One of the most aggressive human malignancies, anaplastic thyroid carcinoma (ATC), has an extremely poor prognosis that may be explained by its genomic instability. We hypothesized that the very rapid cell turnover observed in ATC might accelerate telomere shortening and chromosomal instability associated with tumor cell malignancy. To compare and measure chromosomal aberrations and telomere shortening in the anaplastic thyroid cancer cell line OCUT-1, we applied quantitative fluorescence in situ hybridization (Q-FISH) techniques. In all 15 metaphases studied, telomere length estimates from Q-FISH of chromosomes in ATC were shorter than those of a fibroblast cell line derived from the stroma adjacent to the carcinoma. OCUT-1 cells display several chromosomal abnormalities, but have a near-normal chromosome complement of 46, XX, making it easy to analyze the karyotype. The karyotype showed 50, XX, +7, +11, der(11)t(3;11)(q23;q23)×2, del(12)(p11.2p12), +20, +1mar. We analyzed carefully the abnormalities in karyotype of OCUT-1 associated with telomere shortening on each chromosome and expression of subtelomeres. Telomere lengths in the q-arms of the abnormal chromosome del(12)(p11.2p12) were shorter than the average length in the q-arms of the normal chromosome 12 in OCUT-1. Subtelomeres on the abnormal chromosome der(11)t(3;11)(q23;q23)×2 also showed loss of signals on 11p, but there was no loss of signals in the cytogenetically normal trisomies 7 and 20 or the abnormal chromosome del(12)(p11.2p12). Subtelomeres of 3q had eight signals, one pair remaining in place on 3q and another pair on the abnormal 11p. Our findings suggest that telomere shortening and subtelomere loss are correlated with genetic instability in this anaplastic thyroid carcinoma cell line.

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