Screening of specific changes in mRNAs in thyroid tumors by sequence specific differential display:: Decreased expression of c-fos mRNA in papillary carcinoma

To examine the specific changes in gene expression in thyroid carcinomas, we performed sequence specific-differential display (SS-DD) analysis by using a specific degenerate primer for the superfamily of the small G protein. After subcloning and sequencing analysis, one of the genes that showed decreased expression in thyroid papillary carcinomas was revealed to be the proto-oncogene c-fos. Expression of c-fos mRNA in benign and malignant tissues was examined by reverse transcription-polymerase chain reaction (RT-PCR) and Northern blotting. The expression of c-fos was detected in all twelve normal thyroid tissues, whereas it decreased in thirteen of fifteen papillary carcinomas. These results indicate that the increased expression of c-fos mRNA is not necessarily to be an oncogenic feature of thyroid tumors. Further, its constant expression in normal thyroid tissues may play a role in the maintenance of thyroid function.