THE SIGNIFICANCE OF PCNA AND P53 PROTEIN IN SOME ORAL TUMORS

The expression of PCNA and p53 protein was evaluated in a total of 75 cases of benign and malignant lesions of the oral cavity, comprising 5 0 squamous cell carcinomas (SCCs), 14 leukoplakias, and 11 pleomorphic adenomas. The DNA histogram of 20 SCCs was measured by flow cytometry . p53-positive cells were frequently seen in SCCs, but were rare in le ukoplakias and pleomorphic adenomas. The PCNA labeling index (LI) was higher in SCCs than in other benign lesions. The expression rate of p5 3 protein was markedly elevated in SCCs obtained from smoking patients , when compared to nonsmoking patients. DNA ploidy did not show a clos e relationship with PCNA and p53 expression. The mean value of PCNA LI for 22 cases carrying positive p53 protein was 52.3%, which was highe r than that of p53 protein negative cases (35.7%). The Kaplan-Meier su rvival curve of the patients who were negative for p53 was significant ly more favorable than for patients who were positive for p53 (P < 0.0 1, Cox-Mantel test). These results suggest that PCNA and p53 LI are ma rkers for the malignant potential of the oral mucosa, and are a useful indicator suggesting a poor prognosis.