Epigenetic setting for long-term expression of estrogen receptor α and androgen receptor in cells

Tumor Suppressive Maspin-Sensitized Prostate Cancer to Drug Treatment Through Negative Regulating Androgen Receptor Expression

Overactivation of androgen receptor (AR)-mediated signal has been extensively implicated in prostate cancer (CaP) development, progression, and recurrence, which makes it an attractive therapeutic target. Meanwhile, as an endogenous inhibitor of histone deacetylase 1 (HDAC 1), tumor-suppressive mammary serine protease inhibitor (maspin) was reported to sensitize drug-induced apoptosis with a better therapeutic outcome in CaP, but the relationship between AR and maspin remains unclear. In the current study, treatment of 5'-Aza or MS-275/enzalutamide induced poly (ADP-ribose) polymerase (PARP) cleavage and p-H2A.X in CaP cells with an increase of maspin expression but a decrease of AR. Then, treatment with protease inhibitor MG132 did not rescue the above drug-induced loss of AR. In addition, modulation of maspin expression by gene recombinant or siRNA technology showed an inverse correlation between expression of maspin and AR, consequently affecting the AR-regulated downstream gene transcription (e.g., NKX3.1 and TMPRSS2). Bioinformatics analysis of the data extracted from the National Center for Biotechnology Information Gene Expression Omnibus (NCBI GEO) database also revealed an inverse correlation between low maspin expression and high AR level in advanced CaP. Furthermore, chromatin immunoprecipitation (ChIP) assay using anti-maspin antibody identified that a portion of AR promoter sequence was co-precipitated and presented in the immunoprecipitated complex. Finally, maspin-mediated repression of AR was induced by treatment of MS-275, which promoted enzalutamide treatment efficacy with decrease of prostate-specific antigen (PSA) expression in LNCaP and 22RV1 cells. Taken together, the data not only demonstrated maspin-mediated repression of AR to augment drug anti-tumor activity but also provided in-depth support for combination of HDAC inhibitors with AR antagonist in CaP therapy.

Androgen and estrogen sensitivity of bird song: a comparative view on gene regulatory levels

Singing of songbirds is sensitive to testosterone and its androgenic and estrogenic metabolites in a species-specific way. The hormonal effects on song pattern are likely mediated by androgen receptors (AR) and estrogen receptor alpha (ERα), ligand activated transcription factors that are expressed in neurons of various areas of the songbirds' vocal control circuit. The distribution of AR in this circuit is rather similar between species while that of ERα is species variant and concerns a key vocal control area, the HVC (proper name). We discuss the regulation of the expression of the cognate AR and ERα and putative splice variants. In particular, we suggest that transcription factor binding sites in the promoter of these receptors differ between bird species. Further, we suggest that AR- and ERα-dependent gene regulation in vocal areas differs between species due to species-specific DNA binding sites of putative target genes that are required for the transcriptional activity of the receptors. We suggest that species differences in the distribution of AR and ERα in vocal areas and in the genomic sensitivity to these receptors contribute to species-specific hormonal regulation of the song.

An epigenetic basis for autism spectrum disorder risk and oral contraceptive use

In the United States 1 in 68 children are diagnosed with autism spectrum disorder (ASD). Although the etiology is unknown, many scientists believe ASD is caused by a combination of genetic and environmental factors and/or epigenetic factors. The widespread use of oral contraceptives is one environmental risk factor that has been greatly overlooked in the biomedical literature. Oral contraceptives, synthetic hormones created to imitate natural human hormones and disrupt endogenous endocrine function to inhibit pregnancy, may be causing the harmful neurodevelopmental effects that result in the increased prevalence of ASD. It is conceivable that the synthetic hormones repeatedly assault the oocyte causing persistent changes in expression of the estrogen receptor beta gene. Ethinylestradiol, a known endocrine disruptor, may trigger DNA methylation of the estrogen receptor beta gene causing decreased mRNA resulting in impaired brain estrogen signaling in progeny. In addition, it is possible the deleterious effects are transgenerational as the estrogen receptor gene and many of its targets may be imprinted and the methylation marks protected from global demethylation and preserved through fertilization and beyond to progeny generations. This article will delineate the hypothesis that ethinylestradiol activates DNA methylation of the estrogen receptor beta gene causing decreased mRNA resulting in diminished brain estrogen signaling in offspring of mothers exposed to oral contraceptives. Considering the detrimental epigenetic and transgenerational effects proposed, it calls for further study.

