CEACAM5 and gastric cancer: Using a humanized anti-CEA antibody (M5A) conjugated with a NIR 800 nm dye (M5A-IR800), we were able to brightly target the tumors and achieve high tumor-to-background ratios.28 In the present study, we obtained two patient-derived gastric cancer samples and demonstrate the applicability of M5A-IR800 to target human gastric cancer.