An overview of epigenetics and chemoprevention

Lessons learned from the discovery and development of the sesquiterpene lactones in cancer therapy and prevention

INTRODUCTION

Sesquiterpene lactones (SLs) are one of the most diverse bioactive secondary metabolites found in plants and exhibit a broad range of therapeutic properties . SLs have been showing promising potential in cancer clinical trials, and the molecular mechanisms underlying their anticancer potential are being uncovered. Recent evidence also points to a potential utility of SLs in cancer prevention.

AREAS COVERED

This work evaluates SLs with promising anticancer potential based on cell, animal, and clinical models: Artemisinin, micheliolide, thapsigargin dehydrocostuslactone, arglabin, parthenolide, costunolide, deoxyelephantopin, alantolactone, isoalantolactone, atractylenolide 1, and xanthatin as well as their synthetic derivatives. We highlight actionable molecular targets and biological mechanisms underlying the anticancer therapeutic properties of SLs. This is complemented by a unique assessment of SL mechanisms of action that can be exploited in cancer prevention. We also provide insights into structure-activity and pharmacokinetic properties of SLs and their potential use in combination therapies.

EXPERT OPINION

We extract seven major lessons learned and present evidence-based solutions that can circumvent some scientific limitations or logistic impediments in SL anticancer research. SLs continue to be at the forefront of cancer drug discovery and are worth a joint interdisciplinary effort in order to leverage their potential in cancer therapy and prevention.

Black raspberries attenuate colonic adenoma development in Apc Min mice: Relationship to hypomethylation of promoters and gene bodies

Recent studies have suggested that in addition to promoter region, DNA methylation in intragenic and intergenic regions also changes during physiological processes and disease. The current study showed that feeding of black raspberries (BRBs) to Apc^Min mice suppressed colon and intestinal tumors. MBDCap-seq suggested that dietary BRBs hypomethylated promoter, intragenic, and intergenic regions. Annotation of those regions highlighted genes in pathways involved in immune regulation, inflammatory signaling, production of nitric oxide and reactive oxygen species, and progression of colorectal cancer. BRB phytochemicals (e.g., ellagic acid, anthocyanins, oligosaccharides) and their gut bacterial metabolites (e.g., urolithin, protocatechuic acid, short-chain fatty acids) inhibited DNMT1 and DNMT3B activities in a cell-free assay. Our results suggest that BRBs’ hypomethylating activities result from the combined effects of multiple BRB phytochemicals and their gut bacterial metabolites. Because similar substances are found in many plant products, our results with BRBs might also apply to commonly consumed fruits and vegetables.

Targeting Breast Cancer Cells with G4 PAMAM Dendrimers and Valproic Acid Derivative Complexes

BACKGROUND

Our research group has developed some Valproic Acid (VPA) derivatives employed as anti-proliferative compounds targeting the HDAC8 enzyme. However, some of these compounds are poorly soluble in water.

OBJECTIVE

Employed the four generations of Polyamidoamine (G4 PAMAM) dendrimers as drug carriers of these compounds to increase their water solubility for further in vitro evaluation.

METHODS

VPA derivatives were subjected to Docking and Molecular Dynamics (MD) simulations to evaluate their affinity on G4 PAMAM. Then, HPLC-UV/VIS, 1H NMR, MALDI-TOF and atomic force microscopy were employed to establish the formation of the drug-G4 PAMAM complexes.

RESULTS

The docking results showed that the amide groups of VPA derivatives make polar interactions with G4 PAMAM, whereas MD simulations corroborated the stability of the complexes. HPLC UV/VIS experiments showed an increase in the drug water solubility which was found to be directly proportional to the amount of G4 PAMAM. 1H NMR showed a disappearance of the proton amine group signals, correlating with docking results. MALDI-TOF and atomic force microscopy suggested the drug-G4 PAMAM dendrimer complexes formation.

DISCUSSION

In vitro studies showed that G4 PAMAM has toxicity in the micromolar concentration in MDAMB- 231, MCF7, and 3T3-L1 cell lines. VPA CF-G4 PAMAM dendrimer complex showed anti-proliferative properties in the micromolar concentration in MCF-7 and 3T3-L1, and in the milimolar concentration in MDAMB- 231, whereas VPA MF-G4 PAMAM dendrimer complex didn't show effects on the three cell lines employed.

CONCLUSION

These results demonstrate that G4 PAMAM dendrimers are capableof transporting poorly watersoluble aryl-VPA derivate compounds to increase its cytotoxic activity against neoplastic cell lines.

