A novel mechanism of chemoprevention by sulforaphane : inhibition of histone deacetylase

Targeting the epigenome, including the use of histone deacetylase (HDAC) inhibitors, is a novel strategy for cancer chemoprevention. Sulforaphane (SFN), a compound found at high levels in broccoli and broccoli sprouts, is a potent inducer of Phase 2 detoxification enzymes and inhibits tumorigenesis in animal models. SFN also has a marked effect on cell cycle checkpoint controls and cell survival/apoptosis in various cancer cells, through mechanisms that are poorly understood. Based on the structure of known histone deacetylase inhibitors, it was hypothesized that SFN may possess HDAC inhibitory properties. Initial studies confirmed that, indeed, at physiologically-relevant concentrations, SFN inhibited HDAC activity in human colorectal cancer cells, with a concomitant increase in acetylated histones H3 and H4, induction of p21 expression, and increased acetylated histone H4 associated with the P21 promoter. A metabolite of SFN, SFN-Cysteine, was found to be the active HDAC inhibitor. Furthermore, in BPH-1, LnCaP, and PC-3 human prostate epithelial cells, SFN inhibited HDAC activity and increased acetylation of histones. SFN also induced p21 expression, with an increase in acetylated histone H4 associated with the P21 promoter in BPH-1 cells. The downstream effects of HDAC inhibition by SFN included induction of pro-apoptotic proteins and repression of anti-apoptotic proteins, and an increase in multi-caspase activity. Dietary SFN suppressed the growth of human prostate cancer PC-3 xenografts and inhibited HDAC activity in the xenografts, peripheral blood mononuclear cells (PBMC), and prostates. In time-course studies, a single oral dose of SFN induced histone acetylation at 6 and 24 h in mouse colonic mucosa, and long-term dietary SFN treatment increased histone acetylation in the ileum, colon, PBMC, and prostates. Moreover, dietary SFN suppressed intestinal tumorigenesis significantly in Apc[superscrip min] mice, with an increase in acetylated histones detected in the normal-looking ileum and polyps and polyps from the colon. Overall, the data presented in this thesis support a novel mechanism for chemoprevention by SFN in vivo, through inhibition of histone deacetylase. The findings also imply that SFN will offer significant protection against at least two of the major cancer killers in the US, namely colon and prostate cancer

Barriers to Completing Colonoscopy Screenings

Background: - Colon cancer is the second leading cause of cancer death in the United States and the third leading cause of cancer death in Vermont. - Colon cancer progression may be prevented by removing precancerous polyps found on colonoscopy screening. -Vermont ranks among the states with the best colon cancer screening rates, but there is room for improvement. In 2006, 55.5% of Vermonters over 50 years of age had undergone a sigmoidoscopy or colonoscopy within the last 5 years. Vermont’s public health goal is to raise this percentage of screened individuals to 65% by 2010. - Vermont medical institutions have the resources to perform screening colonoscopies on all Vermonters over 50 years of age. - Although primary care physician (PCP) recommendations increase the likelihood of a patient completing a colonoscopy screening, a substantial number of patients referred for screening colonoscopies do not complete their appointments.https://scholarworks.uvm.edu/comphp_gallery/1004/thumbnail.jp

Broccoli or Sulforaphane:Is It the Source or Dose That Matters?

There is robust epidemiological evidence for the beneficial effects of broccoli consumption on health, many of them clearly mediated by the isothiocyanate sulforaphane. Present in the plant as its precursor, glucoraphanin, sulforaphane is formed through the actions of myrosinase, a β-thioglucosidase present in either the plant tissue or the mammalian microbiome. Since first isolated from broccoli and demonstrated to have cancer chemoprotective properties in rats in the early 1990s, over 3000 publications have described its efficacy in rodent disease models, underlying mechanisms of action or, to date, over 50 clinical trials examining pharmacokinetics, pharmacodynamics and disease mitigation. This review evaluates the current state of knowledge regarding the relationships between formulation (e.g., plants, sprouts, beverages, supplements), bioavailability and efficacy, and the doses of glucoraphanin and/or sulforaphane that have been used in pre-clinical and clinical studies. We pay special attention to the challenges for better integration of animal model and clinical studies, particularly with regard to selection of dose and route of administration. More effort is required to elucidate underlying mechanisms of action and to develop and validate biomarkers of pharmacodynamic action in humans. A sobering lesson is that changes in approach will be required to implement a public health paradigm for dispensing benefit across all spectrums of the global population

When Food Meets Man: the Contribution of Epigenetics to Health

Post-translational modifications of chromatin contribute to the epigenetic control of gene transcription. The response to food intake and individual nutrients also includes epigenetic events. Bile acids are necessary for lipid digestion and absorption, and more recently have emerged as signaling molecules. Their synthesis is transcriptionally regulated also in relation to the fasted-to-fed cycle, and interestingly, the underlying mechanisms include chromatin remodeling at promoters of key genes involved in their metabolism. Several compounds present in nutrients affect gene transcription through epigenetic mechanisms and recent studies demonstrate that, beyond the well known anti-cancer properties, they beneficially affect energy metabolism

Sulforaphane Causes Epigenetic Repression of hTERT Expression in Human Breast Cancer Cell Lines

Sulforaphane (SFN), an isothiocyanate found in cruciferous vegetables, is a common dietary component that has histone deacetylase inhibition activity and exciting potential in cancer prevention. The mechanisms by which SFN imparts its chemopreventive properties are of considerable interest and little is known of its preventive potential for breast cancer. expression facilitated the induction of cellular apoptosis in human breast cancer cells.Collectively, our results provide novel insights into SFN-mediated epigenetic down-regulation of telomerase in breast cancer prevention and may open new avenues for approaches to SFN-mediated cancer prevention

