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Frequency of Smad gene mutations in human cancers
G J Riggins1, K W Kinzler, B Vogelstein
1The Johns Hopkins Oncology Center, Baltimore, Maryland 21231, USA.
Abstract:
Much excitement has recently been generated by the discovery of the Smad genes, encoding proteins that transduce signals from the transforming growth factor beta family of cytokines. Here, we report the completion of cloning of the six known human Smads, providing novel sequences for Smad5 and Smad6. Previously, Smad4 and Smad2 were shown to be mutated in human cancers. However, analysis of the other four Smad genes revealed no mutations in a total of 167 tumors, including those from colon, breast, lung, and pancreas. These results suggest that the various Smad genes have different functions and demonstrate that mutations in these four genes do not, in general, account for the widespread resistance to transforming growth factor beta that is found in human tumors.
Insights
The Smad genes are crucial for transforming growth factor beta signaling. This study found no mutations in four key Smad genes across 167 human tumors, suggesting alternative mechanisms for cancer's resistance to this pathway.
Area of Science:
- Molecular Biology
- Cancer Genetics
- Cell Signaling
Background:
- The Smad gene family encodes proteins essential for signal transduction from the transforming growth factor beta (TGF-β) cytokine superfamily.
- Mutations in Smad4 and Smad2 have been previously identified in human cancers, highlighting their role in tumorigenesis.
- Understanding the role of other Smad genes in cancer is crucial for comprehending TGF-β pathway dysregulation.
Purpose of the Study:
- To complete the cloning of all six known human Smad genes, including novel sequences for Smad5 and Smad6.
- To investigate the mutational status of the four Smad genes (excluding Smad4 and Smad2) in a comprehensive panel of human tumors.
- To determine if mutations in these Smad genes contribute to the observed resistance to TGF-β signaling in various cancers.
Main Methods:
- Full-length cDNA cloning of the six human Smad genes.
- Sequencing of Smad1, Smad3, Smad5, and Smad6 in a total of 167 tumor samples.
- Tumor types analyzed included colon, breast, lung, and pancreas cancers.
Main Results:
- Novel sequences for human Smad5 and Smad6 were obtained.
- No mutations were detected in Smad1, Smad3, Smad5, or Smad6 in any of the 167 analyzed tumors.
- This indicates that these specific Smad genes are generally not mutated in these common human cancers.
Conclusions:
- The Smad gene family likely possesses diverse functions, as indicated by differential mutation patterns in cancer.
- Mutations in Smad1, Smad3, Smad5, and Smad6 do not generally account for the widespread resistance to TGF-β signaling observed in human tumors.
- Further research is needed to explore other mechanisms underlying TGF-β pathway dysregulation and cancer progression.