol and Its Role in Chronic Diseases

Indole-3-carbinol (I3C), a common phytochemical in cruciferous vegetables, and its condensation product, 3,3'-diindolylmethane (DIM) exert several biological activities on cellular and molecular levels, which contribute to their well-recognized chemoprevention potential. Initially, these compounds were classified as blocking agents that increase drug-metabolizing enzyme activity. Now it is widely accepted that I3C and DIM affect multiple signaling pathways and target molecules controlling cell division, apoptosis, or angiogenesis deregulated in cancer cells. Although most of the current data support the role of I3C and DIM in prevention of hormone-dependent cancers, it seems that their application in prevention of the other cancer as well as cardiovascular disease, obesity, and diabetes reduction is also possible. This chapter summarizes the current experimental data on the I3C and DIM activity and the results of clinical studies indicating their role in prevention of chronic diseases.

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.

Involvement of PTEN/Akt signaling and oxidative stress on indole-3-carbinol (I3C)-induced hepatocarcinogenesis in rats

We previously reported that indole-3-carbinol (I3C) had hepatocellular tumor-promoting activity in a short-term (8 weeks) two-stage liver carcinogenesis model in rats. It was suggested that this effect was related to the production of reactive oxygen species (ROS) caused by cytochrome P450 1A (CYP1A) induction. In the present study, 0.5% I3C was administered to DEN-initiated rats for 26 weeks to examine the effect of prolonged administration of I3C and to clarify the possible mechanisms of I3C-induced hepatocarcinogenesis. The number and area of GST-P positive foci, ROS production, TBARS level, 8-OHdG content and mRNA levels of Ahr and Nrf2 gene batteries significantly increased in the DEN-I3C group compared with the DEN-alone group. Furthermore, some GST-P positive preneoplastic foci progressed to hepatocellular adenomas with the prolongation of I3C administration. Lack of PTEN and phospho-Smad2/3 expression and translocations of PDPK1 and phospho-Akt substrates to underneath the cell membrane were observed in the majority of hepatocellular adenomas. In addition, the number of Ki-67 positive cells increased in adenomas compared with the preneoplastic foci. These results suggest that the administration of I3C for 26 weeks in DEN-initiated rats induces tumor progression from hepatocellular altered foci to hepatocellular adenomas by ROS-mediated Akt activation that inhibits the TGF-β/Smad signaling and results in the increased cell proliferation.

Physiological and behavioural effects of fruit toxins on seed-predating versus seed-dispersing congeneric rodents

Fleshy, ripe fruits attract seed dispersers but also seed predators. Although many fruit consumers (legitimate seed dispersers as well as seed predators) are clearly exposed to plant secondary compounds (PSCs), their impact on the consumers’ physiology and foraging behaviour has been largely overlooked. Here, we document the divergent behavioural and physiological responses of three congeneric rodent species in the Middle East, seed dispersers versus seed predators, to fruit consumption. The fruit pulp of the desert plant Ochradenus baccatus contains high concentrations of glucosinolates (GLSs). These GLSs are hydrolyzed into active toxic compounds upon contact with the myrosinase enzyme released from seeds crushed during fruit consumption. Acomys russatus and A. cahirinus share a desert habitat. Acomys russatus acts as an O. baccatus seed predator, and A. cahirinus circumvents the activation of the GLSs by orally expelling vital seeds. We found that between the three species examined, A. russatus was physiologically most tolerant to whole fruit consumption and even A. minous, which is evolutionarily naïve to O. baccatus, exhibits greater tolerance to whole fruit consumption than A. cahirinus. However, like A. cahirinus, A. minous may also behaviourally avoid the activation of the GLSs by making a hole in the pulp and consuming only the seeds. Our findings demonstrate that seed predators have a higher physiological tolerance than seed dispersers when consuming fruits containing toxic PSCs. The findings also demonstrate the extreme ecological/evolutionary ability of this plant-animal symbiosis to shift from predation to mutualism and vice versa.

