Epigenetic control of a VDR-governed feed-forward loop that regulates p21(waf1/cip1) expression and function in non-malignant prostate cells

Phytosterol and phytostanol-mediated epigenetic changes in cancer and other non-communicable diseases: a systematic review

Phytosterols/phytostanols are bioactive compounds found in vegetable oils, nuts and seeds and added to a range of commercial food products. Consumption of phytosterols/phytostanols reduces levels of circulating LDL-cholesterol, a causative biomarker of CVD, and is linked to a reduced risk of some cancers. Individuals who consume phytosterols/phytostanols in their diet may do so for many years as part of a non-pharmacological route to lower cholesterol or as part of a healthy diet. However, the impact of long term or high intakes of dietary phytosterols/phytostanols has not been on whole-body epigenetic changes before. The aim of this systematic review was to identify all publications that have evaluated changes to epigenetic mechanisms (post-translation modification of histones, DNA methylation and miRNA expression) in response to phytosterols/phytostanols. A systematic search was performed that returned 226 records, of which eleven were eligible for full-text analysis. Multiple phytosterols were found to inhibit expression of histone deacetylase (HDAC) enzymes and were also predicted to directly bind and impair HDAC activity. Phytosterols were found to inhibit the expression and activity of DNA methyl transferase enzyme 1 and reverse cancer-associated gene silencing. Finally, phytosterols have been shown to regulate over 200 miRNA, although only five of these were reported in multiple publications. Five tissue types (breast, prostate, macrophage, aortic epithelia and lung) were represented across the studies, and although phytosterols/phytostanols alter the molecular mechanisms of epigenetic inheritance in these mammalian cells, studies exploring meiotic or transgenerational inheritance were not found.

Extracellular vesicle-mediated delivery of anti-miR-106b inhibits morphine-induced primary ciliogenesis in the brain

Repeated use of opioids such as morphine causes changes in the shape and signal transduction pathways of various brain cells, including astrocytes and neurons, resulting in alterations in brain functioning and ultimately leading to opioid use disorder. We previously demonstrated that extracellular vesicle (EV)-induced primary ciliogenesis contributes to the development of morphine tolerance. Herein, we aimed to investigate the underlying mechanisms and potential EV-mediated therapeutic approach to inhibit morphine-mediated primary ciliogenesis. We demonstrated that miRNA cargo in morphine-stimulated-astrocyte-derived EVs (morphine-ADEVs) mediated morphine-induced primary ciliogenesis in astrocytes. CEP97 is a target of miR-106b and is a negative regulator of primary ciliogenesis. Intranasal delivery of ADEVs loaded with anti-miR-106b decreased the expression of miR-106b in astrocytes, inhibited primary ciliogenesis, and prevented the development of tolerance in morphine-administered mice. Furthermore, we confirmed primary ciliogenesis in the astrocytes of opioid abusers. miR-106b-5p in morphine-ADEVs induces primary ciliogenesis via targeting CEP97. Intranasal delivery of ADEVs loaded with anti-miR-106b ameliorates morphine-mediated primary ciliogenesis and prevents morphine tolerance. Our findings bring new insights into the mechanisms underlying primary cilium-mediated morphine tolerance and pave the way for developing ADEV-mediated small RNA delivery strategies for preventing substance use disorders.

The role of vitamin D on redox regulation and cellular senescence

Vitamin D is considered an essential micronutrient for human health that is metabolized into a multifunctional secosteroid hormone. We can synthesize it in the skin through ultraviolet B (UVB) rays or acquire it from the diet. Its deficiency is a major global health problem that affects all ages and ethnic groups. Furthermore, dysregulation of vitamin D homeostasis has been associated with premature aging, driven by various cellular processes, including oxidative stress and cellular senescence. Various studies have shown that vitamin D can attenuate oxidative stress and delay cellular senescence, mainly by inducing the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and Klotho and improving mitochondrial homeostasis, proposing this vitamin as an excellent candidate for delaying aging. However, the mechanisms around these processes are not yet fully explored. Therefore, in this review, the effects of vitamin D on redox regulation and cellular senescence are discussed to propose new lines of research and clinical applications of vitamin D in the context of age-related diseases.

A Review: Highlighting the Links between Epigenetics, COVID-19 Infection, and Vitamin D

The highly transmittable and infectious COVID-19 remains a major threat worldwide, with the elderly and comorbid individuals being the most vulnerable. While vaccines are currently available, therapeutic drugs will help ease the viral outbreak and prevent serious health outcomes. Epigenetic modifications regulate gene expression through changes in chromatin structure and have been linked to viral pathophysiology. Since epigenetic modifications contribute to the life cycle of the virus and host immune responses to infection, epigenetic drugs are promising treatment targets to ameliorate COVID-19. Deficiency of the multifunctional secosteroid hormone vitamin D is a global health threat. Vitamin D and its receptor function to regulate genes involved in immunity, apoptosis, proliferation, differentiation, and inflammation. Amassed evidence also indicates the biological relations of vitamin D with reduced disease risk, while its receptor can be modulated by epigenetic mechanisms. The immunomodulatory effects of vitamin D suggest a role for vitamin D as a COVID-19 therapeutic agent. Therefore, this review highlights the epigenetic effects on COVID-19 and vitamin D while also proposing a role for vitamin D in COVID-19 infections.

Vitamin D modulation and microRNAs in gastric cancer: prognostic and therapeutic role

Gastric adenocarcinoma arises after a complex interaction between the host and environmental factors. Tumor location and TNM are the tools that currently guide treatment decisions. Surgery is the only curative treatment, but relapse is common. After relapse or advanced staged disease survival is poor and systemic treatment has modestly improved survival. An association between sun exposure, vitamin D status and gastric cancer (GC) incidence and mortality has been reported. The molecular differences of the histological subtypes and the new molecular classifications account for the great heterogeneity of this disease and are the basis for the discovery of new therapeutic targets. New prognostic and predictive factors are essential and microRNAs (miRNAs) are endogenous small non-coding RNA molecules with a great potential for diagnosis, prognosis and treatment of cancer. There are hundreds of miRNAs with altered expression in tumor gastric tissue when compared to normal gastric tissue. Many of these miRNAs are associated with clinicopathological variables and survival in patients with GC. Furthermore, the expression of some of these miRNAs with prognostic importance in CG is influenced by vitamin D and others are mediators of some of the actions of this vitamin. This review aims to update the evidence on several miRNAs with prognostic value and therapeutic potential in GC, whose expression may be influenced by vitamin D or may regulate vitamin D signaling.

Challenges and Opportunities of Genomic Approaches in Therapeutics Development

The magnitude of all therapeutic responses is significantly determined by genome structure, variation, and functional interactions. This determination occurs at many levels which are discussed in the current review. Well-established examples of structural variation between individuals are known to dictate an individual's response to numerous drugs, as clearly illustrated by warfarin. The exponential rate of genomic-based interrogation is coupled with an expanding repertoire of genomic technologies and applications. This is leading to an ever more sophisticated appreciation of how structural variation, regulation of transcription and genomic structure, both individually and collectively, define cell therapeutic responses.

A novel vitamin D gene therapy for acute myeloid leukemia

Current treatment approaches for older adult patients with acute myeloid leukemia (AML) are often toxic and lack efficacy. Active vitamin D3 (1,25(OH)₂D3) has been shown to induce myeloid blast differentiation but at concentrations that have resulted in unacceptable, off-target hypercalcemia in clinical trials. In our study, we found that the combination of 1,25(OH)₂D3 and the hypomethylating agent (HMA) 5-Azacytidine (AZA) enhanced cytotoxicity and differentiation, and inhibited proliferation of several AML cell lines (MOLM-14, HL60) and primary AML patient samples. This observation was corroborated by our RNA sequence analysis data in which VDR, CD14, and BAX expression were increased, and FLT-3, PIM1 and Bcl-2 expression were decreased. To address the hypercalcemia issue, we genetically engineered MOLM-14 cells to constantly express CYP27B1 (the VD3 activating enzyme, 1-α-hydroxylase-25(OH)D3) through lentiviral transduction procedures. Subsequently, we used these cells as vehicles to deliver the CYP27B1 enzyme to the bone marrow of AML mice. We observed that AML mice with CYP27B1 treatment had longer overall survival compared to no treatment and displayed no significant change in calcium level.

