Characterization of the Tumor Microenvironment in the Mouse Oral Cancer (MOC1) Model after Orthotopic Implantation in the Buccal Mucosa.

Background: Preclinical models are invaluable for studies of head and neck cancer. There is growing interest in the use of orthotopic syngeneic models, wherein cell lines are injected into the oral cavity of immunocompetent mice. In this brief report, we describe injection of mouse oral cancer 1 (MOC1) cells into the buccal mucosa and illustrate the tumor growth pattern, lymph node response, and changes in the tumor immune microenvironment over time. Methods: MOC1 cells were injected into the buccal mucosa of C57BL6 mice. Animals were sacrificed at 7, 14, 21, or 27 days. Tumors and lymph nodes were analyzed by flow cytometry. Results: All mice developed tumors by day 7 and required euthanasia for tumor burden and/or weight loss by day 27. Lymph node mapping showed that these tumors reliably drain to a submandibular lymph node. The proportion of intratumoral CD8+ T cells decreased over time, while neutrophilic myeloid cells increased dramatically. Growth of orthotopic MOC2 and MOC22 also showed similar growth patterns versus published data in flank tumors. Conclusions: When used orthotopically in the buccal mucosa, the MOC1 model induces a robust lymph node response and distinct pattern of immune cell infiltration, with peak immune infiltration by day 14.