P53 AND PCNA COEXPRESSION OF 81 PLEURAL AND PERITONEAL EFFUSION SPECIMENS - AN IMMUNOHISTOCHEMICAL STUDY

Several studies have indicated that wild type p53 plays an important r ole in controlling cell growth and acts as a cyclin modifier. Abnormal ities in p53 induce the over-expression of proliferating cell nuclear antigen. The aim of this study is to correlate immunocytochemically th e expression of mutant p53 and the proliferative index (PI) as indicat ed by image analysis of PCNA immunoreactivity in 81 cases of pleural a nd peritoneal effusions. There was a strong correlation (r = 73%) betw een p53 immunoreactivity and PCNA Pls. Forty-three (71 %) cases indica ted p53 immunostaining out of 61 cases with PCNA immunoreactivity, for ty of which (93 %) proved to have a diagnosis of malignancy using hist ological or clinical data. Furthermore, 7 malignant cases showed PCNA reactivity but no p53 immunostaining. An additional four malignant cas es indicated no reactivity for either p53 or PCNA. Also, there was a s ignificant difference in the PCNA PI between benign and malignant effu sions (p < 0.001). These clinical observations confirm the function of wild p53 as a check point during cell cycling, and as a strong negati ve feedback effect on PCNA expression. Furthermore, such co-expression represents a significant indicator for malignancy.