Ephrin A1 Stimulates CCL2 Secretion to Facilitate Pre-metastatic Niche Formation and Promote Gastric Cancer Liver Metastasis.

The liver is a primary target for distal metastasis of gastric cancer (GC). The hepatic pre-metastatic niche (PMN) facilitates crucial communications between primary tumor and liver, thereby playing an essential role in hepatic metastasis. Identification of the molecular mechanisms driving PMN formation in GC could facilitate development of strategies to prevent and treat liver metastasis. Here, we uncovered a role for ephrin A1 (EFNA1) signaling in development of the PMN. EFNA1 overexpression in GC cells significantly increased CCL2 secretion through the Hippo-YAP pathway. Secreted CCL2 activated hepatic stellate cells (HStCs) within the hepatic PMN via the WNT/β-catenin pathway. Inhibition of CCL2 significantly suppressed HStC activation and reduced liver metastasis triggered by EFNA1 signaling in GC cells. Moreover, high CCL2 expression correlated with poor survival in GC patients. Overall, these findings reveal that EFNA1 signaling in GC cells upregulates CCL2, which activates HStCs to engender establishment of a hepatic pre-metastatic niche that supports liver metastasis.