Intestinal lymphangiectasis and lipidosis in rats following subchronic exposure to indole-3-carbinol via oral gavage

To investigate the toxicity and carcinogenic potential of indole-3-carbinol (I3C), the National Toxicology Program has conducted 13-week subchronic studies in Fisher 344 rats and B6C3F1 mice, and chronic 2-year bioassays in Sprague-Dawley rats and B6C3F1 mice. While the chronic study results are not yet available, subchronic study results and short-term special evaluations of interim sacrifices in the 2-year rat bioassay are presented. F344 rats were orally gavaged ≤300 mg I3C/kg body weight 5 days a week for 13 weeks. Rats treated with ≥150 mg/kg demonstrated a dose-related dilation of lymphatics (lymphangiectasis) of the duodenum, jejunum, and mesenteric lymph nodes. Material within dilated lacteals stained positively for Oil Red O and Sudan Black, consistent with lipid. Electron microscopic evaluation confirmed extracellular lipid accumulation within the villar lamina propria, lacteals, and within villar macrophages. Analyses of hepatic and pulmonary CYP1A enzymes demonstrated dose-dependent I3C induction of CYP1A1 and 1A2. B6C3F1 mice orally gavaged ≤250 mg I3C/kg body weight did not demonstrate histopathological changes; however, hepatic CYP induction was similar to that in rats. The histopathologic changes of intestinal lymphangiectasis and lipidosis in this study share similarities with intestinal lymphangiectasia as observed in humans and dogs. However, the resultant clinical spectrum of protein-losing enteropathy was not present.

Microbial production of indolylglucosinolate through engineering of a multi-gene pathway in a versatile yeast expression platform

Epidemiological studies have shown that consumption of cruciferous vegetables, such as, broccoli and cabbages, is associated with a reduced risk of developing cancer. This phenomenon has been attributed to specific glucosinolates among the ~30 glucosinolates that are typically present as natural products characteristic of cruciferous plants. Accordingly, there has been a strong interest to produce these compounds in microbial cell factories as it will allow production of selected beneficial glucosinolates. We have developed a versatile platform for stable expression of multi-gene pathways in the yeast, Saccharomyces cerevisiae. Introduction of the seven-step pathway of indolylglucosinolate from Arabidopsis thaliana to yeast resulted in the first successful production of glucosinolates in a microbial host. The production of indolylglucosinolate was further optimized by substituting supporting endogenous yeast activities with plant-derived enzymes. Production of indolylglucosinolate serves as a proof-of-concept for our expression platform, and provides a basis for large-scale microbial production of specific glucosinolates for the benefit of human health.

Indole-3-carbinol enhances oxidative stress responses resulting in the induction of preneoplastic liver cell lesions in partially hepatectomized rats initiated with diethylnitrosamine

The liver tumor-promoting effects of indole-3-carbinol (I3C), a cytochrome P450 (CYP) 1A inducer found in cruciferous vegetables, were investigated using a medium-term hepatocarcinogenesis model in rats. Six-week-old male F344 rats received an intraperitoneal injection of N-diethylnitrosamine (DEN) and were fed a diet containing 0 (DEN-alone), 0.25, 0.50 or 1.0% of I3C for 8 weeks from 2 weeks after DEN-initiation. The number and area of liver cell foci positive for glutathione S-transferase placental form (GST-P) significantly increased in the livers of rats given 0.5% I3C or more, compared to those in the DEN-alone group. The number of GST-P positive foci also increased in the 0.25% I3C group. The number of liver cells positive for proliferating cell nuclear antigen (PCNA) significantly increased in all I3C groups compared to that in the DEN-alone group. Real-time RT-PCR analysis showed that I3C increased transcript levels of not only Cyp1a1 but also aryl hydrocarbon receptor (AhR) and/or nuclear factor (erythroid-derived 2)-like 2 (Nrf2) gene batteries, such as Cyp1a2, Cyp1b1, Ugt1a6, Nrf2, Nqo1, Gsta5, Gstm2, Ggt1and Gpx2. Reactive oxygen species (ROS) in the microsomal fraction significantly increased in all I3C-treated groups compared to the DEN-alone group, and thiobarbituric acid-reactive substances (TBARS) levels and 8-hydroxy-2'-deoxyguanosine (8-OHdG) content significantly increased in all of the I3C-treated groups and 1.0% I3C group, respectively. These results suggest that I3C is an AhR activator and enhances microsomal ROS production resulting in the upregulation of Nrf2 gene batteries, but the oxidative stress generated overcomes the antioxidant effect of Nrf2-related genes. Such 'a redox imbalance' subsequently induces liver tumor-promoting effects by enhancing cellular proliferation in rats.