Identification of Caffeic Acid Phenethyl Ester (CAPE) as a Potent Neurodifferentiating Natural Compound That Improves Cognitive and Physiological Functions in Animal Models of Neurodegenerative Diseases

Cell-based screening of bioactive compounds has served as an important gateway in drug discovery. In the present report, using human neuroblastoma cells and enrolling an extensive three-step screening of 57 phytochemicals, we have identified caffeic acid phenethyl ester (CAPE) as a potent neurodifferentiating natural compound. Analyses of control and CAPE-induced neurodifferentiated cells revealed: (i) modulation of several key proteins (NF200, MAP-2, NeuN, PSD95, Tuj1, GAP43, and GFAP) involved in neurodifferentiation process; and (ii) attenuation of neuronal stemness (HOXD13, WNT3, and Msh-2) and proliferation-promoting (CDC-20, CDK-7, and BubR1) proteins. We anticipated that the neurodifferentiation potential of CAPE may be beneficial for the treatment of neurodegenerative diseases and tested it using the Drosophila model of Alzheimer’s disease (AD) and mice model of amnesia/loss of memory. In both models, CAPE exhibited improved disease symptoms and activation of physiological functions. Remarkably, CAPE-treated mice showed increased levels of neurotrophin-BDNF, neural progenitor marker-Nestin, and differentiation marker-NeuN, both in the cerebral cortex and hippocampus. Taken together, we demonstrate the differentiation-inducing and therapeutic potential of CAPE for neurodegenerative diseases.

Dynamic-shared Pharmacophore Approach as Tool to Design New Allosteric PRC2 Inhibitors, Targeting EED Binding Pocket

The Polycomb Repressive complex 2 (PRC2) maintains a repressive chromatin state and silences many genes, acting as methylase on histone tails. This enzyme was found overexpressed in many types of cancer. In this work, we have set up a Computer-Aided Drug Design approach based on the allosteric modulation of PRC2. In order to minimize the possible bias derived from using a single set of coordinates within the protein-ligand complex, a dynamic workflow was developed. In details, molecular dynamic was used as tool to identify the most significant ligand-protein interactions from several crystallized protein structures. The identified features were used for the creation of dynamic pharmacophore models and docking grid constraints for the design of new PRC2 allosteric modulators. Our protocol was retrospectively validated using a dataset of active and inactive compounds, and the results were compared to the classic approaches, through ROC curves and enrichment factor. Our approach suggested some important interaction features to be adopted for virtual screening performance improvement.

Polyunsaturated fatty acids and DNA methylation in colorectal cancer

Colorectal cancer (CRC) has been designated a major global problem, especially due to its high prevalence in developed countries. CRC mostly occurs sporadically (75%-80%), and only 20%-25% of patients have a family history. Several processes are involved in the development of CRC such as a combination of genetic and epigenetic alterations. Epigenetic changes, including DNA methylation play a vital role in the progression of CRC. Complex interactions between susceptibility genes and environmental factors, such as a diet and sedentary lifestyle, lead to the development of CRC. Clinical and experimental studies have confirmed the beneficial effects of dietary polyunsaturated fatty acids (PUFAs) in preventing CRC. From a mechanistic viewpoint, it has been suggested that PUFAs are pleiotropic agents that alter chromatin remodeling, membrane structure and downstream cell signaling. Moreover, PUFAs can alter the epigenome via modulation of DNA methylation. In this review, we summarize recent investigations linking PUFAs and DNA methylation-associated CRC risk.

CDH1, DLEC1 and SFRP5 methylation panel as a prognostic marker for advanced epithelial ovarian cancer

AIM

To investigate the CDH1, DLEC1 and SFRP5 gene methylation panel for advanced epithelial ovarian carcinoma (EOC).

MATERIALS & METHODS

One hundred and seventy-seven advanced EOC specimens were evaluated by methylation-specific PCR. We also used The Cancer Genome Atlas dataset to evaluate the panel.

RESULTS

The presence of two or more methylated genes was significant in recurrence (hazard ratio [HR]: 1.91 [1.33-2.76]; p = 0.002) and death (HR: 1.96 [1.26-3.06]; p = 0.006) in our cohort. In The Cancer Genome Atlas dataset, the presence of two or three methylated genes was significant in death (HR: 1.59 [1.15-2.18]; p = 0.0047) and close to the significance level in recurrence (HR: 1.37 [0.99-1.88]; p = 0.058).

CONCLUSION

The CDH1, DLEC1 and SFRP5 methylation panel is a potential prognostic biomarker for advanced EOC.

