A proposal for the integration of immunohistochemical staining and DNA-based techniques for the determination of TP53 mutations in human carcinomas

The p53 protein plays an important role in the control of the cell cycle an d DNA repair. Mutations in the TP53 gene may be a prognostic factor for cer tain forms of human cancer, with specific mutation sites being associated w ith significantly worse prognosis, particularly for colorectal and breast c ancer. Thus, standardization of accurate, rapid, and cost-effective techniq ues for the detection of TP53 mutations is a high priority . At present, th e only widely available technology that reliably detects and defines all mu tations is DNA sequencing. However, the routine sequencing of the entire TP 53 gene in all breast and colorectal cancer cases in hospital laboratories is prohibitively costly, complex, and time consuming. In order for the anal ytical power of DNA to be accessed by the routine laboratory, initial scree ning using immunohistochemistry, which is widely used as a test for detecti on of accumulated, mutated protein, followed by heteroduplex analysis of ex ons 4 to 9 to detect frameshift mutations in immunohistochemistry-negative cases, is proposed. To illustrate the effectiveness of this approach, 28 ca ses of head and neck squamous-cell carcinomas that were known to contain TP 53 mutations were retrospectively analyzed. All missense mutations stained positive on immunohistochemistry using the monoclonal antibody DO7, and all insertions and deletions, even those involving a single nucleotide, were p ositive using an extremely simple heteroduplex analysis. Only rare nonsense mutations were not detected by this strategy. Nevertheless, application of these results to published data suggests that the prescreening would detec t 80% of mutations but would result in a 75% reduction in the sequencing lo ad of the laboratory.