Biologic and cytogenetic characterization of three human medullary thyroid carcinomas in culture.

Neuroendocrine features and cytogenetic abnormalities of one continuous cell line (MTC-SK) and two long-term cultures (GER, STAH) derived from three sporadic cases of human medullary thyroid carcinomas (MTCs) were studied. Specific neuroendocrine markers (NSE, chromogranins, calcitonin, calcitonin gene-related peptide) were identified by electron microscopy and immunocytochemistry. In situ hybridochemistry and Northern blot analysis confirmed endocrine activity. Cytogenetic studies of the cell line MTC-SK revealed three consistent marker chromosomes, t(3;10), 11p+, and 22p+. Cells of long-term cultures GER and STAH exhibited a consistent translocation t(2;18), a trisomy 7, and two consistent marker chromosomes der3 and 5p+, respectively. Recently, we have isolated 12 stable clones of this MTC-SK cell line, which showed two different growth patterns. Quantitative measurement of mitotic activity flow cytometry and semiquantitative analysis of AgNOR-, Ki67-, and Cyclin/PCNA-(immuno)reactivity showed different DNA composition and duplication rates, indicating at least two subpopulations. Some of our clones developed a new consistent marker (i.e., an unbalanced translocation between mar11p+ and 1q). However, no correlations between chromosome findings, growth rate, and neuroendocrine markers were observed.