Background: Cancer is caused by the accumulation of mutations that activate proto-oncogenes and inactivate tumor suppressor genes. The result is a clonal expansion of genetically identical daughter cells that eventually become clinical malignancies. The specific mutations acquired by the progenitor cell are like a fingerprint carried by each cell of the tumor. These mutations can serve as very specific markers for the presence of tumor cells in a background of normal cells. Methods: Mutations in the p53 gene recovered from head and neck squamous cell carcinomas were sequenced, and these altered DNA sequences were used retrospectively as tumor-specific genetic markers for cancer cells in the patient's saliva. Cloned p53 sequences amplified by the polymerase chain reaction from DNA extracted from banked preoperative saliva specimens were screened for the presence of tumor-specific mutations using radiolabeled oligonucleotide probes. Results: We identified tumor-specific mutations in preoperative saliva samples of 5 of the 7 patients evaluated (71%). Conclusions: These results suggest a potential for clinical applications of this novel approach to cancer detection using gene mutations as molecular markers for carcinomas.
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