Cruciferous vegetables in cancer prevention

Epidemiological studies have reported a strong inverse correlation between the intake of cruciferous vegetables and the cancer risk. This association has been found stronger than the association between cancer risk and fruit and vegetable intake in general. Cruciferous vegetables are unique in that they are rich sources of glucosinolates. Hydrolytic degradation of glucosinolates results in the formation of biologically active compounds, including indoles (such as I3C - indole-3-carbinol, DIM - diindolylmethane, indole phytoalexins) and isothiocyanates (such as PEITC - phenethyl isothiocyanate, SFN - sulforaphane). Some mechanisms, like effect on biotransformation system, induction of cell cycle arrest and apoptosis, and antiangiogenic effect, by which cruciferous vegetables act as chemopreventive agents have been described. Beneficial modulation of oestrogen metabolism with reduced risk of breast and cervical cancer after DIM and I3C supplementation was noted. Despite all health benefit expectation, some studies found that I3C actually promoted or enhanced the development of cancer when administered chronically after the carcinogen (post initiation) to rats. Because the long-term effects of the supplementation of the mentioned compounds on cancer risk in humans are not known, the widespread use of dietary supplements containing natural compounds in humans should be avoided until the potential risks versus benefits are better understood.

A combination of indol-3-carbinol and genistein synergistically induces apoptosis in human colon cancer HT-29 cells by inhibiting Akt phosphorylation and progression of autophagy

Background

The chemopreventive effects of dietary phytochemicals on malignant tumors have been studied extensively because of a relative lack of toxicity. To achieve desirable effects, however, treatment with a single agent mostly requires high doses. Therefore, studies on effective combinations of phytochemicals at relatively low concentrations might contribute to chemopreventive strategies.

Results

Here we found for the first time that co-treatment with I3C and genistein, derived from cruciferous vegetables and soy, respectively, synergistically suppressed the viability of human colon cancer HT-29 cells at concentrations at which each agent alone was ineffective. The suppression of cell viability was due to the induction of a caspase-dependent apoptosis. Moreover, the combination effectively inhibited phosphorylation of Akt followed by dephosphorylation of caspase-9 or down-regulation of XIAP and survivin, which contribute to the induction of apoptosis. In addition, the co-treatment also enhanced the induction of autophagy mediated by the dephosphorylation of mTOR, one of the downstream targets of Akt, whereas the maturation of autophagosomes was inhibited. These results give rise to the possibility that co-treatment with I3C and genistein induces apoptosis through the simultaneous inhibition of Akt activity and progression of the autophagic process. This possibility was examined using inhibitors of Akt combined with inhibitors of autophagy. The combination effectively induced apoptosis, whereas the Akt inhibitor alone did not.

Conclusion

Although in vivo study is further required to evaluate physiological efficacies and toxicity of the combination treatment, our findings might provide a new insight into the development of novel combination therapies/chemoprevention against malignant tumors using dietary phytochemicals.

Phytochemicals as potential chemopreventive and chemotherapeutic agents in hepatocarcinogenesis. Eur J Cancer Prev. 2009;18:13-25. [PMID: 19077560 DOI: 10.1097/cej.0b013e3282f0c090]

Hepatocellular carcinoma (HCC) is the fifth commonest malignancy worldwide and the incidence is rising. Surgery, including transplantation resection, is currently the most effective treatment for HCC; however, recurrence rates are high and long-term survival is poor. Identifying novel chemopreventive and chemotherapeutic agents and targeting them to patients at high risk of developing HCC or following curative treatment may go some way towards improving prognosis. This review examines current knowledge regarding the chemopreventive and chemotherapeutic potential of phytochemicals in heptocarcinogenesis. Both in-vitro and animal studies demonstrate that several phytochemicals, including curcumin, resveratrol, green tea catechins, oltipraz and silibinin, possess promising chemopreventive and chemotherapeutic properties. Despite this, very few clinical trials have been performed. Problems regarding validation of biomarkers, agent delivery, side effects and patient selection are barriers that need to be overcome to determine the potential of such agents in clinical practice.

Single-dose pharmacokinetics and tolerability of absorption-enhanced 3,3'-diindolylmethane in healthy subjects

We have completed a single ascending dose clinical study of the proposed chemopreventive agent 3,3'-diindolylmethane (DIM). The study agent was nutritional-grade, absorption-enhanced BioResponse 3,3'-diindolylmethane (BR-DIM). We determined the safety, tolerability, and pharmacokinetics of single doses of BR-DIM in drug-free, non-smoking, healthy men and women. Groups of four subjects were enrolled for each dose level. After randomization, one subject in each group received placebo whereas three received active BR-DIM. The doses administered were 50, 100, 150, 200, and 300 mg, with the 300-mg dose repeated in an additional group. No BR-DIM-related adverse effects were reported at doses up to 200 mg. At the 300-mg dose, one of six subjects reported mild nausea and headache and one also reported vomiting. Only the latter effect was judged as probably related to the study agent. Analysis of serial plasma samples showed that only one subject at the 50-mg dose had detectable concentrations of DIM. The single 100-mg dose of BR-DIM resulted in a mean maximum plasma concentration (C(max)) of 32 ng/mL and a mean area under the curve (AUC) of 128 h ng/mL, and a single 200-mg dose produced a mean C(max) of 104 ng/mL and a mean AUC of 553 h ng/mL. The single 300-mg dose of BR-DIM resulted in a mean C(max) of 108 ng/mL and a mean AUC of 532 h ng/mL. We conclude that BR-DIM is well tolerated at single doses of up to 200 mg, and that increasing the dose to 300 mg did not result in an increase in C(max).

