Investigation of chromosomal rearrangements in the BRAF gene in differentiated thyroid carcinomas in childhood

Abstract

The thyroid cancer, although it is considered rare when compared to other forms of more common cancers in the population, accounts for approximately 90% of all cancers related to the endocrine system and the most deaths from endocrine neoplasia. In pediatric patients, this type of carcinoma accounts for 0.5 to 3% of all cancers in the US and Europe, and could reach 2% in Brazil. However, when compared to adults, the risk of metastases is higher in children. Carcinomas of thyroid can derive both from follicular cells (classified in differentiated, poorly differentiated and undifferentiated) and parafollicular cells (classified in medullary). The differentiated thyroid carcinoma (DTC) is the subtype of higher incidence both in adults (70 to 80%) and children (90%). Furthermore, the tumors have been classified as sporadic and induced by radiation. When the thyroid carcinomas occur in childhood, risk factors such as age, family history and exposure to radiation are important data. As sporadic thyroid neoplasm have low incidence in the pediatric population, population studies are rare, resulting in shortage of information and hindering the establishment of appropriate conduct when diagnosed in this group. Mutations in BRAF and RAS genes and the rearrangements RET/PTC and NTRK1 have been predominantly identified in the DTC in adults. However, mutations in BRAF are rare in the pediatric age group. Moreover, chromosomal rearrangements involving this gene have been identified in pediatric PTC. Thus, the objective of this project is to determine the prevalence of BRAF rearrangements involving pediatric DTC using the technique of FISH dual-color break-apart. To identify genes that are fused to BRAF it will be used RACE technique, which constitutes in synthesis of chimeric cDNA resulting from chromosomal rearrangements involving BRAF, followed by amplification of chimeric cDNAs and further sequencing of them. In this case, the "unknown" end of the "known" gene (BRAF), involved in the rearrangement, may be 3 'or 5', depending on where the chromosomal breakage occurred. Thus, the results derived from this project will help in the understanding of the molecular mechanisms involved in thyroid carcinomas in the pediatric group, besides providing aids for the establishment of appropriate conduct in thyroid carcinomas diagnosed in children and adolescents.