Modulation of estrogen synthesis and metabolism by phytoestrogens in vitro and the implications for women's health

Phytoestrogens are increasingly used as dietary supplements due to their suggested health promoting properties, but also by women for breast enhancement and relief of menopausal symptoms. Generally, phytoestrogens are considered to exert estrogenic activity via estrogen receptors (ERs), but they may also affect estrogen synthesis and metabolism locally in breast, endometrial and ovarian tissues. Considering that accurate regulation of local hormone levels is crucial for normal physiology, it is not surprising that interference with hormonal synthesis and metabolism is associated with a wide variety of women's health problems, varying from altered menstrual cycle to hormone-dependent cancers. Yet, studies on phytoestrogens have mainly focused on ER-mediated effects of soy-derived phytoestrogens, with less attention paid to steroid synthesis and metabolism or other phytoestrogens. This review aims to evaluate the potential of phytoestrogens to modulate local estrogen levels and the implications for women's health. For that, an overview is provided of the effects of commonly used phytoestrogens, i.e. 8-prenylnaringenin, biochanin A, daidzein, genistein, naringenin, resveratrol and quercetin, on estrogen synthesizing and metabolizing enzymes in vitro. The potential implications for women's health are assessed by comparing the in vitro effect concentrations with blood concentrations that can be found after intake of these phytoestrogens. Based on this evaluation, it can be concluded that high-dose supplements with phytoestrogens might affect breast and endometrial health or fertility in women via the modulation of steroid hormone levels. However, more data regarding the tissue levels of phytoestrogens and effect data from dedicated, tissue-specific assays are needed for a better understanding of potential risks. At least until more certainty regarding the safety has been established, especially young women would better avoid using supplements containing high doses of phytoestrogens.

Phytochemistry and Pharmacology of Phyllanthus niruri L.: A Review

Phyllanthus niruri, a typical member of family Euphorbiaceae, is a small annual herb found throughout the tropical and subtropical regions of both hemispheres. The genus Phyllanthus has been used in traditional medicine for its wide range of pharmacological activities like antimicrobial, antioxidant, anticancer, antiinflammatory, antiplasmodial, antiviral, diuretic and hepatoprotective. This review summarizes the information about morphological, biochemical, ethanobotanical, pharmacological, biological and toxicological activities with special emphasis on mechanism of anticancer activity of P. niruri. Gaps in previous studies such as taxonomic inconsistency of P. niruri, novel phytochemicals and their therapeutic properties, especially mechanisms of anticancerous activity and market products available, have been looked into and addressed. Scientific information related to 83 phytochemicals (including many novel compounds detected recently by the authors) has been provided in a very comprehensive manner. Copyright © 2017 John Wiley & Sons, Ltd.

Spotlight on decitabine for myelodysplastic syndromes in Chinese patients

Myelodysplastic syndromes (MDSs) are a group of heterogeneous clonal hematopoietic stem cell malignancies with advanced median age. The silencing of tumor suppressor genes caused by DNA hypermethylation plays a crucial role in the pathogenesis of MDS. Decitabine, the available hypomethylating agent, is successfully used for the treatment and improves the outcome of MDS, and has become one of the most frequently administered disease-modifying therapies. With an aging population and a growing number of people exposed to benzene, the incidence of MDS has been increasing rapidly. The blinded regimen choice and the lack of a unified strategy create challenges for the treatment of MDS. Here, we present a review of clinical progress and prospects of decitabine treatment of MDS in the People’s Republic of China. We also discuss the optimization of therapy issues to improve the cure rate and prolong survival in patients with MDS.

Epigenetic therapy for colorectal cancer

Aberrations in epigenome that include alterations in DNA methylation, histone acetylation, and miRNA (microRNA) expression may govern the progression of colorectal cancer (CRC). These epigenetic changes affect every phase of tumor development from initiation to metastasis. Since epigenetic alterations can be reversed by DNA demethylating and histone acetylating agents, current status of the implication of epigenetic therapy in CRC is discussed in this article. Interestingly, DNA methyltransferase inhibitors (DNMTi) and histone deacetylase inhibitors (HDACi) have shown promising results in controlling cancer progression. The information provided here might be useful in developing personalized medicine approaches.

Cancer cell-specific oligopeptides selected by an integrated microfluidic system from a phage display library for ovarian cancer diagnosis

Ovarian cancer is one of the leading causes of female mortality worldwide. Unfortunately, there are currently few high-specificity candidate oligopeptide targeting agents that can be used for early diagnosis of this cancer. It has been suggested that cancer-specific oligopeptides could be screened from a phage display library. However, conventional methods are tedious, labor-intensive, and time consuming. Therefore, a novel, integrated microfluidic system was developed to automate the entire screening process for ovarian cancer cell-specific oligopeptides. An oligopeptide screened with microfluidic chip-based technique was demonstrated to have high affinity to ovarian cancer cells and demonstrated relatively low binding to other cancer cells, indicating a high specificity. Furthermore, the developed method consumed relatively low volumes of samples and reagents; only 70 μL of reactant was used within the whole experimental process. Each panning process was also significantly shortened to only 7.5 hours. Therefore, the screened oligopeptide could be used to isolate ovarian cancer cells in a rapid manner, thus greatly expediting the diagnosis and its application as oligopeptide targeting agent for theranostics of this cancer.

