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Human papillomavirus (HPV) infection is necessary but not a sufficient cause for the development of invasive cervical cancer (ICC). Epithelial tissues, target for HPV, are exposed to reactive oxygen species (ROS) associated with tumor initiation and progression. The NADPH oxidase (NOX) and catalase (CAT) are involved in hydrogen peroxide (H2O2) production and inactivation, respectively. P22phox is the NOX subunit encoded by the CYBA gene that has a functional polymorphism (C-242T). This protein is involved in the regulation of electron transfer to oxygen. CAT is a hemic enzyme that plays a role in regulating H2O2 concentration, with a functional polymorphism (C-262T) in its gene. We evaluated CYBA C-242T and CAT C262T genetic polymorphisms and their interaction in 132 women with ICC. We found that CYBA C-242T and CAT C262T genotype frequencies were significantly different between ICC and controls (χ (2) test, p = 0.017 and p = 0.009, respectively). Women with the C/T CYBA-242 genotype had a lower risk for ICC development (odds ratio (OR) = 0.515, 95% confidence interval (CI) 0.291-0.914, p = 0.023) whereas T/T CAT-262 genotype carriers present an increased risk for ICC (OR = 3.034, 95% CI 1.462-6.298, p = 0.003). Women with C/C genotype for CYBA and T/T genotype for CAT had an increased risk to develop ICC comparing with the interaction of the other possible genotypes of both genes (OR = 3.952, 95% CI 1.075-14.521, p = 0.032). The CYBA C-242T and CAT C-262T genetic polymorphisms and their epistatic interactions can be associated with ICC through mechanisms related with the role of ROS in cell proliferation and apoptosis.

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Cervical cancer is the fourth most common cancer affecting women worldwide, according to the latest IARC release with 528 000 new cases every year. Infection by high-risk human papillomavirus (HPV) is necessary but not sufficient for progression to cancer. Epithelial tissues, the target of HPV infection, are heavily exposed to reactive oxygen species (ROS). Hypochlorous acid (HOCl) is a very potent ROS, and it is produced by myeloperoxidase (MPO). MPO, a lysosomal enzyme expressed in polymorphonuclear neutrophils (PMN), has the potential to kill HPV transformed cells, as a component of an intercellular induced-apoptosis pathway. This enzyme catalyzes the production of HOCl in the presence of hydrogen peroxide (H2O2). The H2O2 produced by the Doderlein's bacillus will interact with MPO, contributing to the intercellular induced-apoptosis pathway. We studied a functional polymorphism in the promoter region of MPO (G463A) and how it may affect the risk of developing cervix cancer. A sample of 100 patients with invasive cervical cancer and 122 control women were genotyped for MPO polymorphism by PCR-RFLP method. The statistical method used was χ(2). We found that women with the GG genotype had lower risk for cervical cancer than the women who displayed the heterozygous genotype GA (OR = 0.546, 95 % CI = 0.315-0.939, p = 0.028, OR = 2.210, 95 % CI = 1.257-3.886, p = 0.008, respectively). The genotype that leads to a higher concentration of ROS (GG) presents itself as a protection factor in comparison to the homozygous genotype (AA). This can be explained by the interaction of HOCl and superoxide of transformed cells that will generate apoptosis-inducing hydroxyl radicals.

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