P53 ABERRATIONS IN ORAL SUBMUCOUS FIBROSIS AND ORAL SQUAMOUS-CELL CARCINOMA DETECTED BY IMMUNOCYTOCHEMISTRY AND PCR-SSCP

An archival series of oral biopsies from Karachi, Pakistan, consisting of 21 cases of oral submucous fibrosis (OSF) and 27 cases of squamous cell carcinoma (SCC), of which 6 had arisen from OSF, were used to ex amine the aberrations in the structure and expression of the p53 tumou r suppressor gene. The PCR-SSCP method was used for mutation analysis of exons 2-9, and (over)expression of p53 protein was detected by immu nocytochemistry using monoclonal antibody DO 7. Positive immunostainin g was observed in 15/20 (75%) of OSF specimens, 3/6 (50%) of SCC arisi ng from OSF and 14/21 (67%) of SCC not arising from OSF. Mobility shif ts in SSCP indicative of a mutation in p53 or loss of heterozygosity ( deletion of a band) were seen in 13/21 cases of OSF and 15/27 cases of SCC. There was concordance between immunocytochemistry and SSCP resul ts in a majority (33/48) of samples. Though the number of analysed SCC cases arising from OSF was limited, the results suggest that p53 muta tion/protein stabilisation may play a part in the pathogenesis of OSF and its progression to SCC.