CXCR4 antagonistic lipid nanoparticles loading siRNA combat refractory AML through AML1-ETO depletion and homoharringtonine sensitization.

Acute myeloid leukemia (AML) is characterized by uncontrolled malignant clonal proliferation of leukemic cells resulting from the blockade of myeloid hematopoietic stem/progenitor cell differentiation. The disease-causing fusion protein AML1-ETO (also known as RUNX1-ETO or RUNX1-RUNX1T1) and the chemokine (C-X-C motif) receptor 4 (CXCR4) have been recognized as crucial effectors. Strategies targeting each individual factor have been applied to develop new therapeutic approaches; however, clinical demands remain unmet, and much is still unknown about the crosstalk between the two factors. In this study, we utilized a lipid nanoparticle platform to carry AML1-ETO siRNA and the CXCR4 antagonistic peptide E5 (E5-LNP@siAE) to simultaneously deplete the fusion protein and inhibit CXCR4 activation, aiming to elucidate the crosstalk between the two factors and to develop a novel dual-functional therapeutic approach based on lipid nanoparticles. The resulting nanoparticles were investigated in a refractory AML mouse model (AML1-ETO & C-KITD816V) with a high level of CXCR4 and in the t(8; 21)-positive AML cell line Kasumi-1. It was shown that E5-LNP@siAE effectively achieved RNAi of AML1-ETO and antagonism of CXCR4, thereby synergistically inducing effective multi-lineage differentiation, leading to significantly enhanced differentiation-post apoptotic responses of AML cells to homoharringtonine and remarkably prolonged survival in refractory AML mice.