Chimeric antigen receptors that trigger phagocytosis

Abstract

Chimeric antigen receptors (CARs) are synthetic receptors that reprogram T cells to kill cancer. The success of CAR-T cell therapies highlights the promise of programmed immunity and suggests that applying CAR strategies to other immune cell lineages may be beneficial. Here, we engineered a family of Chimeric Antigen Receptors for Phagocytosis (CAR-Ps) that direct macrophages to engulf specific targets, including cancer cells. CAR-Ps consist of an extracellular antibody fragment, which can be modified to direct CAR-P activity towards specific antigens. By screening a panel of engulfment receptor intracellular domains, we found that the cytosolic domains from Megf10 and FcRɣ robustly triggered engulfment independently of their native extracellular domain. We show that CAR-Ps drive specific engulfment of antigen-coated synthetic particles and whole human cancer cells. Addition of a tandem PI3K recruitment domain increased cancer cell engulfment. Finally, we show that CAR-P expressing murine macrophages reduce cancer cell number in co-culture by over 40%.

Evolution of chimeric antigen receptor (CAR) T cell therapy: current status and future perspectives

“…DSBs are known to cause activation of the tumor-suppressor protein p53, resulting in reduced insertion efficiency of target genes because of cell-cycle arrest or apoptosis (Haapaniemi et al 2018;Ihry et al 2018); moreover, multiple DSBs may cause large deletions (Kosicki et al 2018) or translocations (Qasim et al 2017) of DNA. In addition to improvements in CAR-T therapy, ongoing research seeks to develop novel anticancer cell therapies by introducing CAR genes into various adaptive and innate immune effector cells, such as natural killer (NK) cells, natural killer T (NKT) cells, gamma-delta T (cdT cells), and phagocytic macrophages (Morrissey et al 2018;Saudemont et al 2018). Furthermore, CAR-engineered regulatory T cells (CAR-Treg) or CAR-T cells targeting pathogenic immune cells have been developed for autoimmune diseases and solid organ transplantation (Ellebrecht et al 2016;MacDonald et al 2016).…”

Progress on Modulating Tumor‐Associated Macrophages with Biomaterials

“…Similarly, Morrissey et al introduced chimeric antigen receptors for phagocytosis (CAR‐P) into macrophages . As with CARMAs, the CAR‐P contained: 1) an scFv against CD19 or CD22, 2) a CD8 transmembrane domain, and 3) an intracellular cytoplasmic domain (CD3ζ, Megf10, or FcRγ) to trigger phagocytosis.…”

CARs: Beyond T Cells and T Cell-Derived Signaling Domains

“…This subdivision is not mutually exclusive and mixed phenotypes exist [87]. Macrophages are capable of killing target cells via phagocytosis and trogocytosis (the uptake of severed cell parts) [88][89][90] and MHC-II presentation of antigens taken up, as well as secretion of cytokine and effector molecules [91,92].…”

“…Tumor cell lysis was achieved via CAR-directed phago-and trogo-cytosis [71]. By presenting processed tumor antigens to T cells, CAR macrophages contributed to a poly-antigenic T cell response, reducing the risk of antigen evasion [89,90]. A down-point of macrophages as CAR vehicles is their endogenous resistance to viral infection, resulting in low transduction rates [100].…”

“…Morrissey et al lentivirally transduced murine bone marrow-derived macrophages (BMDMs) with anti-CD19 or anti-CD22 CARs using (amongst others) FcRγ and Megf10 signaling domains ( Figure 1) [90]. These so-called chimeric antigen receptors for phagocytosis (CAR-Ps) enabled macrophages to engulf differently sized bead targets and limit Raji cell growth in vitro [90].…”