Intracellular control of thyroid hormone in epithelial tumorigenesis

Interest in thyroid hormone (TH) in cancer was first aroused by the demonstration, over a century ago, that breast cancer responded to thyroid extract treatment. This suggested that TH was a key regulator of tumorigenesis. However, the role of TH in the complex process of neoplastic transformation long remained obscure. Interest in the link between TH and cancer was renewed when it became clear that TH receptors and modulators are often altered in cancerous tissues and that modulation of TH might foster cancer cell expansion. Studies in two different epithelial cancers, namely the Basal Cell Carcinoma of the skin and the colon cancer have provided molecular insight the role of TH modulation at intracellular level in tumor formation, thus prompting interest in tissue-specific TH modulation as an anti-tumoral agent. Since then a large body of data has accumulated on this topic and the aim of this brief review is to try to draw together the evidence pointing to a general mechanism by which TH interferes with oncogenic pathways, thus affecting tumoral formation.