Serum 25-hydroxyvitamin D and the risk of ovarian cancer

Insight into vitamin D3 action within the ovary-Basic and clinical aspects

Vitamin D3 is a fat-soluble secosteroid predominantly synthesized in the skin or delivered with a diet. Nevertheless, recently it is considered more as a hormone than a vitamin due to its pleiotropic function within the organism ensured by widely distributed vitamin D receptors and metabolic enzymes. Besides the main role in calcium and phosphorus homeostasis, vitamin D3 was shown to regulate many cellular and metabolic processes in normal and cancerous tissues within the immune system, the cardiovascular system, the respiratory system and the endocrine system. The ovary is an important extraskeletal tissue of vitamin D3 action and local metabolism, indicating its role in the regulation of ovarian functions upon physiological and pathological conditions. This chapter reviews firstly the updated information about vitamin D3 metabolism and triggered intracellular pathways. Furthermore, the basic information about ovarian physiology and several aspects of vitamin D3 effects within the ovary are presented. Finally, the special attention is paid into possible mechanism of vitamin D3 action within ovarian pathologies such as premature ovarian failure, polycystic ovary syndrome, and ovarian cancer, considering its clinical application as alternative therapy.

Serum vitamin D deficiency and risk of epithelial ovarian cancer in Lagos, Nigeria

The studies that have evaluated the association between vitamin D and risk of ovarian cancer have reported inconsistent findings. Many of these studies were carried out in regions with relatively low sunshine all year round unlike in Africa. This study was aimed to determine the relationship between vitamin D deficiency and epithelial ovarian cancer (EOC) amongst women in Lagos, Nigeria. We conducted a case–control study involving women with histologically confirmed EOC (case group) and an equal number of healthy women without cancer (control group) treated at the gynaecological oncology units of two public tertiary hospitals in Lagos, Nigeria, between 1 August, 2016 and 31 May, 2017. Relevant information was obtained from the participants using a structured interviewer-administered questionnaire, and then, venous blood samples were collected and analysed for serum 25-hydroxyvitamin D levels using the CALBIOTECH® 25(OH) vitamin D ELISA kit. The descriptive statistics were conducted for all relevant data, and the multivariable analysis using binary logistic regression model was performed to examine the association between vitamin D deficiency and EOC after adjusting for all possible confounders. The mean age of the participants was 50.6 ± 11.1 years. There was no statistically significant association between serum vitamin D deficiency and EOC (p = 0.09). However, 10 mmol/L change in circulating vitamin D levels was associated with EOC amongst the study participants (adjusted odds ratio 0.96; 95% confidence interval 0.93–0.99; p = 0.04), but following adjustment for potential confounders in a multivariable analysis, there was no statistically significant relationship observed with EOC (adjusted odds ratio 0.99; 95% confidence interval 0.97–1.00; p = 0.06). In addition, there was no evidence of an interaction effect between these confounders and change in circulating 25(OH)D levels in relation to the risk of EOC. The study revealed no statistically significant association between the circulating levels of vitamin D and the risk of EOC. A better assessment of sun exposure in the future as well as better dietary compositional data may help to clarify whether the association between vitamin D and EOC actually exists. Therefore, the future large prospective longitudinal studies are recommended to further examine this relationship and then evaluate the possible need for vitamin D supplementation in women with an increased risk of EOC in Nigeria.

Vitamin D Exposure and Ovarian Cancer Risk and Prognosis

Given the poor prognosis of ovarian cancer and limited population-level strategies for early detection and long-term treatment success, knowledge of modifiable risk factors for prevention and improved prognosis is important. Vitamin D has received wide scientific interest in cancer research as having the potential to be one such factor. We carried out a systematic narrative review of the literature on vitamin D and ovarian cancer risk and survival. We included 17 case-control and cohort studies on ovarian cancer incidence. Five analyses were of sun exposure, among which three reported an inverse association. Of 11 analyses of dietary vitamin D, two reported an inverse association. Among five studies of 25(OH)D levels, an inverse association was reported in two. Across all studies the findings were inconsistent, but some recent studies have suggested that vitamin D exposure at earlier ages may be important. Only three studies examining vitamin D exposure in relation to survival among ovarian cancer survivors were identified and the findings were inconsistent. The evidence to date supports a null influence of vitamin D on both ovarian cancer risk and survival. Future research should ensure that exposure assessment captures vitamin D exposure from all sources and for the etiologically or prognostically pertinent period.

