Green Cancer Prevention and Beyond.

The concept of green chemoprevention was introduced in 2012 by Drs. Jed Fahey and Thomas Kensler as whole-plant foods and/or extract-based interventions demonstrating cancer prevention activity. Refining concepts and research demonstrating proof-of-principle approaches are highlighted within this review. Early approaches included extensively investigated whole foods, including broccoli sprouts and black raspberries showing dose-responsive effects across a range of activities in both animals and humans with minimal or no apparent toxicity. A recent randomized crossover trial evaluating the detoxification of tobacco carcinogens by a broccoli seed and sprout extract in the high-risk cohort of current smokers highlights the use of a dietary supplement as a potential next-generation green chemoprevention or green cancer prevention approach. Challenges are addressed, including the selection of dose, duration and mode of delivery, choice of control group, and standardization of the plant food or extract. Identification and characterization of molecular targets and careful selection of high-risk cohorts for study are additional important considerations when designing studies. Goals for precision green cancer prevention include acquiring robust evidence from carefully controlled human studies linking plant foods, extracts, and compounds to modulation of targets for cancer risk reduction in individual cancer types.

Study on Human Urinary Metabolic Profiles after Consumption of Kale and Daikon Radish using a High-resolution Mass Spectrometry-Based Non-targeted and Targeted Metabolomic Approach.

In the present study, urine samples were collected from healthy human volunteers to determine the metabolic fates of phenolic compounds and glucosinolates after a single meal of kale and daikon radish. The major glucosinolates and phenolic compounds in kale and daikon radish were measured. The urinary metabolome after feeding at different time periods was investigated. A targeted metabolite analysis method was developed based on the known metabolic pathways for glucosinolates and phenolic compounds. Using a targeted approach, a total of 18 metabolites were found in urine: 4 from phenolic compounds and 14 from glucosinolates. Among these metabolites, 4-methylsulfinyl-3-butenyl isothiocyanate, 4-methylsulfinyl-3-butenyl isothiocyanate-cysteine, and 4-methylsulfinyl-3-butenylglucosinolate-N-acetyl cysteine were reported for the first time in human urine. The combination of non-targeted and targeted metabolomic approaches can gain a full metabolite profile for human dietary intervention studies.

BMI Is Associated With Increased Plasma and Urine Appearance of Glucosinolate Metabolites After Consumption of Cooked Broccoli.

Introduction: Preclinical studies suggest that brassica vegetable diets decrease cancer risk, but epidemiological studies show varied effects, resulting in uncertainty about any health impact of brassicas. Factors controlling absorption of glucosinolate metabolites may relate to inconsistent results. We reported previously that subjects with BMI > 26 kg/m2 (HiBMI), given cooked broccoli plus raw daikon radish (as a source of plant myrosinase) daily for 17 days, had lower glucosinolate metabolite absorption than subjects given a single broccoli meal. This difference was not seen in subjects with BMI < 26 kg/m2 (LoBMI). Our objective in this current study was to determine whether a similar response occurred when cooked broccoli was consumed without a source of plant myrosinase. Methods: In a randomized crossover study (n = 18), subjects consumed no broccoli for 16 days or the same diet with 200 g of cooked broccoli daily for 15 days and 100 g of broccoli on day 16. On day 17, all subjects consumed 200 g of cooked broccoli. Plasma and urine were collected for 24 h and analyzed for glucosinolate metabolites by LC-MS. Results: There was no effect of diet alone or interaction of diet with BMI. However, absorption doubled in HiBMI subjects (AUC 219%, plasma mass of metabolites 202% compared to values for LoBMI subjects) and time to peak plasma metabolite values and 24-h urinary metabolites also increased, to 127 and 177% of LoBMI values, respectively. Conclusion: BMI impacts absorption and metabolism of glucosinolates from cooked broccoli, and this association must be further elucidated for more efficacious dietary recommendations. Clinical Trial Registration: This trial was registered at clinicaltrials.gov (NCT03013465).

