Purpose: Cyclin B1 is a key regulator of progression through the G2/M transition during the cell cycle. Although cyclin B1 proteins are overexpressed in various types of human cancers, the relationship between cyclin B1 status in gastric cancer and its clinical significance remains unknown. Methods: We examined cyclin B1 expression by immunohistological means in 61 patients with gastric cancer in terms of histological type, tumor invasion, and metastatic behavior. Specimens were considered positive when the cytoplasm of over 10% of the cancer cell population was stained. Results: Cyclin B1 was overexpressed in 32 (53%) of 61 patients with gastric cancer. Tumors that expressed cyclin B1 were predominant in older patients, in well- and moderately differentiated adenocarcinomas and in expanding-growth type tumors. Conversely, expression of cyclin B1 was lower in poorly differentiated adenocarcinomas, and in those of the infiltrative growth type. Moreover, the disease was more advanced (stages III and IV) and widespread nodal involvement was more frequent when cyclin B1 expression was low. Logistic regression analyses showed that histological type is a significant factor related to cyclin B1 protein expression. Conclusions: These findings suggested that cyclin B1 protein overexpression is closely associated with less aggressive tumor behavior. Therefore, G2/M cyclin alternatives and the possible role of cyclins in cancer development warrants further attention.
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