Association of the vitamin D receptor genotype with bone metastases in breast cancer patients

This study was designed in order to evaluate specific vitamin D receptor (VDR) genotypes as indicators of the likelihood of developing osseous metastases in breast cancer patients. Therefore, we determined polymorphisms of the VDR gene in a study group comprising 183 breast cancer patients. Specific fragments spanning over intron 8 and exon 9 of the VDR gene were amplified by polymerase chain reaction. The fragments were then incubated with each of the specific endonucleases APAI, BSMI or TAQI, respectively. The VDR gene polymorphisms were detected by the presence or absence of the particular restriction site using agarose gel electrophoresis. Statistical analyses revealed a significant correlation between both the VDR gene polymorphisms indicated as AA (absence of the APAI restriction site in both alleles) or TT (absence of the TAQI restriction site in both alleles), respectively, and the occurrence of bone metastases. Patients with the AA genotype have a 1.7-fold increased risk of developing bone metastases, whereas patients with the TT genotype have a 0.5-fold risk. Neither other genotypes nor allelic combinations displayed any further correlation with the clinical stage. The data suggest that the AA genotype of the VDR gene might be useful to identify breast cancer patients with a high probability of forming occult bone metastases who are considered to benefit from an adjuvant bone-protective therapy.