Knowledge gaps in understanding the metabolic and clinical effects of excess folates/folic acid: a summary, and perspectives, from an NIH workshop.

Folate, an essential nutrient found naturally in foods in a reduced form, is present in dietary supplements and fortified foods in an oxidized synthetic form (folic acid). There is widespread agreement that maintaining adequate folate status is critical to prevent diseases due to folate inadequacy (e.g., anemia, birth defects, and cancer). However, there are concerns of potential adverse effects of excess folic acid intake and/or elevated folate status, with the original concern focused on exacerbation of clinical effects of vitamin B-12 deficiency and its role in neurocognitive health. More recently, animal and observational studies have suggested potential adverse effects on cancer risk, birth outcomes, and other diseases. Observations indicating adverse effects from excess folic acid intake, elevated folate status, and unmetabolized folic acid (UMFA) remain inconclusive; the data do not provide the evidence needed to affect public health recommendations. Moreover, strong biological and mechanistic premises connecting elevated folic acid intake, UMFA, and/or high folate status to adverse health outcomes are lacking. However, the body of evidence on potential adverse health outcomes indicates the need for comprehensive research to clarify these issues and bridge knowledge gaps. Three key research questions encompass the additional research needed to establish whether high folic acid or total folate intake contributes to disease risk. 1) Does UMFA affect biological pathways leading to adverse health effects? 2) Does elevated folate status resulting from any form of folate intake affect vitamin B-12 function and its roles in sustaining health? 3) Does elevated folate intake, regardless of form, affect biological pathways leading to adverse health effects other than those linked to vitamin B-12 function? This article summarizes the proceedings of an August 2019 NIH expert workshop focused on addressing these research areas.

The Many Faces of Obesity and Its Influence on Breast Cancer Risk.

Obesity is associated with increased risk of breast and other cancers. However, the complexity of the underlying mechanisms, together with the interplay of diet and physical activity-contributing to energy balance-and the role of adipose tissue, pose challenges to our understanding of the basis of this increased risk. Epidemiologic studies have documented a higher obesity prevalence in US black women compared to white women. Elucidation of the contribution of potential biological differences among racially distinct groups to their differences in breast cancer (BC) risk and mortality have been topics of considerable interest in recent years. The racial and ethnic variation in body fat distribution may account for at least part of the differences in breast cancer rates in these populations. Yet, while black women exhibit higher rates of obesity compared to white women, this does not translate directly into higher rates of BC. In fact, overall, BC in black women occurs with a lower incidence than BC in white women. Obesity is a known risk factor for postmenopausal breast cancer, and growing evidence suggests that abdominal obesity, also known as central obesity, may increase risk for triple negative breast cancer, which is more common in premenopausal women. The positive association of postmenopausal BC risk and specifically estrogen receptor (ER)-positive BC, is presumably due largely to accumulation of estrogen in the adipose tissue of the breast and other tissues. Of the two main types of adipose tissue-subcutaneous and visceral-visceral adipocytes are more active metabolically. Such adipose tissue harbors multiple molecular entities that promote carcinogenesis: endocrine molecules/hormones, immunologic factors, inflammatory cytokines, metabolic alterations, and other components of the microenvironment. Expression of these culpable entities is largely regulated by epigenetic mechanisms. The interrelationship between these entities and drivers of epigenetic alteration are critical to the regulation of pathways connecting obesity and cancer risk. Initiatives to counteract the carcinogenic effects of obesity have primarily involved modulation of energy balance by diet. However, targeting of specific molecular abnormalities characterizing adiposity offers an alternative approach to preventing cancer. Our goal in this review is to first discuss the major mechanisms contributing to the obesity-breast cancer link. We will also consider race, specifically black/white differences, as they relate to the association of obesity with breast cancer risk. Then we will enumerate strategies targeting these mechanisms to reduce BC risk, in large part by way of dietary interventions with potential to mitigate the cancer-promoting components of adiposity.

Absorption and metabolism of isothiocyanates formed from broccoli glucosinolates: effects of BMI and daily consumption in a randomised clinical trial.

