Calcitriol (1,25-Dihydroxycholecalciferol) Selectively Inhibits Proliferation of Freshly Isolated Tumor-Derived Endothelial Cells and Induces Apoptosis

In Vitro Angiogenesis Inhibition and Endothelial Cell Growth and Morphology

A co-culture assay with human umbilical vein endothelial cells (HUVECs) and normal human dermal fibroblasts (NHDFs) was used to study whether selected angiogenesis inhibitors were able to inhibit differentiation and network formation of HUVECs in vitro. The effect of the inhibitors was determined by the morphology and the calculated percentage area covered by HUVECs. Neutralizing VEGF with avastin and polyclonal goat anti-VEGF antibody and inhibiting VEGFR2 with sorafenib and vatalanib resulted in the formation of HUVEC clusters of variable sizes as a result of inhibited EC differentiation. Furthermore, numerous inhibitors of the VEGF signaling pathways were tested for their effect on the growth and differentiation of HUVECs. The effects of these inhibitors did not reveal a cluster morphology, either individually or when combined to block VEGFR2 downstream pathways. Only the addition of N-methyl-p-bromolevamisole revealed a similar morphology as when targeting VEGF and VEGFR2, meaning it may have an inhibitory influence directly on VEGFR signaling. Additionally, several nuclear receptor ligands and miscellaneous compounds that might affect EC growth and differentiation were tested, but only dexamethasone gave rise to cluster formation similarly to VEGF-neutralizing compounds. These results point to a link between angiogenesis, HUVEC differentiation and glucocorticoid receptor activation.

Vitamin D and Cancer: An Historical Overview of the Epidemiology and Mechanisms

This is a narrative review of the evidence supporting vitamin D’s anticancer actions. The first section reviews the findings from ecological studies of cancer with respect to indices of solar radiation, which found a reduced risk of incidence and mortality for approximately 23 types of cancer. Meta-analyses of observational studies reported the inverse correlations of serum 25-hydroxyvitamin D [25(OH)D] with the incidence of 12 types of cancer. Case-control studies with a 25(OH)D concentration measured near the time of cancer diagnosis are stronger than nested case-control and cohort studies as long follow-up times reduce the correlations due to changes in 25(OH)D with time. There is no evidence that undiagnosed cancer reduces 25(OH)D concentrations unless the cancer is at a very advanced stage. Meta-analyses of cancer incidence with respect to dietary intake have had limited success due to the low amount of vitamin D in most diets. An analysis of 25(OH)D-cancer incidence rates suggests that achieving 80 ng/mL vs. 10 ng/mL would reduce cancer incidence rates by 70 ± 10%. Clinical trials have provided limited support for the UVB-vitamin D-cancer hypothesis due to poor design and execution. In recent decades, many experimental studies in cultured cells and animal models have described a wide range of anticancer effects of vitamin D compounds. This paper will review studies showing the inhibition of tumor cell proliferation, dedifferentiation, and invasion together with the sensitization to proapoptotic agents. Moreover, 1,25-(OH)₂D₃ and other vitamin D receptor agonists modulate the biology of several types of stromal cells such as fibroblasts, endothelial and immune cells in a way that interferes the apparition of metastases. In sum, the available mechanistic data support the global protective action of vitamin D against several important types of cancer.

Severe Vitamin D Deficiency Increases Mortality Among Patients With Liver Cirrhosis Regardless of the Presence of HCC

BACKGROUND

The aim of this study was to investigate the association between vitamin D deficiency (<10 mg/ml) and mortality in patients with and without hepatocellular carcinoma (HCC) in a cohort of patients with liver cirrhosis.

MATERIALS AND METHODS

A prospective study was conducted among 345 patients with liver cirrhosis.

RESULTS

At enrolment, 46 (13.3%) patients had HCC. Severe vitamin D deficiency was associated with mortality (p<0.01). At the survival analysis, alpha-fetoprotein >10 ng/ml (p=0.003), vitamin D deficiency (p<0.001), a Model for End-Stage Liver Disease score ≥15 (p<0.001), Child-Pugh class B and C (versus A) (p<0.001) and the presence of active HCC (p<0.001) were strongly associated with death. At the multivariate Cox regression analysis, only Child-Pugh class B and C (versus A) and vitamin D deficiency were found to be significantly associated with death during the follow-up period (p<0.001 and p=0.006, respectively).

CONCLUSION

Vitamin D deficiency is common in patients with HCC, it is associated with active HCC and it negatively affects the overall survival of patients with cirrhosis.

Glucocorticoid-mediated effects on angiogenesis in solid tumors

Angiogenesis is essential in tumor development to maintain the oxygen and nutrient supply. Glucocorticoids have shown both direct and indirect angiostatic properties in various types of solid cancers. In most of the reported cases glucocorticoid-mediated actions involved suppression of multiple pro-angiogenic factors expression by cancer cells. The anti-angiogenic properties of glucocorticoids correlated with diminished tumor vasculature and reduced tumor growth in multiple in vivo studies. However, when glucocorticoid treatment is considered, possible adverse events should be taken into account. Additional research is needed to further test the use of these steroidal drugs in cancer therapy.

