Molecular and functional analysis of tyrosinase-related protein (TRP)-2 as a cytotoxic T lymphocyte target in patients with malignant glioma

Tyrosinase-related protein (TRP)-2 is an immunogenic antigen in melanoma. The authors sought to investigate whether TRP-2 could be a potential target for patients with malignant glioma. RT-PCR analysis demonstrated that TRP-2 was present in 51.2% of primary tumor cell lines derived from patients with glioblastoma multiforme (GBM). The percentage of TRP-2-6b, TRP-2-INT2, TRP-2-LT, and TRP-2-8b isoform expression in all tested GBM cells was 13.9%, 34.9%, 41.9%, and 39.5%, respectively. TRP-2 protein expression was detected in GBM cells and tumor tissues by Western blot and immunohistochemistry. In addition, an HLA-A2-restricted cytotoxic T cell clone that recognizes the TRP-2(180-188) peptide (SVYDFFVWL) specifically lysed the TRP-2 positive GBM cells in a HLA-A2 restricted manner. In addition, the level of TRP-2 mRNA expression, as determined by real-time quantitative RT-PCR, correlated with the level of CTL recognition as measured by IFN-gamma secretion (R = 0.90; p < 0.01). To further test the immunogenicity of TRP-2 in glioma, PBMCs from a healthy donor were primed in vitro using autologous dendritic cells (DCs) pulsed with irradiated GBM cells. These in vitro generated T cells specifically lysed T2 cells pulsed with TRP-2(180-188) peptide and TRP-2 positive GBM cell lines. Most importantly, TRP-2(180-188) specific CTL frequency in four patients' PBMC who were both HLA-A2 and TRP-2 positive was significantly (p < 0.01) increased, respectively, after vaccinations with DCs pulsed with autologous tumor lysate. The authors' studies demonstrate that TRP-2 could be a useful antigen target for monitoring or developing immunotherapeutic strategies for glioma patients.