In vitro antimicrobial activity and the mode of action of indole-3-carbinol against human pathogenic microorganisms

Indole-3-carbinol (I3C) is a naturally occurring constituent of cruciferous vegetables. The aim of this study was to assess the in vitro antimicrobial activity of I3C and its mode of action. By using an NCCLS broth microdilution assay, the activity of I3C was evaluated against human pathogenic microorganisms including clinically isolated antibiotic-resistant bacterial strains. The results indicated that I3C exhibited broad spectrum antimicrobial activities. To elucidate the physiological changes of the fungal cells induced by I3C, we performed a flow cytometric analysis for a cell cycle. The results showed that I3C arrested the cell cycle at the G(2)/M phase in Candida albicans. To understand the antifungal mode of action of I3C, the change in the membrane dynamics was monitored by using fluorescence changing experiments against C. albicans. The results suggest that I3C may exert antifungal activity by disrupting the structure of the cell membrane. The present study indicates that I3C has considerable antimicrobial activity, deserving further investigation for clinical applications.

Discovery and development of sulforaphane as a cancer chemopreventive phytochemical

Sulforaphane (SF) is a phytochemical that displays both anticarcinogenic and anticancer activity. SF modulates many cancer-related events, including susceptibility to carcinogens, cell death, cell cycle, angiogenesis, invasion and metastasis. We review its discovery and development as a cancer chemopreventive agent with the intention of encouraging further research on this important compound and facilitating the identification and development of new phytochemicals for cancer prevention.

Head and neck cancer: a case for inhibition by isothiocyanates and indoles from cruciferous vegetables

Chemical carcinogens derived from cigarettes and other tobacco products, as well as betel quid, paan, and alcohol consumption, are commonly associated with head and neck cancer risk. This is a particularly debilitating cancer, with a high recurrence rate and long-term treatment comorbidities affecting health and lifestyle. Controlling tobacco access or use may be an ideal prevention strategy but may also be challenging or undesired. Individuals, however, may be able to reduce their risk through simple and focused dietary change. Results from epidemiologic studies, basic research, and clinical investigations suggest that a diet rich in cruciferous vegetables may increase carcinogen metabolism, induce apoptosis, and reduce the risk of developing a primary head and neck tumor. This review briefly summarizes head and neck cancer nutritional epidemiology, and then describes the biochemical and epidemiologic literature describing the effects of crucifer consumption on head and neck carcinogenesis. To translate these findings, the strengths and limitations of specific intervention models are discussed, including differences in target populations and the choice of a food-based or pill-based approach for intervention. Addressing these factors in a future intervention may define a low-cost and non-toxic approach to reduce the burden of head and neck cancer.

Herbs or Natural Products That Protect Against Cancer Growth: Part Three of a Four-Part Series

PURPOSE/OBJECTIVES

To provide evidence-based research information about 47 herbs and natural products that have the potential to protect against the development of cancer.

DATA SOURCES

Natural Medicines Comprehensive Database and Lawrence Review of Natural Products-Monograph System. Information about these herbs has been found in evidence-based studies cited in the references.

DATA SYNTHESIS

Early research shows that some herbs and natural products appear to have the potential to prevent cancer growth.

CONCLUSIONS

This preliminary evidence may be useful to healthcare professionals or patients who are concerned about cancer.

IMPLICATIONS FOR NURSING

Oncology nurses who receive this information can become resources for patients or other healthcare professionals.

Gene expression analysis during tumor enhancement by the dietary phytochemical, 3,3'-diindolylmethane, in rainbow trout

