Vitamin D receptor gene polymorphisms and the risk of colorectal cancer in a Chinese population

From molecular basis to clinical insights: a challenging future for the vitamin D endocrine system in colorectal cancer

Colorectal cancer (CRC) is one of the most life-threatening neoplasias in terms of incidence and mortality worldwide. Vitamin D deficiency has been associated with an increased risk of CRC. 1α,25-Dihydroxyvitamin D3 [1,25(OH)2D3], the most active vitamin D metabolite, is a pleiotropic hormone that, through its binding to a transcription factor of the nuclear receptor superfamily, is a major regulator of the human genome. 1,25(OH)2D3 acts on colon carcinoma and stromal cells and displays tumor protective actions. Here, we review the variety of molecular mechanisms underlying the effects of 1,25(OH)2D3 in CRC, which affect multiple processes that are dysregulated during tumor initiation and progression. Additionally, we discuss the epidemiological data that associate vitamin D deficiency and CRC, and the most relevant randomized controlled trials of vitamin D3 supplementation conducted in both healthy individuals and CRC patients.

Colorectal Cancer Risk Prediction Using the rs4939827 Polymorphism of the SMAD7 Gene in the Romanian Population

Colorectal cancer (CRC) is globally recognized as a prevalent malignancy known for its significant mortality rate. Recent years have witnessed a rising incidence trend in colorectal cancer, emphasizing the necessity for early diagnosis. Our study focused on examining the impact of the SMAD7 gene variant rs4939827 on the risk of colorectal cancer occurrence. The composition of our study group included 340 individuals, comprising 170 CRC diagnosed patients and 170 healthy controls. We performed genotyping of all biological samples using the TaqMan assay on the ABI 7500 Real-Time PCR System (Applied Biosystems, Waltham, MA, USA). This investigation focused on the rs4939827 gene variant, assessing its association with CRC risk and clinicopathological characteristics. Genotyping results for the SMAD7 gene variant rs4939827 revealed a 42.6% prevalence of the C allele in CRC patients (p = 0.245) and a 22.8% prevalence of the T allele in control subjects (p = 0.109). This study concluded that there was an elevated risk of CRC in the dominant model for CC/CT+TT, with a p-value of 0.113 and an odds ratio (OR) of 2.781, within a 95% confidence interval (CI) of 0.998 to 3.456. The findings of our research indicate a correlation between variants of the SMAD7 gene and the likelihood of developing colorectal cancer in our study population. Consequently, these results could be instrumental in facilitating early diagnosis of colorectal cancer utilizing information on single-nucleotide polymorphism (SNP) and genetic susceptibility to the disease.

Evaluation of rs10811661 polymorphism in CDKN2A / B in colon and gastric cancer

One of the causes of colon and gastric cancer is the dysregulation of carcinogenic genes, tumor inhibitors, and micro-RNA. The purpose of this study is to apply rs10811661 polymorphism in CDKN2A /B gene as an effective biomarker of colon cancer and early detection of gastric cancer. As a result,400 blood samples, inclusive of 200 samples from healthy individuals and 200 samples (100 samples from intestinal cancer,100 samples from stomach cancer) from the blood of someone with these cancers, to determine the genotype of genes in healthful and ill people through PCR-RFLP approach and Allelic and genotypic tests of SPSS software. To observe the connection between gastric cancer and bowel cancer risk and genotypes, the t-student test for quantitative variables and Pearson distribution for qualitative variables have been tested and the results have been evaluated using the Chi-square test. The effects confirmed that the highest frequency of TT genotypes is in affected individuals and CC genotype is in healthful individuals. In addition, it confirmed that women were more inclined than men to T3 tumor invasion and most grade II and III colon cancers, and in older sufferers with gastric cancer, the grade of tumor tended to be grade I. Among genetic variety and rs10811661, with invasiveness, there is a tumor size and degree in the affected person. In summary, our findings suggest that the rs10811661 polymorphism of the CDKN2A / B gene is strongly associated with the occurrence of intestinal cancer and stomach is linked to its potential role as a prognostic biomarker for the management of bowel cancer and stomach.

Association of vitamin D receptor polymorphisms with colorectal cancer susceptibility: A systematic meta-analysis

BACKGROUND

Recent studies have reported an association between vitamin D receptor (VDR) polymorphisms and colorectal cancer (CRC) risk; however, the results are controversial. This meta-analysis was performed to investigate whether the Cdx-2, Tru9I, FokI, BsmI, TaqI, and ApaI polymorphisms were correlated with CRC susceptibility.

METHODS

All potential studies were retrieved by searching the PubMed, EMBASE, and Cochrane Library databases through October 2, 2021. Odds ratios (ORs) with 95% confidence intervals were used to evaluate the correlation between VDR gene Cdx-2, Tru9I, FokI, BsmI, TaqI, and ApaI polymorphisms and CRC risk.

RESULTS

In this meta-analysis, the BsmI variant was significantly correlated with a lower risk of CRC, especially in Caucasian population (B vs b: OR 0.94, 95%CI 0.90-0.99; BB vs bb: OR 0.88; 95%CI 0.79-0.97; BB vs Bb/bb: BB vs Bb/bb: OR 0.89; 95%CI 0.81-0.98). A statistically significant result from the FokI polymorphism was observed in colon cancer rather than rectal cancer (Ff vs FF: OR 0.86, 95%CI 0.84-0.93; ff/Ff vs FF: OR 0.88, 95%CI 0.79-0.98; ff vs Ff/FF: OR 0.90, 95%CI 0.82-0.99). Similarly, Cdx-2 polymorphism was found to be associated with decreased CRC risk among Africans (C vs c: OR 0.50, 95%CI 0.33-0.75; CC vs cc: OR 0.09, 95%CI 0.01-0.77; Cc vs cc: OR 0.49, 95%CI 0.30-0.81; CC/Cc vs cc: OR 0.45, 95%CI 0.28-0.74,).

CONCLUSION

Our findings indicate that VDR polymorphisms are significantly associated with CRC risk.

Investigation of Microbial Translocation, TLR and VDR Gene Polymorphisms, and Recurrence Risk in Stage III Colorectal Cancer Patients

Gut microbial dysbiosis and microbial passage into the peripheral blood leads to colorectal cancer (CRC) and disease progression. Toll-like (TLR) and vitamin D (VDR) receptors play important role in the immune modulation and polymorphisms that may increase CRC risk and death rates. The aim of the current study was to demonstrate the prognostic value of microbial DNA fragments in the blood of stage III CRC patients and correlate such microbial detection to TLR/VDR polymorphisms. Peripheral blood was collected from 132 patients for the detection of microbial DNA fragments, and TLR/VDR gene polymorphisms. In the detection of various microbial DNA fragments, TLR and VDR polymorphisms was significantly higher compared to healthy group. Homozygous individuals of either TLR or VDR polymorphisms had significantly higher detection rates of microbial DNA fragments. Mutational and MSI status were significantly correlated with TLR9 and VDR polymorphisms. Significantly shorter disease-free survival was associated with patients with BRAF mutated tumors and ApaI polymorphisms, whereas shorter overall survival was associated with the detection of C. albicans. The detection of B. fragilis, as demonstrated by the multivariate analysis, is an independent poor prognostic factor for shorter disease-free survival. TLR/VDR genetic variants were significantly correlated with the detection of microbial fragments in the blood, and this in turn is significantly associated with tumorigenesis and disease progression.

