Sorafenib induces cathepsin B-mediated apoptosis of bladder cancer cells by regulating the Akt/PTEN pathway. The Akt inhibitor, perifosine, enhances the sorafenib-induced cytotoxicity against bladder cancer cells.
Consuelo Amantini1, Maria Beatrice Morelli2,3, Matteo Santoni4, Alessandra Soriani3 Claudio Cardinali2,3, Valerio Farfariello3, Anna Maria Eleuteri1, Laura Bonfili1, Matteo Mozzicafreddo1, Massimo Nabissi2, Stefano Cascinu3, Giorgio Santoni2
1 School of Biosciences and Veterinary Medicine, University of Camerino, Camerino, Italy
2 School of Pharmacy, Experimental Medicine Section, University of Camerino, Camerino, Italy
3 Department of Molecular Medicine, Sapienza University, Rome, Italy
4 Department of Medical Oncology, Polytechnic University of Marche, Ancona, Italy
Giorgio Santoni, email:
Keywords: sorafenib, bladder cancer cells, cathepsin B, Akt, TKI, perifosine
Received: January 27, 2015 Accepted: March 16, 2015 Published: March 23, 2015
Sorafenib, a tyrosine kinase inhibitor, has been demonstrated to exert anti-tumor effects. However, the molecular mechanisms underlying its effects on bladder cancer remain unknown.
Here, we evaluated the mechanisms responsible for the sorafenib-induced anti-tumor effects on 5637 and T24 bladder cancer cells. We demonstrated that sorafenib reduces cell viability, stimulates lysosome permeabilization and induces apoptosis of bladder cancer cells. These effects are dependent by the activation of cathepsin B released from lysosomes. The sorafenib-increased cathepsin B activity induced the proteolysis of Bid into tBid that stimulates the intrinsic pathway of apoptosis characterized by mitochondrial membrane depolarization, oxygen radical generation and cytochrome c release. Moreover, we found that cathepsin B enzymatic activity, induced by sorafenib, is dependent on its dephosphorylation via PTEN activation and Akt inactivation. Pretreatment with orthovanadate rescued bladder cancer cells from apoptosis. In addition, the Akt inhibitor perifosine increased the sensitivity of bladder cancer cells to sorafenib-induced cytotoxicity.
Overall, our results show that apoptotic cell death induced by sorafenib in bladder cancer cells is dependent on cathepsin B activity and involved PTEN and Akt signaling pathways. The Akt inhibitor perifosine increased the cytotoxic effects of sorafenib in bladder cancer cells.