Vitamin D Analogues Tacalcitol and Calcipotriol Inhibit Proliferation and Migration of T98G Human Glioblastoma Cells

The active form of vitamin D (1α,25-dihydroxyvitamin D) acts as a steroid hormone and binds to the vitamin D receptor. This receptor is expressed in most cell types including cells in the central nervous system (CNS). Vitamin D has several functions in the body including effects on brain development, neuroprotection and immunological regulation. It has been shown that vitamin D has antiproliferative activities in different cancer cell lines. Tacalcitol and calcipotriol are synthetic analogues of 1α,25-dihydroxyvitamin D with reduced effect on calcium metabolism. The aim of this study was to analyse the effects of tacalcitol and calcipotriol on cell viability, proliferation and migration in the human glioblastoma cell line T98G. Glioblastoma is the most lethal type of primary tumours in the CNS. Both analogues decreased cell viability and/or growth, dose-dependently, in concentrations between 1 nM and 10 μM. Manual counting indicated suppressive effects by the vitamin D analogues on proliferation. Treatment with tacalcitol strongly suppressed thymidine incorporation, indicating that the vitamin D analogues mainly inhibit proliferation. Also, effects on cell migration were measured with wound-healing assay. Both calcipotriol and tacalcitol reduced the migration rate of T98G cells compared to vehicle-treated cells. However, they had no effect on caspase-3 and -7 activities, suggesting that their mechanism of action does not involve induction of apoptosis. The current results indicate that the vitamin D analogues tacalcitol and calcipotriol strongly reduce proliferation and migration of human glioblastoma T98G cells, suggesting a potential role for this type of compounds in treatment of brain cancer.

Adipose tissue inflammation and VDR expression and methylation in colorectal cancer

Background

Lack of vitamin D (VD) has been associated with colorectal cancer (CRC). VD has anti-inflammatory effects and regulates several cellular pathways by means of its receptor, including epigenetic modifications. Adipose tissue dysfunction has been related to low-grade inflammation, which is related to diseases like cancer. The aim of this study was to explore the relationship between serum 25-hydroxyvitamin D (25(OH)D), adipose tissue gene expression of VD receptor (VDR), pro-inflammatory markers, and the epigenetic factor DNA methyltransferase 3a (DNMT3A) as well as VDR promoter methylation in CRC.

Methods

Blood and visceral adipose tissue from 57 CRC and 50 healthy control subjects were collected. CRC subjects had lower serum 25(OH)D levels and higher VDR gene expression, and these were negatively correlated in the CRC group.

Results

Adipose tissue NFκB1, IL6, and IL1B gene expression were higher in the CRC subjects than in the control subjects. 25(OH)D correlated negatively with NFκB1 and CRP. In turn, CRP correlated positively with NFκB1, IL6, IL1B, and VDR gene expression as well as NFκB1 that correlated positively with IL6 and IL1B. DNMT3A mRNA was negatively correlated with serum 25(OH)D and positively correlated with VDR DNA methylation. VDR DNA methylation at position 4 had lower levels in the CRC group. Global NFκB1 methylation at dinucleotide 3 was lower in the CRC group.

Conclusion

Our results suggest that adipose tissue may be a key factor in CRC development. The low 25(OH)D levels and high adipose tissue VDR expression in CRC may, at least in part, mediate this relationship by modifying adipose tissue DNA methylation and promoting inflammation.

Electronic supplementary material

The online version of this article (10.1186/s13148-018-0493-0) contains supplementary material, which is available to authorized users.

Vitamin D Signaling Modulators in Cancer Therapy

The antiproliferative and pro-apoptotic effects of 1α,25-dihydroxycholecalciferol (1,25(OH)2D3, 1,25D3, calcitriol) have been demonstrated in various tumor model systems in vitro and in vivo. However, limited antitumor effects of 1,25D3 have been observed in clinical trials. This may be attributed to a variety of factors including overexpression of the primary 1,25D3 degrading enzyme, CYP24A1, in tumors, which would lead to rapid local inactivation of 1,25D3. An alternative strategy for improving the antitumor activity of 1,25D3 involves the combination with a selective CYP24A1 inhibitor. The validity of this approach is supported by numerous preclinical investigations, which demonstrate that CYP24A1 inhibitors suppress 1,25D3 catabolism in tumor cells and increase the effects of 1,25D3 on gene expression and cell growth. Studies are now required to determine whether selective CYP24A1 inhibitors+1,25D3 can be used safely and effectively in patients. CYP24A1 inhibitors plus 1,25D3 can cause dose-limiting toxicity of vitamin D (hypercalcemia) in some patients. Dexamethasone significantly reduces 1,25D3-mediated hypercalcemia and enhances the antitumor activity of 1,25D3, increases VDR-ligand binding, and increases VDR protein expression. Efforts to dissect the mechanisms responsible for CYP24A1 overexpression and combinational effect of 1,25D3/dexamethasone in tumors are underway. Understanding the cross talk between vitamin D receptor (VDR) and glucocorticoid receptor (GR) signaling axes is of crucial importance to the design of new therapies that include 1,25D3 and dexamethasone. Insights gained from these studies are expected to yield novel strategies to improve the efficacy of 1,25D3 treatment.