Association of SMAD7 genetic markers and haplotypes with colorectal cancer risk

Purpose

Colorectal cancer (CRC) is one of the common cancers with a high mortality rate worldwide. In Iran, there has been a trend of increased incidence of colorectal cancer in the last three decades that necessitates the early diagnosis. Genetic factors have an influential role in its etiology along with the conventional risk factors such as age, diet, and lifestyle. Results from GWAS have shown significant associations between SMAD7 gene variants and risk of CRC. This study aimed to assess the association of certain polymorphisms as well as haplotypes of this gene and risk of colorectal cancer.

Methods and materials

This study was designed as a case–control association study. After obtaining ethical approval and informed consent, blood samples from 209 patients with colorectal cancer were collected and DNA was extracted. Four variants: rs4939827, rs34007497, rs8085824 and rs8088297 were genotyped using ARMS-PCR method.

Results

SMAD7 rs4939827 in the recessive and co-dominant models was associated with colorectal cancer risk [TT/CT + CC: OR = 2.90, 95%CI (1.38–6.09), p = 0.005; CC + TT/CT: OR = 1.66, 95%CI (1.00–2.75), p = 0.01]. Haplotype analysis indicated that some SNP combinations including two for-SNPs haplotypes of T-T-C-C and T-C-C-A were significantly associated with CRC risk.

Conclusion

Based on the identified association of SMAD7 gene variations and haplotypes with colorectal cancer risk in our population, genetic variations in this gene region may have a role in CRC development. This data may shed light on the genetic predisposition of CRC which involves different pathways including TGF-β.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-021-01150-3.

Interactions Between Vitamin D and Calcium Intake, Vitamin D Receptor Genetic Polymorphisms, and Colorectal Cancer Risk

BACKGROUND

Vitamin D has anticarcinogenic properties and acts through vitamin D receptor (VDR) to carry out its functions.

AIMS

This study explored the independent and combined effects of dietary vitamin D and calcium, and VDR genetic polymorphisms on colorectal cancer risk in a Chinese population.

METHODS

This ongoing case-control study recruited 488 cases with histologically confirmed colorectal cancer and 496 sex- and age-matched controls. Vitamin D and calcium intakes were assessed by a validated food frequency questionnaire, and VDR genotype was conducted for Fok I (rs2228570), Bsm I (rs1544410), Apa I (rs7975232), and Taq I (rs731236). Unconditional logistic regression was used to calculate odds ratio and 95% confidence interval after adjusting for various confounders.

RESULTS

No significant association was found between Fok I, Bsm I, Apa I, Taq I, and colorectal cancer risk. Higher intakes of dietary vitamin D and calcium were associated with 47% and 50% reduction in colorectal cancer risk. Significant interaction was observed between dietary vitamin D intake and Apa I polymorphisms in relation to colorectal cancer risk (P_interaction = 0.006). Subjects with higher dietary vitamin D intake and mutant Apa I A allele had a substantially decreased risk of colorectal cancer compared to Apa I aa carriers with lower vitamin D intake.

CONCLUSIONS

Our study supports that Apa I may interact with dietary vitamin D intake on colorectal cancer risk. However, no interactions were found between dietary vitamin D or calcium intakes and Fok I, Bsm I, and Taq I in relation to colorectal cancer risk.

Ethnicity as modifier of risk for Vitamin D receptors polymorphisms: Comprehensive meta-analysis of all cancer sites

Vitamin D receptors polymorphisms are found to be associated with several cancers. Since their prevalence vary across ethnicities and ethnicity itself seems to influence the cancer risk, a comprehensive meta-analysis was performed to investigate the role of VDR Fok1, Bsm1, Taq1, Apa1, Cdx2 and cancer risk at specific organ sites. Odds ratios, calculated with random-effects models, summarized one-hundred-ninety-two independent studies for twenty-two cancer sites. Evidence was provided that Fok1, Bsm1, Cdx2, Apa1 and Taq1 are linked to cancer susceptibility for colorectal, lung, ovarian, skin, multiple myeloma and brain cancer. Stratifying by ethnicity, some differences were found, partially explained by minor allele frequency (MAF), for colorectal cancer, ovarian and prostate cancer in Caucasian and prostate cancer in Asian populations. In summary, ethnicity may be a modifier of cancer risk, in particular for hormone dependent cancers and it should be considered evaluating the effect of VDR on cancer risk.

Vitamin D Receptor Polymorphisms and Cancer

Increasing scientific evidence supports the link between vitamin D and cancer risk. The active metabolite 1,25(OH)2D exerts its activity by binding to the vitamin D receptor (VDR), an intracellular receptor that mediates transcriptional activation and repression of target genes. The binding of 1,25(OH)2D to VDR is able to regulate hundreds of different genes. VDR is active in virtually all tissues including the colon, breast, lung, ovary, bone, kidney, parathyroid gland, pancreatic b-cells, monocytes, T lymphocytes, melanocytes, keratinocytes, and also cancer cells.The relevance of VDR gene restriction fragment length polymorphisms for various types of cancer has been investigated by a great number of studies.We have carried out a systematic review of the literature to analyze the relevance of more VDR polymorphisms (Fok1, Bsm1, Taq1, Apa1, and Cdx2) for individual malignancies considering ethnicity as a key factor for heterogeneity.Up to December 2018, we identified 176 independent studies with data to assess the risk of breast, prostate, colorectal, skin (melanoma and non-melanoma skin cancer), lung, ovarian, kidney, bladder, gallbladder, esophageal, thyroid, head and neck, liver and pancreatic cancer, oral squamous cell carcinoma, non-Hodgkin lymphoma, multiple myeloma and sarcoma.Significant associations with VDR polymorphisms have been reported for prostate (Fok1, Bsm1, Taq1, Apa1, Cdx2), breast (Fok1, Bsm1, Taq1, Apa1, CdX2), colorectal (Fok1, Bsm1, Taq1, Apa1), and skin cancer (Fok1, Bsm1, Taq1). Very few studies reported risk estimates for the other cancer sites.Conflicting data have been reported for most malignancies, and at present, it is still not possible to make any definitive statements about the importance of the VDR genotype for cancer risk. It seems probable that other factors such as ethnicity, phenotype, 25(OH)D plasma levels, and UV radiation exposure play a role as confounding factors and introduce heterogeneity.To conclude, there is some indication that VDR polymorphisms may modulate the risk of some cancer sites and in future studies VDR genetic variation should be integrated also with assessment of vitamin D status and stratified by ethnicity.