Gene methylation profiles as prognostic markers in ovarian clear cell and endometrioid adenocarcinomas

Ovarian cancer is a cancer of high mortality. Aberrant gene methylation of tumor suppressor genes has been shown to be related to the development of malignancy. This study aimed to investigate the methylation of various genes in ovarian clear cell adenocarcinoma (OCCA) and ovarian endometrioid adenocarcinoma (OEA) and evaluate methylation biomarkers in terms of patient chemo-response and outcome. Eight candidate genes from 66 OCCA and 51 OEA patients were evaluated by methylation-specific polymerase chain reaction and capillary electrophoresis. Clinico-pathological parameters and patient outcomes were analyzed. The frequencies of gene methylation in RASSF1A (79% vs. 59%, p=0.025), E-cadherin (30% vs. 10%, p=0.011), and DLEC1 (71% vs. 43%, p=0.003) were higher in the patients with OCCA than in those with OEA. The chemo-resistant group had a significantly higher percentage of E-cadherin methylation (36.7% vs. 16.1%, p=0.036) than the chemo-sensitive group. In multivariate analysis (log-rank test), advanced stage (4.79 [2.10-10.94], p<0.001) was the only risk factor for mortality. Those with methylation of more than two out of three genes (E-cadherin, DLEC1, and SFRP5) had a shorter disease-free survival (1.89 [1.07-3.32], p=0.028) and overall survival (3.29 [1.57-6.87], p=0.002) than those with methylation of one or no gene. In advanced-stage malignancies, those with more than two out of the three gene methylations also had a shorter overall survival (3.86 [1.63-9.09], p=0.002) than those with methylation of only one or no gene. Patients with OCCA have different patterns of gene methylation than those with OEA. Methylation of the E-cadherin, DLEC1 and SFRP5 genes can be a prognostic biomarker for OCCA and OEA.

Comparison between decitabine and azacitidine for the treatment of myelodysplastic syndrome: a meta-analysis with 1,392 participants

The hypomethylating agents decitabine and azacitidine have been found to improve the outcome of patients with myelodysplastic syndrome (MDS); however, the clinical choice between them is controversial. Therefore, this meta-analysis was performed to compare the efficacy, toxicity, and survival advantage of decitabine and azacitidine in patients with MDS. Eleven trials with a total of 1392 patients with MDS (decitabine, n = 768; azacitidine, n = 624) were included for analysis. The pooled estimates of partial response, hematologic improvement, and overall response rates for azacitidine were significantly higher than for decitabine. There were no differences between these 2 drugs regarding complete response, red blood cell transfusion-independent rates, and grade 3 or 4 hematologic toxicity. When compared with best supportive care, azacitidine significantly improved overall survival (hazard ratio [HR], 0.69; 95% CI, 0.54-0.87) and time to acute myeloid leukemia transformation (HR, 0.51; 95% CI, 0.35-0.74). But these benefits were not found with decitabine. Among patients with higher risk (International Prognostic Scoring System value of 3) or older than 75 years, treatment with azacitidine was a favorable factor, whereas decitabine showed no advantage. Therefore, with higher overall response rates and better survival benefits, azacitidine is recommended as the first-line hypomethylating agent for MDS, especially in elderly patients or those with high risk.

Epigenetic reprogramming of human lung cancer cells with the extract of bovine parthenogenetic oocytes

The tumour suppressor gene silencing and proto-oncogene activation caused by epigenetic alterations plays an important role in the initiation and progression of cancer. Re-establishing the balance between the expression of tumour suppressor genes and proto-oncogenes by epigenetic modulation is a promising strategy for cancer treatment. In this study, we investigated whether cancer cells can be epigenetically reprogrammed by oocyte extract. H460 human lung cancer cells were reversibly permeabilized and incubated with the extract of bovine parthenogenetic oocytes. Bisulphite sequencing showed that bovine parthenogenetic oocyte extract induced significant demethylation at the promoters of the tumour suppressor genes RUNX3 and CDH1, but not at the promoter of the oncogenic pluripotency gene SOX2. Chromatin immunoprecipitation showed that the histone modifications at RUNX3 and CDH1 promoters were modulated towards a transcriptionally activating state, while those at SOX2 promoter towards a transcriptionally repressive state. Correspondingly, bovine parthenogenetic oocyte extract reversed the epigenetic silencing of RUNX3 and CDH1, and repressed the expression of SOX2. At the functional level, proliferation, anchorage-independent growth, migration and invasion of H460 cells was strongly inhibited. These results indicate that bovine parthenogenetic oocyte extract changes the expression patterns of tumour suppressor and oncogenic genes in cancer cells by remodelling the epigenetic modifications at their promoters. Bovine parthenogenetic oocyte extract may provide a useful tool for epigenetically reprogramming cancer cells and for dissecting the epigenetic mechanisms involved in tumorigenesis.

