article accepted in Mol Cancer Ther
Combining antibody-directed presentation of IL-15 and 4-1BBL in a trifunctional fusion protein for cancer immunotherapy
Kermer V, Hornig N, Harder M, Bondarieva A, Kontermann RE, Muller D.
Institute of Cell Biology and Immunology, University Stuttgart, Allmandring 31, 70569 Stuttgart, Germany
Taking influence on the cytokine-receptor network that modulates the immune response holds great potential for cancer immunotherapy. Although encouraging results have been obtained by focusing on individual members of the common γ-chain (γc) receptor and tumor necrosis (TNF) receptor family so far, combination strategies might be required to further improve the effectiveness of the antitumor response. Here, we propose the combination of IL-15 and 4-1BBL in a single, tumor-directed molecule. Therefore, a trifunctional antibody-fusion protein was generated, composed of a tumor-specific recombinant antibody, IL-15 linked to a fragment of the IL-15Rα chain (RD) and the extracellular domain of 4-1BBL. In soluble and targeted form, the trifunctional antibody-fusion protein RD_IL-15_scFv_4-1BBL was shown to stimulate activated T cell proliferation and induce T cell cytotoxicity to a similar degree as the bifunctional scFv_RD_IL-15 fusion protein. On the other hand, in targeted form, the trifunctional fusion protein was much more effective in inducing T cell proliferation and IFN-γ release of unstimulated PBMC. Here, the additional signal enhancement could be attributed to the costimulatory activity of 4-1BBL, indicating a clear benefit for the simultaneous presentation of IL-15 and 4-1BBL in one molecule. Furthermore, the trifunctional antibody-fusion protein was more effective than the corresponding bifunctional fusion proteins in reducing metastases in a tumor mouse model in vivo. Hence, the targeted combination of IL-15 and 4-BBL in form of a trifunctional antibody-fusion protein is a promising new approach for cancer immunotherapy.