calcitriol and Colonic-Neoplasms

Epidemiological studies have demonstrated a high incidence of colonic tumors in populations living in areas of low sunlight exposure. This suggests 1,25-dihydroxyvitamin D3, an antimitotic prodifferentiating steroid hormone, as a potentially preventive factor since levels of the precursor 25-hydroxyvitamin D3 in serum are, to a major part, dependent upon sun exposure. Conversion into the active metabolite from the precursor is effected by CYP27B1, and degradation by CYP24. Both p450 hydroxylases are known to be located in the kidney. However, we were able to demonstrate presence, and activity of both enzymes also in the colon. We have shown also that during early tumor progression expression of CYP27B1 and of the vitamin D receptor is upregulated. Therefore the vitamin D system may function as a potent physiological defense against further tumor progression in cancer patients. We suggest that estrogenic substances, and also phytoestrogens present in soy food could, by increasing tumor tissue-located CYP27B1 activity and decreasing degradative CYP24 activity, augment tumor-localized 1,25-dihydroxyvitamin D3 levels and activity.

Topics: 25-Hydroxyvitamin D3 1-alpha-Hydroxylase; Animals; Colon; Colonic Neoplasms; Cytochrome P-450 Enzyme System; Estrogens; Gene Expression Regulation; Humans; Isoflavones; Phytoestrogens; Plant Preparations; Receptors, Estrogen; Vitamin D

1,25-dihydroxyvitamin D3[1,25(OH)2D3] is a well-known potent regulator of cell growth and differentiation and there is recent evidence of an effect on cell death, tumour invasion and angiogenesis, which makes it a candidate agent for cancer regulation. The classical synthetic pathway of 1,25(OH)2D3 involves 25- and 1 alpha-hydroxylation of vitamin D3, in the liver and kidney, respectively, of absorbed or skin-synthesized vitamin D3. There is recent focus on the importance in growth control of local metabolism of 1,25(OH)2D3, which is a function of local tissue synthetic hydroxylases and particularly the principal catabolizing enzyme, 24-hydroxylase. The classical signalling pathway of 1,25(OH)2D3 employs the vitamin D nuclear receptor (VDR), which is a transcription factor for 1,25(OH)2D3 target genes. Effects of this pathway include inhibition of cellular growth and invasion. Cytoplasmic signalling pathways are increasingly being recognized, which similarly may regulate growth and differentiation but also apoptosis. 1,25(OH)2D3 has a major inhibitory effect on the G1/S checkpoint of the cell cycle by upregulating the cyclin dependent kinase inhibitors p27 and p21, and by inhibiting cyclin D1. Indirect mechanisms include upregulation of transforming growth factor-beta and downregulation of the epidermal growth factor receptor. 1,25(OH)2D3 may induce apoptosis either indirectly through effects on the insulin-like growth receptor and tumour necrosis factor-alpha or more directly via the Bcl-2 family system, the ceramide pathway, the death receptors (e.g. Fas) and the stress-activated protein kinase pathways (Jun N terminal kinase and p38). Inhibition of tumour invasion and metastasis potential has been demonstrated and mechanisms include inhibition of serine proteinases, metalloproteinases and angiogenesis. The lines of evidence for an effect of vitamin D3 in systemic cancer are the laboratory demonstration of relevant effects on cellular growth, differentiation, apoptosis, malignant cell invasion and metastasis; epidemiological findings of an association of the occurrence and outcome of cancers with derangements of vitamin D3/1,25(OH)2D3 and the association of functional polymorphisms of the VDR with the occurrence of certain cancers. In addition, vitamin D3 analogues are being developed as cancer chemotherapy agents. There is accumulating evidence that the vitamin D3/1,25(OH)2D3/VDR axis is similarly important in malignant melanoma (MM). MM cells express

Topics: Breast Neoplasms; Cell Differentiation; Cell Division; Cholecalciferol; Colonic Neoplasms; Female; Humans; Male; Melanoma; Polymorphism, Genetic; Prostatic Neoplasms; Receptors, Calcitriol; Signal Transduction; Skin; Skin Neoplasms; Vitamin D

