CAR-T therapy demonstrated unprecedented success in treating blood cancers but showed limited efficacy on solid tumors. Major challenges including T cells' insufficient infiltration, low persistence and exhaustion in tumor tissues. Tackling these problems will require novel approaches that mobilize a broader immune system beyond T cells. Here we aim to program mast cells into an effective CAR carrier because mast cells are tissue resident, long-lived, and can eliminate tumors by a combination of direct killing and indirect recruiting of tumor-infiltrating T and NK cells. Our goal is to develop CAR-mast cell as a novel cell therapy for solid tumors.