1. Differential expression of alphaB-crystallin and Hsp27-1 in anaplastic thyroid carcinomas because of tumor-specific alphaB-crystallin gene (CRYAB) silencing.
- Author
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Mineva I, Gartner W, Hauser P, Kainz A, Löffler M, Wolf G, Oberbauer R, Weissel M, and Wagner L
- Subjects
- Animals, COS Cells, Carcinoma chemistry, Carcinoma metabolism, Cell Line, Tumor, Cloning, Molecular, DNA, Complementary biosynthesis, Down-Regulation, Gene Silencing, Genes, Reporter, Goiter, HSP27 Heat-Shock Proteins, Heat-Shock Proteins analysis, Heat-Shock Proteins metabolism, Humans, Intermediate Filament Proteins analysis, Intermediate Filament Proteins metabolism, Luciferases genetics, Molecular Chaperones, Neoplasm Proteins analysis, Neoplasm Proteins metabolism, Nerve Tissue Proteins analysis, Nerve Tissue Proteins metabolism, Oligonucleotide Array Sequence Analysis, Promoter Regions, Genetic, Protein Kinases analysis, Protein Kinases metabolism, RNA, Messenger metabolism, Repressor Proteins metabolism, Thyroid Neoplasms chemistry, Thyroid Neoplasms metabolism, Tissue Extracts chemistry, Tissue Extracts genetics, Tissue Extracts metabolism, Transcription Factors metabolism, Transfection, alpha-Crystallin B Chain, Carcinoma genetics, Gene Expression Regulation, Neoplastic, Intermediate Filament Proteins genetics, Nerve Tissue Proteins genetics, Protein Kinases genetics, Repressor Proteins genetics, Thyroid Neoplasms genetics, Transcription Factors genetics
- Abstract
Expression of the small heat shock protein alphaB-crystallin in differentiated thyroid tumors has been described recently. In this study, we investigated the molecular mechanisms that affect the expression of alphaB-crystallin in benign goiters (n = 7) and highly malignant anaplastic thyroid carcinomas (ATCs) (n = 3). AlphaB-crystallin expression was compared with that of Hsp27-1. Immunoblot and quantitative real-time (RT) polymerase chain reaction revealed marked downregulation of alphaB-crystallin in all the tested ATCs and the ATC-derived cell line C-643 . In contrast, considerable expression of Hsp27-1 in benign and malignant thyroid tissue was demonstrated. Immunofluorescence analysis revealed no relevant topological differences between benign and malignant thyrocytes in the cytoplasmic staining of both proteins. Consistent and marked downregulation of TFCP2L1 was identified as one of the main mechanisms contributing to CRYAB gene silencing in ATCs. In addition, CRYAB gene promoter methylation seems to occur in distinct ATCs. In silico analysis revealed that the differential expression of alphaB-crystallin and Hsp27-1 results from differences between the alphaB-crystallin and Hsp27-1 promoter fragments (712 bp upstream from the transcriptional start site). Biological activity of the analyzed promoter element is confirmed by its heat shock inducibility. In conclusion, we demonstrate downregulation of alphaB-crystallin expression in highly dedifferentiated ATCs because of a tumor-specific transcription factor pattern. The differential expression of alphaB-crystallin and Hsp27-1 indicates functional differences between both proteins.
- Published
- 2005
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