Association between Vitamin D Receptor Single-Nucleotide Polymorphisms and Colorectal Cancer in the Thai Population: A Case-Control Study

Vitamin D and its cognate intracellular nuclear receptor, namely, vitamin D receptor (VDR), are involved in the regulation of a variety of body metabolic processes, immune function, and oncogenesis. A large number of studies demonstrated the association of low vitamin D levels and variations in five common single nucleotide polymorphisms (SNPs), FokI, BsmI, Tru9I, ApaI, and TaqI, with the risk of several cancers, including colorectal cancers. However, these associations vary among different populations. This case-control study was aimed at analysing whether common single-nucleotide polymorphisms (SNPs) and haplotypes of the vitamin D receptor (VDR) gene contribute to colorectal carcinogenesis in the Thai population. We enrolled 364 Thai participants from King Chulalongkorn Memorial Hospital between 2014 and 2015. Half of the participants underwent colonoscopy and showed a normal colon without polyps (control group) and another half were newly diagnosed patients with colorectal cancer (CRC) by colonoscopy during the index period, were under treatment, or were followed up at the outpatient clinic (case group). Differences in allele and genotype frequencies of five common VDR SNPs, between the case and control groups, were the primary outcome measures. Differences in haplotype frequencies of the five SNPs between the case and control groups were the secondary outcome measures. Among the 364 participants, baseline characteristics were not significantly different between the case and control groups, except for the higher proportion of males in the CRC group. The mean vitamin D level was also not significantly different between the case and control groups (24.6 ± 9.1 vs. 25.3 ± 10.6 ng/mL, p = 0.52). None of the five VDR SNPs was associated with CRC development (p > 0.05). However, haplotype analysis of these polymorphisms demonstrated that the AGGT haplotype was associated with a decreased risk of CRC (odds ratio 0.24, 95% confidence interval 0.07-0.81, p = 0.01). The AGGT haplotype was associated with a lower risk of CRC in the Thai population. This genetic linkage might support the role of vitamin D in colorectal carcinogenesis. However, this finding requires further study within a larger population and a multivariate analysis of other established risk factors.

The Role of Vitamin D Receptor Gene Polymorphisms in Colorectal Cancer Risk

Vitamin D deficiency has been associated with increased colorectal cancer (CRC) incidence risk and mortality. Vitamin D mediates its action through the binding of the vitamin D receptor (VDR), and polymorphisms of the VDR might explain these inverse associations. The aim of the study was the investigation of the relevance of rs731236; Thermus aquaticus I (TaqI), rs7975232; Acetobacter pasteurianus sub. pasteurianus I (ApaI), rs2228570; Flavobacterium okeanokoites I (FokI) and rs1544410, Bacillus stearothermophilus I (BsmI) polymorphisms of the VDR gene to colorectal carcinogenesis (CRC) and progression. Peripheral blood was obtained from 397 patients with early operable stage II/III (n = 202) and stage IV (n = 195) CRC. Moreover, samples from 100 healthy donors and 40 patients with adenomatous polyps were also included as control groups. Genotyping in the samples from patients and controls was performed using polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP). A significant association was revealed between all four polymorphisms and cancer. Individuals with homozygous mutant (tt, aa, ff or bb) genotypes were more susceptible to the disease (p < 0.001). All of the mutant genotypes detected were also significantly associated with stage IV (p < 0.001), leading to significantly decreased survival (p < 0.001). Moreover, all four polymorphisms were significantly associated with KRAS (Kirsten ras oncogene) mutations and Toll-like receptor (TLR2, TLR4 and TLR9) genetic variants. In multivariate analysis, tt, aa and ff genotypes emerged as independent factors associated with decreased overall survival (OS) (p = 0.001, p < 0.001 and p = 0.001, respectively). The detection of higher frequencies of the VDR polymorphisms in CRC patients highlights the role of these polymorphisms in cancer development and progression.

Determination of Cut Point in the Age of Colorectal Cancer Diagnosis Using a Survival Cure Model

Background and Objectives:

Colorectal Cancer (CRC) is the fourth cancer-related cause of death worldwide. CRC is a multi-stage cancer, which is curable during the early stages of the disease. Therefore, determining the time of cut-point existence could improve treatment planning and help directly allocate resources. This study aims to determine the cut point in the age of CRC diagnosis.

Methods:

This study, covering the course 1985 to 2012, consisted of 345 colorectal cancer patients registered in Taleghani Hospital, Tehran, Iran and followed up to 2013. The cut-point in the age of CRC diagnosis was obtained using a mixture cure model. The data were analyzed using SPSS and R, V. 20 and 2.15.0, respectively.

Results:

The results showed that the cut point in the age of CRC diagnosis was 50 years. Based on our estimation, 65% of the patients diagnosed with CRC at or younger than 50 were cured, while 31% of them diagnosed older than 50 were cured, and the younger group had a better survival over the older group.

Conclusion:

Since access to a cut-point and analysis of created prognostic groups are important in screening and treatment planning, our results suggested that it is better to estimate the cut-point in the age of curable cancers in early stages via survival cure models, and the cure rate would increase by CRC timely screening.

Vitamin D receptor gene polymorphisms in ocular surface squamous cell neoplasms

PURPOSE

To investigate vitamin D receptor polymorphisms in ocular surface squamous cell neoplasm and to evaluate the relationship between the identified polymorphisms and susceptibility to ocular surface squamous cell neoplasm and the clinical course.

MATERIALS AND METHODS

A totala of 70 patients with ocular surface squamous cell neoplasm (study group) and 75 healthy age and gender-matched individuals (control group) were included in the study. Vitamin D receptor FokI and BsmI polymorphisms were examined. The relationships between histopathological diagnosis, recurrence rates, tumor stage, and identified polymorphisms were investigated.

RESULTS

Histopathologically, 43 of the cases were squamous cell carcinoma and 27 of the cases were conjunctival intraepithelial neoplasia. The frequency of FokI (FF, Ff, ff) and BsmI (BB, Bb, bb) polymorphism genotype of vitamin D receptor gene were similar in the groups. The frequency of polymorphism (heterozygous or homozygous) for BsmI (Bb and bb) was significantly higher (p = 0.046) in the study group, while no difference was found between the groups in terms of polymorphic carriers (heterozygous or homozygous) for FokI. There was no correlation between tumor stage, recurrence-polymorphism frequency, and patient age-polymorphism frequency.

CONCLUSION

It is known that active vitamin D inhibits the growth of cancer cells by binding to vitamin D receptor with regulation of genes responsible for cell proliferation. The presence of BsmI polymorphism in vitamin D receptor, in particular bb genotype and b allele, appears to be associated with the susceptibility of ocular surface squamous cell neoplasm. BsmI gene polymorphisms of vitamin D receptor might play an effective role in the formation, progression, and in the course of ocular surface squamous cell neoplasm.

