An organoid-based screen for epigenetic inhibitors that stimulate antigen presentation and potentiate T-cell-mediated cytotoxicity.

In breast cancer, genetic heterogeneity, the lack of actionable targets and immune evasion all contribute to the limited clinical response rates to immune checkpoint blockade therapy. Here, we report a high-throughput screen based on the functional interaction of mouse- or patient-derived breast tumour organoids and tumour-specific cytotoxic T cells for the identification of epigenetic inhibitors that promote antigen presentation and potentiate T-cell-mediated cytotoxicity. We show that the epigenetic inhibitors GSK-LSD1, CUDC-101 and BML-210, identified by the screen, display antitumour activities in orthotopic mammary tumours in mice, that they upregulate antigen presentation mediated by the major histocompatibility complex class I on breast tumour cells and that treatment with BML-210 substantially sensitized breast tumours to the inhibitor of the checkpoint programmed death-1. Standardized measurements of tumour-cell killing activity facilitated by tumour-organoid-T-cell screens may help with the identification of candidate immunotherapeutics for a range of cancers.