P21 WAF1 PROTEIN EXPRESSION IN NASOPHARYNGEAL CARCINOMA - COMPARATIVE-STUDY WITH PCNA, P53 AND MDM-2 PROTEIN EXPRESSION/

We investigated the immunohistochemical expression of p21/waf1 protein in 59 cases of nasopharyngeal carcinomas (NPC) and compared p21 expre ssion with PCNA, p53 and mdm2 protein expression. We found p21, PCNA, p53 and mdm2 in 59/59, 59/59, 18/59 and 12/59 nasopharyngeal carcinoma s, respectively. We observed a tendency to a relationship between high expression of PCNA (>%5%positivity in tumour cells) and low expressio n of p21 protein. Parallel p53/p21 protein expression was found in 18 cases. Twelve were also mdm2 positive. This pattern may represent NPC with wild type (wt) p53 since mdm2 and p21 proteins are inducible by w t p53 gene. In these cases p53 protein expression may be due to stabil isation to mdm2 protein. This could be important in the pathogenesis o f these cases since mdm2 may deregulate the p53-dependent growth suppr essive pathway. Discordant p53-/p21+ protein expression was found in 4 1 cases. All were also mdm2 negative. This pattern suggests immunohist ochemically undetectable wt p53 gene which is able to induce p21 prote in expression.