Human glutathione peroxidase codon 198 variant increases nasopharyngeal carcinoma risk and progression.

PURPOSE: Glutathione peroxidase 1 (GPx-1) is a selenium-dependent detoxifying enzyme involved in the protection of cells against oxidative damage. Some genetic association studies reported significant associations between GPx-1 Pro198Leu variant and carcinogenesis across different populations; however, the impact of this variant on nasopharyngeal carcinoma (NPC) has not been explored. Therefore, the present study was planned to evaluate the potential involvement of the GPx-1 Pro198Leu variant and plasma GPx activity in the risk of developing NPC in a Tunisian population. METHODS: The GPx-1 Pro198Leu genotype was determined in 327 NPC patients and 150 healthy controls by the RFLP-PCR analysis. The correlation between the GPx-1 variant and the clinicopathological parameters was examined. GPx activity was assessed in the plasma of 119 NPC patients and 58 healthy control subjects and according to GPx-1 genotypes and clinicopathological characteristics of NPC patients. RESULTS: A significant association was found between GPx-1 Pro198Leu variant and NPC risk in a Tunisian population. The allelic frequencies of Pro and Leu alleles were 32% versus 68% and 41% versus 59% in NPC cases and controls, respectively. Thus, the minor 198 Leu allele increased significantly in NPC patients and appeared as a potential risk factor for NPC occurrence (OR = 1.48, CI 95% = 1.14-1.91, p = 0.002). The plasma GPx activity was significantly higher in NPC patients than in controls (p = 0.03). According to the clinicopathological characteristics of NPC patients, GPx activity decreased significantly in patients with lymph node metastasis (p = 0.004). CONCLUSION: This is the first study showing a strong association between GPx-1 Pro198Leu genetic variant and NPC risk. GPx-1 Pro198Leu variant increased the development of regional lymph node metastasis. Plasma GPx activity was higher in NPC patients. Thus, GPx-1 gene could be considered as a determinant factor influencing NPC risk and progression.

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.