A novel pathway links oxidative stress to loss of insulin growth factor-2 (IGF2) imprinting through NF-κB activation

Targeting IGF2 to reprogram the tumor microenvironment for enhanced viro-immunotherapy

BACKGROUND

The FDA approval of oncolytic herpes simplex-1 virus (oHSV) therapy underscores its therapeutic promise and safety as a cancer immunotherapy. Despite this promise, the current efficacy of oHSV is significantly limited to a small subset of patients largely due to the resistance in tumor and tumor microenvironment (TME).

METHODS

RNA sequencing (RNA-Seq) was used to identify molecular targets of oHSV resistance. Intracranial human and murine glioma or breast cancer brain metastasis (BCBM) tumor-bearing mouse models were employed to elucidate the mechanism underlying oHSV therapy-induced resistance.

RESULTS

Transcriptome analysis identified IGF2 as one of the top-secreted proteins following oHSV treatment. Moreover, IGF2 expression was significantly upregulated in 10 out of 14 recurrent GBM patients after treatment with oHSV, rQNestin34.5v.2 (71.4%; P = .0020) (ClinicalTrials.gov, NCT03152318). Depletion of IGF2 substantially enhanced oHSV-mediated tumor cell killing in vitro and improved survival of mice bearing BCBM tumors in vivo. To mitigate the oHSV-induced IGF2 in the TME, we constructed a novel oHSV, oHSV-D11mt, secreting a modified IGF2R domain 11 (IGF2RD11mt) that acts as IGF2 decoy receptor. Selective blocking of IGF2 by IGF2RD11mt significantly increased cytotoxicity, reduced oHSV-induced neutrophils/PMN-MDSCs infiltration, and reduced secretion of immune suppressive/proangiogenic cytokines, while increased CD8 + cytotoxic T lymphocytes (CTLs) infiltration, leading to enhanced survival in GBM or BCBM tumor-bearing mice.

CONCLUSIONS

This is the first study reporting that oHSV-induced secreted IGF2 exerts a critical role in resistance to oHSV therapy, which can be overcome by oHSV-D11mt as a promising therapeutic advance for enhanced viro-immunotherapy.

Long-term environmental metal exposure is associated with hypomethylation of CpG sites in NFKB1 and other genes related to oncogenesis

BACKGROUND

Long-term environmental exposure to metals leads to epigenetic changes and may increase risks to human health. The relationship between the type and level of metal exposure and epigenetic changes in subjects exposed to high concentrations of metals in the environment is not yet clear. The aim of our study is to find the possible association of environmental long-term exposure to metals with DNA methylation changes of genes related to immune response and carcinogenesis. We investigated the association of plasma levels of 21 essential and non-essential metals detected by ICP-MS and the methylation level of 654 CpG sites located on NFKB1, CDKN2A, ESR1, APOA5, IGF2 and H19 genes assessed by targeted bisulfite sequencing in a cohort of 40 subjects living near metal mining area and 40 unexposed subjects. Linear regression was conducted to find differentially methylated positions with adjustment for gender, age, BMI class, smoking and metal concentration.

RESULTS

In the metal-exposed group, five CpGs in the NFKB1 promoter region were hypomethylated compared to unexposed group. Four differentially methylated positions (DMPs) were associated with multiple metals, two of them are located on NFKB1 gene, and one each on CDKN2A gene and ESR1 gene. Two DMPs located on NFKB1 (chr4:102500951, associated with Be) and IGF2 (chr11:2134198, associated with U) are associated with specific metal levels. The methylation status of the seven CpGs located on NFKB1 (3), ESR1 (2) and CDKN2A (2) positively correlated with plasma levels of seven metals (As, Sb, Zn, Ni, U, I and Mn).

CONCLUSIONS

Our study revealed methylation changes in NFKB1, CDKN2A, IGF2 and ESR1 genes in individuals with long-term human exposure to metals. Further studies are needed to clarify the effect of environmental metal exposure on epigenetic mechanisms and pathways involved.

