Analysis of microRNA let-7a and mir-140 Expression Levels Using Laser Capture Microdissected (LCM) Samples of Thyroid Formalin Fixed Paraffin Embedded (FFPE) Tissues
J Li, P Smyth, K Denning, R Flavin, S Aherne, S Guenther, J O'Leary, O Sheils. Trinity College, University of Dublin, Dublin, Ireland; Applied Biosystems, Foster City, CA
Background: Archival formalin-fixed paraffin-embedded (FFPE) tissues represent an abundant source of clinical specimens. Our previous study demonstrated that miRNAs can be detected in FFPE samples and its expression level is reliable in FFPE compared with snap frozen paired samples. Thyroid cancer incidence has increased significantly during the past decades and has become one of the leading cancer types in females. This study is aimed to examine microRNA expression across a spectrum of thyroid diseases including benign, malignant, inflammatory, and hyperplastic.
Design: 182 samples of thyroid FFPE tissues, representing different diseases, were laser captured microdissected and then were undergone RNA extractions using Ambion RecoverAll Total Nucleic Acid Isolation Kit according to manufacturer's protocol. Applied Biosystems TaqMan microRNA (miRNA) assays and protocol were utilised in this study, including two human targets, let-7a and mir-140, and one endogenous control, RNU6B. Nonparametric MannWhitney statistical analysis was performed on the relative quantification (RQ) values using Analyse-it statistical software for Microsoft Excel.
Results: We found Let-7a has a higher expression level in PTC versus Hashmoto's thyroiditis or thyroiditis and mir-140 has a higher expression level in neoplasm and malignancy compared with non-neoplasm, with P value < 0.05.
Conclusions: microRNAs were constantly detected in FFPE tissue samples, and even in the limited available materials, for example in LCM. The different expression levels of let-7a and mir-140 in thyroid disease settings demonstrated these microRNAs could be the potential biomarkers functioning in the thyroid signalling pathways.
Tuesday, March 10, 2009 1:00 PM
Poster Session IV # 82, Tuesday Afternoon