Molecular Mechanism of Cancer Susceptibility Associated with Fok1 Single Nucleotide Polymorphism of VDR in Relation to Breast Cancer

Abstract

Breast cancer is the leading cause of death among women worldwide. It is a multi-factorial disease caused by<br />genetic and environmental factors. Vitamin D has been hypothesized to lower the risk of breast cancer via the nuclear<br />vitamin D receptor (VDR). Genetic variants of these vitamin D metabolizing genes may alter the bioavailability of<br />vitamin D, and hence modulate the risk of breast cancer. Materials and Methods: The distribution of Fok1 VDR gene<br />(rs2228570) polymorphism and its association with breast cancer was analysed in a case–control study based on 125<br />breast cancer patients and 125 healthy females from North Indian population, using PCR-RFLP. An In silico exploration<br />of the probable mechanism of increased risk of breast cancer was performed to investigate the role of single nucleotide<br />polymorphisms (SNPs) in cancer susceptibility. Results: The Fok1 ff genotype was significantly associated with an<br />increased risk of breast cancer (p=0.001; χ2=13.09; OR=16.909; %95 CI=2.20 - 130.11). In silico analysis indicated<br />that SNPs may lead to a loss in affinity of VDR to calcitriol, and may also cause the impairment of normal interaction<br />of liganded VDR with its heterodimeric partner, the retinoid X receptor (RXR), at protein level, thereby affecting target<br />gene transcription. Conclusion: Breast cancer risk and pathogenesis in females can be influenced by SNPs. SNPs in<br />VDR may cause alterations in the major molecular actions of VDR, namely ligand binding, heterodimerization and<br />transactivation. VDRE binding and co-activator recruitment by VDR appear to be functionally inseparable events that<br />affect vitamin D-elicited gene transcription. This indicates that breast cancer risk and pathogenesis in females may be<br />influenced by SNPs.