In vivo imaging of miR-221 biogenesis in papillary thyroid carcinoma.

PURPOSE: To investigate the overexpression of miR-221 in papillary thyroid carcinoma (PTC), we developed a Gaussia luciferase (Gluc) system regulated by miR-221. PROCEDURES: Quantities of primary or mature miR-221 in normal thyroid cells (HT-ori3) and in PTC (NPA, TPC-1) were measured by quantitative real-time polymerase chain reaction. Cytomegalovirus (CMV)/Gluc-3xPT_miR221, which included three perfect complementary target sequences repeats of miR221 in the 3'-untranslated region of Gluc, was transfected into cells with pre-miR-221 or anti-miR-221 and Gluc activities were then compared in vitro and in vivo. RESULTS: Primary or mature miR-221 were overexpressed in PTC as compared with HT-ori3. In cells transfected with the Gaussia luciferase reporter system (CMV/Gluc-3xPT_miR221), Gluc activities were regulated according to miR-221 levels in vitro and in vivo. CONCLUSIONS: These results suggest that the devised CMV/Gluc-3xPT_miR221 system may be a useful tool for monitoring quantities of endogenous miR-221 in cells or living organisms.