The burgeoning role of cytochrome P450-mediated vitamin D metabolites against colorectal cancer

The metabolites of vitamin D₃ (VD3) mediated by different cytochrome P450 (CYP) enzymes, play fundamental roles in many physiological processes in relation to human health. These metabolites regulate a variety of cellular signal pathways through the direct binding of activated vitamin D receptor/retinoic X receptor (VDR/RXR) heterodimeric complex to specific DNA sequences. Thus, the polymorphisms of VDR and VD3 metabolizing enzymes lead to differentiated efficiency of VD3 and further affect serum VD3 levels. Moreover, VDR activation is demonstrated to inhibit the growth of various cancers, including colorectal cancer. However, excessive intake of vitamin D may lead to hypercalcemia, which limits the application of vitamin D tremendously. In this review, we have summarized the advances in VD3 research, especially the metabolism map of VD3 and the molecular mechanisms of inhibiting growth and inducing differentiation in colorectal cancer mediated by VDR-associated cellular signal pathways. The relationship between VDR polymorphism and the risk of colorectal cancer is also illustrated. In particular, novel pathways of the activation of VD3 started by CYP11A1 and CYP3A4 are highlighted, which produce several noncalcemic and antiproliferative metabolites. At last, the hypothesis is put forward that further research of CYP-mediated VD3 metabolites may develop therapeutic agents for colorectal cancer without resulting in hypercalcemia.

Associations between VDR gene polymorphisms and colorectal cancer susceptibility: an updated meta-analysis based on 39 case-control studies

BACKGROUND

Recent studies have reported the associations between vitamin D receptor (VDR) polymorphisms and colorectal cancer (CRC), but the results were not always consistent. This meta-analysis aims to evaluate whether VDR polymorphisms are associated with CRC susceptibility.

MATERIALS AND METHODS

Studies on the associations between VDR polymorphisms and CRC were retrieved from the Web of Science, PubMed, the Chinese Biomedical Database (CBM), Chinese National Knowledge Infrastructure (CNKI) and Wanfang (Chinese) databases. The odds ratio (OR) with 95% confidence intervals (CIs) was obtained.

RESULTS

Thirty-nine articles met all inclusion criteria and were included in the meta-analysis including 22101 CRC cases and 23696 healthy controls. The 39 articles consisted of five VDR gene polymorphisms including ApaI, FokI, BsmI, TaqI and Cdx2. The results of meta-analysis showed that the FokI polymorphism was on the fringe of statistically significant in the comparisons of F allele vs. f allele in fixed model (OR = 1.029, 95% CI = 0.999-1.059, Praw = 0.057, PFDR = 0.057). Moreover, for the associations between BsmI polymorphism with CRC, We observed significant differences in allele frequencies, the homozygous model and the dominant model between CRC patients and healthy controls (B vs. b: OR = 0.862, 95% CI = 0.761-0.976, Praw = 0.019, PFDR = 0.019; BB vs. bb: OR = 0.786, 95% CI = 0.636-0.972, Praw = 0.026, PFDR = 0.039; BB + Bb vs. bb: OR = 0.934, 95% CI = 0.888-0.982, Praw = 0.008, PFDR = 0.024, respectively).

CONCLUSIONS

This meta-analysis suggests that BsmI is associated with CRC risk and FokI might be a risk factor for CRC. However, these associations with CRC need further studied.

Association of the vitamin D receptor FokI gene polymorphism with sex- and non-sex-associated cancers: A meta-analysis

Currently higher morbidity and mortality rates are observed in cancer diseases, especially sex-dependent cancers. A positive role of endogenous vitamin D concentration in cancer diseases has been reported in many publications. Furthermore, there has been observed a relationship between serum vitamin D and testosterone concentrations in an elderly Caucasian population carrying the vitamin D receptor FokI gene polymorphism. The aim of this study was to investigate whether the vitamin D receptor FokI polymorphism is associated with cancerogenesis in sex-dependent cancers. The MEDLINE and ResearchGate databases were used to search for articles up to January 2017, and 96 articles concerning the FokI polymorphism were chosen. Odds ratios with 95% confidence intervals were used to assess the strength of associations between polymorphisms of vitamin D receptor and cancer risk in the described populations. The fixed-effects model and the DerSimonian-Laird random-effects model (with weights based on the inverse variance) were used to calculate summary odds ratios, and both within- and between-study variation were considered. Generally, the F variant reduces the risk of cancer by 4% (odds ratio = 0.96, p value = 0.0057). This effect is particularly evident in female sex-associated cancers (odds ratio = 0.96, 95% confidence interval: 0.93-0.99, p value = 0.0259), but it is not observed in non-sex-associated cancers. Polymorphism FokI is associated with breast and ovarian cancers.

Association between vitamin D receptor gene FokI polymorphism and skeletal fluorosis of the brick-tea type fluorosis: a cross sectional, case control study

BACKGROUND

Brick-tea type fluorosis is a public health concern in the north west area of China. The vitamin D receptor (VDR)-FokI polymorphism is considered to be a regulator of bone metabolism and calcium resorption. However, the association of VDR-FokI polymorphism with the risk of brick-tea type fluorosis has not been reported.

MATERIALS AND METHODS

A cross sectional, case control study was conducted in three provinces (Inner Mongolia, Qinghai and Sinkiang) in China. The fluoride content of Brick-tea water and urine was tested using the standards GB 1996-2005 and WS/T89-2006 (China), respectively. Skeletal fluorosis was diagnosed using the standard WS/192-2008 (China). The VDR-FokI polymorphism was detected by the Sequenom MassARRAY system.

RESULT

Compared with carriers of the CC genotype, participants with the CT/TT genotype had a significantly decreased risk of skeletal fluorosis (OR=0.761 (95% CI 0.580 to 0.997)), after adjustment for risk factors. When investigated among ethnic groups, the protective effect of the CT/TT genotype was limited in the Mongolian participants (OR=0.525 (95% CI 0.278 to 0.991)). Moreover, the interaction of VDR-FokI with risk factors was only found in Mongolian participants: the protective effect of the CT/TT genotype was limited to participants with >7.0 mg/day daily intake of tea fluoride (OR=0.085 (95% CI 0.009 to 0.851), participants with >3.2 mg/L urine fluoride (OR=0.103 (95% CI 0.017 to 0.633)) or participants aged 46-65 years (OR=0.404 (95% CI 0.177 to 0.922).

CONCLUSIONS

Our data suggest that the CT/TT genotype of VDR-FokI may be a protective factor for brick-tea type skeletal fluorosis, and this effect is pronounced in Mongolian participants.

Association of Vitamin D Receptor Gene Polymorphisms with Colorectal Cancer in a Saudi Arabian Population

BACKGROUND

Vitamin D, causally implicated in bone diseases and human malignancies, exerts its effects through binding to the vitamin D receptor (VDR). VDR is a transcription factor modulating the expression of several genes in different pathways. Genetic variants in the VDR gene have been associated with several cancers in different population including colorectal cancer.