Epidemiological studies suggest an inverse correlation between dietary calcium (Ca(2+)) and vitamin D intake and the risk of colorectal cancer (CRC). It has been shown in vitro that the active vitamin D metabolite, 1,25-dihydroxyvitamin D3 (1,25-D3) can upregulate expression of the calcium-sensing receptor (CaSR). In the colon, CaSR has been suggested to regulate proliferation of colonocytes. However, during tumorigenesis colonic CaSR expression is downregulated and we hypothesized that the loss of CaSR could influence the anti-tumorigenic effects of Ca(2+) and vitamin D. Our aim was to assess the impact of CaSR expression and function on the anti-neoplastic effects of 1,25-D3 in colon cancer cell lines. We demonstrated that in the healthy colon of mice, high vitamin D diet (2500 IU/kg diet) increased expression of differentiation and apoptosis markers, decreased expression of proliferation markers and significantly upregulated CaSR mRNA expression, compared with low vitamin D diet (100 IU/kg diet). To determine the role of CaSR in this process, we transfected Caco2-15 and HT29 CRC cells with wild type CaSR (CaSR-WT) or a dominant negative CaSR mutant (CaSR-DN) and treated them with 1,25-D3 alone, or in combination with CaSR activators (Ca(2+) and NPS R-568). 1,25-D3 enhanced the anti-proliferative effects of Ca(2+) and induced differentiation and apoptosis only in cells with a functional CaSR, which were further enhanced in the presence of NPS R-568, a positive allosteric modulator of CaSR. The mutant CaSR inhibited the anti-tumorigenic effects of 1,25-D3 suggesting that the anti-neoplastic effects of 1,25-D3 are, at least in part, mediated by the CaSR. Taken together, our data provides molecular evidence to support the epidemiological observation that both, vitamin D and calcium are needed for protection against malignant transformation of the colon and that their effect is modulated by the presence of a functional CaSR. This article is part of a Special Issue entitled '17th Vitamin D Workshop'.

Topics: Adenocarcinoma; Aniline Compounds; Animals; Caco-2 Cells; Calcium; Cell Differentiation; Cell Proliferation; Cell Transformation, Neoplastic; Colon; Colonic Neoplasms; Dietary Supplements; Gene Expression Regulation, Neoplastic; HT29 Cells; Humans; Male; Mice; Mice, Transgenic; Mutation; Phenethylamines; Propylamines; Receptors, Calcium-Sensing; Receptors, G-Protein-Coupled; RNA, Messenger; Signal Transduction; Transfection; Vitamin D

Colorectal carcinoma (CRC) is the third most common cancer in developed countries. A large fraction of cases are linked to chronic intestinal inflammation, with concomitant increased TNF-α release and elevated Snail1/Snail2 levels. These transcription factors in turn suppress vitamin D receptor (VDR) expression, resulting in loss of responsiveness to the protective anti-proliferative and anti-migratory effects of 1,25-dihydroxyvitamin D (1,25D). Experimental and epidemiologic evidence support the use of natural products to target CRC. Here we show that the flavonolignan silibinin reverses the TNF-α-induced upregulation of Snail1 and Snail2 in the 1,25D-resistant human colon carcinoma cells HT-29. These silibinin effects are accompanied by an increase in VDR levels; Snail1 overexpression reverses these silibinin effects. Silibinin also restores promoter activity from a vitamin D-response element (VDRE) reporter construct. While 1,25D had no significant effect on HT-29 and SW480-R cell proliferation and migration, co-treatment with silibinin restored 1,25D responsiveness. In addition, co-treatment with silibinin plus 1,25D decreased proliferation and migration at doses where silibinin alone had no effect. These findings demonstrate that this combination may present a novel approach to target CRC in conditions of chronic colonic inflammation.

Topics: Antineoplastic Combined Chemotherapy Protocols; Cell Movement; Cell Proliferation; Colonic Neoplasms; Drug Synergism; HT29 Cells; Humans; Receptors, Calcitriol; Retinoid X Receptor alpha; Silybin; Silymarin; Snail Family Transcription Factors; Transcription Factors; Tumor Necrosis Factor-alpha; Vitamin D

Oxidative catabolism of 1α,25-dihydroxyvitamin D(3) [1α,25(OH)(2)D(3)] is mediated by either CYP24A1 or CYP3A4. In this paper, we tested whether induction of CYP3A4 in the LS180 intestinal cell model enhances clearance of 1α,25(OH)(2)D(3) and blunts its hormonal effect on expression of the apical membrane calcium transport protein, TRPV6. Treatment with the hPXR agonist rifampin significantly increased CYP3A4 mRNA content and catalytic activity, but had no effect on CYP24A1 or TRPV6 mRNA content. Pre-treating cells with rifampin for 48h, prior to a 24h 1α,25(OH)(2)D(3) treatment phase, was associated with a subsequent 48% increase in the elimination of 1α,25(OH)(2)D(3) and a 35% reduction of peak TRPV6 mRNA. Introduction of the CYP3A4 inhibitor, 6',7'-dihydroxybergamottin, an active inhibitor in grapefruit juice, reversed the effects of rifampin on 1α,25(OH)(2)D(3) clearance and TRPV6 expression. Over-expression of hPXR in LS180 cells greatly enhanced the CYP3A4 responsiveness to rifampin pretreatment, and elicited a greater relative suppression of TRPV6 expression and an increase in 1α,25(OH)(2)D(3) disappearance rate, compared to vector expressed cells, following hormone administration. Together, these results suggest that induction of CYP3A4 in the intestinal epithelium by hPXR agonists can result in a greater metabolic clearance of 1α,25(OH)(2)D(3) and reduced effects of the hormone on the intestinal calcium absorption, which may contribute to an increased risk of drug-induced osteomalacia/osteoporosis in patients receiving chronic therapy with potent hPXR agonists. Moreover, ingestion of grapefruit juice in the at-risk patients could potentially prevent this adverse drug effect.

