Efficient tumor T-cell infiltration is crucial for the effectiveness of T-cell-based therapies against solid tumors. Eosinophils play crucial roles in recruiting T cells in solid tumors. Our group has previously generated induced eosinophils (iEOs) from human pluripotent stem cells and exhibited synergistic efficacy with CAR-T cells in solid tumor inhibition. However, administrated eosinophils might influx into inflammatory lungs, posing a potential safety risk. Mitigating the safety concern and enhancing efficacy is a promising development direction for further application of eosinophils.

Our study provides a novel approach to alleviate the potential safety concerns associated with eosinophils while increasing T-cell infiltration in solid tumors. This finding offers a prospective strategy for incorporating eosinophils to improve CAR-T-cell immunotherapy for solid tumors in the future.

We developed a new approach to generate eosinophils with enhanced potency from human chemically reprogrammed induced pluripotent stem cells (hCiPSCs) with the Toll-like receptor (TLR) 7/8 signaling agonist R848.

R848-activated iEOs (R-iEOs) showed significantly decreased influx to the inflamed lungs, indicating a lower risk of causing airway disorders. Furthermore, these R-iEOs had enhanced anti-tumor functions, preferably accumulated at tumor sites, and further increased T-cell infiltration. The combination of R-iEOs and CAR-T cells suppressed tumor growth in mice. Moreover, the chemo-trafficking signaling increased in R-iEOs, which may contribute to the decreased lung influx of R-iEOs and the increased tumor recruitment of T cells.