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Detection of naturally processed and HLA-A1-presented melanoma T-cell epitopes defined by CD8(+) T-cells' release of granulocyte-macrophage colony-stimulating factor but not by cytolysis.

Several antigens, including the products encoded by the genes MAGE-1 and MAGE-3, are recognized on human melanoma cells by HLA-A1, HLA-A2, or HLA-Cw*1601*-restricted T cells on autologous or HLA-matched melanoma cell lines. T-cell recognition of naturally processed MHC class I-presented peptides, or alternatively synthetic peptides derived from MAGE-1 or MAGE-3, leads to cytokine release as well as to a cytotoxic T-cell response in these antimelanoma-directed polyclonal or clonal effector T-cell populations. Recent reports suggest that the activity of T lymphocytes infiltrating melanoma in vivo appears to be impaired. We report here the characterization of the in vitro (in the presence of 6000 IU interleukin 2) expanded tumor-infiltrating lymphocyte (TIL) T-cell line PM2-B2 derived from a patient with rapidly progressing and therapy-resistant head and neck melanoma. The TIL cell line PM2-B2 did not lyse, but instead released granulocyte-macrophage colony-stimulating factor in response to the autologous tumor or HLA-A1-matched allogeneic tumor cell lines. The TIL line PM2-B2 did not kill the MHC class I natural killer/lymphokine-activated killer target cell lines Daudi or K562. The fine specificity of the TIL line PM2-B2 restricted by HLA-A1 was further characterized by evaluating specific granulocyte-macrophage colony-stimulating factor release in response to MHC class I-eluted peptides derived from HLA-A1(+) melanoma cell lines. TIL PM2-B2 failed to recognize the recently described HLA-A1-presented peptides derived from the gene products encoded by MAGE-1 or MAGE-3. PCR-based analysis of the freshly harvested tumor from patient PM2-B2 revealed the presence of message for the melanoma-associated gene products MAGE-1 and MAGE-3, but not for tyrosinase or MART-1/MELAN-A. Acid elution and high performance liquid chromatography fractionation of MHC class I-presented peptides from HLA-A1-matched melanoma cell lines 397 or 888 revealed that TIL PM2-B2 recognized at least three distinct peptide epitopes eluting in high performance liquid chromatographic bioactive fractions 5/6, 36, and 51/52. These bioactive peaks appeared to be shared among HLA-A1(+) melanoma cell lines. We suggest, based on this report, that HLA-A1-presented melanoma-derived peptides (other than those previously reported peptides derived from MAGE-1 or MAGE-3) may represent targets for TIL recognition as defined by cytokine release, but not cytotoxicity. Such an immune response differentially defined by cytokine release, but absent cytotoxic functions, may either reflect the impaired cytolytic function of the TIL population or reflect the inherent nature of HLA-A1-presented melanoma T-cell epitopes leading to cytokine release, but not to a cytotoxic T-cell response. Additionally, this report suggests that the individual T-cell immune response to melanoma may be rather complex, involving diverse T-cell effector functions (e.g., cytotoxicity or cytokine release), each of which should be evaluated in studies of antitumor-specific T-cell reactivity.