The tumor necrosis factor-α promoter −1031C polymorphism is associated with decreased risk of endometriosis in a Japanese population

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Abstract
BACKGROUND: Tumor necrosis factor-α (TNF-α) is a multifunctional proinflammatory cytokine, associated with various inflammatory and autoimmune diseases. Elevated TNF-α levels in peritoneal fluid have been reported in women with endometriosis, suggesting that TNF-α may be involved in the development of endometriosis. In this study, we investigated the possible association between endometriosis and the TNF-α gene promoter polymorphisms −238G/A, −308G/A, −857C/T, −863C/A and −1031T/C in a Japanese population. METHODS: We compared the distribution of the −238G/A, −308G/A, −857C/T, −863C/A and −1031T/C polymorphisms in the promoter region of TNF-α in 130 endometriosis cases and 185 controls using PCR–RFLP analysis. RESULTS: The allele frequencies of −238A, −308A, −857T, −863A and −1031C in controls were 2.0%, 1.3%, 19.4%, 17.0% and 18.6%, and in the cases 1.1%, 0.3%, 19.6%, 18.6% and 13.6%, respectively. No significant differences in frequencies were found between the crude endometriosis cases and controls. However, when the endometriosis group was divided into a subgroup of women with stage IV disease only, the frequency of the −1031C allele was significantly lower in this subgroup than controls. CONCLUSIONS: The variability of the −1031T/C polymorphism of the TNF-α gene may be associated with susceptibility to (AUTHOR: as meant?) endometriosis.