DNA methyltransferases: a novel target for prevention and therapy

Cancer is the second leading cause of death in US. Despite the emergence of new, targeted agents, and the use of various therapeutic combinations, none of the available treatment options are curative in patients with advanced cancer. Epigenetic alterations are increasingly recognized as valuable targets for the development of cancer therapies. DNA methylation at the 5-position of cytosine, catalyzed by DNA methyltransferases (DNMTs), is the predominant epigenetic modification in mammals. DNMT1, the major enzyme responsible for maintenance of the DNA methylation pattern is located at the replication fork and methylates newly biosynthesized DNA. DNMT2 or TRDMT1, the smallest mammalian DNMT is believed to participate in the recognition of DNA damage, DNA recombination, and mutation repair. It is composed solely of the C-terminal domain, and does not possess the regulatory N-terminal region. The levels of DNMTs, especially those of DNMT3B, DNMT3A, and DNMT3L, are often increased in various cancer tissues and cell lines, which may partially account for the hypermethylation of promoter CpG-rich regions of tumor suppressor genes in a variety of malignancies. Moreover, it has been shown to function in self-renewal and maintenance of colon cancer stem cells and need to be studied in several cancers. Inhibition of DNMTs has demonstrated reduction in tumor formation in part through the increased expression of tumor suppressor genes. Hence, DNMTs can potentially be used as anti-cancer targets. Dietary phytochemicals also inhibit DNMTs and cancer stem cells; this represents a promising approach for the prevention and treatment of many cancers.

Black raspberries protectively regulate methylation of Wnt pathway genes in precancerous colon tissue

Ulcerative colitis is frequently an intermediate step to colon cancer. The interleukin-10 knockout mouse is a genetic model of this progression. We report that knockout mice fed 5% black raspberries (BRB) had significantly less colonic ulceration as compared with knockout mice that consumed the control diet. Dysfunction of the Wnt signaling pathway is a key event in ulcerative colitis-associated colon carcinogenesis. Therefore, we investigated the effects of BRBs on the Wnt pathway and found that the BRB-fed knockout mice exhibited a significantly lower level of β-catenin nuclear translocation. We followed-up this observation by evaluating the effect of BRBs on selected Wnt pathway antagonists. The mRNA expression levels of wif1, sox17, and qki were diminished in the knockout mice, whereas they were expressed at normal levels in knockout mice that were fed BRBs. The lower mRNA expression of these genes in the colon from the knockout mice correlated with hypermethylation of their promoter regions; BRBs decreased their promoter methylation and increased mRNA expression of these genes. This hypomethylation was associated with elevated protein expression of key proteins/enzymes that augment methylation, for example, dnmt3b, hdac1, hdac2, and mbd2 in the knockout mice; in addition, BRBs decreased the protein expression of these proteins/enzymes. The knockout mouse model recapitulates what occurs in human ulcerative colitis. Promoter methylation of CDH1 and SFRP1 was significantly higher in human ulcerative colitis tissues compared with their adjacent normal tissues. In conclusion, our results suggest that BRBs inhibit colonic ulceration and, ultimately, colon cancer partly through inhibiting aberrant epigenetic events that dysregulate Wnt signaling.

Trends in incidence and survival outcome of epithelial ovarian cancer: 30-year national population-based registry in Taiwan

Objective

To investigate the changes of incidence and prognosis of epithelial ovarian cancer in thirty years in Taiwan.

Methods

The databases of women with epithelial ovarian cancer during the period from 1979 to 2008 were retrieved from the National Cancer Registration System of Taiwan. The incidence and prognosis of these patients were analyzed.

Results

Totally 9,491 patients were included in the study. The age-adjusted incidences of epithelial ovarian cancer were 1.01, 1.37, 2.37, 3.24, 4.18, and 6.33 per 100,000 person-years, respectively, in every 5-year period from 1979 to 2008. The age-specific incidence rates increased especially in serous, endometrioid and clear cell carcinoma, and the age of diagnosis decreased from sixty to fifty years old in the three decades. Patients with mucinous, endometrioid, or clear cell carcinoma had better long-term survival than patients with serous carcinoma (log rank test, p<0.001). Patients with undifferentiated carcinoma or carcinosarcoma had poorer survival than those with serous carcinoma (log rank test, p<0.001). The mortality risk of age at diagnosis of 30-39 was significantly higher than that of age of 70 years or more (test for trend, p<0.001). The mortality risk decreased from the period of 1996-1999 (hazard ratio [HR], 0.90; p=0.054) to the period after 2000 (HR, 0.74; p<0.001) as compared with that from the period of 1991-1995.