Topics: Adenocarcinoma; Caco-2 Cells; Calcium; Cell Line, Tumor; Colonic Neoplasms; Cytochrome P-450 CYP3A; Dose-Response Relationship, Drug; Enzyme Induction; Humans; Pregnane X Receptor; Receptors, Steroid; Rifampin; Vitamin D

We designed by docking and synthesized two novel analogues of 1α,25-dihydroxyvitamin D(3) hydroxymethylated at C-26 (2 and 3). The syntheses were carried out by the convergent Wittig-Horner approach via epoxide 12a as a common key intermediate. The antiproliferative and transactivation potency of the compounds was evaluated in colon and breast cancer cell lines. The analogues showed a similar but reduced activity compared to 1,25(OH)(2)D(3). Analogue 3 was more potent than analogue 2, and in some assays it exhibited potency similar to that of the natural ligand.

Topics: Animals; Antineoplastic Agents; Breast Neoplasms; Cell Line, Tumor; Cell Proliferation; Chlorocebus aethiops; Cholecalciferol; Colonic Neoplasms; COS Cells; Drug Design; Female; Humans; Ligands; Protein Binding; Receptors, Calcitriol

The Wnt/beta-catenin signalling pathway is activated in 90% of human colon cancers by nuclear accumulation of beta-catenin protein due to its own mutation or to that of adenomatous polyposis coli. In the nucleus, beta-catenin regulates gene expression promoting cell proliferation, migration and invasiveness. 1alpha,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) inhibits beta-catenin signalling by inducing its binding to vitamin D receptor (VDR) and by promoting beta-catenin nuclear export. The transcription factor Snail1 represses VDR expression and we demonstrate here that Snail1 also abolishes the nuclear export of beta-catenin induced by 1,25(OH)(2)D(3) in SW480-ADH cells. Accordingly, Snail1 relieves the inhibition exerted by 1,25(OH)(2)D(3) on genes whose expression is driven by beta-catenin, such as c-MYC, ectodermal-neural cortex-1 (ENC-1) or ephrin receptor B2 (EPHB2). In addition, Snail1 abrogates the inhibitory effect of 1,25(OH)(2)D(3) on cell proliferation and migration. In xenografted mice, Snail1 impedes the nuclear export of beta-catenin and the inhibition of ENC-1 expression induced by EB1089, a 1,25(OH)(2)D(3) analogue. The elevation of endogenous SNAIL1 protein levels reproduces the effect of an ectopic Snail1 gene. Remarkably, the expression of exogenous VDR in cells with high levels of Snail1 normalizes the transcriptional responses to 1,25(OH)(2)D(3). However, this exogenous VDR failed to fully restore the blockage of the Wnt/beta-catenin pathway by 1,25(OH)(2)D(3). This suggests that the effects of Snail1 on this pathway are not merely due to the repression of VDR gene. We conclude that Snail1 is a positive regulator of the Wnt/beta-catenin signalling pathway in part through the abrogation of the inhibitory action of 1,25(OH)(2)D(3).

Topics: Animals; beta Catenin; Calcitriol; Cell Line, Tumor; Cell Movement; Cell Proliferation; Colonic Neoplasms; Female; Humans; Mice; Mice, SCID; Microfilament Proteins; Neoplasm Transplantation; Neuropeptides; Nuclear Proteins; Receptors, Calcitriol; Signal Transduction; Snail Family Transcription Factors; Transcription Factors; Vitamin D; Wnt Proteins

Vitamin D receptor (VDR) ligands are therapeutic agents for the treatment of psoriasis, osteoporosis, and secondary hyperparathyroidism. VDR ligands also show immense potential as therapeutic agents for autoimmune diseases and cancers of skin, prostate, colon, and breast as well as leukemia. However, the major side effect of VDR ligands that limits their expanded use and clinical development is hypercalcemia that develops as a result of the action of these compounds mainly on intestine. In order to discover VDR ligands with less hypercalcemia liability, we sought to identify tissue-selective VDR modulators (VDRMs) that act as agonists in some cell types and lack activity in others. Here, we describe LY2108491 and LY2109866 as nonsecosteroidal VDRMs that function as potent agonists in keratinocytes, osteoblasts, and peripheral blood mononuclear cells but show poor activity in intestinal cells. Finally, these nonsecosteroidal VDRMs were less calcemic in vivo, and LY2108491 exhibited more than 270-fold improved therapeutic index over the naturally occurring VDR ligand 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] in an in vivo preclinical surrogate model of psoriasis.

