Quantification of Core-1 and β-actin mRNA by RT-PCR analysis. A. Determination of the optimal number of amplification cycles for quantification of Core-1 and β-actin mRNA. B. Semiquantitative RT-PCR analysis of Core-1 mRNA expression. For each sample, constant amounts of reverse-transcribed RNA were amplified together with β-actin housekeeping gene. N, triplicates of samples of normal thyroid tissue; T, triplicates of samples of follicular carcinoma. * Values are expressed in arbitrary units.