Conclusion

An increasing incidence and decreasing age of diagnosis in epithelial ovarian cancer patients were noted. Histological type, age of diagnosis, and treatment period were important prognostic factors for epithelial ovarian carcinoma.

Remodeling epigenetic modifications at tumor suppressor gene promoters with bovine oocyte extract

BACKGROUND AIMS

Epigenetic silencing of tumor suppressor genes by aberrant DNA methylation and histone modifications at their promoter regions plays an important role in the initiation and progression of cancer. The therapeutic effect of the widely used epigenetic drugs, including DNA methyltransferase inhibitors and histone deacetylase inhibitors, remains unsatisfactory. One important underlying factor in the ineffectiveness of these drugs is that their actions lack specificity.

METHODS

To investigate whether oocyte extract can be used for epigenetic re-programming of cancer cells, H460 human lung cancer cells were reversibly permeabilized and incubated with bovine oocyte extract.

RESULTS

Bisulfite sequencing showed that bovine oocyte extract induced significant demethylation at hypermethylated promoter CpG islands of the tumor suppressor genes RUNX3 and CDH1; however, the DNA methylation levels of repetitive sequences were not affected. Chromatin immunoprecipitation showed that bovine oocyte extract significantly reduced transcriptionally repressive histone modifications and increased transcriptionally activating histone modifications at the promoter regions of RUNX3 and CDH1. Bovine oocyte extract reactivated the expression of RUNX3 and CDH1 at both the messenger RNA and the protein levels without up-regulating the transcription of pluripotency-associated genes. At the functional level, anchorage-independent proliferation, migration and invasion of H460 cells was strongly inhibited.

CONCLUSIONS

These results demonstrate that bovine oocyte extract reactivates epigenetically silenced tumor suppressor genes by remodeling the epigenetic modifications at their promoter regions. Bovine oocyte extract may provide a useful tool for investigating epigenetic mechanisms in cancer and a valuable source for developing novel safe therapeutic approaches that target epigenetic alterations.

Specific reversal of tumor-suppressor gene promoter hypermethylation with bovine oocyte extract

Epigenetic silencing of tumor-suppressor genes by promoter hypermethylation contributes considerably to the initiation and progression of cancer. Nucleoside analogs, the most widely used DNA methylation inhibitors, have the drawbacks of inducing repetitive sequence hypomethylation. Here, we aimed to specifically reverse tumor-suppressor gene (TSG) promoter hypermethylation with bovine oocyte extract. H460 human lung cancer cells were reversibly permeabilized and incubated with bovine oocyte extract for 3.5 h. The extract treatment led to significant demethylation of the hypermethylated promoters of the TSGs RUNX3, CDH1, RASSF1A and WIF1; however, the methylation levels of repetitive sequences were not affected. The promoter demethylation induced by bovine oocyte extract substantially upregulated the expression of RUNX3, CDH1, RASSF1A and WIF1, and significantly inhibited the anchorage-independent proliferation, migration and invasion of H460 cells. This study demonstrates that bovine oocyte extract can reverse the malignant phenotype by serving as an efficient and safe DNA demethylator. The active demethylation activity of bovine oocyte extract is valuable for dissecting the epigenetic alterations in cancer cells and developing novel safe anticancer drugs based on epigenetic mechanisms.

Phenethyl isothiocyanate inhibits androgen receptor-regulated transcriptional activity in prostate cancer cells through suppressing PCAF

SCOPE

Androgen receptor (AR) signaling is critical for all aspects of prostate growth and tumorigenesis. The glucosinolate-derived phenethyl isothiocyanate (PEITC) has recently been demonstrated to reduce the risk of prostate cancer (PCa) and inhibit PCa cell growth. We previously reported that p300/CBP-associated factor (PCAF), a co-regulator for AR, is upregulated in PCa cells through suppression of the mir-17 gene. Here, we assessed the effects of PEITC on PCAF expression and AR-regulated transcriptional activity in PCa cells.

METHODS AND RESULTS

Using AR-responsive LNCaP cells, we observed the inhibitory effects of PEITC on the dihydrotestosterone-stimulated AR transcriptional activity and cell growth of PCa cells. Interestingly, overexpression of PCAF attenuated the inhibitory effects of PEITC on dihydrotestosterone-stimulated AR transcriptional activity. Expression of PCAF was upregulated in PCa cells through suppression of miR-17. PEITC treatment significantly decreased PCAF expression and promoted transcription of miR-17 in LNCaP cells. Functional inhibition of miR-17 attenuated the suppression of PCAF in cells treated by PEITC.

