The decrease of cyclin B2 expression inhibits invasion and metastasis of bladder cancer

It has been shown that cyclin B2 is commonly overexpressed in many malignant tumors. This study aimed to investigate the potential role of cyclin B2 in bladder cancer.

Fixed tissues for immunohistochemistry and fresh tissues for western blotting and quantitative real-time polymerase chain reaction assay were randomly selected from Nanfang hospital. Normal bladder urothelial cell and bladder cancer cell lines was stored in our laboratory, the bladder cancer cells were transfected to develop bladder cancer cell clones expressing decreased cyclin B2 levels, the clones were used for cell growth and metastasis experiments in vitro and in vivo.

Western blot and immunohistochemical analysis both showed that the cyclin B2 protein expression was higher in bladder urothelial carcinoma than in normal bladder mucosa, especially in invasive cancer. Real-time polymerase chain reaction showed that the cyclin B2 messenger RNA expression exhibited the same trend. Results of cell lines experiments also showed higher cyclin B2 expression in cancer cells. In vitro tests the decrease of cyclin B2 expression that had little effect on cell growth and cell cycling according to the MTT assay and the Edu assay, whereas in the Boyden chamber transwell assay, the cyclin B2 low-expressing clones significantly inhibits the cells׳ invasion and metastatic abilities. This result was consistent with the scratch-wound assay result showing that the target clone needed more time for healing the wound. The in vivo experiment in nude mice produced similar results, the lung and liver target cell metastasis nodules were smaller and less than those of the negative control by the hepatic subcapsular injection assay, and the mice of the target clone group has longer survival time in no intervention observed test.

These results indicate that the cyclin B2 was overexpressed in bladder cancer, and the down-regulation of cyclin B2 expression in bladder cancer greatly inhibits the cell׳s invasion and metastatic abilities, and it prolonged the survival time of nude mice in vivo.