CYP27A1 and CYP24 expression as a function of malignant transformation in the colon

Vitamin D and cancer

The role of vitamin D in the prevention of chronic diseases including cancer, has received a great deal of attention during the past few decades. The term "Cancer" represents multiple disease states with varying biological complexities. The strongest link between vitamin D and cancer is provided by ecological and studies like observational, in preclinical models. It is apparent that vitamin D exerts diverse biological responses in a tissue specific manner. Moreover, several human factors could affect bioactivity of vitamin D. The mechanism(s) underlying vitamin D initiated anti-carcinogenic effects are diverse and includes changes at the muti-system levels. The oncogenic environment could easily corrupt the traditional role of vitamin D or could ensure resistance to vitamin D mediated responses. Several researchers have identified gaps in our knowledge pertaining to the role of vitamin D in cancer. Further areas are identified to solidify the role of vitamin D in cancer control strategies.

Mutant APC reshapes Wnt signaling plasma membrane nanodomains by altering cholesterol levels via oncogenic β-catenin

Although the role of the Wnt pathway in colon carcinogenesis has been described previously, it has been recently demonstrated that Wnt signaling originates from highly dynamic nano-assemblies at the plasma membrane. However, little is known regarding the role of oncogenic APC in reshaping Wnt nanodomains. This is noteworthy, because oncogenic APC does not act autonomously and requires activation of Wnt effectors upstream of APC to drive aberrant Wnt signaling. Here, we demonstrate the role of oncogenic APC in increasing plasma membrane free cholesterol and rigidity, thereby modulating Wnt signaling hubs. This results in an overactivation of Wnt signaling in the colon. Finally, using the Drosophila sterol auxotroph model, we demonstrate the unique ability of exogenous free cholesterol to disrupt plasma membrane homeostasis and drive Wnt signaling in a wildtype APC background. Collectively, these findings provide a link between oncogenic APC, loss of plasma membrane homeostasis and CRC development.

The tumor-repressing effect of CYP27A1 on renal cell carcinoma by 27-HC arising from cholesterol metabolism

As a key approach to mediate cholesterol metabolism, the role of the CYP27A1/27-HC axis in renal cell carcinoma (RCC) remains unclear. Analysis of CYP27A1 expression from public databases and metastatic cases in our center suggested that CYP27A1 was obviously downregulated in RCC tissues, and survival analysis further showed its correlation with favorable clinicopathological features and prognosis. In vitro, up and downregulation of CYP27A1 expression in RCC cell lines could definitely illustrate its anticipation involving apoptosis, proliferation, invasion, migration, and clonality. This could be achieved through upregulation of 27-HC concentration, which mediates the activation of signaling pathways of apoptosis and cell cycle arrest. Further, recovery of CYP27A1 expression could definitely inhibit the proliferation of RCC tumors in vivo. This is the first study to explore the role of the CYP27A1/27-HC axis in RCC. Attempts to maintain the normal function of the axis may be a potential strategy in the treatment of RCC, and the predictive value of CYP27A1 detection on the efficacy of targeted therapy in metastatic RCC is also worthy of attention.

Vitamin D resistant genes - promising therapeutic targets of chronic diseases

Vitamin D is an essential vitamin indispensable for calcium and phosphate metabolism, and its deficiency has been implicated in several extra-skeletal pathologies, including cancer and chronic kidney disease. Synthesized endogenously in the layers of the skin by the action of UV-B radiation, the vitamin maintains the integrity of the bones, teeth, and muscles and is involved in cell proliferation, differentiation, and immunity. The deficiency of Vit-D is increasing at an alarming rate, with nearly 32% of children and adults being either deficient or having insufficient levels. This has been attributed to Vit-D resistant genes that cause a reduction in circulatory Vit-D levels through a set of signaling pathways. CYP24A1, SMRT, and SNAIL are three genes responsible for Vit-D resistance as their activity either lowers the circulatory levels of Vit-D or reduces its availability in target tissues. The hydroxylase CYP24A1 inactivates analogs and prohormonal and/or hormonal forms of calcitriol. Elevation of the expression of CYP24A1 is the major cause of exacerbation of several diseases. CYP24A1 is rate-limiting, and its induction has been correlated with increased prognosis of diseases, while loss of function mutations cause hypersensitivity to Vit-D. The silencing mediator of retinoic acid and thyroid hormone receptor (SMRT) and its corepressor are involved in the transcriptional repression of VDR-target genes. SNAIL1 (SNAIL), SNAIL2 (Slug), and SNAIL3 (Smuc) are involved in transcriptional repression and binding to histone deacetylases and methyltransferases in addition to recruiting polycomb repressive complexes to the target gene promoters. An inverse relationship between the levels of calcitriol and the epithelial-to-mesenchymal transition is reported. Studies have demonstrated a strong association between Vit-D deficiency and chronic diseases, including cardiovascular diseases, diabetes, cancers, autoimmune diseases, infectious diseases, etc. Vit-D resistant genes associated with the aforementioned chronic diseases could serve as potential therapeutic targets. This review focuses on the basic structures and mechanisms of the repression of Vit-D regulated genes and highlights the role of Vit-D resistant genes in chronic diseases.

Is Vitamin D Deficiency Related to Increased Cancer Risk in Patients with Type 2 Diabetes Mellitus?

There is mounting evidence that type 2 diabetes mellitus (T2DM) is related with increased risk for the development of cancer. Apart from shared common risk factors typical for both diseases, diabetes driven factors including hyperinsulinemia, insulin resistance, hyperglycemia and low grade chronic inflammation are of great importance. Recently, vitamin D deficiency was reported to be associated with the pathogenesis of numerous diseases, including T2DM and cancer. However, little is known whether vitamin D deficiency may be responsible for elevated cancer risk development in T2DM patients. Therefore, the aim of the current review is to identify the molecular mechanisms by which vitamin D deficiency may contribute to cancer development in T2DM patients. Vitamin D via alleviation of insulin resistance, hyperglycemia, oxidative stress and inflammation reduces diabetes driven cancer risk factors. Moreover, vitamin D strengthens the DNA repair process, and regulates apoptosis and autophagy of cancer cells as well as signaling pathways involved in tumorigenesis i.e., tumor growth factor β (TGFβ), insulin-like growth factor (IGF) and Wnt-β-Cathenin. It should also be underlined that many types of cancer cells present alterations in vitamin D metabolism and action as a result of Vitamin D Receptor (VDR) and CYP27B1 expression dysregulation. Although, numerous studies revealed that adequate vitamin D concentration prevents or delays T2DM and cancer development, little is known how the vitamin affects cancer risk among T2DM patients. There is a pressing need for randomized clinical trials to clarify whether vitamin D deficiency may be a factor responsible for increased risk of cancer in T2DM patients, and whether the use of the vitamin by patients with diabetes and cancer may improve cancer prognosis and metabolic control of diabetes.