Vitamin D and VDR in Gynecological Cancers-A Systematic Review

In recent years, a vast amount of studies have centered on the role of vitamin D in the pathogenesis of certain types of cancers such as breast, colorectal and lung cancer. Increasing evidence suggests that vitamin D and its receptor play a crucial role in the development of gynecological cancers. In this review, we systematically analyzed the effect of vitamin D and the vitamin D receptor on endometrial, ovarian, cervical, vulvar and vaginal cancer. Our literature research shows that vitamin D levels and vitamin-D-related pathways affect the risk of gynecological cancers. Numerous ecological studies give evidence on the inverse relationship between UVB exposure and gynecological cancer risk. However, epidemiologic research is still inconclusive for endometrial and ovarian cancer and insufficient for rarer types of gynecological cancers. The vitamin D receptor (VDR) is upregulated in all gynecological cancers, indicating its influence on cancer etiology. The VDR polymorphism FokI (rs2228570) seems to increase the risk of ovarian cancer. Other nuclear receptors, such as the RXR, also influence gynecological cancers. Although there is limited knowledge on the role of the VDR/RXR on the survival of endometrial, cervical, vulvar or vaginal cancer patients, some studies showed that both receptors influence survival. Therefore, we suggest that further studies should focus on the vitamin D- and its hetero dimer receptor RXR in gynecological cancers.

Association of vitamin D levels and risk of ovarian cancer: a Mendelian randomization study

BACKGROUND

In vitro and observational epidemiological studies suggest that vitamin D may play a role in cancer prevention. However, the relationship between vitamin D and ovarian cancer is uncertain, with observational studies generating conflicting findings. A potential limitation of observational studies is inadequate control of confounding. To overcome this problem, we used Mendelian randomization (MR) to evaluate the association between single nucleotide polymorphisms (SNPs) associated with circulating 25-hydroxyvitamin D [25(OH)D] concentration and risk of ovarian cancer.

METHODS

We employed SNPs with well-established associations with 25(OH)D concentration as instrumental variables for MR: rs7944926 (DHCR7), rs12794714 (CYP2R1) and rs2282679 (GC). We included 31 719 women of European ancestry (10 065 cases, 21 654 controls) from the Ovarian Cancer Association Consortium, who were genotyped using customized Illumina Infinium iSelect (iCOGS) arrays. A two-sample (summary data) MR approach was used and analyses were performed separately for all ovarian cancer (10 065 cases) and for high-grade serous ovarian cancer (4121 cases).

RESULTS

The odds ratio for epithelial ovarian cancer risk (10 065 cases) estimated by combining the individual SNP associations using inverse variance weighting was 1.27 (95% confidence interval: 1.06 to 1.51) per 20 nmol/L decrease in 25(OH)D concentration. The estimated odds ratio for high-grade serous epithelial ovarian cancer (4121 cases) was 1.54 (1.19, 2.01).

CONCLUSIONS

Genetically lowered 25-hydroxyvitamin D concentrations were associated with higher ovarian cancer susceptibility in Europeans. These findings suggest that increasing plasma vitamin D levels may reduce risk of ovarian cancer.

Vitamin D postpones the progression of epithelial ovarian cancer induced by 7, 12-dimethylbenz [a] anthracene both in vitro and in vivo

Purpose

Ovarian cancer is the most lethal malignancy of the female reproductive system, and the prevention and treatment of ovarian carcinoma are still far from optimal. Epidemiological studies reported that ovarian cancer risk was inversely associated with low level of 25-hydroxy vitamin D [25(OH)]. Therefore, this study focuses on exploring the chemoprevention of vitamin D on epithelial ovarian cancer induced by 7, 12-dimethylbenz [a] anthracene (DMBA).

Methods

The mouse ovarian surface epithelial cells were isolated from estrus mice by mild trypsinization and maintained in completed culture medium by repeated passaging. The malignant transformation of mouse ovarian surface epithelial cells was induced by DMBA in vitro. DMBA was directly injected into the bursa of mouse ovary to produce optimized in vivo ovarian cancer model.

