The relationship between Lewis/Secretor genotypes and serum carbohydrate antigen 19-9 levels in a Korean population

Background: The Lewis histo-blood group system consists of 2 major antigens-Le^a and Le^b-and a sialyl Lewis antigen-carbohydrate antigen (CA) 19-9. We investigated the distribution of Lewis genotypes and evaluated the relationship between the Lewis/Secretor genotypes and the serum level of CA 19-9 in a Korean population to identify whether the serum CA 19-9 levels are influenced by the Lewis/Secretor genotypes. Methods: The study included 242 individuals who had no malignancies. Lewis genotyping was performed for the 59T>G, 508G>A and 1067T>A polymorphic sites. The Secretor genotype was determined through analysis of the 357C>T and 385A>T polymorphic sites and the fusion gene. Serum CA 19-9 level was analyzed using an electrochemiluminescence immunoassay. Results: Individuals carrying the 3 common genotypes-Le/Le, Le/le^59,508, and Le/le^59,1067-accounted for 95% of the study population. In the Korean population, the allelic frequencies of Le, Le⁵⁹, le^59,508, and le⁵⁹,¹⁰⁶⁷ were 0.731, 0.010, 0.223, and 0.035, respectively. We found a significant difference in serum CA 19-9 concentrations among the 9 Lewis/Secretor genotype groups (P<0.001). The serum CA 19-9 levels in subjects with genotype groups 1 and 2 (Le/-and se/se) were higher than those with genotype groups 3-6 (Le/-and Se/-; 15.63 vs 6.64 kU/L, P<0.001). Conclusions: Le/Le, Le/le^59,508, and Le/le^59,1067 are frequent Lewis genotypes in Koreans. Because serum CA 19-9 levels are significantly influenced by the Lewis/Secretor genotypes, caution is suggested when interpreting the serum CA 19-9 levels.