RESUMO

Background: Two recurrent TERT (telomerase reverse transcriptase) promoter mutations, C228T and C250T, have been reported in thyroid carcinomas and were correlated with high-risk clinicopathological features and a worse prognosis. Although far more frequent in the poorly differentiated and undifferentiated thyroid cancer, the TERT promoter mutations play a significant role on PTC recurrence and disease-specific mortality. However, the prevalence varies considerably through studies and it is uncertain if these differences are due to population variation or the methodology used to detect TERT mutations. In this study we aim to compare three different strategies to detect TERT promoter mutations in PTC. Methods: DNA was isolated from formalin-fixed paraffin-embedded (FFPE) specimens from 89 PTC and 40 paired lymph node metastases. The prevalence of the hot spot TERT C228T and C250T mutations was assessed in FFPE samples using TaqMan SNP genotyping assays. Random samples were tested by Sanger Sequencing and droplet digital PCR (ddPCR). Results: In general, 16 out of 89 (18%) PTC samples and 14 out of 40 (35%) lymph node metastases harbored TERT promoter mutations by TaqMan assay. Sanger sequencing, performed in random selected samples, failed to detect TERT mutations in four samples that were positive by TaqMan SNP genotyping assay. Remarkably, ddPCR assay allowed detection of TERT promoter mutations in six samples that harbor very low mutant allele frequency (≤ 2%) and were negative by both genotype assay and Sanger Sequencing. Conclusion: This study observed a good concordance among the methodologies used to detect TERT promoter mutations when a high percentage of mutated alleles was present. Sanger analysis demonstrated a limit of detection for mutated alleles. Therefore, the prevalence of TERT promoter mutations in PTC may be higher than previously reported, since most studies have conventionally used Sanger sequencing. The efficient characterization of genetic alterations that are used as preoperative or postoperative diagnostic, risk stratification of the patient and individualized treatment decisions, mainly in highly heterogeneous tumors, require highly sensitive and specific approaches.

Assuntos

Mutação , Regiões Promotoras Genéticas , Análise de Sequência de DNA/métodos , Telomerase/genética , Câncer Papilífero da Tireoide/diagnóstico , Câncer Papilífero da Tireoide/genética , Neoplasias da Glândula Tireoide/diagnóstico , Neoplasias da Glândula Tireoide/genética , Alelos , DNA/genética , Reações Falso-Negativas , Genótipo , Humanos , Metástase Linfática , Polimorfismo de Nucleotídeo Único , Prevalência , Prognóstico , Reprodutibilidade dos Testes , Câncer Papilífero da Tireoide/epidemiologia , Neoplasias da Glândula Tireoide/epidemiologia

RESUMO

Background: Head and neck squamous cell carcinoma (HNSCC) is usually associated to tobacco and alcohol consumption. Increased telomerase activity has been consistently detected in 80-90% of malignant tumors, including HNSCC. Mutations within the promoter region of telomerase reverse transcriptase (TERT) that confer enhanced TERT promoter activity have been reported in two major hotspots, designated C228T and C250T. Objectives: To evaluate TERT promoter mutations C228T and C250T in HNSCC patients from Brazil and correlate with patients' outcome. Materials and Methods: Formalin-fixed paraffin-embedded tissues were obtained from 88 HNSCC patients and analyzed for TERT promoter mutations C228T and C250T by pyrosequencing. Results: The overall prevalence of hotspot TERT mutations in HNSCC samples was of 27.3%, with 6.8% at locus C228T and 20.5% at C250T. The majority (92%) of mutated cases were located in oral cavity, mainly at the tongue. We observed that 94.4% of the patients harboring TERT promoter mutation C250T were alcohol consumers (p = 0.032) and 66.7% of the patients harboring TERT promoter mutation C228T were not alcohol consumers (p = 0.035). The presence of C228T mutation impacted patient outcome, with a significant decrease in disease-free survival (20.0 vs. 63.0%, p =0.017) and in overall survival (16.7 vs. 45.1%, p = 0.017). Conclusion: This is the first report of a TERT promoter mutations in HNSCC patients from South America. The high prevalence of TERT mutation, as well as its association with poor disease-free survival and overall survival, particular at C228T locus might serve as a prognostic biomarker in HNSCC to help clinicians in the management of treatment.