Catalpol Inhibited the Proliferation of T24 Human Bladder Cancer Cells by Inducing Apoptosis Through the Blockade of Akt-Mediated Anti-apoptotic Signaling

Catalpol is an iridoid glucoside extracted from the traditional Chinese medicinal plant called Rehmannia glutinosa, and it is reported to possess a variety of pharmacological activities. The goal of this research was to explore the effect of catalpol on the human bladder cancer cells T24. The cells were treated for different durations with various concentrations of catalpol. Then the viability, mobility, and invasiveness of the cells were determined by MTT assay and flow cytometry, respectively. Catalpol was found to significantly suppress the proliferation, migration, and invasiveness of T24 bladder cancer cells in a dose- and time-dependent manner. The results also revealed that catalpol promoted apoptosis and caused the cell-cycle arrest at G2/M phase. Furthermore, the catalpol-mediated apoptosis was found to involve the modulation of PI3K/Akt pathway and inhibit the expression of anti-apoptotic B cell lymphoma-2 (Bcl-2) family proteins. Also, the expressions of Bcl-2 proapoptotic effectors, Bcl-2-associated X protein, and Bcl-2 associated death promoter were up-regulated in the cells treated with catalpol. The enzymes involved in the ultimate process of apoptosis, active caspase-3 and poly ADP ribose polymerase were elevated, and the latter was observed to be cleaved, indicating that catalpol-accelerated cell apoptosis involved a caspase-dependent pathway. These results suggest that catalpol might serve to be a promising therapeutic agent for the treatment of human bladder cancer.