Bone-Marrow-Targeted Nanocomposite Abrogates C-Myb-Survivin Cross Talk in MLL-AF9-Rearranged Acute Myeloid Leukemia in In Vitro and In Vivo Patient-Derived Xenograft Models

The heterogeneous form of malignancy in the myeloid lineage of normal hematopoietic stem cells (HSCs) is characterized as acute myeloid leukemia (AML). The t(9;11) reciprocal translocation (p22;q23) generates MLL-AF9 oncogene, which results in myeloid-based monoblastic AML with frequent relapse and poor survival. MLL-AF9 binds with the C-Myb promoter and regulates AML onset, maintenance, and survival. The bone marrow microenvironment (BMM) protects leukemia stem cells (LSCs) from therapeutic agents, which can lead to relapsed condition. Targeting leukemia BMM can be a viable therapeutics approach for AML treatment, wherein bone homing bisphosphonate, ibandronic acid (IBD), can localize to the BMM. In order to target the BMM of AML, C-Myb siRNA was entrapped in Vitamin D nanoemulsion-functionalized with BMM-targeted IBD, which exhibited binding with ex vivo bone slices and localization into mice bone marrow. IBD functionalization and C-Myb siRNA nanotherapy enhanced the suppression of LSCs (c-Kit⁺) and the upregulation of myeloid differentiation markers CD11b and Gr-1 in peripheral blood and bone marrow of athymic nude mice and patient-derived xenograft models. IBD functionalization enhanced the downregulation of C-Myb and C-Myb-Survivin cross talk in bone marrow and spleen tissue responsible for AML onset, maintenance, and pathogenesis. Further C-Myb binding to Survivin promoter was abrogated by the present bone-marrow-targeted nanotherapy, signifying its translational potential for AML therapeutics.