Impaired transforming growth factor signalling in Barrett's carcinogenesis due to frequent SMAD4 inactivation
| Autor: | Yinghui Huang, Suet-Feung Chin, Tanja Kranjac, Pierre Lao-Sirieix, Rebecca C. Fitzgerald, Benjamin A. Onwuegbusi, Ian G. Mills, Alan Aitchison, Carlos Caldas |
|---|---|
| Rok vydání: | 2006 |
| Předmět: |
Esophageal Neoplasms
Molecular Sequence Data Bisulfite sequencing Adenocarcinoma Biology Transfection medicine.disease_cause Barrett Esophagus Downregulation and upregulation Transforming Growth Factor beta Tumor Cells Cultured medicine Humans Prospective Studies RNA Messenger RNA Neoplasm Cell Proliferation Smad4 Protein Genome Base Sequence Reverse Transcriptase Polymerase Chain Reaction Cell growth Gastroenterology Methylation Transforming growth factor beta DNA Methylation Molecular biology digestive system diseases Neoplasm Proteins Gene Expression Regulation Neoplastic Oesophagus Cell Transformation Neoplastic DNA methylation Disease Progression Cancer research biology.protein Carcinogenesis Precancerous Conditions Signal Transduction Transforming growth factor |
| Zdroj: | Gut. 55:764-774 |
| ISSN: | 0017-5749 |
| DOI: | 10.1136/gut.2005.076430 |
| Popis: | Transforming growth factor beta (TGF-beta) is frequently involved in gastrointestinal carcinogenesis although its contribution to oesophageal adenocarcinoma (AC) and its precursor Barrett's oesophageal epithelium (BE) metaplasia are unclear.Expression of TGF-beta signalling components was assessed by reverse transcription-polymerase chain reaction (PCR), western blot, and immunohistochemistry in oesophageal endoscopic biopsies and cell lines. Genomic alterations in SMAD4 were characterised by fluorescence in situ hybridisation, methylation specific PCR, and sequencing. Functional integrity of TGF-beta signalling was assessed by characterisation of p21 and proliferation status. Smad4 negative BIC-1 cells were transiently transfected with smad4 and TGF-beta responsiveness evaluated.smad4 mRNA expression was progressively reduced in the metaplasia-dysplasia-adenocarcinoma sequence (p0.01). A quarter of AC samples displayed an abnormal Smad4 protein isoform, with no corresponding changes in gene sequence or organisation. Methylation of smad4 has not been described previously but we found promoter methylation in 70% of primary AC samples. In 6/8 oesophageal cell lines, chromosomal rearrangements affected the smad4 locus. Lack of smad4 expression in BIC-1 cells occurred secondary to loss of one copy and extensive deletion of the second allele's promoter region. TGF-beta dependent induction of p21 and downregulation of minichromosome maintenance protein 2 was lost in80% of BE and AC. TGF-beta failed to inhibit proliferation in 5/8 oesophageal cell lines. In BIC-1, the antiproliferative response was restored following transient transfection of smad4 cDNA.In BE carcinogenesis, downregulation of Smad4 occurs due to several different mechanisms, including methylation, deletion, and protein modification. Frequent alterations in TGF-beta signalling lead to a functionally significant impairment of TGF-beta mediated growth suppression. |
| Databáze: | OpenAIRE |
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