Tumor-immune hybrid cells evade the immune response and potentiate colorectal cancer metastasis through CTLA4

Understanding the metastatic cascade is critical for the treatment and prevention of cancer-related death. Within a tumor, immune cells have the capacity to fuse with tumor cells to generate tumor-immune hybrid cells (THCs). THCs are hypothesized to be a subset of cancer cells with the capacity to enter circulation as circulating hybrid cells (CHC) and seed metastases. To understand the mechanism of THC metastasis, we investigated CHCs in peripheral blood from patients with stage IV colorectal cancer (CRC), as well as THCs in tissues of primary colorectal cancers and their liver metastasis sites using immunofluorescence, spatial proteomic, spatial transcriptomic, molecular classification, and molecular pathway analyses. Our findings indicated a high prevalence of CHCs and THCs in patients with stage IV CRC. THCs expressed CTLA4 in primary CRC lesions and correlated with upregulation of CD68, CD4, and HLA-DR in metastatic liver lesions, which is found in the consensus molecular subtype (CMS) 1 of primary CRC tissue. Pathway analysis of these genes suggested that THCs are associated with neutrophils due to upregulation of neutrophil extracellular trap signaling (NET) and neutrophil degranulation pathways. These data provide molecular pathways for the formation of THCs suggesting fusion with neutrophils, which may facilitate extravasation and metastatic seeding.