The results from Kim et al. [66], showing that transient overexpression of Wnt-1 or β-catenin in FRTL-5 cells decreased thyroperoxidase (TPO) mRNA, and suppressed TPO-promoter activity, corroborate a putative role for β-catenin activation in loss of differentiation of thyroid cancer cells. The gene discussed is TPO; the disease is thyroid cancer.