OBJECTIVE

To assess the association of VDR gene polymorphisms in relation with colorectal cancer (CRC) in a Saudi population.

METHODS

The polymorphisms of VDR gene (BsmI, FokI, ApaI and TaqI) were analyzed by the polymerase chain reaction amplification of segments of interest followed by Sanger sequencing. One hundred diagnosed CRC patients and 100 healthy control subjects that were age and gender matched were recruited.

RESULTS

We did not observe significant association of any of the four VDR polymorphisms with colorectal cancer risk in the overall analysis. Although not statistically significant, the AA genotype of BsmI conferred about two-fold protection against CRCs compared to the GG genotype. Stratification of the study subjects based on age and gender suggests statistically significant association of CRC with the 'C' allele of ApaI in patients >57 years of age at disease diagnosis and BsmI polymorphism in females. In addition, statistically significant differences were observed for the genotypic distributions of VDR-BsmI, ApaI and TaqI SNPs between Saudi Arabian population and several of the International HapMap project populations.

CONCLUSION

Despite the absence of correlation of the examined VDR polymorphisms with CRCs in the combined analysis, ApaI and BsmI loci are statistically significantly associated with CRC in elderly and female patients, respectively. These findings need further validation in larger cohorts prior to utilizing these SNPs as potential screening markers for colorectal cancers in Saudi population.

Associations between vitamin D receptor (VDR) gene polymorphisms and colorectal cancer risk and effect modifications of dietary calcium and vitamin D in a Japanese population

Much interest has been drawn to possible associations between vitamin D receptor (VDR) gene polymorphisms and colorectal cancer risk in conjunction with potentially protective effects of calcium and vitamin D. In a study of 685 cases of colorectal cancer and 778 community controls in Japan, we examined the associations of the FokI, BsmI, ApaI, and TaqI polymorphisms with colorectal cancer risk and effect modification by dietary calcium and vitamin D. Genotypes were determined by the PCR-RFLP method. The ApaI polymorphism seemed to be associated with a decreased risk of colorectal cancer, particularly of rectal cancer. The adjusted odds ratio of colorectal cancer for the ApaI AA and Aa genotypes combined versus the aa genotype was 0.83 (95% confidence interval [CI] 0.67-1.02), and the corresponding value for rectal cancer was 0.75 (95%CI 0.56-0.99). A decreased risk of colorectal cancer for the ApaI AA and Aa genotypes combined was more evident in individuals with high calcium intake (interaction p=0.055). The FokI polymorphism seemed to be associated with a decreased risk of colon cancer among those with high vitamin D intake (interaction p=0.09). The BsmI and TaqI polymorphisms were unrelated to colorectal cancer risk, and the null associations were not modified by calcium or vitamin D intake. In conclusion, the ApaI polymorphism may be associated with a decreased risk of colorectal cancer in Japanese, dependent on dietary calcium intake.

Vitamin D, Cancer Risk, and Mortality

Antiproliferative effects of 1,25-dihydroxyvitamin D, the biologically active form of vitamin D, are well established in various cell types by influencing cell differentiation and decreasing cell proliferation, growth, invasion, angiogenesis, and metastasis. Several meta-analyses showed that low serum levels of 25(OH)D was associated with colorectal cancer and overall mortality, while the association with cancer mortality was less consistent. VDR is a crucial mediator for the cellular effects of vitamin D and conflicting data have been reported for most malignancies. Beyond VDR, the biological effects of vitamin D are mediated by the vitamin D-binding protein. The GC (group-specific component) gene, encoding DBP, is highly polymorphic and several polymorphisms were investigated in association with cancer development with controversial results. Vitamin D supplementation was found to be associated with a reduced risk of overall mortality, reviewing all published trials on healthy subjects, whereas the evidence of an effect on cancer risk and mortality is less clear. Furthermore, long-term health effects of high doses of vitamin D, extended duration of supplementation, and the association with different baseline vitamin D levels remain to be investigated. In summary, epidemiological and preclinical studies support the development of vitamin D as preventative and therapeutic anticancer agents, with significant associations especially found for low vitamin D status with overall mortality and cancer outcome, more than cancer incidence. However, a definitive conclusion cannot be drawn and only large randomized clinical trials, both in healthy subjects and in cancer patients, will allow to draw definitive conclusions on the effect of vitamin D supplementation on cancer risk, prognosis, and mortality.

Vitamin D receptor BsmI polymorphism and colorectal cancer risk: an updated analysis

BACKGROUND

Previous studies have investigated the association between the vitamin D receptor (VDR) BsmI polymorphism and colorectal cancer (CRC) susceptibility, but the results were conflicting. The aim of this study is to quantitatively summarize the relationship between this polymorphism and CRC risk.

MATERIALS AND METHODS

Two investigators independently searched the Medline, Embase, China National Knowledge Infrastructure (CNKI) and Chinese Biomedicine databases for studies published before November 2013. Summary odds ratios (ORs) and 95% confidence intervals (95%CIs) for VDR BsmI polymorphism and CRC were calculated in a fixed- effects model (the Mantel-Haenszel method) and a random-effects model (the DerSimonian and Laird method) when appropriate.

RESULTS

This meta-analysis included 14 case-control studies, which included 10,822 CRC cases and 11,779 controls. Overall, the variant genotype (BB) of the BsmI was associated with a lower CRC risk when compared with the wild-type bb homozygote (OR=0.66, 95%CI: 0.49-0.88). Similarly, a decreased CRC risk was also found in the dominant and recessive models. When stratifying for ethnicity, source of controls, and study sample size, associations were observed among Caucasians, population-based studies and studies with large study sample size (>1000 subjects). Limiting the analysis to the studies within Hardy-Weinberg equilibrium, the results were persistent and robust. No publication bias was found in the present study.

CONCLUSIONS

This updated meta-analysis suggests that the VDR BsmI polymorphism may be associated with a moderate protective effect against CRC.

Vitamin D receptor polymorphism FokI and cancer risk: a comprehensive meta-analysis

Numerous studies investigated the associations of VDR polymorphisms with various types of cancer, suggesting an influence on cancer risk. FokI is one of the most frequently analysed polymorphisms but the results from single studies are contradictory. We performed a meta-analysis looking at the association between the FokI and all cancer sites and investigating sources of heterogeneity. We identified 77 independent studies up to April 2014. We presented the summary odds ratios (SORs) by cancer sites, ethnicity and study features. We found a significant association between FokI and ovarian cancer for ff genotype versus FF with no heterogeneity: SOR = 1.20 (95% CI: 1.02-1.41, I (2) = 0%). Moreover, we found a significant increased risk of any cancer: SOR = 1.08 (95% CI: 1.01-1.16, I (2) = 58%). A significant increased risk of any cancer is confirmed among Caucasian, among studies in Hardy-Weinberg equilibrium and nested case-control studies. Furthermore, among studies in Hardy-Weinberg equilibrium, skin cancer was found significantly associated with FokI: SOR = 1.24 (95% CI: 1.01-1.54; I (2) = 24%) for ff versus FF. The estimated number of cases attributable to ff genotype is 4221 for ovarian cancer and 52858 for skin cancer worldwide each year. No indication for publication bias was found for any cancer site. In conclusion, we found an overall significant association of FokI polymorphism with any cancer, with differential effect by ethnicity. In particular, the summary estimates indicate an increase risk for ovarian and skin cancer for ff versus FF. However, other factors may act modifying the association, and further studies are needed to clarify the impact on cancer risk.

