Machine perfusion and single-cell spatial transcriptome mapping identifies novel immune escape mechanisms in colorectal cancer liver metastasis

Liver metastasis is the terminal stage of colorectal cancer. Immune checkpoint blockade (ICB) has heralded remarkable clinical success across a range of cancer types, but with limited efficacy in replacement-type colorectal liver metastasis (CRLM), the most common and lethal histological subtype. Using a novel human normothermic perfusion model, we demonstrate for the first time, that T-cells preferentially extravasate within the peri-tumoural liver rather than the CRLM. We use single-cell spatial transcriptomics and multiplexed immunofluorescence to validate CRLM T-cell exclusion and show that CRLM endothelia are anergic, lacking key receptors required for T-cell extravasation. CD4 T-cells that extravasate within the peri-tumoural liver are TCR-reactive, yet exhausted, whilst CD4 T-cells within the CRLM demonstrate a stress response, impaired cytokine expression and lack of TCR reactivity. We identify the spatial cellular and molecular interactions underlying these observations, providing novel targets for future attempts to sensitise to immunotherapeutics and a justification for failed ICB efficacy in CRLM.