RUNX1 Inhibition Using Lipid Nanoparticle-Mediated Silencing RNA Delivery as an Effective Treatment for Acute Leukemias.

Transcription factor RUNX1 plays key roles in the establishment and maintenance of the hematopoietic system. Although RUNX1 has been considered a beneficial tumor suppressor, several recent reports have described the tumor-promoting role of RUNX1 in a variety of hematopoietic neoplasms. In this study, we assessed the effect of RUNX1 depletion in multiple human leukemia cell lines using the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 system, and confirmed that RUNX1 is in fact required for sustaining their leukemic proliferation. To achieve efficient RUNX1 inhibition in leukemia cells, we then examined the effect of lipid nanoparticle (LNP)-mediated delivery of RUNX1-targeting small interfering (si)RNA using two tumor-tropic LNPs. The LNPs containing RUNX1-targeting siRNA were efficiently incorporated into myeloid and T-cell leukemia cell lines and patient-derived primary human acute myeloid leukemia (AML) cells, downregulated RUNX1 expression, induced cell cycle arrest and apoptosis, and exhibited the growth-inhibitory effect in them. In contrast, the LNPs were not efficiently incorporated into normal cord blood CD34+ cells, indicating their minimum cytotoxicity. Thus, our study highlights RUNX1 as a potential therapeutic target to inhibit leukemogenesis, and provides the LNP-based siRNA delivery as a promising approach to deplete RUNX1 specifically in leukemia cells.