MicroRNA Analysis in Common Thyroid Neoplasms as an Aid for Diagnostic Evaluation
Y Li, GA Barkan, S Alkan. Loyola University Medical Center, Maywood, IL
Background: Although diagnosis of the majority of thyroid neoplasms is straightforward by histological evaluation, the differential diagnosis of a number of lesions such as follicular variant of papillary thyroid carcinoma (FVPTC), follicular carcinoma (FC) and follicular adenoma (FA), remain difficult due to morphologic similarity and lack of diagnostic ancillary studies. Studies found a group of small RNA molecules (22 nucleotides long), namely microRNA (miR) derived from non-coding sequence of RNA, bind to specific mRNA targets to modulate translation or RNA degradation process, and important to tumor growth. It has been also reported recently that overexpression of miR-221, -222, and -181b were detected in thyroid papillary carcinomas (PTC) using real-time PCR (RT-PCR) technique and freshly frozen surgical specimens.
Design: Based on previous studies of miR extraction from paraffin-embedded samples, we quantified miR-221 and -222 by RT-PCR (Taqman assay) on miR isolated from paraffin-embedded thyroid specimens, and extended the analysis to a broader category of thyroid neoplasms including PTC, FVPTC, FC and FA, as well as normal thyroid tissue. miR-RNU is used as an internal control for calculation of Ct (cycle threshold) values. The expression of miR-221 and -222 in normal and several thyroid neoplasms are illustrated in the following table.
t-test was used for statistical analysis. *** p<0.0005, * p<0.05
|Ct (miR-221)||-0.18 0.83||-3.96 1.15***||-2.05 2.5*||-2.20 2.24*|
|Ct (miR-222)||-1.11 0.71||-4.81 1.18***||-2.85 2.70||-2.34 2.05|
Results: Our results showed miR-221 is significantly overexpressed in PTC compared to normal thyroid, and slightly overexpressed in FVPTC and FC. miR-222 expression level is also highly up-regulated in PTC, but did not show a statistical significance in FVPTC or FC.
Conclusions: In conclusion, miR-221 and -222 are highly sensitive diagnostic markers of PTC, but are less sensitive to FVPTC and FC, and may be helpful in understanding the biology as well as aid in evaluation of thyroid neoplasms.
Monday, March 9, 2009 9:30 AM
Poster Session I Stowell-Orbison/Autopsy Award # 86, Monday Morning