H3K4me3 Is a Potential Mediator for Antiproliferative Effects of Calcitriol (1α,25(OH)2D3) in Ovarian Cancer Biology

Posttranslational histone modification plays an important role in tumorigenesis. Histone modification is a dynamic response of chromatin to various signals, such as the exposure to calcitriol (1α,25(OH)₂D₃). Recent studies suggested that histone modification levels could be used to predict patient outcomes in various cancers. Our study evaluated the expression level of histone 3 lysine 4 trimethylation (H3K4me3) in a cohort of 156 epithelial ovarian cancer (EOC) cases by immunohistochemical staining and analyzed its correlation to patient prognosis. The influence of 1α,25(OH)₂D₃ on the proliferation of ovarian cancer cells was measured by BrdU proliferation assay in vitro. We could show that higher levels of H3K4me3 were correlated with improved overall survival (median overall survival (OS) not reached vs. 37.0 months, p = 0.047) and identified H3K4me3 as a potential prognostic factor for the present cohort. Ovarian cancer cell 1α,25(OH)₂D₃ treatment induced H3K4me3 protein expression and exhibited antiproliferative effects. By this, the study suggests a possible impact of H3K4me3 expression on EOC progression as well as its relation to calcitriol (1α,25(OH)₂D₃) treatment. These results may serve as an explanation on how 1α,25(OH)₂D₃ mediates its known antiproliferative effects. In addition, they further underline the potential benefit of 1α,25(OH)₂D₃ supplementation in context of ovarian cancer care.

The miR-96 and RARγ signaling axis governs androgen signaling and prostate cancer progression

Expression levels of retinoic acid receptor gamma (NR1B3/RARG, encodes RARγ) are commonly reduced in prostate cancer (PCa). Therefore, we sought to establish the cellular and gene regulatory consequences of reduced RARγ expression, and determine RARγ regulatory mechanisms. RARG shRNA approaches in non-malignant (RWPE-1 and HPr1-AR) and malignant (LNCaP) prostate models revealed that reducing RARγ levels, rather than adding exogenous retinoid ligand, had the greatest impact on prostate cell viability and gene expression. ChIP-Seq defined the RARγ cistrome, which was significantly enriched at active enhancers associated with AR binding sites. Reflecting a significant genomic role for RARγ to regulate androgen signaling, RARγ knockdown in HPr1-AR cells significantly regulated the magnitude of the AR transcriptome. RARγ downregulation was explained by increased miR-96 in PCa cell and mouse models, and TCGA PCa cohorts. Biochemical approaches confirmed that miR-96 directly regulated RARγ expression and function. Capture of the miR-96 targetome by biotin-miR-96 identified that RARγ and a number of RARγ interacting co-factors including TACC1 were all targeted by miR-96, and expression of these genes were prominently altered, positively and negatively, in the TCGA-PRAD cohort. Differential gene expression analyses between tumors in the TCGA-PRAD cohort with lower quartile expression levels of RARG and TACC1 and upper quartile miR-96, compared to the reverse, identified a gene network including several RARγ target genes (e.g., SOX15) that significantly associated with worse disease-free survival (hazard ratio 2.23, 95% CI 1.58 to 2.88, p = 0.015). In summary, miR-96 targets a RARγ network to govern AR signaling, PCa progression and disease outcome.

A calcium-sensitive feed-forward loop regulating the expression of the ATP-gated purinergic P2X7 receptor via specificity protein 1 and microRNA-22

Cells have developed complex transcriptional regulatory mechanisms to maintain intracellular homeostasis and withstand pathophysiological stressors. Feed-forward loops comprising transcription factors that drive expression of both target gene and a microRNA as negative regulator, are gaining increasing recognition as key regulatory elements of cellular homeostasis. The ATP-gated purinergic P2X7 receptor (P2X7R) is an important driver of inflammation and has been implicated in the pathogenesis of numerous brain diseases including epilepsy. Changes in P2X7R expression have been reported in both experimental models and in epilepsy patients but the mechanism(s) controlling P2X7R levels remain incompletely understood. The specificity protein 1 (Sp1) has been shown to induce P2X7R transcription in vitro and recent data has identified microRNA-22 as a post-transcriptional repressor of P2X7R expression after seizures. In the present study we show that Sp1 can induce the transcription of both microRNA-22 and P2X7R in vitro during increased neuronal activity and in vivo in a mouse model of status epilepticus. We further show that Sp1-driven microRNA-22 transcription is calcium-sensitive and Sp1 occupancy of the microRNA-22 promoter region is blocked under conditions of seizure activity sufficient to elicit neuronal death. Taken together, our results suggest a neuronal activity-dependent P2X7R expression which is induced by the transcription factor Sp1 and repressed in a calcium-dependent manner by microRNA-22.

Hormone stimulation of androgen receptor mediates dynamic changes in DNA methylation patterns at regulatory elements

DNA methylation is an epigenetic modification that contributes to stable gene silencing by interfering with the ability of transcriptional regulators to bind to DNA. Recent findings have revealed that hormone stimulation of certain nuclear receptors induces rapid, dynamic changes in DNA methylation patterns alongside transcriptional responses at a subset of target loci, over time. However, the ability of androgen receptor (AR) to dynamically regulate gene transcription is relatively under-studied and its role in the regulation of DNA methylation patterns remains to be elucidated. Here we demonstrate in normal prostate cells that hormone stimulated AR activity results in dynamic changes in the transcription rate and DNA methylation patterns at the AR target genes, TIPARP and SGK1. Time-resolved chromatin immunoprecipitation experiments on the SGK1 locus reveals dynamic recruitment of AR and RNA Polymerase II, as well as the recruitment of proteins involved in the DNA demethylation process, TET1 and TDG. Furthermore, the presence of DNA methylation at dynamic regions inhibits protein binding and transcriptional activity of SGK1. These findings establish AR activity as a contributing factor to the dynamic regulation of DNA methylation patterns at target genes in prostate biology and infer further complexity involved in nuclear receptor mediation of transcriptional regulation.

Essential vitamins for an effective T cell response

Effective adaptive immune responses rely upon appropriate activation of T cells by antigenic peptide-major histocompatibility complex on the surface of antigen presenting cells (APCs). Activation relies on additional signals including co-stimulatory molecules on the surface of the APCs that promote T cell expansion. The immune response is further sculpted by the cytokine environment. However, T cells also respond to other environmental signals including hormones, neurotransmitters, and vitamins. In this review, we summarize the mechanisms through which vitamins A and D impact immune responses, particularly in the context of T cell responses.

5-Aza-2′-deoxycytidine enhances the antimicrobial response of vitamin D receptor against Mycobacterium tuberculosis

Objective: Epigenetic modification affects disease susceptibility.