Sulphoraphane originates from glucoraphanin in broccoli and is associated with anti-cancer effects. A preclinical study suggested that daily consumption of broccoli may increase the production of sulphoraphane and sulphoraphane metabolites available for absorption. The objective of this study was to determine whether daily broccoli consumption alters the absorption and metabolism of isothiocyanates derived from broccoli glucosinolates. We conducted a randomised cross-over human study (n 18) balanced for BMI and glutathione S-transferase µ 1 (GSTM1) genotype in which subjects consumed a control diet with no broccoli (NB) for 16 d or the same diet with 200 g of cooked broccoli and 20 g of raw daikon radish daily for 15 d (daily broccoli, DB) and 100 g of broccoli and 10 g of daikon radish on day 16. On day 17, all subjects consumed a meal of 200 g of broccoli and 20 g of daikon radish. Plasma and urine were collected for 24 h and analysed for sulphoraphane and metabolites of sulphoraphane and erucin by triple quadrupole tandem MS. For subjects with BMI >26 kg/m2 (median), plasma AUC and urinary excretion rates of total metabolites were higher on the NB diet than on the DB diet, whereas for subjects with BMI <26 kg/m2, plasma AUC and urinary excretion rates were higher on the DB diet than on the NB diet. Daily consumption of broccoli interacted with BMI but not GSTM1 genotype to affect plasma concentrations and urinary excretion of glucosinolate-derived compounds believed to confer protection against cancer. This trial was registered as NCT02346812.

Inhibition of the Cell Death Pathway in Nonalcoholic Steatohepatitis (NASH)-Related Hepatocarcinogenesis Is Associated with Histone H4 lysine 16 Deacetylation.

Hepatocellular carcinoma (HCC) is one of the most aggressive human cancers, and its incidence is steadily increasing worldwide. Recent epidemiologic findings have suggested that the increased incidence of HCC is associated with obesity, type II diabetes mellitus, and nonalcoholic steatohepatitis (NASH); however, the mechanisms and the molecular pathogenesis of NASH-related HCC are not fully understood. To elucidate the underlying mechanisms of the development of NASH-related HCC, we investigated the hepatic transcriptomic and histone modification profiles in Stelic Animal Model mice, the first animal model of NASH-related HCC to resemble the disease pathogenesis in humans. The results demonstrate that the development of NASH-related HCC is characterized by progressive transcriptomic alterations, global loss of histone H4 lysine 20 trimethylation (H4K20me3), and global and gene-specific deacetylation of histone H4 lysine 16 (H4K16). Pathway analysis of the entire set of differentially expressed genes indicated that the inhibition of cell death pathway was the most prominent alteration, and this was facilitated by persistent gene-specific histone H4K16 deacetylation. Mechanistically, deacetylation of histone H4K16 was associated with downregulation of lysine acetyltransferase KAT8, which was driven by overexpression of its inhibitor nuclear protein 1 (Nupr1). The results of this study identified a reduction of global and gene-specific histone H4K16 acetylation as a key pathophysiologic mechanism contributing to the development of NASH-derived HCC and emphasized the importance of epigenetic alterations as diagnostic and therapeutic targets for HCC.Implications: Histone H4K16 deacetylation induces silencing of genes related to the cell death that occurred during the development of NASH-related HCC. Mol Cancer Res; 15(9); 1163-72. ©2017 AACR.

NCI Funding Trends and Priorities in Physical Activity and Energy Balance Research Among Cancer Survivors.

There is considerable evidence that a healthy lifestyle consisting of physical activity, healthy diet, and weight control is associated with reduced risk of morbidity and mortality after cancer. However, these behavioral interventions are not widely adopted in practice or community settings. Integrating heath behavior change interventions into standard survivorship care for the growing number of cancer survivors requires an understanding of the current state of the science and a coordinated scientific agenda for the future with focused attention in several priority areas. To facilitate this goal, this paper presents trends over the past decade of the National Cancer Institute (NCI) research portfolio, fiscal year 2004 to 2014, by funding mechanism, research focus, research design and methodology, primary study exposures and outcomes, and study team expertise and composition. These data inform a prioritized research agenda for the next decade focused on demonstrating value and feasibility and creating desire for health behavior change interventions at multiple levels including the survivor, clinician, and healthcare payer to facilitate the development and implementation of appropriately targeted, adaptive, effective, and sustainable programs for all survivors.

