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Mutation analysis of the transforming growth factor-beta type II receptor in human cell lines resistant to growth
F Vincent1, M Nagashima, S Takenoshita
1Laboratory of Human Carcinogenesis, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
Abstract:
The transforming growth factor-beta (TGF-beta) binds the type II TGF-beta growth factor receptor (RII) to inhibit the growth of most epithelial tissues. Most human colon and gastric cancers with microsatellite instability (MI) have frameshift mutations in polynucleotide repeats within the RII coding region; these mutations truncate the receptor protein and disable the serine/threonine kinase to produce TGF-beta resistance. To further investigate the type, frequency and tissue distribution of RII mutations, we selected 24 human cancer cell lines from various tissues which were previously reported to be resistant to the inhibitory effects of TGF-beta. We developed protocols for non-isotopic SSCP analysis of PCR products from genomic DNA samples, and we tested them for microsatellite instability. PCR-SSCP analysis followed by DNA sequencing identified deletion mutations in the exon 3 poly-adenine tract in three colon tumor cell lines: LS174T and SW48 had a single base deletion and LS411 had a two base deletion. Among the 24 previously unreported cell lines, only these three demonstrated microsatellite instability. These and other recent data indicate that RII mutations are essentially confined to colon and gastric cancers with microsatellite instability. The narrow spectrum of tissues containing RII mutations illustrates the complexity of genetic checkpoints in human carcinogenesis.
Insights
Transforming growth factor-beta receptor II (RII) mutations are linked to microsatellite instability (MI) in colon and gastric cancers. These mutations disable the receptor, leading to resistance against TGF-beta
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Transforming growth factor-beta (TGF-beta) signaling is crucial for inhibiting epithelial tissue growth.
- Mutations in the TGF-beta receptor type II (RII) gene, particularly frameshift mutations in microsatellite instability (MI) cancers, lead to TGF-beta resistance.
- Understanding the spectrum of RII mutations is key to understanding cancer development.
Purpose of the Study:
- To investigate the type, frequency, and tissue distribution of RII mutations in cancer cell lines.
- To identify RII mutations in a panel of 24 human cancer cell lines resistant to TGF-beta.
- To correlate RII mutations with microsatellite instability.
Main Methods:
- Developed non-isotopic Single-Strand Conformation Polymorphism (SSCP) analysis for PCR products from genomic DNA.
- Tested 24 human cancer cell lines for microsatellite instability.
- Utilized PCR-SSCP and DNA sequencing to identify mutations in the RII gene.
Main Results:
- Deletion mutations in the exon 3 poly-adenine tract of RII were identified in three colon tumor cell lines (LS174T, SW48, LS411).
- LS174T and SW48 showed a single base deletion, while LS411 had a two base deletion.
- Only these three cell lines exhibited microsatellite instability among the 24 tested, indicating a strong association.
Conclusions:
- RII mutations are primarily found in colon and gastric cancers characterized by microsatellite instability.
- The specific tissue confinement of RII mutations highlights the intricate genetic checkpoints in human carcinogenesis.
- These findings reinforce the role of RII inactivation in specific cancer types with MI.