Evaluation of the frequency of G-765C polymorphism in the promoter region of the COX-2 gene and its correlation with the expression of this gene in the endometrium of women with endometriosis.

Objective: To evaluate the frequency of polymorphism G-765C (rs20417) of the COX-2 gene and the expression of this gene in the endometrium of women with endometriosis.

Study Design: This is a case-control study of 365 women with endometriosis (251 infertile and 114 fertile) submitted to laparoscopy/laparotomy with histological confirmation of endometriosis. The control group was composed of 522 fertile women without endometriosis. Of these, 37 patients from the endometriosis group and 47 from the control group were submitted to biopsy of the endometrium for analysis of the expression of the COX-2 gene. The genotypes were determined using analysis by High-Resolution Melt. Gene expression was measured by qRT-PCR with TaqMan methodology using the GAPDH gene as normalizer of the reactions.

Results: The distribution of the genotypes and alleles in the group of fertile women with moderate/severe endometriosis showed a statistically significant difference, demonstrating association of the ancestral allele, -765G, with increased risk of endometriosis (p = 0.028; OR 0.53; CI 0.32-0.90). The mean expression of the COX-2 gene (mRNA PTGS2) in the group of women with endometriosis was statistically higher compared to the control group (3.85 versus 2.84, p = 0.028).

Conclusion: The present study identified that in Brazilian women the presence of the ancestral allele, -765G, of the COX-2 gene is associated with an increased risk for development of moderate/severe endometriosis associated with fertility, and that the eutopic endometrium of women with endometriosis showed increased expression of COX-2 when compared to the control group.