Stem Cell Features Segregate to the Peripheral Compartment of High-Grade Follicular Thyroid Carcinomas
H Elhassan, A Blanes, J Moorhead, SJ Diaz-Cano. King's College Hospital, London, United Kingdom; University of Malaga School of Medicine, Malaga, Spain
Background: Previous studies have looked at the expression of some stem cell markers in the thyroid, but no topographical analysis is available. We aim to assess topographically stem cell markers in differentiated follicular cell thyroid proliferative lesions by gene expression and immunohistochemistry.
Design: We selected 15 hyperplastic nodules, 22 adenomas, 14 minimally-invasive carcinomas, 24 widely-invasive carcinomas, 15 papillary carcinomas and 13 anaplastic carcinomas (WHO criteria). Total RNA was extracted from normal and neoplastic tissues (peripheral and internal compartments) by hot acidic phenol, DNase I-treated, phenol extracted and cleaned (RNeasy columns). T7-(dT24) oligomer was used for priming the first-strand cDNA synthesis and the resultant cDNA was phenol/chloroform extracted, and used as template for cRNA synthesis (T7 MegaScript In Vitro Transcription Kit). The cRNA was fragmented, Cy3- and Cy5-labeled, and hybridized to the human GeneChip U133A Array noncompetitively. Cross-validated gene expression analyses were performed (expression factor2, significance0.01), and variables studied regarding the histological diagnosis and stem cell markers. Telomerase immunostaining and FISH-PNA of telomere were also analyzed. Significant variables were evaluated immunohistochemically.
Results: Statistically significant topographic differences were observed for CD44 for PTC and FTA, being significantly higher for widely invasive FTC in both peripheral and internal compartments. CD44 expression correlated positively with IL18 receptor accessory protein, PAX8, MAPK10, AKT3, and ELK3, and negatively with MCM4, Histone deacetylase 2, Transcription factor 3, Chromodomain helicase DNA binding protein. Using these variables, 96.6% of follicular neoplasms and 54% PTC were correctly classified. Telomerase was significantly higher in internal compartments (p<0.001) and in malignant lesions (p<0.001), correlating with PNA-FISH detectable telomeres in internal compartments. PNA-FISH detectable telomere in more than 20% of peripheral tumor cells was observed in high-grade lesions (widely-invasive and anaplastic carcinomas).
Conclusions: Stem cell markers showed higher expression in peripheral compartments of follicular cell thyroid carcinomas, controlling the MAPK-ELK and WNT pathways (MAPK10, TCF3) and cell replication (MCM4, HDAC2, helicase). Maintained stem cell features in peripheral follicular cells would contribute to higher metastatic potential.
Tuesday, March 10, 2009 9:00 AM
Platform Session: Section H1, Tuesday Morning