Garlic and onions: their cancer prevention properties.

The Allium genus includes garlic, onions, shallots, leeks, and chives. These vegetables are popular in cuisines worldwide and are valued for their potential medicinal properties. Epidemiologic studies, while limited in their abilities to assess Allium consumption, indicate some associations of Allium vegetable consumption with decreased risk of cancer, particularly cancers of the gastrointestinal tract. Limited intervention studies have been conducted to support these associations. The majority of supportive evidence on Allium vegetables cancer-preventive effects comes from mechanistic studies. These studies highlight potential mechanisms of individual sulfur-containing compounds and of various preparations and extracts of these vegetables, including decreased bioactivation of carcinogens, antimicrobial activities, and redox modification. Allium vegetables and their components have effects at each stage of carcinogenesis and affect many biologic processes that modify cancer risk. This review discusses the cancer-preventive effects of Allium vegetables, particularly garlic and onions, and their bioactive sulfur compounds and highlights research gaps.

Interstrain differences in the progression of nonalcoholic steatohepatitis to fibrosis in mice are associated with altered hepatic iron metabolism.

Nonalcoholic fatty liver disease (NAFLD) is a major health problem worldwide. Currently, there is a lack of conclusive information to clarify the molecular events and mechanisms responsible for the progression of NAFLD to fibrosis and cirrhosis and, more importantly, for differences in interindividual disease severity. The aim of this study was to investigate a role of interindividual differences in iron metabolism among inbred mouse strains in the pathogenesis and severity of fibrosis in a model of NAFLD. Feeding male A/J, 129S1/SvImJ and WSB/EiJ mice a choline- and folate-deficient diet caused NAFLD-associated liver injury and iron metabolism abnormalities, especially in WSB/EiJ mice. NAFLD-associated fibrogenesis was correlated with a marked strain- and injury-dependent increase in the expression of iron metabolism genes, especially transferrin receptor (Tfrc), ferritin heavy chain (Fth1), and solute carrier family 40 (iron-regulated transporter), member 1 (Slc40a1, Fpn1) and their related proteins, and pronounced down-regulation of the iron regulatory protein 1 (IRP1), with the magnitude being A/J<129S1/SvImJ

The emerging role of microRNAs and nutrition in modulating health and disease.

Understanding the molecular mechanisms that inform how diet and dietary supplements influence health and disease is an active research area. One such mechanism concerns the role of diet in modulating the activity and function of microRNAs (miRNAs). miRNAs are small noncoding RNA molecules that are involved in posttranscriptional gene silencing and have been shown to control gene expression in diverse biological processes including development, differentiation, cell proliferation, metabolism, and inflammation as well as in human diseases. Recent evidence described in this review highlights how dietary factors may influence cancer, cardiovascular disease, type 2 diabetes mellitus, obesity, and nonalcoholic fatty liver disease through modulation of miRNA expression. Additionally, circulating miRNAs are emerging as putative biomarkers of disease, susceptibility, and perhaps dietary exposure. Research needs to move beyond associations in cells and animals to understanding the direct effects of diet and dietary supplements on miRNA expression and function in human health and disease.

Epigenetic research in cancer epidemiology: trends, opportunities, and challenges.

