ORAL COMMUNCATION 20 Exome-Sequencing in familial thyroid carcinoma: genetic and functional characterization Catarina Salga<strong>do</strong> 1 , Hugo Prazeres 1,2 and Paula Soares 1,3 1 IPATIMUP - Instituto de Patologia e Imunologia Molecular da <strong>Universidade</strong> <strong>do</strong> <strong>Porto</strong>, <strong>Porto</strong>, Portugal; 2 IPO-C – Instituto Português de Oncologia de Coimbra, Coimbra, Portugal; 3 FMUP – Faculdade de Medicina da <strong>Universidade</strong> <strong>do</strong> <strong>Porto</strong>, <strong>Porto</strong>, Portugal Thyroid tumors are the most frequent en<strong>do</strong>crine neoplasia [1]. These tumours may occur sporadically or in a familial context, as is the case of familial nonmedullary thyroid cancer (FNMTC) [2]. FNMTC is a familial form of thyroid cancer whose genetic cause is still unknown [3,4] Next-Generation Sequencing (NGS) technologies are enabling a new way to explore disease-causing mutations, namely in the field of oncobiology research [5,6]. The main goal of this work was to expand the genetic profile of FNMTC through NGS of different samples of one family displaying clinicopathological features suggestive of hereditary disease. Novel germline variants as well as somatic mutations occurring de novo in the tumour tissue were confirmed by PCR (Polimerase Chain Reaction) and Sanger Sequencing. From 35 candidate germline alterations identified by NGS, 1 nonsense mutation in PRAMEF1 gene (p.L105*) was shared among affected individuals of the same family. Despite being present in a control population, distribution of this variant was significantly different from Hardy-Weinberg equilibrium, no homozygote was found in the control group. This can be taken to indicate that this variant is deleterious when in homozygosity. In terms of somatic mutations, out of 103 candidate changes identified by NGS, 88 (85%) proved to be false-positive and 15 variants were confirmed by Sanger Sequencing. Of these, 8 were evaluated as they were classified as probably and possibly damaging by the program Polyphen-2. In this analysis loss of heterozygosity in the gene GRID2IP was observed. Following-up on this observation, in vitro experiments were conducted using an siRNA in order to reduce GRID2IP gene expression, mimicking inactivation observed in the tumor. The reduction in GRID2IP gene expression did not result in significant changes to the proliferation rate or apoptosis. Nevertheless, GRID2IP knock <strong>do</strong>wn led to an observable decrease in actin labeling at the plasma membrane, which reinforces the role of this protein in anchoring the actin cytoskeleton to the membrane and may indicate that GRID2IP is a tumor suppressor gene in follicular thyroid carcinoma (FTC). References: [1]DeLellis, R.A., et al. (2004) Pathology and genetics of tumours of en<strong>do</strong>crine organs. p. 320. [2]Sherman, S.I. (2003) Thyroid carcinoma. Lancet, 361(9356), p. 501-11. [3]Nikiforova, M.N., et al. (2003) BRAF mutations in thyroid tumors are restricted to papillary carcinomas and anaplastic or poorly differentiated carcinomas arising from papillary carcinomas. J Clin En<strong>do</strong>crinol Metab, 88(11), p. 5399-404. [4]Prazeres, H., et al. (2010) The familial counterparts of follicular cell--derived thyroid tumors. Int J Surg Pathol, 18(4), p. 233-42. [5]Mardis, E.R. (2008) Next-generation DNA sequencing methods. Annu Rev Genomics Hum Genet, 9, p. 387-402. [6]Meyerson, M., S. Gabriel, and G. Getz. (2010) Advances in understanding cancer genomes through second-generation sequencing. Nat Rev Genet, 11(10), p. 685-96. 38
39 Posters