Generation of human tumor-reactive cytotoxic T cells against peptides presented by non-self HLA class I molecules

The cyclin-D1 protein, which was found to be overexpressed in various human tumors, promotes cell cycle progression from the G1 into the S phase. It is normally expressed at low levels in several tissues and is likely to induce immunological tolerance. We have recently shown in a murine system that T cell tolerance to a widely expressed protein was circumvented by raising cytotoxic T lymphocytes (CTL) from MHC-mismatched donors. In this study, we tested whether it is possible to raise human allo-restricted CTL against the cyclin-D1 protein. The human cell line T2 is deficient in the genes encoding the transporter associated with antigen processing (TAP), resulting in inefficient loading of HLA-A2 class I molecules with endogenous peptides. Thus, a large number of A2 molecules can bind exogenously supplied synthetic peptides. Peripheral blood mononuclear cells from HLA-A2-negative donors were stimulated with T2 cells presenting cyclin-D1-derived synthetic peptides. Cloning of bulk cultures revealed that a large proportion of CTL clones were peptide specific. One peptide induced CTL which lysed cyclin-D1-expressing breast cancer cells, but not control Epstein-Barr virus-transformed B lymphoid cells. The results show that HLA-A2-negative donors can be used to isolate tumor-reactive CTL specific for cyclin-D1 peptides presented by HLA-A2 class I molecules.