Pan-cancer analyses of the nuclear receptor superfamily

Nuclear receptors (NR) act as an integrated conduit for environmental and hormonal signals to govern genomic responses, which relate to cell fate decisions. We review how their integrated actions with each other, shared co-factors and other transcription factors are disrupted in cancer. Steroid hormone nuclear receptors are oncogenic drivers in breast and prostate cancer and blockade of signaling is a major therapeutic goal. By contrast to blockade of receptors, in other cancers enhanced receptor function is attractive, as illustrated initially with targeting of retinoic acid receptors in leukemia. In the post-genomic era large consortia, such as The Cancer Genome Atlas, have developed a remarkable volume of genomic data with which to examine multiple aspects of nuclear receptor status in a pan-cancer manner. Therefore to extend the review of NR function we have also undertaken bioinformatics analyses of NR expression in over 3000 tumors, spread across six different tumor types (bladder, breast, colon, head and neck, liver and prostate). Specifically, to ask how the NR expression was distorted (altered expression, mutation and CNV) we have applied bootstrapping approaches to simulate data for comparison, and also compared these NR findings to 12 other transcription factor families. Nuclear receptors were uniquely and uniformly downregulated across all six tumor types, more than predicted by chance. These approaches also revealed that each tumor type had a specific NR expression profile but these were most similar between breast and prostate cancer. Some NRs were down-regulated in at least five tumor types (e.g. NR3C2/MR and NR5A2/LRH-1)) whereas others were uniquely down-regulated in one tumor (e.g. NR1B3/RARG). The downregulation was not driven by copy number variation or mutation and epigenetic mechanisms maybe responsible for the altered nuclear receptor expression.

Vitamin D in Prostate Cancer

Metastatic castration-resistant prostate cancer (mCRPC) is a progressive, noncurable disease induced by androgen receptor (AR) upon its activation by tumor tissue androgen, which is generated from adrenal steroid dehydroepiandrosterone (DHEA) through intracrine androgen biosynthesis. Inhibition of mCRPC and early-stage, androgen-dependent prostate cancer by calcitriol, the bioactive vitamin D3 metabolite, is amply documented in cell culture and animal studies. However, clinical trials of calcitriol or synthetic analogs are inconclusive, although encouraging results have recently emerged from pilot studies showing efficacy of a safe-dose vitamin D3 supplementation in reducing tumor tissue inflammation and progression of low-grade prostate cancer. Vitamin D-mediated inhibition of normal and malignant prostate cells is caused by diverse mechanisms including G1/S cell cycle arrest, apoptosis, prodifferentiation gene expression changes, and suppressed angiogenesis and cell migration. Biological effects of vitamin D are mediated by altered expression of a gene network regulated by the vitamin D receptor (VDR), which is a multidomain, ligand-inducible transcription factor similar to AR and other nuclear receptors. AR-VDR cross talk modulates androgen metabolism in prostate cancer cells. Androgen inhibits vitamin D-mediated induction of CYP24A1, the calcitriol-degrading enzyme, while vitamin D promotes androgen inactivation by inducing phase I monooxygenases (e.g., CYP3A4) and phase II transferases (e.g., SULT2B1b, a DHEA-sulfotransferase). CYP3A4 and SULT2B1b levels are markedly reduced and CYP24A1 is overexpressed in advanced prostate cancer. In future trials, combining low-calcemic, potent next-generation calcitriol analogs with CYP24A1 inhibition or androgen supplementation, or cancer stem cell suppression by a phytonutrient such as sulfarophane, may prove fruitful in prostate cancer prevention and treatment.

Mechanistic Effects of Calcitriol in Cancer Biology

Besides its classical biological effects on calcium and phosphorus homeostasis, calcitriol, the active vitamin D metabolite, has a broad variety of actions including anticancer effects that are mediated either transcriptionally and/or via non-genomic pathways. In the context of cancer, calcitriol regulates the cell cycle, induces apoptosis, promotes cell differentiation and acts as anti-inflammatory factor within the tumor microenvironment. In this review, we address the different mechanisms of action involved in the antineoplastic effects of calcitriol.

Inflammation and Nutritional Science for Programs/Policies and Interpretation of Research Evidence (INSPIRE)

An increasing recognition has emerged of the complexities of the global health agenda—specifically, the collision of infections and noncommunicable diseases and the dual burden of over- and undernutrition. Of particular practical concern are both 1) the need for a better understanding of the bidirectional relations between nutritional status and the development and function of the immune and inflammatory response and 2) the specific impact of the inflammatory response on the selection, use, and interpretation of nutrient biomarkers. The goal of the Inflammation and Nutritional Science for Programs/Policies and Interpretation of Research Evidence (INSPIRE) is to provide guidance for those users represented by the global food and nutrition enterprise. These include researchers (bench and clinical), clinicians providing care/treatment, those developing and evaluating programs/interventions at scale, and those responsible for generating evidence-based policy. The INSPIRE process included convening 5 thematic working groups (WGs) charged with developing summary reports around the following issues: 1) basic overview of the interactions between nutrition, immune function, and the inflammatory response; 2) examination of the evidence regarding the impact of nutrition on immune function and inflammation; 3) evaluation of the impact of inflammation and clinical conditions (acute and chronic) on nutrition; 4) examination of existing and potential new approaches to account for the impact of inflammation on biomarker interpretation and use; and 5) the presentation of new approaches to the study of these relations. Each WG was tasked with synthesizing a summary of the evidence for each of these topics and delineating the remaining gaps in our knowledge. This review consists of a summary of the INSPIRE workshop and the WG deliberations.

Vitamin D receptor and RXR in the post-genomic era

Following the elucidation of the human genome and components of the epigenome, it is timely to revisit what is known of vitamin D receptor (VDR) function. Early transcriptomic studies using microarray approaches focused on the protein coding mRNA that were regulated by the VDR, usually following treatment with ligand. These studies quickly established the approximate size and surprising diversity of the VDR transcriptome, revealing it to be highly heterogenous and cell type and time dependent. Investigators also considered VDR regulation of non-protein coding RNA and again, cell and time dependency was observed. Attempts to integrate mRNA and miRNA regulation patterns are beginning to reveal patterns of co-regulation and interaction that allow for greater control of mRNA expression, and the capacity to govern more complex cellular events. Alternative splicing in the trasncriptome has emerged as a critical process in transcriptional control and there is evidence of the VDR interacting with components of the splicesome. ChIP-Seq approaches have proved to be pivotal to reveal the diversity of the VDR binding choices across cell types and following treatment, and have revealed that the majority of these are non-canonical in nature. The underlying causes driving the diversity of VDR binding choices remain enigmatic. Finally, genetic variation has emerged as important to impact the transcription factor affinity towards genomic binding sites, and recently the impact of this on VDR function has begun to be considered.

Vitamin D in cancer chemoprevention

CONTEXT

There is increasing evidence that Vitamin D (Vit D) and its metabolites, besides their well-known calcium-related functions, may also exert antiproliferative, pro-differentiating, and immune modulatory effects on tumor cells in vitro and may also delay tumor growth in vivo.

OBJECTIVE

The aim of this review is to provide fresh insight into the most recent advances on the role of Vit D and its analogues as chemopreventive drugs in cancer therapy.

METHODS

A systematic review of experimental and clinical studies on Vit D and cancer was undertaken by using the major electronic health database including ISI Web of Science, Medline, PubMed, Scopus and Google Scholar.

RESULTS AND CONCLUSION

Experimental and clinical observations suggest that Vit D and its analogues may be effective in preventing the malignant transformation and/or the progression of various types of human tumors including breast cancer, prostate cancer, colorectal cancer, and some hematological malignances. These findings suggest the possibility of the clinical use of these molecules as novel potential chemopreventive and anticancer agents.

