Aline Neves Araujo
Genome-Wide Copy Number Analysis in a Family with p.G533C RET Mutation and Medullary Thyroid Carcinoma Identified Regions Associated with Higher Predisposition to Lymph Node Metastasis
Araujo AN 1, Moraes LS 1, França MIC 2, Maciel RMB 2 and Cerutti JM 1
1 Genetic Bases of Thyroid Tumors Laboratory, Division of Genetics, Department of Morphology and Genetics, Universidade Federal de São Paulo, SP, Brazil.
2 Laboratory of Molecular and Translational Endocrinology, Division of Endocrinology, Department of Medicine, Universidade Federal de São Paulo , SP, Brazil.
BACKGROUND: Our group described a p.G533C RET mutation in a family with multiple endocrine neoplasia type 2A syndrome. Clinical heterogeneity was observed among the p.G533C-carries, mainly associated with the presence of lymph node metastases. The aim of this study was to investigate whether copy number variations (CNV), present in the constitutional DNA, is associated with higher predisposition to lymph node metastasis in this kindred.
METHODS: Fifteen p.G533C carriers with medullary thyroid carcinoma (MTC) were chosen for the initial screening. The subjects were divided into two groups according the presence (n=8) or absence (n=7) of lymph node metastasis. Peripheral blood DNA was independently hybridized using Genome-Wide Human SNP Array 6.0 platform and the results were analyzed using Genotyping Console software. To identify the possible candidate regions associated with the presence of lymph node metastasis, cases (metastatic MTC) were compared with controls (nonmetastatic MTC). The identified CNVs were validated by quantitative PCR in an extended cohort (n=26).
RESULTS: We identified seven CNV regions that were associated with presence of lymph node metastases, some of them encompass non-annotated and annotated genes. The validation step confirmed that a CNV loss impacting the FMN2 gene was associated with a more aggressive phenotype, observed as presence of lymph node metastasis in this family (p ≤ 0.05). We additionally verified the association of CNVs with clinical-pathological features and observed an association between a CNV loss, which comprise the LCE3C gene, and tumor size (p ≤ 0.05). Finally, we investigated whether the development of lymph node metastasis might depend on a combination of various CNVs. These analyses defined a CNV pattern related to a more aggressive phenotype in this family, with CNV deletions being enriched in the metastatic group (p ≤ 0.05).
CONCLUSION: Although hereditable specific RET mutations are important to determine cancer risk; our findings support the hypothesis that germline CNVs in disease-affected individuals may predispose them to MTC aggressiveness, mainly associated with the presence of lymph node metastases.