Contribution of Nitric oxide synthase 3 genetic variants to nasopharyngeal carcinoma risk and progression in a Tunisian population.

PURPOSE: We conduct this study to evaluate the clinical and functional impact of Nitric Oxide Synthase 3 (NOS3) T-786C and G894T genetic variants on nasopharyngeal carcinoma (NPC) risk and progression in a Tunisian population. METHODS: 259 NPC patients and 169 healthy controls were enrolled into our case-control study. Blood samples were genotyped by the RFLP-PCR analysis. The levels of Nitric oxide (NO) were measured by a colorimetric assay kit in the plasma of NPC patients, healthy controls and according to NOS3 genotypes. The correlation between the NOS3 variants and the clinicopathological parameters was examined. RESULTS: We found no linkage disequilibrium between NOS3 T-786C and G894T variants. These results showed that NOS3 variants were genetically independent. In contrast to NOS3 T-786C, a significant association was found between NOS3 G894T polymorphism and NPC risk. The 894T allele decreased significantly in NPC patients and appeared as protective factor (OR = 0.65, CI 95%= 0.48-0.88, p = 0.006). NPC patients had significantly higher levels of plasma NO as compared to healthy controls (p = 0.0011). The T-786C mutation reduced the levels of plasma NO and decreased risk of lymph node metastasis in NPC patients (OR = 0.64, 95% CI = 0.43-0.96; p = 0.03). In contrast, NOS3 G894T polymorphism had no effects neither on NO plasma levels nor clinical parameters. CONCLUSIONS: This is the first study to associate NPC with significantly higher levels of plasma NO. NOS3-derived NO could play key roles in NPC pathogenesis. NOS3 variants differently contribute to NPC risk and progression in a Tunisian population. NOS3 G894T was associated with NPC risk. NOS3 T-786C decreased the levels of plasma NO and reduced the development of regional lymph node metastasis.