Yuki Ishihara

Immunological evaluation of personalized peptide vaccination in combination with a 5-fluorouracil derivative (TS-1) for advanced gastric or colorectal carcinoma patients

The aim of the present study was to investigate the safety and immunological responses of personalized peptide vaccination in combination with oral administration of a 5‐fluorouracil derivative (TS‐1) in advanced gastric or colorectal carcinoma patients. Eleven patients (four with gastric cancer and seven with colorectal cancer) who failed to improve by prior TS‐1‐based chemotherapies were enrolled in this study. Peptides to be administered to patients were determined based on the presence of peptide‐specific cytotoxic T lymphocyte (CTL) precursors in peripheral blood mononuclear cells and peptide‐specific IgG in the plasma of cancer patients. Patients were vaccinated with peptides (a maximum of four) biweekly in combination with or without three different doses of TS‐1 (20, 40 and 80 mg/m2/day). Although grade 3 toxicity, including anemia (one patient) and neutropenia (one patient) were observed, the combination therapy was generally well tolerated. An increase in peptide‐specific IgG after the sixth vaccination was observed in the vast majority of patients irrespective of the dose of TS‐1 used. In contrast, an increase in peptide‐specific interferon‐γ production by CTL was most evident in patients who were administered the highest dose of TS‐1. Furthermore, in the patients who received 80 mg/m2/day TS‐1, CTL‐mediated cytotoxicity against cancer cells was maintained at the prevaccination level. These results indicate that administration of the standard dose (80 mg/m2/day) of TS‐1 in combination with a personalized peptide vaccination does not necessarily impede immunological responses in cancer patients, and could actually maintain or augment them. (Cancer Sci 2007; 98: 1113–1119)

A phase II study of a personalized peptide vaccination for chemotherapy-resistant advanced pancreatic cancer patients

Pancreatic cancer is one of the most aggressive cancers with a median survival time (MST) of <6 months in chemotherapy-resistant patients. Therefore, the development of novel treatment modalities is needed. In the present study, a phase II study of personalized peptide vaccination (PPV) was conducted, in which vaccine antigens were selected and administered based on the pre-existing IgG responses to 31 different pooled peptides, for 41 chemotherapy-resistant advanced pancreatic cancer patients. No vaccine-related severe adverse events were observed. IgG responses specific to at least one of the vaccine peptides were augmented in 14 of 36 patients (39%) and in 18 of 19 patients (95%) tested after the 5th and 11th vaccination, respectively. MST from the first vaccination was 7.9 months with a 1-year survival rate of 26.8%. Higher serum amyloid A (SAA) and C-reactive protein (CRP) levels in pre-vaccination plasma were unfavorable factors for overall survival (OS). Due to the safety profile and the potential clinical efficacy, the conduction of additional clinical trials of PPV for chemotherapy-resistant advanced pancreatic cancer patients is warranted.

Identification of parathyroid hormone-related protein-derived peptides immunogenic in human histocompatibility leukocyte antigen-A24+ prostate cancer patients.

Parathyroid hormone-related protein (PTHrP) is a key factor in the development of bone metastases, which are a major barrier in treating prostate cancer patients. In this study, we attempted to identify PTHrP-derived peptides immunogenic in human histocompatibility leukocyte antigen (HLA)-A24+ prostate cancer patients. Among four different PTHrP peptides carrying the HLA-A24 binding motif, both the PTHrP36–44 and PTHrP102–111 peptides efficiently induced peptide-specific cytotoxic T lymphocytes from peripheral blood mononuclear cells (PBMCs) of HLA-A24+ prostate cancer patients. Peptide-stimulated PBMCs showed cytotoxicity against prostate cancer cells in an HLA-A24-restricted manner. Experiments using antibodies and cold inhibition targets confirmed that their cytotoxicity was dependent on PTHrP peptide-specific and CD8+ T cells. Immunoglobulin G reactive to the PTHrP102–111 or PTHrP110–119 peptide was frequently detected in the plasma of prostate cancer patients, suggesting that the PTHrP102–111 peptide is able to elicit cellular and humoral immune responses in cancer patients. These results indicate that the PTHrP could be a promising target molecule for specific immunotherapy of HLA-A24+ prostate cancer patients with metastases.

