Increased expression levels of cyclin-dependent kinase inhibitor p27 correlate with good responses to platinum-based chemotherapy in non-small cell lung cancer.

In order to determine whether expression of the cyclin-dependent kinase inhibitor p27 in non-small cell lung cancer (NSCLC) correlates with chemotherapeutic response, resected tumors from 22 patients with recurrent lung cancer who had undergone complete resection and received chemotherapy after the initial tumor recurrence were subjected to p27 immunostaining. Histological examination of the resected tumors revealed 14 adenocarcinomas, 7 squamous cell carcinomas and one adenosquamous cell carcinoma. Fifty percent or less and over 50% of the cells in the resected tumors of 11 patients each (groups 1 and 2, respectively) were p27-immunopositive. All but one patient received platinum-based chemotherapy after recurrence. Only one in group 1 achieved a partial response (PR) in chemotherapy whereas 2 and 4 in group 2 achieved complete and PRs, respectively. The chemotherapy response rate of group 2 (54%) was significantly higher than that of group 1 (9%, p=0.022). The times to recurrence after tumor resection of the 2 groups did not differ significantly (log-rank p=0.23, Wilcoxon p=0. 32), but survival after chemotherapy of group 2 was significantly better than that of group 1 (log-rank p=0.045, Wilcoxon p=0.028). It is suggested that high p27 expression levels in tumors may predict the good responses to platinum-based chemotherapy for NSCLC.