Association between histone deacetylase activity and vitamin D-dependent gene expressions in relation to sulforaphane in human colorectal cancer cells

BACKGROUND

It is relatively unknown as to how dietary bioactive compound sulforaphane (SFN) and vitamin D regulate gene expression in colorectal cancer. We hypothesized that a combination of SFN with vitamin D would prove beneficial in colorectal cancer. A combinatorial chemo-preventive strategy was employed to investigate the impact of SFN on chromatin remodeling in colorectal carcinoma. To understand the epigenetics-mediated changes in gene expression in response to SFN and vitamin D, Caco-2 cells were exposed for 24 h to vitamin D (100 nmol L^-1 ) either alone or in combination with SFN and trichostatin A (20 and 1 μmol L^-1 , respectively) at 70% confluency (proliferating) and after 13 days post-confluency (fully differentiated). Changes to VDR, CYP24A1, CYP27B1 and TRPV6 gene expressions were quantified using real-time PCR-based assays. Histone deacetylase (HDAC) inhibitor activity was assessed using HDAC I/II assay that measured global changes in acetylation status.

RESULTS

In differentiated Caco-2 cells, none of the genes had significant changes from D alone group. D + SFN (P = 0.99) demonstrated an opposing effect from D alone and decreased VDR expression. However, in proliferating Caco-2 cells, D + SFN (P < 0.04) increased VDR expression and decreased CYP27B1 (P < 0.01) more than D alone (P = 0.38 and 0.07, respectively). Although statistically significant, D + SFN (P = 0.01) effect on HDAC inhibitor activity was less than trichostatin A alone group (P < 0.0004) or SFN alone group (P < 0.0014).

CONCLUSIONS

The data suggest that colon cancer cells respond to dietary components differently under different conditions. The effect of vitamin D and SFN is selective and gene-specific in the complex multistep process of colorectal carcinogenesis in vitro. © 2020 Society of Chemical Industry.

Circulating 27-hydroxycholesterol and Risk of Colorectal Adenomas and Serrated Polyps

The oxysterol 27-hydroxycholesterol (27-OHC) is an endogenous selective estrogen receptor modulator implicated in breast cancer etiology. It is unknown whether circulating 27-OHC is associated with colorectal neoplasia risk. Circulating 27-OHC was measured using LC/MS in fasting plasma collected at baseline from participants of the Vitamin D/Calcium Polyp Prevention Study, a completed randomized clinical trial. Participants were between 45 and 75 years old, recently diagnosed with ≥1 colorectal adenoma, and followed for new colorectal polyps during colonoscopic surveillance. Adjusted risk ratios (RR) with 95% confidence intervals (CI) of new colorectal polyps were estimated for quartiles of circulating 27-OHC using log-linear regression for repeated outcomes. Polyp phenotypes included any adenomas, advanced adenomas, hyperplastic polyps, and sessile serrated adenomas/polyps. Circulating 27-OHC was measured at baseline for 1,246 participants. Compared with participants with circulating 27-OHC below the first quartile (<138 ng/mL), those with circulating 27-OHC at or above the fourth quartile (≥201 ng/mL) had 24% higher risk of adenomas (RR, 1.24; 95% CI, 1.05-1.47) and 89% higher risk of advanced adenomas (RR, 1.89; 95% CI, 1.17-3.06). Stronger associations were observed among participants with advanced adenomas at baseline. Circulating 27-OHC was not associated with risk of hyperplastic polyps (RR, 0.90; 95% CI, 0.66-1.22) or sessile serrated adenomas/polyps (RR, 1.02; 95% CI, 0.50-2.07). Circulating 27-OHC may be a risk factor for colorectal adenomas but not serrated polyps. PREVENTION RELEVANCE: This study found that plasma concentration of 27-hydroxycholesterol, a metabolite of cholesterol that regulates lipid metabolism and acts as a selective estrogen receptor modulator, is associated with the risk of developing precursor lesions for colorectal cancer.

Functional effects of vitamin D: From nutrient to immunomodulator

Vitamin D can be obtained from the endogenous synthesis in the epidermis by exposure to UVB light, and from foods and supplements in the form of ergocalciferol (vitamin D₂) and cholecalciferol (vitamin D₃). The main metabolite used to measure vitamin D serum status is calcidiol [25(OH)D]. However, its active metabolite calcitriol [1α,25(OH)₂D] performs pleiotropic effects in the cardiovascular, neurological, and adipose tissue as well as immune cells. Calcitriol exerts its effects through genomic mechanisms modulated by the nuclear vitamin D receptor (VDR)/retinoid X receptor (RXR) complex, to bind to vitamin D response elements (VDRE) in target genes of several cells such as activated T and B lymphocytes, neutrophils, macrophages, and dendritic cells; besides of its genomic mechanisms, VDR performs novel non-genomic mechanisms that involve its membrane expression and soluble form; highlighting that vitamin D could be an immunomodulatory nutrient that plays a key role during physiological and pathological events. Therefore, the aim of this comprehensive literature review was to describe the most relevant findings of vitamin D dietary sources, absorption, synthesis, metabolism, and factors that influence its serum status, signaling pathways, and biological effects of this immunonutrient in the health and disease.

The role of vitamin D in head and neck cancer

OBJECTIVE

Head and neck squamous cell carcinoma (HNSCC) describes a set of malignancies of the head and neck that continue to inflict considerable morbidity and mortality. Because HNSCC often presents at an advanced stage, patients frequently undergo intensive multi-modal therapy with an intent to cure. Vitamin D is a precursor to the biologically active hormone calcitriol which governs bone and calcium physiology that is obtained from diet and UV-B exposure. Vitamin D is known to have pleiotropic effects on health and disease. In this review, we examine the role of vitamin D in cancer with emphasis on HNSCC and discuss potential avenues for further research that might better elucidate the role of vitamin D in the management of HNSCC.

REVIEW METHODS

A review of MEDLINE database indexed literature concerning the role and biology of vitamin D in HNSCC was conducted, with special consideration of recently published work and research involving immunobiology and HNSCC.

CONCLUSIONS

The available evidence suggests that vitamin D may play a role in protecting against HNSCC, particularly in persons who smoke, although conflicting and limited data exists. Promising initial work encourages the pursuit of further study.

IMPLICATIONS FOR PRACTICE

The significant morbidity and mortality that HNSCC brings warrants continued research in available and safe interventions that improve patient outcomes. With the rise of immunotherapy as an effective modality for treatment, continued research of vitamin D as an adjunct in the treatment of HNSCC is supported.

Dysregulation of vitamin D synthesis pathway genes in colorectal cancer: A case-control study

Background

The cytochromes P450 are a superfamily of enzymes that control the synthesis of the biologically active form of vitamin D, 1,25‐dihydroxyvitamin D3. These enzymes contribute to the formation of 1,25‐dihydroxyvitamin D3, which starts with a 25‐hydroxylation by CYP2R1 and CYP27A1 and a subsequent 1α‐hydroxylation via CYP27B1.

Methods

By using quantitative real‐time polymerase chain reaction (qRT‐PCR), we analyzed the expression ratio of CYP2R1, CYP27A1 and CYP27B1 genes within the vitamin D metabolic pathway in a total of 75 colorectal cancer (CRC) tissues compared to the adjacent tissues. Furthermore, we evaluated the association of CYP27B1 rs4646536 and CYP2R1 rs12794714 and rs10766196 polymorphisms with CRC risk in a total of 490 subjects, including 245 CRC patients and 245 non‐cancer controls. The genotyping was performed using tetra‐primer amplification refractory mutation system polymerase chain reaction (TP‐ARMS–PCR) method.

Results

The results indicated 2.3 and 2.7 upregulation of CYP2R1 and CYP27B1 genes in colorectal cancer tissues compared to the adjacent tissues, respectively. Rs12794714 AG genotype increased the risk of CRC (P = .03). Furthermore, a significant association was observed under the dominant inheritance model (P = .039).

