Role of Suppressive Monocytes During Oral Squamous Cell Carcinoma
Background: Oral squamous cell carcinoma (OSCC) is a malignant cancer commonly noted with poor prognosis. Squamous cells form tumor lesions affecting areas within the oral cavity and surrounding head and neck regions. The aggressive nature of OSCC complicated treatment, and is difficult to detect early. Recently, other cancer forms have been associated with immune suppression; the immune response fails to respond and eliminate malignant cells. Immune cells of the myeloid lineage enter the tumor microenvironment but are converted to suppressor type phenotypes, including T cells and monocytes. Monocytes with an immunosuppressive phenotype are known as myeloid derived suppressor cells (MDSC). Tumor cells have been shown to secrete anti-inflammatory mediators through extracellular vesicles that are competent in transforming naive monocytes into MDSC’s/ However, the physical proximity of MDSCs to the tumor microenvironment have not been sufficiently explored. Objective Determine whether myeloid-derived suppressor cells are physically localized to the tumor microenvironment. Tissue from an oral squamous cell carcinoma murine model will be harvested and assessed for relevant MDSC markers by immunohistochemistry.
Design/Methods: Tumor lesions harvested from nude mice injected with model OSCC line TR146 were formalin-fixed and paraffin-embedded (FFPE). Fixed samples were sectioned at 5 µm and prepared for immunohistochemistry. Prepared sections were stained with primary antibody rabbit anti-mouse IBA1 (Wako 019-19741) followed by secondary antibody donkey anti-rabbit IgG H&L (Abcam ab6701). Finally, sections were counter stained and mounted with Vectashield Mounting Reagent with DAPI (Vector #1700) before assessment by fluorescence microscopy.
Results: Preliminary results indicated a colocalization of IBA1+ signal with DAPI nuclear stain on prepared sections.
Conclusions: Presentation of MDSC marker IBA+ in the tumor microenvironment of murine model oral squamous cell carcinoma may suggest the presence of MDSCs in OSCC. However, the physical presence of MDSCs in the tumor microenvironment must be evaluated in human OSCC tissue in order to establish clinical relevance and further application.