<> "The repository administrator has not yet configured an RDF license."^^ . <> . . "Characterization of spontaneous tumor antigen-reactive T cell responses in melanoma patients and treatment of human melanoma with optimized T cell receptor transgenic T cells in a xenotransplantation model"^^ . "One of the leading human malignancies is cancer, a disease characterized by mostly uncontrolled growth of abnormal cells in the body, often forming metastases. It´s interaction with the immune system, that can influence the disease progression, has repeatedly been reported and gained increasing importance over the last decades. However, most of the current immunotherapeutic approaches for cancer treatment are limited, partly due to the immune controlling capacities of tumors. The development of novel experimental approaches and therapeutic strategies, that support and complement the tumor-directed pre-existing abilities of the immune system, will be critical for the success of future cancer immunotherapies. Therefore, and because of the general need of novel treatment strategies, the presented thesis focused on four different approaches to optimize cancer immune therapeutic interventions. Functionally competent tumor-specific memory T cells have been reported to efficiently control tumor growth and be required for a durable prevention of tumor recurrence and metastasis formation. Therefore, the first project dealed with spontaneously induced tumor antigen-reactive memory T cell responses in the peripheral blood (PB) of melanoma and dysplastic nevi patients. Thereby, using a short-term IFNgamma ELISPOT assay, high frequencies of pre-existing T cell responses were detected in both cohorts ex vivo. As antigen-presenting cells, I have used autologous dendritic cells, generated from monocytes which were pulsed with 13 different 50 amino acid long synthetic melanoma polypeptides, derived from immunodominant regions of tumor-associated antigens (TAAs). Thereby, the nature of the identified T cell responses revealed to be polyvalent and HLA-unrestricted. Moreover, the designed polypeptide sequences, that covered MHC class I- and II-restricted epitopes, are optimal for presentation on a wide range of HLA types and therefore, were recognized by CD4+ and CD8+ T cells. I have shown that the long peptide sequence of the NA17-A antigen induce high frequencies of NA17-A-reactive memory T cells, but not NA17-A-specific regulatory T cell (Treg) responses. Thus, particular importance for future vaccination approaches might therefore have to be considered. Furthermore, the demonstration that the TAA-reactive T cell frequencies increased after resection of the non-metastasized tumors or dysplastic nevi indicates that the presence of the lesions controls pre-existing T cell responses. Additionally, these investigations also showed antigen-specific Treg in the PB and revealed that, in some patients, Treg have an immunosuppressive potential. In general, however, an essential role of Treg in controlling spontaneous T cell responses in non-metastasized melanoma and dysplastic nevi patients could not be detected. Based on these findings, besides Treg, the tumor- or lesion-mediated TAA-reactive memory T cell suppression might also be facilitated through other potential effectors of immunosuppression, including combinations of soluble and cellular mediators. Summarized, the investigated polypeptides efficiently elucidated pre-existing T cell responses in melanoma and dysplastic nevi patients and thus indicate that those polyvalent responses could be therapeutically reactivated in consequence of an appropriate peptide vaccination treatment. For the second optimization approach a human melanoma murine xenotransplantation model has been established. Thereby, the in vivo efficiency and biologic relevance of human T cells, which were transduced with functionally expressed, in vitro optimized, T cell receptor (TCR) constructs, specific for the antigens MDM2 or gp100 were investigated. For the first time in vivo, two novel strategies that aimed to avoid hybrid mispaired TCR chain formation and thereby potential autoimmune disease-causing “off-target” reactions were tested. These approaches comprised the molecular design of the TCR alpha/beta interphase and a single chain TCR framework. Thereby, optimized MDM2 as well as gp100 transgenic T cells revealed the ability to significantly control human melanoma tumor growth. Moreover, the engineered T cells persisted in vivo and controlled in the same animals even a secondary tumor growth in a memory T cell-like manner. I could also demonstrate that a combinational treatment of adoptive T cell therapy using TCR gene-modified human T cells with local low dose tumor irradiation (2 Gy), led to an improved T cell targeting into the tumor and additionally further increased the tumor growth control. Consequently, in order to improve adoptive cancer immunotherapeutic approaches the in vivo experiments confirmed the feasibility and efficiency of the applied TCR design. In the third project presented in this thesis, a novel tumor cell-mediated immunosuppressive mechanism, facilitated by the cell adhesion molecules CEACAM6 and L1CAM, was addressed. Thereby, these molecules were detected in various tumor cell lines and using short-term IFNgamma ELISPOT and 51Cr release cytotoxicity assays it could be shown that their specific blockade resulted in increased, functional effector T cell responses. Therefore, in order to modulate the strength of T cell responses against malignant edited tumor cells that escaped immune recognition, CEACAM6 and L1CAM may consequently be attractive targets for novel immunotherapeutic interventions. Finally, to increase the capacity of oncolytic virotherapies, in a fourth project, I optimized the viral transport of the Newcastle disease virus (NDV) to human tumor cells. In this approach, the loading of human T cells with NDV was specified for the first time in an in vitro co-culture system. Moreover, in a “hitchhiking”-like mechanism T cells have shown to be capable to transfer cell surface-attached NDV to MCF-7 tumor cells. In addition, monolayers of tumor cells were efficiently destroyed through oncolytic NDV-modified activated T cells. Based on this combinational therapy, it can be proposed that effector T cells can facilitate as potent carrier vehicles to transport NDV to tumor sites, resulting in focused tumor cell destruction. In summary, the findings of the four different approaches, presented in this thesis, indicate novel perspectives for the optimization of future immunotherapeutic interventions in order to elicit and support protective T cell responses against clinically apparent malignant tumors. "^^ . "2011" . . . . . . . . "Christina"^^ . "Pfirschke"^^ . "Christina Pfirschke"^^ . . . . . . "Characterization of spontaneous tumor antigen-reactive T cell responses in melanoma patients and treatment of human melanoma with optimized T cell receptor transgenic T cells in a xenotransplantation model (PDF)"^^ . . . "Dissertation_Christina_Pfirschke2.pdf"^^ . . . 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"medium.jpg"^^ . . . "Characterization of spontaneous tumor antigen-reactive T cell responses in melanoma patients and treatment of human melanoma with optimized T cell receptor transgenic T cells in a xenotransplantation model (Other)"^^ . . . . . . "small.jpg"^^ . . "HTML Summary of #12944 \n\nCharacterization of spontaneous tumor antigen-reactive T cell responses in melanoma patients and treatment of human melanoma with optimized T cell receptor transgenic T cells in a xenotransplantation model\n\n" . "text/html" . . . "570 Biowissenschaften, Biologie"@de . "570 Life sciences"@en . .