Indole-3-carbinol (I3C) and 3,3'-diindolylmethane (DIM), a primary I3C derivative, are known dietary chemopreventive agents also available as supplements. However, I3C has been found to act as a tumor promoter in rat (multi-organ) and trout (liver) models. I3C and DIM were previously found to be estrogenic in trout liver based on toxicogenomic profiles. In this study, we compare the post-initiation effects of DIM and 17beta-estradiol (E2) on aflatoxin B(1) (AFB(1))-induced hepatocarcinogenesis in trout. Trout were initiated as embryos with AFB(1) and juvenile fish were fed diets containing 0, 120 or 400 p.p.m. DIM or 5 p.p.m. E2 for 18 weeks. Tumor incidence was determined at 13 months and found to be significantly elevated in AFB(1)-initiated trout fed either 400 p.p.m. DIM or 5 p.p.m. E2 compared with control animals. To evaluate the mechanism of tumor enhancement, hepatic gene expression profiles were examined in animals fed promotional diets during the course of tumorigenesis and in hepatocellular carcinomas (HCCs) of initiated animals. We demonstrate that DIM alters gene expression profiles similar to E2 in liver samples during tumorigenesis and in HCC tumors. Further, HCCs from animals on DIM and E2 promotional diets had a transcriptional signature indicating decreased invasive or metastatic potential compared with HCCs from control animals. Overall, these findings are the first to demonstrate tumor promotion by DIM. They confirm the importance of estrogenic signaling in the mechanism of promotion by dietary indoles in trout liver and indicate a possible dual effect that enhances tumor incidence and decreases potential for metastasis.

Cruciferous vegetables and human cancer risk: epidemiologic evidence and mechanistic basis

Cruciferous vegetables are a rich source of glucosinolates and their hydrolysis products, including indoles and isothiocyanates, and high intake of cruciferous vegetables has been associated with lower risk of lung and colorectal cancer in some epidemiological studies. Glucosinolate hydrolysis products alter the metabolism or activity of sex hormones in ways that could inhibit the development of hormone-sensitive cancers, but evidence of an inverse association between cruciferous vegetable intake and breast or prostate cancer in humans is limited and inconsistent. Organizations such as the National Cancer Institute recommend the consumption of five to nine servings of fruits and vegetables daily, but separate recommendations for cruciferous vegetables have not been established. Isothiocyanates and indoles derived from the hydrolysis of glucosinolates, such as sulforaphane and indole-3-carbinol (I3C), have been implicated in a variety of anticarcinogenic mechanisms, but deleterious effects also have been reported in some experimental protocols, including tumor promotion over prolonged periods of exposure. Epidemiological studies indicate that human exposure to isothiocyanates and indoles through cruciferous vegetable consumption may decrease cancer risk, but the protective effects may be influenced by individual genetic variation (polymorphisms) in the metabolism and elimination of isothiocyanates from the body. Cooking procedures also affect the bioavailability and intake of glucosinolates and their derivatives. Supplementation with I3C or the related dimer 3,3'-diindolylmethane (DIM) alters urinary estrogen metabolite profiles in women, but the effects of I3C and DIM on breast cancer risk are not known. Small preliminary trials in humans suggest that I3C supplementation may be beneficial in treating conditions related to human papilloma virus infection, such as cervical intraepithelial neoplasia and recurrent respiratory papillomatosis, but larger randomized controlled trials are needed.

Single-Dose and Multiple-Dose Administration of Indole-3-Carbinol to Women: Pharmacokinetics Based on 3,3′-Diindolylmethane

We have completed a phase I trial in women of the proposed chemopreventive natural product indole-3-carbinol (I3C). Women received oral doses of 400, 600, 800, 1,000, and 1,200 mg I3C. Serial plasma samples were analyzed by high-performance liquid chromatography-mass spectrometry for I3C and several of its condensation products. I3C itself was not detectable in plasma. The only detectable I3C-derived product was 3,3'-diindolylmethane (DIM). Mean Cmax for DIM increased from 61 ng/mL at the 400-mg I3C dose to 607 ng/mL following a 1,000-mg dose. No further increase was observed following a 1,200-mg dose. A similar result was obtained for the area under the curve, which increased from 329 h ng/mL at the 400-mg dose to 3,376 h ng/mL after a 1,000-mg dose of I3C. Significant interindividual quantitative variation was seen in plasma DIM values within each dosing group, but the overall profiles were qualitatively similar, with no quantifiable DIM before dosing, tmax at approximately 2 h, and DIM levels near or below 15 ng/mL (the limit of quantitation), by 24 h. Different results were obtained for 14 subjects who received a 400-mg dose of I3C after 8 weeks of twice-daily I3C dosing. Although the predose sampling occurred at least 12 h after the last known ingestion of I3C, 6 of 14 subjects exhibited Cmax for DIM in their predose plasma. Despite this high initial value, plasma DIM for all subjects decreased to near or below the limit of quantitation within the 12-h sampling period. Possible reasons for this disparity between apparent t1/2 of DIM and the high predose values are discussed.

