CAR-T cell-treated tumor-on-chip systems were assessed with regards to the secretion of cytokines IL-2, IL-6, IL-10, TNF-α, IFN-γ, and granzyme B on day 1 (20 h) after CAR-T cell perfusion. To ensure that the cytokines originate from CAR-T cell-tumor interaction, either control T cells or CAR-T cells were perfused through either acellular (empty), mvEC-only, or complete tumor-on-chip setups (mvECs + MDA); n= 2–4 chips. Data are presented as the mean ± SEM. Each red dot represents one chip. The dashed line indicates the upper detection limit.