ANKRD26-RET - A novel gene fusion involving RET in papillary thyroid carcinoma.

BACKGROUND: Rearrangements of RET are drivers of oncogenesis, traceable in different cancer types as papillary thyroid carcinoma (PTC), non-small cell lung cancer, colorectal or breast cancer. Anchored multiplex PCR based next-generation sequencing (NGS) can detect RET rearrangements involving previously unknown partner genes. METHODS: A sample of PTC underwent NGS, following detection of RET rearrangement by fluorescence in situ hybridization. Expression analysis of ANKRD26 and RET was performed for the tumor harboring ANKRD26-RET, for corresponding normal thyroid tissue and PTC tumors with representative genetic alterations (BRAFV600E, CCDC6-RET), complemented by a comparative search in the "UniProt" database. RESULTS: NGS analysis resulted in the discovery of the fusion ANKRD26-RET. ANKRD26 mRNA was expressed in all PTC tumors (ANKRD26-RET, BRAFV600E, CCDC6-RET) and in normal thyroid tissue, whereas RET mRNA was detected only in the tumors with RET rearrangement. On protein level, ANKRD26-RET combines the RET tyrosine kinase to ankyrin repeat and coiled-coil domains. CONCLUSIONS: ANKRD26-RET is a novel rearrangement of the RET gene, associated with RET expression in thyroid tissue. The result is a fusion of the RET tyrosine kinase to prominent protein-protein interaction motifs. Further studies are required to investigate the influence of different RET rearrangements on metastasis and disease-free survival in PTC.

Detection of RET rearrangements in papillary thyroid carcinoma using RT-PCR and FISH techniques - A molecular and clinical analysis.

INTRODUCTION: Oncogenic BRAF and RAS mutations as well as multiple known (and yet unknown) RET fusion oncogenes comprise the majority of causative molecular alterations in papillary thyroid carcinoma (PTC). Apparently "mutation-negative" PTCs encompass a heterogenous group impeding analysis of prognostic significance of underlying genetics. MATERIAL AND METHODS: BRAF wild type PTC tissue of 56 patients was analyzed using two established methods: hybrid-specific RT-PCR for the predominant rearrangement RET/PTC1 and fluorescent in situ hybridization (FISH). Clinical features of the cases with and without RET rearrangement were compared (patient age, gender, tumor size, focality, lymph node affection, and iodine avidity). RESULTS: RT-PCR revealed RET/PTC1 rearrangements in five of 56 tumors (9%). FISH confirmed these, and identified four additional RET rearrangements (9/56; 16%). Loss of the iodine avidity only occurred in cases of RET/PTC hybrids (7/9 tumors), but not in RET/PTC-negative PTCs (0/41 tumors with available uptake information; p = 0.029). The risk to develop lymph node metastases was eight times higher in presence of RET rearrangements (p = 0.010). CONCLUSIONS: FISH analysis, in contrast to hybrid-specific RT-PCR, revealed infrequent and unknown RET fusion genes. The presence of RET rearrangements was associated with a significantly elevated risk to develop iodine refractory disease and lymph node metastases. Of note, significant clinical discrimination was only achievable when taking the FISH results into account; differences would have been missed when using the RT-PCR method only. Increasing evidence of the clinical impact of RET/PTC-positivity may influence the decision on the extent of surgical resection, especially on lymph node dissection, in PTCs.

Novel rearrangements involving the RET gene in papillary thyroid carcinoma.

BACKGROUND: In the field of gene fusions driving tumorigenesis in papillary thyroid carcinoma (PTC), rearrangement of the proto-oncogene RET is the most frequent alteration. Apart from the most common rearrangement of RET to CCDC6, more than 15 partner genes are yet reported. The landscape of RET rearrangements in PTC ("RET-PTC") can notably be enlarged by modern targeted next-generation sequencing, indicating similarities between oncogenic pathways in other cancer types with identical genetic alterations. METHODS: Targeted next-generation sequencing was performed for two cases of BRAF-wild type PTC with confirmation of the results by Sanger sequencing. A "UniProt" database research was performed to assess protein alterations resulting from RET rearrangements. RESULTS: RUFY2-RET and KIAA1468-RET were detected. The fusion genes were not present in normal tissue of the index patients. The rearrangement RUFY2-RET lead to a fusion of the RET tyrosine kinase domain to a RUN domain and a coiled-coil domain. For KIAA1468-RET, a fusion to a LisH domain and two coiled-coil domains resulted. CONCLUSIONS: RUFY2-RET and KIAA1468-RET are novel RET/PTC rearrangements. The fusions were previously described in non-small cell lung cancer. The rearrangement results in a fusion of the RET tyrosine kinase to regulatory domains of RUFY2 and KIAA1468.