RESUMO
Epigenetic silencing of cancer-related genes plays an important role in oral/oropharyngeal squamous cell carcinoma (OSCC). We evaluated promoter hypermethylation of 4 cancer-related genes in OSCCs of a Brazilian cohort and determined its relationship with exposure to alcohol, tobacco, HPV infection and clinicopathological parameters. CDKN2A (cyclin-dependent kinase inhibitor 2A or p16), SFN (stratifin or 14-3-3 σ), EDNRB (endothelin receptor B) and RUNX3 (runt-related transcript factor-3) had their methylation patterns evaluated by MSP analysis in OSCC tumors (n = 45). HPV detection was carried out by PCR/RFLP. Aberrant methylation was detected in 44/45 (97.8 %) OSCC; 24.4 % at CDKN2A, 77.8 % at EDNRB, 17.8 % at RUNX3 and 97.8 % at SFN gene. There was no significant association between methylation patterns and clinical parameters. HPV (subtype 16) was detected in 3 out of 45 patients (6 %). Our findings indicate that HPV infection is uncommon and methylation is frequent in Brazilian OSCCs, however, EDNRB and SFN gene methylation are not suitable OSCC biomarkers due to indistinct methylation in tumoral and normal samples. In contrast, CDKN2A and RUNX3 genes could be considered differentially methylated genes and potential tumor markers in OSCCs.
Assuntos
Carcinoma de Células Escamosas/genética , Metilação de DNA , Neoplasias Bucais/genética , Neoplasias Orofaríngeas/genética , Infecções por Papillomavirus/genética , Regiões Promotoras Genéticas , Proteínas 14-3-3/genética , Adulto , Idoso , Idoso de 80 Anos ou mais , Consumo de Bebidas Alcoólicas/efeitos adversos , Biomarcadores Tumorais/genética , Brasil , Carcinoma de Células Escamosas/etiologia , Carcinoma de Células Escamosas/virologia , Estudos de Coortes , Subunidade alfa 3 de Fator de Ligação ao Core/genética , Epigênese Genética , Exonucleases/genética , Exorribonucleases , Feminino , Regulação Neoplásica da Expressão Gênica , Genes Virais , Genes p16 , Papillomavirus Humano 16/genética , Humanos , Masculino , Pessoa de Meia-Idade , Neoplasias Bucais/etiologia , Neoplasias Bucais/virologia , Neoplasias Orofaríngeas/etiologia , Neoplasias Orofaríngeas/virologia , Infecções por Papillomavirus/virologia , Reação em Cadeia da Polimerase , Receptor de Endotelina B/genética , Fatores de Risco , Análise de Sequência de DNA , Fumar/efeitos adversosRESUMO
The presence of TP53 gene mutations in breast cancer has been associated with worse prognosis. These mutations interfere with the ability of the p53 protein, a transcription factor, to regulate the expression of target genes. Unlike the wild-type protein, which is rapidly degraded in cells, mutated forms have increased half-life and accumulate in tumor cells. Immunohistochemistry (IHC) is widely used in Brazil in the determination of breast cancer patients' prognosis. However, this technique is not able to detect many altered forms of the p53 protein (false-negative results) and readily detects the accumulation of wild-type p53 (false-positive results) that is associated with non-tumoral processes. For these reasons, we have set out to compare the efficiency of IHC with a molecular technique that detects gene variations at the DNA level in the evaluation of Brazilian patients with sporadic breast cancer. We have used denaturing gradient gel electrophoresis (DGGE) to study the TP53 status in 45 tumors, finding 26 allelic variants, most of them located in exon 4. Comparing the two techniques, IHC showed a false-negative rate of 64% and a false-positive rate of 50%. These results confirm the inability of IHC to correctly detect TP53 status, reason because it should not be routinely used to establish prognosis of breast cancer patients in Brazilian Pathology Laboratories. We recommend the utilization of a screening method, such as DGGE, followed by sequencing of altered exonic fragments to correctly detect TP53 gene variants and establish the prognosis of breast cancer patients.
Assuntos
Neoplasias da Mama/genética , Neoplasias da Mama/metabolismo , Eletroforese em Gel de Gradiente Desnaturante/métodos , Imuno-Histoquímica/métodos , Proteína Supressora de Tumor p53/classificação , Proteína Supressora de Tumor p53/genética , Proteína Supressora de Tumor p53/metabolismo , Brasil , Neoplasias da Mama/diagnóstico , Análise Mutacional de DNA/métodos , Feminino , Humanos , Prognóstico , Sensibilidade e EspecificidadeRESUMO
Early detection of Oral Squamous Cell Carcinoma (OSCC) is important to reduce mortality rates and to help provide successful cancer treatment. Hypermethylation of CpG islands is a common epigenetic mechanism that leads to gene silencing in tumors and could be a useful biomarker in OSCC. Abnormal DNA hypermethylation can occur very early in cancer development and may be induced by exposure to environmental carcinogens. We set out to investigate the methylation status of cancer-related genes in normal oral exfoliated cells from OSCC patients and healthy volunteers, as well as possible associations with alcohol/tobacco exposure or specific tumor characteristics. The methylation status of CDKN2A (cyclin-dependent kinase inhibitor 2A or p16), SFN (stratifin or 14-3-3 σ), EDNRB (endothelin receptor B) and RUNX3 (runt-related transcript factor-3) was evaluated by MSP (Methylation-Specific Polymerase Chain Reaction) analysis in non-neoplastic oral epithelial cells from OSCC patients (n = 70) and cancer-free subjects (n = 41). Hypermethylation was observed in CDKN2A, EDNRB and SFN genes, whereas no methylation was found in the RUNX3 gene. CDKN2A hypermethylation occurred only in the OSCC group (5.7%) while SFN and EDNRB hypermethylation occurred in both groups. There was no association between hypermethylation and smoking, drinking habits or specific tumor characteristics.