Vitamin D and estrogen receptor gene polymorphisms and the risk of colorectal cancer in Bulgaria

Background and aims Different epidemiological studies report the protective effect on colorectal cancer (CRC) exerted by vitamin D₃ intake, estrogen replacement therapy, and increase of the risk of microsatellite instability (MSI) in CRC by withdrawal of estrogens. The aim of our study was to search for association between CRC and polymorphisms in estrogen receptor-α (ER-α) and Vitamin D receptor (VDR) genes. Materials and methods We analyzed the PvuII and XbaI polymorphisms from the ER-α gene and the BsmI polymorphism of the VDR gene in 140 patients with CRC (subsequently divided according to their MSI status) and 94 controls. Results We have demonstrated that the presence of the PvuII pp genotype increased the risk of developing MSI(+) tumors about three times compared to MSI(−) tumors [odds ratio (OR)=3.09, 95% confidence interval (CI) 0.88–10.91]. The effect of the XbaI xx genotype was similar (OR=2.08, 95% CI 0.49–8.81). Our results for the VDR BsmI polymorphism showed an increased risk for CRC in bb carriers (OR=1.8, 95% CI 0.81–4.05). Conclusion We conclude that PvuII and XbaI polymorphisms in the ER-α gene were associated with the risk of developing MSI in CRC patients. The BsmI polymorphism in the VDR gene was linked to the risk of developing CRC.