Epigenetic modifications of gene promoter DNA in the liver of adult female mice masculinized by testosterone

Testosterone (T) is known to masculinize the female phenotype of the liver, evidenced as up- and down-regulated expressions of male- and female-predominant genes, respectively, involved in hepatic metabolism. This study is aimed at identifying epigenetic modifications of promoters of these differently expressed genes in the liver after masculinization by T of adult female C57BL/6 mice using methylated DNA immunoprecipitation and NimbleGen microarrays. Among the 17,354 promoters examined, 82 promoters in the liver have been identified to be significantly changed by T (p<0.05), with 47 and 35 promoters exhibiting increased and decreased DNA methylation, respectively. Most of these promoters display the changes of DNA methylation in their Ups-regions, which are between +500 and +2000 bp upstream from the transcription start site (TSS) of the genes. Less T-induced modifications have been detected in the Cor-regions of the promoters, i.e., +500 to -500 bp around the TSS. Only 13 and 7 Cor-promoters are hyper- and hypo-methylated, respectively, among which are 10 hyper- and 5 hypo-methylated promoters of genes with annotated functions. Surprisingly, the promoters are largely unmethylated in those genes whose expression has been previously found to be permanently deregulated by T in the liver, as e.g. the T-upregulated male-predominant genes Cyp7b1, Cyp2d9, Cyp4a10, Ugt2b1, Ugt2b38, Hsd3b5, Slco1a1 as well as the T-downregulated female-predominant genes Cyp2b9, Cyp2b13, Cyp3a41, Cyp3a44, Fmo3, Sult2a2, respectively. Though methylatable, the promoter DNA of Ar, Esr1, and Esr2 remained unaffected by T. However, T decreases DNA-methylation of the Cor-promoter region of Ddc encoding the AR-coactivator dopa decarboxylase. Among the identified 15 Cor-promoters of genes with annotated functions are also those of Defb43, Cst11, and Sele involved in innate immunity. Our data support the view that T may exert long-lasting epigenetic effects on functions of the liver-inherent immune system.

Methylation of migraine-related genes in different tissues of the rat

17ß-Estradiol, an epigenetic modulator, is involved in the increased prevalence of migraine in women. Together with the prophylactic efficacy of valproate, which influences DNA methylation and histone modification, this points to the involvement of epigenetic mechanisms. Epigenetic studies are often performed on leukocytes, but it is unclear to what extent methylation is similar in other tissues. Therefore, we investigated methylation of migraine-related genes that might be epigenetically regulated (CGRP-ergic pathway, estrogen receptors, endothelial NOS, as well as MTHFR) in different migraine-related tissues and compared this to methylation in rat as well as human leukocytes. Further, we studied whether 17ß-estradiol has a prominent role in methylation of these genes. Female rats (n = 35) were ovariectomized or sham-operated and treated with 17β-estradiol or placebo. DNA was isolated and methylation was assessed through bisulphite treatment and mass spectrometry. Human methylation data were obtained using the Illumina 450k genome-wide methylation array in 395 female subjects from a population-based cohort study. We showed that methylation of the Crcp, Calcrl, Esr1 and Nos3 genes is tissue-specific and that methylation in leukocytes was not correlated to that in other tissues. Interestingly, the interindividual variation in methylation differed considerably between genes and tissues. Furthermore we showed that methylation in human leukocytes was similar to that in rat leukocytes in our genes of interest, suggesting that rat may be a good model to study human DNA methylation in tissues that are difficult to obtain. In none of the genes a significant effect of estradiol treatment was observed.

Differential androgen receptor expression and DNA methylation state in striatum song nucleus Area X between wild and domesticated songbird strains

In songbirds, a specialized neural system, the song system, is responsible for acquisition and expression of species-specific vocal patterns. We report evidence for differential gene expression between wild and domesticated strains having different learned vocal phenotypes. A domesticated strain of the wild white-rumped munia, the Bengalese finch, has a distinct song pattern with a more complicated syntax than the wild strain. We identified differential androgen receptor (AR) expression in basal ganglia nucleus Area X GABAergic neurons between the two strains, and within different domesticated populations. Differences in AR expression were correlated with the mean coefficient of variation of the inter-syllable duration in the two strains. Differential AR expression in Area X was observed before the initiation of singing, suggesting that inherited and/or early developmental mechanisms may affect expression within and between strains. However, there were no distinct differences in regions upstream of the AR start codon among all the birds in the study. In contrast, an epigenetic modification, DNA methylation state in regions upstream of AR in Area X, was observed to differ between strains and within domesticated populations. These results provide insight into the molecular basis of behavioral evolution through the regulation of hormone-related genes and demonstrate the potential association between epigenetic modifications and behavioral phenotype regulation.

