RECOGNITION OF HUMAN RENAL-CELL CARCINOMA AND MELANOMA BY HLA-A2-RESTRICTED CYTOTOXIC T-LYMPHOCYTES IS MEDIATED BY SHARED PEPTIDE EPITOPES AND UP-REGULATED BY INTERFERON-GAMMA

Cytotoxic T lymphocytes (CTL) have previously been isolated from perip heral blood of patients with renal cell carcinoma (RCC). The CD8-posit ive CTL line MZ1257-CTL-5 (CTL-5) has been shown to lyse autologous cu ltured RCC cells in an HLA-A2 restricted fashion. Allogeneic, HLA-A2-m atched RCC and melanoma cell lines were also lysed by CTL-5, suggestin g that melanoma and renal cancer share antigenic determinants. The aim of the study was to determine whether RCC and melanoma share peptide epitopes that are recognized by CTL-5 in the context of HLA-A2 molecul es. Peptides were acid-eluted from various cell lines, separated by re versed phase high performance liquid chromatography (RP-HPLC), and ass essed for their ability to reconstitute the CTL-5-defined epitope by p ulsing the peptides on HLA-A2 positive antigen-processing mutant cell line CEM x 721.174.T2 (T2). Peptides eluted from allogeneic HLA-A2-mat ched RCC and melanoma cell lines exhibited the CTL-5-defined epitope i n the same HPLC fractions as peptides derived from the autologous RCC line. Renal cancer and melanoma cells preincubated with interferon-gam ma (IFN-gamma) resulted in an additional peak of reconstitution activi ty in both cell types. This second lytic peak was also observed when h igh amounts of autologous RCC cells were used for peptide preparation without IFN-gamma pretreatment, indicating that IFN-gamma increases th e amount of MHC class I/peptide complexes per cell, rather than induci ng a neo-epitope.