Several studies have demonstrated the existence of DNA repair SNPs responsible for the induction and/or progression of neoplasms . Among these polymorphisms, the rs13181 variant of the ERCC2 gene, also known as ERCC2 Lys751Gly, can alter the enzymatic activity of some encoded proteins, such as helicase, and may be associated with several types of cancer, including gliomas [10, 13].
To the best of our knowledge, this is the first study to evaluate the expression of SNP rs13181 of the ERCC2 gene between high- and low-grade gliomas using DNA samples isolated from neoplastic tissue stored in paraffin blocks in Brazilian patients. In the current study, the patient groups with high- and low-grade gliomas were homogeneous regarding sex, smoking, alcohol use, and family cancer history. However, the mean age of patients with high-grade gliomas was significantly higher than those with low-grade gliomas, while no statistically significant difference was observed in the expression of GG, GT, and TT genotypes.
As for the epidemiological characteristics of the patients, some studies reported a higher prevalence of gliomas in males and no association between sex and the histological grade of these tumors [14–16], corroborating the results of the present study. There was no difference between family history of cancer and gliomas, perhaps because this association is more common in certain types of syndromes, such as Li Fraumeni, Turcort, neurofibromatosis, among others , which did not occur in this study. There was also no association between gliomas and smoking or alcohol consumption; however, some authors reported a higher risk for high-grade gliomas in cases of excessive smoking  and alcohol use [19, 20]. High-grade gliomas occur in older patients [14–16], corroborating the present study results, as cellular aging increases immunological senescence, telomere shortening, chronic inflammation with antigenic stimulation, genomic instability, and mutations forming more aggressive neoplasms such as high-grade gliomas .
Some studies have shown an association between the rs13181 variant of the ERCC2 gene and the risk of developing gliomas [21, 22, 23]. However, most of these studies were conducted only in Asian populations and showed contradictory results regarding the influence of genotypes of this variant in the development of glial tumors [24–28]. In the present study, the rs13181 SNP of the ERCC2 gene was found in all samples. However, no statistically significant differences in the expression of the GG, GT, and TT genotypes between high- and low-grade gliomas were observed, consistent with the findings of Qian et al.  and Zhou et al. , and divergent from those of Huang et al. , Cui et al.  and Jia et al. , who showed an increased risk, particularly in relation to the GT genotype in the Asian population.
The absence of an association between genotypes and the degree of malignancy of glial tumors in the current study may be due to its small sample size and the lack of a consistent genetic pattern in the Brazilian population. Brazil has a rich mixture of Europeans, Africans, and Indians, presenting different results from those found in other countries, where the populations are predominantly Caucasian, Asian, or African .
In conclusion, in the current study, patients with low-grade gliomas had a significantly lower mean age than high-grade glioma patients, and the ERCC2 rs13181 genotypes found were TT, GG, and GT; however, no difference in the expression between high- and low-grade gliomas was found in patients in Northeast Brazil. Nevertheless, further studies should be carried out with a larger sample size due to the rich Brazilian racial miscegenation.