Chimeric antigen receptors that trigger phagocytosis

Our immune system constantly patrols our body, looking to eliminate cancerous cells and harmful microbes. It can spot these threats because it recognizes certain signals at the surface of dangerous cells. However, cancer cells often find ways to ‘hide’ from our immune system. Chimeric antigen receptors, or CARs, are receptors designed in a laboratory to attach to specific proteins that are found on a cancer cell. These receptors tell immune cells, such as T cells, to attack cancers. T cells that carry CARs are already used to treat people with blood cancers. Yet, these immune cells are not good at penetrating a solid tumor to kill the cells inside, which limits their use. Macrophages are a group of immune cells that can make their way inside tumors and travel to cancers that the rest of the immune system cannot reach. They defend our body by ‘swallowing’ harmful cells. Would it then be possible to use CARs to program macrophages to ‘eat’ cancer cells? Morrissey, Williamson et al. created a new type of CARs, named CAR-P, and introduced it in macrophages. These cells were then able to recognize and attack beads covered in proteins found on cancer cells. The modified macrophages could also limit the growth of live cancer cells in a dish by ‘biting’ and even ‘eating’ them. While these results are promising in the laboratory, the next step is to test whether these reprogrammed macrophages can recognize and fight cancers in living animals.