Assessment of CAR-T mediated and targeted cytotoxicity in 3D microfluidic TBNC co-culture models for combination therapy

Chimeric antigen receptor (CAR)-T cell therapy is efficacious against many hematological malignancies; however, their therapeutic application to treat solid tumors presents further challenges. A better understanding of how the solid tumor microenvironment (TME) impacts CAR-T anti-tumor effects would enable the selection of effective combination therapies to decipher the optimal course of treatment for patients and to better engineer CAR-Ts. Classical 2D in vitro models do not provide sufficient recapitulation of the native human TME, and in vivo models, such as patient-derived xenografts, are costly, complex and labor intensive. Here, we present a novel 3D, miniaturized assay for the evaluation of EGFR-targeted CAR-T cell cytotoxicity and specificity on tumor-stroma triple-negative breast cancer models in microfluidic devices. CAR-T cells were shown to home towards EGFR-expressing cancer cells to elicit a cytotoxic effect, whilst leaving low EGFR-expressing fibroblasts viable, an effect which was enhanced through combination anti-PD-L1 therapy and carboplatin chemotherapy. Hence, we propose this proof-of-concept immunoassay as a future preclinical screening tool for the development of novel immunotherapeutics and for use in personalized medicine.