Previously, we utilized the MKN45 cell line to establish orthotopic mouse models of gastric cancer and labeled them with a humanized anti-CEA antibody (M5A) conjugated with a NIR 800 nm dye (M5A-IR800).28 Our findings using the cell line demonstrated that the conjugate was able to brightly label both primary gastric tumors and peritoneal metastases with TBRs greater than four times that of the control. This evidence concerns the gene CEACAM5 and gastric cancer.