Gene Expression Profiles in Archival Thyroid Carcinoma Using Pre-amplification RT-PCR, Immunohistochemistry and MicroRNA Expression Analysis
K Denning, P Smyth, R Flavin, S Finn, S Russell, J Li, S Aherne, E Conlon, J O'Leary, O Sheils. Trinity College Dublin, Dublin, Ireland
Background: Thyroid cancer is the most frequently occurring endocrine malignancy, with world wide thyroid cancer incidence rates increasing year after year. Furthermore thyroid nodules are a common occurrence and distinguishing benign specimens from malignant can be problematic. The development of a robust molecular expression signature encompassing transcriptomic, protein and microRNA expression analysis would greatly aid in the diagnosis of thyroid malignancy.
Design: Two hundred and five formalin fixed paraffin embedded (FFPE) thyroid samples were laser capture microdissected and a novel pre-amplification technique was used to facilitate gene expression analysis using TaqMan Q-RT-PCR of a panel of 5 targets including MMP11, BAX, APOE, TOP2A and LYN plus endogenous control. A tissue microarray (TMA) was constructed using the same two hundred and five samples and immunohistochemical analysis was carried out for MMP11, BAX, APOE, TOP2A and LYN. Expression of microRNA let-7a was analysed in one hundred and four FFPE thyroid tissue samples using a novel in situ (ISH) hybridisation technique for miRNA expression in archival samples.
Results: All five targets were found to significantly (p < 0.05) discriminate a range of benign from malignant thyroid disease states at mRNA and protein expression levels. Four out of the five targets were also shown to significantly differentiate, at the gene and protein level, corresponding groups of matched samples. Of these four targets, MMP11 and APOE, which were over-expressed in malignant tissues, were found to be targets of let-7a using miRNA target prediction databases. Expression of let-7a was significantly (p < 0.05) down-regulated in all malignant and neoplastic groups, and subsequently was also found capable of discriminating benign from malignant thyroid disease.
Conclusions: This robust panel of molecular markers could prove extremely useful in assisting the classification and diagnosis of thyroid malignancy.
Tuesday, March 10, 2009 1:00 PM
Poster Session IV # 78, Tuesday Afternoon