Eosinophil ablation and tumor development.

Tissue eosinophilia in squamous cell carcinoma has long been recognized; however, the role of eosinophils in tumor development remains unclear. Studies have reported both favorable and unfavorable prognoses for patients with tumors exhibiting tumor-associated tissue eosinophilia (TATE). This study seeks to elucidate the potential role of the eosinophil in squamous cell carcinoma development and provide an experimental model for future studies. The carcinogen-induced hamster oral cancer model was found to fulfill these objectives. Eosinophils progressively infiltrate into this carcinogen-induced oral cancer model. We now demonstrate that TATE is completely abolished by the use of an anti-interleukin-5 monoclonal antibody (mAb) preparation, TRFK-5. Clinical observations revealed that TRFK-5-treated hamsters exhibited smaller tumor burden and delayed onset of tumor development. The results suggest that anti-interleukin-5 antibody treatment may delay and/or inhibit tumor development, and that eosinophils may have a tumor-promoting role.