Association of Vitamin D Intake, VDR Levels, and Relevant Gene Polymorphisms in Early-Stage Thai Colorectal Cancer Patients Following Vitamin D3 Supplementation

Background: Recent studies have reported associations between vitamin D receptor (VDR) gene polymorphisms and colorectal cancer (CRC). However, the findings thus far are inconsistent. This study aims to clarify the association of vitamin D intake, VDR levels, and relevant polymorphisms in early stages of CRC in Thai patients following vitamin D3 supplementation. Methods: Total RNA and genomic DNA were isolated from the buffy coats of CRC patients (n = 27). The levels of VDR, RXR, CYP27B1, and CYP24A1 were measured using quantitative real-time PCR. Associations of nine single-nucleotide polymorphisms (SNPs) of VDR, CYP27B1, CYP24A1 and serum vitamin D levels were investigated. Results: The expression levels of VDR, RXR and CYP27B1 were significantly elevated in the vitamin D3-treated group. However, no significant associations were observed between vitamin D intake and the specific VDR SNPs, including FokI, BsmI, ApaI, TaqI, and Tru9I. Furthermore, none of the SNPs or haplotypes within the VDR, CYP27B1 (rs10877012), or CYP24A1 (rs6013897, rs158552, rs17217119) were linked to colorectal cancer susceptibility. Conclusions: This finding demonstrated that vitamin D intake enhances the expression of VDR and related genes in early-stage CRC patients; these effects are independent of VDR, CYP27B1, and CYP24A1 genetic polymorphisms. This suggests that gene expression changes may be driven more by vitamin D status than by underlying genetic variation.