Vitamin D receptor and colorectal cancer

Colorectal cancer (CRC) is the third cause of cancer-related morbidity and mortality in America following lung cancer and stomach cancer. In China and other Asian countries, increasingly Westernized diets have led to a high incidence of CRC. The vitamin D receptor (VDR) can mediate 1,25(OH)₂D₃ to regulate cell growth and differentiation in a variety of normal tissues or tumor tissues. VDR gene polymorphisms are closely related to the occurrence and development of CRC. This article summarizes the recent progress in understanding the relationship between VDR and CRC in terms of the structure and function of VDR, mechanisms of CRC inhibition, correlation between VDR polymorphisms and CRC, and the development of analogs of VDR ligands.

Protective role of the vitamin D receptor

Vitamin D receptor (VDR) is found in most tissues, not just those participating in the classic actions of vitamin D such as bone, gut, and kidney. The nonclassic actions are therefore potential targets for the active metabolite of vitamin D, 1,25(OH)₂D₃. This review is intended to highlight the actions of VDR in role of protection. Medline is searched for articles describing actions of VDR on secondary hyperparathyroidism, diabetic nephropathy, hypertension and atherosclerosis. VDR exerts its protective activities through the following mechanisms: inhibition of renin-angiotensin system (RAS); regulation of proliferation and differentiation; reduction of proteinuria; anti-inflammation and anti-fibrosis. The nonclassic actions of VDR provide a number of potential new clinical applications for 1,25(OH)₂D₃ and its analogs. We believe 1,25(OH)₂D₃/VDR can be of particular value in the prevention of kidney-related diseases.

Association of vitamin D receptor gene polymorphisms with colon cancer

OBJECTIVE

In this study, we investigated the association of two vitamin D receptor (VDR) polymorphisms BsmI and TaqI with colon cancer in a Caucasian population.

METHODS

The VDR gene polymorphisms BsmI and TaqI were detected by polymerase chain reaction (PCR), restriction fragment length polymorphism (RFLP)-genotyping assays by using endonucleases BsmI and TaqI, and an agarose gel electrophoresis technique in a series of 43 colon cancer patients and 42 healthy controls.

RESULTS

Allele frequencies and genotype distributions were found to be similar in both cases and controls. When homozygous carriers and heterozygotes were combined for each allele, alleles B and T were found to be more common in the control group (p=0.039, χ(2)=4.276, odds ratio [OR]=0.312, 95% confidence interval [CI]=0.100-0.973 and p=0.039, χ(2)=4.258, OR=0.254, 95% CI=0.064-1.000, respectively). When genotypes were analyzed as pairs, the Bb/TT variant was higher in the control group at a statistically high significance (p=0.001, χ(2)=11.854, OR=0.122, 95% CI=0.032-0.460).

CONCLUSION

The alleles B and T and the genotype combination Bb/TT were found to be higher in the control group, and thus BsmI and TaqI polymorphisms of the VDR gene may be possible risk factors for colorectal carcinogenesis.

Vitamin D receptor gene polymorphism and its association with Parkinson's disease in Chinese Han population

Vitamin D plays an important role in neurodegenerative disorders as a crucial neuro-immunomodulator, and accumulating data have provided evidence for that vitamin D receptor (VDR) gene is a candidate gene for susceptibility to Parkinson's disease (PD). In this study, we performed a case-control study to demonstrate whether the risk for the development of onset of sporadic PD might be influenced by VDR gene polymorphisms in a Chinese cohort. Two hundred and sixty PD patients and 282 matched-healthy controls were genotyped for two representative single nucleotide polymorphisms (SNPs) in VDR gene (FokI C/T and BsmI G/A) by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) analysis in. Results from our study revealed that FokI C allele carriers were likely to associate with an increased risk of PD (P=0.004) as well as early-onset PD (EOPD) (P=0.010). Moreover, the frequency of FokI C allele was significantly increased in PD group and late-onset PD (LOPD) group relative to the control groups respectively (P=0.023 and P=0.033, respectively). For BsmI polymorphisms, no significant difference in genotype or allele distribution was found between PD patients and the controls, as well as gender- and age-related differences between PD patients and the controls subgroup. This study demonstrated a possible association between the VDR FokI T/C polymorphism and PD, indicating that VDR polymorphisms may well change genetic susceptibility to sporadic PD in a Han Chinese population.

Vitamin D receptor gene polymorphisms and colorectal cancer risk: a systematic meta-analysis

AIM

To investigate the relationship between polymorphisms present in the vitamin D receptor (VDR) gene and colorectal cancer risk, a systematic meta-analysis of population-based studies was performed.

METHODS

A total of 38 relevant reports published between January 1990 and August 2010 were identified, of which only 23 qualified for this meta-analysis based on our selection criteria. Five polymorphic variants of the VDR gene, including Cdx-2 (intron 1e) and FokI (exon 2) present in the 5' region of the gene, and BsmI (intron 8), ApaI (intron 8), and TaqI (exon 9) sites present in the 3' untranslated region (UTR), were evaluated for possible associations with colorectal cancer risk. Review manager 4.2 was used to perform statistical analyses.

RESULTS

In the meta-analysis performed, only the BsmI polymorphism was found to be associated with colorectal cancer risk. In particular, the BsmI B genotype was found to be related to an overall decrease in the risk for colorectal cancer [BB vs bb: odds ratio (OR) = 0.87, 95% CI: 0.80-0.94, P = 3 × 10(-4); BB vs Bb + bb: OR = 0.90, 95% CI: 0.84-0.97, P = 5 × 10(-4)]. Moreover, in subgroup analyses, the BsmI B genotype was significantly associated with colon cancer, and not rectal cancer. An absence of between-study heterogeneity was also observed.

CONCLUSION

A meta-analysis of 23 published studies identified the BsmI polymorphism of the VDR gene to be associated with an increased risk of colon cancer.

