p53 mutation and detection of p53 protein expression in oral leukoplakia and oral squamous cell carcinoma.

In many studies the detection of p53 protein by immunohistochemistry (IHC) with one antibody is assumed to be consistent with a mutation of the gene. To determine the correlation of protein detection by immunohistochemistry and gene mutation, paraffin embedded specimens of 60 oral leukoplakias (OL) and 73 oral squamous cell carcinomas (OSCC) were analysed by IHC with two different antibodies (Do7; Pab 1801), PCR-SSCP and sequencing. In 98% of OLs and 94% of OSSCs p53 protein expression was detected with at least one antibody. Only 49% of all tissue specimen were positive with both antibodies. Molecular analysis of the same specimen showed mutations of the p53 gene in 13.3% of OLs and 9, 6% of OSCCs. p53 protein expression was not detected by IHC in 3 out of 7 OSCC with p53 mutations. According to these results detection of p53 expression by IHC is not always correlated with p53 gene mutation and failure to detect p53 protein by IHC does not prove the absence of mutation of the gene in the carcinogenesis in the oral mucosa.