DNA-based electrochemical biosensors for monitoring of bis-indoles as potential antitumoral agents, chemistry, X-ray crystallography

Facile and practical electrochemical DNA bioassay, X-ray diffraction analysis, synthesis and 1H and 13C NMR data of the 5,5'-disubstituted-3,3'-methanediyl-bis-indoles are reported. On the basis of electrochemical measurements we have hypothesized that the analyzed bis-indoles have an effect on human tumor cells due to DNA binding at adenine-thymidine deoxynucleotides rich region in a concentration/substituent dependent manner. Interesting N-H...pi and hydrogen-bonding intermolecular interactions were observed which may differentiate their biological features. The 5,5'-dimethoxy-3,3'-methanediyl-bis-indole (2) was found to reduce considerably the growth of cancer cell lines HOP-92 (lung), A498 (renal) and MDA-MB-231/1TCC (breast). The results indicate that title compounds could be interesting as potential antitumoral chemotherapeutics.

Using salmonid microarrays to understand the dietary modulation of carcinogenesis in rainbow trout

The highlighted article in this issue by Tilton et al. (2005a) is an innovative approach to evaluate the modulation of estrogen receptor (ER) and aryl hydrocarbon (Ah)-receptor pathways as mechanisms underlying indole-3-carbinol (I3C) tumor promotion in rainbow trout (Onchorhynchus mykiss). I3C and its major in vivo component 3,3'-diindolylmethane (DIM) are potent tumor promoters that appear to target both of the aforementioned receptor pathways. However, the relative importance of I3C modulation of ER and AhR-dependent pathways in the promotion of rainbow trout hepatocarcinogenesis has not been established. Previously, researchers within this group reported that I3C promotes aflatoxin B1 (AFB1)-induced trout hepatocarcinogenesis post-initiation at low concentrations in the diet that induce the expression of vitellogenin, a downstream marker for the activation of ER-dependent pathways in fish. Furthermore, the promotional effects of I3C on AFB1 hepatocarcinogenesis in rainbow trout occur at concentrations that differentially induce vitellogenin, but not CYP1A expression. Interestingly, higher I3C concentrations induce the expression of both CYP1A and vitellogenin. Thus, the relative induction of vitellogenin and CYP1A expression, which are respective markers for activation of fish ER and AhR-mediated gene expression, suggest that these pathways may be important for tumor promotion by dietary I3C in trout. Understanding the complexities of I3C-mediated tumor promotion is essential from several perspectives. For example, there is the obvious need to increase our basic understanding of dietary modulation of carcinogenesis. In addition, I3C also exhibits significant antioxidant and cancer chemoprotective effects under certain experimental conditions and in certain models which have led to its recent marketing as a dietary supplement, as well as its development as a possible chemopreventive agent in humans.

3,3′-Diindolylmethane downregulates pro-survival pathway in hormone independent prostate cancer

Epidemiological evidences suggest that the progression and promotion of prostate cancer (CaP) can be modulated by diet. Since all men die with prostate cancer rather than of the disease, it is of particular interest to prevent or delay the progression of the disease by chemopreventive strategies. We have been studying the anticancer properties of compounds present in cruciferous vegetables such as indole-3-carbinol (I3C). Diindolylmethane (DIM) is a dimer of I3C that is formed under acidic conditions and unlike I3C is more stable with higher anti-cancer effects. In the present report, we demonstrate that DIM is a potent anti-proliferative agent compared to I3C in the hormone independent DU 145 CaP cells. The anti-prostate cancer effect is mediated by the inhibition of the Akt signal transduction pathway as DIM, in sharp contrast to I3C, induces the downregulation of Akt, p-Akt, and PI3 kinase. DIM also induced a G1 arrest in DU 145 cells by flow cytometry and downstream concurrent inhibition of cell cycle parameters such as cyclin D1, cdk4, and cdk6. Our data suggest a need for further development of DIM, as a chemopreventive agent for CaP, which justifies epidemiological evidences and molecular targets that are determinants for CaP dissemination/progression. The ingestion of DIM may benefit CaP patients and reduce disease recurrence by eliminating micro-metastases that may be present in patients who undergo radical prostatectomy.