MART-10, the new brand of 1α,25(OH)2D3 analog, is a potent anti-angiogenic agent in vivo and in vitro

BACKGROUND

Angiogenesis is the hall marker for cancer growth and metastasis. Thus, anti-angiogenesis emerges as a new way to treat cancer. 1α,25(OH)2D3 is recently getting popular due to the non-mineral functions, which have been applied fore cancer treatment. The newly-synthesized 1α,25(OH)2D3 analog, MART-10, has been proved to be much more potent than 1α,25(OH)2D3 regarding inhibiting cancer cells growth and metastasis without inducing hypercalcemia in vivo. In this study, we aimed to investigate the effect of MART-10 and 1α,25(OH)2D3 on angiogenesis in vitro and in vivo.

METHODS AND RESULTS

MART-10 and 1α,25(OH)2D3 were able to repress VEGFA-induced human umbilical vein endothelial cells (HUVECs) migration, invasion and tube formation, but not proliferation, with MART-10 much more potent than 1α,25(OH)2D3. The Chick Chorioallantoic Membrane (CAM) assay and matrigeal angiogenesis assay further confirmed the in vivo more potent anti-angiogenesis effect of MART-10. MART-10 inhibited the VEGFA-induced HUVECs angiogenesis process through downregulation of Akt and Erk 1/2 phosphorylation. The VEGFA-VEGFR2 (VEGF receptor 2) axis is the main signal transducing pathway to stimulate angiogenesis. A positive autocrine manner was found for the first time in HUVECs as treated by VEGFA, which induced VEGFA expression and secretion, and VEGFR2 expression. MART-10 and 1α,25(OH)2D3 were demonstrated to be able to repress this positive autocrine manner, thus inhibiting angiogenesis.

CONCLUSIONS

MART-10 and 1α,25(OH)2D3 both are effective anti-angiogenesis agents. Given MART-10 is much more potent than 1α,25(OH)2D3 and active in vivo without obvious side effect, MART-10 should be deemed as a promising anti-cancer agent.

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.

Vitamin D supplementation for prevention of cancer in adults

BACKGROUND

The evidence on whether vitamin D supplementation is effective in decreasing cancers is contradictory.

OBJECTIVES

To assess the beneficial and harmful effects of vitamin D supplementation for prevention of cancer in adults.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, LILACS, Science Citation Index Expanded, and the Conference Proceedings Citation Index-Science to February 2014. We scanned bibliographies of relevant publications and asked experts and pharmaceutical companies for additional trials.

SELECTION CRITERIA

We included randomised trials that compared vitamin D at any dose, duration, and route of administration versus placebo or no intervention in adults who were healthy or were recruited among the general population, or diagnosed with a specific disease. Vitamin D could have been administered as supplemental vitamin D (vitamin D₃ (cholecalciferol) or vitamin D₂ (ergocalciferol)), or an active form of vitamin D (1α-hydroxyvitamin D (alfacalcidol), or 1,25-dihydroxyvitamin D (calcitriol)).

DATA COLLECTION AND ANALYSIS

Two review authors extracted data independently. We conducted random-effects and fixed-effect model meta-analyses. For dichotomous outcomes, we calculated the risk ratios (RRs). We considered risk of bias in order to assess the risk of systematic errors. We conducted trial sequential analyses to assess the risk of random errors.

MAIN RESULTS

Eighteen randomised trials with 50,623 participants provided data for the analyses. All trials came from high-income countries. Most of the trials had a high risk of bias, mainly for-profit bias. Most trials included elderly community-dwelling women (aged 47 to 97 years). Vitamin D was administered for a weighted mean of six years. Fourteen trials tested vitamin D₃, one trial tested vitamin D₂, and three trials tested calcitriol supplementation. Cancer occurrence was observed in 1927/25,275 (7.6%) recipients of vitamin D versus 1943/25,348 (7.7%) recipients of control interventions (RR 1.00 (95% confidence interval (CI) 0.94 to 1.06); P = 0.88; I² = 0%; 18 trials; 50,623 participants; moderate quality evidence according to the GRADE instrument). Trial sequential analysis (TSA) of the 18 vitamin D trials shows that the futility area is reached after the 10th trial, allowing us to conclude that a possible intervention effect, if any, is lower than a 5% relative risk reduction. We did not observe substantial differences in the effect of vitamin D on cancer in subgroup analyses of trials at low risk of bias compared to trials at high risk of bias; of trials with no risk of for-profit bias compared to trials with risk of for-profit bias; of trials assessing primary prevention compared to trials assessing secondary prevention; of trials including participants with vitamin D levels below 20 ng/mL at entry compared to trials including participants with vitamin D levels of 20 ng/mL or more at entry; or of trials using concomitant calcium supplementation compared to trials without calcium. Vitamin D decreased all-cause mortality (1854/24,846 (7.5%) versus 2007/25,020 (8.0%); RR 0.93 (95% CI 0.88 to 0.98); P = 0.009; I² = 0%; 15 trials; 49,866 participants; moderate quality evidence), but TSA indicates that this finding could be due to random errors. Cancer occurrence was observed in 1918/24,908 (7.7%) recipients of vitamin D₃ versus 1933/24,983 (7.7%) in recipients of control interventions (RR 1.00 (95% CI 0.94 to 1.06); P = 0.88; I² = 0%; 14 trials; 49,891 participants; moderate quality evidence). TSA of the vitamin D₃ trials shows that the futility area is reached after the 10th trial, allowing us to conclude that a possible intervention effect, if any, is lower than a 5% relative risk reduction. Vitamin D₃ decreased cancer mortality (558/22,286 (2.5%) versus 634/22,206 (2.8%); RR 0.88 (95% CI 0.78 to 0.98); P = 0.02; I² = 0%; 4 trials; 44,492 participants; low quality evidence), but TSA indicates that this finding could be due to random errors. Vitamin D₃ combined with calcium increased nephrolithiasis (RR 1.17 (95% CI 1.03 to 1.34); P = 0.02; I² = 0%; 3 trials; 42,753 participants; moderate quality evidence). TSA, however, indicates that this finding could be due to random errors. We did not find any data on health-related quality of life or health economics in the randomised trials included in this review.