1α,25(OH)2D3 differentially regulates miRNA expression in human bladder cancer cells

Bladder cancer is the fourth most commonly diagnosed cancer in men and eighth leading cause of cancer-related death in the US. Epidemiological and experimental studies strongly suggest a role for 1α,25(OH)2D3 in cancer prevention and treatment. The antitumor activities of 1α,25(OH)2D3 are mediated by the induction of cell cycle arrest, apoptosis, differentiation and the inhibition of angiogenesis and metastasis. miRNAs play important regulatory roles in cancer development and progression. However, the role of 1α,25(OH)2D3 in the regulation of miRNA expression and the potential impact in bladder cancer has not been investigated. Therefore, we studied 1α,25(OH)2D3-regulated miRNA expression profiles in human bladder cancer cell line 253J and the highly tumorigenic and metastatic derivative line 253J-BV by miRNA qPCR panels. 253J and 253J-BV cells express endogenous vitamin D receptor (VDR), which can be further induced by 1α,25(OH)2D3. VDR target gene 24-hydroxylase was induced by 1α,25(OH)2D3 in both cell lines, indicating functional 1α,25(OH)2D3 signaling. The miRNA qPCR panel assay results showed that 253J and 253J-BV cells have distinct miRNA expression profiles. Further, 1α,25(OH)2D3 differentially regulated miRNA expression profiles in 253J and 253J-BV cells in a dynamic manner. Pathway analysis of the miRNA target genes revealed distinct patterns of contribution to the molecular functions and biological processes in the two cell lines. In conclusion, 1α,25(OH)2D3 differentially regulates the expression of miRNAs, which may contribute to distinct biological functions, in human bladder 253J and 253J-BV cells. This article is part of a Special Issue entitled '17th Vitamin D Workshop'.

VDR regulation of microRNA differs across prostate cell models suggesting extremely flexible control of transcription

The Vitamin D Receptor (VDR) is a member of the nuclear receptor superfamily and is of therapeutic interest in cancer and other settings. Regulation of microRNA (miRNA) by the VDR appears to be important to mediate its actions, for example, to control cell growth. To identify if and to what extent VDR-regulated miRNA patterns change in prostate cancer progression, we undertook miRNA microarray analyses in 7 cell models representing non-malignant and malignant prostate cells (RWPE-1, RWPE-2, HPr1, HPr1AR, LNCaP, LNCaP-C4-2, and PC-3). To focus on primary VDR regulatory events, we undertook expression analyses after 30 minutes treatment with 1α,25(OH)2D3. Across all models, 111 miRNAs were significantly modulated by 1α,25(OH)2D3 treatment. Of these, only 5 miRNAs were modulated in more than one cell model, and of these, only 3 miRNAs were modulated in the same direction. The patterns of miRNA regulation, and the networks they targeted, significantly distinguished the different cell types. Integration of 1α,25(OH)2D3-regulated miRNAs with published VDR ChIP-seq data showed significant enrichment of VDR peaks in flanking regions of miRNAs. Furthermore, mRNA and miRNA expression analyses in non-malignant RWPE-1 cells revealed patterns of miRNA and mRNA co-regulation; specifically, 13 significant reciprocal patterns were identified and these patterns were also observed in TCGA prostate cancer data. Lastly, motif search analysis revealed differential motif enrichment within VDR peaks flanking mRNA compared to miRNA genes. Together, this study revealed that miRNAs are rapidly regulated in a highly cell-type specific manner, and are significantly co-integrated with mRNA regulation.

Serum microRNA expression patterns that predict early treatment failure in prostate cancer patients

We aimed to identify microRNA (miRNA) expression patterns in the serum of prostate cancer (CaP) patients that predict the risk of early treatment failure following radical prostatectomy (RP). Microarray and Q-RT-PCR analyses identified 43 miRNAs as differentiating disease stages within 14 prostate cell lines and reflectedpublically available patient data. 34 of these miRNA were detectable in the serum of CaP patients. Association with time to biochemical progression was examined in a cohort of CaP patients following RP. A greater than two-fold increase in hazard of biochemical progression associated with altered expression of miR-103, miR-125b and miR-222 (p <.0008) in the serum of CaP patients. Prediction models based on penalized regression analyses showed that the levels of the miRNAs and PSA together were better at detecting false positives than models without miRNAs, for similar level of sensitivity. Analyses of publically available data revealed significant and reciprocal relationships between changes in CpG methylation and miRNA expression patterns suggesting a role for CpG methylation to regulate miRNA. Exploratory validation supported roles for miR-222 and miR-125b to predict progression risk in CaP. The current study established that expression patterns of serum-detectable miRNAs taken at the time of RP are prognostic for men who are at risk of experiencing subsequent early biochemical progression. These non-invasive approaches could be used to augment treatment decisions.

Nuclear receptors and the Warburg effect in cancer

In 1927 Otto Warburg established that tumours derive energy primarily from the conversion of glucose to lactic acid and only partially through cellular respiration involving oxygen. In the 1950s he proposed that all causes of cancer reflected different mechanisms of disabling cellular respiration in favour of fermentation (now termed aerobic glycolysis). The role of aberrant glucose metabolism in cancer is now firmly established. The shift away from oxidative phosphorylation towards the metabolically expensive aerobic glycolysis is somewhat counter-intuitive given its wasteful nature. Multiple control processes are in place to maintain cellular efficiency and it is likely that these mechanisms are disrupted to facilitate the shift to the reliance on aerobic glycolysis. One such process of cell control is mediated by the nuclear receptor superfamily. This large family of transcription factors plays a significant role in sensing environmental cues and controlling decisions on proliferation, differentiation and cell death for example, to regulate glucose uptake and metabolism and to modulate the actions of oncogenes and tumour suppressors. In this review we highlight mechanisms by which nuclear receptors actions are altered during tumorigenic transformation and can serve to enhance the shift to aerobic glycolysis. At the simplest level, a basic alteration in NR behaviour can serve to enhance glycolytic flux thus providing a basis for enhanced survival within the tumour micro-environment. Ameliorating the enhanced NR activity in this context may help to sensitize cancer cells to Warburg targeted therapies and may provide future drug targets.

Vitamin D, intermediary metabolism and prostate cancer tumor progression

Epidemiological data have demonstrated an inverse association between serum vitamin D3 levels, cancer incidence and related mortality. However, the effects of vitamin D on prostate cancer biology and its utility for prevention of prostate cancer progression are not as well-defined. The data are often conflicting: some reports suggest that vitamin D3 induces apoptosis in androgen dependent prostate cancer cell lines, while others suggest that vitamin D3 only induces cell cycle arrest. Recent molecular studies have identified an extensive synergistic crosstalk between the vitamin D- and androgen-mediated mRNA and miRNA expression, adding an additional layer of post-transcriptional regulation to the known VDR- and AR-regulated gene activation. The Warburg effect, the inefficient metabolic pathway that converts glucose to lactate for rapid energy generation, is a phenomenon common to many different types of cancer. This process supports cell proliferation and promotes cancer progression via alteration of glucose, glutamine and lipid metabolism. Prostate cancer is a notable exception to this general process since the metabolic switch that occurs early during malignancy is the reverse of the Warburg effect. This "anti-Warburg effect" is due to the unique biology of normal prostate cells that harbor a truncated TCA cycle that is required to produce and secret citrate. In prostate cancer cells, the TCA cycle activity is restored and citrate oxidation is used to produce energy for cancer cell proliferation. 1,25(OH)2D3 and androgen together modulates the TCA cycle via transcriptional regulation of zinc transporters, suggesting that 1,25(OH)2D3 and androgen maintain normal prostate metabolism by blocking citrate oxidation. These data demonstrate the importance of androgens in the anti-proliferative effect of vitamin D in prostate cancer and highlight the importance of understanding the crosstalk between these two signaling pathways.

