Objective: To study the relationship between TAP (transporter associated with antigen processing) gene promoter regional methylation level and cervical lesions with HPV infection in Uyghur women.
Methods: A specialized software was used to design specific primers of CpG island fragments of TAP1 and TAP2 gene promoter for PCR amplification, bisulfitemodified SiHa cancer cell DNA for PCR amplification, cloning and sequencing analysis to obtain the relevant information on the gene base sequence methylation of CpG sites. Seventy-eight fresh cervical tissue samples from Uyghur women with cervicitis (number = 15), cervical intraepithelial neoplasia (CIN, number = 30) and cervical squamous cell carcinoma (number = 33) were collected. The methylation level of TAP1 and TAP2 gene promoter regions was detected using MassArray DNA technology. HPV infection status was determined by HPV gene chips. The relationship between CpG-island methylation of gene promoter regions and HPV infection was then analyzed.
Results: Each TAP1 and TAP2 gene corresponding target fragment contained 23 and 8 CpG sites. There were 5 and 8 CpG sites methylation occurred in SiHa cervical cancer cells genomic DNA respectively. The TAP1 methylation level increased steadily with the severity of cervical lesions. The methylation levels in cervical squamous cell carcinoma and CIN (0.048 ± 0.039 and 0.037 ± 0.026, respectively) were higher than that of normal cervical tissue (0.035 ± 0.029, P < 0.05). Although TAP2 gene methylation level also demonstrated similar changes, the difference however was not statistically significant (P > 0.05). HPV gene chip detected 13 HPV genotypes, with HPV16 infection rate being 66.7% (52/78). The methylated proportion of TAP1 positively correlated with HPV16 infection (χ(2) = 6.08, P = 0.039).
Conclusion: TAP1 methylation is a remarkable phenomenon occurring in a range of cervical lesions and significantly associated with cervical HPV infection.