Myeloid cell-targeted miR-146a mimic inhibits NF-κB-driven inflammation and leukemia progression in vivo.

NF-κB is a key regulator of inflammation and cancer progression, with an important role in leukemogenesis. Despite its therapeutic potential, targeting NF-κB using pharmacologic inhibitors has proven challenging. Here, we describe a myeloid cell-selective NF-κB inhibitor using an miR-146a mimic oligonucleotide conjugated to a scavenger receptor/Toll-like receptor 9 agonist (C-miR146a). Unlike an unconjugated miR146a, C-miR146a was rapidly internalized and delivered to the cytoplasm of target myeloid cells and leukemic cells. C-miR146a reduced expression of classic miR-146a targets (IRAK1 and TRAF6), thereby blocking activation of NF-κB in target cells. IV injections of C-miR146a mimic to miR-146a-deficient mice prevented excessive NF-κB activation in myeloid cells, and thus alleviated myeloproliferation and mice hypersensitivity to bacterial challenge. Importantly, C-miR146a showed efficacy in dampening severe inflammation in clinically relevant models of chimeric antigen receptor (CAR) T-cell-induced cytokine release syndrome. Systemic administration of C-miR146a oligonucleotide alleviated human monocyte-dependent release of IL-1 and IL-6 in a xenotransplanted B-cell lymphoma model without affecting CD19-specific CAR T-cell antitumor activity. Beyond anti-inflammatory functions, miR-146a is a known tumor suppressor commonly deleted or expressed at reduced levels in human myeloid leukemia. Using The Cancer Genome Atlas acute myeloid leukemia data set, we found an inverse correlation of miR-146a levels with NF-κB-related genes and with patient survival. Correspondingly, C-miR146a induced cytotoxic effects in human MDSL, HL-60, and MV4-11 leukemia cells in vitro. The repeated IV administration of C-miR146a inhibited expression of NF-κB target genes and thereby thwarted progression of disseminated HL-60 leukemia. Our results show the potential of using myeloid cell-targeted miR-146a mimics for the treatment of inflammatory and myeloproliferative disorders.