Relationship of HLA-G expression and its 14-bp insertion/deletion polymorphism with susceptibility to colorectal cancer
Human leukocyte antigen (HLA) G, a non-classical HLA class I (MHC class I) molecule, is characterized by a low degree of polymorphism, unlike classical MHC-I. The 14-base pair insertion/deletion (indel) polymorphism (rs16375) in exon 8 of the 3′ untranslated region has been reported to control HLA-G expression transcriptionally and post-transcriptionally. We evaluated a possible association between the 14-bp indel polymorphism of HLA-G and the level of this protein in serum [sHLA-G1] and in primary-tumor tissue in colorectal cancer (CRC) of a Saudi population. A total of 105 patients with CRC and 105 healthy controls were analyzed for the 14-bp indel polymorphism. sHLA-G1; histological presence of HLA-G was also investigated for association with CRC. Lower prevalence of the heterozygous genotype of the 14-bp indel polymorphism was observed among the patients with CRC, though the difference was not quite significant (P = 0.052). In addition, the sHLA-G1 pattern did not show a significant difference between the patients with CRC and the controls. However, the expression pattern of HLA-G in colorectal tissue showed a heterogeneous profile, marked by a lack of expression in colorectal adenocarcinoma and normal cells and focal expression of the protein in the transition zone.