AUTHORS' CONCLUSIONS

There is currently no firm evidence that vitamin D supplementation decreases or increases cancer occurrence in predominantly elderly community-dwelling women. Vitamin D₃ supplementation decreased cancer mortality and vitamin D supplementation decreased all-cause mortality, but these estimates are at risk of type I errors due to the fact that too few participants were examined, and to risks of attrition bias originating from substantial dropout of participants. Combined vitamin D₃ and calcium supplements increased nephrolithiasis, whereas it remains unclear from the included trials whether vitamin D₃, calcium, or both were responsible for this effect. We need more trials on vitamin D supplementation, assessing the benefits and harms among younger participants, men, and people with low vitamin D status, and assessing longer duration of treatments as well as higher dosages of vitamin D. Follow-up of all participants is necessary to reduce attrition bias.

1α,25-dihydroxyvitamin D3 modulates CYP2R1 gene expression in human oral squamous cell carcinoma tumor cells

Oral squamous cell carcinomas (OSCC) are the most common malignant neoplasms associated with mucosal surfaces of the oral cavity and oropharynx. 1α,25-Dihydroxyvitamin D3 (1,25(OH)2D3) is implicated as an anticancer agent. Cytochrome P450 2R1 (CYP2R1) is a microsomal vitamin D 25-hydroxylase which plays an important role in converting dietary vitamin D to active metabolite, 25-(OH)D3. We identified high levels of CYP2R1 expression using tissue microarray of human OSCC tumor specimens compared to normal adjacent tissue. Therefore, we hypothesize that 1,25(OH)2D3 regulates CYP2R1 gene expression in OSCC tumor cells. Interestingly, real-time RT-PCR analysis of total RNA isolated from OSCC cells (SCC1, SCC11B, and SCC14a) treated with 1,25(OH)2D3 showed a significant increase in CYP2R1 and vitamin D receptor (VDR) mRNA expression. Also, Western blot analysis demonstrated that 1,25(OH)2D3 treatment time-dependently increased CYP2R1 expression in these cells. 1,25(OH)2D3 stimulation of OSCC cells transiently transfected with the hCYP2R1 promoter (-2 kb)-luciferase reporter plasmid demonstrated a 4.3-fold increase in promoter activity. In addition, 1,25(OH)2D3 significantly increased c-Fos, p-c-Jun expression, and c-Jun N-terminal kinase (JNK) activity in these cells. The JNK inhibitor suppresses 1,25(OH)2D3, inducing CYP2R1 mRNA expression and gene promoter activity in OSCC cells. Furthermore, JNK inhibitor significantly decreased 1,25(OH)2D3 inhibition of OSCC tumor cell proliferation. Taken together, our results suggest that AP-1 is a downstream effector of 1,25(OH)2D3 signaling to modulate CYP2R1 gene expression in OSCC tumor cells, and vitamin D analogs could be potential therapeutic agents to control OSCC tumor progression.

Epigenetic regulation of the 1,25-dihydroxyvitamin D3 24-hydroxylase (CYP24A1) in colon cancer cells

Calcitriol is the hormonally active form of vitamin D and has anti-proliferative and pro-apoptotic effects. Calcitriol and its precursor calcidiol (25(OH)D3) are degraded by the 1,25-dihydroxyvitamin D3 24-hydroxylase (CYP24A1). This enzyme is overexpressed in colorectal tumors, however, the mechanisms of this overexpression remain to be elucidated. CYP24A1 mRNA level differs among colorectal cancer cell lines and range from almost undetectable to high. Since DNA methylation and histone acetylation regulate CYP24A1 gene expression in prostate cancer cell lines, we investigated whether epigenetic mechanisms could explain the differences in basal expression of CYP24A1 in colon cancer cells. Methyltransferase inhibitor 5-aza-2'-deoxycytidine (DAC) treatment resulted in an over 50-fold induction of CYP24A1 mRNA expression in Coga1A and HT-29 cells but in no response in Caco2/AQ and Coga13 cells. This finding is supported by a strong increase in CYP24A1 activity after DAC treatment in Coga1A (35%). In addition, calcitriol and DAC had synergistic effects on CYP24A1 gene transcription. Interestingly, the CYP24A1 promoter was not methylated in Coga1A and HT-29 (<5%), while in Caco2/AQ it was 62% methylated. This suggests that DNA demethylation must activate genes upstream of CYP24A1 rather than act on the gene itself. However, transcriptional regulators of CYP24A1 such as vitamin D receptor (VDR), retinoid X receptor (RXR), specificity protein 1 (SP1), or mediator complex subunit 1 (MED1) were not upregulated. We conclude that in colon cancer cells, CYP24A1 gene expression is inducible by methyltransferase and some histone deacetylase inhibitors in a cell line-dependent manner. This effect does not correlate with the methylation state of the promoter and therefore must affect genes upstream of CYP24A1. This article is part of a Special Issue 'Vitamin D Workshop'.