Synergic Action of Insulin-like Growth Factor-2 and miRNA-483 in Pterygium Pathogenesis

Pterygium is a multifactorial disease in which UV-B is speculated to play a key role by inducing oxidative stress and phototoxic DNA damage. In search for candidate molecules that are useful for justifying the intense epithelial proliferation observed in pterygium, our attention has been focused on Insulin-like Growth Factor 2 (IGF-2), mainly detected in embryonic and fetal somatic tissues, which regulate metabolic and mitogenic functions. The binding between IGF-2 and its receptor Insulin-like Growth Factor 1 Receptor (IGF-1R) activates the PI3K-AKT pathway, which leads to the regulation of cell growth, differentiation, and the expression of specific genes. Since IGF2 is regulated by parental imprinting, in different human tumors, the IGF2 Loss of Imprinting (LOI) results in IGF-2- and IGF2-derived intronic miR-483 overexpression. Based on these activities, the purpose of this study was to investigate the overexpression of IGF-2, IGF-1R, and miR-483. Using an immunohistochemical approach, we demonstrated an intense colocalized epithelial overexpression of IGF-2 and IGF-1R in most pterygium samples (Fisher's exact test, p = 0.021). RT-qPCR gene expression analysis confirmed IGF2 upregulation and demonstrated miR-483 expression in pterygium compared to normal conjunctiva (253.2-fold and 12.47-fold, respectively). Therefore, IGF-2/IGF-1R co-expression could suggest their interplay through the two different paracrine/autocrine IGF-2 routes for signaling transfer, which would activate the PI3K/AKT signaling pathway. In this scenario, miR-483 gene family transcription might synergically reinforce IGF-2 oncogenic function through its boosting pro-proliferative and antiapoptotic activity.

TGFB3-AS1 promotes Hcy-induced inflammation of macrophages via inhibiting the maturity of miR-144 and upregulating Rap1a

It has been demonstrated that homocysteine (Hcy) can cause inflammatory diseases. Long noncoding RNAs (lncRNA) and microRNAs (miRNAs) are involved in this biological process, but the mechanism underlying Hcy-induced inflammation remains poorly understood. Here, we found that lncRNA TGFB3-AS1 was highly expressed in macrophages treated with Hcy and the peripheral blood monocytes from cystathionine beta-synthase heterozygous knockout (CBS^+/−) mice with a high-methionine diet using lncRNA microarray. In vivo and in vitro experiments further confirmed that TGFB3-AS1 accelerated Hcy-induced inflammation of macrophages through the Rap1a/wnt signaling pathway. Meanwhile, TGFB3-AS1 interacted with Rap1a and reduced degradation of Rap1a through inhibiting its ubiquitination in macrophages treated with Hcy. Rap1a mediated inflammation induced by Hcy and serves as a direct target of miR-144. Moreover, TGFB3-AS1 regulated miR-144 by binding to pri-miR-144 and inhibiting its maturation, which further regulated Rap1a expression. More importantly, we found that high expression of TGFB3-AS1 was positively correlated with the levels of Hcy and proinflammatory cytokines in serum of healthy individuals and patients with HHcy. Our study revealed a novel mechanism by which TGFB3-AS1 promoted inflammation of macrophages through inhibiting miR-144 maturation to stay miR-144 regulated inhibition of functional Rap1a expression.

The roles of inducible chromatin and transcriptional memory in cellular defense system responses to redox-active pollutants

People are exposed to wide range of redox-active environmental pollutants. Air pollution, heavy metals, pesticides, and endocrine disrupting chemicals can disrupt cellular redox status. Redox-active pollutants in our environment all trigger their own sets of specific cellular responses, but they also activate a common set of general stress responses that buffer the cell against homeostatic insults. These cellular defense system (CDS) pathways include the heat shock response, the oxidative stress response, the hypoxia response, the unfolded protein response, the DNA damage response, and the general stress response mediated by the stress-activated p38 mitogen-activated protein kinase. Over the past two decades, the field of environmental epigenetics has investigated epigenetic responses to environmental pollutants, including redox-active pollutants. Studies of these responses highlight the role of chromatin modifications in controlling the transcriptional response to pollutants and the role of transcriptional memory, often referred to as "epigenetic reprogramming", in predisposing previously exposed individuals to more potent transcriptional responses on secondary challenge. My central thesis in this review is that high dose or chronic exposure to redox-active pollutants leads to transcriptional memories at CDS target genes that influence the cell's ability to mount protective responses. To support this thesis, I will: (1) summarize the known chromatin features required for inducible gene activation; (2) review the known forms of transcriptional memory; (3) discuss the roles of inducible chromatin and transcriptional memory in CDS responses that are activated by redox-active environmental pollutants; and (4) propose a conceptual framework for CDS pathway responsiveness as a readout of total cellular exposure to redox-active pollutants.

