Constitutively active RAS signaling reduces 1,25 dihydroxyvitamin D-mediated gene transcription in intestinal epithelial cells by reducing vitamin D receptor expression

Multiomics profiling reveals VDR as a central regulator of mesenchymal stem cell senescence with a known association with osteoporosis after high-fat diet exposure

The consumption of a high-fat diet (HFD) has been linked to osteoporosis and an increased risk of fragility fractures. However, the specific mechanisms of HFD-induced osteoporosis are not fully understood. Our study shows that exposure to an HFD induces premature senescence in bone marrow mesenchymal stem cells (BMSCs), diminishing their proliferation and osteogenic capability, and thereby contributes to osteoporosis. Transcriptomic and chromatin accessibility analyses revealed the decreased chromatin accessibility of vitamin D receptor (VDR)-binding sequences and decreased VDR signaling in BMSCs from HFD-fed mice, suggesting that VDR is a key regulator of BMSC senescence. Notably, the administration of a VDR activator to HFD-fed mice rescued BMSC senescence and significantly improved osteogenesis, bone mass, and other bone parameters. Mechanistically, VDR activation reduced BMSC senescence by decreasing intracellular reactive oxygen species (ROS) levels and preserving mitochondrial function. Our findings not only elucidate the mechanisms by which an HFD induces BMSC senescence and associated osteoporosis but also offer new insights into treating HFD-induced osteoporosis by targeting the VDR-superoxide dismutase 2 (SOD2)-ROS axis.

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.

Molecular Mechanism of Vitamin D Receptor Modulating Wnt/β-catenin Signaling Pathway in Gastric Cancer

Background: Gastric cancer is the most common gastrointestinal cancer worldwide. The latest data showed that it was the fourth leading cause of cancer-related death. The unobvious symptom and the difficulties lying in the early diagnosis largely affect the effect of the treatment. Therefore, it becomes particularly important to investigate the related genes and signal transduction pathways in gastric cancer. Our previous study found that the vitamin D receptor (VDR) gene FokI polymorphism may be associated with susceptibility to gastric cancer in the Chinese Han population. However, the mechanism of VDR affecting gastric cancer is unknown. In this study, we explored the molecular mechanism and the possible signaling pathway of VDR modulating carcinogenesis and progression of gastric cancer. Methods: The expression of VDR in gastric cancer cell lines was interfered by plasmid transfection and RNA interference technology. And then we analyzed the cell viability and invasive ability by MTT assay, colony formation assay, and transwell migration assay, and detected the expression of VDR and several signaling proteins in gastric cancer cells by SDS-PAGE and Western blotting. Results: The overexpression of VDR can significantly inhibit the viability and invasive ability of gastric cancer cells; on the contrary, when VDR siRNA inhibits the expression of VDR, the viability and invasive ability of gastric cancer cells enhanced. VDR expression levels in gastric cancer cells treated with 1,25 (OH) 2D3 showed a time-dependent increased expression; and with the increase of the VDR expression, the expression of β-catenin decreased gradually, but the expression of E-cadherin showed a time-dependent increase (P < 0.05). Compared with the mutant-type VDR gene(ff) cells, the degree of β-catenin decline was significantly enhanced after transfected with homozygous wild-type VDR gene (FF) plasmids (p<0.05). Conclusions: The results of this study indicate that VDR FokI polymorphism plays an important role in the malignant phenotype of gastric cancer cells, such as proliferation, invasion, and clone formation. When the VDR is activated by its ligand, it can prevent the nuclear import of β-catenin, affect the E-cadherin level, inhibit the proliferation of gastric cancer cells, which suggested that VDR FokI gene may play a role of cancer suppressor via Wnt/β-catenin signaling pathway.

Vitamin D-Related Genes and Thyroid Cancer-A Systematic Review

Vitamin D, formerly known for its role in calcium-phosphorus homeostasis, was shown to exert a broad influence on immunity and on differentiation and proliferation processes in the last few years. In the field of endocrinology, there is proof of the potential role of vitamin D and vitamin D-related genes in the pathogenesis of thyroid cancer-the most prevalent endocrine malignancy. Therefore, the study aimed to systematically review the publications on the association between vitamin D-related gene variants (polymorphisms, mutations, etc.) and thyroid cancer. PubMed, EMBASE, Scopus, and Web of Science electronic databases were searched for relevant studies. A total of ten studies were found that met the inclusion criteria. Six vitamin D-related genes were analyzed (VDR-vitamin D receptor, CYP2R1-cytochrome P450 family 2 subfamily R member 1, CYP24A1-cytochrome P450 family 24 subfamily A member 1, CYP27B1-cytochrome P450 family 27 subfamily B member 1, DHCR7-7-dehydrocholesterol reductase and CUBN-cubilin). Moreover, a meta-analysis was conducted to summarize the data from the studies on VDR polymorphisms (rs2228570/FokI, rs1544410/BsmI, rs7975232/ApaI and rs731236/TaqI). Some associations between thyroid cancer risk (VDR, CYP24A1, DHCR7) or the clinical course of the disease (VDR) and vitamin D-related gene polymorphisms were described in the literature. However, these results seem inconclusive and need validation. A meta-analysis of the five studies of common VDR polymorphisms did not confirm their association with increased susceptibility to differentiated thyroid cancer. Further efforts are necessary to improve our understanding of thyroid cancer pathogenesis and implement targeted therapies for refractory cases.