CONCLUSION

Our results indicate that PEITC inhibits AR-regulated transcriptional activity and cell growth of PCa cells through miR-17-mediated suppression of PCAF, suggesting a new mechanism by which PEITC modulates PCa cell growth.

From natural products to drugs for epimutation computer-aided drug design

The epimutational event, i.e., ectopic methylation in tumor suppressor genes, can lead to gene silencing, thus promoting prognosis of cancer. The progression of DNA methylation is a cycle of demethylation, de novo methylation, and maintenance methylation. The enzyme responsible for maintenance of methylation status is DNA methyltransferase 1 (DNMT1), the continuous activity of which is required to maintain the pattern of epimutation; thus, its inhibition is a promising strategy for the treatment of cancer. To the best of our knowledge, this study is the first to focus on the recently developed crystal structure of the catalytic site of DNMT1. Here in this study, we have used the crystal structure for the development of non-nucleoside DNMT1 inhibitors using virtual screening (VS), absorption, distribution, metabolism, elimination/toxicology analysis, and molecular docking studies. In this study, VS was carried out on 48,531 natural products to create a subset of lead-like natural products. Three of them were found to form hydrogen bonds with the catalytic site of the DNMT1 (Cys 1226). Thus, this study adumbrates potential lead compounds for treatment of epimutation.

Environmental toxicants, epigenetics, and cancer

Tumorigenesis, a complex and multifactorial progressive process of transformation of normal cells into malignant cells, is characterized by the accumulation of multiple cancer-specific heritable phenotypes triggered by the mutational and/or non-mutational (i.e., epigenetic) events. Accumulating evidence suggests that environmental and occupational exposures to natural substances, as well as man-made chemical and physical agents, play a causative role in human cancer. In a broad sense, carcinogenesis may be induced through either genotoxic or non-genotoxic mechanisms; however, both genotoxic and non-genotoxic carcinogens also cause prominent epigenetic changes. This review presents current evidence of the epigenetic alterations induced by various chemical carcinogens, including arsenic, 1,3-butadine, and pharmaceutical and biological agents, and highlights the potential for epigenetic changes to serve as markers for carcinogen exposure and cancer risk assessment.

Black raspberry-derived anthocyanins demethylate tumor suppressor genes through the inhibition of DNMT1 and DNMT3B in colon cancer cells

We previously reported that oral administration of black raspberry powder decreased promoter methylation of tumor suppressor genes in tumors from patients with colorectal cancer. The anthocyanins (ACs) in black raspberries are responsible, at least in part, for their cancer-inhibitory effects. In the present study, we asked if ACs are responsible for the demethylation effects observed in colorectal cancers. Three days of treatment of ACs at 0.5, 5, and 25 μg/ml suppressed activity and protein expression of DNMT1 and DNMT3B in HCT116, Caco2 and SW480 cells. Promoters of CDKN2A, and SFRP2, SFRP5, and WIF1, upstream of Wnt pathway, were demethylated by ACs. mRNA expression of some of these genes was increased. mRNA expression of β-catenin and c-Myc, downstream of Wnt pathway, and cell proliferation were decreased; apoptosis was increased. ACs were taken up into HCT116 cells and were differentially localized with DNMT1 and DNMT3B in the same cells visualized using confocal laser scanning microscopy. Although it was reported that DNMT3B is regulated by c-Myc in mouse lymphoma, DNMT3B did not bind with c-Myc in HCT116 cells. In conclusion, our results suggest that ACs are responsible, at least in part, for the demethylation effects of whole black raspberries in colorectal cancers.

Epigenetic mechanisms of pulmonary hypertension

Epigenetics refers to changes in phenotype and gene expression that occur without alterations in DNA sequence. Epigenetic modifications of the genome can be acquired de novo and are potentially heritable. This review focuses on the emerging recognition of a role for epigenetics in the development of pulmonary arterial hypertension (PAH). Lessons learned from the epigenetics in cancer and neurodevelopmental diseases, such as Prader-Willi syndrome, can be applied to PAH. These syndromes suggest that there is substantial genetic and epigenetic cross-talk such that a single phenotype can result from a genetic cause, an epigenetic cause, or a combined abnormality. There are three major mechanisms of epigenetic regulation, including methylation of CpG islands, mediated by DNA methyltransferases, modification of histone proteins, and microRNAs. There is substantial interaction between these epigenetic mechanisms. Recently, it was discovered that there may be an epigenetic component to PAH. In PAH there is downregulation of superoxide dismutase 2 (SOD2) and normoxic activation of hypoxia inducible factor (HIF-1α). This decrease in SOD2 results from methylation of CpG islands in SOD2 by lung DNA methyltransferases. The partial silencing of SOD2 alters redox signaling, activates HIF-1α) and leads to excessive cell proliferation. The same hyperproliferative epigenetic abnormality occurs in cancer. These epigenetic abnormalities can be therapeutically reversed. Epigenetic mechanisms may mediate gene-environment interactions in PAH and explain the great variability in susceptibility to stimuli such as anorexigens, virus, and shunts. Epigenetics may be relevant to the female predisposition to PAH and the incomplete penetrance of BMPR2 mutations in familial PAH.

