Synergistic effect of interleukin-6 promoter (IL6 -634C/G) and intercellular adhesion molecule-1 (ICAM-1 469K/E) gene polymorphisms on the risk of endometriosis in Japanese women

PROBLEM: Endometriosis is an immune-related, chronic inflammatory disease with a polygenic predisposition. The aim of this study was to investigate whether the interleukin-6 (IL-6) gene promoter region polymorphism (-634C/G) and the intercellular adhesion molecule-1 (ICAM-1) gene 469K/E polymorphism are responsible in part for the genetic susceptibility to endometriosis. METHODS OF STUDY: The IL-6 -634C/G and ICAM-1 469K/E genotypes were determined in 202 patients with endometriosis and 236 control women by polymerase chain reaction-restriction fragment length polymorphism. RESULTS: There were no differences in the IL-6 -634C/G or the ICAM-1 469K/E genotypes and allele frequencies between control women and endometriosis patients collectively, or between control women and each clinical subgroup of endometriosis patients. Interestingly, the frequency of ICAM-1 EE homozygotes who concomitantly carried the IL-6 -634G allele was significantly higher in patients with endometriosis (chi(2) = 6.458, P = 0.0396, d.f. = 2). CONCLUSION: Our results suggest that the IL-6 -634C/G and ICAM-1 469K/E polymorphisms synergistically affect the susceptibility for endometriosis in the Japanese population.