Peptide Imaging in Follicular and Classic Variant of Papillary Thyroid Carcinoma: An Application of MALDI-Imaging Mass Spectrometry 1Yasemin 1Department
Ucal,
2Cavit
Kerem Kayhan,
2Fatma
Tokat,
3Mete
Düren,
1Ümit
İnce,
1Aysel
Ozpinar
of Medical Biochemistry, School of Medicine, University of Acibadem, Istanbul, TR , 2Pathology, Acibadem University Medical School, Istanbul, Turkey, 3General Surgery, Acibadem Maslak Hospital, Istanbul, Turkey
Introduction
Experimental Design and Methods
Fine Needle Aspiration Biopsy (FNAB), a gold standard method in histopathological diagnosis of thyroid nodules, can be insufficient in the characterization and diagnosis of the follicular variant of papillary thyroid carcinoma (FVPTC).
The experimental procedure is outlined in Figure 3.
In some cases, when no certain diagnosis is made for FVPTC there is a need for a second surgical operation to remove the other thyroid lobe.
MALDI-TOF/TOF mass spectrometry (Bruker Daltonics GmbH, Bremen, Germany).
In this work, we analyzed peptides in Follicular and Classic Variants (CV) of Papilary Thyroid Carcinoma (PTC), using Matrix-assisted laser desorption/ionization-Imaging Mass Spectrometry (MALDI)-Imaging Mass Spectrometry (IMS) as it requires no homogenization prior to analysis and enables the localization of molecular species along with histology A
B
C
Mass spectra have been acquired using Autoflex III Smartbeam
All acquired spectra range from m/z 600 to 2000, with a raster of 200 micrometers. Samples were stained with H&E for investigating MS data with corresponding histological features.
Aim Figure 1: Hematoxylin and Eosin (H&E) staining of (a) FVPTC and (b) CVPTC. The green circles represent the tumor regions of the tissue sections.
Figure 2: Exemplary PTC tissue. A: 3 um tissue section B: Region of Interest to be analyzed by MALDI-IMS C: Representative peptide image after MALDI-IMS
1- To distinguish the peptide pattern differences in FVPTC and CVPTC.
Figure 2: Experimental outlinee for MALDI-IMS
Evaluation of the results was based on single peptide localizations and hierarchical clustering analyses in correlation with histological features.
Results and Conclusion • In this preliminary work, up to 250 monoisotopic peaks were detected in the
• Peptide pattern differences were observed between FVPTC and CVPTC (Figure 6).
mass spectra of both CVPTC and FVPTC (Figure 4 and 5). • These identified peptides were correlated with histological features of the tissues, which were emphasized by tissue-specific results of hierarchical cluster analysis (Figure 7). • Previously identified and calculated peptides were used as a basis for evaluating the acquired data. Based on this evaluation, the accuracy of the identified peptides
Figure 5: Acquired spectra from tumor regions of different PTC tissues
Figure 6: Peptide pattern differences observed in PVPTC and CVPTC. green: FVPTC, red: CVPTC
Figure 7: Observed peptide patterns highly correlated with the histological features of the tissue. Hierarchical analysis demonstrated that the peptides grouped in pink were localized in the tumor region. The peptides grouped in purple were localized in the benign region.
were determined with less than 100 ppm.
Figure 4: Different m/z values localized in tumor regions were used for further analysis.
The work presented here demonstrates the capability of MALDI-IMS to accurately classify peptides from CVPTC and FVPTC. It provides a broad knowledge about IMS studies in thyroid pathology and can be further extended to an increased size of sample set with high spatial resolution for biomarker discovery. This work was supported by the Scientific and technical Research Council of Turkey (TUBITAK) under Grant N0: 214S012, Contact Email:
[email protected]