Vitamin D and the RNA transcriptome: more than mRNA regulation

The GRCh37.p13 primary assembly of the human genome contains 20805 protein coding mRNA, and 37147 non-protein coding genes and pseudogenes that as a result of RNA processing and editing generate 196501 gene transcripts. Given the size and diversity of the human transcriptome, it is timely to revisit what is known of VDR function in the regulation and targeting of transcription. Early transcriptomic studies using microarray approaches focused on the protein coding mRNA that were regulated by the VDR, usually following treatment with ligand. These studies quickly established the approximate size, and surprising diversity of the VDR transcriptome, revealing it to be highly heterogenous and cell type and time dependent. With the discovery of microRNA, investigators also considered VDR regulation of these non-protein coding RNA. Again, cell and time dependency has emerged. Attempts to integrate mRNA and miRNA regulation patterns are beginning to reveal patterns of co-regulation and interaction that allow for greater control of mRNA expression, and the capacity to govern more complex cellular events. As the awareness of the diversity of non-coding RNA increases, it is increasingly likely it will be revealed that VDR actions are mediated through these molecules also. Key knowledge gaps remain over the VDR transcriptome. The causes for the cell and type dependent transcriptional heterogenetiy remain enigmatic. ChIP-Seq approaches have confirmed that VDR binding choices differ very significantly by cell type, but as yet the underlying causes distilling VDR binding choices are unclear. Similarly, it is clear that many of the VDR binding sites are non-canonical in nature but again the mechanisms underlying these interactions are unclear. Finally, although alternative splicing is clearly a very significant process in cellular transcriptional control, the lack of RNA-Seq data centered on VDR function are currently limiting the global assessment of the VDR transcriptome. VDR focused research that complements publically available data (e.g., ENCODE Birney et al., 2007; Birney, 2012), TCGA (Strausberg et al., 2002), GTEx (Consortium, 2013) will enable these questions to be addressed through large-scale data integration efforts.

Inhibition of Methicillin-resistant Staphylococcus aureus-induced cytokines mRNA production in human bone marrow derived mesenchymal stem cells by 1,25-dihydroxyvitamin D3

Background

Methicillin-resistant Staphylococcus aureus (MRSA) is the predominant cause of bone infection. Toll like receptors (TLRs) are an important segments of host response to infection and are expressed by a variety of cells including human mesenchymal stem cells (hMSCs). The active form of Vitamin D, 1,25-dihydroxyvitamin D3 (1,25(OH)₂D₃) has potent immunoregulatory properties, but the mechanism remains poorly understood. The genomic action of 1,25(OH)₂D₃ is mediated by vitamin D receptor (VDR), hormone-regulated transcription factor. VDR interacts with co-activators and co-repressors are associated with chromatin histone modifications and transcriptional regulation. The aim of our study is to explore MRSA-induced TLRs-mediated pro-inflammatory cytokines expression in hMSCs. Further, we hypothesized that 1,25(OH)₂D₃ inhibits MRSA-induced cytokines synthesis in hMSCs via inhibition of NF-кB transcription factor. Finally, we explored the regulatory role of 1,25(OH)₂D₃ in MRSA-mediated global epigenetic histone H3 mark, such as, trimethylated histone H3 lysine 9 (H3K9me3), which is linked to gene silencing.

Results

Quantitative PCR data revealed that MRSA-infection predominantly induced expression of TLRs 1, 2, 6, NR4A2, and inflammatory cytokines IL-8, IL-6, TNFα in hMSCs. MRSA-mediated TLR ligands reduced osteoblast differentiation and increased hMSCs proliferation, indicating the disrupted multipotency function of hMSCs. Pretreatment of 1,25(OH)₂D₃ followed by MRSA co-culture inhibited nuclear translocation of NF-кB-p65, reduced expression of NR4A2 and pro-inflammatory cytokines IL-8, IL-6, and TNFα in hMSCs. Further, NF-κB-p65, VDR, and NR4A2 were present in the same nuclear protein complex, indicating that VDR is an active part of the nuclear protein complexes for transcriptional regulation. Finally, 1,25(OH)₂D₃ activated VDR, restores the global level of H3K9me3, to repress MRSA-stimulated inflammatory cytokine IL-8 expression. Pretreatment of 5-dAZA, DNA methylatransferases (Dnmts) inhibitor, dramatically re-expresses 1,25(OH)₂D₃-MRSA-mediated silenced IL-8 gene.

Conclusions

This data indicates that TLR 1, 2, and 6 can be used as markers for localized S. aureus bone infection. 1,25(OH)₂D₃-VDR may exhibits its anti-inflammatory properties in MRSA-stimulated infection by inhibiting nuclear translocation of NF-kB-p65 and transcripts of IL-8, IL-6, TNFα, and NR4A2 in hMSCs. Finally, 1,25(OH)₂D₃-activated VDR, acting as an epigenetic regulator, inhibits synthesis of cytokines in MRSA-stimulated infection by restoring the global level of H3K9me3, a histone H3 mark for gene silencing.

Interaction of vitamin D with membrane-based signaling pathways

Many studies in different biological systems have revealed that 1α,25-dihydroxyvitamin D₃ (1α,25(OH)₂D₃) modulates signaling pathways triggered at the plasma membrane by agents such as Wnt, transforming growth factor (TGF)-β, epidermal growth factor (EGF), and others. In addition, 1α,25(OH)₂D₃ may affect gene expression by paracrine mechanisms that involve the regulation of cytokine or growth factor secretion by neighboring cells. Moreover, post-transcriptional and post-translational effects of 1α,25(OH)₂D₃ add to or overlap with its classical modulation of gene transcription rate. Together, these findings show that vitamin D receptor (VDR) cannot be considered only as a nuclear-acting, ligand-modulated transcription factor that binds to and controls the transcription of target genes. Instead, available data support the view that much of the complex biological activity of 1α,25(OH)₂D₃ resides in its capacity to interact with membrane-based signaling pathways and to modulate the expression and secretion of paracrine factors. Therefore, we propose that future research in the vitamin D field should focus on the interplay between 1α,25(OH)₂D₃ and agents that act at the plasma membrane, and on the analysis of intercellular communication. Global analyses such as RNA-Seq, transcriptomic arrays, and genome-wide ChIP are expected to dissect the interactions at the gene and molecular levels.

Gene regulatory scenarios of primary 1,25-dihydroxyvitamin d3 target genes in a human myeloid leukemia cell line

Genome- and transcriptome-wide data has significantly increased the amount of available information about primary 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) target genes in cancer cell models, such as human THP-1 myelomonocytic leukemia cells. In this study, we investigated the genes G0S2, CDKN1A and MYC as master examples of primary vitamin D receptor (VDR) targets being involved in the control of cellular proliferation. The chromosomal domains of G0S2 and CDKN1A are 140-170 kb in size and contain one and three VDR binding sites, respectively. This is rather compact compared to the MYC locus that is 15 times larger and accommodates four VDR binding sites. All eight VDR binding sites were studied by chromatin immunoprecipitation in THP-1 cells. Interestingly, the site closest to the transcription start site of the down-regulated MYC gene showed 1,25(OH)2D3-dependent reduction of VDR binding and is not associated with open chromatin. Four of the other seven VDR binding regions contain a typical DR3-type VDR binding sequence, three of which are also occupied with VDR in macrophage-like cells. In conclusion, the three examples suggest that each VDR target gene has an individual regulatory scenario. However, some general components of these scenarios may be useful for the development of new therapy regimens.

Integrated analysis of miRNA and mRNA during differentiation of human CD34+ cells delineates the regulatory roles of microRNA in hematopoiesis

In the process of human hematopoiesis, precise regulation of the expression of lineage-specific gene products is critical for multiple cell-fate decisions that govern cell differentiation, proliferation, and self-renewal. Given the important role of microRNAs (miRNAs) in development and differentiation, we examined the global expression of miRNA in CD34(+) cells during lineage specific hematopoiesis and found 49 miRNAs to be differentially expressed, with functional roles in cellular growth and proliferation, and apoptosis. miR-18a was upregulated during erythropoiesis and downregulated during megakaryopoiesis. miR-145 was upregulated during granulopoiesis and down regulated during erythropoiesis. Megakaryopoitic differentiation resulted in significant alteration in the expression of many miRNAs that are believed to play critical roles in the regulation of B and T cell differentiation. Target prediction analyses on three different miRNA databases indicated that TargetScan outperformed microCosm and miRDB in identifying potential miRNA targets associated with hematopoietic differentiation process. An integrated analysis of the observed miRNAs and messenger RNAs (mRNAs) resulted in 87 highly correlated miRNA-mRNA pairs that have major functional roles in cellular growth and proliferation, hematopoietic system development, and Wnt/B-catenin and Flt 3 signaling pathways. We believe that this study will enhance our understanding on the regulatory roles of miRNA in hematopoiesis by providing a library of mRNA-miRNA networks.

