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Examination of human tumors for rhoA mutations
1Medicine Branch, National Cancer Institute, Bethesda, MD 20892.
Abstract:
rhoA encodes a ras-related GTP-binding protein that is thought to play a role in cytoskeletal organization. Recent evidence has suggested both that rhoA could act either as a dominant oncogene, since transfection of both normal and activated rho genes confer a transformed phenotype on fibroblast cells in culture, or as a recessive tumor suppressor gene, by virtue, in part, of its chromosomal location at 3p21, a site deleted in many human malignancies. In either case, a role for rhoA in the oncogenesis of human tumors would be supported by the finding of rhoA mutations in tumors. We therefore examined human tumors and cell lines for mutations in the protein coding regions of rhoA by RNAase protection analysis. We first examined the expression of rhoA in renal cell carcinoma cell lines in which 3p21 was heterozygously deleted or retained. We found no evidence for rhoA mutations in these specimens. We also examined RNA from lung, breast, colon or ovarian tumors and also found no evidence of activating rhoA mutations. Furthermore, there was no relation between the level of rhoA mRNA expression and the presence or absence of 3p21 deletions in the renal cell carcinoma specimens. Thus, although rhoA has transforming potential in vitro, there is no evidence that it is activated by mutation in human malignancies, or that it could act as a tumor suppressor gene in tumors in which 3p21 is deleted.
Insights
This study investigated mutations in the rhoA gene in human tumors. Researchers found no evidence of rhoA mutations in various cancers, suggesting it does not play a significant role in oncogenesis through mutation.
Area of Science:
- Molecular Biology
- Oncology
- Genetics
Background:
- The rhoA gene encodes a ras-related GTP-binding protein involved in cytoskeletal organization.
- rhoA has shown transforming potential in vitro, suggesting a possible role in oncogenesis.
- Its chromosomal location at 3p21, frequently deleted in malignancies, implies potential tumor suppressor functions.
Purpose of the Study:
- To investigate the presence of mutations in the protein-coding regions of the rhoA gene in human tumors and cell lines.
- To determine if rhoA mutations are associated with cancer development or its potential role as an oncogene or tumor suppressor.
Main Methods:
- RNAase protection analysis was employed to detect mutations in the rhoA gene.
- Analysis focused on renal cell carcinoma cell lines with and without 3p21 deletions.
- RNA from lung, breast, colon, and ovarian tumors was also examined for rhoA mutations.
Main Results:
- No rhoA mutations were detected in renal cell carcinoma cell lines, regardless of 3p21 deletion status.
- No activating rhoA mutations were found in RNA from lung, breast, colon, or ovarian tumors.
- rhoA mRNA expression levels showed no correlation with 3p21 deletions in renal cell carcinoma.
Conclusions:
- Despite its in vitro transforming potential, rhoA is not activated by mutation in the human malignancies studied.
- The findings do not support a role for rhoA as an oncogene activated by mutation or as a tumor suppressor gene in tumors with 3p21 deletions.