Conclusion

CYP2R1 and CYP27B1 genes were over‐expressed in CRC samples compared to the adjacent control tissues. Furthermore, CYP2R1 rs12794714 variant was associated with the risk of CRC in the studied samples. CYP2R1 rs10766196 and CYP27B1 rs4646536 are not responsible for CYP2R1 and CYP27B1 genes expression alteration, respectively, but CYP2R1 rs12794714 polymorphism may be the reason of CYP2R1 upregulation and increased the risk of CRC.

Exploratory Genome-Wide Interaction Analysis of Nonsteroidal Anti-inflammatory Drugs and Predicted Gene Expression on Colorectal Cancer Risk

BACKGROUND

Regular use of nonsteroidal anti-inflammatory drugs (NSAID) is associated with lower risk of colorectal cancer. Genome-wide interaction analysis on single variants (G × E) has identified several SNPs that may interact with NSAIDs to confer colorectal cancer risk, but variations in gene expression levels may also modify the effect of NSAID use. Therefore, we tested interactions between NSAID use and predicted gene expression levels in relation to colorectal cancer risk.

METHODS

Genetically predicted gene expressions were tested for interaction with NSAID use on colorectal cancer risk among 19,258 colorectal cancer cases and 18,597 controls from 21 observational studies. A Mixed Score Test for Interactions (MiSTi) approach was used to jointly assess G × E effects which are modeled via fixed interaction effects of the weighted burden within each gene set (burden) and residual G × E effects (variance). A false discovery rate (FDR) at 0.2 was applied to correct for multiple testing.

RESULTS

Among the 4,840 genes tested, genetically predicted expression levels of four genes modified the effect of any NSAID use on colorectal cancer risk, including DPP10 (PG×E = 1.96 × 10-4), KRT16 (PG×E = 2.3 × 10-4), CD14 (PG×E = 9.38 × 10-4), and CYP27A1 (PG×E = 1.44 × 10-3). There was a significant interaction between expression level of RP11-89N17 and regular use of aspirin only on colorectal cancer risk (PG×E = 3.23 × 10-5). No interactions were observed between predicted gene expression and nonaspirin NSAID use at FDR < 0.2.

CONCLUSIONS

By incorporating functional information, we discovered several novel genes that interacted with NSAID use.

IMPACT

These findings provide preliminary support that could help understand the chemopreventive mechanisms of NSAIDs on colorectal cancer.

Vitamin D-Induced Molecular Mechanisms to Potentiate Cancer Therapy and to Reverse Drug-Resistance in Cancer Cells

Increasing interest in studying the role of vitamin D in cancer has been provided by the scientific literature during the last years, although mixed results have been reported. Vitamin D deficiency has been largely associated with various types of solid and non-solid human cancers, and the almost ubiquitous expression of vitamin D receptor (VDR) has always led to suppose a crucial role of vitamin D in cancer. However, the association between vitamin D levels and the risk of solid cancers, such as colorectal, prostate and breast cancer, shows several conflicting results that raise questions about the use of vitamin D supplements in cancer patients. Moreover, studies on vitamin D supplementation do not always show improvements in tumor progression and mortality risk, particularly for prostate and breast cancer. Conversely, several molecular studies are in agreement about the role of vitamin D in inhibiting tumor cell proliferation, growth and invasiveness, cell cycle arrest and inflammatory signaling, through which vitamin D may also regulate cancer microenvironment through the activation of different molecular pathways. More recently, a role in the regulation of cancer stem cells proliferation and short non-coding microRNA (miRNAs) expression has emerged, conferring to vitamin D a more crucial role in cancer development and progression. Interestingly, it has been shown that vitamin D is able not only to potentiate the effects of traditional cancer therapy but can even contribute to overcome the molecular mechanisms of drug resistance—often triggering tumor-spreading. At this regard, vitamin D can act at various levels through the regulation of growth of cancer stem cells and the epithelial–mesenchymal transition (EMT), as well as through the modulation of miRNA gene expression. The current review reconsiders epidemiological and molecular literature concerning the role of vitamin D in cancer risk and tumor development and progression, as well as the action of vitamin D supplementation in potentiating the effects of drug therapy and overcoming the mechanisms of resistance often triggered during cancer therapies, by critically addressing strengths and weaknesses of available data from 2010 to 2020.

Serum vitamin D receptor (VDR) levels as a potential diagnostic marker for colorectal cancer

Colorectal cancer (CRC) is one of the leading causes of mortality and morbidity worldwide, and there has been a significant increase in the incidence of CRC in recent decades. Therefore, there is an urgent need to identify blood biomarkers that can be used for early diagnosis. It is not yet clear whether the level of vitamin D and its receptor, vitamin D receptor (VDR), in the blood are helpful factors in the diagnosis of CRC. Therefore, the study focuses on determining the VDR serum level’s contribution and other chemical parameters to the risk of CRC. A total of 189 Saudi participants (66 CRC patients and 123 control patients) aged 20–80 years old were enrolled in this case-control study. A serum sample was collected from each participant, and the levels of VDR and other bone profile tests were determined using ELISA or chemiluminescent assays. P values < 0.05 were considered statistically significant. The results showed a highly significant reduction in the levels of total vitamin D (P < 0.0001), VDR (P < 0.0001), vitamin D₃ (P < 0.05), and calcium (P < 0.0001) in the serum of CRC patients compared to the controls. However, the alkaline phosphatase level was higher in CRC patients compared to the controls (P < 0.0001). None of the blood markers showed a significant correlation to the progression of CRC (P > 0.05). More investigation is needed to elucidate different physiological processes that can be affected by these blood biomarkers, therefore changing the carcinogenesis of CRC.

Vitamin D-Related Genes, Blood Vitamin D Levels and Colorectal Cancer Risk in Western European Populations

Higher circulating 25-hydroxyvitamin D levels (25(OH)D) have been found to be associated with lower risk for colorectal cancer (CRC) in prospective studies. Whether this association is modified by genetic variation in genes related to vitamin D metabolism and action has not been well studied in humans. We investigated 1307 functional and tagging single-nucleotide polymorphisms (SNPs; individually, and by gene/pathway) in 86 vitamin D-related genes in 1420 incident CRC cases matched to controls from the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. We also evaluated the association between these SNPs and circulating 25(OH)D in a subset of controls. We confirmed previously reported CRC risk associations between SNPs in the VDR, GC, and CYP27B1 genes. We also identified additional associations with 25(OH)D, as well as CRC risk, and several potentially novel SNPs in genes related to vitamin D transport and action (LRP2, CUBN, NCOA7, and HDAC9). However, none of these SNPs were statistically significant after Benjamini-Hochberg (BH) multiple testing correction. When assessed by a priori defined functional pathways, tumor growth factor β (TGFβ) signaling was associated with CRC risk (P ≤ 0.001), with most statistically significant genes being SMAD7 (PBH = 0.008) and SMAD3 (PBH = 0.008), and 18 SNPs in the vitamin D receptor (VDR) binding sites (P = 0.036). The 25(OH)D-gene pathway analysis suggested that genetic variants in the genes related to VDR complex formation and transcriptional activity are associated with CRC depending on 25(OH)D levels (interaction P = 0.041). Additional studies in large populations and consortia, especially with measured circulating 25(OH)D, are needed to confirm our findings.