Cooperative behavior of the nuclear receptor superfamily and its deregulation in prostate cancer

The current study aimed to assess the topology of the nuclear receptor (NR) superfamily in normal prostate epithelial cells and its distortion in prostate cancer. Both in vitro and in silico approaches were utilized to profile NRs expressed in non-malignant RWPE-1 cells, which were subsequently investigated by treating cells with 132 binary NR ligand combinations. Nine significant cooperative interactions emerged including both superadditive [22(R)-hydroxycholesterol and eicosatetraenoic acid] and subadditive [1α,25(OH)2D3 and chenodeoxycholic acid] cellular responses, which could be explained in part by cooperative control of cell-cycle progression and candidate gene expression. In addition, publicly available data were employed to assess NR expression in human prostate tissue. Common and significant loss of NR superfamily expression was established in publicly available data from prostate tumors, in part predicting parallel distortion of targeting microRNA. These findings suggest that the NR superfamily in the prostate cooperatively integrates signals from dietary, hormonal and metabolic cues, and is significantly distorted in prostate cancer.

The Interactions of microRNA and Epigenetic Modifications in Prostate Cancer

Epigenetic modifiers play important roles in fine-tuning the cellular transcriptome. Any imbalance in these processes may lead to abnormal transcriptional activity and thus result in disease state. Distortions of the epigenome have been reported in cancer initiation and progression. DNA methylation and histone modifications are principle components of this epigenome, but more recently it has become clear that microRNAs (miRNAs) are another major component of the epigenome. Interactions of these components are apparent in prostate cancer (CaP), which is the most common non-cutaneous cancer and second leading cause of death from cancer in the USA. Changes in DNA methylation, altered histone modifications and miRNA expression are functionally associated with CaP initiation and progression. Various aspects of the epigenome have also been investigated as biomarkers for different stages of CaP detection, though with limited success. This review aims to summarize key aspects of these mechanistic interactions within the epigenome and to highlight their translational potential as functional biomarkers. To this end, exploration of TCGA prostate cancer data revealed that expression of key CaP miRNAs inversely associate with DNA methylation. Given the importance and prevalence of these epigenetic events in CaP biology it is timely to understand further how different epigenetic components interact and influence each other.

1,25-Dihydroxyvitamin D3 modulates lipid metabolism in prostate cancer cells through miRNA mediated regulation of PPARA

Previous studies from our laboratory have shown that testosterone (T) and 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) co-operate to inhibit cell proliferation and induce significant changes in gene expression and differentiation in LNCaP cells. The data presented here demonstrate that the two agents alter fatty acid metabolism, and accumulation of neutral lipid. Concurrent genome wide analysis of mRNA and miRNA in LNCaP cells reveals an extensive transcription regulatory network modulated by T and 1,25(OH)2D3. This involves not only androgen receptor (AR)- and vitamin D receptor (VDR)-mediated transcription, but also transcription factors E2F1- and c-Myc-dependent transcription. Changes in the activities of these transcription factors alter the steady state levels of several miRNAs, including the miR-17/92 cluster. These changes correlate with the up-regulation of the mRNA encoding peroxisome proliferator-activated receptor alpha (PPARA) and its downstream targets, leading to increased lipogenesis. These data suggest that the coordinated effect of T and 1,25(OH)2D3 in prostate cancer cells increases lipogenesis, diverting energy away from Warburg-based tumor energy metabolism, which slows or halts cell growth and tumor progression. This article is part of a Special Issue entitled 'Vitamin D Workshop'.

The sum of many small changes: microRNAs are specifically and potentially globally altered by vitamin D3 metabolites

Vitamin D3 deficiency is rampant which may contribute to increased risk of many diseases including cancer, cardiovascular disease and autoimmune disorders. Genomic activity of the active metabolite 1,25-dihydroxyvitamin D (1,25D) mediates most vitamin D3's actions and many gene targets of 1,25D have been characterized. As the importance of non-coding RNAs has emerged, the ability of vitamin D3via 1,25D to regulate microRNAs (miRNAs) has been demonstrated in several cancer cell lines, patient tissue and sera. In vitamin D3 intervention patient trials, significant differences in miRNAs are observed between treatment groups and/or between baseline and followup. In patient sera from population studies, specific miRNA differences associate with serum levels of 25D. The findings thus far indicate that dietary vitamin D3 in patients and 1,25D in vitro not only regulate specific miRNA(s), but may also globally upregulate miRNA levels. This article is part of a Special Issue entitled 'Vitamin D Workshop'.

Epigenetic distortion to VDR transcriptional regulation in prostate cancer cells

The current study aimed to examine the gene specific mechanisms by which the actions of the vitamin D receptor (VDR) are distorted in prostate cancer. Transcriptional responses toward the VDR ligand, 1α,25(OH)2D3, were examined in non-malignant prostate epithelial cells (RWPE-1) and compared to the 1α,25(OH)2D3-recalcitrant prostate cancer cells (PC-3). Time resolved transcriptional studies for two VDR target genes revealed selective attenuation and repression of VDR transcriptional responses in PC-3 cells. For example, responses in PC-3 cells revealed suppressed responsiveness of IGFBP3 and G0S2. Furthermore, Chromatin Immunoprecipitation (ChIP) assays revealed that suppressed transcriptional responses in PC-3 cells of IGFBP3 and G0S2 were associated with selective VDR-induced NCOR1 enrichment at VDR-binding regions on target-gene promoter regions. We propose that VDR inappropriately recruits co-repressors in prostate cancer cells. Subsequent direct and indirect mechanisms may induce local DNA methylation and stable transcriptional silencing. Thus a transient epigenetic process mediated by co-repressor binding, namely, the control of H3K9 acetylation, is distorted to favor a more stable epigenetic event, namely DNA methylation. This article is part of a Special Issue entitled 'Vitamin D Workshop'.

Vitamin D receptor signaling mechanisms: integrated actions of a well-defined transcription factor

The main physiological actions of the biologically most active metabolite of vitamin D, 1α,25-dihydroxyvitamin D(3) (1α,25(OH)(2)D(3)), are calcium and phosphorus uptake and transport and thereby controlling bone formation. Other emergent areas of 1α,25(OH)(2)D(3) action are in the control of immune functions, cellular growth and differentiation. All genomic actions of 1α,25(OH)(2)D(3) are mediated by the transcription factor vitamin D receptor (VDR) that has been the subject of intense study since the 1980's. Thus, vitamin D signaling primarily implies the molecular actions of the VDR. In this review, we present different perspectives on the VDR that incorporate its role as transcription factor and member of the nuclear receptor superfamily, its dynamic changes in genome-wide locations and DNA binding modes, its interaction with chromatin components and its primary protein-coding and non-protein coding target genes and finally how these aspects are united in regulatory networks. By comparing the actions of the VDR, a relatively well-understood and characterized protein, with those of other transcription factors, we aim to build a realistic positioning of vitamin D signaling in the context of other intracellular signaling systems.