Dietary garlic and hip osteoarthritis: evidence of a protective effect and putative mechanism of action

Background Patterns of food intake and prevalent osteoarthritis of the hand, hip, and knee were studied using the twin design to limit the effect of confounding factors. Compounds found in associated food groups were further studied in vitro. Methods Cross-sectional study conducted in a large population-based volunteer cohort of twins. Food intake was evaluated using the Food Frequency Questionnaire; OA was determined using plain radiographs. Analyses were adjusted for age, BMI and physical activity. Subsequent in vitro studies examined the effects of allium-derived compounds on the expression of matrix-degrading proteases in SW1353 chondrosarcoma cells. Results Data were available, depending on phenotype, for 654-1082 of 1086 female twins (median age 58.9 years; range 46-77). Trends in dietary analysis revealed a specific pattern of dietary intake, that high in fruit and vegetables, showed an inverse association with hip OA (p = 0.022). Consumption of 'non-citrus fruit' (p = 0.015) and 'alliums' (p = 0.029) had the strongest protective effect. Alliums contain diallyl disulphide which was shown to abrogate cytokine-induced matrix metalloproteinase expression. Conclusions Studies of diet are notorious for their confounding by lifestyle effects. While taking account of BMI, the data show an independent effect of a diet high in fruit and vegetables, suggesting it to be protective against radiographic hip OA. Furthermore, diallyl disulphide, a compound found in garlic and other alliums, represses the expression of matrix-degrading proteases in chondrocyte-like cells, providing a potential mechanism of action

Supplementation of the diet by exogenous myrosinase via mustard seeds to increase the bioavailability of sulforaphane in healthy human subjects after the consumption of cooked broccoli

Broccoli contains the glucosinolate glucoraphanin which, in the presence of myrosinase, can hydrolyse to the isothiocyanate sulforaphane, reported to have anti-carcinogenic activity. However, the myrosinase enzyme is denatured on cooking. Addition of an active source of myrosinase, such as from powdered mustard seed, to cooked brassica vegetables can increase the release of health beneficial isothiocyanates, however this has not previously been proven in-vivo. The concentration of sulforaphane metabolite (sulforaphane N-acetyl-L-cysteine (SF-NAC) in 12 healthy adults after the consumption of 200g cooked broccoli, with and without 1 g powdered brown mustard, was studied in a randomized crossover design. During the 24 hour period following consumption of the study sample all urine was collected. SF-NAC content was assayed by HPLC. When study subjects ingested cooked broccoli alone, mean urinary SF-NAC excreted was 9.8 ± 5.1 µmol per g creatinine, whilst when cooked broccoli was consumed with mustard powder this increased significantly to 44.7 ± 33.9 µmol SF-NAC per g creatinine. These results conclude that when powdered brown mustard is added to cooked broccoli the bioavailability of sulforaphane is over four times greater than that from cooked broccoli ingested alone

The isothiocyanate sulforaphane inhibits mTOR in an NRF2-independent manner

BACKGROUND: The isothiocyanate sulforaphane (SFN) has multiple protein targets in mammalian cells, affecting processes of fundamental importance for the maintenance of cellular homeostasis, among which are those regulated by the stress response transcription factor nuclear factor erythroid 2 p45-related factor 2 (NRF2) and the serine/threonine protein kinase mechanistic target of rapamycin (mTOR). Whereas the way by which SFN activates NRF2 is well established, the molecular mechanism(s) of how SFN inhibits mTOR is not understood. HYPOTHESIS/PURPOSE: The aim of this study was to investigate the mechanism(s) by which SFN inhibits mTOR STUDY DESIGN AND METHODS: We used the human osteosarcoma cell line U2OS and its CRISPR/Cas9-generated NRF2-knockout counterpart to test the requirement for NRF2 and the involvement of mTOR regulators in the SFN-mediated inhibition of mTOR. RESULTS: SFN inhibits mTOR in a concentration- and time-dependent manner, and this inhibition occurs in the presence or in the absence of NRF2. The phosphatidylinositol 3-kinase (PI3K)-AKT/protein kinase B (PKB) is a positive regulator of mTOR, and treatment with SFN caused an increase in the phosphorylation of AKT at T308 and S473, two phosphorylation sites associated with AKT activation. Interestingly however, the levels of pS552 β-catenin, an AKT phosphorylation site, were decreased, suggesting that the catalytic activity of AKT was inhibited. In addition, SFN inhibited the activity of the cytoplasmic histone deacetylase 6 (HDAC6), the inhibition of which has been reported to promote the acetylation and decreases the kinase activity of AKT. CONCLUSION: SFN inhibits HDAC6 and decreases the catalytic activity of AKT, and this partially explains the mechanism by which SFN inhibits mTOR

Epigenetics Offer New Horizons for Colorectal Cancer Prevention

In recent years, colorectal cancer (CRC) incidence has been increasing to become a major cause of morbidity and mortality worldwide from cancers, with high rates in westernized societies and increasing rates in developing countries. Epigenetic modifications including changes in DNA methylation, histone modifications, and non-coding RNAs play a critical role in carcinogenesis. Epidemiological data suggest that, in comparison to other cancers, these alterations are particularly common within the gastrointestinal tract. To explain these observations, environmental factors and especially diet were suggested to both prevent and induce CRC. Epigenetic alterations are, in contrast to genetic modifications, potentially reversible, making the use of dietary agents a promising approach in CRC for the development of chemopreventive strategies targeting epigenetic mechanisms. This review focuses on CRC-related epigenetic alterations as a rationale for various levels of prevention strategies and their potential modulation by natural dietary compounds