Cholecalciferol induces apoptosis via autocrine metabolism in epidermoid cervical cancer cells

The anti-cancer effects of vitamin D are of fundamental interest. Cholecalciferol is sequentially hydroxylated endogenously to calcidiol and calcitriol. Here, SiHa epidermoid cervical cancer cells were treated with cholecalciferol (10 - 2600 nM). Cell count and viability were assayed using crystal violet and trypan blue, respectively. Apoptosis was assessed using flow cytometry for early and late biomarkers along with brightfield microscopy and transmission electron microscopy. Autocrine vitamin D metabolism was analysed by qPCR and immunoblotting for activating enzymes; 25-hydroxylases (CYP2R1 and CYP27A1) and 1α-hydroxylase (CYP27B1); the catabolic 24-hydroxylase (CYP24A1); and the vitamin D receptor (VDR). Data were analysed using one-way ANOVA and Bonferroni post hoc test, and p<0.05 was considered significant. After cholecalciferol, cell count (p=0.011) and viability (p<0.0001) decreased, apoptotic biomarkers were positive, mitochondrial membrane potential decreased (p=0.0145), and phosphatidylserine externalisation (p=0.0439); terminal caspase activity (p=0.0025) and nuclear damage (p=0.004) increased. Microscopy showed classical features of apoptosis. Gene and protein expression were concordant. Immunoblots revealed increased CYP2R1 (p = 0.021), VDR (p=0.04) and CYP24A1 (p=0.0274) and decreased CYP27B1 (p=0.031). We conclude that autocrine activation of cholecalciferol to calcidiol may mediate VDR signalling of growth inhibition and apoptosis in SiHa cells.

Vitamin D Receptor Expression and its Clinical Significance in Papillary Thyroid Cancer

Objective: This study aimed to evaluate the association between vitamin D receptor (an essential component in the vitamin D signaling pathway) and serum vitamin D as well as its clinical significance in papillary thyroid cancer. Methods: This prospective cohort study comprised patients with thyroid tumors who visited our hospital, from 2017 to 2018. The level of vitamin D receptor expression from thyroid tissue was measured in patients with thyroid tumor and evaluated for correlation with serum vitamin D levels and clinicopathologic characteristics of papillary thyroid cancer. Data from 501 patients with papillary thyroid cancer from The Cancer Genome Atlas database were analyzed. Results: Increased vitamin D receptor protein and mRNA expression were observed in papillary thyroid cancer compared to those in normal and benign tissues. Lower vitamin D receptor protein expression was associated with high TNM stage papillary thyroid cancer and low p21 protein expression. Lower relative vitamin D receptor mRNA expression in papillary thyroid cancer was associated with low serum 25-hydroxyvitamin D level. The Cancer Genome Atlas database showed a positive correlation among mRNA expression of vitamin D receptor, CYP24A1, and p21. Conclusions: An association between decreased vitamin D receptor protein expression and advanced stage papillary thyroid cancer, and a correlation between low vitamin D receptor mRNA expression with low serum 25-hydroxyvitamin D level was observed. Low vitamin D receptor expression in papillary thyroid cancer was shown to positively correlate with low serum vitamin D level and disease aggressiveness.

Synthesis and characterization of vitamin D3-functionalized carbon dots for CRISPR/Cas9 delivery

Aim: To develop a novel nanovector for the delivery of genetic fragments and CRISPR/Cas9 systems in particular. Materials & methods: Vitamin D₃-functionalized carbon dots (D/CDs) fabricated using one-step microwave-aided methods were characterized by different microscopic and spectroscopic techniques. The 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl tetrazolium bromide assay and flow cytometry were employed to determine the cell viability and transfection efficiency. Results: D/CDs transfected CRISPR plasmid in various cell lines with high efficiency while maintaining their remarkable efficacy at high serum concentration and low plasmid doses. They also showed great potential for the green fluorescent protein disruption by delivering two different types of CRISPR/Cas9 systems. Conclusion: Given their high efficiency and safety, D/CDs provide a versatile gene-delivery vector for clinical applications.

