Genetic modification of a carcinoma with the IL‐4 gene increases the influx of dendritic cells relative to other cytokines

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Abstract
Tumor cells genetically modified with certain cytokine genes gain immunogenic properties that allow the development of systemic anti-tumor immunity. Whether different cytokines may influence infiltration of transduced tumors by dendritic cells (DC) has not been investigated. Therefore, we analyzed the C26 murine colon carcinoma genetically modified to release interleukin (IL)-2, IL-4, IL-12, granulocyte colony-stimulating-factor (CSF) or granulocyte-macrophage (GM)-CSF for immunostaining with the monoclonal antibody NDLC145 recognizing the DEC205 determinant which, on tumor sections, is virtually restricted to DC. Infiltrating leukocytes were also characterized for expression of co-stimulatory molecules like CD54, CD86 and major histocompatibility complex class II. The intratumoral DC content was dependent on the type of transduced cytokines with C26/IL-4 being the most abundant in DEC205+ cells. The effect of IL-4 in recruiting DC did not depend on the type of tumor since it was confirmed in the TSA mammary carcinoma. In comparison with C26/GM-CSF, C26/IL-4 had more B7.2+ cells but less Ia+ cells. Furthermore, the hypertrophic skin overlaying tumors producing GM-CSF showed numerous Langerhans cells stained by NDLC145 and the draining lymph nodes showed abundance and paucity of DC in C26/GM-CSF and C26/IL-4, respectively. When injected into the ear pinna, C26/GM-CSF stimulated, whereas C26/IL-4 inhibited DC-mediated priming of delayed-type hypersensitivity reaction by 2,4-dinitro-1-fluorobenzene. These findings prove that transduced cytokines differently influence DC recruitment at the tumor site and DC function in nearby tissues. Along with the other leukocytes and their secondary produced cytokines, DC create an environment in which T cells can be differently modulated. Such a phenomenon may have implications on genetic modification of tumor cells to be used as cancer vaccine.