Tumor associated antigens in human renal cell carcinoma: MHC restricted recognition by cytotoxic T lymphocytes.

Abstract

Based on previous studies in human melanoma leading to the molecular cloning of genes encoding peptide antigens recognized by MHC-restricted cytotoxic T lymphocytes (CTL) we extended our efforts to renal cancer systems established in tissue culture. In two patients we obtained stable CD8+ CTL clones with high cytolytic activity for the corresponding autologous tumor cell line in vitro. Neither autologous EBV-transformed B lymphocytes or PHA-activated PBL nor natural killer targets K562 were lysed by these CTL clones. MZ1257-RCC CTL5-30 lysed autologous tumor cells as well as normal kidney cell cultures in an HLA-A2 restricted fashion. Further specificity analysis showed cross reactivity with HLA-A2 matched renal cancer cell lines, melanoma cell lines and tumor cell lines of other origins. HLA-A2 negative target cells were not lysed. The restriction element for T cell recognition in another renal cancer system, MZ1973-RCC, appeared to be HLA-B8 as tested with CTL 5-10. Crossreactivity of CTL 5-10 was documented with one HLA-B8 positive RCC line. Tumor cell lines of other origin were not lysed by CTL 5-10. For further study of CTL-defined epitopes, peptides were extracted from tumor cell lines. Peptides from cultured cell lines were acid-eluted and fractionated by reversed phase HPLC. The peptide fractions were tested in cytotoxicity assays for their ability to reconstitute RCC epitopes by addition to the HLA-A2.1 positive antigen processing mutant cell line 721.124xCEM.T2. One HPLC peak was identified containing an epitope for the HLA-A2 restricted MZ1257-RCC CTL 5-30. These peptide epitopes were present in the autologous renal cancer cell line MZ1257-RCC as well as in an allogeneic HLA-A2 positive RCC cell line MZ1973 and melanoma cell line SK29-MEL, but were absent in peptides eluted from autologous EBV-B cells. We conclude that renal cell carcinoma may induce autologous CTL. Epitopes recognized by MHC-restricted CTL on RCC may be shared by HLA-matched allogeneic renal cancer or even tumors of other origin, such as melanoma. The current challenge is the determination of the amino acid sequences of these CTL-defined peptides as a step to further characterize the nature of these tumor associated antigens.