Epigenetics is emerging as an important field in cancer epidemiology that promises to provide insights into gene regulation and facilitate cancer control throughout the cancer care continuum. Increasingly, investigators are incorporating epigenetic analysis into the studies of etiology and outcomes. To understand current progress and trends in the inclusion of epigenetics in cancer epidemiology, we evaluated the published literature and the National Cancer Institute (NCI)-supported research grant awards in this field to identify trends in epigenetics research. We present a summary of the epidemiologic studies in NCI's grant portfolio (from January 2005 through December 2012) and in the scientific literature published during the same period, irrespective of support from the NCI. Blood cells and tumor tissue were the most commonly used biospecimens in these studies, although buccal cells, cervical cells, sputum, and stool samples were also used. DNA methylation profiling was the focus of the majority of studies, but several studies also measured microRNA profiles. We illustrate here the current status of epidemiologic studies that are evaluating epigenetic changes in large populations. The incorporation of epigenomic assessments in cancer epidemiology studies has and is likely to continue to provide important insights into the field of cancer research.

Transcriptomic responses provide a new mechanistic basis for the chemopreventive effects of folic acid and tributyrin in rat liver carcinogenesis.

The steady increase in the incidence and mortality of hepatocellular carcinoma (HCC) signifies a crucial need to understand better its pathogenesis to improve clinical management and prevention of the disease. The aim of this study was to investigate molecular mechanisms for the chemopreventive effects of folic acid and tributyrin alone or in combination on rat hepatocarcinogenesis. Male Wistar rats were subjected to a classic "resistant hepatocyte" model of liver carcinogenesis and treated with folic acid and tributyrin alone or in combination for 5 weeks during promotion stage. Treatment with folic acid and tributyrin alone or in combination strongly inhibited the development of glutathione-S-transferase placental form (GSTP)-positive foci. Microarray analysis showed significant changes in gene expression. A total of 498, 655 and 940 of differentially expressed genes, involved in cell cycle, p53-signaling, angiogenesis and Wnt pathways, was identified in the livers of rats treated with folic acid, tributyrin or folic acid and tributyrin. A detailed analysis of these differentially expressed genes revealed that treatments inhibited angiogenesis in the preneoplastic livers. This was evidenced by the fact that 30 out of 77 differentially expressed genes common to all three treatments are involved in the regulation of the angiogenesis pathway. The inhibition of angiogenesis was confirmed by reduced levels of CD34 protein. In conclusion, the tumor-suppressing activity of folic acid and tributyrin is associated with inhibition of angiogenesis at early stages of rat liver carcinogenesis. Importantly, the combination of folic acid and tributyrin has stronger chemopreventive effect than each of the compounds alone.

Trends in research on energy balance supported by the National Cancer Institute.

Over the past decade, the body of research linking energy balance to the incidence, development, progression, and treatment of cancer has grown substantially. No prior NIH portfolio analyses have focused on energy balance within one institute. This portfolio analysis describes the growth of National Cancer Institute (NCI) grant research on energy balance-related conditions and behaviors from 2004 to 2010 following the release of an NCI research priority statement in 2003 on energy balance and cancer-related research. Energy balance grants from fiscal years (FY) 2004 to 2010 were identified using multiple search terms and analyzed between calendar years 2008 and 2010. Study characteristics related to cancer site, design, population, and energy balance area (physical activity, diet, and weight) were abstracted. From FY2004 to FY2010, the NCI awarded 269 energy balance-relevant grants totaling $518 million. In FY2010, 4.2% of NCI's total research project grants budget was allocated to energy balance research, compared to 2.1% in FY2004. The NCI more than doubled support for investigator-initiated research project grants (R01) and increased support for cooperative agreement (U01, U54) and exploratory research (R21) grants. In the portfolio, research examining energy balance areas in combination accounted for 41.6%, and observational and interventional studies were equally represented (38.3% and 37.2%, respectively). Breast cancer was the most commonly studied cancer. Inclusion of minorities rose, and funding specific to cancer survivors more than doubled. From FY2004 to FY2010, NCI's investment in energy balance and related health behavior research showed growth in funding and diversity of mechanisms, topics, and disciplines-growth that reflects new directions in this field.

Coupling global methylation and gene expression profiles reveal key pathophysiological events in liver injury induced by a methyl-deficient diet.

