Therapy of lung metastases through combined vaccination with carcinoma cells engineered to release IL-13 and IFN-γ

TS/A spontaneous mouse mammary adenocarcinoma cells were engineered to release interferon-γ (IFN-γ), a Th1 cytokine (TS/A-IFNγ) and interleukin-13 (IL-13), a Th2 cytokine (TS/A-IL13). Mice bearing lung micrometastases induced by parental TS/A cells received repeated subcutaneous vaccinations with TS/A-IFNγ admixed with TS/A-IL13 engineered cells. This combined treatment cured up to 75% of mice, whereas vaccinations with either TS/A-IFNγ or TS/A-IL13 alone cured only 20-40% of mice. Combined TS/A-IL13 and TS/A-IFNγ therapeutic vaccinations elicited a reactive infiltrate of CD4⁺ and CD8⁺ lymphocytes in lung metastases and an increased production of IFN-γ in the spleen and lung, suggesting a shift of the immune response toward the Th1 type. The type of infiltrating cells along with the lack of efficacy in T cell-deficient mice point to a major role of T cells. In conclusion, no antagonism but a synergistic and effective definitive cure stems from the combined vaccination with tumor cells engineered to release a Th1 and a Th2 cytokine.