Vitamin D status and breast cancer risk.

BACKGROUND: Local synthesis of 1alpha,25(OH)D3 in breast tissue may contribute to maintenance of normal cell function and could be impaired with low circulating levels of the precursor 25hydroxyvitamin D. The aims of this study were to: i) assess the association between breast cancer risk and plasma 25OHD3 concentration and ii) define the significance of expression of the 25OHD activating enzyme CYP27b1 in non-malignant and malignant models of breast epithelial cells. MATERIALS AND METHODS: Breast cancer patients and control women were recruited and their 25OHD levels measured by enzyme-linked immunosorbent assay (ELISA). MRNA expression of CYP271b and the 1,25(OH)2D3 inactivating enzyme CYP24 were measured in breast cancer cell lines by RT-PCR and correlated with immunoblotting approaches to the translated proteins. RESULTS: For women with 25OHD < 50 nM the odds ratio for breast cancer compared with women with 25OHD > 50 nM was 3.54 (CI 1.89-6.61, p < 0.001). CYP271b and CYP24 were detected in non-malignant and malignant cell models. Protein levels of 24OHase but not 1alphaOHase were decreased at confluence in the cell lines. CONCLUSION: Impaired local generation of 1,25OHD3 may contribute to the development of breast cancer.

Plasma 25-hydroxy vitamin D concentrations, vitamin D receptor genotype and breast cancer risk in a UK Caucasian population.

Low levels of 25-hydroxy vitamin D (25(OH)D) and polymorphisms in the vitamin D receptor gene (VDR) have been found separately to increase risk of breast cancer. The aim of this study was to determine whether low 25(OH)D levels, alone and in combination with BsmI VDR genotype, increased breast cancer risk in a United Kingdom (UK) Caucasian population. Breast cancer patients (n=179) and control women (n=179) were recruited and 25(OH)D levels measured by enzyme-linked immunosorbent assay (ELISA). VDR genotype was determined by polymerase chain reaction (PCR) and restriction enzyme digest. Analysis showed that subjects with 25(OH)D levels <50 nM and the bb BsmI VDR genotype are 6.82 times more likely to have breast cancer than subjects with levels of 25(OH)D>50 nM and either the BB or Bb genotype (95% confidence interval (CI) 2.31-14.7, P<0.001). This study indicates that low levels of circulating 25(OH)D, both alone and in combination with BsmI VDR genotype, may increase risk of breast cancer in a UK Caucasian population.

Vitamin D receptor gene polymorphisms and breast cancer risk.

PURPOSE: The steroid hormone 1,25-dihydroxyvitamin D3 is thought to protect against breast cancer. The actions of 1,25-dihydroxyvitamin D3 are mediated via the vitamin D receptor (VDR), and a number of polymorphisms in the VDR gene have been identified. These result in distinct genotypes, some of which may alter susceptibility to breast cancer. We have investigated whether specific VDR gene polymorphisms are associated with breast cancer risk in a United Kingdom Caucasian population. EXPERIMENTAL DESIGN: In a retrospective case-control study, female breast cancer patients (n = 398) and control women (n = 427) were recruited, and three VDR polymorphisms were determined. RESULTS: The 3' VDR polymorphisms BsmI and variable-length poly(adenylate) sequence were both significantly associated with breast cancer risk; odds ratios (adjusted for age menopausal status and hormone replacement therapy usage) for bb genotype versus BB genotype = 1.92 (95% confidence interval, 1.20-3.10; P < 0.01) and for LL versus SS = 1.94 (95% confidence interval, 1.20-3.14; P < 0.01). A 5' VDR gene variant, FokI, was not associated with breast cancer risk when analyzed in isolation (P > 0.05). However, FokI did modulate the increased risk associated with the bb/LL genotype such that possession of one or more F alleles together with the bb/LL genotype augmented breast cancer risk. Furthermore, the highest proportion of bb and FFLL/FfLL genotypes occurred in women with metastatic breast cancer. CONCLUSIONS: VDR polymorphisms are associated with breast cancer risk and may be associated with disease progression. Additional investigations into how different genotypes may affect the functional mechanisms of the VDR will provide a better strategy for identifying women at risk of breast cancer and for developing improved treatments.

Approaches to evaluating the association of vitamin D receptor gene polymorphisms with breast cancer risk.

The steroid hormone 1,25 dihydroxyvitamin D3 is thought to protect against breast cancer. Its actions are mediated via the vitamin D receptor (VDR) and a number of polymorphisms in the VDR gene have been identified, some of which may alter susceptibility to breast cancer. This study has investigated whether specific VDR gene polymorphisms are associated with breast cancer risk in a UK Caucasian population. Female breast cancer patients (n = 313) and control women with a negative screening mammogram (n = 410) were recruited and their VDR polymorphisms were determined. The 3' VDR polymorphism BsmI was significantly associated with breast cancer risk; odds ratio bb vs. BB genotype = 1.79 (95% CI, 1.12-2.86; P = 0.0221). In addition, over 70% of seven commonly used breast cancer cell lines were found to have the at-risk genotype bb. The 5' FokI gene variant was not associated with breast cancer risk. Further investigations into how these different genotypes may affect the functional mechanisms of the VDR will provide a better strategy for identifying women at risk of breast cancer and for developing improved treatments.

Induction of apoptosis in breast cancer cells by apomine is mediated by caspase and p38 mitogen activated protein kinase activation.

The 1,1-bisphosphonate ester family member apomine (SR-45023A) is known to have anti-tumour activity in various cancer cell types. The aims of this study were to determine the effect of apomine on the growth of two breast cancer cell lines, MCF-7 and MDA-MB-231, to ascertain whether any growth inhibitory effects found were due to induction of apoptosis, and to investigate the mechanism of action of apomine. Apomine caused significant growth inhibition of both cell lines after 72h of treatment. Apomine-induced growth inhibition was associated with caspase and p38 MAPK activation and DNA fragmentation. Apomine had no effect on Ras localisation, nor did addition of mevalonate to treatment media prevent apomine-induced apoptosis. We conclude that apomine induces apoptosis in breast cancer cells, an effect that is independent of oestrogen receptor status and is not via inhibition of the mevalonate pathway. Our study suggests apomine is a potential anti-neoplastic drug in breast cancer treatment.