P53 ACCUMULATION AND PROLIFERATING-CELL NUCLEAR ANTIGEN EXPRESSION IN HUMAN LUNG-CANCER

Mutations in the p53 gene are currently the commonest genetic alterations in human malignant tumors, including non-small-cell lung cancer (NSCLC) and small-cell lung cancer (SCLC). Alterations of the protein induced by gene mutations enables the mutant protein to become more stable, resulting in the accumulation of P53 in quantities detectable by immunohistochemistry. Although previous studies document the accumulation of P53 in lung cancer, there is little information regarding the usual frequency of accumulation based on a comprehensive number of lung tumors. A total of 328 paraffin-embedded lung carcinoma specimens were analyzed for P53 accumulation and for the expression of the proliferating-cell nuclear antigen (PCNA) by standard immunohistochemistry. Among 49 SCLC, 35% were positive for p53 and 51% were positive for PCNA. Out of 279 NSCLC, 43% showed a positive P53 immunoreaction and 72% displayed detectable amounts of PCNA. In squamous-cell carcinomas a statistically significant increased accumulation of P53 was found compared to adenocarcinomas (P = 0.001). Among the 233 PCNA-positive tumors the relative number of P53-positive specimens was higher compared to the total number of tumors. Since immunohistochemical investigations should contribute to the improvement of the clinical diagnosis and treatment or give information on the prognosis, we conclude from our results that it seems to be legitimate to assess the P53 status exclusively in the specimens positive for PCNA. Immunohistochemical investigations under consideration of the PCNA status yielded good and fast recognition of p53 mutations leading to intracellular P53 protein accumulation.