Multisite metastatic atlas of gastric cancer identifies C/EBPβ as a regulator promoting liver metastasis

Background The role of intrinsic tumour heterogeneity in driving organ-tropic metastasis in gastric cancer remains underexplored. It is unclear whether the metastatic potential to specific organs is partly associated with pre-existing molecular features of the primary tumour. Objective This study aimed to investigate whether intrinsic tumour features are associated with an enhanced propensity for liver metastasis in gastric cancer and to identify the key transcriptional regulators and downstream mechanisms contributing to this organ-specific dissemination. Design We performed single-cell RNA sequencing (scRNA-seq) on 137 primary and metastatic samples obtained from 53 patients to generate a comprehensive multisite metastatic discovery single-cell atlas and used an independent treatment-validation cohort and 10 public scRNA-seq datasets for validation. Results We constructed the largest multisite metastatic single-cell atlas of gastric cancer to date and identified CCAAT/enhancer-binding protein beta (C/EBPβ), a transcription factor involved in early liver development, as a key regulator associated with liver metastatic propensity. Elevated C/EBPβ expression in primary tumours from patients with or subsequently developing liver metastases across multiple GI cancers further supports its conserved association with liver-directed dissemination. Mechanistically, C/EBPβ promotes tumour-cell adrenomedullin (ADM) secretion to disrupt endothelial junctions via CALCRL, thereby facilitating intravasation. In parallel, C/EBPβ induces C3 expression in tumour cells, activating C3AR1 on macrophages to promote an immunosuppressive macrophage state and support immune evasion during extravasation. Conclusions Our findings establish C/EBPβ as both a candidate biomarker associated with liver metastasis risk and a potential therapeutic entry point while highlighting the ADM–CALCRL and C3–C3AR1 axes as candidate targets for intercepting liver metastatic progression.