ID #369 Trafficking of cell surface expressed tumour associated antigens contributes to antigen heterogeneity and response to targeted therapies including CAR T cell therapies

Abstract

Therapies targeting cell surface-located receptors hold great promise for the treatment of brain cancer. These include drugs targeting growth factor receptors such as the EGFR and immune cell therapies such as chimeric antigen receptor (CAR) T cell therapies targeting the EphA2 receptor. However, these receptors undergo dynamic trafficking which can alter their cell surface availability and may affect therapeutic response. Importantly, presentation of receptors at the cell surface is regulated by interaction with the tissue microenvironment. We hypothesize that features of the brain tumour microenvironment determine surface receptor density and, consequently, response to therapy. To test this, we used mechanically tuned surfaces, gliomasphere cultures and assembloid cultures consisting of gliomaspheres co-cultured with stem-cell derived brain organoids. We first show that soft brain like-environments induce EGFR internalization and resistance to EGFR inhibitors. We next demonstrate that gliomasphere growth alone is sufficient to trigger receptor internalization. Building on these findings we show that EphA2 CAR T cell efficacy is significantly reduced in gliomasphere and assembloid cultures. Mechanistically, we confirm that ligand-stimulated receptor internalization reduces sensitivity to CAR T cell-mediated killing. Collectively, the data suggest that the brain tissue microenvironment plays a key role in regulating sensitivity to receptor targeted therapies. These findings suggest that strategies to limit receptor internalization may enhance the effectiveness of therapies targeting cell surface receptors in brain cancer.