Vitamin D and VDR gene polymorphism (FokI) in epithelial ovarian cancer in Indian population
© Mohapatra et al.; licensee BioMed Central Ltd. 2013
Received: 2 April 2013
Accepted: 22 May 2013
Published: 26 May 2013
Vitamin D deficiency and vitamin D receptor (VDR) gene polymorphism, FokI, is reported to increase the risk of many cancers. Role of vitamin D and its receptor polymorphisms in ovarian cancer has not been clearly defined.
To study the levels of serum vitamin D and occurrence of vitamin D receptor gene polymorphism (FokI) in cases of ovarian cancer.
Material and methods
FokI genotyping was done by PCR-RFLP technique and vitamin D levels were estimated by chemiluminescence immunoassay.
Serum vitamin D levels were significantly (p < 0.03) lower in ovarian cancer cases as compared to controls. The homozygous (TT) and heterozygous (CT) genotype predispose to the development of ovarian cancer in Indian population (OR: 2.37, 95% CI: 1.04-5.44) as compared to the homozygous (CC) genotype. Vitamin D deficiency and VDR gene polymorphism (FokI) act non-synergistically (p value < 0.4).
Low blood levels of vitamin D and VDR receptor polymorphism (FokI) might be a risk factor for the development of ovarian cancer. Other novel ligands of vitamin D receptor might be responsible for the non-synergistic effect.
Ovarian cancer is the 6th most common cancer in women with estimated lifetime risk of 1 in 70 women . Epithelial ovarian cancer is the most common histological type of ovarian cancer. More than seventy percent of these patients present in the advanced stage of this disease, and have a cure rate of less than forty percent . The high mortality in these cases is due to lack of highly sensitive and specific screening methods.
Vitamin D is a fat soluble secosteroid which is involved in a wide variety of biological processes like bone metabolism, modulation of immune response, cell proliferation and cell differentiation. There exists an inverse relationship between vitamin D levels in blood and incidence of many cancers [3, 4]. The studies conducted by Arslan et al. and Tworoger et al. couldn’t establish any direct relationship between vitamin D deficiency and risk of ovarian cancer [5, 6]. But Tworoger et al. reported that vitamin D deficiency is associated with significant risk of ovarian cancer in overweight and obese women . Activity of vitamin D is mediated by vitamin D receptor (VDR). VDR gene polymorphism, FokI, (rs10735810/rs2228570) is reported to be in linkage disequilibrium with other VDR polymorphisms. A change in the sequence from C to T in the start codon translation site leads to generation of a polymorphic variant (TT) which is three amino acids longer and has decreased transactivation capacity as compared to the short CC allele . Several population based studies indicated that VDR gene polymorphisms are associated with human cancers [8, 9]. A few studies tried to establish a relationship between vitamin D receptor gene polymorphism (FokI) and ovarian cancer. The odds ratio in these studies were observed to vary from 1.09 to 2.5 indicating that CT and TT genotypes of VDR gene polymorphism (FokI) are at increased risk of ovarian cancer[10–13]. However there is hardly any data in this regard in the Indian population. Hence the present study was designed (a) to evaluate the levels of serum vitamin D in epithelial ovarian cancer patients, (b) to evaluate the association of Vitamin D receptor (VDR) gene polymorphism (FokI) with the risk of epithelial ovarian cancer and (c) to explore if the relationship between vitamin D levels and vitamin D receptor polymorphism FokI is additive in their action.
Material and methods
A case control study was designed to recruit fifty subjects in each group and conducted in the department of Biochemistry and department of Obstetrics and Gynecology, Maulana Azad Medical College, New Delhi. Written informed consent was taken from the cases and controls. Blood sample (5 ml) was collected from fifty newly diagnosed ovarian cancer patients who had histopathologically confirmed epithelial ovarian cancer. The study group was subjected to a structured questionnaire (regarding demographic, medical, lifestyle and reproductive information). Fifty controls were matched with respect to age, menopausal status and month of blood draw. The study was approved by the institutional ethics committee of Maulana Azad Medical College, New Delhi.
Serum vitamin D estimation
The serum vitamin D was measured by electrochemiluminescence immunoassay method using Elecsys Total Vitamin D (25-OH) kit (Roche diagnostics, Mannheim, Germany) adapted to ELECSYS 2010 (Roche diagnostics, Mannheim, Germany).
Statistical analysis was done with SPSS version 17.0 (SPSS, Inc., Chicago IL). Independent T test (for parametric data) and Mann Whitney U test (for nonparametric data) were used to compare the data. The relationship between vitamin D and ovarian cancer was determined using logistic regression. The associations between CT and TT genotypes and risk of ovarian cancer were estimated by computing the odds ratios (ORs) and their 95% confidence intervals (CIs). Synergy factor was calculated to measure the interaction between vitamin D deficiency and VDR polymorphism (FokI) . Statistical difference was considered significant for p values <0.05.
