DIFFERENTIAL DISPLAY IN PRIMARY AND METASTATIC MEDULLARY-THYROID CARCINOMA

Despite recent advances in the understanding of the role of the RET pr oto oncogene in the development of familial and approximately 30% of s poradic medullary thyroid carcinomas (MTC), little is known about othe r genetic events that modify the course and outcome of the disease. We compared the expression of genes in intrathyroidal MTCs to autologous local lymph node metastases by means of mRNA differential display (DD RT-PCR). This is the first report of differential display using surgic al specimens of a primary cancer and its metastases. Total RNA was ext racted from tumor tissue of two patients with MTC associated with mult iple endocrine neoplasia (MEN 2B) and sporadic MTC, respectively. Foll owing reverse transcription (RT), the products were PCR-amplified and separated on a denaturating polyacrylamide gel. RT-PCR. products demon strating differential expression were reamplified and used as probes f or Northern blot analysis. Six fragments for which differential expres sion was confirmed were cloned and sequenced. Resultant sequences were tested for homology to sequences in public data bases, and two novel MTC derived fragments (MDF-1, MDF-2) were identified. Sensitivity of t he method was confirmed by identification of a sequence encoding the c alcitonin precursor flanking peptide which Is expressed almost exclusi vely in MTC and normal thyroid C cells, Overexpression of the ribosoma l genes S3a and PO was found in the metastases. Recent reports suggest that components of the translational apparatus act as regulatory medi ators of growth, proliferation, and neoplastic change. The altered exp ression of ribosomal proteins and gene products encoded by MDF-1 or MD F-2 may play an important role in the progression and metastatic sprea d of MTC. (C) 1997 Academic Press.