Role of androgen and vitamin D receptors in endothelial cells from benign and malignant human prostate

Forty years ago, Judah Folkman (Folkman. N Engl J Med 285: 1182-1186, 1971) proposed that tumor growth might be controlled by limiting formation of new blood vessels (angiogenesis) needed to supply a growing tumor with oxygen and nutrients. To this end, numerous "antiangiogenic" agents have been developed and tested for therapeutic efficacy in cancer patients, including prostate cancer (CaP) patients, with limited success. Despite the lack of clinical efficacy of lead anti-angiogenic therapeutics in CaP patients, recent published evidence continues to support the idea that prostate tumor vasculature provides a reasonable target for development of new therapeutics. Particularly relevant to antiangiogenic therapies targeted to the prostate is the observation that specific hormones can affect the survival and vascular function of prostate endothelial cells within normal and malignant prostate tissues. Here, we review the evidence demonstrating that both androgen(s) and vitamin D significantly impact the growth and survival of endothelial cells residing within prostate cancer and that systemic changes in circulating androgen or vitamin D drastically affect blood flow and vascularity of prostate tissue. Furthermore, recent evidence will be discussed about the expression of the receptors for both androgen and vitamin D in prostate endothelial cells that argues for direct effects of these hormone-activated receptors on the biology of endothelial cells. Based on this literature, we propose that prostate tumor vasculature represents an unexplored target for modulation of tumor growth. A better understanding of androgen and vitamin D effects on prostate endothelial cells will support development of more effective angiogenesis-targeting therapeutics for CaP patients.

Dexamethasone has variable effects on mesenchymal stromal cells

BACKGROUND AIMS

Dexamethasone (Dex) is a potent synthetic member of the glucocorticoid class of steroid drugs. Frequently, Dex has been used to enhance osteogenic, chondrogenic and adipogenic differentiation of mesenchymal stromal cells (MSC). Recently, Dex was applied to promote MSC proliferation, because of the rare frequency of MSC in bone marrow, and could protect the cells from apoptosis. The effects of Dex on MSC cytobiology behavior needs to be investigated.

METHODS

MSC were obtained from human umbilical cord. The surface phenotype and functional characterization of MSC cultured with different concentrations of Dex were investigated, in comparison with a control group, including MSC proliferation, apoptosis, cytokine expression and immunosuppression.

RESULTS

Different concentrations of Dex exerted diverse effects on MSC proliferation and apoptosis. Dex was also able to affect the pattern of cytokine expression of MSC. Furthermore, Dex impaired immunosuppression of MSC on peripheral blood mononuclear cells.

CONCLUSIONS

A low dose of Dex favors MSC expansion in vitro, and protects against apoptosis. It is not suitable for MSC to be pre-treated with Dex when they are to be used to treat immunologic disease. However, when MSC are applied to promote angiogenesis, it is beneficial for them to be pre-treated with 10(-9) mol/L Dex.

VDR/RXR and TCF4/β-catenin cistromes in colonic cells of colorectal tumor origin: impact on c-FOS and c-MYC gene expression

Many of the transcriptional and growth regulating activities of 1α,25-dihydroxyvitamin D(3) [1,25-(OH)(2)D(3)] in the intestine and colon are recapitulated in the human colorectal cancer cell LS180. We therefore used this line together with chromatin immunoprecipitation-seq and gene expression analyses to identify the vitamin D receptor (VDR)/retinoid X receptor (RXR) and transcription factor 7-like 2 (TCF7L2/TCF4)/β-catenin cistromes and the genes that they regulate. VDR and RXR colocalized to predominantly promoter distal, vitamin D response element-containing sites in a largely ligand-dependent manner. These regulatory sites control the expression of both known as well as novel 1,25-(OH)(2)D(3) target genes. TCF4 and β-catenin cistromes partially overlapped, contained TCF/lymphoid enhancer-binding factor consensus elements, and were only modestly influenced by 1,25-(OH)(2)D(3). However, the two heterodimer complexes colocalized at sites near a limited set of genes that included c-FOS and c-MYC; the expression of both genes was modulated by 1,25-(OH)(2)D(3). At the c-FOS gene, both VDR/RXR and TCF4/β-catenin bound to a single distal enhancer located 24 kb upstream of the transcriptional start site. At the c-MYC locus, however, binding was noted at a cluster of sites between -139 and -165 kb and at a site located -335 kb upstream. Examined as isolated enhancer fragments, these regions exhibited basal and 1,25-(OH)(2)D(3)-inducible activities that were interlinked to both VDR and β-catenin activation. These data reveal additional complexity in the regulation of target genes by 1,25-(OH)(2)D(3) and support a direct action of both VDR and the TCF4/β-catenin regulatory complex at c-FOS and c-MYC.

