Evaluation of immunotherapies improving macrophage anti-tumor response using a microfluidic model

Tumor-on-a-chip models are rapidly coming to the fore as a promising platform to accurately mimic tumor biology. These models overcome ethical concerns of animal usage in research, and are of particular use in the field of immuno-oncology, as there are substantial interspecies differences in how cells of the immune system operate. Additionally, they allow a human-centered investigation of novel immunotherapeutic approaches. Here, we report a new application of a microfluidic tumor-on-a-chip system and show its utility by investigating macrophage responses in the context of a promising therapeutic approach that combines anti-epidermal growth factor receptor (EGFR) IgA with an anti-CD47 innate immune checkpoint inhibitor. We report a novel on-chip microscopy-based antibody-dependent cellular phagocytosis (ADCP) assay with human M1-like pro- or M2-like anti-inflammatory macrophages and tumor cells in a collagen matrix. The tumor microenvironment was further characterized by ELISA for secreted factors in the culture medium and through endpoint analyses of gene expression by RT-qPCR. Employing the novel on-chip assay, we show for the first time that the combination of anti-EGFR IgA and a CD47 checkpoint inhibitor synergistically activate macrophage phagocytic function to specifically kill cancer cells, especially for M2-like macrophages. We further demonstrate that the checkpoint inhibition is responsible for elevated secretion of inflammatory cytokines such as TNFα and IL-6, and tends to elevate expression of genes regulating both inflammation (IL-1β) and phagocytic function (CD209), particularly in M2-like macrophages. Taken together, we demonstrate a novel on-chip ADCP assay compatible with multi-parameter characterization of the tumor microenvironment on-chip and demonstrate its utility for yielding novel insights regarding innate immunotherapy combinations.