Binding between the NIS promoter region and nuclear extracts from thyroid tissues and correlation with NIS RNA levels. The probe was incubated with nuclear extracts from normal and tumoral thyroid tissues in the presence of 0.2 μg poly(dI-dC) with, and DNA protein complexes were resolved as shown in Fig. 1. Lanes: P, probe alone; N, probe plus nuclear extract from normal thyroid tissue; T, probe plus nuclear extract from cancer thyroid tissue. The levels of the NIS mRNA were assessed by a semi-quantitative RT-PCR based method, as previously described (12) and expressed as mean ± S.E.M. of three different experiments.