Differential expression of alphaB-crystallin and Hsp27-1 in anaplastic thyroid carcinomas because of tumor-specific alphaB-crystallin gene (CRYAB) silencing.
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.
Mineva
Ivelina
I
Department of Medicine III, Medical University of Vienna, Waehringer Guertel 18-20, Vienna A-1090, Austria.
Gartner
Wolfgang
W
Hauser
Peter
P
Kainz
Alexander
A
Löffler
Michael
M
Wolf
Gerhard
G
Oberbauer
Rainer
R
Weissel
Michael
M
Wagner
Ludwig
L
D000818:Animals; D019556:COS Cells; D002277:Carcinoma / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000096:biosynthesis; D015536:Down-Regulation; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D017930:Genes, Reporter; D006042:Goiter; D055551:HSP27 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000032:analysis / Q000378:metabolism; D006801:Humans; D007381:Intermediate Filament Proteins / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D008156:Luciferases / Q000235:genetics; D018832:Molecular Chaperones; D009363:Neoplasm Proteins / Q000032:analysis / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic; D011494:Protein Kinases / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D013964:Thyroid Neoplasms / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D014020:Tissue Extracts / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D014162:Transfection; D038203:alpha-Crystallin B Chain
C059215:CRYAB protein, human; D018076:DNA, Complementary; D055551:HSP27 Heat-Shock Proteins; C057725:HSPB1 protein, human; D006360:Heat-Shock Proteins; D007381:Intermediate Filament Proteins; D018832:Molecular Chaperones; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D012097:Repressor Proteins; C428128:TFCP2L1 protein, human; D014020:Tissue Extracts; D014157:Transcription Factors; D038203:alpha-Crystallin B Chain; D008156:Luciferases; D011494:Protein Kinases