Polymorphisms of Fractalkine receptor CX3CR1 and plasma levels of its ligand CX3CL1 in colorectal cancer patients

Abstract

The chemokine Fractalkine/CX3CL1, which is expressed by epithelial cells within normal colorectal mucosa and in colorectal cancer (CRC), is thought to have a crucial role in colorectal mucosal immunity by recruiting leucocytes via the receptor CX3CR1. The purpose of this study was to investigate two single-nucleotide polymorphisms of the Fractalkine receptor/CX3CR1 gene, V249I and T280M, in CRC to find out whether they occur more often in patients with CRC than in non-CRC individuals. In the search for tumour markers, we also intended to determine whether plasma levels of Fractalkine were correlated with parameters such as Dukes' stage, tumour localisation, gender and age in CRC patients. Genomic deoxyribonucleic acid from 223 CRC patients and 229 controls was amplified by polymerase chain reaction, and the polymorphisms were detected by the restriction fragment length polymorphism analysis. Fractalkine/CX3CL1 was analysed in plasma from 62 CRC patients and 78 controls using enzyme-linked immunosorbent assay. The variant V249I was significantly different in genotype and allelic distribution between CRC patients and control subjects, P = 0.028 and P = 0.048, respectively. We also found that individuals with the I249 allele in homozygote state were less frequent in the CRC group (3.1%) compared with controls (9.2%; P = 0.008). No significant difference was observed regarding Fractalkine/CX3CL1 levels in plasma between patients and the control group. Our results suggest that the lack of the allele I249 of the CX3CR1 gene may play a partial or minor role in CRC and that plasma Fractalkine/CX3CL1 does not seem to be a useful tumour marker that reflects the disease outcome of CRC.