Vitamin D Receptor Gene Polymorphism and Serum Vitamin D Levels with the Risk of Colorectal Cancer: an Observational Case-Control Study

Abstract Purpose: Colorectal cancer (CRC) is the third leading cause of cancer death in the world, and its incidence is steadily rising. Understanding the role of modifiable risk factors in colorectal carcinogenesis is one of the primary prevention strategies. This research was conducted to evaluate the relationship between serum vitamin D levels, vitamin D receptor (VDR) gene polymorphisms, and CRC risk. Methods: Fifty-one CRC patients who were diagnosed within the last three months prior to the study and 51 individuals adjusted by age and sex with the study group were included as controls. Serum vitamin D levels and four different VDR gene polymorphisms (ApaI, BsmI, FokI, and TaqI) were analyzed. Logistic regression analysis was made for the serum vitamin D levels and VDR gene polymorphisms. Results: It was determined that serum vitamin D deficiency (≤20 ng/mL) increases the CRC risk approximately 5.5 times (OR: 5.452, 95%CI: 1.909-15.568). Also, BsmI, ApaI, TaqI and FokI polymorphisms were not significantly associated with CRC risk (p>0.05). Serum 25(OH)D levels were evaluated according to VDR polymorphism genotypes, it was found that CRC patients with heterozygous (Bb and Aa) genotypes of BsmI and ApaI polymorphisms had significantly lower serum 25(OH)D levels than controls with the same genotype (p<0.05). The distribution of haplotypes did not differ statistically between the groups (p>0.05). Conclusions: Developing strategies to achieve normal serum vitamin D levels are important to decrease CRC prevalence. To better understanding these associations, further studies with larger sample sizes and other vitamin D pathway genes are needed.