Bortezomib decreases Rb phosphorylation and induces caspase-dependent apoptosis in Imatinib-sensitive and -resistant Bcr-Abl1 expressing cells

Ignacio Perez-Roger (1) , Maria Pilar Albero (1) , Juana Maria Vaquer (1) , Enrique J Andreu (1) , Juan José Villanueva (1) , Laura Franch (1) , Carmen Ivorra (1) , Enric Poch (1) , Xabier Agirre (1) , Felipe Prosper (1)

1 Departament of Chemistry, Biochemistry and Molecular Biology

The use of c-abl specific inhibitors such as Imatinib or Dasatinib has revolutionized the treatment of Chronic Myeloid Leukemia. However, a significant percentage of patients become resistant to Imatinib. In this report, we have analyzed the possibility of using the proteasome as a molecular target in CML. Our results show that cells that express Bcr-Abl1 are more sensitive to the inhibition of the proteasome with Bortezomib than control cells. This treatment reduces the proliferation of Bcr-Abl1 expressing cells, by inactivating NF-B2 and decreasing the phosphorylation of Rb, eventually leading to an increase in caspase-dependent apoptosis. Furthermore, we show that Bortezomib also induces cell cycle arrest and apoptosis in cells expressing Bcr-Abl1 mutants that are resistant to Imatinib. These results unravel a new molecular target of Bortezomib, i.e. the Rb pathway, and open new possibilities in the treatment of CML especially for patients that become resistant to Imatinib due to the presence of the T315I mutation.

Mots clés: Bortezomib; CML; Bcr-Abl1; Imatinib-Resistance; Rb; Apoptosis

Ignacio Perez-Roger, Maria Pilar Albero, Juana Maria Vaquer, Enrique J Andreu, Juan José Villanueva, et al.. Bortezomib decreases Rb phosphorylation and induces caspase-dependent apoptosis in Imatinib-sensitive and -resistant Bcr-Abl1 expressing cells. Oncogene, 2010, ⟨10.1038/onc.2010.81⟩. ⟨hal-00519997⟩