SCOPE: A methyl-deficient diet induces liver injury similar to human nonalcoholic steatohepatitis, one of the main risk factors for the development of hepatocellular carcinoma. Previous studies have demonstrated that this diet perturbs DNA methylation by causing a profound loss of global cytosine methylation, predominantly at heavily methylated repetitive sequences. However, whether methyl deficiency affects the methylation status of gene promoters has not been explored. METHODS AND RESULTS: Mouse gene expression and CpG island microarrays were used to characterize the gene expression and CpG island methylation profiles in the livers of C57BL/6J mice fed a methyl-deficient diet. We detected 164 genes that were differentially expressed and exhibited an inverse relationship between the gene expression and the extent of CpG island methylation. Furthermore, these genes were associated with altered lipid and glucose metabolism, DNA damage and repair, apoptosis, the development of fibrosis, and liver tissue remodeling. Although there were both increased and decreased levels of CpG island methylation, the number of hypomethylated genes was substantially greater than the number of hypermethylated genes. CONCLUSION: The results this study demonstrate that pairing methylation profiles with gene expression profiles is a powerful approach to identify dysregulated high-priority fundamental pathophysiological pathways associated with disease development.

MicroRNA, nutrition, and cancer prevention.

MicroRNA (miRNA) are small noncoding RNA molecules that are involved in post-transcriptional gene silencing. Alterations in miRNA expression are observed in and may underlie many different human diseases, including cancer. In fact, miRNA have been shown to affect the hallmarks of cancer, including sustaining proliferative signaling, evading growth suppressors, resisting cell death, enabling replicative immortality, inducing angiogenesis, and activating invasion and metastasis. Genetic and epigenetic alterations may explain aberrant miRNA expression in cancer cells and may also contribute to cancer risk. It is now thought that by circulating through the bloodstream, miRNA can exert their effects at distant sites as well as within the cells of origin. Recent evidence suggests that nutrients and other bioactive food components protect against cancer through modulation of miRNA expression. Moreover, dietary factors have been shown to modify miRNA expression and their mRNA targets in various cancer processes, including apoptosis, cell cycle regulation, differentiation, inflammation, angiogenesis, and metastasis as well as pathways in stress response. Herein, we provide a brief overview of dietary modulation of miRNA expression and its potential role in cancer prevention. Understanding the affect of dietary factors on miRNA expression and function may provide insight on prevention strategies to reduce the burden of cancer.

High dietary intake of sodium selenite does not affect gene mutation frequency in rat colon and liver.

Our previous studies have shown that selenium (Se) is protective against dimethylhydrazine (DMH)-induced preneoplastic colon cancer lesions, and protection against DNA damage has been hypothesized to be one mechanism for the anticancer effect of Se. The present study was designed to determine whether dietary selenite affects somatic mutation frequency in vivo. We used the Big Blue transgenic model to evaluate the in vivo mutation frequency of the cII gene in rats fed either a Se-deficient (0 microg Se/g diet) or Se-supplemented diet (0.2 or 2 microg Se/g diet; n = 3 rats/diet in experiment 1 and n = 5 rats/group in experiment 2) and injected with DMH (25 mg/kg body weight, i.p.). There were no significant differences in body weight between the Se-deficient and Se-supplemented (0.2 or 2 microg Se/g diet) rats, but the activities of liver glutathione peroxidase and thioredoxin reductase and concentration of liver Se were significantly lower (p < 0.0001) in Se-deficient rats compared to rats supplemented with Se. We found no effect of dietary Se on liver 8-hydroxy-2'-deoxyguanosine. Gene mutation frequency was significantly lower in liver (p < 0.001) than that of colon regardless of dietary Se. However, there were no differences in gene mutation frequency in DNA from colon mucosa or liver from rats fed the Se-deficient diet compared to those fed the Se-supplemented (0.2 or 2 microg Se/g diet) diet. Although gene mutations have been implicated in the etiology of cancer, our data suggest that decreasing gene mutation is not likely a key mechanism through which dietary selenite exerts its anticancer action against DMH-induced preneoplastic colon cancer lesions in a Big Blue transgenic rat model.

