Expression of complement regulating factors in gastric cancer cells

Aims: To investigate the deposition of complement components, C3d and C5b-9, and the expression of complement regulating factors (S protein, membrane cofactor protein (MCP; CD46), protectin (CD59), decay accelerating factor (DAF; CD55), and type 1 complement receptor (CRI; CD35)) in gastric cancers. Methods: Specimens of gastric cancer were examined by immunohistochemistry and immunoelectron microscopy. Results: Four complement regulating factors (S protein, MCP, protectin, and DAF) were expressed on gastric cancer cells, in ultrastructurally localised areas on the cell membrane. CRI was not expressed. The staining intensity of DAF in both differentiated and undifferentiated adenocarcinomas was significantly higher than in histologically normal gastric epithelium. Furthermore, the staining intensity of DAF in gastric cancers showing a diffusely infiltrating growth pattern was higher than in gastric cancers showing an expanding growth pattern. Conclusions: These data indicate that DAF may play a role in cancer cell infiltration and resistance in tumour cells.