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‐γ

Cytotoxic T lymphocytes (CTL) have previously been isolated from peripheral blood of patients with renal cell carcinoma (RCC). The CD8‐positive CTL line MZ1257‐CTL‐5 (CTL‐5) has been shown to lyse autologous cultured RCC cells in an HLA‐A2 restricted fashion. Allogeneic, HLA‐A2‐matched RCC and melanoma cell lines were also lysed by CTL‐5, suggesting 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 molecules. Peptides were acid‐eluted from various cell lines, separated by reversed phase high performance liquid chromatography (RP‐HPLC), and assessed for their ability to reconstitute the CTL‐5‐defined epitope by pulsing the peptides on HLA‐A2 positive antigen‐processing mutant cell line CEM × 721.174.T2 (T2). Peptides eluted from allogeneic HLA‐A2‐matched RCC and melanoma cell lines exhibited the CTL‐5‐defined epitope in the same HPLC fractions as peptides derived from the autologous RCC line. Renal cancer and melanoma cells preincubated with interferon‐γ (IFN‐γ) resulted in an additional peak of reconstitution activity in both cell types. This second lytic peak was also observed when high amounts of autologous RCC cells were used for peptide preparation without IFN‐γ pretreatment, indicating that IFN‐γ increases the amount of MHC class I/peptide complexes per cell, rather than inducing a neo‐epitope.