Transforming growth factor-beta produced by progressor tumors inhibits, while IL-10 produced by regressor tumors enhances, Langerhans cell migration from skin

The induction of epidermal immunity depends on activation of local dendritic cells (DC), Langerhans cells (LC), to migrate from the skin to local lymph nodes and mature into potent immunostimulatory cells. We have previously shown that progressor skin tumors, which evade immunological destruction, prevent contact sensitizer-induced LC migration from the skin to draining lymph nodes. In contrast, regressor tumors, which evoke protective immunity, did not inhibit DC mobilization. In this study we utilized the skin explant model to determine the factors produced by skin tumors which regulate LC migration from the skin. Supernatants from two progressor squamous cell carcinoma lines both inhibited LC migration, whereas supernatants from two regressor squamous cell carcinoma lines both enhanced LC mobilization. Transforming growth factor (TGF)-beta1 inhibited, while IL-10 enhanced, LC migration from cultured skin. Both reduced the ability of LC to mature into potent allostimulators. Antibody neutralization identified that TGF-beta1 produced by the progressor tumor was responsible for inhibition of LC migration, while IL-10 produced by the regressor tumor enhanced LC mobilization. Thus these studies show that skin tumors influence DC mobilization from tumors by production of cytokines, and that TGF-beta1 is one factor produced by tumors which can immobilize LC and keep them in an immature form. This is likely to be an important mechanism of tumor escape from the immune system as progressor tumors inhibited, while regressor tumors enhanced DC mobilization.