miR-204 functions as a tumor suppressor gene, at least partly by suppressing CYP27A1 in glioblastoma

Gliomas are the most common type of malignant primary brain tumors in adults and exhibit a spectrum of aberrantly aggressive phenotypes. Despite advances in treatments during past decades, prognosis of the disease remains poor, with a median survival time of 12-14 months. Future studies on the molecular mechanism of the disease may provide the theoretical basis to identify new targets for effective therapies. The present study revealed that in glioblastoma cells, the overexpression of cytochrome P450, family 27, subfamily A, polypeptide 1 (CYP27A1) promoted proliferation, while silencing of CYP27A1 inhibited proliferation, without affecting migration and invasion. CYP27A1 protein was upregulated in glioblastoma tissues, indicating that CYP27A1 is an oncogene. The downregulation of specific microRNAs (miRNA) may contribute to the upregulation of oncogenes in glioblastoma. A common strategy was used to predict target miRNAs of CPY27A1 using the miRanda algorithm. miR-211 and miR-204 could target the 3'untranslated region of CPY27A1 mRNA. Additional studies confirmed that the overexpression of miR-204 inhibited CPY27A1 expression in glioblastoma cells. Finally, it was identified that miR-204 was downregulated in glioblastoma and that its overexpression inhibited proliferation, migration and invasion in glioblastoma cells. Thus, it was concluded that miR-204 functions as a tumor suppressor gene, at least partly by suppressing CYP27A1 in glioblastoma.

Exploring vitamin D metabolism and function in cancer

Vitamin D, traditionally known as an essential nutrient, is a precursor of a potent steroid hormone that regulates a broad spectrum of physiological processes. In addition to its classical roles in bone metabolism, epidemiological, preclinical, and cellular research during the last decades, it revealed that vitamin D may play a key role in the prevention and treatment of many extra-skeletal diseases such as cancer. Vitamin D, as a prohormone, undergoes two-step metabolism in liver and kidney to produce a biologically active metabolite, calcitriol, which binds to the vitamin D receptor (VDR) for the regulation of expression of diverse genes. In addition, recent studies have revealed that vitamin D can also be metabolized and activated through a CYP11A1-driven non-canonical metabolic pathway. Numerous anticancer properties of vitamin D have been proposed, with diverse effects on cancer development and progression. However, accumulating data suggest that the metabolism and functions of vitamin D are dysregulated in many types of cancer, conferring resistance to the antitumorigenic effects of vitamin D and thereby contributing to the development and progression of cancer. Thus, understanding dysregulated vitamin D metabolism and function in cancer will be critical for the development of promising new strategies for successful vitamin D-based cancer therapy.

Complement 5a stimulates macrophage polarization and contributes to tumor metastases of colon cancer

Inflammatory cells such as macrophages can play a pro-tumorigenic role in the tumor stroma. Tumor-associated macrophages (TAMs) generally display an M2 phenotype with tumor-promoting activity; however, the mechanisms regulating the TAM phenotype remain unclear. Complement 5a (C5a) is a cytokine-like polypeptide that is generated during complement system activation and is known to promote tumor growth. Herein, we investigated the role of C5a on macrophage polarization in colon cancer metastasis in mice. We found that deficiency of the C5a receptor (C5aR) severely impairs the metastatic ability of implanted colon cancer cells. C5aR was expressed on TAMs, which exhibited an M2-like functional profile in colon cancer liver metastatic lesions. Furthermore, C5a mediated macrophage polarization and this process relied substantially on activation of the nuclear factor-kappa B (NF-κB) pathway. Finally, analysis of human colon carcinoma indicated that C5aR expression is negatively associated with tumor differentiation grade. Our results demonstrate that C5aR has a central role in regulating the M2 phenotype of TAMs, which in turn, contributes to hepatic metastasis of colon cancer through NF-κB signaling. C5a is a potential novel marker for cancer prognosis and drugs targeting complement system activation, specifically the C5aR pathway, may offer new therapeutic opportunities for colon cancer management.

Extraskeletal actions of vitamin D

The vitamin D receptor (VDR) is found in nearly all, if not all, cells in the body. The enzyme that produces the active metabolite of vitamin D and ligand for VDR, namely CYP27B1, likewise is widely expressed in many cells of the body. These observations indicate that the role of vitamin D is not limited to regulation of bone and mineral homeostasis, as important as that is. Rather, the study of its extraskeletal actions has become the major driving force behind the significant increase in research articles on vitamin D published over the past several decades. A great deal of information has accumulated from cell culture studies, in vivo animal studies, and clinical association studies that confirms that extraskeletal effects of vitamin D are truly widespread and substantial. However, randomized, placebo-controlled clinical trials, when done, have by and large not produced the benefits anticipated by the in vitro cell culture and in vivo animal studies. In this review, I will examine the role of vitamin D signaling in a number of extraskeletal tissues and assess the success of translating these findings into treatments of human diseases affecting those extracellular tissues.

Repression of intestinal transporters and FXR-FGF15 signaling explains bile acids dysregulation in experimental colitis-associated colon cancer

Bile acids (BAs) are important endogenous signaling molecules that play vital roles in the pathological development of various diseases including colitis-associated cancer (CAC). BAs were previously found dysregulated under conditions of CAC; however, the exact patterns and underlying molecular mechanisms remain largely elusive. Based on the development of a method for comprehensive analysis of BAs, this study aims to elucidate the dysregulation patterns and involved mechanisms in a typical CAC model induced by azoxymethane (AOM)/dextran sodium sulfate (DSS). CAC mice showed decreased BAs transformation in gut and glucuronidation in colon, leading to accumulation of primary BAs but reduction of secondary BAs in colon. CAC mice were characterized by an accumulation of BAs in various compartments except ileum, which is in line with repressed ileal FXR-FGF15 feedback signaling and the increased expression of hepatic CYP7A1. The compromised ileal FXR-FGF15 signaling was caused in part by the reduced absorption of FXR ligands including free and tauro-conjungated BAs due to the downregulation of various transporters of BAs in the ileum of CAC mice.

CYP24A1 variant modifies the association between use of oestrogen plus progestogen therapy and colorectal cancer risk

BACKGROUND

Menopausal hormone therapy (MHT) use has been consistently associated with a decreased risk of colorectal cancer (CRC) in women. Our aim was to use a genome-wide gene-environment interaction analysis to identify genetic modifiers of CRC risk associated with use of MHT.

METHODS

We included 10 835 postmenopausal women (5419 cases and 5416 controls) from 10 studies. We evaluated use of any MHT, oestrogen-only (E-only) and combined oestrogen-progestogen (E+P) hormone preparations. To test for multiplicative interactions, we applied the empirical Bayes (EB) test as well as the Wald test in conventional case-control logistic regression as primary tests. The Cocktail test was used as secondary test.

RESULTS

The EB test identified a significant interaction between rs964293 at 20q13.2/CYP24A1 and E+P (interaction OR (95% CIs)=0.61 (0.52-0.72), P=4.8 × 10(-9)). The secondary analysis also identified this interaction (Cocktail test OR=0.64 (0.52-0.78), P=1.2 × 10(-5) (alpha threshold=3.1 × 10(-4)). The ORs for association between E+P and CRC risk by rs964293 genotype were as follows: C/C, 0.96 (0.61-1.50); A/C, 0.61 (0.39-0.95) and A/A, 0.40 (0.22-0.73), respectively.

