The Inhibition of Chk1/Chk2 and Wee-1 Kinases as a Promising Therapy for the Treatment of Adult Acute Lymphoblastic Leukemia

Due to inadequate treatments, the survival rate of adult patients with acute lymphoblastic leukemia (ALL) is still very poor. Thus there is a need to improve the efficacy of conventional therapy. In this study we evaluated the effectiveness of checkpoint kinase inhibitors (Chk-i) in single agent and in combination with different compounds conventionally used for the treatment of B-/T-ALL. We showed that Chk1 and Chk2 kinases are highly expressed and hyper-activated in tumor samples in comparison to normal tissue. On these bases we speculate that the inhibition of these kinases could mine the genetic stability and enhance cell death in ALL cells. We firstly evaluate the efficacy in single agent of the Chk1/Chk2 (PF-0477736 and LY2606368) and of the Wee1 (MK-1775) inhibitors on different cell lines and on primary cells isolated from adult B-ALL patients. We demonstrated that the inhibition of Chk1/Chk2 kinases reduces of the cell viability, activates the apoptosis and modify the expression of different elements of the G2/M checkpoint. To assess the chemo-sensitizer activity of different checkpoint kinase inhibitors, several combination studies were performed. To this purpose, LY2606368 and MK-1775 were combined with different tyrosine kinase inhibitors (imatinb, dasatinib and bosutinib) and with the purine nucleoside analogue, clofarabine. The efficacy of the combinations was not only evaluated in term of reduction of the cell viability but also in term of induction of apoptosis and induction of DNA damages. The results found were then confirmed on primary cells of B-ALL patients. Finally different class of checkpoint kinase inhibitors were combined together in order to evaluate their interaction. In our opinion the preclinical data presented in this study are the basis for a future evaluation of this class of compound in clinical trials in the treatment of adult ALL patients.