3,3′-Diindolylmethane, a cruciferous vegetable derived synthetic anti-proliferative compound in thyroid disease

Considerable epidemiological evidence exists to link thyroid disease with differing patterns of dietary consumption, in particular, cruciferous vegetables. We have been studying the anti-thyroid cancer (TCa) activity of indole-3-carbinol (I3C) found in cruciferous vegetables and its acid catalyzed dimer, 3,3'-diindolylmethane (DIM). There are no studies as yet to elucidate the effect of these compounds on the altered proliferative patterns in goiter or thyroid neoplasia. In this study, we tested the anti-proliferative effects of I3C and DIM on four different thyroid cancer cell lines representative of papillary (B-CPAP and 8505-C) and follicular carcinoma of the thyroid (CGTH-W-1 and ML-1), and primary human goiter cells. Cell survival and IC50 values for I3C and DIM were calculated by the XTT assay and cell cycle distribution analysis was done by flow cytometry. DIM was found to be a better anti-proliferative agent than I3C in both papillary and follicular TCa resulting in a greater cytotoxic effect at a concentration over three fold lower than predicted by the molar ratio of DIM and I3C. The anti-proliferative activity of DIM in follicular TCa was mediated by a G1 arrest followed by induction of apoptosis. DIM also inhibited the growth of primary goiter cells by 70% compared to untreated controls. Contrary to traditional belief that cruciferous vegetables are "goitrogenic", DIM has anti-proliferative effects in glandular thyroid proliferative disease. Our preclinical studies provide a strong rationale for the clinical exploration of DIM as an adjuvant to surgery in thyroid proliferative disease.

Effects of analogs of indole-3-carbinol cyclic trimerization product in human breast cancer cells

5,6,11,12,17,18-Hexahydrocyclonona[1,2-b:4,5-b*:7,8-b**]triindole (CTr) is a major digestive product of indole-3-carbinol (I3C) from Brassica vegetables and exhibits strong estrogenic activities. CTr increases proliferation of estrogen-dependent breast tumor cells, binds with strong affinity for the estrogen receptor-alpha (ERalpha), and activates expression of estrogen (E(2))-dependent genes. To begin to examine the structural features that determine the biological activity of CTr, we prepared and studied the effects of two analogs, 9,18-dihydro-12H-[1,2,5]trithionino[3,4-b:6,7-b*:9,8-b**]triindole (S(3)CTr) and 5,6,11,12,17,18-hexahydro-5,11,17-trimethylcyclonona[1,2-b:4,5-b*:7,8-b**]triindole (Me(3)CTr). N-Methylation of CTr completely ablated the estrogenic activities of CTr. In the dose range in which CTr was clearly estrogenic, Me(3)CTr exhibited no detectable effect on cell growth, ERalpha binding to E(2), or ERalpha-responsive gene expression. S(3)CTr showed mixed ERalpha agonist activities. It bound to the ERalpha and activated receptor binding with DNA, weakly activated expression of transfected E(2)-responsive reporter gene constructs, and strongly inhibited the E(2)-induced activation of these reporter constructs. S(3)CTr activated aryl hydrocarbon receptor (AhR)-mediated pathways, consistent with the moderately strong binding affinity of S(3)CTr for the AhR. Comparisons of the conformational characteristics among CTr and its two analogs indicated that the estrogenic effects of CTr are highly sensitive to apparently minor structural modifications, and further supported the hypothesis for a central role of hydrogen bonding around the nitrogen atom in CTr binding to the ligand binding site of ERalpha.

Chemopreventive Effect of Indole-3-Carbinol on Induction of Preneoplastic Altered Hepatic Foci

Indole-3-carbinol (I3C) is a cleavage product of glucobrassicanin, a natural compound present in a wide variety of plant food substances including members of the family Cruciferae. I3C is known to possess cancer-chemopreventive potential in various animal models. The present study reveals the protective effect of I3C on the development of diethylnitrosamine (DEN)-initiated and 2-acetylaminofluorene (AAF)-promoted preneoplastic, altered hepatic foci (AHF) in Wistar rats. I3C was given at dose levels of 0.5 and 1 mg/kg body weight for five consecutive days along with DEN and AAF. AHF were scored and analyzed by quantitative stereology using the Image Analysis System from frozen liver sections stained for positive and negative biological markers of AHF, that is, glutathione S-transferase (GST-P), gamma-glutamyl transpeptidase (GGT), glucose-6-phosphatase (G6Pase), adenosine triphosphatase (ATPase), and alkaline phosphatase (AlkPase). Results revealed the chemopreventive effect of I3C on the DEN-initiated AHF in Wistar rats. The expression of G6Pase, ATPase, and AlkPase was restored in the I3C-supplemented animal. Similarly the induced expression GST-P and GGT also decreased in the animals with I3C administration. The recovery of altered levels of these biomarkers was of comparatively higher magnitude in the animals given a higher dose of I3C (1 mg/kg body weight) in comparison with the animals given 0.5 mg/kg body weight dose of I3C, although no dose-dependence pattern was recorded in I3C-supplemented groups. These results thus suggest the chemopreventive effect of I3C in rat hepatocarcinogenesis by suppressing DEN- and AAF-induced AHF development.

