IL15 and medulloblastoma: To assess the ability of PNP hydrogels to improve CAR-T cell treatment of solid tumors in vivo, human B7H3 CAR-T cells (2 million per dose) were encapsulated in PNP-1-5 hydrogels with and without coencapsulated IL-15 (0.25 μg per dose) and administered peritumorally in NSG mice bearing a subcutaneous human medulloblastoma (MED8A) solid tumor (Fig. 5A and figs.