Human dendritic cells engineered to secrete interleukin-18 activate MAGE-A3-specific cytotoxic T lymphocytes in vitro.

Adoptive cell transfer (ACT) involves the administration of tumor specific cytotoxic T lymphocytes (CTLs) into a patient to kill cancer cells. Although a promising cancer therapy, limitations on the generation of activated CTLs have restricted ATC's clinical application. Interleukin-18 (IL-18) is an interferon-γ (IFN-γ) inducing factor that plays an important functional role in regulating CTLs. Here, we attempt to use dendritic cells (DCs) modified with a recombinant adenovirus encoding IL-18 (rAd/IL-18) to improve the generation of activated tumor-specific CTLs. These engineered DCs secrete IL-18, increase the expression of co-stimulatory molecules, and enhance the cytotoxic efficacy of melanoma antigen 3 (MAGE-A3)-specific CTLs in vitro. We show that stimulation of CTLs with rAd/IL-18-loaded DCs increases the specific lysis of MAGE-A3-expressing human breast cancer MCF-7 cells, and at the same time increases the production of activated MAGE-A3-specific CTLs. Our results indicate that transducing DCs with rAd/IL-18 increases both the maturation of DCs and the activation level of MAGE-A3-specific CTLs, greatly enhancing the cytotoxic efficacy of CTLs towards tumor cells.