HLA-A2-restricted CTL epitopes from human heparanase as novel targets for broad spectrum tumor immunotherapy

Ting Chen, Xu-Dong Tang, Yin Wan, Ling Chen, Song-Tao Yu, Zhen Xiong, Dian-Chun Fang, Guang-Ping Liang and Shi-Ming Yang

Year 2008, Volume 10, Issue 9

Abstract

Peptide vaccination for cancer immunotherapy requires identification of peptide epitopes derived from antigenic proteins associated with tumors. Heparanase is broadly expressed in various advanced tumors and seems to be an attractive new tumor-associated antigen. The present study was designed to predict and identify HLA-A2-restricted CTL epitopes in the protein of human heparanase. For this purpose, HLA-A2-restricted CTL epitopes were identified using the following four-step procedure: (a) a computer-based epitope prediction from the amino acid sequence of human heparanase; (b) a peptide-binding assay to determine the affinity of the predicted protein with the HLA-A2 molecule; (c) stimulation of the primary T-cell response against the predicted peptides in vitro; and (d) testing of the induced CTLs toward different kinds of carcinoma cells expressing heparanase antigens and/or HLA-A2. The results demonstrated that, of the tested peptides, effectors induced by peptides of human heparanase at residue positions 525-533 (PAFSYSFFV, Hpa525), 277-285(KMLKSFLKA, Hpa277) and 405-413 (WLSLLFKKL, Hpa405) could effectively lyse various tumor cell lines that were heparanase positive and HLA-A2 matched. We also found that these peptide-specific CTLs could not lyse autologous lymphocytes with low heparanase activity. Further study revealed that Hpa525, Hpa277 and Hpa405 peptides increased the frequency of IFN-¦Ã-producing T cells as compared to negative peptide. Our results suggest that Hpa525, Hpa277 and Hpa405 peptides are new HLA-A2-restricted CTL epitopes capable of inducing heparanase-specific CTLs in vitro. Because heparanase is expressed in most advanced malignant tumors, Hpa525, Hpa277 and Hpa405 peptide-based vaccines may be useful for the immunotherapy of patients with advanced tumors.

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