P53 PROTEIN DETECTED BY IMMUNOHISTOCHEMICAL STAINING IS NOT ALWAYS MUTANT

The expression of the tumour suppressor gene p53 was analyzed in a var iety of human solid tumours by immunohistochemistry and direct DNA seq uencing. Positive nuclear staining using a panel of anti-p53 antibodie s was used to select rumours for further genetic analysis. Using PCR a mplification followed by immobilization onto magnetic beads and direct sequencing, we sequenced exons 5-9 of the p53 gene from 9 melanomas, 8 nasopharyngeal carcinomas, 16 sporadic breast carcinomas and 11 pati ents from familial breast cancer families. No sequence alterations of the p53 gene were detected in either the melanoma or nasopharyngeal ru mours and only 19% of the primary breast carcinomas showed a variant b and indicative of a mutation. Our results indicate firstly that p53 mu tations are not generally involved in the tumour types studied and sec ondly the data emphasize the disparity encountered when attempting to correlate p53 immunohistochemical positivity with mutations within the p53 gene.