Recruitment of NCOR1 to VDR target genes is enhanced in prostate cancer cells and associates with altered DNA methylation patterns

The current study investigated transcriptional distortion in prostate cancer cells using the vitamin D receptor (VDR) as a tool to examine how epigenetic events driven by corepressor binding and CpG methylation lead to aberrant gene expression. These relationships were investigated in the non-malignant RWPE-1 cells that were 1α,25(OH)(2)D(3) responsive (RWPE-1) and malignant cell lines that were 1α,25(OH)(2)D(3) partially responsive (RWPE-2) and resistant (PC-3). These studies revealed that selective attenuation and repression of VDR transcriptional responses in the cancer cell lines reflected their loss of antiproliferative sensitivity. This was evident in VDR target genes including VDR, CDKN1A (encodes p21( (waf1/cip1) )) and GADD45A; NCOR1 knockdown alleviated this malignant transrepression. ChIP assays in RWPE-1 and PC-3 cells revealed that transrepression of CDKN1A was associated with increased NCOR1 enrichment in response to 1α,25(OH)(2)D(3) treatment. These findings supported the concept that retained and increased NCOR1 binding, associated with loss of H3K9ac and increased H3K9me2, may act as a beacon for the initiation and recruitment of DNA methylation. Overexpressed histone methyltransferases (KMTs) were detectable in a wide panel of prostate cancer cell lines compared with RWPE-1 and suggested that generation of H3K9me2 states would be favored. Cotreatment of cells with the KMT inhibitor, chaetocin, increased 1α,25(OH)(2)D(3)-mediated induction of CDKN1A expression supporting a role for this event to disrupt CDKN1A regulation. Parallel surveys in PC-3 cells of CpG methylation around the VDR binding regions on CDKN1A revealed altered basal and VDR-regulated DNA methylation patterns that overlapped with VDR-induced recruitment of NCOR1 and gene transrepression. Taken together, these findings suggest that sustained corepressor interactions with nuclear-resident transcription factors may inappropriately transform transient-repressive histone states into more stable and repressive DNA methylation events.

Mitochondrial translocation of vitamin D receptor is mediated by the permeability transition pore in human keratinocyte cell line

Background

Vitamin D receptor (VDR) is a well known transcriptional regulator, active as heterodimer in association with coactivators and corepressors. In addition it has been described the extranuclear distribution of the receptor and in particular the recently reported mitochondrial localization in platelets and megakaryocytes is intriguing because it appears to be a common feature of steroid receptors. Whereas for other members of the steroid receptor family the mitochondrial function has been explored, up to now nothing is known about a mitochondrial form of VDR in human proliferating cells.

Methodology/Principal Findings

In this study we characterized for the first time the mitochondrial localization of VDR in the human keratinocyte cell line HaCaT. In proliferating HaCaT cells VDR was abundantly expressed in mitochondria in association with its binding partner RXRα and the import was ligand-independent. By immunoprecipitation studies we demonstrated the interaction of VDR with proteins of the permeability transition pore (PTP), VDAC and StAR. We then adopted different pharmacological and silencing approaches with the aim of hampering PTP function, either affecting PTP opening or abating the expression of the complex member StAR. By all means the impairment of pore function led to a reduction of mitochondrial levels of VDR.

Conclusions

The results reported here demonstrate a ligand-independent mitochondrial import of VDR through the permeability transition pore, and open interesting new perspectives on PTP function as transporter and on VDR role in mitochondria.

Vitamin D and colon cancer

The most active vitamin D metabolite, 1α,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)), is a pleiotropic hormone with wide regulatory actions. Classically, vitamin D deficiency was known to alter calcium and phosphate metabolism and bone biology. In addition, recent epidemiological and experimental studies support the association of vitamin D deficiency with a large variety of human diseases, and particularly with the high risk of colorectal cancer. By regulating the expression of many genes via several mechanisms, 1,25(OH)(2)D(3) induces differentiation, controls the detoxification metabolism and cell phenotype, sensitises cells to apoptosis and inhibits the proliferation of cultured human colon carcinoma cells. Consistently, 1,25(OH)(2)D(3) and several of its analogues decrease intestinal tumourigenesis in animal models. Molecular, genetic and clinical data in humans are scarce but they suggest that vitamin D is protective against colon cancer. Clearly, the available evidence warrants new, well-designed, large-scale trials to clarify the role of vitamin D in the prevention and/or therapy of this important neoplasia.

Vitamin D has wide regulatory effects on histone demethylase genes

Vitamin D from the diet or synthesized in the skin upon UV-B irradiation is converted in the organism into the active metabolite 1α,25- dihydroxyvitamin D 3 [1,25(OH) 2D 3, calcitriol], a pleiotropic hormone with wide regulatory actions. The classical model of 1,25(OH)2D3 action implies the activation of the vitamin D receptor, which binds specific DNA sequences in its target genes and modulates their transcription rate. We have recently shown that 1,25(OH) 2D 3 induces the expression of the JMJD3 gene coding for a histone demethylase that is involved in epigenetic regulation. JMJD3 mediates the effects of 1,25(OH) 2D 3 on a subset of target genes and affects the expression of ZEB1, ZEB2 and SNAI1, inducers of epithelial-mesenchymal transition. Novel data indicate that 1,25(OH) 2D 3 has an unanticipated wide regulatory action on the expression of genes coding for histone demethylases of the Jumonji C (JmjC) domain and lysine-specific demethylase (LSD) families. Moreover, JMJD3 knockdown decreases the expression of miR‑200b and miR‑200c, two microRNAs targeting ZEB1 RNA. This may explain the upregulation of this transcription factor found in JMJD3-depleted cells. Thus, 1,25(OH) 2D 3 exerts an ample regulatory effect on the expression of histone-modifying enzymes involved in epigenetic regulation that may mediate its actions on gene transcription and cell phenotype.

Vitamin D and cancer: a review of molecular mechanisms

The population-based association between low vitamin D status and increased cancer risk can be inconsistent, but it is now generally accepted. These relationships link low serum 25OHD (25-hydroxyvitamin D) levels to cancer, whereas cell-based studies show that the metabolite 1,25(OH)2D (1,25-dihydroxyvitamin D) is a biologically active metabolite that works through vitamin D receptor to regulate gene transcription. In the present review we discuss the literature relevant to the molecular events that may account for the beneficial impact of vitamin D on cancer prevention or treatment. These data show that although vitamin D-induced growth arrest and apoptosis of tumour cells or their non-neoplastic progenitors are plausible mechanisms, other chemoprotective mechanisms are also worthy of consideration. These alternative mechanisms include enhancing DNA repair, antioxidant protection and immunomodulation. In addition, other cell targets, such as the stromal cells, endothelial cells and cells of the immune system, may be regulated by 1,25(OH)2D and contribute to vitamin D-mediated cancer prevention.

KDM6B/JMJD3 histone demethylase is induced by vitamin D and modulates its effects in colon cancer cells

KDM6B/JMJD3 is a histone H3 lysine demethylase with an important gene regulatory role in development and physiology. Here, we show that human JMJD3 expression is induced by the active vitamin D metabolite 1α,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) and that JMJD3 modulates the gene regulatory action of this hormone. 1,25(OH)(2)D(3) activates the JMJD3 gene promoter and increases the level of JMJD3 RNA in human cancer cells. JMJD3 upregulation was strictly dependent on vitamin D receptor (VDR) expression and was abolished by cycloheximide. In SW480-ADH colon cancer cells, JMJD3 knockdown or expression of an inactive mutant JMJD3 fragment decreased the induction by 1,25(OH)(2)D(3) of several target genes and of an epithelial adhesive phenotype. Moreover, JMJD3 knockdown upregulated the epithelial-to-mesenchymal transition inducers SNAIL1 and ZEB1 and the mesenchymal markers fibronectin and LEF1, while it downregulated the epithelial proteins E-cadherin, Claudin-1 and Claudin-7. Additionally, JMJD3 knockdown abolished the nuclear export of β-catenin and the inhibition of β-catenin transcriptional activity caused by 1,25(OH)(2)D(3). Importantly, the expression of JMJD3 correlated directly with that of VDR and inversely with that of SNAI1 in a series of 96 human colon tumours. Our results indicate for the first time that an epigenetic gene coding for a histone demethylase such as JMJD3 is a VDR co-target that partially mediates the effects of 1,25(OH)(2)D(3) on human colon.