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.

Role of vitamin d in the prevention of pancreatic cancer

Pancreatic cancer is a malignancy of poor prognosis which is mostly diagnosed at advanced stages. Current treatment modalities are very limited creating great interest for novel preventive and therapeutic options. Vitamin D seems to have a protective effect against pancreatic cancer by participating in numerous proapoptotic, antiangiogenic, anti-inflammatory, prodifferentiating, and immunomodulating mechanisms. 25-hydroxyvitamin D [25(OH)D] serum concentrations are currently the best indicator of vitamin D status. There are three main sources of vitamin D: sun exposure, diet,and dietary supplements. Sun exposure has been associated with lower incidence of pancreatic cancer in ecological studies. Increased vitamin D levels seem to protect against pancreatic cancer, but caution is needed as excessive dietary intake may have opposite results. Future studies will verify the role of vitamin D in the prevention and therapy of pancreatic cancer and will lead to guidelines on adequate sun exposure and vitamin D dietary intake.

Involvement of stress activated protein kinases (JNK and p38) in 1,25 dihydroxyvitamin D3-induced breast cell death

It has been previously demonstrated that 1,25 dihydroxyvitamin D(3) (1,25-D(3)) exerts inhibitory effects in breast cancer cells. The aim of this study was to determine whether mitogen-activated protein kinase (MAPK) pathways are associated with 1,25-D(3)-induced cell death in breast cancer. We used three breast cell lines which have different sensitivities to 1,25-D(3) treatment. Non-malignant MCF-12A cells were more sensitive to 1,25-D(3) treatment than malignant MCF-7 cells (growth inhibition IC(50) 75 nM vs. 100 nM, p<0.001) while malignant MDA-MB-231 cells were resistant. Moreover, 1,25-D(3)-induced apoptosis was caspase-dependent in MCF-12A cells and caspase-independent in MCF-7 cells. Following MAPK activation analysis, we found a significant activation of JNK in MCF-12A cells and malignant MCF-7 cells in response to 1,25-D(3) treatment. Furthermore, 1,25-D(3) treatment stimulated p38 activity in MCF-12A cells and in MCF-7 cells. ERK1/2 activity was unaffected by 1,25-D(3) treatment in all breast cells. Importantly, no increased MAPK activity was observed in MDA-MB-231 breast cancer cells which displayed resistance to 1,25-D(3)-induced apoptosis. Utilising specific pharmacological inhibitors of JNK and p38, it was demonstrated that MCF-12A and MCF-7 cells were protected from death induced by 1,25-D(3). These results implicate JNK and p38 signalling in 1,25-D(3)-induced cancer breast cell death.

Epigenetic silencing of CYP24 in the tumor microenvironment

Calcitriol (1,25 dihydroxycholecalciferol) has significant anti-tumor activity in vitro and in vivo in a number of tumor model systems. We developed a system for isolation of fresh endothelial cells from tumors and Matrigel environments which demonstrate that CYP24, the catabolic enzyme involved in vitamin D signaling, is epigenetically silenced selectively in tumor-derived endothelial cells (TDEC). TDEC maintain phenotypic characteristics which are distinct from endothelial cells isolated from normal tissues and from Matrigel plugs (MDEC). In TDEC, calcitriol induces G(0)/G(1) arrest, modulates p27 and p21, and induces apoptotic cell death and decreases P-Erk and P-Akt. In contrast, endothelial cells isolated from normal tissues and MDEC are unresponsive to calcitriol-mediated anti-proliferative effects despite intact signaling through the vitamin D receptor (VDR). In TDEC, which are sensitive to calcitriol, the CYP24 promoter is hypermethylated in two CpG island regions located at the 5'end; this hypermethylation may contribute to gene silencing of CYP24. The extent of methylation in these two regions is significantly less in MDEC. Lastly, treatment of TDEC with a DNA methyltransferase inhibitor restores calcitriol-mediated induction of CYP24 and resistance to calcitriol. These data suggest that epigenetic silencing of CYP24 modulates cellular responses to calcitriol.

Glucocorticoid regulation of the vitamin D receptor

Many studies indicate calcitriol has potent anti-tumor activity in different types of cancers. However, high levels of vitamin D can produce hypercalcemia in some patients. Glucocorticoids are used to ameliorate hypercalcemia and to enhance calcitriol anti-tumor activity. Calcitriol in combination with the glucocorticoid dexamethasone (Dex) increased vitamin D receptor (VDR) protein levels and ligand binding in squamous cell carcinoma VII (SCC). In this study we found that both calcitriol and Dex induce VDR- and glucocorticoid receptor (GR)-mediated transcription respectively, indicating both hormone receptors are active in SCC. Pre-treatment with Dex increases VDR-mediated transcription at the human CYP24A1 promoter. Whereas, pre-treatment with other steroid hormones, including dihydrotestosterone and R1881, has no effect on VDR-mediated transcription. Real-time PCR indicates treatment with Dex increases Vdr transcripts in a time-dependent manner, suggesting Dex may directly regulate expression of Vdr. Numerous putative glucocorticoid response elements (GREs) were found in the Vdr gene. Chromatin immuno-precipitation (ChIP) assay demonstrated GR binding at several putative GREs located within the mouse Vdr gene. However, none of the putative GREs studied increase GR-mediated transcription in luciferase reporter assays. In an attempt to identify the response element responsible for Vdr transcript regulation, future studies will continue to analyze newly identified GREs more distal from the Vdr gene promoter.

