Detection of p53 mutations in Hong Kong colorectal carcinomas by conventional PCR-SSCP analysis versus p53 yeast functional assays

Background: Previous reports indicate that the p53 yeast functional assay i s a highly sensitive method of detection of p53 mutations in clinical speci mens. Our earlier report (1) showed a 35.4% p53 mutation frequency in Hong Kong colorectal carcinoma (CRC) patients, when conventional molecular scree ning techniques were utilized to assess the mutation rate in the hot spots in exons 5-8. Materials and methods: The yeast functional assay was used to determine if the previous mutation frequency determined by PCR-SSCP techni ques was under-estimated and if so, to see if other hot spots for mutations explain this difference. Results, The p53 functional yeast assay results s howed an increased mutation frequency. However, sequencing showed the mutat ions were confined to common hot spots for mutations in exons 6 and 7. Conc lusions: The mutation frequency in CRC patients observed with the yeast ass ay is higher than previously reported. Forty-five percent of 20 SSCP-negati ve specimens were positive by the yeast assay, which this study shows is su perior for detection of p53 mutations directly in clinical specimens contai ning varying amounts of normal tissue contamination.