Specific peptide‐mediated immunity against established melanoma tumors with dendritic cells requires IL‐2 and fetal calf serum‐free cell culture

• Published in: European journal of immunology 2002-01, Vol.32 (1), p.122-127
• Main Authors: Eggert, Andreas O., Becker, Jürgen C., Ammon, Michael, McLellan, Alexander D., Renner, German, Merkel, Angela, Bröcker, Eva‐B., Kämpgen, Eckhart
• Format: Article
• Language: English
• Subjects: Animals; Antigens, Neoplasm - immunology; Antigens, Neoplasm - therapeutic use; Bone Marrow Cells - immunology; Culture Media, Serum-Free; Dendritic cell; Dendritic Cells - cytology; Dendritic Cells - immunology; IL‐2; Immunotherapy; Interleukin-2 - administration & dosage; Interleukin-2 - immunology; Intramolecular Oxidoreductases - immunology; Intramolecular Oxidoreductases - therapeutic use; Melanoma; Melanoma, Experimental - prevention & control; Mice; Mice, Inbred C57BL; Neoplasm Metastasis; Peptides - immunology; Peptides - therapeutic use; Serum Albumin, Bovine; Tumor Cells, Cultured; Tyrosinase‐related protein 2; Vaccination
• ISSN: 0014-2980; 1521-4141
• DOI: 10.1002/1521-4141(200201)32:1<122::AID-IMMU122>3.0.CO;2-C

Melanoma, despite its aggressive growth characteristics, is an antigenic tumor expressing several characterized neo‐ and differentiation antigens. Dendritic cells (DC) when pulsed with definedpeptides have been shown to effectively induce melanoma‐specific T cell responses in humans and mice. These protect animals from challenge with melanoma, but so far have failed to induce significant tumor regressions. To study the efficacy of DC‐based anti‐tumor vaccinations, we set up a therapeutic model using C57BL/6J mice with established pulmonary and subcutaneous metastases induced by the B16‐melanoma cell line B78‐D14. Mice were vaccinated twice with 20,000 antigen‐presenting cells, either bone marrow‐derived DC or epidermal Langerhans cells (LC), which were loaded with the tyrosinase‐related protein 2 (TRP2) peptide. Generally, DC cultured with fetal calf serum (FCS) induced a dominant unspecific response. This was not seen using LC cultured without serum; however, vaccination with TRP2‐loaded FCS‐free LC alone failed to influence the growth of established B16 tumors. A reproducible reduction of tumor size and weight was only obtained if LC vaccinations with TRP2 were followedby a 5‐day treatment of mice with 200,000 IU IL‐2 intraperitoneally twice/daily. Omitting the TRP2 peptide abolished the efficacy of this combined treatment, demonstrating the crucial role of priming a melanoma‐specific T cell response. Microcytotoxic assays performed with spleen‐derived T cells and melanoma as well as congenic fibroblast lines as targets confirmed the TRP2‐dependent specificity of LC‐induced immune responses. Thus, despite the fact that tumor‐specific T cells were primed, an additional IL‐2‐dependent stimulus was needed to translate this immune response into a therapeutic effect against established tumors.