Direct removal of circulating leukemia cells by magnetic hyperthermia

Abstract

Statement of Purpose: Removal of cancer cells in the blood system is an important therapeutics for leukemia patients. Chemotherapy has been widely used to remove cancer cells in the bloodstream, however, side effects have been a serious problem in the process. In this study, leukemia cell-specific removal directly in the bloodstream was performed in a leukemia animal model, AKR mouse, by using target-specific magnetic hyperthermia. Magnetic hyperthermia has been widely reported in an animal xenograft model, and most of them were performed to reduce tumor cell masses artificially prepared in mouse body. This study proposes a possible method to treat genetically modified animal model of leukemia by treatment of iron oxide magnetic particles modified with a specific antibody targeted to leukemia cells, anti-EpCAM antibody, and subsequent irradiation of magnetic field to the whole body of animals. Heat induction by iron oxide nanoparticles under magnetic field induced the removal of attached leukemia cells on the iron oxide nanoparticles. Methods: EpCAM antibody-immobilized iron oxide nanoparticles (E-MNPs, Myltenyi Biotec Inc.) were injected to AKR mice, as a leukemia animal model. A home-made magnetic set-up was used to irradiate the magnetic field on the whole body of mice. The number of leukemia cells was counted using a single cell analysis system (CelSee Inc.) and histological analysis. Thymus, the origin of T-cell type leukemia, was also analyzed for the removal of cancer cells, by Tunnel assay. Results: When MOLT-3 cells (leukemia T-cells) were treated E-MNPs and subsequent magnetic irradiation, the cell proliferation was decreased to 87% of control cells which were not irradiated to the magnetic field. In AKR mice, the number of leukemia cells in the bloodstream following intravenous injection of E-MNPs and subsequent hyperthermic treatment was reduced to 25% of control mice (Figure 1). The removal efficiency of leukemia cells by magnetic hyperthermia directly in the bloodstream was nearly 75%. Tunnel assay analysis also supported that hyperthermic treatment with E-MNPs could induce the apoptosis of leukemia cells in the thymus (Figure 2). The histological analysis showed that there were no side-effects by treatment of E-MNPs and irradiation of the magnetic field to the whole body of mice. Conclusions: Until now, most of the studies on magnetic hyperthermia have reported the effect of magnetic particles to reduce the tumor mass in solid tumor xenograft. In this study, magnetic particles could be targeted to circulating leukemia cells specifically. The target-specific magnetic hyperthermia caused a decrease of cancer cells by induction of heat to the microenvironment of magnetic particles. This study proposes a new approach of leukemia therapy using a new nanomedicine optimized for magnetic hyperthermia directly in the circulating system in vivo.