Topics: Acetates; Animals; Arylsulfonates; Caco-2 Cells; Calcitriol; Cell Proliferation; Cells, Cultured; Colonic Neoplasms; Dose-Response Relationship, Drug; Drug Evaluation, Preclinical; Female; Humans; Hypercalcemia; Intestines; Keratinocytes; Ligands; Mice; Mice, Hairless; Mice, Inbred C57BL; Mice, Inbred Strains; Models, Biological; Osteoblasts; Psoriasis; Rats; Receptors, Calcitriol; Signal Transduction; Species Specificity; Thiophenes; Transcription, Genetic; Tumor Cells, Cultured; Vitamin D

1alpha,25-Dihydroxyvitamin D3 (1alpha,25(OH)2D3) has antitumor activity in addition to its classical action on calcium metabolism and bone tissue biology. It is thought to regulate the expression of multiple target genes and thus modulate processes critical for tumor growth and metastases. Here we show that 1alpha,25(OH)2D3 differentially regulates the expression of Id1 and Id2 genes, members of a family of transcriptional regulators of cell proliferation and differentiation. 1alpha,25(OH)2D3 induced epithelial differentiation in SW480-ADH human colon carcinoma cell line by promoting expression of the proteins implicated in adherent junction formation, including E-cadherin, and by inhibiting beta-catenin transcriptional activity. 1alpha,25(OH)2D3 activated the human Id1 gene promoter and rapidly induced Id1 RNA and protein. Ectopic overexpression of Id1 was not sufficient to induce E-cadherin, which was critical for the morphological changes induced by 1alpha,25(OH)2D3 in SW480-ADH cells. Conversely, Id2 transcription rate, RNA and protein levels were decreased by 1alpha,25(OH)2D3. Id2 downregulation by 1alpha,25(OH)2D3 mediated the antiproliferative effect of 1alpha,25(OH)2D3 on SW480-ADH cells. In addition, we showed that 1alpha,25(OH)2D3 changed the levels of the inducer of angiogenesis, vascular endothelial growth factor and the potent antiangiogenic factor thrombospondin-1, leading to a balanced change in the angiogenic potential of SW480-ADH human colon carcinoma cells.

Topics: Animals; beta Catenin; Cadherins; Carcinoma; Cell Proliferation; Colonic Neoplasms; Cytoskeletal Proteins; DNA-Binding Proteins; Gene Expression Regulation, Neoplastic; Humans; Inhibitor of Differentiation Protein 1; Inhibitor of Differentiation Protein 2; Mice; Mice, Inbred C57BL; Neovascularization, Pathologic; Promoter Regions, Genetic; Repressor Proteins; Trans-Activators; Transcription Factors; Tumor Cells, Cultured; Vitamin D

While Vitamin D insufficiency in the US and European population is rising, epidemiological studies suggest an inverse correlation between low serum levels of 25-hydroxyvitamin D(3) (25-OH-D(3)) and colorectal cancer incidence. The antimitotic, prodifferentiating and proapoptotic active metabolite 1alpha,25-dihydroxyvitamin D(3) (1,25-(OH)(2)-D(3)) is synthesized also by colonocytes, since these possess Vitamin D synthesizing (CYP27B1) and catabolic (CYP24) hydroxylases similar to the kidney. Early during colon tumor progression, expression of CYP27B1 and of the Vitamin D receptor increases, suggesting an autocrine/paracrine growth control in colon tissue as a physiological restriction against tumor progression. However, in human adenocarcinomas expression of the catabolic CYP24 is also enhanced when compared with adjacent normal mucosa. Therefore, to maintain colonic accumulation of 1,25-(OH)(2)-D(3) its catabolism needs to be restricted. Our studies in mice show that low nutritional calcium causes hyperproliferation of colon crypts and significant elevation of CYP24 expression, which can be completely abrogated by soy feeding. We suggest that phytoestrogens in soy, known to be estrogen receptor modulators, are responsible for decreased CYP24 expression. These results and our observation that 17beta-estradiol can elevate CYP27B1 expression in rectal tissue of postmenopausal women, may underlie the observed protective effect of estrogens against colorectal cancer in females.

Topics: 25-Hydroxyvitamin D3 1-alpha-Hydroxylase; Calcium; Cell Line, Tumor; Chromatography, High Pressure Liquid; Colonic Neoplasms; Endocrine System; Gastrointestinal Tract; Gene Expression Regulation; Humans; Receptors, Calcitriol; RNA, Messenger; Steroid Hydroxylases; Tumor Cells, Cultured; Vitamin D; Vitamin D3 24-Hydroxylase