Cytotoxic chemotherapy in a 3D microfluidic device induces dendritic cell recruitment and trogocytosis of cancer cells.

Cytotoxic chemotherapy that kills cancer cells can also elicit anti-tumor immune responses. Therefore, understanding the immunogenic context of cytotoxic chemotherapy can improve combination immunotherapies. In this study, we sought to improve our understanding about dendritic cell (DC) dynamics in cytotoxic chemotherapy-treated tumor tissues by developing 3D microfluidic devices that enable high-resolution visualization of cellular dynamics. Specifically, microfluidic chips mimicking 3D tumor tissues were fabricated and used. Collagen gel blocks encapsulating cancer cells in microfluidics were treated with various concentrations of oxaliplatin (OXP). Then, DCs were attached on the side of the collagen gel blocks, and migration of DCs within the 3D gels was quantitatively analyzed. Interactions between OXP-treated cancer cells and DCs were observed by high-resolution time-lapse imaging. Active infiltration of DCs was predominantly observed when OXP was administrated, indicating OXP-treated cancer cells release factors promoting DC motility. The highest frequency of DC recruitment was detected at a moderate OXP concentration, suggesting that optimizing the dosage of cytotoxic chemotherapy is crucial in order to improve immunogenic cell death (ICD). High-resolution video microscopy revealed that DCs employ trogocytosis to disassemble dying/dead cancer cells and acquire antigens, as opposed to phagocytosing the entire cancer cells. Microfluidic chip-based observations may provide new insights for the design of new therapeutic strategies to combine chemotherapy and immunotherapy.