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.

Vitamin D: Promises on the Horizon and Challenges Ahead for Fighting Pancreatic Cancer

Simple Summary

Pancreatic cancer is an almost universally lethal cancer, largely due to its late diagnosis, early metastasis, and therapeutic resistance. This highlights the need to develop novel and effective intervention strategies to improve the outcomes of patients with pancreatic cancer. Vitamin D is one of the hottest topics in cancer research and clinics because of its pleiotropic functions on the hallmarks of cancer. Here we critically review past and current efforts that define the effects of vitamin D on the risk, incidence, patient survival, and mortality of pancreatic cancer. We also provide overviews on the opportunities and challenges associated with vitamin D as an economic adjunct to improve the efficacy of immunotherapy and chemo- or radiotherapy for pancreatic cancer.

Abstract

Pancreatic cancer has a dismal prognosis, while its incidence is increasing. This is attributed, in part, to a profound desmoplastic and immunosuppressive tumor microenvironment associated with this cancer and resistance to current available therapies. Novel and effective intervention strategies are urgently needed to improve the outcomes of patients with pancreatic cancer. Vitamin D has pleiotropic functions beyond calcium–phosphate homeostasis and has been extensively studied both in the laboratory and clinic as a potential preventive agent or adjunct to standard therapies. Accumulating evidence from ecological, observational, and randomized controlled trials suggests that vitamin D has beneficial effects on risk, survival, and mortality in pancreatic cancer, although controversies still exist. Recent advances in demonstrating the important functions of vitamin D/vitamin D receptor (VDR) signaling in the regulation of stromal reprogramming, the microbiome, and immune response and the emergence of checkpoint immunotherapy provide opportunities for using vitamin D or its analogues as an adjunct for pancreatic cancer intervention. Many challenges lie ahead before the benefits of vitamin D can be fully realized in pancreatic cancer. These challenges include the need for randomized controlled trials of vitamin D to assess its impact on the risk and survival of pancreatic cancer, optimizing the timing and dosage of vitamin D or its analogues as an adjunct for pancreatic cancer intervention and elucidating the specific role of vitamin D/VDR signaling in the different stages of pancreatic cancer. Nevertheless, vitamin D holds great promise for reducing risk and improving outcomes of this disease.

Vitamin D Status and Survival in Stage II-III Colorectal Cancer

Vitamin D status has been shown to be positively correlated with the morbidity and prognosis of colorectal cancer (CRC) patients. However, the prognostic effect of vitamin D status on patients with stage II and III CRC, especially Asian patients, remains unclear. A total of 728 patients (523 in the primary cohort and 205 in the validation cohort) who were diagnosed with stage II-III CRC between January 2011 and December 2015 were enrolled. Their serum 25-hydroxyvitamin D3 [25(OH)D] levels were tested. Kaplan-Meier curves and Cox regression analyses were carried out. Subgroup analyses were conducted according to tumor location. In the primary cohort, the serum 25(OH)D level was positively correlated with the overall survival (OS) of all CRC patients (p= 0.016) and stage III patients (p= 0.009), while no correlation was found between 25(OH)D level and the prognosis of patients with stage II CRC. Moreover, 25(OH)D level was an independent prognostic factor for the OS of all patients with CRC [HR 0.541, 95% CI 0.334-0.875, p=0.012] and those with stage III CRC (HR 0.563, 95% CI 0.319-0.993, p=0.047). Subgroup analysis indicated that only in the left-sided subgroup, stage III CRC patients with high 25(OH)D levels had better OS than those with low 25(OH)D levels (HR 0.474, 95% CI 0.230-0.978, p=0.043). In the validation cohort, serum 25(OH)D levels were verified to have prognostic value for patients with stage III CRC (HR 0.220, 95% CI 0.080-0.602, p=0.003), and low 25(OH)D levels indicated worse OS for left-sided stage III CRC patients (HR 0.233, 95% CI 0.075-0.727, p=.012). In conclusion, vitamin D status is positively correlated with the survival of CRC patients, especially those with left-sided stage III CRC.

