DLL4 overexpression increases gastric cancer stem/progenitor cell self‐renewal ability and correlates with poor clinical outcome via Notch‐1 signaling pathway activation

Gastric cancer is one of the most common malignant diseases, and poses a serious threat to the quality of human life. Gastric cancer stem/progenitor cells (GCSPCs) have critical effects on tumor formation, affecting specific features of self‐renewal and differentiation and playing a critical role in metastasis. The Notch‐1 pathway is crucially important to GCSPCs and is regulated by DLL4. In this study, DLL4 and Nestin levels were measured in 383 gastric cancer tissue samples by immunohistochemistry, and the clinico‐pathological features of patients assessed. After DLL4 silencing in selected gastric cancer cell lines, the expression of GCSPC markers and colony formation ability were analyzed and the self‐renewal and differentiation capacities of the cells were evaluated. The relationship between DLL4 levels and Notch‐1 signaling pathway effector amounts was assessed via Western blotting and immunofluorescence. Finally, the tumor formation ability of the gastric cancer cells was evaluated with different levels of DLL4 and multiple cell densities in vivo. Our results indicate that DLL4 expression is associated with TNM stage and cancer metastasis, with high amounts of DLL4 leading to poor outcome. DLL4 silencing inhibited the self‐renewal ability of GCSPCs and increased their multidifferentiation capacity, resulting in reduced GCSPC ratios. DLL4 knockdown also blocked the Notch‐1 pathway, weakening invasion ability and resistance to 5‐FU chemotherapy. In vivo, DLL4 silencing inhibited the tumor formation ability of GCSPCs. In conclusion, DLL4 affects GCSPC stemness, altering their pathological behavior. DLL4 silencing inhibits GCSPC metastatic potential both in vitro and in vivo by impeding Notch‐1 signaling pathway activation, indicating that DLL4 may be a new potential therapeutic target.