CAR-Macrophages and CAR-T Cells Synergistically Kill Tumor Cells In Vitro

Abstract

Chimeric antigen receptor (CAR)-expressing macrophages (CAR-M) have a great potential to improve cancer therapy, as shown from several recent preclinical studies. However, unlike CAR-T cell therapy, which has been widely studied, the efficacy and limitations of CAR-M cells remain to be established. To address this issue, in the present study, we compared three intracellular signaling domains (derived from common γ subunit of Fc receptors (FcRγ), multiple EGF-like-domains protein 10 (Megf10), and the CD19 cytoplasmic domain that recruits the p85 subunit of phosphoinositide-3 kinase (PI3K), respectively) for their ability to promote primary CAR-M functions, and investigated the potential synergistic effect between CAR-M and CAR-T cells in their ability to kill tumor cells. We found that CAR-MFcRγ exerted more potent phagocytic and tumor-killing capacity than CAR-MMegf10 and CAR-MPI3K. CAR-M and CAR-T demonstrated synergistic cytotoxicity against tumor cells in vitro. Mechanistically, the inflammatory factors secreted by CAR-T increased the expression of costimulatory ligands (CD86 and CD80) on CAR-M and augmented the cytotoxicity of CAR-M by inducing macrophage M1 polarization. The upregulated costimulatory ligands may promote the fitness and activation of CAR-T cells in turn, achieving significantly enhanced cytotoxicity. Taken together, our study demonstrated for the first time that CAR-M could synergize with CAR-T cells to kill tumor cells, which provides proof-of-concept for a novel combinational immunotherapy.

Evolving Tumor Characteristics and Smart Nanodrugs for Tumor Immunotherapy

“… Could be effective in multiple myeloma and other hematologic cancers with these antigen expressions. [ 132 ] …”

CAR products from novel sources: a new avenue for the breakthrough in cancer immunotherapy

“…The innate ability of CAR macrophages to boost the function of endogenous T cells suggests they could enhance CAR T cell activity. When co-cultured in vitro , CAR macrophages and CAR T cells exhibited remarkable synergy in cytotoxic activity against tumor cells ( 186 ). While CAR macrophages support the function of CAR T cells by upregulating costimulatory ligands (CD86 and CD80), CAR T cells also secrete proinflammatory cytokines that drive CAR macrophages towards an M1 polarization.…”

New cell sources for CAR-based immunotherapy

“…Liu et al compared three common engulfment receptor intracellular domains (FcRγ, Megf10, and PI3K recruitment domain of CD19) in CAR-M for their phagocytosis and killing ability. CAR-M FcRγ showed the most potent phagocytic and killing capacity among the three CAR-Ms [ 202 ]. They also found that CAR-M and CAR-T have a synergistic effect against tumors.…”

“…The synergistic effect of CAR-M and CAR-T against tumor cells probably depends on a feedback loop triggered by the activation of CAR-T. The inflammatory factors secreted by CAR-T augment the cytotoxicity of CAR-M by inducing macrophage M1 polarization and increasing the expression of costimulatory ligands on CAR-M, which may promote the fitness and activation of CAR-T cells in turn [ 202 ]. Klichinsky et al also demonstrated that CAR-Ms constructed with either the CD3ζ or FcRγ activating domain are functionally similar in phagocytosis assays [ 198 ].They generated CAR macrophages (CAR-Ms) by transducing the monocyte-derived pro-inflammatory macrophages with adenoviral vectors encoding anti-HER2 CAR.…”