Specific killing of P53 mutated tumor cell lines by a cross-reactive humanHLA-A2-restricted P53-specific CTL line

p53 is upregulated in the majority of spontaneous tumors and the HLA class I molecule HLA-A2 is expressed by approximately 50% of the caucasians. Pote ntially, these facts make HLA-A2-binding p53 peptides for CTL-inducing immu notherapy applicable to a broad range of cancer patients. In our study, we investigated the CTL-inducing capacity of autologous monocyte-derived dendr itic cells (DC) maturated by exposure to CD40L and pulsed with a pool of 4 wild-type, HLA-A2-binding p53 peptides, and the p53-specific CD8(+) CTL lin es established from healthy HLA-A2-positive donors were characterized. Reac tivity to p53(65-73) and p53(187-197) peptides was obtained in the T-cell l ines. Interestingly, cold target inhibition experiments demonstrated that t he simultaneous recognition of the 2 peptides was the result of crossreacti vity, which was confirmed by killing experiments at the clonal CTL level. F urthermore, 4 HLA-A2(+) p53-mutated tumor cell lines were lysed by the CTL line, indicating that these peptides are endogenously processed and present ed on HLA-A2 molecule. Thus, monocyte-derived DC pulsed with a pool of pept ides are able to induce CTL reactivity to wildtype p53 peptides presented b y several cancer cell lines. In addition, the recognition of 2 different p5 3 peptides by the same CTL clone suggests a promiscuous peptide recognition by the TCR involved. Taken together, these in vitro results suggest that v accination with autologous DC pulsed with multiple p53 epitopes may induce an effective tumor-specific CTL response in vivo with the potential to erad icate p53-upregulated spontaneously occurring tumors. (C) 2001 Wiley-Liss, Inc.