Sequential analysis of development of invasive thyroid follicular cell carcinomas in inflamed capsular regions of rats treated with sulfadimethoxine after N-bis(2-hydroxypropyl)nitrosamine-initiation

A 2-stage thyroid follicular carcinogenesis model in rats initiated with N-bis(2-hydroxypropyl)nitrosamine (DHPN) is widely used to detect modifying effects of chemicals on thyroid carcinogenesis. A number of goitrogens are known to strongly promote carcinogenesis, and the carcinomas often originate adjacent to the thyroid capsule and show invasive growth into the capsule or adjacent tissues. To clarify mechanisms of progression to invasive carcinomas, we sequentially evaluated histopathological and immunohistochemical characteristics of thyroids in male F344 rats treated with sulfadimethoxine (SDM, 0.1% in drinking water) for 0-10 weeks beginning 1 week after DHPN initiation (2800 mg/kg body weight, single s.c. injection). In DHPN-SDM-treated rats, multiple focal hyperplasias and adenomas developed in thyroid follicular parenchyma at weeks 4 to 6. Apart from the proliferative lesions, capsular thickening with inflammatory cell infiltration, mainly consisting of macrophages, and migration of follicular epithelium into the capsule were also observed. Focal hyperplasias/adenomas adjacent to the capsule progressively developed to invasive carcinomas at weeks 6 to 10. In thyroid parenchyma, malignant lesions were seldom observed. With SDM-treatment alone, although no neoplastic lesions were observed, capsular thickening with inflammation and epithelial migration resulted in intracapsular residual follicles. Intracapsular residual follicular cells as well as invasive and intrathyroidal carcinoma cells generally showed increased cell proliferative activity, coincidental with cytoplasmic/nuclear positivity for beta-catenin. These results suggested that beta-catenin activation related to capsular inflammation may play a role in development of invasive carcinomas but is insufficient for tumor formation by itself. Whether this is associated with mutations in the beta-catenin gene remains to be clarified.

Effect of common Brassica vegetables (Brussels sprouts and red cabbage) on the development of preneoplastic lesions induced by 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) in liver and colon of Fischer 344 rats

Aim of the present study was the investigation of effects of juices from commonly consumed Brassica vegetables (two cultivars of Brussels sprouts and two cultivars of red cabbage) on formation and development of preneoplastic lesions in colons (aberrant crypt foci, ACF) and livers (glutathione-S-transferase placental form, GST-P+) in male F344 rats. The foci were induced by 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), a widespread carcinogenic heterocyclic aromatic amine which is found in fried meats. Recently, we reported on pronounced protective effects in the two-organ foci model when the vegetable juices were given during the carcinogen treatment but several findings by other groups indicated that breakdown products of glucosinolates contained in Brassica vegetables cause tumour promotion in various organs of laboratory rodents. In the present study, the animals received the juices in the drinking water (5%) over a period of 20 days after treatment with IQ (100 mg/kg bw on 10 alternate days). To increase the foci yield (which facilitates the detection of modifying effects), the animals were fed with a modified (high fat, fibre free) AIN-76 diet. With exception of the sprout variety "Cyrus", all juices lowered the number of GST-P+ foci as well as the foci area in the liver, but none of these effects was statistically significant. In the colon, none of the juices had an impact on crypt multiplicity (number of crypts/focus), whereas the number of ACF was decreased; only with the sprout variety Maximus the protective effect was significant (reduction 49%). The present findings show that administration of vegetable juices to the animals after the carcinogen does not increase the number and size of IQ-induced preneoplastic lesions in liver and colon.

Post-initiation modulating effects of allyl sulfides in rat hepatocarcinogenesis

Effects of administration of diallyl sulfide (DAS) and diallyl disulfide (DADS) on the promotion stage of hepatocarcinogenesis were investigated in rats using the Ito model. They were compared with those of phenobarbital (PB), a well-known liver promoter in rats. Initiation was induced by a single dose of N-nitrosodiethylamine (NDEA) and 3 weeks later, a partial hepatectomy was conducted. Two weeks after the NDEA injection, rats received either 0.05% allyl sulfides, PB or both in their diet for 8 weeks. Feeding with DAS increased the number of liver preneoplastic foci by 63% with respect to the untreated group. However, rats fed DAS showed a lower foci development than rats fed PB. The DADS group did not differ from control group for any of the measured morphometric parameters. Simultaneous administration of DADS with PB partially reduced the promotional activity of PB whereas DAS co-treatment did not modify PB properties. These findings confirm that DAS can act as a promoter in rat liver but exerts no co-promoting effect. Conversely, DADS was found to have promotion-inhibiting ability, suggesting that DADS has greater value than DAS as a chemopreventive agent.