Alteration of Metabolic Conditions Impacts the Regulation of IGF-II/H19 Imprinting Status in Prostate Cancer

Prostate cancer is the second major cause of male cancer deaths. Obesity, type 2 diabetes, and cancer risk are linked. Insulin-like growth factor II (IGF-II) is involved in numerous cellular events, including proliferation and survival. The IGF-II gene shares its locus with the lncRNA, H19. IGF-II/H19 was the first gene to be identified as being "imprinted"-where the paternal copy is not transcribed-a silencing phenomenon lost in many cancer types. We disrupted imprinting behaviour in vitro by altering metabolic conditions and quantified it using RFLP, qPCR and pyrosequencing; changes to peptide were measured using RIA. Prostate tissue samples were analysed using ddPCR, pyrosequencing and IHC. We compared with in silico data, provided by TGCA on the cBIO Portal. We observed disruption of imprinting behaviour, in vitro, with a significant increase in IGF-II and a reciprocal decrease in H19 mRNA; the increased mRNA was not translated into peptides. In vivo, most specimens retained imprinting status apart from a small subset which showed reduced imprinting. A positive correlation was seen between IGF-II and H19 mRNA expression, which concurred with findings of larger Cancer Genome Atlas (TGCA) cohorts. This positive correlation did not affect IGF-II peptide. Our findings show that type 2 diabetes and/or obesity, can directly affect regulation growth factors involved in carcinogenesis, indirectly suggesting a modification of lifestyle habits may reduce cancer risk.

The role of insulin-like growth factors in the development of prostate cancer

INTRODUCTION

Preclinical, clinical, and population studies have provided robust evidence for an important role for the insulin-like growth factor (IGF) system in the development of prostate cancer.

AREAS COVERED

An overview of the IGF system is provided. The evidence implicating the IGF system in the development of prostate cancer is summarized. The compelling evidence culminated in a number of clinical trials of agents targeting the system; the reasons for the failure of these trials are discussed.

EXPERT OPINION

Clinical trials of agents targeting the IGF system in prostate cancer were terminated due to limited objective clinical responses and are unlikely to be resumed unless a convincing predictive biomarker is identified that would enable the selection of likely responders. The aging population and increased screening will lead to greater diagnosis of prostate cancer. Although the vast majority will be indolent disease, the epidemics of obesity and diabetes will increase the proportion that progress to clinical disease. The increased population of worried men will result in more trials aimed to reduce the risk of disease progression; actual clinical endpoints will be challenging and the IGFs remain the best intermediate biomarkers to indicate a response that could alter the course of disease.

CTCF loss mediates unique DNA hypermethylation landscapes in human cancers

Background

The chromatin insulator CCCTC-binding factor (CTCF) displays tissue-specific DNA binding sites that regulate transcription and chromatin organization. Despite evidence linking CTCF to the protection of epigenetic states through barrier insulation, the impact of CTCF loss on genome-wide DNA methylation sites in human cancer remains undefined.

Results

Here, we demonstrate that prostate and breast cancers within The Cancer Genome Atlas (TCGA) exhibit frequent copy number loss of CTCF and that this loss is associated with increased DNA methylation events that occur preferentially at CTCF binding sites. CTCF sites differ among tumor types and result in tissue-specific methylation patterns with little overlap between breast and prostate cancers. DNA methylation and transcriptome profiling in vitro establish that forced downregulation of CTCF leads to spatially distinct DNA hypermethylation surrounding CTCF binding sites, loss of CTCF binding, and decreased gene expression that is also seen in human tumors. DNA methylation inhibition reverses loss of expression at these CTCF-regulated genes.

Conclusion

These findings establish CTCF loss as a major mediator in directing localized DNA hypermethylation events in a tissue-specific fashion and further support its role as a driver of the cancer phenotype.

Adverse outcome pathways for ionizing radiation and breast cancer involve direct and indirect DNA damage, oxidative stress, inflammation, genomic instability, and interaction with hormonal regulation of the breast

