Genetically engineering mast cells as effectors for targeted cancer cell cytotoxicity.

Type-I hypersensitivity is a mast cell-mediated degranulation process induced by IgE-antigen recognition. Inspired by this highly specific mechanism, we developed a new cell therapy platform by genetically engineering mouse mast cell line MC/9 to overexpress the cytotoxic proteins perforin and granzyme B (PG-MCs) via lentiviral transduction. In the melanoma model utilizing B16 cells expressing membrane-bound OVA, a polarized degranulation of mast cells towards cancer cells was validated upon the recognition of antigens by anti-OVA IgE. PG-MCs could selectively kill cancer cells via IgE-antigen recognition. The IgE-sensitized PG-MCs administered through an intertumoral route delivered perforin 1 (Prf1) and granzyme B (Gmzb) toward target cells to potentiate anti-tumor efficacy. Moreover, we demonstrated the reprogramming effect of tumor microenvironment by PG-MC-induced hypersensitivity, driving an immune remodeling of the tumor milieu, characterized by the increased lymphocyte infiltration. In addition, this mast cell therapy, in combination with 5- fluorouracil (5-Fu), induced a significant inhibition of tumor growth in a B16-OVA mouse model, which is associated with the depletion of myeloid-derived suppressor cells (MDSCs).