The -4817 G>A (rs2238136) variant of the vitamin D receptor gene: a probable risk factor for colorectal cancer

Vitamin D appears to have anti-tumor activities in the large bowel. Our aim was to investigate whether -4817 G>A (rs2238136) polymorphism located at 5'-untranslated region (5'-UTR) of the human vitamin D receptor (VDR) gene was associated with colorectal cancer (CRC) risk. We conducted a case-control study and VDR genotypes, determined by Bpu10I restriction endonuclease digestion of PCR-amplified DNA, were performed on 327 cases with CRC and 327 controls. The distribution of VDR -4817 G>A genotypes and alleles differed significantly between cases with CRC and controls even after adjustment for confounding factors such as age, BMI, sex, and smoking status. Individuals carrying the "AA" genotype had a 2.09-fold increased risk compared with those with "GG" genotype (P = 0.016, OR = 2.09, 95% CI = 1.15-3.78) and a 1.87-fold increased risk compared with those with "GG and GA" genotypes (P = 0.033, OR = 1.87, 95% CI = 1.05-3.33) for CRC. Furthermore, the VDR "A" allele was significantly overrepresented in cases with CRC than controls (P = 0.044; OR = 1.28, 95% CI = 1.01-1.63). Interestingly, the analysis of the SNP revealed that all these associations were stronger for women subjects than for all subjects combined. These data indicated for the first time a direct association between "AA" genotype of VDR gene -4817 G>A polymorphism and CRC, with a stronger association for female subjects. However, our findings remain to be confirmed in other populations.

Genetic associations in the vitamin D receptor and colorectal cancer in African Americans and Caucasians

Low vitamin D levels are associated with an increased incidence of colorectal cancer (CRC) and higher mortality from the disease. In the US, African Americans (AAs) have the highest CRC incidence and mortality and the lowest levels of vitamin D. Single nucleotide polymorphisms (SNPs) in the vitamin D receptor (VDR) gene have been previously associated with CRC, but few studies have included AAs. We studied 795 AA CRC cases and 985 AA controls from Chicago and North Carolina as well as 1324 Caucasian cases and 990 Caucasian controls from Chicago and Spain. We genotyped 54 tagSNPs in VDR (46586959 to 46521297 Mb) and tested for association adjusting for West African ancestry, age, gender, and multiple testing. Untyped markers were imputed using MACH1.0. We analyzed associations by gender and anatomic location in the whole study group as well as by vitamin D intake in the North Carolina AA group. In the joint analysis, none of the SNPs tested was significantly associated with CRC. For four previously tested restriction fragment length polymorphisms, only one (referred to as ApaI), tagged by the SNP rs79628898, had a nominally significant p-value in AAs; none of these polymorphisms were associated with CRC in Caucasians. In the North Carolina AAs, for whom we had vitamin D intake data, we found a significant association between an intronic SNP rs11574041 and vitamin D intake, which is evidence for a VDR gene-environment interaction in AAs. In summary, using a systematic tagSNP approach, we have not found evidence for significant associations between VDR and CRC in AAs or Caucasians.

Case-control study of vitamin D, dickkopf homolog 1 (DKK1) gene methylation, VDR gene polymorphism and the risk of colon adenoma in African Americans

BACKGROUND

There are sparse data on genetic, epigenetic and vitamin D exposure in African Americans (AA) with colon polyp. Consequently, we evaluated serum 25(OH) D levels, vitamin D receptor (VDR) polymorphisms and the methylation status of the tumor suppressor gene dickkopf homolog 1 (DKK1) as risk factors for colon polyp in this population.

METHODS

The case-control study consisted of 93 patients with colon polyp (cases) and 187 healthy individuals (controls) at Howard University Hospital. Serum levels of 25(OH)D (including D3, D2, and total) were measured by liquid chromatography-mass spectrometry. DNA analysis focused on 49 single nucleotide polymorphisms (SNPs) in the VDR gene. Promoter methylation analysis of DKK1 was also performed. The resulting data were processed in unadjusted and multivariable logistic regression analyses.

RESULTS

Cases and controls differed in vitamin D status (D(3)<50 nmol/L: Median of 35.5 in cases vs. 36.8 in controls nmol/L; P = 0.05). Low levels of 25(OH)D(3) (<50 nmol/L) were observed in 86% of cases and 68% of controls and it was associated with higher risks of colon polyp (odds ratio of 2.7, 95% confidence interval 1.3-3.4). The SNP analysis showed no association between 46 VDR polymorphisms and colon polyp. The promoter of the DKK1 gene was unmethylated in 96% of the samples.

CONCLUSION

We found an inverse association between serum 25(OH)D(3) and colon polyp in AAs. VDR SNPs and DKK1 methylation were not associated with colon polyp. Vitamin D levels may in part explain the higher incidence of polyp in AAs.

Meta-analyses of vitamin D intake, 25-hydroxyvitamin D status, vitamin D receptor polymorphisms, and colorectal cancer risk

BACKGROUND

Our objective was to conduct a systematic review and meta-analysis of prospective studies on colorectal cancer (CRC) and vitamin D intake and 25-hydroxyvitamin D status, as part of the World Cancer Research Fund Continuous Update Project. We also aimed at conducting meta-analysis of all studies on CRC and vitamin D receptor (VDR) single-nucleotide polymorphisms.

METHODS

Relevant studies were identified in PubMed (up to June 2010). Inclusion criteria were original and peer-reviewed publications with a prospective design (for studies on vitamin D intake or status). Random effects of dose-response meta-analyses were performed on cancer incidence.

RESULTS

We observed inverse associations of CRC risk with dietary vitamin D [summary relative risk (RR) per 100 IU/day = 0.95, 95% CI: 0.93-0.98; 10 studies; range of intake (midpoints) = 39-719 IU/day] and serum/plasma 25-hydroxyvitamin D (RR per 100 IU/L = 0.96, 0.94-0.97; 6 studies; range = 200-1,800 IU/L), but not with total vitamin D (5 studies). Supplemental (2 studies; range = 0-600 IU/day) and total (4 studies; range = 79-732 IU/day) vitamin D intake and 25-hydroxyvitamin D status (6 studies; range = 200-1,800 IU/L) were inversely associated with colon cancer risk. We did not observe statistically significant associations between FokI, PolyA, TaqI, Cdx2, and ApaI VDR polymorphisms and CRC risk. The BsmI polymorphism was associated with a lower CRC risk (RR = 0.57, 0.36-0.89 for BB versus bb, 8 studies).

CONCLUSIONS

These meta-analyses support the evidence of an inverse association between vitamin D intake, 25-hydroxyvitamin D status, and the BsmI VDR polymorphism and CRC risk.

IMPACT

Improving vitamin D status could be potentially beneficial against CRC incidence.

