PURPOSE:
To optimize the combination of ionizing radiation and cellular immunotherapy using a preclinical autochthonous model of prostate cancer.
METHODS AND MATERIALS:
Transgenic mice expressing a model antigen under a prostate-specific promoter were treated using a platform that integrates cone-beam CT imaging with 3-dimensional conformal therapy. Using this technology we investigated the immunologic and therapeutic effects of combining ionizing radiation with granulocyte/macrophage colony-stimulating factor-secreting cellular immunotherapy for prostate cancer in mice bearing autochthonous prostate tumors.
RESULTS:
The combination of ionizing radiation and immunotherapy resulted in a significant decrease in pathologic tumor grade and gross tumor bulk that was not evident with either single-modality therapy. Furthermore, combinatorial therapy resulted in improved overall survival in a preventive metastasis model and in the setting of established micrometastases. Mechanistically, combined therapy resulted in an increase of the ratio of effector-to-regulatory T cells for both CD4 and CD8 tumor-infiltrating lymphocytes.
CONCLUSIONS:
Our preclinical model establishes a potential role for the use of combined radiation-immunotherapy in locally advanced prostate cancer, which warrants further exploration in a clinical setting.
Wada S, Harris TJ, Tryggestad E, Yoshimura K, Zeng J, Yen HR, Getnet D, Grosso JF, Bruno TC, De Marzo AM, Netto GJ, Pardoll DM, DeWeese TL, Wong J & Drake CG.
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