Differential protein expression profiles of cyst fluid from papillary thyroid carcinoma and benign thyroid lesions.

Andrii Dinets,Hanna Kjellin,Anders Höög,Maria Pernemalm,Catharina Larsson,Janne Lehtiö,C Christofer Juhlin,Anastasios Sofiadis,Jan Zedenius,Vitalijs Sviatoha,Jacques Emile Dumont

doi:10.1371/journal.pone.0126472

Abstract

Cystic papillary thyroid carcinoma (cPTC) is a subgroup of PTC presenting a diagnostic challenge at fine needle aspiration biopsy (FNAB). To further investigate this entity we aimed to characterize protein profiles of cyst fluids from cPTC and benign thyroid cystic lesions. In total, 20 cPTCs and 56 benign thyroid cystic lesions were studied. Profiling by liquid chromatography tandem mass spectrometry (LC-MS/MS) was performed on cyst fluids from a subset of cases after depletion, and selected proteins were further analyzed by Western blot (WB), immunohistochemistry (IHC) and enzyme-linked immunosorbent assay (ELISA). A total of 1,581 proteins were detected in cyst fluids, of which 841 were quantified in all samples using LC-MS/MS. Proteins with different expression levels between cPTCs and benign lesions were identified by univariate analysis (41 proteins) and multivariate analysis (59 proteins in an orthogonal partial least squares model). WB analyses of cyst fluid and IHC on corresponding tissue samples confirmed a significant up-regulation of cytokeratin 19 (CK-19/CYFRA 21-1) and S100A13 in cPTC vs. benign lesions. These findings were further confirmed by ELISA in an extended material of non-depleted cyst fluids from cPTCs (n = 17) and benign lesions (n = 55) (p<0.05). Applying a cut-off at >55 ng/ml for CK-19 resulted in 82% specificity and sensitivity. For S100A13 a cut-off at >230 pg/ml revealed a 94% sensitivity, but only 35% specificity. This is the first comprehensive catalogue of the protein content in fluid from thyroid cysts. The up-regulations of CK-19 and S100A13 suggest their possible use in FNAB based preoperative diagnostics of cystic thyroid lesions.

Highlights

Papillary thyroid carcinoma (PTC) is the most common form of thyroid malignancy
Twenty of these 227 cases were classified as cystic variant of PTC (cPTC) giving a proportion of 9% cPTCs in this study cohort (Table 1)
A preoperative diagnosis of PTC was established in 8 cases (47%), whereas 9 cPTC cases (53%) had suspicious or benign fine needle aspiration biopsy (FNAB) results illustrating the diagnostic challenges for preoperative identification of cPTC (Table 1)

Summary

Introduction

Papillary thyroid carcinoma (PTC) is the most common form of thyroid malignancy. The tumor is usually well-differentiated and is characterized by typical cytological and histopathological features [1]. The diagnosis is challenging, since the fine needle aspiration biopsy (FNAB) of a cystic thyroid nodule usually results in a relatively large volume of cyst fluid, but may contain insufficient amounts of representative tumor cells. This may lead to cytological reports in which malignancy is not recognized [4]. The most frequently used immunohistochemical markers to confirm a PTC diagnosis are cytokeratin 19 (CK-19) and Hector Battifora mesothelial antigen-1 (HBME-1) [6, 7] These proteins are commonly up-regulated in PTC, they can be expressed in benign thyroid lesions, leading to difficulties in establishing the preoperative diagnosis [8]. Identification of novel diagnostic markers to distinguish cPTC from benign cystic thyroid lesions is warranted and could be based on proteinbased screening approaches

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