Mucosal vitamin D signaling in inflammatory bowel disease

Epidemiological studies have identified vitamin D (25(OH)D) deficiency to be highly prevalent among patients with inflammatory bowel disease (IBD), and low serum levels correlate with a higher disease activity and a more complicated disease course. The link to IBD pathogenesis has been subject of investigations, primarily due to the distinct immunological functions of vitamin D signaling, including anti-inflammatory and anti-fibrotic actions. Vitamin D is a pleiotropic hormone that executes its actions on cells through the vitamin D receptor (VDR). A leaky gut, i.e. an insufficient intestinal epithelial barrier, is thought to be central for the pathogenesis of IBD, and emerging data support the concept that vitamin D/VDR signaling in intestinal epithelial cells (IECs) has an important role in controlling barrier integrity. Here we review the latest evidence on how vitamin D promotes the interplay between IECs, the gut microbiome, and immune cells and thereby regulate the intestinal immune response. On the cellular level, vitamin D signaling regulates tight junctional complexes, apoptosis, and autophagy, leading to increased epithelial barrier integrity, and promotes expression of antimicrobial peptides as part of its immunomodulating functions. Further, intestinal VDR expression is inversely correlated with the severity of inflammation in patients with IBD, which might compromise the positive effects of vitamin D signaling in patients with flaring disease. Efforts to reveal the role of vitamin D in the pathophysiology of IBD will pave the road for the invention of more rational treatment strategies of this debilitating disease in the future.

Inhibition of HAS2 and hyaluronic acid production by 1,25-Dihydroxyvitamin D3 in breast cancer

1,25-Dihydroxyvitamin D₃ (1,25D3) induces growth arrest and apoptosis in breast cancer cells in vivo and in vitro, however the exact mechanisms are unclear. Although the vitamin D receptor (VDR), a ligand dependent transcription factor, is required for growth regulation by vitamin D, the specific target genes that trigger these effects are unknown. Genomic profiling of murine mammary tumor cells with differential VDR expression identified 35 transcripts that were altered by the 1,25D3-VDR complex including Hyaluronan Synthase-2 (Has2). Here we confirmed that 1,25D3 reduces both HAS2 gene expression and hyaluronic acid (HA) synthesis in multiple models of breast cancer. Furthermore, we show that the growth inhibitory effects of 1,25D3 are partially reversed in the presence of high molecular weight HA. HAS2 expression and HA production are elevated in immortalized human mammary epithelial cells induced to undergo epithelial-mesenchymal transition (EMT) through stable expression of TGFβ, SNAIL or TWIST and in those expressing oncogenic H-RAS^V12, indicating that deregulation of HA production may be an early and frequent event in breast tumorigenesis. 1,25D3 also reduces HA secretion and acts additively with an HA synthesis inhibitor to slow growth of cells expressing TGFβ, SNAIL and TWIST. Analysis of mammary gland and tumors from Vdr knockout mice suggest that loss of VDR is associated with enhanced HAS2 expression and HA production in vivo. These data define a novel role for 1,25D3 and the VDR in control of HA synthesis in epithelial tissues that likely contributes to its anti-cancer actions.

Effects of 1,25-dihydroxyvitamin D3 on experimental periodontitis and AhR/NF-κB/NLRP3 inflammasome pathway in a mouse model

Vitamin D has been known to have important regulatory functions in inflammation and immune response and shows inhibitory effects on experimental periodontitis in animal models. However, the potential mechanism has yet to be clarified. Recent studies have highlighted Aryl hydrocarbon receptor (AhR) and its downstream signaling as a crucial regulator of immune homeostasis and inflammatory regulation.

OBJECTIVE

This study aimed to clarify the effect of 1,25-dihydroxyvitamin D3 (VD3) on experimental periodontitis and AhR/nuclear factor-κB (NF-κB)/NLR pyrin domain-containing 3 (NLRP3) inflammasome pathway in the gingival epithelium in a murine model.

METHODOLOGY

We induced periodontitis in male C57BL/6 wild-type mice by oral inoculation of Porphyromonas gingivalis (P. gingivalis), and subsequently gave intraperitoneal VD3 injection to the mice every other day for 8 weeks. Afterwards, we examined the alveolar bone using scanning electron microscopy (SEM) and detected the gingival epithelial protein using western blot analysis and immunohistochemical staining.

RESULTS

SEM images demonstrated that alveolar bone loss was reduced in the periodontitis mouse model after VD3 supplementation. Western blot analyses and immunohistochemical staining of the gingival epithelium showed that the expression of vitamin D receptor, AhR and its downstream cytochrome P450 1A1 were enhanced upon VD3 application. Additionally, VD3 decreased NF-κB p65 phosphorylation, and NLRP3, apoptosis-associated speck-like protein, caspase-1, interleukin-1β (IL-1β) and IL-6 protein expression.

