Effective Targeting Of Chronic Myeloid Leukemia Initiating Activity With The Combination Of Arsenic Trioxide and Interferon Alpha

Imatinib is the standard of care in the treatment of Chronic Myeloid Leukemia (CML) patients. However, imatinib is not curative since most patients who discontinue therapy will relapse, stressing the need for novel therapies that target leukemia initiating cells (LIC). Arsenic trioxide induces complete remission in patients with acute promyelocytic leukemia (APL). We previously demonstrated that, through full degradation of PML-RARA, the combination of arsenic and retinoic acid eradicates APL LICs and cures the disease. Interferon alpha (IFN) induces hematologic and cytogenetic remissions and interestingly, improved outcome was reported with the combination of interferon and imatinib. We investigated the effects of arsenic and IFN on human CML cell lines or primary cells and the bone marrow retroviral transduction/transplantation murine CML model. In vitro, the combination of arsenic and IFN inhibited proliferation and activated apoptosis. Importantly, arsenic and IFN synergistically reduced the clonogenic activity of primary bone marrow cells derived from CML patients. Moreover, in a murine transplantation model of CML, we show that arsenic/IFN prolonged survival of primary leukemic mice and sharply diminished transplantation of CML cells in secondary recipients, pointing to exhaustion of CML LICs. Our results also suggest that IFN/arsenic may clear LICs independently from oncoprotein catabolism. Interestingly, arsenic/IFN effect on CML LIC activity was significantly superior to that of imatinib.These studies plea for a clinical exploration of this combination, knowing that IFN and arsenic have both shown clinical activity in CML, alone or in combination with imatinib.