SFRP5 inhibits gastric epithelial cell migration induced by macrophage-derived Wnt5a

Secreted frizzled-related protein 5 (SFRP5) is frequently found downregulated in gastric cancer due to SFRP5 gene hypermethylation, and there is a great necessity to elucidate the role of its downregulation in gastric cancer. By binding Wnt molecules, SFRP5 is generally supposed to exert negative effects on Wnt signal pathways widely linked to human cancers. This study found that macrophages over-produced Wnt5a under the stimulation of Lipopolysaccharide (LPS) or Helicobacter pylori, the most common infectious agent in human stomach. Wnt5a-conditioned medium from macrophages enhanced cell migration and CXCR4 expression in either SFRP5-negative gastric epithelial cells (GEC) harboring SFRP5 methylation or SFRP5-positive cells treated with SFRP5 small interfering RNA (siRNA). However, such induced effect was remarkably eliminated by either Wnt5a siRNA in macrophages or treatment with recombinant SFRP5. We also found that Wnt5a-conditioned medium stimulated phosphorylation of c-jun N-terminal kinase (JNK) and c-Jun, and JNK inhibitor SP600125 blocked Wnt5a-induced CXCR4 expression and cell migration in SFRP5-negative cells. Taken together, these findings suggest that epithelium-derived SFRP5 may play a probable defensive role in impeding gastric cancer progression, characteristically by inhibiting GEC migration induced by macrophage-derived Wnt5a via JNK signaling activation.