Knowledge about established breast carcinogens can support improved and modernized toxicological testing methods by identifying key mechanistic events. Ionizing radiation (IR) increases the risk of breast cancer, especially for women and for exposure at younger ages, and evidence overall supports a linear dose-response relationship. We used the Adverse Outcome Pathway (AOP) framework to outline and evaluate the evidence linking ionizing radiation with breast cancer from molecular initiating events to the adverse outcome through intermediate key events, creating a qualitative AOP. We identified key events based on review articles, searched PubMed for recent literature on key events and IR, and identified additional papers using references. We manually curated publications and evaluated data quality. Ionizing radiation directly and indirectly causes DNA damage and increases production of reactive oxygen and nitrogen species (RONS). RONS lead to DNA damage and epigenetic changes leading to mutations and genomic instability (GI). Proliferation amplifies the effects of DNA damage and mutations leading to the AO of breast cancer. Separately, RONS and DNA damage also increase inflammation. Inflammation contributes to direct and indirect effects (effects in cells not directly reached by IR) via positive feedback to RONS and DNA damage, and separately increases proliferation and breast cancer through pro-carcinogenic effects on cells and tissue. For example, gene expression changes alter inflammatory mediators, resulting in improved survival and growth of cancer cells and a more hospitable tissue environment. All of these events overlap at multiple points with events characteristic of "background" induction of breast carcinogenesis, including hormone-responsive proliferation, oxidative activity, and DNA damage. These overlaps make the breast particularly susceptible to ionizing radiation and reinforce that these biological activities are important characteristics of carcinogens. Agents that increase these biological processes should be considered potential breast carcinogens, and predictive methods are needed to identify chemicals that increase these processes. Techniques are available to measure RONS, DNA damage and mutation, cell proliferation, and some inflammatory proteins or processes. Improved assays are needed to measure GI and chronic inflammation, as well as the interaction with hormonally driven development and proliferation. Several methods measure diverse epigenetic changes, but it is not clear which changes are relevant to breast cancer. In addition, most toxicological assays are not conducted in mammary tissue, and so it is a priority to evaluate if results from other tissues are generalizable to breast, or to conduct assays in breast tissue. Developing and applying these assays to identify exposures of concern will facilitate efforts to reduce subsequent breast cancer risk.

Adverse outcome pathways for ionizing radiation and breast cancer involve direct and indirect DNA damage, oxidative stress, inflammation, genomic instability, and interaction with hormonal regulation of the breast

Knowledge about established breast carcinogens can support improved and modernized toxicological testing methods by identifying key mechanistic events. Ionizing radiation (IR) increases the risk of breast cancer, especially for women and for exposure at younger ages, and evidence overall supports a linear dose-response relationship. We used the Adverse Outcome Pathway (AOP) framework to outline and evaluate the evidence linking ionizing radiation with breast cancer from molecular initiating events to the adverse outcome through intermediate key events, creating a qualitative AOP. We identified key events based on review articles, searched PubMed for recent literature on key events and IR, and identified additional papers using references. We manually curated publications and evaluated data quality. Ionizing radiation directly and indirectly causes DNA damage and increases production of reactive oxygen and nitrogen species (RONS). RONS lead to DNA damage and epigenetic changes leading to mutations and genomic instability (GI). Proliferation amplifies the effects of DNA damage and mutations leading to the AO of breast cancer. Separately, RONS and DNA damage also increase inflammation. Inflammation contributes to direct and indirect effects (effects in cells not directly reached by IR) via positive feedback to RONS and DNA damage, and separately increases proliferation and breast cancer through pro-carcinogenic effects on cells and tissue. For example, gene expression changes alter inflammatory mediators, resulting in improved survival and growth of cancer cells and a more hospitable tissue environment. All of these events overlap at multiple points with events characteristic of "background" induction of breast carcinogenesis, including hormone-responsive proliferation, oxidative activity, and DNA damage. These overlaps make the breast particularly susceptible to ionizing radiation and reinforce that these biological activities are important characteristics of carcinogens. Agents that increase these biological processes should be considered potential breast carcinogens, and predictive methods are needed to identify chemicals that increase these processes. Techniques are available to measure RONS, DNA damage and mutation, cell proliferation, and some inflammatory proteins or processes. Improved assays are needed to measure GI and chronic inflammation, as well as the interaction with hormonally driven development and proliferation. Several methods measure diverse epigenetic changes, but it is not clear which changes are relevant to breast cancer. In addition, most toxicological assays are not conducted in mammary tissue, and so it is a priority to evaluate if results from other tissues are generalizable to breast, or to conduct assays in breast tissue. Developing and applying these assays to identify exposures of concern will facilitate efforts to reduce subsequent breast cancer risk.

Screening of urine identifies PLA2G16 as a field defect methylation biomarker for prostate cancer detection

BACKGROUND

Prostate cancer (PC) is a multifocal disease. DNA methylation alterations are not restricted to the immediate peritumor environment, but spatially widespread in the adjacent and distant histologically normal prostate tissues. In the current study, we utilized high-throughput methylation arrays to identify epigenetic changes in the urine from men with and without cancer.

DESIGN, SETTING, AND PARTICIPANTS

DNA urine samples were enriched for methylated fragments using MBD methyl-binding antibodies and applied to high density CytoScanHD arrays. Significant loci were validated using quantitative pyrosequencing and binary logistic regression modeling applied to urine sample analyses in a training (n = 83) and validation approach (n = 84). Methylation alterations in prostate tissues using pyrosequencing at the PLA2G16 locus were examined in 38 histologically normal specimens from men with (TA, n = 26) and without (NTA, n = 12) cancer and correlated to gene expression.

