title: 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.
abstract: 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.
authors.affiliation: School of Biosciences and Veterinary Medicine, University of Camerino, Camerino, Italy.
authors.forename: Consuelo
authors.initials: C
authors.lastname: Amantini
authors.affiliation: School of Pharmacy, Experimental Medicine Section, University of Camerino, Camerino, Italy ; Department of Molecular Medicine, Sapienza University, Rome, Italy.
authors.forename: Maria Beatrice
authors.initials: MB
authors.lastname: Morelli
authors.affiliation: Department of Medical Oncology, Polytechnic University of Marche, Ancona, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Santoni
authors.affiliation: Department of Molecular Medicine, Sapienza University, Rome, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Soriani
authors.affiliation: School of Pharmacy, Experimental Medicine Section, University of Camerino, Camerino, Italy ; Department of Molecular Medicine, Sapienza University, Rome, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Cardinali
authors.affiliation: Department of Molecular Medicine, Sapienza University, Rome, Italy.
authors.forename: Valerio
authors.initials: V
authors.lastname: Farfariello
authors.affiliation: School of Biosciences and Veterinary Medicine, University of Camerino, Camerino, Italy.
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Eleuteri
authors.affiliation: School of Biosciences and Veterinary Medicine, University of Camerino, Camerino, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Bonfili
authors.affiliation: School of Biosciences and Veterinary Medicine, University of Camerino, Camerino, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Mozzicafreddo
authors.affiliation: School of Pharmacy, Experimental Medicine Section, University of Camerino, Camerino, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Nabissi
authors.affiliation: Department of Molecular Medicine, Sapienza University, Rome, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Cascinu
authors.affiliation: School of Pharmacy, Experimental Medicine Section, University of Camerino, Camerino, Italy.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Santoni
keywords: Akt; TKI; bladder cancer cells; cathepsin B; perifosine; sorafenib