REG4 and gastric cancer: To further confirm whether REG4 colocalizes with GPR37 on gastric cancer cell membrane, confocal microscopy using different fluorescent antibodies for REG4 and GPR37 was performed, the image clearly demonstrated that REG4 colocalized with GPR37 on the cell membrane, and that knockdown of GRP37 prevented REG4 to associate with cell surface (Figure 3D, Supplementary Figure S3B).