EP84 – Validation of Genetic Alterations Obtained By Exome Sequencing of Ret and Ras Negative Medullary Thyroid Carcinoma

      Ciampi, Raffaele1; Falco, Antonino1; Romei, Cristina1; Casella, Francesca1; Tacito, Alessia1; Vitti, Paolo1; Elisei, Rossella1 1 Unit of Endocrinology – Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy   Background/Purpose: About 60% of sporadic Medullary Thyroid Carcinomas (MTC) harbor somatic mutations in RET and RAS genes while roughly 40% of cases are still orphan of an oncogenic driver. Next generation sequencing (NGS) is a very promising technique but, so far, it failed in finding novel significative genetic alterations. Aim of this project was to validate and analyze 57 single nucleotide variations (SNV) previously identified by exome sequencing (WES) performed in 3 patients, affected by sporadic RET/RAS- MTC and 1 patient affected by FMTC. Methods: Sanger sequencing of genomic DNA (gDNA) for validation of the 57 SNV and TaqMan SNP genotyping for SNP prevalence in the additional 872 MTC gDNA. Results: SNVs were all missense, heterozygous, with a MAF?0.01, with high pathogenicity score values and in genes potentially involved in carcinogenesis. Fiftythree/57 (92.9%) germline mutations were validated. We then focused on 28 mutations in the FMTC patient two family members: affected and healthy. Two rare SNPs in the KIAA1522 (rs372939895) and in the REM1 (rs760417150) genes were present only in affected patients. Hypothesizing a general predisposing role of these SNP, we genotyped gDNA of additional 872 patients, detecting no additional cases that represented significative “private mutations” of this family. Discussion & Conclusion: In conclusion, we validated 92.9% mutations obtained by WES of 4 MTC patients. SNPs segregating with the disease represented “private” mutations of this family. Despite the great potentiality of WES, we did not find any additional oncogenic driver for MTC.


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