Introduction: Glioblastoma Multiforme (GBM) is the most common primary malignant tumor of the central nervous system. GBM patients manifest as immunosupressed both systemically and locally. Impaired humoral as well as cellular immunity with impaired local cytotoxic T-cell reaction and recruitment is known, due in part to the immunosuppressive nature of the tumor milieu. The immunoprofile of GBM is not well characterized. Although melanoma and GBM are both neuroectodermally originated tumors, sharing differentiation/other antigens, only the immune profile of melanoma has been well-characterized. In this study we characterized HLA-A2 restricted melanoma associated peptides presentation on GBM cell lines and solid tumor samples from GBM patients.
Methods: RNA analysis, flow cytometry, Western blotting, mass spectroscopy and Cytotoxic T lymphocytes toxicity assay results were compared to those of immunohistochemistry with engineered antibodies bearing specificity of T-cell receptor constructed in this paper. These antibodies enable us to directly analyze HLA-A2 restricted peptides on cell surface of GBM and melanoma. Four melanoma associated differentiation antigens were targeted: MART-1, Tyrosinase, Gp100 and MAGE-A1.
Results: The presentation of HLA-A2/MART-1(26-35, A27L) complexes on the surface of U-251MG GBM cell line was relatively low and that of the HLA-A2/gp-100(209-217, T210M) and HLA-A2/MAGE-A1(278-286) was moderate. HLA-A2/Tyrosinase(369-377) was presented in relatively high levels on GBM cell lines (a finding corroborated by mass spectrometry analysis) and was also present on human GBM tumor samples; this was inconsistent with our results from cytolytic T-cell assay which may suggest non-to-low presentation of HLA-A2/Tyrosinase(369-377) complex. This inconsistency probably stems from presentation levels which, albeit being relatively high, are not sufficient to enable effective lysis of target cells, particularly because the anti-Tyrosinase CTL clones have low avidity and therefore require higher antigen concentrations to effectively mediate lysis.
Conclusions: Our profiling sheds light on the immunological profile of GBM and its evolution and may create new targets for immunotherapy.
Patient Care: developing better understanding and immunotherapy for GBM
Learning Objectives: developing better understanding and immunotherapy for GBM