A COMPARATIVE-STUDY OF DETECTION OF P53 MUTATIONS IN HUMAN BREAST-CANCER BY FLOW-CYTOMETRY, SINGLE-STRAND CONFORMATION POLYMORPHISM AND GENOMIC SEQUENCING

The accuracy of immunodetection by dual parameter dow cytometry (FCM), polymerase chain reaction-mediated single strand conformation polymor phism (PCR-SSCP) and genomic sequencing to detect p53 mutations were c ompared. Analysis by the last two techniques was restricted to exons 5 -8. Initially, 110 breast tumours were screened for p53 expression by FCM. Seventy (64%) of tumours were immunopositive. Fifteen highly immu nopositive and 15 completely immunonegative tumours were selected for further analysis by PCR-SSCP and genomic sequencing. Eleven out of 15 immunopositive tumours were found to have mutation by PCR-SSCP. Genomi c sequencing confirmed the presence of mutation in 10 of these 11 immu nopositive tumours. Therefore, four immunopositive tumours failed to s how mutation by SSCP and five by genomic sequencing. Of the 15 immunon egative tumours, one showed mutation by both PCR-SSCP and genomic sequ encing and one tumour has undergone deletion of the p53 gene. Overall, immunoreactivity correlated with both PCR-SSCP and genomic sequencing in 80% of cases (24/30), and there was 96.5% (28/29) concordance betw een PCR-SSCP and genomic sequencing. We conclude that there is good co ncordance between mutations detected by PCR-SSCP and genomic sequencin g, but immunochemical detection of p53 overexpression is not an absolu te indicator of p53 gene mutation.