Results

The results indicate that 1α,25 dihydroxyvitamin D3 may delay malignant transformation of mouse ovarian surface epithelial cells induced by DMBA and significantly decreased the colony formation rate from 18.4% to 3.2% (P<0.05). There was a negative correlation between incidence of DMBA-induced tumor and 25-hydroxy vitamin D level (R²=0.978, P<0.05). Vitamin D3 can delay the progression of ovarian cancer induced by DMBA, and the administration of vitamin D3 during the whole process worked more effectively than the administration only during tumor initiation or promotion. Moreover, we found the vitamin D3 increased the expression of E-cadherin and vitamin D receptor while it decreased the expression of β-catenin.

Conclusion

We succeeded in establishment of epithelial ovarian cancer models both in vitro and in vivo. The DMBA-implanted model in mice yields high incidence and specificity of epithelial derived tumors. We also found that vitamin D delays the progression of ovarian cancer. However, spontaneous epithelial ovarian carcinoma models are still to be explored for testing the preventive effects of vitamin D on epithelial ovarian cancer.

Evidence of differential effects of vitamin d receptor variants on epithelial ovarian cancer risk by predicted vitamin d status

INTRODUCTION

Experimental studies suggest vitamin D inhibits ovarian carcinogenesis. Yet, epidemiologic studies of ovarian cancer risk and lifestyle correlates of vitamin D status, plasma 25-hydroxyvitamin D [25(OH)D], or vitamin D receptor (VDR) variants have been inconsistent.

OBJECTIVE

To evaluate VDR genetic associations by high vs. low predicted 25(OH)D, scores derived from known determinants of plasma 25(OH)D. To assess ovarian cancer associations with variants identified in genome-wide association studies (GWAS) of plasma 25(OH)D.

METHODS

We genotyped up to seven VDR and eight 25(OH)D GWAS variants in the Nurses' Health Studies (562 cases, 1,553 controls) and New England Case-Control study (1,821 cases, 1,870 controls). We estimated haplotype scores using expectation-maximization-based algorithms. We used unconditional logistic regression to calculate odds ratios (ORs) and 95% confidence intervals (CI). We combined study results using DerSimonian and Laird meta-analysis.

RESULTS

Ovarian cancer risk increased per A allele of rs7975232 (VDR; OR = 1.12, 95% CI = 1.01-1.25) among all women. When stratified by predicted 25(OH)D, ovarian cancer was associated with rs731236 (VDR; per C allele OR = 1.31) and rs7975232 (OR = 1.38) among women with high predicted 25(OH)D, but not among women with low levels (P ≤ 0.009). We also observed heterogeneity by predicted 25(OH)D for the ovarian cancer association with VDR 3' end haplotypes (P = 0.009). Of 25(OH)D-associated GWAS loci, rs7041 was associated with reduced ovarian cancer risk (per T allele OR = 0.92, 95% CI = 0.85-0.99), which did not differ by predicted 25(OH)D status.

CONCLUSION

Our study suggests an influence of VDR 3' end variants on ovarian cancer risk may be observed in women with high predicted 25(OH)D, which remained even after taking multiple comparisons into consideration. Future studies are needed to confirm our results and explore further the relation between vitamin D exposure, genetic variants, and ovarian cancer risk.

Surrogates of long-term vitamin d exposure and ovarian cancer risk in two prospective cohort studies

Experimental evidence and ecologic studies suggest a protective role of vitamin D in ovarian carcinogenesis. However, epidemiologic studies using individual level data have been inconsistent. We evaluated ultraviolet (UV)-B radiation, vitamin D intake, and predicted plasma 25-hydroxyvitamin D [25(OH)D] levels as long-term surrogates of vitamin D exposure within the Nurses’ Health Study (NHS) and NHSII. We estimated incidence rate ratios (RRs) and 95% confidence intervals (CIs) for risk of overall ovarian cancer and by histologic subtype using Cox proportional hazards models. Between 1976 and 2010 in NHS and 1989 and 2011 in NHSII, we identified a total of 1,225 incident epithelial ovarian cancer cases (NHS: 970, NHSII: 255) over 4,628,648 person-years of follow-up. Cumulative average UV-B exposure was not associated with ovarian cancer risk in NHS (P_trend = 0.08), but was associated with reduced risk in NHSII (highest vs. lowest category RR = 0.67; 95% CI: 0.50, 0.89; P_trend < 0.01). When stratified by histologic subtype, UV-B flux was positively associated with risk of serous tumors in NHS (P_trend < 0.01), but inversely associated in NHSII (P_trend = 0.01). Adjusted for confounders, ovarian cancer risk was not associated with vitamin D intake from food or supplements or with predicted 25(OH)D levels. Our study does not strongly support a protective role for vitamin D in ovarian cancer risk.