RESULTS

Methylation microarrays identified 3,986 loci showing significantly altered methylation in the urine samples from patients with PC compared to those without (TA vs NTA; p<0.01). These loci were then compared against subjects with their prostates removed to exclude non-prostate cell markers yielding 196 significant regions. Multiple CpGs adjacent to PLA2G16 CpG island showed increased methylation in TA compared to NTA (p<0.01) in a large validation study of urine samples. The predictive accuracy of PLA2G16 methylation at CG2 showed the highest predictive value at 0.8 (odds ratio, 1.37; 95% confidence interval, 1.16-1.62; p<0.001). Using a probability cutoff of 0.065, the sensitivity and specificity of the multivariate model was 92% and 35%. When histologically normal prostate tissues/biopsies from patients with PC (TA) were compared to subjects without cancer, significant hypermethylation of PLA2G16 was noted (odds ratio, 1.35; 95% confidence interval, 1.07-1.71; p = 0.01).

CONCLUSION

PLA2G16 methylation defines an extensive field defect in histologically normal prostate tissue associated with PC. PLA2G16 methylation in urine and prostate tissues can detect the presence of PC.

Associations between H19 polymorphisms and neuroblastoma risk in Chinese children

BackgroundH19 polymorphisms have been reported to correlate with an increased susceptibility to a few types of cancers, although their role in neuroblastoma has not yet been clarified.Materials and methods We investigated the association between three single polymorphisms (rs2839698 G>A, rs3024270 C>G, and rs217727 G>A) and neuroblastoma susceptibility in Chinese Han populations. Three hundred ninety-three neuroblastoma patients and 812 healthy controls were enrolled from the Henan and Guangdong provinces. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to determine the strength of the association of interest.Results Separated and combined analyses revealed no associations of the rs2839698 G>A, rs3024270 C>G or rs217727 G>A polymorphisms and neuroblastoma susceptibility. In the stratification analysis, female children with rs3024270 GG genotypes had an increased neuroblastoma risk (adjusted OR = 1.61, 95% CI = 1.04-2.50, P=0.032).Conclusion The rs3024270 GG genotype might contribute to an increased neuroblastoma susceptibility in female Chinese children.

Methylation profiles of IL33 and CCL26 in bronchial epithelial cells are associated with asthma

AIM

This study aimed to characterize DNA methylation (DNA-me) in promoter region of IL33, IL1RL1 and CCL26 in asthma and their impacts on transcriptional activity in bronchial epithelial cells (BECs).

PATIENTS & METHODS

We performed bis-pyrosequencing, quantitative real-time PCR and sequencing in BECs from ten asthmatic and ten control individuals.

RESULTS

We detected lower DNA-me levels of IL33 and CCL26 in asthmatic than control BECs. No correlation was found between methylation and expression levels. Interestingly, carriers of a mutative allele in a haplotype within the promoter of IL33 had a lower IL33 DNA-me level and CCL26 gene expression correlated with eosinophil count.

CONCLUSION

These findings highlight the importance of investigating both epigenetic and genetic mechanisms in understanding the epithelial immune response in asthma.

Cancer Stem Cells: Emergent Nature of Tumor Emergency

A functional analysis of 167 genes overexpressed in Krebs-2 tumor initiating cells was performed. In the first part of the study, the genes were analyzed for their belonging to one or more of the three groups, which represent the three major phenotypic manifestation of malignancy of cancer cells, namely (1) proliferative self-sufficiency, (2) invasive growth and metastasis, and (3) multiple drug resistance. 96 genes out of 167 were identified as possible contributors to at least one of these fundamental properties. It was also found that substantial part of these genes are also known as genes responsible for formation and/or maintenance of the stemness of normal pluri-/multipotent stem cells. These results suggest that the malignancy is simply the ability to maintain the stem cell specific genes expression profile, and, as a consequence, the stemness itself regardless of the controlling effect of stem niches. In the second part of the study, three stress factors combined into the single concept of "generalized cellular stress," which are assumed to activate the expression of these genes, were defined. In addition, possible mechanisms for such activation were identified. The data obtained suggest the existence of a mechanism for the de novo formation of a pluripotent/stem phenotype in the subpopulation of "committed" tumor cells.

Role of CTCF in DNA damage response

CCCTC-binding factor (CTCF) is a highly conserved, ubiquitously expressed zinc finger protein. CTCF is a multifunctional protein, associated with a number of vital cellular processes such as transcriptional activation, repression, insulation, imprinting and genome organization. Emerging evidence indicates that CTCF is also involved in DNA damage response. In this review, we focus on the newly identified role of CTCF in facilitating DNA double-strand break repair. Due to the large number of cellular processes in which CTCF is involved, factors that functionally affect CTCF could have serious implications on genomic stability. It is becoming increasingly clear that exposure to environmental toxicants could have adverse effects on CTCF functions. Here we discuss the various ways that environmental toxicants could impact CTCF functions and the potential consequences on DNA damage response.

