Article

CGH alterations in medullary thyroid carcinomas in relation to the RET M918T mutation and clinical outcome

Department of Molecular Medicine, Endocrine Tumor Unit, Karolinska Hospital CMM L8:01, SE-171 76 Stockholm, Sweden.
International Journal of Oncology (Impact Factor: 3.03). 06/2001; 18(6):1219-25. DOI: 10.3892/ijo.18.6.1219
Source: PubMed

ABSTRACT Apart from the RET proto-oncogene (RET) no other genes have been found to be involved in medullary thyroid carcinoma (MTC) tumorigenesis. Germline RET mutations are seen virtually in all familial forms of MTC and somatic RET mutations are often detected in sporadic MTC. In sporadic MTCs the RET gene is mutated in codon 918, where a methionine is substituted to a threonine (M918T). In this study 24 MTCs were analyzed by comparative genomic hybridization (CGH) for chromosomal imbalances. Overall, alterations were detected in approximately 60% of the samples. The most common aberrations were gains on chromosome 19q (29%), 19p (21%), 11c-q12 (12.5%), and 22q (12.5%) and losses on 13q21 (21%) and 3q23-qter (12.5%). Gain of chromosome 11c-q12 was only detected in samples from patients whom died of MTC (p=0.001). These MTCs also harbored the somatic RET M918T mutation and also showed the highest numbers of CGH alterations in the series (p<0.003). Although there was a tendency towards a higher number of CGH imbalances in the tumors with RET M918T mutation, this difference was not significant. The results indicate that MTC is a comparatively genetically stable tumor, and that chromosomal regions 19q, 19p, 13q and 11q may be involved in MTC carcinogenesis.

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    • "It is clear that heterogeneity in chromosomal alterations is present in SMTCs. Several authors have suggested that these CGH imbalances could contribute to outcome or prognosis and that those genetic regions may contain genes associated to the development of SMTC [16-19]. An overexpression of genes involved in proliferation and invasion such as PTN (7q33); ESM1 (5q11), and CEACAM (19q13) could also characterize an aggressive SMTC [20]. "
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    ABSTRACT: Association between DNA alterations and clinical parameters as recurrence, survival or prognosis has been found in a variety of tumors. A clear association between Medullary Thyroid Carcinoma (MTC) and RET oncogene mutation has been accepted. Specifically M918T RET mutation represents the main genetic event in most cases of sporadic MTC (SMTC) and limited chromosomal alterations analyses have been performed. In the present work, a comparative genomic hybridization (CGH) study was performed using DNA from a primary tumor in a M918T RET mutation-positive SMTC patient and from its lymph node metastasis to investigate additional genetic alterations. We studied a patient with 15 years of follow-up and persistence of disease, confirmed by periodical elevated serum calcitonin (CT) levels. Only 3 chromosomal imbalances were identified in the primary tumor, gain of 18p, and loss of 6p and 16p region, whereas 25 chromosomal imbalances were identified in the metastasis (9 gains and 16 losses). The chromosomal changes 6p-, 16p-, 18p + could determine in part the oncogenic phenotype in the primary M918T RET positive tumor and probably related to persistence of high serum CT levels in this patient. The additional chromosomal changes observed could be related to the metastasis phenotype. We suggest that some genes mapped at 6p, 16p and 18p chromosomal regions, could act as genes associated to cancer and could be related to persistent SMTC and good prognosis. VIRTUAL SLIDES: The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1720753793691097.
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    • "Recent studies based on Comparative Genomic Hybridization (CGH) have shown that several chromosome areas can be amplified or lost in MTC suggesting that genetic background might be important in determining the development and/or tumor progression (Ye et al., 2008; Khosla et al., 1991; Mulligan et al., 1993; Koch et al., 2006; Hemmer et al., 1999; Frisk et al., 2001; Marsh et al., 2003). These findings and the evidence that RET mutated gene is amplified in the TT hereditary MTC derived cell line (Huang et al., 2003), arises the question of whether these RET alterations may play a role in the development and/or progression of MTC. "
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    ABSTRACT: About 30% of hereditary Medullary Thyroid Carcinoma (MTC) have been demonstrated to harbour imbalance between mutant and wild-type RET alleles. We studied the RET copy number alterations (RET CNA) in 65 MTC and their correlation with RET mutation and patients' outcome. Fluorescence in situ Hybridization and Real-time PCR revealed RET CNA in 27.7% MTC but only in a variable percentage of cells. In sporadic MTC, RET CNA were represented by chromosome 10 aneuploidy while in hereditary MTC by RET amplification. A significant higher prevalence of RET CNA was observed in RET mutated MTC (P=0.003). RET CNA was also associated to a poorer outcome (P=0.005). However, the multivariate analysis revealed that only RET mutation and advanced clinical stage correlated with the worst outcome. In conclusion, 30% MTC harbour RET CNA in variable percentage of cells suggesting cell heterogeneity. RET CNA can be considered a poor prognostic factor potentiating the poor prognostic role of RET mutation.
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