Proteome analysis in thyroid pathology

Abstract

The incidence of thyroid cancer has continuously increased due to its detection in the preclinical stage. Clinical research in thyroid pathology is focusing on the development of new diagnostic tools to improve the stratification of nodules that have biological, practical and economic consequences on the management of patients. Several clinical questions related to thyroid carcinoma remain open and the use of proteomic research in the hunt for new targets with potential diagnostic applications has an important role in the solutions. Many different proteomic approaches are used to investigate thyroid lesions, including mass spectrometry profiling and imaging technologies. These approaches have been applied to different human tissues (cytological specimens, frozen sections, formalin-fixed paraffin embedded tissue or Tissue Micro Arrays). Moreover, other specimens are used for biomarker discovery, such as cell lines and the secretome. Alternative approaches, such as metabolomics and lipidomics, are also used and integrated within proteomics.

Keywords:

• mass spectrometry
• proteomics
• MS-imaging
• thyroid
• cancer
• diagnosis

Acknowledgments

This study was supported by grants from the MIUR: FIRB 2007 (RBRN07BMCT_11), FAR 2010–2014; from iMODE-CKD (FP7-PEOPLE-2013-ITN) and in part by the COST Action (BM1104) Mass Spectrometry Imaging: New Tools for Healthcare Research.

Financial & competing interests disclosure

The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.

Key issues

• Thyroid cancer is the most frequent endocrine neoplasm and accounts for approximately 4% of all malignancies. Since its incidence in the US has increased by 8.8% in the past 65 years, the diagnosis of early-stage lesions has become of considerable importance.

• Fine needle aspiration is the preferred procedure to investigate thyroid nodules. Despite its high diagnostic performances (Positive predictive value: 97% and Negative predictive value : 92%), undetermined lesions account for approximately 15–30% of fine needle aspiration biopsies. For this reason, additional discriminative elements are required to differentiate benign and malignant entities.

• The widespread genetic investigations, designed to explore and explain cancer pathogenesis, led to the validation of genetic tools (Veracyte and ThyroSeq) useful for diagnostic/prognostic purposes. Moreover, the possible complementary contribution of proteomic approaches in the discovery of novel biomarkers produced preliminary data. The current research follows the application of such techniques upon various kinds of thyroid specimens, both histological (fresh frozen or formalin fixed paraffin-embedded tissues) and cytological (liquid-based cytology, traditional smears). The future employment of serum samples could be also investigated.

• Differential proteomic investigations in thyroid cancer will benefit from the use of label-free relative and absolute quantitation via LC-ESI-MS, with these approaches being able to provide information on greater number of proteins than 2DE.

• MS will gain more importance when validating biomarkers due to the high specificity and sensitivity of detection. This is especially true for the triple quadrupole instruments working in multiple reaction monitoring.

• MS-imaging, thanks to its powerful capability to detect different classes of analytes (small molecules, metabolites, lipids, peptides, proteins) directly in tissue, while maintaining all of the information related to their spatial distribution, will assume a more important role in thyroid studies.

• Molecular information obtained by MS-imaging, or by other techniques such as nuclear magnetic resonance, will be integrated and correlated with the histological images.

• As in microbiology laboratories, where bacteria are identified by MALDI-TOF, such instruments could also be implemented in pathological units to support the diagnosis of undetermined thyroid lesions.