The RET/PTC3 oncogene: metastatic solid-type papillary carcinomas in murine thyroids.

Our research goal is to better understand the mechanisms controlling the initiation and progression of thyroid diseases. One such disease, papillary thyroid carcinoma (PTC), is the leading endocrine malignancy in the United States. Recently, a family of related fusion proteins, RET/PTC1-5, has been implicated in the early stages of PTC. Although all five members of this family have the c-RET proto-oncogene kinase domain in their COOH terminus, little is known about how these genes alter follicular cell biology. Consequently, to answer questions related to the mechanism of the RET/PTC fusion protein action, we have devised a molecular genetic strategy to study PTC using a mouse model of thyroid disease. A new member of this fusion oncogene family, RET/PTC3, which has been implicated in more cases of solid tumor carcinoma (79%) than PTC1 or PTC2 and predominates (80%) in radiation-induced thyroid cancer of children, was investigated in our study. We have generated transgenic mice expressing human RET/PTC3 exclusively in the thyroid. These mice develop thyroid hyperplasia, solid tumor variants of papillary carcinoma and metastatic cancer. This new transgenic line will be useful in deciphering the molecular and biological mechanisms that cause PTC and histological variations in humans.