Cyclin B1 plays an important role in the mitotic cycle, in which it regulates the G2-M transition, and has been suggested to play a role in development and progression of various cancers. The present study was undertaken in order to clarify the role of the cell cycle regulator cyclin B1 in non-small cell carcinoma (NSCLC). We retrospectively investigated 174 patients with NSCLC who previously underwent complete resection. There were two study groups: the squamous cell carcinoma (SCC) group (n=62); and the non-SCC group (n=112). Expression of cyclin B1 in cancer cells was analyzed immunohistochemically. The rate of cyclin B1 positivity in cancer cells ranged from 0% to 56.5% (average 10.9%). Seventy-four cases (42.5%) were designated as cyclin B1 positive in the present study. Cyclin B1 expression was observed more frequently in SCC cases than in non-SCC cases. In SCC, cyclin B1 expression demonstrated significant correlation with gender (p<0.01) and histological type (p<0.01). In non-SCC, only gender was correlated with cyclin B1 expression. Five-year survival rates for cyclin B1-positive and cyclin B1-negative cases were 45.8 and 57.9%, and 10-year survival rates were 39.3 and 51.4%, respectively. Patients with positive cyclin B1 staining showed a lower survival rate than those with negative staining (p=0.11). The prognostic value in SCC cases was p=0.48. In non-SCC cases, the survival rate of non-SCC patients who were positive for cyclin B1 was significantly lower than that of patients who were negative (p<0.01). Using multivariate analysis, tumor size (p=0.037) and N factor (p=0.026) were found to be independent prognostic parameters. Cyclin B1 expression was not an independent prognostic factor in the present series. These data suggest that elevated levels of cyclin B1 expression may be an indicator of poor prognosis in NSCLC, particularly in non-SCC.

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