Insulin-like growth factor 2: a poor prognostic biomarker linked to racial disparity in women with uterine carcinosarcoma

The objective of this study was to investigate the relationship of insulin‐like growth factor 2 (IGF2) expression and survival in women with uterine carcinosarcoma (UCS). Insulin‐like growth factor 2 protein expression was determined by immunohistochemical staining of tumor tissues from 103 patients with UCS. The H‐score (product of staining intensity and percentage positive cells) was quantified for the epithelial cytoplasmic (EC), epithelial nuclear (EN), and malignant stromal compartments. Multivariable Cox proportional hazard regression models were used to examine the relationship of IGF2 levels with progression‐free survival (PFS) and overall survival (OS). Adjusting for stage, race, and adjuvant therapy, PFS and OS were reduced in patients with high IGF2 (H‐score ≥ median) in the EC and EN compartments. Black race was independently associated with reduced PFS and OS in patients with early‐stage disease, and IGF2 levels in the EC were higher in black than in white patients (P = 0.02, Wilcoxon test). In a race‐stratified multivariable analysis, high IGF2 in the epithelial compartments more than doubled the risk of death in black women; HR = 2.43 (95% CI: 1.18–5.01, P = 0.02) for high IGF2 in the EC; and HR = 2.34 (95% CI: 1.25–4.39, P = 0.008) for high IGF2 in the EN. In conclusion, high tumor IGF2 expression is an independent risk factor for reduced PFS and OS in UCS. Black women have elevated tumor IGF2 compared with white women, and decreased survival associated with high IGF2. These findings identify IGF2 as a candidate biomarker for survival linked to racial disparity in women with UCS.

Insulin-like growth factor 2 expression in prostate cancer is regulated by promoter-specific methylation

Deregulation of the insulin-like growth factor (IGF) axis and dysbalance of components of the IGF system as potential therapeutic targets have been described in different tumor types. IGF2 is a major embryonic growth factor and an important activator of IGF signaling. It is regulated by imprinting in a development- and tissue-dependent manner and has been implicated in a broad range of malignancies including prostate cancer (PCa). Loss of imprinting (LOI) usually results in bi-allelic gene expression and increased levels of IGF2. However, the regulatory mechanisms and the pathophysiological impact of altered IGF2 expression in PCa remain elusive. Here, we show that in contrast to many other tumors, IGF2 mRNA and protein levels were decreased in 80% of PCa in comparison with non-neoplastic adjacent prostate and were independent of LOI status. Instead, IGF2 expression in both tumors and adjacent prostate depended on preferential usage of the IGF2 promoters P3 and P4. Decreased IGF2 expression in tumors was strongly related to hypermethylation of these two promoters. Methylation of the A region in promoter P4 correlated specifically with IGF2 expression in the 20% of PCa where IGF2 was higher in tumors than in adjacent prostate. We conclude that IGF2 is downregulated in most PCa and may be particularly relevant during early stages of tumor development or during chemotherapy and androgen deprivation. PCa differs from other tumors in that IGF2 expression is mainly regulated through methylation of promoter-specific and not by imprinting. Targeting of promoter-specific regions may have relevance for the adjuvant treatment of PCa.

Oxidative stress and prostatic diseases

Prostatic diseases are a common health problem among males in Western countries, and include chronic prostatic diseases, which have an unclear pathogenesis and few treatment options. In vitro and in vivo studies describe oxidative stress as a major pathway involved in the occurrence of benign prostatic hyperplasia, prostatic cancer and chronic prostatitis. Thus, the oxidative stress cascade is a potential target for the treatment of prostatic diseases. This paper presents a systematic review of the available data concerning the association between oxidative stress and the most common chronic prostatic diseases, and describes the available treatment options that act upon this pathway.