General characteristics of study population
Characteristics of epithelial ovarian cancer cases and controls
Ovarian cases (n = 50)
Controls (n = 50)
Age in yr
47.9 ± 13.35
47.2 ± 12.4
Subjects with positive family history of breast or ovarian cancer
History of use of oral contraceptives
Serum vitamin D levels
Odds ratio (OR) and 95% CI for ovarian cancer according to tertile levels of baseline vitamin D levels
Median (Range) of serum vitamin D levels in ng/ml
Ovarian cancer patients
OR (95% CI) Unadjusted
Top tertile 36 (27–47)
Bottom tertile 11.9 (5–16.2)
Median (range) of serum vitamin D (in ng/ml) in reproductive and post-menopausal age group in ovarian cancer patients and controls
Ovarian cancer patients
Reproductive age group
18.3 (7.2-61.8)(n = 19)
21.4 (7.3-40)(n = 20)
20.6 (6.93-43)(n = 30)
27.8 (7.7-47)(n = 31)
Comparison of vitamin D levels in different clinical stages and histological grading in ovarian cancer
Median (Range) of vitamin D in ng/ml
Stage I and II (n = 7)
Stage III (n = 40)
Stage IV (n = 3)
Well-differentiated (n = 6)
Moderately differentiated (n = 29)
Poorly-differentiated (n = 15)
Distribution of FF and Ff/ff genotypes in cases and healthy controls
Odds ratio (95% CI)
CT + TT (Ff + ff)
By unconditional logistic regression analysis, it was found that in comparison to the CC genotype, the CT and TT genotype (combined) were at significantly higher risk of ovarian cancer (OR = 2.37, 95% CI 1.04-5.44, p < 0.05).
Synergy factor (SF) in ovarian cancer between serum vitamin D and VDR ( Fok1) gene polymorphism
VDR gene (Fok1)
Vitamin D deficient
Ovarian cancer cases
SF (p value)
Vitamin D was known to be involved in bone metabolism but its role in other diseases like cancer, autoimmune diseases and diabetes mellitus is being studied extensively only in recent times. Ovarian cancer, on the other hand is a disease whose etiology is attributed to incessant ovulation and hormonal imbalance. Potential role of vitamin D in cancer prevention has been widely described [16–18]. There exist numerous studies which show inverse relationship of cancers of different organs with sun exposure including ovarian cancer [19–21]. However only a few studies have evaluated the role of serum vitamin D levels in ovarian cancer, and most are on Caucasian population [5, 6]. To our knowledge this is the first study showing a clear relationship between vitamin D deficiency, VDR functional polymorphism (FokI) and risk of ovarian cancer in Indian population.
It may seem surprising to see the prevalence of vitamin D deficiency in a tropical country like India. The reason behind this could be the lifestyle of people where most of the women stay indoors. The poor intake of dairy products due to social factor and dietary habits may also contribute to this. A few studies conducted on general prevalence of vitamin D deficiency in India show alarming trends [22, 23]. In our study, the participants in the highest tertile had a significant lower risk of ovarian cancer than those in the lowest tertile. On subset analysis, the mean vitamin D level of ovarian cancer (21 ± 9.1 ng/ml) was significantly lower than that of controls (26.5 ± 8.5 ng/ml) in the post-menopausal group. The reason could be that in post-menopausal state there is an increased need of vitamin D due to decreased expression of VDR caused by decrease in estrogen levels .
Summary of other studies on Fok I in ovarian cancer
Odds ratio FFvsFf/ff
Lurie et al. 2007 
Clendenen et al. 2008 
U.S + Sweden
Tworoger et al. 2009 
Lurie et al. 2010 
The increased risk of ovarian cancer in combined vitamin D deficiency and vitamin D receptor polymorphism is expected to be due to modulation of same target molecules. But we observed that low serum vitamin D levels along with homozygous TT allele didn’t lead to synergistic increase in the risk of epithelial ovarian cancer (synergy factor:2; p value < 0.4). There are other novel ligands of vitamin D receptor and co-modulators influencing vitamin D signaling mechanism [29–31]. The non-synergistic effect indicates that these novel ligands of vitamin D receptor and co-modulators might also play a role in determining the risk of ovarian cancer which is worth exploring.
It is suggested that low vitamin D levels might be a risk factor for ovarian cancer. Additionally, VDR gene (FokI) polymorphism may be a genetic modifier for ovarian cancer risk in Indian population. The homozygous FokI (TT) and heterozygous (CT) polymorphism and vitamin D levels have independent effect on cancer development and are not synergistic in their actions. However, independent large population-based prospective studies are needed to validate our findings and to facilitate rigorous analyses of subgroups. Thus our study provides evidence that the protective effect of vitamin D supplementation against ovarian cancer (especially in postmenopausal women) is worth investigating in Indian population.
We would like to thank Dr Tejinder Singh for assisting in the histopathological studies in this work.
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