CONCLUSIONS

Our results indicate that rs964293 modifies the association between E+P and CRC risk. The variant is located near CYP24A1, which encodes an enzyme involved in vitamin D metabolism. This novel finding offers additional insight into downstream pathways of CRC etiopathogenesis.

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.

Vitamin D and Colorectal, Breast, and Prostate Cancers: A Review of the Epidemiological Evidence

Over the past two decades, the question of whether vitamin D has a role in cancer incidence, progression, and mortality has been studied in detail. Colorectal, breast, and prostate cancers have been a particular area of focus; together, these three malignancies account for approximately 35% of cancer cases and 20% of cancer deaths in the United States, and as such are a major public health concern. Herein, we review and synthesize the epidemiological research regarding vitamin D, as measured by the biomarker 25-hydroxycholecalciferol [25(OH)D], and the incidence, progression, and mortality of these cancers. Overall, the results of observational studies of the relationship between 25(OH)D and colorectal cancer have revealed a consistent inverse association for incidence and mortality; while for breast cancer, results have generally demonstrated a relationship between higher 25(OH)D and lower risk for progression and mortality. In contrast, randomized, double-blind clinical trials conducted to date have generally failed to support these findings. For prostate cancer, there is no convincing evidence of an association between 25(OH)D and incidence, and inconsistent data for progression and mortality, though results of one open label clinical trial suggest that supplementation with 4000 IU/d of vitamin D3 may inhibit progression of the disease. Nonetheless, until the results of additional ongoing randomized, double-blind clinical trials are reported, it will be difficult to ascertain if vitamin D itself is related to a reduction in risk for some cancer endpoints, or whether high concentrations of the vitamin D biomarker 25(OH)D may instead serve as a marker for an overall beneficial risk factor profile.

Vitamin D: Metabolism, Molecular Mechanism of Action, and Pleiotropic Effects

1,25-Dihydroxvitamin D3 [1,25(OH)2D3] is the hormonally active form of vitamin D. The genomic mechanism of 1,25(OH)2D3 action involves the direct binding of the 1,25(OH)2D3 activated vitamin D receptor/retinoic X receptor (VDR/RXR) heterodimeric complex to specific DNA sequences. Numerous VDR co-regulatory proteins have been identified, and genome-wide studies have shown that the actions of 1,25(OH)2D3 involve regulation of gene activity at a range of locations many kilobases from the transcription start site. The structure of the liganded VDR/RXR complex was recently characterized using cryoelectron microscopy, X-ray scattering, and hydrogen deuterium exchange. These recent technological advances will result in a more complete understanding of VDR coactivator interactions, thus facilitating cell and gene specific clinical applications. Although the identification of mechanisms mediating VDR-regulated transcription has been one focus of recent research in the field, other topics of fundamental importance include the identification and functional significance of proteins involved in the metabolism of vitamin D. CYP2R1 has been identified as the most important 25-hydroxylase, and a critical role for CYP24A1 in humans was noted in studies showing that inactivating mutations in CYP24A1 are a probable cause of idiopathic infantile hypercalcemia. In addition, studies using knockout and transgenic mice have provided new insight on the physiological role of vitamin D in classical target tissues as well as evidence of extraskeletal effects of 1,25(OH)2D3 including inhibition of cancer progression, effects on the cardiovascular system, and immunomodulatory effects in certain autoimmune diseases. Some of the mechanistic findings in mouse models have also been observed in humans. The identification of similar pathways in humans could lead to the development of new therapies to prevent and treat disease.

CYP24A1 is a potential biomarker for the progression and prognosis of human colorectal cancer

Our study aims to fully evaluate clinicopathological and prognostic values of CYP24A1 in colorectal cancer (CRC) patients. Tissue microarrays of formalin-fixed and paraffin-embedded tumor samples and matched adjacent nontumor colorectal tissues from 99 CRC patients were studied for CYP24A1 protein expression by immunohistochemistry. Messenger RNA expression of CYP24A1 was further evaluated by quantitative real-time polymerase chain reaction in 12 pairs of fresh frozen CRC samples. CYP24A1 expression was significantly higher in CRC tissues compared to corresponding noncancerous tissues. The expression of CYP24A1 protein in CRC was correlated with the depth of tumor invasion (P = .000), lymph node metastasis (P = .030), venous permeation (P = .016), and overall survival (P = .008). A Kaplan-Meier analysis of the CRC patients with high CYP24A1 expression showed significantly reduced overall survival and disease-free survival compared to the patients with low expression (P = 0.026 and .009). A prognostic significance of CYP24A1 was also found in the subgroup of venous permeation condition classification. A multivariate Cox regression analysis showed that CYP24A1 expression was an independent prognostic factor for CRC recurrence (P = .032). In conclusion, CYP24A1 expression is closely associated with CRC progression, and it might be a novel prognostic biomarker for CRC.

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 and male reproduction

Vitamin D is a versatile signalling molecule with a well-established role in the regulation of calcium homeostasis and bone health. The spectrum of vitamin D target organs has expanded and the reproductive role of vitamin D is highlighted by expression of the vitamin D receptor (VDR) and enzymes that metabolize vitamin D in testis, male reproductive tract and human spermatozoa. The expression levels of VDR and CYP24A1 in human spermatozoa serve as positive predictive markers of semen quality, and VDR mediates a nongenomic increase in intracellular calcium concentration that induces sperm motility. Interestingly, functional animal models show that vitamin D is important for estrogen signalling and sperm motility, while cross-sectional studies support the positive association between serum 25-hydroxyvitamin D level and sperm motility in both fertile and infertile men. Expression of VDR and enzymes that metabolize vitamin D in fetal testis indicates a yet unknown role during development, which may be extrapolated from invasive testicular germ cell tumours where 1α,25-dihydroxyvitamin D induces a mesodermal differentiation of the pluripotent testicular cancer cells. Taken together, vitamin D signalling has a positive effect on semen quality, increases estrogen responsiveness and differentiates germ cell tumours. Future studies are needed to determine when 1α,25-dihydroxyvitamin D acts in a paracrine manner and whether systemic changes, which are subject to pharmacological modulation, could influence male reproductive function.

Ex vivo culture of primary human colonic tissue for studying transcriptional responses to 1α,25(OH)2 and 25(OH) vitamin D

1α,25-Dihydroxyvitamin D3 [1α,25(OH)2D3] is a steroid hormone derived from circulating 25(OH) vitamin D [25(OH)D] with chemopreventive effects in colorectal cancer. 1α,25(OH)2D3 acts through transcriptional mechanisms; however, our understanding of vitamin D transcriptional responses in the colon is derived from studies in transformed cancer cell lines which may not represent responses in normal healthy tissue. Here, we describe the optimization of an ex vivo culture model using primary colonic biopsy samples for studying short-term transcriptional response induced by 1α,25(OH)2D3 and 25(OH)D treatment. Colon biopsy samples from healthy subjects were maintained in primary culture and treated in parallel with 100 nM 1α,25(OH)2D3 or 62.5 nM 25(OH)D and vehicle control (ethanol). Viability was assessed using histology and enzymatic assays. Genome-wide transcriptional responses to 1α,25(OH)2D3 were assessed and expression of 25(OH)D targets CYP27B1 and CYP24A1 were measured by real time PCR. We show that ex vivo culture of colonic tissue remains viable for up to 8 h. The largest number of differentially expressed genes in response to 1α,25(OH)2D3 was noted after 6 h (n = 120). As proof of concept, the top upregulated gene was CYP24A1, a well-established vitamin D-responsive gene. With 25(OH)D treatment, mRNA expression of CYP27B1 was significantly increased after 1 h, while expression of CYP24A1 was greatest at 8 h. Ex vivo culture can be used to assess short-term transcriptional responses to 1α,25(OH)2D3 and 25(OH)D in primary tissue from human colon. Future studies will address interindividual differences in transcriptional responses.

