Myeloid Cell-based Immunotherapies for the Treatment of Cancer

Abstract

A key question in cancer immunotherapy is which features dictate therapeutic response versus non-response. Therapeutic responses to checkpoint blockade immunotherapies still hover around 15-20% across most cancers. Critical barriers to therapeutic response include the immune suppressive tumor microenvironment (TME), which is predominated by tumor-associated macrophages (TAMs). These TAMs generally promote tumor growth, invasion, metastasis, and resistance to treatment. Due to their high plasticity, TAMs can exhibit various phenotypes. Recent studies have revealed that some TAMs actually stimulate the immune response, challenging their traditional view as purely immunosuppressive. While prior approaches have been made to therapeutically target TAMs using antibodies binding cell surface proteins or growth factor pathways, these approaches have had limited clinical success. A possible reason why these approaches failed is that they targeted macrophages without identifying an immunological direction. Here, we show that systematic identification of stimuli to induce interleukin-12 (IL-12), a strongly anti-tumor cytokine produced by macrophages, provides novel combination therapies to induce IL-12 production natively within TAMs. We combine a high-throughput molecular screen for IL-12-inducing compounds with a cyclodextrin-based nanoparticle to create a Highly Active Myeloid Therapy (HAMT) that can complex small molecule immune modulatory drugs for simultaneous delivery into macrophages. By employing this simultaneous delivery strategy, we overcome the challenges of the uneven drug distribution that often results from differing pharmacokinetics in separate administrations to modulate macrophage more effectively. We hypothesized that a novel TAM-targeted nanoparticle, encapsulated with triple small-molecule drugs targeting the Janus Tyrosine Kinase (JAK1/2), the non-canonical nuclear factor kappa light chain enhancer of activated B cells (NF-κB), and toll-like receptor (TLR) pathways, would trigger native macrophage production of IL-12 to mitigate the immune suppressive microenvironment within tumors. To test the mechanism further, we applied intravital microscopy and flow cytometry to confirm that most nanoparticle uptake was into TAMs but not tumor cells or lymphocytes. We also demonstrate that HAMT treatment cohorts showed fewer terminally exhausted T cells compared to the control groups. Finally, we performed RNA sequencing on HAMT-stimulated bone marrow-derived macrophages, which characterized a novel TAM phenotype by an over-expression of IL-12, MARCO, DC-SIGN, and SIGNR7 and the absence of ISG, which includes the inhibitory factors PDL1 and IDO1/2.