Association Between Genetic Variation Of CGAS, STING And MHC Genes And Susceptibility To Cervical Precancerous Lesions

ObjectivesCervical cancer is the second most common cancer worldwide, however, owing to its slow progression, it takes several years or even decades from early precancerous to cervical cancer. Therefore, early detection of cervical precancerous lesions for the prevention and treatment of cervical cancer is of great significance. Currently, HPV is generally considered as the most important risk factor for cervical cancer. In addition, environmental factors and genetic factors also play important roles in cervical precancerous lesions and even progression of the cancer. Environmental factors, such as sexual behavior without sanitary conditions, pregnancy history, habits and customs, living environment are considered closely related to cervical precancerous lesions. However, even if exposed in the same environment or infected HPV, the risk of cervical precancerous lesions varys greatly between individuals. The effects of environmental factors are mainly determined by individual genetic susceptibility.Cyclic GMP-AMP synthase(c GAS) is a recognition receptors that can detect exogenous DNA in vivo. c GAS binds to and activates STING, thereby triggering type Ⅰinterferon production through the transduction of downstream TBK1-IRF3 and IKK- NF-κB signal pathway. The present studies show that type Ⅰ interferons play a vital role in antiviral, anti-cell proliferation, mediated innate immunity and specific immunity. Although the association between c GAS-STING innate immune signaling pathways, HPV infection and cervical precancerous lesions have not been reported yet. We supposed that the polymorphisms of the key genes in c GAS-Sting pathway, which may affect individual identification of the antiviral ability of HPV-mediated innate immune,causing a part of individuals in the status of persistent HPV infection and increase the risk of cervical precancerous lesions and even cervical cancer. In addition, genome-wide association study in Sweden find a polymorphism in MHC region which highly linked with MICA frameshift mutation A5.1, suggesting that it may be associated with the development of cervical cancer, but the association has not yet been for validation in Chinese population.Therefore, the aim of this study was to explore the association between the polymorphisms of key genes in c GAS,STING, MHC, environmental factors and the precancerosis of the cervix. Methods1.This was a 1:1 matching case-control study. The population included 296 subjects with the precancerosisof the cervix and 296 control subjects. The cervical exfoliated cells and venous blood were collected for HPV genotyping, thinprep cytologic test and DNA extraction, respectively.2.The general information of subjects were collected through epidemiological questionnaire, including general demographic characteristics(age, type of health insurance, income, etc.), history of disease, the history of menstruation, pregnancy history and personal habits and so on.3.Single nucleotide polymorphisms(SNPs) in the c GAS, STING and MHC genes on human chromosomes were screened from the Hapmap database,meanwhile,searching for locus which has not been confirmed in Chinese population. All SNPs were genotyped using the Matrix assisted laser desorption ionization time of flight mass spectrometry.4.SPSS 16.0, PHASE 2.0, and Haploview 4.0 Software were used to analysis the relationship between the polymorphisms of key genes in c GAS,STING innate immune signaling pathways and MHC region, environmental factors and the susceptibility of precancerosis of the cervix. Results1.The univariate analysis showed that there were significant differences in medical insurance, age of first sexual life, frequency of sex, frequency of passive smoking, exercise intensity, the frequency of mother pregnancy were between cervical precancerous lesions group and control group.2.The HPV genotyping test showed that HPV infection rate(73.31%) in case group was higher than control group(31.08%) with statistic difference. The major types of HPV were the same in case and control groups, including HPV52、HPV58、HPV16、HPV18. There were significant differences in infection rate of HPV52( P=0.000)、 HPV58(P=0.000) 、HPV16(P=0.003)、HPV18(P=0.034)、HPV51(P=0.002)、HPV68(P=0.017)、HPV31(P=0.001) and HPV33(P=0.038)between case and control groups. Compared with non-infection group, the risk of developing ASCUS, LSIL, HSIL of HPV infection group were 4 times(P=0.000)、9.12 times(P=0.000)and 4.41 times(P=0.000), respectively.3.Conditional logistic regression analysis with 1:1 matching showed that over early age of first sexual life(OR=0.92, P=0.000), excessive numbers of pregnancy(OR=1.23, P=0.016) and HPV infection( OR=6.23, P=0.000) were independent factors of increasing risk of developing cervical precancerous lesions.4.Nine SNPs(zh419、rs311675、rs4032697、rs7761170、rs610913、rs9352000、rs7380824、rs1131769、rs2516448)were involved in this study. Compared with c GAS-zh419 genotype AA, individual who carried genotype AG were reduced the risk of developing cervical precancerous lesions(OR=0.64, P=0.037), after adjusting age of first sexual life, the frequency of mother pregnancy and HPV infection. In the dominant genetic model, individual carrying genotype AG / GG has 0.64 times lower risk for developing cervical precancerous lesions than carrying the AA genotype(AG/GG vs AA: OR=0.64,P=0.037). The remaining eight SNPs and haplotypes were not found association with cervical precancerous lesions.5.After statistical analysis, we did not find a statistically significant interaction between gene and gene,gene and environment, environment and environment, respectively. ConclusionEarly age of first sexual life, excessive number of pregnancies and HPV infection were independent risk factor for the risk of developing cervical precancerous lesions. The polymorphism of c GAS-zh419 was associated with cervical precancerous lesions. The study has not been able to find a statistically significant interaction which can affect susceptibility to cervical lesions. The role of STING genes, MHC region locus(rs2516448) and other environmental factors in progress of cervical precancerous lesions need for further research.