25(OH)D3 in patients with ovarian cancer and its correlation with survival

OBJECTIVES

The aim of this study was to examine vitamin 25(OH)D3 concentration in ovarian cancer patients in relation to a pathological subtype of the tumor, FIGO stage, grading, menopause status and overall 5-year survival.

DESIGN AND METHODS

72 epithelial ovarian cancer patients aged 37-79, who undergone optimal cytoreductive surgery were enrolled to the study group. Serum 25(OH)D3 concentration was measured using an electrochemiluminescence immunoassay before surgery. Serum concentration of 25(OH)D3 was also measured in a group of 65 healthy non-obese women aged 35-65 years.

RESULTS

In patients with ovarian cancer serum concentration of 25(OH)D3 was lower than in the reference group (12.5±7.75 ng/mL vs 22.4±6.5 ng/mL). No significant correlation was found between serum 25(OH)D3 concentration and histological subtype, grading, FIGO stage and menopausal status. The study group was divided into two subgroups and the survival curves were analyzed. Overall 5-year survival rate was significantly higher in the subgroup of patients with 25(OH)D3 concentration over 10 ng/mL compared to women with concentration below 10 ng/mL.

CONCLUSIONS

Low 25(OH) D3 concentration associated with lower overall survival rate might suggest for the important role of severe deficiency in more aggressive course of ovarian cancer. Testing for 25(OH)D in the standard procedure could help to find ovarian cancer patients with worse prognosis, who would benefit of special attention and supplementation.

Maternal vitamin D during pregnancy and its relation to immune-mediated diseases in the offspring

Vitamin D deficiency during pregnancy is fairly common in many parts of the world. However, currently there is no consensus on the optimal vitamin D intake during pregnancy. Vitamin D is known to be of great importance for the homeostatic functions within the immune system. Maternal vitamin D status during pregnancy may therefore affect the developing immune system of the fetus, thus contributing to the later development of immune-mediated diseases. This chapter introduces the basics of vitamin D during pregnancy and discusses the role of maternal vitamin D intake in the development of asthma, allergic diseases, autoimmune diseases, cancer, and infections in the offspring. So far, the strongest observational evidence underlines the potential of maternal vitamin D intake during pregnancy to influence the likelihood of asthma and allergic outcomes in the offspring. Somewhat conflicting findings imply that there might be critical time windows of exposure to adequate vitamin D levels during pregnancy. More research is needed in order to fully understand the contribution of maternal vitamin D status during pregnancy to the progress of immune-mediated diseases.

Prospective study of UV exposure and cancer incidence among Swedish women

BACKGROUND

Except for skin melanoma and nonmelanoma skin cancer, little evidence from prospective studies is available on the association between UV exposure and cancer risk.

METHODS

We followed prospectively 49,261 women aged 30 to 49 years at enrollment in 1991 to 1992 for 15 years. Cancer incidence was analyzed by fitting Cox models, and estimating hazard ratios (HR) and 95% confidence intervals (CI).

RESULTS

2,303 incident cases of cancer were diagnosed (breast: 1,053, ovary: 126, lung: 116, colon-rectum: 133, and brain: 116). No associations were found between any cumulative measure of UV exposure at ages 10 to 39 years and overall cancer risk. However, spending ≥1 week/year between ages 10 and 29 years on sunbathing vacations led to an inverse association with overall cancer risk (HR: 0.70, 95% CI: 0.53-0.93) and breast cancer risk (HR: 0.56, 95% CI: 0.36-0.89) when compared with women who never went on such vacations. Solarium use was inversely associated with breast cancer risk, whereas ≥2 sunburns/year was inversely associated with lung cancer risk. No other associations were found between sun exposure or solarium use at ages 10 to 39 years and cancer risk.

CONCLUSION

We found no evidence of an association between any cumulative measure of UV exposure at ages 10 to 39 years and overall cancer risk. UV exposure earlier in life was related to reduced overall and breast cancer risk.

