Functional Polymorphisms and Gene Expression of TLR9 Gene as Protective Factors for Nasopharyngeal Carcinoma Severity and Progression

Nasopharyngeal carcinoma (NPC) is a disease that is closely associated with EBV infection. Toll-like receptor 9 is an important factor mediating the interaction between EBV and the host immune response. Any genetic (single nucleotide polymorphisms, SNPs) or expression variation in TLR9 gene may modify the ability of the receptor to respond correctly to viral infection as in NPC. This study is aimed at evaluating the effect of TLR9 functional polymorphisms (TLR9-1486 T/C and TLR9-1237 T/C) and TLR9 mRNA expression in NPC severity and progression at diagnosis and after treatment. This study included 322 patients with NPC. RFLP-PCR and real-time PCR were used to assess, respectively, the genotypes and the mRNA expression of TLR9 gene. The genotyping analysis showed that the presence of mutated allele -1237C (TLR9-1237 TC+CC) was associated with large tumor size (p=0.017; OR CI 95%=1.888 (1.11-3.19)) at diagnosis. After treatment, the -1237C allele was associated with a better chance of complete remission (p=0.031, OR CI 95%=0.486 (0.25-0.95)), a lower risk of distant metastasis (p=0.028, OR CI 95%=0.435 (0.18-1.02)), and a lower risk of death by NPC (p=0.003, OR CI 95%=0.20 (0.06-0.67)). Kaplan-Meier analysis showed that patients with -1237CC and -1237TC genotypes had a better overall survival (OVS) (p<0.01) and distant metastasis-free survival (DMFS) (p<0.05). A multivariate analysis revealed that TLR9-1237 T/C polymorphism was an independent prognostic factor in OVS (p=0.02; HR=0.244) and DMFS (p=0.048; HR=0.388). The transcriptomic analysis showed that the mRNA expression was reduced in patients with larger tumor size (T4) (p=0.013) and advanced clinical stage (SIII-SIV) (p=0.037). The TLR9 mRNA expression was inversely correlated with tumor size (p=0.014; r=−0.314) at diagnosis. Our results indicated for the first time that the functional -1237 T/C polymorphism and mRNA expression of TLR9 gene may be considered as protective factors for NPC severity and progression.