Expression of wild-type p53 tumor suppressor gene and its possible involvement in the apoptosis of thyroid tumors.

A good prognosis is often achieved in patients who have undergone treatment for human papillary carcinoma of the thyroid. On the assumption that this may be partly attributable to an apoptotic tendency of this special type of tumor, we measured DNA fragmentation, cell death by enzyme-linked immunosorbent assay (ELISA), and the expression of apoptosis-related genes. DNA fragmentation occurred more extensively in malignant tumor cells than in benign thyroid tumors or normal thyroid tissue, as examined by agarose gel electrophoresis and confirmed by the quantitative method using an ELISA kit. Although only expression of the tumor suppressor gene, p53, was increased in the tumor tissue, no expression of other genes, such as Fas, TNF, c-myc, c-fos or bcl-2, was observed in the normal, benign, or malignant tumor tissues, indicating that the roles of these gene functions, if any, were minimal in these tissues. Since p53 is closely related to cellular apoptosis and no point mutation was observed in the transcripts expressed by malignant cells, apoptosis and/or the production of an angiogenesis inhibitor induced by wild-type p53 molecules may be related to the favorable prognosis of patients treated for papillary carcinoma of the thyroid.