Association between circulating concentrations of 25(OH)D and colorectal adenoma: a pooled analysis

The relationship between the biomarker of vitamin D status, 25(OH)D, and the risk for colorectal neoplasia is suggestive but equivocal. Questions remain regarding whether there are differential associations between 25(OH)D and colorectal adenoma by gender, colorectal subsite or features of baseline and recurrent adenomas. We sought to investigate the relationship between 25(OH)D and both baseline and recurrent adenoma characteristics. Our study was conducted among 2,074 participants in a pooled population of two clinical intervention trials of colorectal adenoma recurrence. A cross-sectional analysis of 25(OH)D and baseline adenoma characteristics and a prospective study of recurrent adenomas and their characteristics were conducted. There was a statistically significant inverse association between the concentrations of 25(OH)D and the presence of three or more adenomas at baseline. Compared to participants with 25(OH)D levels of <20 ng/mL, the adjusted odds ratios (ORs) (95% condifdence intervals [CIs]) were 0.99 (0.70-1.41) for those with concentrations of ≥20 and <30 ng/mL, and 0.73 (0.50-1.06) among participants with levels of ≥30 ng/mL (p-trend = 0.05). Baseline villous histology was also significantly inversely related to 25(OH)D levels (p-trend = 0.04). Conversely, 25(OH)D concentrations were not associated with overall colorectal adenoma recurrence, with ORs (95% CIs) of 0.91 (0.71-1.17) and 0.95 (0.73-1.24; p-trend = 0.85). These findings support the concept that the relationship between vitamin D and colorectal neoplasia may vary by stage of adenoma development.

Antineoplastic effects of 1,25(OH)2D3 and its analogs in breast, prostate and colorectal cancer

The active form of vitamin D3, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), is mostly known for its importance in the maintenance of calcium and phosphate homeostasis. However, next to its classical effects on bone, kidney and intestine, 1,25(OH)2D3 also exerts antineoplastic effects on various types of cancer. The use of 1,25(OH)2D3 itself as treatment against neoplasia is hampered by its calcemic side effects. Therefore, 1,25(OH)2D3-derived analogs were developed that are characterized by lower calcemic side effects and stronger antineoplastic effects. This review mainly focuses on the role of 1,25(OH)2D3 in breast, prostate and colorectal cancer (CRC) and the underlying signaling pathways. 1,25(OH)2D3 and its analogs inhibit proliferation, angiogenesis, migration/invasion and induce differentiation and apoptosis in malignant cell lines. Moreover, prostaglandin synthesis and Wnt/b-catenin signaling are also influenced by 1,25(OH)2D3 and its analogs. Human studies indicate an inverse association between serum 25(OH)D3 values and the incidence of certain cancer types. Given the literature, it appears that the epidemiological link between vitamin D3 and cancer is the strongest for CRC, however more intervention studies and randomized placebo-controlled trials are needed to unravel the beneficial dose of 1,25(OH)2D3 and its analogs to induce antineoplastic effects.

A systems biology approach to the global analysis of transcription factors in colorectal cancer

Background

Biological entities do not perform in isolation, and often, it is the nature and degree of interactions among numerous biological entities which ultimately determines any final outcome. Hence, experimental data on any single biological entity can be of limited value when considered only in isolation. To address this, we propose that augmenting individual entity data with the literature will not only better define the entity’s own significance but also uncover relationships with novel biological entities.

To test this notion, we developed a comprehensive text mining and computational methodology that focused on discovering new targets of one class of molecular entities, transcription factors (TF), within one particular disease, colorectal cancer (CRC).

Methods

We used 39 molecular entities known to be associated with CRC along with six colorectal cancer terms as the bait list, or list of search terms, for mining the biomedical literature to identify CRC-specific genes and proteins. Using the literature-mined data, we constructed a global TF interaction network for CRC. We then developed a multi-level, multi-parametric methodology to identify TFs to CRC.

Results

The small bait list, when augmented with literature-mined data, identified a large number of biological entities associated with CRC. The relative importance of these TF and their associated modules was identified using functional and topological features. Additional validation of these highly-ranked TF using the literature strengthened our findings. Some of the novel TF that we identified were: SLUG, RUNX1, IRF1, HIF1A, ATF-2, ABL1, ELK-1 and GATA-1. Some of these TFs are associated with functional modules in known pathways of CRC, including the Beta-catenin/development, immune response, transcription, and DNA damage pathways.

Conclusions

Our methodology of using text mining data and a multi-level, multi-parameter scoring technique was able to identify both known and novel TF that have roles in CRC. Starting with just one TF (SMAD3) in the bait list, the literature mining process identified an additional 116 CRC-associated TFs. Our network-based analysis showed that these TFs all belonged to any of 13 major functional groups that are known to play important roles in CRC. Among these identified TFs, we obtained a novel six-node module consisting of ATF2-P53-JNK1-ELK1-EPHB2-HIF1A, from which the novel JNK1-ELK1 association could potentially be a significant marker for CRC.

Circulating vitamin D and colorectal adenoma in asymptomatic average-risk individuals who underwent first screening colonoscopy: a case-control study

BACKGROUND

A higher circulating vitamin D level is inversely associated with the risk of colorectal cancer, but the association with adenoma risk is less clear.

AIMS

We examined the association between the circulating 25-hydroxyvitamin D(3) [25(OH)D(3)] concentration and colorectal adenoma in asymptomatic average-risk participants undergoing initial screening colonoscopy.

METHODS

The study subjects were comprised of 143 cases of colorectal adenomas and 143 age- and gender-matched controls with normal colonoscopy among the 586 asymptomatic average-risk subjects (median age, 58 years; range, 50-73 years) who underwent first screening colonoscopy and measurement of the serum 25(OH)D(3) between December 2009 and April 2010, consistent with winter months of the region.

RESULTS

The mean concentration of serum 25(OH)D(3) in the adenoma and control groups was 20.0 ± 11.0 ng/ml and 25.0 ± 20.0 ng/ml, respectively (P = 0.009). Using multivariate analysis, higher levels of 25(OH)D(3) were associated with a statistically significant decreased risk of colorectal adenoma after multivariable adjustment (highest vs. lowest quartile OR 0.38, 95% CI 0.18-0.80, P (trend) = 0.012). The inverse association of circulating 25(OH)D(3) with colorectal adenoma was stronger among the patients with proximal adenoma than that among the patients without proximal adenoma (highest vs. lowest quartile OR 0.29, 95% CI 0.13-0.66, P (trend) = 0.001).

CONCLUSIONS

The present study suggests that high levels of circulating vitamin D are associated with a decreased risk of colorectal adenoma, and especially adenoma located in the proximal colon.