Down-regulation of the microRNAs miR-34a, miR-127, and miR-200b in rat liver during hepatocarcinogenesis induced by a methyl-deficient diet.

Altered expression of microRNAs (miRNAs) has been reported in diverse human cancers; however, the down-regulation or up-regulation of any particular miRNAs in cancer is not sufficient to address the role of these changes in carcinogenesis. In this study, using the rat model of liver carcinogenesis induced by a methyl-deficient diet, which is relevant to the hepatocarcinogenesis in humans associated with viral hepatitis C and B infections, alcohol exposure and metabolic liver diseases, we showed that the development of hepatocellular carcinoma (HCC) is characterized by prominent early changes in expression of miRNA genes, specifically by inhibition of expression of microRNAs miR-34a, miR-127, miR-200b, and miR-16a involved in the regulation of apoptosis, cell proliferation, cell-to-cell connection, and epithelial-mesenchymal transition. The mechanistic link between these alterations in miRNAs expression and the development of HCC was confirmed by the corresponding changes in the levels of E2F3, NOTCH1, BCL6, ZFHX1B, and BCL2 proteins targeted by these miRNAs. The significance of miRNAs expression dysregulation in respect to hepatocarcinogenesis was confirmed by the persistence of these miRNAs alterations in the livers of methyl-deficient rats re-fed a methyl-adequate diet. Altogether, the early occurrence of alterations in miRNAs expression and their persistence during the entire process of hepatocarcinogenesis indicate that the dysregulation of microRNAs expression may be an important contributing factor in the development of HCC.

Epigenetic downregulation of the suppressor of cytokine signaling 1 (Socs1) gene is associated with the STAT3 activation and development of hepatocellular carcinoma induced by methyl-deficiency in rats.

The members of the platelet-derived growth factor (PDGF) and the transforming growth factor-beta (TGFbeta) pathways are important in the induction of liver fibrosis and cirrhosis; however, their role in the subsequent progression to hepatocellular carcinoma (HCC) remains elusive. Our study provides new insights into mechanisms of dysregulation of PDGFs, TGFbeta and signal transducer and activator of transcription (STAT) pathways in the pathogenesis of methyl-deficient rodent liver carcinogenesis, a remarkably relevant model to the development of HCC in humans. We demonstrated a progressive increase in the Pdgfs and TGFbeta expression in preneoplastic tissue and liver tumors indicating their promotional role in carcinogenesis, particularly in progression of liver fibrosis and cirrhosis. However, activation of the STAT3 occurred only in fully developed HCC and was associated with downregulation of the Socs1 gene. The inhibition of the Socs1 expression in HCC was associated with an increase in histone H3 lysine 9, H3 lysine 27, and H4 lysine 20 trimethylation at the Socs1 promoter, but not with promoter methylation. The results of our study suggest the following model of events in hepatocarcinogenesis: during early stages, overexpression of the Socs1 effectively inhibits TGFbeta- and PDGF-induced STAT3 activation, whereas, during the advanced stages of hepatocarcinogenesis, the Socs1 downregulation resulted in loss of its ability to attenuate the signal from the upregulated TGFbeta and PDGFs leading to oncogenic STAT3 activation and malignant cell transformation. This model illustrates that the Socs1 acts as classic tumor suppressor by preventing activation of the STAT3 and downregulation of Socs1 and consequent activation of STAT3 may be a crucial events leading to formation of HCC.

Evidence for dietary regulation of microRNA expression in cancer cells.

MicroRNAs (miRNAs) are an abundant class of short noncoding RNAs that are widely expressed in mammalian cells and are important in post-translational gene regulation, including regulation of cell proliferation, apoptosis, and differentiation processes. miRNAs are involved in cancer initiation and progression and their expression patterns serve as phenotypic signatures of different cancers. Recent evidence suggests that dietary components as diverse as folate, retinoids, and curcumin exert cancer-protective effects through modulation of miRNA expression. miRNAs may be useful as biomarkers of cancer prevention or nutritional status, as well as serve as potential molecular targets that are influenced by dietary interventions.