PLXNB1/SEMA4D signals mediate interactions between malignant epithelial and immune cells to promote colorectal cancer liver metastasis

Distal metastases result from metastatic microenvironment and tumour epithelial cell interactions, the cellular heterogeneity of primary colorectal cancer (CRC) and liver metastases (LM) was evaluated by integrating single-cell sequencing data, and the collected gene expression data from metastatic epithelial cell subsets was used to construct a prognostic model and to identify intercellular receptor-ligand interactions between epithelial and immune cells in CRC and LM. Multiplex immunofluorescence staining, and in vitro wound healing, cell migration and cell apoptosis assays were performed to further explore the biological relevance of identified potential regulatory molecules. In this study, approximately 17 epithelial cell subtypes were detected, with Epi-11 cells being highly expressed in LM tissues compared with CRC samples. Furthermore, patients with high expression of the metastasis-related genetic profile of Epi-11 had a poorer prognosis. By predicting receptor–ligand interactions, Epi-11 cells were found to interact more with myeloid and T/natural killer cells in LM tissues when compared to primary CRC samples, which was mediated by the PLXNB1/SEMA4D axis. In addition, high SEMA4D expression was correlated with decreased overall survival of patients with CRC, whereas PLXNB1 was not. SEMA4D knockdown prevented the migration and promoted the apoptosis of HCT116 cells in vitro. In summary, Epi-11 cells, an important subset of epithelial cells, may drive the LM of CRC and act by crosstalk with immune cells through the PLXNB1/SEMA4D signalling axis.