Effect of histone deacetylase and DNA methyltransferase inhibitors on the expression of the androgen receptor gene in androgen-independent prostate cancer cell lines

Androgen receptor (AR) expression in prostate cancer (CaP) cells varies due to the multiple changes including epigenetic modifications such as DNA methylation and histone deacetylation. DNA methyltransferase and histone deacetylase inhibitors are promising for the treatment of CaP. The aim of our study was to analyze the 5-aza-2'-deoxycytidine (Aza‑dC) and sodium butyrate (NaB) effects on CaP cells with modified AR gene expression. The androgen-independent human prostate cancer cell lines PC3 (lacking a functional AR) and DU145 (strongly limited expression due to methylations in the AR gene) were used. PCR of bisulfite-modified DNA and RT-PCR with bisulfite-sequencing were used for AR gene analysis of DU145 and PC3 cells following their treatment with Aza-dC and/or NaB. Re-acetylated histones around the AR gene were detected by conventional PCR of immunoprecipitated DNA obtained from treated cells. In both cell lines without the AR expression, the combined treatment was followed with significant decrease of cell viability. The co-treatment of DU145 cells caused site-specific demethylation in the AR promoter region followed by gene re-expression and increased acetylation in histones H3 and H4. The co-treatment with Aza-dC and NaB was the most effective in demethylation and re-expression of the AR gene. In the AR gene promoter, the location and density of deme-thylated CpGs indicated the existence of distinct promoter hot spot that could be a target of AR gene inactivation therapy of CaP patients during androgen deprivation.

Hsp90 inhibitors and drug resistance in cancer: the potential benefits of combination therapies of Hsp90 inhibitors and other anti-cancer drugs

Hsp90 is a chaperone protein that interacts with client proteins that are known to be in the cell cycle, signaling and chromatin-remodeling pathways. Hsp90 inhibitors act additively or synergistically with many other drugs in the treatment of both solid tumors and leukemias in murine tumor models and humans. Hsp90 inhibitors potentiate the actions of anti-cancer drugs that target Hsp90 client proteins, including trastuzumab (Herceptin™) which targets Her2/Erb2B, as Hsp90 inhibition elicits the drug effects in cancer cell lines that are otherwise resistant to the drug. A phase II study of the Hsp90 inhibitor 17-AAG and trastuzumab showed that this combination therapy has anticancer activity in patients with HER2-positive metastatic breast cancer progressing on trastuzumab. In this review, we discuss the results of Hsp90 inhibitors in combination with trastuzumab and other cancer drugs. We also discuss recent results from yeast focused on the genetics of drug resistance when Hsp90 is inhibited and the implications that this might have in understanding the effects of genetic variation in treating cancer in humans.

Single-stranded noncoding RNAs mediate local epigenetic alterations at gene promoters in rat cell lines

A growing number of noncoding RNAs (ncRNAs) are thought to be involved in sequence-specific alterations of epigenetic processes, mostly causing gene repression. In this study, promoter-associated ncRNAs (pancRNAs >200 nucleotides in size) that were endogenously generated from the sense strand at Map2b, antisense strand at Nefl, and both strands at Vim were investigated regarding their epigenetic potential as positive or negative regulators in rat pheochromocytoma (PC12) and fibroblast (normal rat kidney) cell lines. The respective antisense pancRNAs were associated with several active chromatin marks at the Nefl and Vim promoters. Forced expression of fragments expressing the antisense pancRNAs caused sequence-specific DNA demethylation, whereas a decrease of expression induced methylation of the same sequences. In contrast, perturbing the expression of the two sense pancRNAs did not change the DNA methylation status. These results suggest that a fraction of naturally occurring ncRNAs acts in cis as a single-stranded form and that the transcriptional orientation of pancRNA is important for the establishment of sequence-specific epigenetic modifications consistent with open chromatin structure.

Genetic and epigenetic underpinnings of sex differences in the brain and in neurological and psychiatric disease susceptibility

There are numerous examples of sex differences in brain and behavior and in susceptibility to a broad range of brain diseases. For example, gene expression is sexually dimorphic during brain development, adult life, and aging. These differences are orchestrated by the interplay between genetic, hormonal, and environmental influences. However, the molecular mechanisms that underpin these differences have not been fully elucidated. Because recent studies have highlighted the key roles played by epigenetic processes in regulating gene expression and mediating brain form and function, this chapter reviews emerging evidence that shows how epigenetic mechanisms including DNA methylation, histone modifications, and chromatin remodeling, and non-coding RNAs (ncRNAs) are responsible for promoting sexual dimorphism in the brain. Differential profiles of DNA methylation and histone modifications are found in dimorphic brain regions such as the hypothalamus as a result of sex hormone exposure during developmental critical periods. The elaboration of specific epigenetic marks is also linked with regulating sex hormone signaling pathways later in life. Furthermore, the expression and function of epigenetic factors such as the methyl-CpG-binding protein, MeCP2, and the histone-modifying enzymes, UTX and UTY, are sexually dimorphic in the brain. ncRNAs are also implicated in promoting sex differences. For example, X inactivation-specific transcript (XIST) is a long ncRNA that mediates X chromosome inactivation, a seminal developmental process that is particularly important in brain. These observations imply that understanding epigenetic mechanisms, which regulate dimorphic gene expression and function, is necessary for developing a more comprehensive view of sex differences in brain. These emerging findings also suggest that epigenetic mechanisms are, in part, responsible for the differential susceptibility between males and females that is characteristic of a spectrum of neurological and psychiatric disorders.