Low-Dose Ionizing Radiation Exposure, Oxidative Stress and Epigenetic Programing of Health and Disease

Ionizing radiation exposure from medical diagnostic imaging has greatly increased over the last few decades. Approximately 80% of patients who undergo medical imaging are exposed to low-dose ionizing radiation (LDIR). Although there is widespread consensus regarding the harmful effects of high doses of radiation, the biological effects of low-linear energy transfer (LET) LDIR is not well understood. LDIR is known to promote oxidative stress, however, these levels may not be large enough to result in genomic mutations. There is emerging evidence that oxidative stress causes heritable modifications via epigenetic mechanisms (DNA methylation, histone modification, noncoding RNA regulation). These epigenetic modifications result in permanent cellular transformations without altering the underlying DNA nucleotide sequence. This review summarizes the major concepts in the field of epigenetics with a focus on the effects of low-LET LDIR (<100 mGy) and oxidative stress on epigenetic gene modification. In this review, we show evidence that suggests that LDIR-induced oxidative stress provides a mechanistic link between LDIR and epigenetic gene regulation. We also discuss the potential implication of LDIR exposure during pregnancy where intrauterine fetal development is highly susceptible to oxidative stress-induced epigenetic programing.

A Tox21 Approach to Altered Epigenetic Landscapes: Assessing Epigenetic Toxicity Pathways Leading to Altered Gene Expression and Oncogenic Transformation In Vitro

An emerging vision for toxicity testing in the 21st century foresees in vitro assays assuming the leading role in testing for chemical hazards, including testing for carcinogenicity. Toxicity will be determined by monitoring key steps in functionally validated molecular pathways, using tests designed to reveal chemically-induced perturbations that lead to adverse phenotypic endpoints in cultured human cells. Risk assessments would subsequently be derived from the causal in vitro endpoints and concentration vs. effect data extrapolated to human in vivo concentrations. Much direct experimental evidence now shows that disruption of epigenetic processes by chemicals is a carcinogenic mode of action that leads to altered gene functions playing causal roles in cancer initiation and progression. In assessing chemical safety, it would therefore be advantageous to consider an emerging class of carcinogens, the epigenotoxicants, with the ability to change chromatin and/or DNA marks by direct or indirect effects on the activities of enzymes (writers, erasers/editors, remodelers and readers) that convey the epigenetic information. Evidence is reviewed supporting a strategy for in vitro hazard identification of carcinogens that induce toxicity through disturbance of functional epigenetic pathways in human somatic cells, leading to inactivated tumour suppressor genes and carcinogenesis. In the context of human cell transformation models, these in vitro pathway measurements ensure high biological relevance to the apical endpoint of cancer. Four causal mechanisms participating in pathways to persistent epigenetic gene silencing were considered: covalent histone modification, nucleosome remodeling, non-coding RNA interaction and DNA methylation. Within these four interacting mechanisms, 25 epigenetic toxicity pathway components (SET1, MLL1, KDM5, G9A, SUV39H1, SETDB1, EZH2, JMJD3, CBX7, CBX8, BMI, SUZ12, HP1, MPP8, DNMT1, DNMT3A, DNMT3B, TET1, MeCP2, SETDB2, BAZ2A, UHRF1, CTCF, HOTAIR and ANRIL) were found to have experimental evidence showing that functional perturbations played “driver” roles in human cellular transformation. Measurement of epigenotoxicants presents challenges for short-term carcinogenicity testing, especially in the high-throughput modes emphasized in the Tox21 chemicals testing approach. There is need to develop and validate in vitro tests to detect both, locus-specific, and genome-wide, epigenetic alterations with causal links to oncogenic cellular phenotypes. Some recent examples of cell-based high throughput chemical screening assays are presented that have been applied or have shown potential for application to epigenetic endpoints.

Paternal chronic colitis causes epigenetic inheritance of susceptibility to colitis

Inflammatory bowel disease (IBD) arises by unknown environmental triggers in genetically susceptible individuals. Epigenetic regulation of gene expression may integrate internal and external influences and may thereby modulate disease susceptibility. Epigenetic modification may also affect the germ-line and in certain contexts can be inherited to offspring. This study investigates epigenetic alterations consequent to experimental murine colitis induced by dextran sodium sulphate (DSS), and their paternal transmission to offspring. Genome-wide methylome- and transcriptome-profiling of intestinal epithelial cells (IECs) and sperm cells of males of the F₀ generation, which received either DSS and consequently developed colitis (F₀^DSS), or non-supplemented tap water (F₀^Ctrl) and hence remained healthy, and of their F₁ offspring was performed using reduced representation bisulfite sequencing (RRBS) and RNA-sequencing (RNA-Seq), respectively. Offspring of F₀^DSS males exhibited aberrant methylation and expression patterns of multiple genes, including Igf1r and Nr4a2, which are involved in energy metabolism. Importantly, DSS colitis in F₀^DSS mice was associated with decreased body weight at baseline of their F₁ offspring, and these F₁ mice exhibited increased susceptibility to DSS-induced colitis compared to offspring from F₀^Ctrl males. This study hence demonstrates epigenetic transmissibility of metabolic and inflammatory traits resulting from experimental colitis.

