Abstract 515: Generation of MAGE-C2/CT10-specific T cell clones for immunotherapy of multiple myeloma

Abstract

Abstract Objective Multiple myeloma (MM) is an incurable neoplasm derived from bone marrow-residing malignant plasma cells. The median life expectancy of MM patients ranges between 3 and 5 years despite the application of conventional chemotherapy including novel agents as well as stem cell transplantation (SCT). Cancer-testis (CT) antigens such as MAGE-C2/CT10 are commonly and specifically expressed in myeloma and, therefore, represent attractive target structures for T cell-based immunotherapies. Methods We screened sera of MM-patients for MAGE-C2/CT10-specific IgG antibodies in an ELISA using recombinant full-length protein. In sera-positive patients frequencies of MAGE-C2/CT10-specific CD4+ and CD8+ T cells were determined following a single cycle of in vitro presensitization of peripheral T cells using a panel of overlapping 20mer peptides spanning the complete sequence of MAGE-C2/CT10. In an IFN-gamma-ELISPOT, which served as a read-out assay, presensitized T cells were re-exposed to MAGE-C2/CT10 peptides pulsed on autologous APC (PHA-stimulated CD4+ T cells [T-APC] or EBV-transformed B-lymphocytes). Stimulated T cells responding to MAGE-C2/CT10 underwent single-cell FACS-sorting of live IFN-gamma secreting T cells using a cytokine secretion assay. After generation of MAGE-C2/CT10-specific CD4+ and CD8+ T cell-clones we identified the composition of the specific T-cell-receptors (TCR) and amplified the receptor chains via PCR. Jurkat-cells were transduced with the specific TCR and specifity and affinity of the resulting genetically modified T cells was evaluated. Results In all 5 of 7 MM-patients with an antibody response against MAGE-C2/CT10 we also detected significant T cell responses against the same antigen. All of these patients evidenced MAGE-C2/CT10 CD4+ T cells and 3/5 patients also showed concomitant CD8+ T cell responses against MAGE-C2/CT10. Overall, CD8+ T cell responses were directed against a total number of 5 different epitopes of MAGE-C2/CT10 whereas CD4+ T cells recognized a total of 13 single peptide sequences. Interestingly, in one patient CD4+ and CD8+ T cells recognized the same MAGE-C2/CT10 20mer peptide. From those myeloma patients evidencing T cell responses against MAGE-C2/CT10 we were able to generate a total number of 44 T cell-clones specific for 8 different epitopes of the CT antigen. Until now, we have identified and cloned the specific TCR of 7 T cell clones. Preliminary experiments suggest that Jurkat cells transduced with the specific TCR recognize naturally processed MAGE-C2/CT10 and are of high avidity. Conclusions Our results demonstrate that the CT antigen MAGE-C2/CT10 induces spontaneous antibody as well as CD4+ and CD8+ T cell responses in myeloma patients. Cloning of these spontaneously occurring T cells seems to be an efficient way to generate TCR-transduced T cells for the MAGE-C2/CT10-specific immunotherapy of MM. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 515. doi:1538-7445.AM2012-515