Histone-lysine N-methyltransferase EZH2 (165-174)

Analyses on reactivity of anti-cancer cytotoxic T lymphocytes (CTLs) and clinical application of peptide-based anti-cancer vaccine have been mainly focused on patients with HLA-A2 or -A24 alleles. In this study, we identified an enhancer of zeste homolog (EZH) 2-derived peptide applicable for anti-cancer vaccine for prostate cancer patients with HLA-A3 supertype alleles. Five EZH2-derived peptides that were prepared based on the binding motif to the HLA-A3 supertype alleles (HLA-A11, -A31, and -A33) were functionally screened for their potential to induce peptide-specific CTLs from peripheral blood mononuclear cells (PBMCs) of HLA-A3 supertype allele(+) prostate cancer patients. As a result, EZH2733-741 peptide was found to efficiently induce peptide-specific CTLs. The EZH2733-741 peptide-stimulated and purified CD8(+) T cells from PBMCs of HLA-A3 supertype allele(+) prostate cancer patients showed higher cytotoxicity against HLA-A3 supertype allele-expressing LNCaP prostate cancer cells than against parental LNCaP cells. This cytotoxicity against HLA-A3 supertype allele-expressing LNCaP cells was partially but significantly inhibited by the addition of EZH2733-741 peptide-pulsed competitive cells. These results indicate that the EZH2733-741 peptide could be a promising candidate for peptide-based immunotherapy for HLA-A3 supertype allele(+) prostate cancer patients.

Background: Parathyroid hormone-related protein (PTHrP) is produced by cancer cells and has been suggested to be responsible for malignancy-associated hypercalcemia and osteolysis after bone metatsases. Therefore, PTHrP is a promising target in the treatment of metastatic prostate cancer. Methods: Seven PTHrP-derived peptides were prepared based on the HLA-A2 binding motif. These peptide candidates were screened by their ability to induce peptide-specific cytotoxic T lymphocytes (CTLs), and their ability to be recognized by immunoglobulin G (IgG). Results: Both the PTHrP59-67 and PTHrP42-51 peptides were found to efficiently induce peptide-specific CTLs from peripheral blood mononuclear cells of HLA-A2+ prostate cancer patients with several HLA-A2 subtypes. These CTLs showed HLA-A2-restricted cytotoxicity toward prostate cancer cells. IgG reactive to the PTHrP42-51 peptide was frequently detected in prostate cancer patients. Conclusions: These results indicate that these two new PTHrP peptides will be useful in the peptide-based immunotherapy of HLA-A2+ prostate cancer patients, especially those with bone metastases.

Background: Antigens overexpressed in metastatic prostate cancer are appropriate targets in anti-cancer immunotherapy, and one candidate is the polycomb group protein enhancer of zeste homolog 2 (EZH2). Methods: Eleven EZH2-derived peptides were prepared based on the HLA-A24 binding motif. These peptide candidates were screened first by their ability to be recognized by immunoglobulin G (IgG), and then by their ability to induce peptide-specific cytotoxic T lymphocytes (CTLs). Results: IgGs reactive to three EZH2 peptides (EZH2-243 to -252, EZH2-291 to -299, and EZH2-735 to -;742) were detected in the plasma of almost half of prostate cancer patients. Among them, the EZH2-291 to -299 and EZH2-735 to -742 peptides effectively induced HLA-A24-restricted and prostate cancer-reactive CTLs from prostate cancer patients. The cytotoxicity was mainly dependent on EZH2 peptide-specific and CD8+ T cells. Conclusions: These EZH2-291 to -299 and EZH2-735 to -742 peptides could be promising candidates for peptide-based immunotherapy for HLA-A24+ prostate cancer patients with metastases.