Endocrine Abstracts

Background: Differentiated Thyroid Carcinomas (DTC) represent more than 90% of thyroid tumors with good prognosis and long survival. Currently, patients with intermediate/high risk nodule as assessed by cytological staging may undergo surgery. According to ATA 2017 guidelines, all patients presenting thyroid nodules with suspicious ultrasound features (hypoechoic pattern, irregular margins, microcalcifications, etc.) and cytopathology TIR3B, TIR4 or TIR5 according to 2014-SIAPEC classification may undergo to surgery. However, not all nodules are malignant: about 25–30% of TIR3B, 50–80% of TIR4 and 95–99% of TIR5 are tumor, as assessed only upon thyroidectomy. Although it has been well established that lncRNAs (long non-coding RNA transcripts) play a fundamental role in cancer biology, knowledge about the specific role of these transcripts in the initiation and progression of DTC is still poorly understood.

Aim: The aim of this study is to identify a molecular profile based on lncRNAs expression that may discriminate between benign and malignant nodules.

Methods: A cohort of 50 patients, male to female ratio 1:5 was enrolled at the Endocrinology and Metabolism Diseases Unit, Fondazione Policlinico Gemelli, Rome Italy. Inclusion criteria: thyroid nodules more than 1 cm with suspicious ultrasound characteristics. Gene expression analysis was performed using Droplet Digital PCR (ddPCR) on the following biological samples: i) cells from Fine Needle Aspiration (FNA) biopsy, ii) residual cell samples from FNA prepared for cytology (FNA-ThP) and iii) fresh thyroid tissue explanted after surgery.

Results: A panel of transcripts were first analyzed by ddPCR on fresh DTC tissue: the three thyroid-specific genes (TG, TPO and NIS), six cancer-associated lncRNAs (MALAT1, NEAT1, HOTAIR, H19, PVT1, MEG3) and two housekeeping genes (GAPDH and P0). According to their higher expression in DTC, TG and MALAT1 were selected as markers for thyroid specificity and malignant phenotype, respectively. Next, gene expression by ddPCR was analyzed in both FNA and FNA-ThP samples after RNA extraction (Single Cells Shot, Biorad), reverse transcription (High Capacity kit, Applied Biosystems) and preAmp step (EvaGreen Master Mix, Biorad). As preliminary results, 6 out 14 patients (12 TIR2 and 2 TIR3) appear to express MALAT1 20-200 fold higher that TG or P0, with the following distribution: 2/2 TIR3 patients and 4/12 TIR2. Of note, 2/4 TIR2 were large thyroid nodules (3–4 cm).

Conclusion: In conclusion, characterization of selected lncRNAs in Fine Needle Aspiration biopsies may represent a novel diagnostic approach potentially contributing to take the final decision to proceed or not with surgery.