Quantitative and qualitative differences in protein expression between papillary thyroid carcinoma and normal thyroid tissue.
In order to better understand basic mechanisms of tumor development and identify potential new biomarkers, we have performed difference gel electrophoresis (DIGE) and peptide mass fingerprinting on pooled protein extracts from patients with papillary thyroid carcinoma (PTC) compared with matched normal thyroid tissue. Image analysis of DIGE gels comparing PTC and matched normal thyroid tissue protein indicated that 25% of the protein spots were differentially expressed at a 2.5-fold cutoff and 35% at two-fold. Comparison between two different pools of protein from normal thyroid tissues revealed differential protein expression of only 4% at 2.5-fold and 6% at two-fold cutoff. One hundred ninety-two protein spots were identified by MALDI-TOFMS, representing 90 distinct proteins. Excluding albumin, globins and thyroglobulin, imaging software determined 31 proteins to be differentially expressed at the two-fold (or greater) level. Individual gel comparisons (PTC vs. matched normal) from five patients established that 15/31 (48%) of these proteins exhibited statistically significant differential expression. Previously identified molecular markers in this group of proteins include cathepsin B, cytokeratin 19, and galectin-3. Novel differentially expressed proteins include S100A6, moesin, HSP70 (BiP), peroxiredoxin 2, protein phosphatase 2, selenium binding protein 1, vitamin D binding protein, and proteins involved in mitochondrial function. The use of two-dimensional gel electrophoresis (2DGE) revealed a significantly altered protein mass and/or pI in 10%-15% of proteins, suggesting alternatively spliced forms and other posttranslational modification of proteins revealed by this approach. We confirmed S100A6 as a potentially useful biomarker using immunohistochemical analysis (85% sensitivity and 69% specificity for distinguishing benign from malignant thyroid neoplasms). In summary, proteomic analysis of PTC using DIGE and mass spectrometry has confirmed several known biomarkers, uncovered novel potential biomarkers, and provided insights into global pathophysiologic changes in PTC. Many of the differences observed would not have been detected by genomic or other proteomic approaches.
Brown
Lewis M
LM
Department of Pediatrics, Section of Pulmonary Medicine, The University of Colorado at Denver and Health Sciences Center, Aurora, 80045, USA.
Helmke
Steve M
SM
Hunsucker
Stephen W
SW
Netea-Maier
Romana T
RT
Chiang
Simon A
SA
Heinz
David E
DE
Shroyer
Kenneth R
KR
Duncan
Mark W
MW
Haugen
Bryan R
BR
D000595:Amino Acid Sequence; D014408:Biomarkers, Tumor / Q000032:analysis* / Q000378:metabolism; D002291:Carcinoma, Papillary / Q000175:diagnosis / Q000378:metabolism* / Q000473:pathology; D018797:Cell Cycle Proteins / Q000032:analysis* / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D006801:Humans; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000032:analysis* / Q000378:metabolism; D011379:Prognosis; D040901:Proteomics / Q000379:methods; D000075383:S100 Calcium Binding Protein A6; D009418:S100 Proteins / Q000032:analysis* / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013961:Thyroid Gland / Q000378:metabolism / Q000473:pathology; D013964:Thyroid Neoplasms / Q000175:diagnosis / Q000378:metabolism* / Q000473:pathology
D014408:Biomarkers, Tumor; D018797:Cell Cycle Proteins; D009363:Neoplasm Proteins; D000075383:S100 Calcium Binding Protein A6; D009418:S100 Proteins; C055351:S100A6 protein, human