IMPACT

Further research is needed to define the amount of solar or artificial UV exposure that may, or may not, be beneficial for cancer prevention.

Meta-analysis: Circulating vitamin D and ovarian cancer risk

OBJECTIVE

To review and summarize evidence from longitudinal studies on the association between circulating 25 hydroxyvitamin D (25(OH)D) and the risk of ovarian cancer (OC).

METHODS

Relevant prospective cohort studies and nested case-control studies were identified by systematically searching Ovid Medline, EMBASE, and ISI Web of Knowledge databases and by cross-referencing. The following data were extracted in a standardized manner from eligible studies: first author, publication year, country, study design, characteristics of the study population, duration of follow-up, OC incidence according to circulating vitamin D status and the respective relative risks, and covariates adjusted for in the analysis. Due to the heterogeneity of studies in categorizing circulating vitamin D levels, all results were recalculated for an increase of circulating 25(OH)D by 20ng/ml. Summary relative risks (RRs) were calculated using meta-analysis methods.

RESULTS

Overall, ten individual-level studies were included that reported on the association between circulating vitamin D levels and OC incidence. Meta-analysis of studies on OC incidence resulted in a summary RR (95% confidence interval, CI) of 0.83 (0.63-1.08) for an increase of 25(OH)D by 20ng/ml (P=0.160). No indication for heterogeneity and publication bias was found.

CONCLUSIONS

A tentative inverse association of circulating 25(OH)D with OC incidence was found, which did not reach statistical significance but which requires clarification by additional studies due to potentially high clinical and public health impact.

Obesity and increased risk of cancer: does decrease of serum 25-hydroxyvitamin D level with increasing body mass index explain some of the association?

Low levels of vitamin D and excess body weight are both factors associated with increased risk of cancer. The increased risk seems to be proportional to the increase in BMI, and to decrease in serum 25-hydroxyvitamin D (25(OH)D) level. Our earlier investigations suggest that serum 25(OH)D levels decrease with increasing BMI. Although the connection between cancer risk, BMI and vitamin D status might be arbitrary, it has not been discussed in the literature so far. In this study, we analyze data published in current meta-analysis, prospective studies, and systematic reviews on cancer-specific risk attributed to high BMI and low vitamin D status. The contribution of low 25(OH)D levels associated with high BMI to increased cancer risk was calculated for 13 vitamin-D-sensitive cancers with a focus on colorectal and breast cancer as the most frequently studied vitamin-D-sensitive cancer types. Our study suggests that a low vitamin D status may explain at least 20% of the cancer risk attributable to high BMI. The contribution of low 25(OH)D to the increased cancer risk with increasing BMI may be different for different cancer types. Thus, we find 40% for breast cancer, and 26 and 75% for colorectal cancer in men and women, respectively.

Peri- and post-menopausal incidental adnexal masses and the risk of sporadic ovarian malignancy: new insights and clinical management

Adnexal masses are common among peri- and post-menopausal women. Although ovarian cancer is a significant cause of mortality in menopausal women, large population-based studies demonstrate that the majority of adnexal masses are benign. Despite this, the appearance of an adnexal mass is a concern for the patient and an insight exercise for physicians. In most cases, an adnexal enlargement is an incidental finding, generally corresponding to a benign cyst and easily diagnosed by conventional ultrasound. Exceptionally an ovarian tumour may be malignant and should be treated as early as possible. When conventional ultrasound renders complex morphology other diagnostic tools must be used such as: colour Doppler and functional tumour vessel properties, serum CA 125 levels, nuclear magnetic resonance imaging and in some cases laparoscopy. Several new tumour markers are being studied for clinical application, although there are presently no clear recommendations. Adnexal masses with benign morphological and functional properties must be periodically monitored as an alternative to surgery since malignant transformation is exceptional.

