Xiabin Lan

BACKGROUND: Central lymph node metastasis (CLNM) is common in papillary thyroid carcinoma (PTC). Prophylactic central lymph node dissection (PCLND) for patients with clinically negative central compartment lymph nodes (CN0) remains controversial. The phrase "clinically negative" is used to indicate that patients exhibited no clinical evidence of CLNM by ultrasonography (US) or computerized tomography (CT) preoperatively. In this study, we analyze the risk factors for CLNM in CN0 patients. METHODS: The PUBMED and SCIE databases were systematically searched for works published through January 31, 2015. All of the patients included in this study underwent thyroidectomy+PCLND. Revman 5.3 software was used to analyze the data. RESULTS: Twenty studies and 9084 patients were included in this meta-analysis. The following variables were associated with an increased risk of CLNM in CN0 patients: age < 45 years (OR = 1.59, 95% CI = 1.42-1.78, p<0.00001), male sex (OR = 1.95, 95% CI = 1.63-2.32, p<0.00001), multifocality (OR = 1.43, 95% CI = 1.22-1.67, p<0.00001), tumor size > 2 cm for PTC patients (OR = 2.98, 95% CI 2.08-4.28, p<0.00001) or tumor size > 0.5 cm for papillary thyroid microcarcinoma (PTMC) patients (OR = 2.30, 95% CI = 1.71-3.09, p<0.00001), location of the primary tumor in the central area and low pole (OR = 1.86, 95% CI = 1.48-2.33, p<0.00001), lymphovascular invasion (OR = 4.35, 95% CI = 2.24-8.46, p<0.0001), extrathyroidal extension (OR = 2.27, 95% CI = 1.76-2.94, p<0.00001), and capsular invasion (OR = 1.72, 95% CI = 1.39-2.41, p<0.00001). PTC (tumor size > 1 cm) exhibited a higher risk factor associated with CLNM than PTMC (tumor size < 1 cm) (OR = 2.83, 95% CI = 2.15-3.72, p<0.00001). Bilateral tumors (OR = 1.21, 95% CI = 0.92-1.58, p = 0.17) and lymphocytic thyroiditis (OR = 0.88, 95% CI = 0.71-1.09, p = 0.25) had no association with CLNM in CN0 patients. CONCLUSIONS: Our systematic review identified several clinical features associated with CLNM in CN0 patients, including age, sex, multifocality, size, location, lymphovascular invasion, capsular invasion, and extrathyroidal extension. These factors should guide the application of PCLND in CN0 patients.

Nuclear paraspeckle assembly transcript 1 (NEAT1), a long non-coding RNA (lncRNA), is a core structural component of paraspeckles and is essential for paraspeckle formation. NEAT1 comprises two different isoforms: NEAT1_1 (3.7 kb) and NEAT1_2 (23 kb). Recently, NEAT1 has been shown to have oncogenic roles and to facilitate tumorigenesis in various human cancers. However, the function of NEAT1 in papillary thyroid cancer (PTC) is not well understood. The relative expression levels of NEAT1_2, ATPase family AAA domain-containing protein 2 (ATAD2), and microRNA-106b-5p (miR-106b-5p) were assessed via quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR). Four PTC cell lines were used to detect the relative expression of NEAT1_2. The effects of NEAT1_2 on PTC cells were studied by RNA interference approaches in vitro. The effects of NEAT1_2 on downstream proteins were detected by western blotting. The underlying mechanism was clarified by a rescue experiment, and three dual-luciferase reporter assays. NEAT1_2 expression was markedly increased in PTC tissues and the PTC cell lines (K1 and TPC1). The relative expression level of NEAT1_2 was positively associated with TNM stage and tumor size. NEAT1_2 knockdown led to a significant inhibition of growth and metastasis, and induced apoptosis in PTC cells. Knockdown of NEAT1_2 significantly inhibited malignant biological behavior by downregulating the oncogene ATAD2. In addition, NEAT1_2 could act as a competing endogenous RNA to regulate the expression of ATAD2 through downregulating miR-106b-5p. Taken together, our results indicated that NEAT1_2 is overexpressed in PTC. NEAT1_2 could function as a competing endogenous RNA to regulate ATAD2 expression by sponging miR-106b-5p in PTC. Targeting NEAT1_2 could be a promising therapeutic strategy for patients with PTC.

Papillary thyroid carcinoma (PTC) is the most common malignancy of the thyroid gland, with a relatively high cure rate. Distant metastasis (DM) of PTC is uncommon, but when it occurs, it significantly decreases the survival of PTC patients. The molecular mechanisms of DM in PTC have not been systematically studied. We performed whole exome sequencing and GeneseeqPrime (425 genes) panel sequencing of the primary tumor, plasma and matched white blood cell samples from 20 PTC with DM and 46 PTC without DM. We identified somatic mutations, gene fusions and copy number alterations and analyzed their relationships with DM of PTC. BRAF-V600E was identified in 73% of PTC, followed by RET fusions (14%) in a mutually exclusive manner (P < 0.0001). We found that gene fusions (RET, ALK or NTRK1) (P < 0.01) and chromosome 22q loss (P < 0.01) were independently associated with DM in both univariate and multivariate analyses. A nomogram model consisting of chromosome 22q loss, gene fusions and three clinical variables was built for predicting DM in PTC (C-index = 0.89). The plasma circulating tumor DNA (ctDNA) detection rate in PTC was only 38.9%; however, it was significantly associated with the metastatic status (P = 0.04), tumor size (P = 0.001) and invasiveness (P = 0.01). In conclusion, gene fusions and chromosome 22q loss were independently associated with DM in PTC and could serve as molecular biomarkers for predicting DM. The ctDNA detection rate was low in non-DM PTC but significantly higher in PTC with DM.