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 is a highly sensitive method of detection of p53 mutations in clinical specimens. Our earlier report (1) showed a 35.4% p53 mutation frequency in Hong Kong colorectal carcinoma (CRC) patients, when conventional molecular screening 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 techniques was under-estimated and if so, to see if other hot spots for mutations explain this difference. Results, The p53 functional yeast assay results showed an increased mutation frequency. However, sequencing showed the mutations were confined to common hot spots for mutations in exons 6 and 7. Conclusions: The mutation frequency in CRC patients observed with the yeast assay is higher than previously reported. Forty-five percent of 20 SSCP-negative specimens were positive by the yeast assay, which this study shows is superior for detection of p53 mutations directly in clinical specimens containing varying amounts of normal tissue contamination.