Effect of a vitamin D(3) derivative (B3CD) with postulated anti-cancer activity in an ovarian cancer animal model

The objective of the present study was to test the hypothesis that Calcidiol derivative B3CD qualifies as a potential anti-cancer drug in vivo employing an ovarian cancer xenograft model in mice. In addition, the selectivity of B3CD on viability and proliferation of platinum-resistant human ovarian cancer cell lines in comparison to control cell lines was analyzed in vitro. B3CD displayed cell line-specific cytotoxicity screened against a panel of ovarian and other carcinoma cell lines, endothelial and control cells. B3CD, at sub-cytotoxic concentrations, revealed stronger effects on the proliferation of SKOV-3 ovarian cancer cells vs. primary fibroblasts as determined by BrdU incorporation analysis. Treatment with B3CD at 0.5 microM resulted in highly condensed chromatin and fragmented nuclei in SKOV-3 cells but not in primary fibroblasts. B3CD induced cell death at low drug concentrations (< or = 0.5 microM) in SKOV-3 ovarian cancer cells is mediated by the p38 MAPK signaling pathway: B3CD induced p38 MAPK expression and activation in SKOV-3 cells and inhibition of p38 signaling counteracted B3CD induced cell death in vitro. An ovarian cancer cell animal model (human SKOV-3 cell derived xenografts in nude mice) revealed that tumor growth in few B3CD treated mice accelerated while the majority of B3CD treated mice displayed delayed tumor growth or full tumor regression. B3CD possesses anti-ovarian cancer properties in vitro and in vivo. We propose the further development of non-calcemic bromoacetoxy derivatives of vitamin D(3) as potential anti-cancer therapeutics.

EB1089 induces Skp2-dependent p27 accumulation, leading to cell growth inhibition and cell cycle G1 phase arrest in human hepatoma cells

EB1089 exhibits a high level of antiproliferative activity against various tumors. However, it is not known whether the mechanism of EB1089 induced the growth inhibition in human hepatic-carcinoma. Here we found that EB1089 significantly reduced cell growth in human hepatoma cells (Hep-G2) and blocked Hep-G2 cell-associated tumor formation in nude mice. The growth inhibition was linked to cell cycle G1 phase arrest by the accumulation of p27 and a reduction of Skp2. Knockdown of Skp2 reversed the p27 induction and G1 arrest. Taken together, our data indicate that EB1089 inhibitory activity is associated with alteration of cell cycle checkpoints through Skp2-dependent p27 induction in Hep-G2 cells.

Role of vitamin D receptor in the antiproliferative effects of calcitriol in tumor-derived endothelial cells and tumor angiogenesis in vivo

Calcitriol (1,25-dihydroxycholecalciferol), the major active form of vitamin D, is antiproliferative in tumor cells and tumor-derived endothelial cells (TDEC). These actions of calcitriol are mediated at least in part by vitamin D receptor (VDR), which is expressed in many tissues including endothelial cells. To investigate the role of VDR in calcitriol effects on tumor vasculature, we established TRAMP-2 tumors subcutaneously into either VDR wild-type (WT) or knockout (KO) mice. Within 30 days post-inoculation, tumors in KO mice were larger than those in WT (P < 0.001). TDEC from WT expressed VDR and were able to transactivate a reporter gene whereas TDEC from KO mice were not. Treatment with calcitriol resulted in growth inhibition in TDEC expressing VDR. However, TDEC from KO mice were relatively resistant, suggesting that calcitriol-mediated growth inhibition on TDEC is VDR-dependent. Further analysis of the TRAMP-C2 tumor sections revealed that the vessels in KO mice were enlarged and had less pericyte coverage compared with WT (P < 0.001). Contrast-enhanced magnetic resonance imaging showed an increase in vascular volume of TRAMP tumors grown in VDR KO mice compared with WT mice (P < 0.001) and FITC-dextran permeability assay suggested a higher extent of vascular leakage in tumors from KO mice. Using ELISA and Western blot analysis, there was an increase of hypoxia-inducible factor-1alpha, vascular endothelial growth factor, angiopoietin 1, and platelet-derived growth factor-BB levels observed in tumors from KO mice. These results indicate that calcitriol-mediated antiproliferative effects on TDEC are VDR-dependent and loss of VDR can lead to abnormal tumor angiogenesis.

