Tumor implantation site dictates the immune landscape of syngeneic mouse models of head and neck cancer.

Syngeneic mouse models are widely used to study immune-mediated tumor responses. While these models are typically implanted in the flank of the mouse, some experimental setups require alternative sites of tumor implantation, such as the foot. It remains unclear how tumors in the flank and the foot differ in terms of immune cell infiltration, thus introducing an unresolved variable in the interpretation of studies applying these two distinct models. To address this, we compared immune cell profiles in foot and flank tumors using the syngeneic carcinogen-induced oral carcinoma cell lines, MOC1 and MOC2. Tumors were digested into single-cell suspensions and analyzed for infiltrating immune cells using spectral flow cytometry. Our findings reveal substantial location-dependent differences in tumor growth and immune cell infiltration, and demonstrate that implantation site is not a neutral experimental parameter but a determinant of the immune landscape shaped by tumor progression. By clarifying how anatomical context influences immune cell infiltration in a syngeneic model, we can support better alignment and hopefully reproducibility between experimental design and biological questions. The variations we find may have important implications for studies on immune-mediated mechanisms of anticancer treatments and should be considered when determining the desired model for such future investigations.