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

Abstract

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 mutation 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.