Vitamin d and susceptibility of chronic lung diseases: role of epigenetics

Vitamin D deficiency is linked to accelerated decline in lung function, increased inflammation, and reduced immunity in chronic lung diseases. Epidemiological studies have suggested that vitamin D insufficiency is associated with low lung function in susceptible subjects who are exposed to higher levels of environmental agents (airborne particulates). Recent studies have highlighted the role of vitamin D and vitamin D receptor (VDR) in regulation of several genes that are involved in inflammation, immunity, cellular proliferation, differentiation, and apoptosis. Vitamin D has also been implicated in reversal of steroid resistance and airway remodeling, which are the hallmarks of chronic obstructive pulmonary disease (COPD) and severe asthma. VDR protein level is decreased in lungs of patients with COPD. VDR deficient mice develop an abnormal lung phenotype with characteristics of COPD, such as airspace enlargement and decline in lung function associated with increased lung inflammatory cellular influx, and immune-lymphoid aggregates formation. Dietary vitamin D may regulate epigenetic events, in particular on genes which are responsible for COPD susceptibility. Active metabolite of vitamin D, 1,25-dihydroxyvitamin D₃ plays an essential role in cellular metabolism and differentiation via its nuclear receptor (VDR) that cooperates with several other chromatin modification enzymes (histone acetyltransferases and histone deacetylases), thereby mediating complex epigenetic events in vitamin D signaling and metabolism. This review provides an update on the current knowledge and understanding on vitamin D, and susceptibility of chronic lung diseases in relation to the possible role of epigenetics in its molecular action. Understanding the molecular epigenetic mechanism of vitamin D/VDR would provide rationale for dietary vitamin D-mediated intervention in prevention and management of chronic lung diseases linked with vitamin D deficiency.

Inecalcitol, an analog of 1α,25(OH)(2) D(3) , induces growth arrest of androgen-dependent prostate cancer cells

19-nor-14-epi-23-yne-1,25(OH)(2) D(3) (inecalcitol) is a unique vitamin D(3) analog. We evaluated the activity of inecalcitol in a human prostate cancer model system. The analog was 11-fold more potent than 1,25(OH)(2) D(3) in causing 50% clonal growth inhibition of androgen-sensitive human prostate cancer LNCaP cells. Inecalcitol, more than 1,25(OH)(2) D(3) , reduced in a dose-dependent manner the expression levels of the transcription factor ETS variant 1 and the serine/threonine protein kinase Pim-1, both of which are upregulated in prostate cancer. Remarkably, dose challenge experiments revealed that inecalcitol maximal tolerated dose (MTD) by intraperitoneal (i.p.) administration was 30 μg/mouse (1,300 μg/kg) three times per week, while we previously found that the MTD of 1,25(OH)(2) D(3) is 0.0625 μg/mouse; therefore, inecalcitol is 480 times less hypercalcemic than 1,25(OH)(2) D(3) . Pharmacokinetic studies showed that plasma half-life of inecalcitol were 18.3 min in mice. A xenograft model of LNCaP cells was developed in immunodeficient mice treated with inecalcitol. The tumors of the diluent-treated control mice increased in size but those in the inecalcitol treatment group did not grow. Our data suggest that inecalcitol inhibits androgen-responsive prostate cancer growth in vivo and should be examined either alone or with other chemotherapy in clinical trials in individuals with rising serum prostate-specific antigen after receiving either surgery or irradiation therapy with curative intent.

Dexamethasone enhances 1alpha,25-dihydroxyvitamin D3 effects by increasing vitamin D receptor transcription

Calcitriol, the active form of vitamin D, in combination with the glucocorticoid dexamethasone (Dex) has been shown to increase the antitumor effects of calcitriol in squamous cell carcinoma. In this study we found that pretreatment with Dex potentiates calcitriol effects by inhibiting cell growth and increasing vitamin D receptor (VDR) and VDR-mediated transcription. Treatment with actinomycin D inhibits Vdr mRNA synthesis, indicating that Dex regulates VDR expression at transcriptional level. Real time PCR shows that treatment with Dex increases Vdr transcripts in a time- and a dose-dependent manner, indicating that Dex directly regulates expression of Vdr. RU486, an inhibitor of glucocorticoids, inhibits Dex-induced Vdr expression. In addition, the silencing of glucocorticoid receptor (GR) abolishes the induction of Vdr by Dex, indicating that Dex increases Vdr transcripts in a GR-dependent manner. A fragment located 5.2 kb upstream of Vdr transcription start site containing two putative glucocorticoid response elements (GREs) was evaluated using a luciferase-based reporter assay. Treatment with 100 nm Dex induces transcription of luciferase driven by the fragment. Deletion of the GRE distal to transcription start site was sufficient to abolish Dex induction of luciferase. Also, chromatin immunoprecipitation reveals recruitment of GR to distal GRE with Dex treatment. We conclude that Dex increases VDR and vitamin D effects by increasing Vdr de novo transcription in a GR-dependent manner.

MicroRNA-32 upregulation by 1,25-dihydroxyvitamin D3 in human myeloid leukemia cells leads to Bim targeting and inhibition of AraC-induced apoptosis

1,25-Dihydroxyvitamin D(3) (1,25D) used to treat human acute myeloid leukemia (AML) cells induces features of normal monocytes, but the mechanisms underlying this response are not fully understood. We hypothesized that one or more microRNAs (miRNA) known to control mouse hematopoiesis and lineage commitment might contribute to the ability of 1,25D to control the malignant phenotype. Here we report that 1,25D markedly induces expression of miR-32 in human myeloid leukemia cells, in which it targets the 3'-untranslated region of the mRNA encoding the proapoptotic factor Bim to reduce its expression. RNAi-mediated suppression of the miRNA-processing enzymes Drosha and Dicer increased Bim levels, in support of the concept that Bim is under miRNA control in AML cells. Antisense-mediated suppression of miR-32 was sufficient to upregulate Bim expression in AML cells. Conversely, ectopic expression of miR-32 downregulated Bim expression and increased the differentiation response to 1,25D treatment in a manner that was associated with increased cell survival. The positive effects of miR-32 on cell survival were confirmed by evidence of increased cell death in AML cells preexposed to antisense miR-32 before treatment with arabinocytosine, a chemotherapeutic drug used to treat human AML. Together, our findings indicate that miR-32 blockade is sufficient to elevate Bim expression and sensitize AML cells to chemotherapy-induced apoptosis. Thus, agents which can inhibit miR-32 expression may offer clinical utility by enhancing therapeutic efficacy in human AML.

The anti-cancer and anti-inflammatory actions of 1,25(OH)₂D₃

Various epidemiological studies have shown an aetiological link between vitamin D deficiency and cancer incidence. The active metabolite of vitamin D, 1,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃], has potent anti-cancer activities both in vitro and in vivo. These anti-cancer effects are attained by regulating the transcription of numerous genes that are involved in different pathways to reduce tumorigenesis and are dependent on the cancer cell type. Besides reducing cell growth and inducing apoptosis, 1,25(OH)₂D₃ also inhibits angiogenesis and metastasis. Moreover, its potency to inhibit inflammation also contributes to its anti-tumoral activity. Here, we report the different ways in which 1,25(OH)₂D₃ interferes with the malignant processes that are activated in cancer cells.