Objective: To investigate the association of tumor necrosis factor-alpha (TNF-α) gene promoter region -1031T/C and its combination with interleukin-6 (IL-6) gene promoter region -634C/G single nucleotide polymorphisms (SNP) with the genetic susceptibility to endometriosis.
Methods: Total of 432 endometriosis patients and 499 non-endometriosis women who had received an operation due to tubal ligation, tubal recanalization, laparoscopic hydrotubation, ovarian simple cyst and teratoma were collected and separated into endometriosis group and control group, that all cases were confirmed by operation and pathology. A case-control study was performed in endometriosis and control group to evaluate the association of these SNP with the susceptibility to endometriosis by using a fluorescent quantitative PCR-based high resolution melting (HRM) method.
Results: (1) TNF-α -1031T/C genotype:the T and C of TNF-α -1031T/C allele frequencies in the endometriosis group and control group were 79.2% (684/864), 20.8% (180/864) and 81.8% (816/998), 18.2% (182/998), respectively. The TT, TC and CC of TNF-α -1031T/C genotype frequencies in the two groups were 63.7% (275/432), 31.0% (134/432), 5.3% (23/432) and 66.5% (332/499), 30.5% (152/499), 3.0% (15/499), respectively. There were no statistical significances in the TNF-α -1031T/C alleles and genotypes distributions between the two groups (P = 0.158, P = 0.186). (2) TNF-α -1031T/C and IL-6 -634C/G conjoint genotypes: to research on the TNF-α -1031T/C and IL-6 -634C/G genotypes for conjoint analysis, the TT+CC, TC+CC, CC+CC, TT+CG, TC+CG, CC+CG, TT+GG, TC+GG and CC+GG combination genotype frequencies in the two groups were 39.4% (170/432), 19.4% (84/432), 4.6% (20/432), 20.6% (89/432), 8.8% (38/432), 0.9% (4/432), 3.5% (15/432), 2.3% (10/432), 0.5% (2/432) and 36.7% (183/499), 17.4% (87/499), 1.4% (7/499), 26.1% (130/499), 10.4% (52/499), 1.2% (6/499), 3.8% (19/499), 2.6% (13/499), 0.4% (2/499), respectively. There were no statistical significances in the combination genotypes distributions between the two groups (P = 0.107). As compared with carriers of TT+CC combination genotype, the endometriosis risk of carriers of CC+CC combination genotype enhanced 3.076 times (95%CI: 1.268 - 7.457, P = 0.009), and the endometriosis risk of carriers of other combination genotypes were no statistical significances (all P > 0.05).
Conclusions: The study demonstrates that there are no significant association between the SNP of TNF-α -1031T/C and genetic susceptibility to endometriosis. However the results indicate that there are significant association between genetic susceptibility to endometriosis and the combination polymorphisms of TNF-α -1031T/C and IL-6 -634C/G.