Influência de marcadores genéticos e epigenéticos na ocorrência de mucosite oral quimioinduzida em pacientes oncopediátricos

Abstract

Chemoinduced oral mucositis (OM) is a tissue inflammatory response to the biochemical action of chemotherapy, commonly observed in patients using Methotrexate (MTX). This drug, in turn, is related to an alteration of inflammatory cytokines, such as interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α), and an oxidative imbalance, which can reduce the activity of antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT). In addition, vitamin D levels were also associated with the occurrence of OM. Studies have shown that the mechanism of MTX toxicity is related to genetic alterations, such as single nucleotide polymorphisms, and in the epigenetic profile of patients, especially with regard to DNA methylation. Therefore, the objective was to analyze the influence of genetic and epigenetic modifications in genes that encode the vitamin D receptor and genes involved in inflammatory mechanisms and oxidative stress. We analyzed whether the BsmI G>A (rs1544410), FokI C>T (rs2228570) and TaqI T>C (rs731236) polymorphisms in the VDR gene, as well as the methylation profile in the VDR, CAT, SOD3, IL-6 and TNF-α were associated with the occurrence of chemoinduced oral mucositis in pediatric oncopediatric patients treated with MTX. To this end, a study was carried out with 123 patients (5 to 19 years old), of which 102 were from the Hospital Napoleão Laureano (João Pessoa-PB) and had a diagnosis of leukemia or lymphoma and were treated with MTX, and 21 were selected healthy individuals. private dental clinic. OM was assessed using the modified Oral Assessment Guide. Demographic, clinical, hematological and biochemical data were collected from medical and dental records. Samples of buccal epithelial cells were obtained by mouthwash and genomic DNA was extracted for analysis of polymorphisms by the PCR-RFLP technique (Polymerase Chain Reaction – Restriction Fragment Length Polymorphism) and for analysis of DNA methylation by MSP (Methylation Specific PCR). Statistical analysis was performed using Chi-square, Fisher's exact, Mann-Whitney U, Dwass-Steel-Critchlow-Fligner tests for multiple comparisons and Hard-Weinberg balance (p<0.05). The study of polymorphism in the VDR gene included 102 oncopediatric patients, in which a prevalence was observed in males (57.8%) and mean age was 10.3 years (±4.7). OM affected 84.3% of the patients, of which 53.1% developed the severe form of the disease (MOG). There was an association between the CT genotype of the FokI C>T polymorphism (rs2228570) (OR=1.81; CI=0.58–5.66; p=0.038), as well as the G allele of the BsmI G>A polymorphism (rs1544410) (OR=2.27; CI=1.01–5.11; p=0.040) with MOG. The study of methylation in the VDR, CAT, SOD3, IL-6 and TNF-α genes involved 85 individuals, 21 healthy individuals and 64 pediatric oncopediatric patients. Females predominated (54.1%), with a mean age of 11.1 years (±4.3) and diagnosis of acute lymphoblastic leukemia (56.5%). Most cancer patients (75.0%) developed OM. There was a difference in the methylation profiles of the TNF-α gene between the groups (p=0.004), with the non-methylated profile being more frequent in patients who had recovered from mucositis when compared in isolation with patients who had mucositis in the time of sample collection (p=0.049). Therefore, it is concluded that both genetic and epigenetic modifications are associated with oral mucositis. The FokI C>T (rs2228570) and BsmI G>A (rs1544410) polymorphisms in the VDR gene increase the chance of severe oral mucositis and the TNF-α methylation profile is associated with the post-mucositis period in pediatric oncology patients.