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.

Prediagnostic 25-hydroxyvitamin D, VDR and CASR polymorphisms, and survival in patients with colorectal cancer in western European ppulations

BACKGROUND

Individuals with higher blood 25-hydroxyvitamin D [25(OH)D] levels have a lower risk of developing colorectal cancer (CRC), but the influence of 25(OH)D on mortality after CRC diagnosis is unknown.

METHODS

The association between prediagnostic 25(OH)D levels and CRC-specific (N = 444) and overall mortality (N = 541) was prospectively examined among 1,202 participants diagnosed with CRC between 1992 and 2003 in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. Multivariable Cox proportional hazards models were used to calculate HRs and corresponding 95% CIs according to 25(OH)D quintiles and genetic variation within the VDR and CASR genes. Potential dietary, lifestyle, and metabolic effect modifiers were also investigated.

RESULTS

There were 541 deaths, 444 (82%) due to CRC. Mean follow-up was 73 months. In multivariable analysis, higher 25(OH)D levels were associated with a statistically significant reduction in CRC-specific (P(trend) = 0.04) and overall mortality (P(trend) = 0.01). Participants with 25(OH)D levels in the highest quintile had an adjusted HR of 0.69 (95% CI: 0.50-0.93) for CRC-specific mortality and 0.67 (95% CI: 0.50-0.88) for overall mortality, compared with the lowest quintile. Except for a possible interaction by prediagnostic dietary calcium intake (P(interaction) = 0.01), no other potential modifying factors related to CRC survival were noted. The VDR (FokI and BsmI) and CASR (rs1801725) genotypes were not associated with survival.

CONCLUSIONS

High prediagnostic 25(OH)D levels are associated with improved survival of patients with CRC.

IMPACT

Our findings may stimulate further research directed at investigating the effects of blood vitamin D levels before, at, and after CRC diagnosis on outcomes in CRC patients.

Evaluation of vitamin D3 A-ring analogues as Hedgehog pathway inhibitors

A structure-activity relationship study focusing on the A-ring of vitamin D3 (VD3) was undertaken to elucidate its role in inhibiting the Hedgehog pathway and in mediating anti-cancer effects. Analogues resulting from simple functional group substitution at 3' position of VD3 were evaluated in a variety of biological assays to determine their ability to selectively inhibit Hh signaling. Moderately active Hh inhibitors that have insignificant binding affinity for VDR were identified; however, these compounds also activate the traditional VDR pathway, presumably due to metabolites produced in the cultured cells. Thus, further structural modifications to the VD3 scaffold are required to yield potent, selective Hh inhibitors.

Vitamin D resistance and colon cancer prevention

Observational studies have been largely consistent in showing an inverse association between vitamin D and an individual's risk of developing colorectal cancer. Vitamin D protection is further supported by a range of preclinical colon cancer models, including carcinogen, genetic and dietary models. A large number of mechanistic studies in both humans and rodents point to vitamin D preventing cancer by regulating cell proliferation. Counterbalancing this mostly positive data are the results of human intervention studies in which supplemental vitamin D was found to be ineffective for reducing colon cancer risk. One explanation for these discrepancies is the timing of vitamin D intervention. It is possible that colon lesions may progress to a stage where they become unresponsive to vitamin D. Such a somatic loss in vitamin D responsiveness bears the hallmarks of an epigenetic change. Here, we review data supporting the chemopreventive effectiveness of vitamin D and discuss how gene silencing and other molecular changes somatically acquired during colon cancer development may limit the protection that may otherwise be afforded by vitamin D via dietary intervention. Finally, we discuss how understanding the mechanisms by which vitamin D protection is lost might be used to devise strategies to enhance its chemopreventive actions.

Regulation of vitamin D metabolism

Fundamental to understanding the way in which perturbations in the vitamin D endocrine system can affect human health is an appreciation of the steps involved in the production of the well-recognized active hormonal form, 1,25-dihydroxyvitamin D(3). Thus this paper focuses first on the nature and regulation of the two enzymes responsible for the production of 1,25-dihydroxyvitamin D(3), the 25-hydroxylase in the liver and the 1α-hydroxylase in the kidney. The most important regulators of the 1α-hydroxylase in the kidney are 1,25-dihydroxyvitamin D(3) itself, parathyroid hormone and FGF23. The extent and importance of extra-renal, 1,25-dihydroxyvitamin D(3) synthesis is then considered. Finally the features of the 24R-hydroxylase, which produces 24R,25-dihydroxyvitamin D(3) in the kidney and is induced by and inactivated, 1,25-dihydroxyvitamin D(3)in target cells are described.

Nutrigenomics, vitamin D and cancer prevention

Although there is growing epidemiological, preclinical and clinical evidence suggesting that low vitamin D intake, exposure and/or status is associated with an increased risk of various types of cancer, the optimum amount needed remains controversial. Furthermore, there is evidence that a U- or J-shaped response curve exist between 25(OH)D and certain cancers. Increasing information about the impact of genetic variation, especially polymorphisms that influence absorption, transport, metabolism and associated molecular targets, should help clarify inconsistencies in the data regarding vitamin D's effect on cancer risk. Rather than focusing on the main effects of a few variants of these genes alone, future studies need to consider gene-nutrient or environmental interactions. Nutrigenomics should clarify who might benefit and be placed at risk because of vitamin D exposure.

Alterations in Vitamin D signalling and metabolic pathways in breast cancer progression: a study of VDR, CYP27B1 and CYP24A1 expression in benign and malignant breast lesions

Background

Breast cancer is a heterogeneous disease associated with different patient prognosis and responses to therapy. Vitamin D has been emerging as a potential treatment for cancer, as it has been demonstrated that it modulates proliferation, apoptosis, invasion and metastasis, among others. It acts mostly through the Vitamin D receptor (VDR) and the synthesis and degradation of this hormone are regulated by the enzymes CYP27B1 and CYP24A1, respectively. We aimed to study the expression of these three proteins by immunohistochemistry in a series of breast lesions.

Methods

We have used a cohort comprising normal breast, benign mammary lesions, carcinomas in situ and invasive carcinomas and assessed the expression of the VDR, CYP27B1 and CYP24A1 by immunohistochemistry.

Results

The results that we have obtained show that all proteins are expressed in the various breast tissues, although at different amounts. The VDR was frequently expressed in benign lesions (93.5%) and its levels of expression were diminished in invasive tumours (56.2%). Additionally, the VDR was strongly associated with the oestrogen receptor positivity in breast carcinomas. CYP27B1 expression is slightly lower in invasive carcinomas (44.6%) than in benign lesions (55.8%). In contrast, CYP24A1 expression was augmented in carcinomas (56.0% in in situ and 53.7% in invasive carcinomas) when compared with that in benign lesions (19.0%).

Conclusions

From this study, we conclude that there is a deregulation of the Vitamin D signalling and metabolic pathways in breast cancer, favouring tumour progression. Thus, during mammary malignant transformation, tumour cells lose their ability to synthesize the active form of Vitamin D and respond to VDR-mediated Vitamin D effects, while increasing their ability to degrade this hormone.