Vitamin D receptor gene polymorphism and bone mineral density in 0-6-year-old Han children

This study aims to investigate the four vitamin D receptor (VDR) gene single nucleotide polymorphisms and their possible relationship with bone mineral density (BMD) in Chinese 0-6-year-old Han children. Two hundred four 0-6-year-old Han children without metabolic bone disease were randomly recruited in Shanghai, China. The BMD of the middle tibia was measured by an ultrasonic bone density instrument. VDR genotypes were determined by polymerase chain reaction restriction fragment length polymorphism using endonuclease ApaI, BsmI, TaqI and FokI. The alleles of a, T, b and F and the genotypes of aa, TT, bb and Ff were predominant. The frequency alleles of a, T, b and F were, respectively, 70.6, 95.8, 95.3 and 57.6%. When the influences of confounders such as serum 25(OH)D, serum zinc and outdoor activities on BMD were removed, the genotypes of BsmI and FokI were found apparently to be related to BMD. The BMD of the Bb carrier was much lower than that of the bb carrier (22.00 ± 27.84 and 43.14 ± 31.98, P < 0.05). The BMD of the ff carrier was lower than that of the Ff or FF carrier (26.97 ± 34.22 and 37.95 ± 29.70 and 53.52 ± 30.35, P < 0.001), while the genotypes of ApaI and TaqI have no relation with BMD in 0-6-year-old Han children. These findings show that the Bb and ff genotypes of the VDR BsmI and FokI variants are significantly associated with a decreased BMD in Chinese Han children aged 0-6 years, while the VDR ApaI and TaqI polymorphisms are not significantly associated with it.

Start codon FokI and intron 8 BsmI variants in the vitamin D receptor gene and susceptibility to colorectal cancer

Epidemiological evidence suggests the protective effect of vitamin D against colorectal cancer (CRC) and the polymorphisms in vitamin D receptor (VDR) gene may influence the development of CRC. In this study the possible association of VDR FokI and BsmI gene polymorphisms with CRC risk was examined. A total of 904 subjects, including 452 cases with CRC and 452 controls were enrolled in this study. All 904 subjects were genotyped for VDR FokI and BsmI gene polymorphisms by PCR-RFLP method. We observed no significant difference in genotype and allele frequencies between the cases with CRC and controls for the both FokI and BsmI polymorphisms either before or after adjustment for confounding factors including age, BMI, sex, and smoking status. Furthermore, no evidence for effect modification of the association VDR gene FokI and BsmI variants and CRC by BMI, sex, or tumor site was observed. In addition, there was no significant difference in genotype and allele frequencies between the normal weight (BMI <25 kg/m(2)) cases with CRC and overweight/obese (BMI ≥25 kg/m(2)) cases with CRC for the two SNPs. Our results do not lend support to the hypothesis that VDR gene FokI and BsmI polymorphisms are associated with the risk of CRC. However, further studies are required to confirm this finding.

Vitamin D receptor gene ApaI polymorphism is associated with susceptibility to colorectal cancer

OBJECTIVES

The purpose of this study was to investigate vitamin D receptor (VDR) gene ApaI and TaqI polymorphisms in relation to the risk of colorectal cancer (CRC) in the Iranian population.

METHODS

Two single nucleotide polymorphisms in intron 8 (ApaI) and exon 9 (TaqI) of the VDR gene were genotyped in 160 subjects with CRC and 180 controls by use of the PCR-RFLP method.

RESULTS

The VDR ApaI genotype distribution differed significantly between subjects with CRC and controls. The ApaI "aa" genotype compared with "AA" genotype was associated with a 2.3-fold increased risk of CRC (P = 0.014; OR = 2.25, 95% CI = 1.18-4.28) and the difference remained significant after adjustment for age, BMI, sex, and smoking status (P = 0.014; OR = 2.32, 95% CI = 1.19-4.54). Furthermore, the ApaI "a" allele was significantly overrepresented in subjects with CRC than controls (P = 0.014; OR = 1.48, 95% CI = 1.08-2.02).

CONCLUSIONS

These findings suggest that VDR ApaI genotype "aa" is associated with increased risk of CRC in the Iranian population. However, these data remain to be confirmed in larger studies and in other populations.

Vitamin D receptor ligands, adenomatous polyposis coli, and the vitamin D receptor FokI polymorphism collectively modulate beta-catenin activity in colon cancer cells

The activity of beta-catenin, commonly dysregulated in human colon cancers, is inhibited by the vitamin D receptor (VDR), and this mechanism is postulated to explain the putative anti-cancer activity of vitamin D metabolites in the colon. We investigated the effect of a common FokI restriction site polymorphism (F/f) in the human VDR gene as well as the effect of anti-tumorigenic 1,25-dihydroxyvitamin D(3) (1,25D) and pro-tumorigenic lithocholic acid (LCA) VDR ligands on beta-catenin transcriptional activity. Furthermore, the influence of a major regulatory protein of beta-catenin, the APC tumor suppressor gene, on VDR-dependent inhibition of beta-catenin activity was examined. We report herein that beta-catenin-mediated transcription is most effectively suppressed by the VDR FokI variant F/M4 when 1,25D is limiting. Using Caco-2 colorectal cancer (CRC) cells, it was observed that VDR ligands, 1,25D and LCA, both suppress beta-catenin transcriptional activity, though 1,25D exhibited significantly greater inhibition. Moreover, 1,25D, but not LCA, suppressed endogenous expression of the beta-catenin target gene DKK-4 independent of VDR DNA-binding activity. These results support beta-catenin sequestration away from endogenous gene targets by 1,25D-VDR. This activity is most efficiently mediated by the FokI gene variant F/M4, a VDR allele previously associated with protection against CRC. Interestingly, we found the inhibition of beta-catenin activity by 1,25D-VDR was significantly enhanced by wild-type APC. These results reveal a previously unrecognized role for 1,25D-VDR in APC/beta-catenin cross talk. Collectively, these findings strengthen evidence favoring a direct effect on the Wnt-signaling molecule beta-catenin as one anti-cancer target of 1,25D-VDR action in the colorectum.

Review and meta-analysis on vitamin D receptor polymorphisms and cancer risk

It was suggested that vitamin D levels influence cancer development. The vitamin D receptor (VDR) is a crucial mediator for the cellular effects of vitamin D. Results from previous studies on the association of VDR polymorphisms with different cancer types are somewhat contradictory, and the role of VDR in the etiology of cancer is still equivocal. We therefore performed a meta-analysis on the association between the two most studied VDR polymorphisms (FokI and BsmI) and any cancer site. Up to January 2009, we identified 67 independent studies. We used random-effects models to provide summary odds ratio (SOR) for VDR polymorphisms and cancer. We tested homogeneity of effects across studies and publication bias and explored between-study heterogeneity. When comparing FokI ff with FF carriers, we found a significant increase in skin cancer [SOR; 95% confidence intervals (CIs): 1.30; 1.04-1.61] and breast cancer (SOR; 95%CI: 1.14; 1.03-1.27) risk. For the same genotype comparison, we found a significantly higher risk of cancer when we pooled estimates from cancer sites possibly associated with vitamin D levels (prostate, breast, skin, ovary, non-Hodgkin lymphoma and colorectal). A significant reduction in prostate cancer risk was observed for carriers of BsmI Bb compared with bb genotype (SOR; 95%CI: 0.83; 0.69-0.99). In Caucasian populations, both Bb and BB carriers had a significant reduced risk of cancer at any site. In conclusion, this meta-analysis showed that VDR FokI and BsmI polymorphisms might modulate the risk of cancer of breast, skin and prostate and possibly affect cancer risk at any site in Caucasians.