Oxidative stress in benign prostatic hyperplasia: a systematic review

BACKGROUND

Several parameters including inflammatory mediators, hormones, dietary factors, inflammatory genes, and oxidative stress (OS) have been considered to play a role in the development of benign prostatic hyperplasia (BPH). Prostate tissue damage and OS may lead to compensatory cellular proliferation with resulting hyperplastic growth.

METHODS

We searched MEDLINE for articles in English published up to March 2014 using the key words 'oxidative stress', 'antioxidants' and 'benign prostatic hyperplasia'.

RESULTS

Prostatic inflammation can cause the generation of free radicals. The extent of oxidative damage can be exacerbated by a decreased efficiency of antioxidant defense mechanisms. The balance between OS and the antioxidant component also has a role in developing prostate disease. Several works show the role of oxidant products and of depletion of antioxidant substances in BPH patients. It is accepted that free radicals play a role in carcinogenesis and that BPH should be considered a premalignant condition which may evolve into prostate cancer. High OS parameters and low antioxidant activity are more prominent in prostate cancer patients compared with BPH and controls.

CONCLUSIONS

Further studies are needed to clarify the potential role of antioxidants in BPH also in view of preventing the progression to prostate cancer.

Loss of imprinting of IGF2 in fibroadenomas and phyllodes tumors of the breast

Loss of imprinting (LOI) of insulin-like growth factor 2 (IGF2) is thought to be implicated in the pathogenesis of some tumors by upregulating IGF2 mRNA but its role in the pathogenesis of fibroadenomas (FAs) and phyllodes tumors (PTs) of the breast is yet to be studied. LOI of IGF2 was investigated in 25 FAs and 17 PTs which were heterozygous for Apa I polymorphism, and was found to be present in 13 FAs and 12 PTs. IGF2 mRNA expression was more upregulated in FAs and PTs than in paired surrounding normal tissues and laser microdissection showed that IGF2 mRNA expression was significantly higher in the stromal than the epithelial cells. LOI was not associated with upregulation of IGF2 mRNA, nor were MED12 mutations and methylation status of the differentially methylated region 0 (DMR0) of IGF2. These results demonstrate that IGF2 mRNA expression is more upregulated in FAs and PTs than in normal tissues, especially in their stromal cells, but such an upregulation is not related to LOI of IGF2, and that hypomethylation of DMR0 is unlikely to be involved in induction of LOI.

IGF2 signaling and regulation in cancer

Upregulation of IGF2 occurs in both childhood and adult malignancies. Its overexpression is associated with resistance to chemotherapy and worse prognosis. IGF2 promoter usage is developmentally regulated; however, malignant tissues are characterized by re-activation of the fetal IGF2 promoters, especially P3. In this review, we describe the mechanisms of IGF2 signaling and regulation in normal and malignant tissues and their clinical implications.

The impact of first trimester phthalate and phenol exposure on IGF2/H19 genomic imprinting and birth outcomes

Genomic imprinting leads to parent-of-origin specific gene expression and is determined by epigenetic modification of genes. The paternally expressed gene insulin-like growth-factor 2 (IGF2) is located about ~100kb from the maternally expressed non-coding gene H19 on human chromosome 11, and both genes play major roles in embryonic and placental growth. Given adverse gestational environments can influence DNA methylation patterns in extra-embryonic tissues, we hypothesized that prenatal exposure to endocrine disrupting chemicals (EDCs) alters H19 and IGF2 methylation in placenta. Our study was restricted to a total of 196 women co-enrolled in the Predictors of Preeclampsia Study and the Harvard Epigenetic Birth Cohort. First trimester urine concentrations of 8 phenols and 11 phthalate metabolites were measured and used to characterize EDC exposure profiles. We assessed methylation of differentially methylated regions (DMRs) by pyrosequencing of H19, IGF2DMR0, and IGF2DMR2 and correlated values with phenol and phthalate metabolites. We also assessed overall expression and allele-specific expression of H19 and IGF2. We found several significant associations between DNA methylation and additive biomarker measurements. A significant decrease in H19 methylation was associated with high levels of the sum (Σ) of phthalate metabolites and metabolites of low molecular weight (LMW) phthalates. Σphthalate and LMW phthalate concentrations were inversely associated with IGF2DMR0 methylation values. Variation in methylation was not associated with changes in allele-specific expression. However increased deviation of allele-specific expression of H19 was associated with Σdi(2-ethylhexyl) phthalate metabolites and high molecular weight phthalates. Neither methylation nor expression of these imprinted regions had a significant impact on birth length or birth weight. Overall, our study provides new insight into an epigenetic mechanism that occurs following EDC exposure.