Purpose: The clinical significance of p21 expression remains unclear, whereas many experimental studies have demonstrated that p21, the product of the WAF1/CIP1/SDI1 gene, plays an important role in regulation of the cell cycle as an inhibitor of cyclin-dependent kinases. The purpose of this study was to clarify the clinical significance in resected non-small-cell lung cancer (NSCLC).
Patients and methods: A total of 233 consecutive patients with completely resected pathologic stage I to IIIA NSCLC were retrospectively reviewed. Expression of p21 and the status of p53 were examined immunohistochemically. Proliferative activity was also evaluated immunohistochemically. The incidence of apoptotic cell death was evaluated by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end-labeling staining.
Results: Expression of p21 was positive in 120 patients (51.5%). The 5-year survival rate of p21-positive patients was 73.8%, significantly higher than that of p21-negative patients (60.7%; P =.006). Aberrant expression of p53 was positive in 98 patients (42.1%). When combined with p53 status, the prognostic value of p21 status was enhanced: the 5-year survival rate of p21-positive and p53-negative patients was 80.7%, markedly higher than that of p21-negative and p53-positive patients (50.0% for both; P =.001). Multivariate analysis confirmed that positive expression of p21 was a significant factor for predicting a favorable prognosis. There was no significant correlation between p21 expression and p53 status, proliferative activity, or incidence of apoptosis.
Conclusion: p21 expression was shown to be an independent prognostic factor in NSCLC.