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Mutations of the p53 gene are not detectable in human testicular tumors
M Fleischhacker1, T Strohmeyer, Y Imai
1Division of Hematology-Oncology, Cedars-Sinai Medical Center, Los Angeles, California.
Abstract:
The tumor suppressor gene p53 is the most frequently mutated gene in human cancer. We have used polymerase chain reaction-single-strand conformation polymorphism analysis and sequencing to examine the status of the p53 gene in human testicular cancers of various histologies. We were unable to find in 40 samples and four cell lines any mutations in the regions of this gene (exons 5 through 8) that are usually mutated in other cancers. Northern blot analysis showed expression of this gene in most of the samples analyzed, as well as in four human testicular tumor cell lines. The MDM-2 gene is amplified and overexpressed in sarcomas; it binds and functionally inactivates p53. The 44 testicular tumor samples and cell lines were examined for amplification of MDM-2 by dot-blot analysis; none was found. The proto-oncogene c-kit probably plays an important role in normal testicular development. Mutation of the tyrosine phosphorylation site of a closely related member of this family of tyrosine kinase receptors (c-fms) is associated with cellular transformation and cancer. Codon 936 is the analogous tyrosine of c-kit; using polymerase chain reaction-single-strand conformation polymorphism analyses, we were unable to detect mutations at this site in our 44 testicular cancer samples. We conclude from our studies that mutations in the most conserved region of the p53 gene, as well as at codon 936 of the c-kit gene and amplification of MDM-2, are extremely rare in human testicular cancers.
Insights
Mutations in the p53 tumor suppressor gene and MDM-2 amplification are rare in human testicular cancers. The c-kit proto-oncogene also showed no mutations at a key site, suggesting these are not primary drivers of testicular tumors.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- The p53 tumor suppressor gene is frequently mutated in various human cancers.
- Understanding genetic alterations in testicular cancer is crucial for diagnosis and treatment.
- Proto-oncogenes like c-kit play roles in normal development and can be implicated in cancer.
Purpose of the Study:
- To investigate mutations in the p53 gene and MDM-2 amplification in human testicular cancers.
- To examine the c-kit proto-oncogene for mutations at a specific tyrosine phosphorylation site.
- To determine the frequency of these genetic alterations in testicular tumors.
Main Methods:
- Polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) analysis and sequencing were used to detect p53 gene mutations.
- Northern blot analysis assessed p53 gene expression.
- Dot-blot analysis was employed to screen for MDM-2 gene amplification.
- PCR-SSCP was also used to analyze mutations at codon 936 of the c-kit gene.
Main Results:
- No mutations were found in the commonly mutated regions (exons 5-8) of the p53 gene in 40 testicular cancer samples and four cell lines.
- p53 gene expression was detected in most analyzed samples and cell lines.
- No amplification of the MDM-2 gene was detected in 44 testicular tumor samples and cell lines.
- No mutations were detected at codon 936 of the c-kit gene in 44 testicular cancer samples.
Conclusions:
- Mutations in the highly conserved regions of the p53 gene are extremely rare in human testicular cancers.
- Amplification of MDM-2 and mutations at codon 936 of c-kit are also rare in these cancers.
- These findings suggest that alterations in p53, MDM-2, and c-kit are unlikely to be major contributors to the development of human testicular cancer.