Blood 25-hydroxyvitamin D3 concentrations and incident sporadic colorectal adenoma risk: a pooled case-control study

The authors examined the association between circulating 25-hydroxyvitamin D(3) (25(OH)D(3)), the best indicator of total vitamin D exposure, and incident, sporadic colorectal adenoma risk in a pooled analysis of primary data from 3 colonoscopy-based case-control studies conducted in Minnesota, North Carolina, and South Carolina between 1991 and 2002. The pooled study included 616 colorectal adenoma cases and 770 polyp-free controls. Multivariable logistic regression was used to estimate the association between circulating 25(OH)D(3) and colorectal adenoma risk. Stratified analyses and the likelihood ratio test were used to examine effect modification by various risk factors. In the pooled analysis, higher circulating 25(OH)D(3) concentrations were statistically significantly associated with decreased colorectal adenoma risk (highest vs. lowest quartile odds ratio = 0.59, 95% confidence interval: 0.41, 0.84). The observed inverse association was stronger among participants who used nonsteroidal antiinflammatory drugs regularly (highest vs. lowest quartile odds ratio = 0.33, 95% confidence interval: 0.19, 0.56). Inverse associations between 25(OH)D(3) and colorectal adenoma did not differ substantially by other risk factors or by adenoma characteristics. These findings support the hypothesis that greater vitamin D exposure may reduce the risk of colorectal adenoma and suggest that it may do so more strongly in combination with antiinflammatory agents.

Vitamin D analogues targeting CYP24 in chronic kidney disease

The cytochrome P450 enzyme 24-hydroxylase (CYP24) plays a critical role in regulating levels of vitamin D hormone. Aberrant expression of CYP24 has been implicated in vitamin D insufficiency and resistance to vitamin D therapy. We have demonstrated amplified CYP24 expression in uremic rats, suggesting that CYP24 has an etiological role in vitamin D insufficiency commonly associated with chronic kidney disease (CKD). We have designed two new analogues of 1alpha,25-dihydroxyvitamin D3 (1alpha,25(OH)2D3), namely CTA091 and CTA018/MT2832, which are potent inhibitors of CYP24. In vitro studies with CTA091 show that it enhances the potency of 1alpha,25(OH)2D3. In vivo studies demonstrate that CTA091 decreases serum intact parathyroid hormone (iPTH) levels and increases circulating 1alpha,25(OH)2D3. CTA091 increases both Cmax and AUC of co-administered 1alpha,25(OH)2D3. These studies indicate that CYP24 inhibition can increase cellular responsiveness to vitamin D hormone and potentiate vitamin D therapy. CTA018/MT2832 differs from CTA091 in that it also has the ability to activate vitamin D receptor-mediated transcription. CTA018/MT2832 effectively suppresses elevated iPTH secretion at doses which do not affect serum calcium or phosphorus levels in a rodent model of CKD. Studies with both new analogues underscore the potential utility of CYP24 inhibition in the treatment of secondary hyperparathyroidism in CKD.

Actions of vitamin D are mediated by the TLR4 pathway in inflammation-induced colon cancer

Many chronic inflammatory diseases are associated with increased risk of developing cancer. In the colon, strong support for a link between chronic inflammation and cancer extends, in part, from population-based studies of persons with inflammatory bowel disease (IBD). Patients with IBD are at increased risk of developing colorectal cancer (CRC). The general consensus is that IBD results from the combined effects of genetics and environment factors known to affect the immune system. Vitamin D, an important regulator of the immune system, has been linked to IBD. Despite the strong potential reported for 1,25-dihydroxyvitamin D (1,25-OH)2D), its effects on calcium metabolism limits its application. Recently, less active vitamin D metabolites, cholecalciferol and 25-hydroxyvitamin D (25(OH)D), have gained considerable attention as promising agents against IBD-related colon cancer. Yet, their anti-proliferative properties and mechanism of action remain to be better defined. We present several signaling pathways commonly regulated by vitamin D compounds and highlight their regulation on TLR4. The efficacy of 25(OH)D and 1alpha-hydroxyviatmin D5 are evaluated using the azoxymethane (AOM)/dextran sodium sulfate (DSS)-induced IBD-related colon carcinogenesis model. In summary, vitamin D supplementation may provide a cost-effective approach to reduce IBD related colon cancer.

The candidate oncogene CYP24A1: A potential biomarker for colorectal tumorigenesis

The main autocrine/paracrine role of the active metabolite of vitamin D(3), 1alpha,25-dihydroxyvitamin D(3) (1,25-D(3)), is inhibition of cell growth and induction of cell differentiation and/or apoptosis. Synthesis and degradation of the secosteroid occurs not only in the kidney but also in normal tissue or malignant extrarenal tissues such as the colon. Because 25-hydroxyvitamin D(3) 24-hydroxylase (CYP24A1) is considered to be the main enzyme determining the biological half-life of 1,25-D(3), we have examined expression of the CYP24A1 mRNA (by real-time RT-PCR) and protein (by immunohistochemistry) in normal human colon mucosa, colorectal adenomas, and adenocarcinomas in 111 patients. Although 76% of the normal and benign colonic tissue was either completely devoid of or expressed very low levels of CYP24A1, in the majority of the adenocarcinomas (69%), the enzyme was present at high concentrations. A parallel increased expression of the proliferation marker Ki-67 in the same samples suggests that overexpression of CYP24A1 reduced local 1,25-D(3) availability, decreasing its antiproliferative effect.

Molecular actions of vitamin D contributing to cancer prevention

The population-based relationship between low vitamin D status and increased cancer risk is now generally accepted. While these relationships are between serum 25 hydroxyvitamin D and cancer, cell-based studies show that the metabolite 1,25 dihydroxyvitamin D is biologically active and influences cell biology relevant to cancer through vitamin D receptor-mediated gene transcription. This review examines this paradox and also discusses the cell and gene targets influenced by 1,25 dihydroxyvitamin D that may account for the anti-cancer actions of vitamin D. A review of the literature shows that while vitamin D-induced growth arrest and apoptosis of tumor cells or their non-neoplastic progenitors are plausible mechanisms, other gene targets related to DNA repair and immunomodulation, and other cell targets such as the stromal cells and cells of the immune system, may be regulated by 1,25 dihydroxyvitamin D and contribute to vitamin D mediated cancer prevention.

A novel SNP in a vitamin D response element of the CYP24A1 promoter reduces protein binding, transactivation, and gene expression

The active form of vitamin D (1alpha,25(OH)(2)D(3)) is known to have antiproliferative effects and has been implicated in cancers of the colon, breast, and prostate. These cancers occur more frequently among African Americans than Caucasians, and individuals with African ancestry are known to have approximately twofold lower levels of serum vitamin D (25(OH)D) compared with individuals of European ancestry. However, epidemiological studies of the vitamin D receptor (VDR) have shown inconsistent associations with cancer risk, suggesting that differences in other genes in the pathway may be important. We sought to identify functionally significant polymorphic variants in CYP24A1, a gene that is highly inducible by 1alpha,25(OH)(2)D(3) and that encodes the primary catabolic enzyme in the pathway. Here we report the identification of six novel SNPs in the human CYP24A1 promoter, including one at nucleotide -279 occurring within the distal vitamin D response element (VDRE2). Our experiments demonstrate that the VDRE2 variant results in decreased protein binding and transactivation in vitro, and reduced expression of CYP24A1 in cultured primary human lymphocytes provides evidence for an effect in vivo. This variant was only observed in our African American population, and represents a first step toward understanding differences in disease risk among racial/ethnic groups.