CONCLUSIONS

These results implicate the alleviation of periodontitis and the alteration of AhR/NF-κB/NLRP3 inflammasome pathway by VD3 in the mouse model. The attenuation of this periodontal disease may correlate with the regulation of AhR/NF-κB/NLRP3 inflammasome pathway by VD3.

1,25-Dihydroxyvitamin D3 affects gastric cancer progression by repressing BMP3 promoter methylation

Background

Vitamin D₃ has been known to have an anticancer effect, but the mechanisms underlying this is poorly explored. The present study aimed to investigate the antitumor role of vitamin D₃ on gastric cancer and mechanisms.

Methods

The Roche Elecsys platform was applied in retrospective studies to detect the role of 25-hydroxylvitamin D₃ in adenocarcinoma and colony formation assay was conducted to verify the effect of 1, 25-dihydroxyvitamin D₃ on the proliferation of gastric cancer cells. After the identification of hypermethylation of BMP3 CpG islands by bisulfite genomic sequencing (BGS), we further investigated the relationship of BMP3 expression and gastric carcinogenesis by Western blot analysis and gel electrophoresis mobility shift assay (EMSA).

Results

Here we show that low concentration of 1, 25-dihydroxyvitamin D₃ links to can-cerization and significantly inhibits proliferation of undifferentiated gastric cancer cell lines SGC-7901 and BGC-823. BMP3 promoter hypermethylation was highly correlated with gastric tumor. Moreover, BMP3 expression was regulated by its promoter methylation in gastric cells. The further exploration of the relationship between 1, 25-dihydroxyvitamin D₃ and BMP3 by EMSA results that 1, 25-dihydroxyvitamin D₃ stimulates BMP3 expression by the inhibition of BMP3 promoter methylation in gastric tumor cells.

Conclusion

In combination with the data from clinical research, bioinformatics analysis and experimental verification, we propose that 1, 25-hydroxylvitamin D₃ affects gastric cancer progression by repressing BMP3 promoter methylation.

Chlorpyrifos stimulates expression of vitamin D3 receptor in skin cells irradiated with UVB

Skin, the organ responsible for vitamin D synthesis, is fully exposed to many xenobiotics, e.g. polycyclic aromatic hydrocarbons and pesticides. A broad spectrum organophosphorus insecticides (OP's), such as chlorpyrifos (CPS), are commonly used in agriculture and to control domestic insects. Thus, the aim of this study was to investigate the effect of chlorpyrifos, on the expression of vitamin D₃ receptor (VDR) in human keratinocytes cell line HaCaT and fibroblasts cell line BJ. The impact of CPS and UVB radiation on cell viability were examined by Neutral Red assay. The effect of CPS on VDR expression was evaluated by RT-qPCR and flow cytometry (FC). The presented study demonstrated that exposure to CPS and UVB significantly affects the viability of HaCaT and BJ cells lines. Results also revealed that exposure to CPS induced the expression at mRNA and protein level of VDR nuclear receptor in both cell lines exposed to UVB. In HaCaT incubated with 250 μM CPS and 15 mJ/cm² UVB, the relative VDR expression was ∼2-fold higher; whereas in BJ incubated with 250 μM CPS and 20 mJ/cm², UVB was∼3-fold higher. Results from FC confirmed this result, as VDR expression increased by ~250% in HaCaT incubated with 250 μM CPS and 20 mJ/cm² UVB, and in BJ incubated with 250 μM CPS, and 20 mJ/cm² UVB cells VDR expression increased by ~190%, compared with control. It can therefore be concluded that OPs pesticide might interfere with vitamin D₃ metabolism in skin cells.

Ancient Nuclear Receptor VDR With New Functions: Microbiome and Inflammation

The biological functions of 1α,25-dihydroxyvitamin D3 are regulated by nuclear receptor vitamin D receptor (VDR). The expression level of VDR is high in intestine. VDR is an essential regulator of intestinal cell proliferation, barrier function, and immunity. Vitamin D/VDR plays a protective role in inflammatory bowel diseases (IBDs), both ulcerative colitis and Crohn's disease. Emerging evidence demonstrates low VDR expression and dysfunction of vitamin D/VDR signaling in patients with IBD. Here, we summarize the progress made in vitamin D/VDR signaling in genetic regulation, immunity, and the microbiome in IBD. We cover the mechanisms of intestinal VDR in regulating inflammation through inhibiting the NF-ĸB pathway and activating autophagy. Recent studies suggest that the association of VDR single nucleotide polymorphisms with immune and intestinal pathology may be sex dependent. We emphasize the tissue specificity of VDR and its sex- and time-dependent effects. Furthermore, we discuss potential clinical application and future direction of vitamin D/VDR in preventing and treating IBD.

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.