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 trea tment 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 en zyme-linked immunosorbent assay (ELISA), and the expression of apoptos is related genes. DNA fragmentation occurred more extensively in malig nant tumor cells than in benign thyroid tumors or normal thyroid tissu e, as examined by agarose gel electrophoresis and confirmed by the qua ntitative method using an ELISA kit. Although only expression of the t umor suppressor gene, p53, was increased in the tumor tissue, no expre ssion of other genes, such as Fas, TNF, c-myc, c-fos or bcl-2, was obs erved in the normal, benign, or malignant tumor tissues, indicating th at the roles of these gene functions, if any, were minimal in these ti ssues. 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.