Dexamethasone inhibition of confluence-induced apoptosis in human mesenchymal stem cells

Human mesenchymal stem cells (MSCs) have been extensively characterized with respect to their in vitro expansion and differentiation potential, especially with respect to osteogenesis. Dexamethasone (Dex) is a well-known inducer of osteogenic differentiation of MSCs, but little is known about the effect of Dex treatment on apoptosis in MSCs. In this study, apoptosis in MSCs was examined with respect to cell density and Dex supplementation, using DAPI staining and DNA fragmentation ELISA Assay. In MSC cultures initiated at 1.0, 3.0, and 9.0 x 10(3) cells per cm(2), it was found that higher MSC density correlated with increased apoptosis and that this apoptotic effect was diminished in cultures containing 100 nM Dex. MSCs and fibroblasts were co-cultured, along with empty insert controls, and assayed for apoptosis by ELISA and DAPI counts to determine if soluble factors accounted for the cell density-related apoptosis. No difference was seen between MSCs cultured with inserts containing either MSCs, fibroblasts, or empty control. To determine cell contact effects, BrdU-labeled MSCs were cultured alone or with unlabeled chondrocytes at 2x and 8x the number of MSCs, with and without Dex, and apoptosis levels quantified. The results showed increased apoptosis at greater cell densities, and that the amount of apoptosis was greatly diminished in cultures containing Dex. These results show that apoptosis in MSCs is cell density-related, requires direct cell contact, and that Dex treatment reduces or eliminates this density-related apoptosis. These results may impact how MSCs should be cultured for clinical applications.

Vitamin D and human health: lessons from vitamin D receptor null mice

The vitamin D endocrine system is essential for calcium and bone homeostasis. The precise mode of action and the full spectrum of activities of the vitamin D hormone, 1,25-dihydroxyvitamin D [1,25-(OH)(2)D], can now be better evaluated by critical analysis of mice with engineered deletion of the vitamin D receptor (VDR). Absence of a functional VDR or the key activating enzyme, 25-OHD-1alpha-hydroxylase (CYP27B1), in mice creates a bone and growth plate phenotype that mimics humans with the same congenital disease or severe vitamin D deficiency. The intestine is the key target for the VDR because high calcium intake, or selective VDR rescue in the intestine, restores a normal bone and growth plate phenotype. The VDR is nearly ubiquitously expressed, and almost all cells respond to 1,25-(OH)(2)D exposure; about 3% of the mouse or human genome is regulated, directly and/or indirectly, by the vitamin D endocrine system, suggesting a more widespread function. VDR-deficient mice, but not vitamin D- or 1alpha-hydroxylase-deficient mice, and man develop total alopecia, indicating that the function of the VDR and its ligand is not fully overlapping. The immune system of VDR- or vitamin D-deficient mice is grossly normal but shows increased sensitivity to autoimmune diseases such as inflammatory bowel disease or type 1 diabetes after exposure to predisposing factors. VDR-deficient mice do not have a spontaneous increase in cancer but are more prone to oncogene- or chemocarcinogen-induced tumors. They also develop high renin hypertension, cardiac hypertrophy, and increased thrombogenicity. Vitamin D deficiency in humans is associated with increased prevalence of diseases, as predicted by the VDR null phenotype. Prospective vitamin D supplementation studies with multiple noncalcemic endpoints are needed to define the benefits of an optimal vitamin D status.

25-Hydroxyvitamin D3 is a natural chemopreventive agent against carcinogen induced precancerous lesions in mouse mammary gland organ culture

Despite the role of vitamin D(3) endocrine system in prevention of mammary gland transformation in animal models, use of 1,25(OH)(2)D(3 )in clinical settings is precluded due to its toxicity in vivo. Therefore much effort has been placed in developing relatively non-toxic vitamin D analogs. Recently, with the discovery of the expression of 25-hydroxy vitamin D(3) 1alpha-hydroxylase (CYP27B1) in multiple extrarenal organs, the functional role of prohormone, 25-hydroxyvitamin D(3) [25(OH)D(3)], has been redefined. Since 25(OH)D(3) does not cause hypercalcemia and maintains relative high concentration in serum, it is possible that the prohormone can be converted to active hormone in mammary epithelial cells to provide chemopreventive effects. In the present study, we evaluated its functional significance using mouse mammary organ culture (MMOC) system. We first showed that 25(OH)D(3) 1alpha-hydroxylase is extensively expressed in mammary ductal epithelial cells at both protein and mRNA levels, which is a prerequisite for 25(OH)D(3) to function in an autocrine/paracrine manner. However, we also observed that clotrimazol (1alpha-hydroxylase inhibitor) enhanced 25(OH)D(3) -induced CYP24 expression in breast cancer cells. In mammary glands derived from 1alpha-hydroxylase knockout mice, 25(OH)D(3) treatment in organ culture significantly induced CYP24 expression, indicating a potential direct effect of 25(OH)D(3). In MMOC, 100-250 nM 25(OH)D(3) suppressed both ovarian hormone-dependent and -independent mammary precancerous lesions (induced by DMBA) by more than 50%, while the active hormone 1,25(OH)(2)D(3) (positive control) at 100 nM suppressed alveolar lesions by more than 80%. The inactive vitamin D(3) (negative control) at 100 nM suppressed alveolar lesions by only 20% (P>0.05). We found that 25(OH)D(3) inhibits DMBA-induced mammary alveolar lesions (MAL) in a stage-specific manner: 25(OH)D(3) mainly inhibits the promotion stage of lesion formation. We conclude that 25(OH)D(3) could serve as a non-toxic natural chemopreventive agent for further development for breast cancer prevention.