Circulating 25-hydroxyvitamin D and risk of epithelial ovarian cancer: Cohort Consortium Vitamin D Pooling Project of Rarer Cancers

A role for vitamin D in ovarian cancer etiology is supported by ecologic studies of sunlight exposure, experimental mechanism studies, and some studies of dietary vitamin D intake and genetic polymorphisms in the vitamin D receptor. However, few studies have examined the association of circulating 25-hydroxyvitamin D (25(OH)D), an integrated measure of vitamin D status, with ovarian cancer risk. A nested case-control study was conducted among 7 prospective studies to evaluate the circulating 25(OH)D concentration in relation to epithelial ovarian cancer risk. Logistic regression models were used to estimate odds ratios and 95% confidence intervals among 516 cases and 770 matched controls. Compared with 25(OH)D concentrations of 50-<75 nmol/L, no statistically significant associations were observed for <37.5 (odds ratio (OR) = 1.21, 95% confidence interval (CI): 0.87, 1.70), 37.5-<50 (OR = 1.03, 95% CI: 0.75, 1.41), or > or =75 (OR = 1.11, 95% CI: 0.79, 1.55) nmol/L. Analyses stratified by tumor subtype, age, body mass index, and other variables were generally null but suggested an inverse association between 25(OH)D and ovarian cancer risk among women with a body mass index of > or =25 kg/m(2) (P(interaction) < 0.01). In conclusion, this large pooled analysis did not support an overall association between circulating 25(OH)D and ovarian cancer risk, except possibly among overweight women.

Independent and joint effects of serum 25-hydroxyvitamin D and calcium on ovarian cancer risk: a prospective nested case-control study

INTRODUCTION

Ovarian cancer has very few known modifiable risk factors but dietary studies suggest a role for vitamin D and calcium in the prevention of ovarian cancer. Thus, we investigated the association between pre-diagnostic serum calcium and 25-hydroxyvitamin D (25-OHD) on the risk of later development of ovarian cancer.

METHODS

We conducted a population-based nested case-control study within the Finnish Maternity Cohort (FMC). The cohort subset comprised 172 ovarian cancer cases with 172 matched controls (age ± 1 year, parity and season of blood donation ± 2 weeks).

RESULTS

We observed a significant inverse association between calcium and ovarian cancer risk. Relative risk (estimated as odds ratio, OR) comparing the highest quartile to the lowest quartile was significantly decreased; 0.41 [95% confidence interval (CI) 0.19-0.85, P-trend 0.004]. Even though a comparable association between 25-OHD and ovarian cancer did not reach statistical significance (OR 0.57, 95% CI 0.26-1.24, P-trend 0.07), having sufficient (> 75 nmol/L) serum 25-OHD levels compared to insufficient serum 25-OHD was associated with a significantly decreased risk of ovarian cancer (OR 0.32; 95% CI 0.12-0.91, p-value 0.03). No synergistic protective interaction between high levels of calcium and 25-OHD against ovarian cancer was observed, the joint effect being just multiplicative.

CONCLUSION

Calcium and vitamin D act independently to reduce the risk of ovarian cancer. The decreased risk of ovarian cancer associated with pre-diagnostic serum calcium and vitamin D needs to be evaluated further for possible new insights into ovarian cancer prevention.

Relation between prediagnostic serum 25-hydroxyvitamin D level and incidence of breast, colorectal, and other cancers

The evidence is increasing that higher serum 25-hydroxyvitamin D [25(OH)D] levels reduce the risk of many types of cancer. Ecological and observational studies yield the strongest evidence, with support from studies of mechanisms. A key question is identifying the relation between serum 25(OH)D level and cancer incidence. Meta-analyses of such studies is a reasonable approach to determine the serum 25(OH)D level-cancer incidence relation. This paper reports new meta-analyses for breast and colorectal cancers. Currently, the journal literature offers seven prospective breast cancer and ten prospective colorectal cancer studies that can be used. The data for these studies graphed and compared. Data from some of the studies were multiplied by factors to bring all the studies into reasonable agreement with a tentative dose-response relation. The data were fit with a variety of functions; the best fits were nonlinear functions that tended to asymptotically reach a lower odds ratio at higher serum 25(OH)D levels. These analyses estimated that the 50% reduction in incidence occurs for a value of 78 nmol/L compared with the value at 24 nmol/L for breast cancer, and a value of 60 nmol/L compared with the value at 15 nmol/L for colorectal cancer. Although these results are reasonable, some concern exists that a single serum 25(OH)D level, measured years prior to diagnosis of cancer, does not adequately represent the serum levels for the entire period before diagnosis. Future prospective studies should include more serum 25(OH)D level measurements during the study course.