Targeted cancer therapy: giving histone deacetylase inhibitors all they need to succeed

Histone deacetylase inhibitors (HDACis) have now emerged as a powerful new class of small-molecule therapeutics acting through the regulation of the acetylation states of histone proteins (a form of epigenetic modulation) and other non-histone protein targets. Over 490 clinical trials have been initiated in the last 10 years, culminating in the approval of two structurally distinct HDACis - SAHA (vorinostat, Zolinza™) and FK228 (romidepsin, Istodax™). However, the current HDACis have serious limitations, including ineffectively low concentrations in solid tumors and cardiac toxicity, which is hindering their progress in the clinic. Herein, we review the primary paradigms being pursued to overcome these hindrances, including HDAC isoform selectivity, localized administration, and targeting cap groups to achieve selective tissue and cell type distribution.

Sesquiterpene lactones isolated from indigenous Middle Eastern plants inhibit tumor promoter-induced transformation of JB6 cells

Background

Sesquiterpene lactones (SL) are plant secondary metabolites that are known for their anti-fungal, anti-bacterial, anti-inflammatory, and anti-tumor properties. Considering that several SL-derived drugs are currently in cancer clinical trials, we have tested two SL molecules, 3-β-methoxy-iso-seco-tanapartholide (β-tan) isolated from Achillea falcata and salograviolide A (Sal A) isolated from Centaurea ainetensis, for their anti-tumor properties. We used the mouse epidermal JB6P + cells as a model for tumor promotion and cellular transformation. Key players that are involved in cellular transformation and tumorigenesis are the AP-1 and NF-κB transcription factors; therefore, we assessed how β-tan and Sal A modulate their signaling pathways in JB6P + cells.

Methods

The effects of β-tan and Sal A on the growth of normal and neoplastic keratinocytes and on the tumor promotion-responsive JB6P + cells were determined using the MTT assay. Anchorage-independent cell growth transformation assays were used to evaluate the anti-tumor promoting properties of these SL molecules in JB6P + cells and dual luciferase reporter assays and western blot analysis were used to investigate their effects on tumor promoter-induced AP-1 and NF-κB activities and protein levels of key AP-1 and NF-кB target genes.

Results

β-tan and Sal A selectively inhibited tumor promoter-induced cell growth and transformation of JB6P + cells at concentrations that do not affect JB6P + and primary keratinocytes basal cell growth. In addition, both molecules reduced basal and tumor promoter-induced NF-κB transcriptional activities, differentially regulated basal and tumor promoter-induced AP-1 transcriptional activities, and modulated key players of the AP-1 and NF-κB signaling pathways.

Conclusions

These results highlight the anti-tumor promoting properties of β-tan and Sal A. These SL molecules isolated from two plant species native to the Middle East may provide opportunities for complementary medicine practices.

Inflammation, DNA methylation and colitis-associated cancer

Inflammation can result from a range of sources including microbial infections, exposure to allergens and toxic chemicals, autoimmune disease and obesity. A well-balanced immune response can be anti-tumorigenic; however, a sustained or chronic inflammatory response is generally harmful as the immune response becomes distorted. A causal link between chronic inflammation and cancer is now well accepted and many chronically inflamed organs of the gastrointestinal tract show this association. For example, patients with inflammatory bowel disease (IBD), including both ulcerative colitis and Crohn's disease, have a 2- to 3-fold greater lifetime risk of developing colorectal cancer compared with the general population. The development of colitis-associated cancer (CAC) is thought to be multifaceted and is probably due to a combination of genetic factors, epigenetic factors and the duration, extent and severity of disease. Recently, epigenetic alterations, in particular alterations in DNA methylation, have been observed during inflammation and inflammation-associated carcinogenesis. The mediators of this, the significance of these changes in DNA methylation and the effect this has on gene expression and the malignant transformation of the epithelial cells during IBD and CAC are discussed in this review. The recent advances in technologies to study genome-wide DNA methylation and the therapeutic potential of understanding these molecular mechanisms are also highlighted.