Targeting primary gastric tumors and peritoneal metastases in cell-derived xenograft mouse models using an anti-mucin-4-antibody conjugated near infrared fluorophore

Introduction: The purpose of the present study is to validate the use of an anti-MUC4 antibody conjugated near infrared dye to target primary and metastatic gastric cancers in nude mouse models. Methods: Subcutaneous models were created in nude mice by injecting 10 6 cells of human gastric cancer cell lines SNU-16 or NCI-N87 into their flanks. These tumors were excised after 2 months and 1 mm 3 fragments were implanted into the stomachs of nude mice to establish orthotopic gastric cancer models of SNU-16 and NCI-N87. Experimental metastasis models were established by injecting 10 6 SNU-16 or 10 6 NCI-N87 cells intraperitoneally in nude mice. 2-3 months after tumor implantation mice were injected via tail vein with a mucin4 antibody conjugated to a near infrared fluorescent dye IRDye800CW (MUC4-IRDye800CW). Mice were sacrificed 72 hours after tail vein injection of 50 µg MUC4-IRDye800CW and imaged with the LI-COR Pearl Imaging System and a Stryker laparoscope. The tumor-to-background ratios (TBR) were calculated by dividing the mean fluorescence intensity of the tumors by that of the surrounding stomach. Histopathological analysis was performed on tumors with immunohistochemical (IHC) staining with anti-mucin-4 and anti-immunoglobulin G (IgG) as a negative control. Results: 20 total mice were imaged, including 14 primary gastric cancer models and 4 intraperitoneal metastatic gastric cancer models. Primary gastric SNU-16 tumors (n = 6) had a mean TBR of 1.99 (SE ± 0.58), and primary gastric NCI-N87 tumors (n = 8) had a mean TBR of 2.81 (SE ± 1.04). Metastatic SNU-16 tumors (n = 3) had a mean TBR of 3.7 (SE ± 0.75), and metastatic NCI-N87 tumors (n = 3) had a mean TBR of 3.91 (SE ± 0.98). Tumor borders were clearly visualized with both Pearl and the Stryker laparoscope fluorescence imaging systems. Representative tumors stained with anti-mucin-4 stained brown while those stained with anti-IgG did not. Conclusions: Anti-MUC4-IRDye800CW can be used to accurately localize both primary and metastatic gastric cancer models in nude mice with fluorescence imaging and is promising for identifying both primary tumor margins and intraperitoneal metastasis intra-operatively.