Two proliferation-related proteins, TYMS and PGK1, could be new cytotoxic T lymphocyte-directed tumor-associated antigens of HLA-A2+ colon cancer.

Purpose: The purpose of this work was to provide a scientific basis for specific immunotherapy of colon cancer. Experimental Design: This study focused on identification of colon tumor-associated antigens and HLA-A2–restricted and tumor-reactive cytotoxic T lymphocytes (CTLs) generated from tumor-infiltrating lymphocytes of a colon cancer patient. A gene expression cloning method was used to identify genes coding for tumor antigens. Fifty-six peptides with HLA-A2–binding motifs encoded by these proteins were examined for their ability to induce HLA-A2–restricted and tumor-reactive CTLs. Results: We identified the following three genes coding for proliferation-related proteins: thymidylate synthase (TYMS), which is involved in chemoresistance (5-fluorouracil); 5′-aminoimidazole-4-carboxamide-1-β-d-ribonucleotide transfolmylase/inosinicase (AICRT/I); and phosphoglycerate kinase 1 (PKG1), which was secreted by tumor cells and involved in the angiogenic process. TYMS was preferentially expressed in tumor cells, whereas AICRT/I and PKG1 were equally expressed in both cancer cells and normal tissues at the mRNA level. Among 56 peptides with HLA-A2–binding motifs encoded by these proteins, 8 peptides were recognized by the CTLs, and 5 of 8 peptides were also recognized by the CTL precursors without ex vivo activation in the peripheral blood of colon cancer patients. Furthermore, four of them (one each from TYMS and PKG1 and two from AICRT/1) possessed the ability to induce HLA-A2–restricted and peptide-specific CTLs cytotoxic to colon tumor cells in peripheral blood mononuclear cells of colon cancer patients. Conclusions: TYMS and PGK1, as well as their epitope peptides, might be appropriate target molecules for specific immunotherapy of HLA-A2+ colon cancer patients because of the positive role of TYMS and PGK1 in chemoresistance (5-fluorouracil) and angiogenesis of tumor cells, respectively.

Identification of Lck-derived peptides applicable to anti-cancer vaccine for patients with human leukocyte antigen-A3 supertype alleles.

The identification of peptide vaccine candidates to date has been focused on human leukocyte antigen (HLA)-A2 and -A24 alleles. In this study, we attempted to identify cytotoxic T lymphocyte (CTL)-directed Lck-derived peptides applicable to HLA-A11+, -A31+, or -A33+ cancer patients, because these HLA-A alleles share binding motifs, designated HLA-A3 supertype alleles, and because the Lck is preferentially expressed in metastatic cancer. Twenty-one Lck-derived peptides were prepared based on the binding motif to the HLA-A3 supertype alleles. They were first screened for their recognisability by immunoglobulin G (IgG) in the plasma of prostate cancer patients, and the selected candidates were subsequently tested for their potential to induce peptide-specific CTLs from peripheral blood mononuclear cells of HLA-A3 supertype+ cancer patients. As a result, four Lck peptides were frequently recognised by IgGs, and three of them – Lck90−99, Lck449−458, and Lck450−458 – efficiently induced peptide-specific and cancer-reactive CTLs. Their cytotoxicity towards cancer cells was mainly ascribed to HLA class I-restricted and peptide-specific CD8+ T cells. These results indicate that these three Lck peptides are applicable to HLA-A3 supertype+ cancer patients, especially those with metastasis. This information could facilitate the development of peptide-based anti-cancer vaccine for patients with alleles other than HLA-A2 and -A24.

New peptide vaccine candidates for epithelial cancer patients with HLA-A3 supertype alleles.

We previously identified 2 cancer-associated antigens, immediate early response gene X-1 (IEX) and small GTPase (Ran), and their 5 epitopes using human leukocyte antigen (HLA)-A33-restricted and tumor-infiltrating T cells from a colon cancer patient. In this study, we examined whether or not these peptides can induce cytotoxic T lymphocytes (CTLs) in HLA-A11+ or HLA-A31+ epithelial cancer patients because the HLA-A11, HLA-A31, and HLA-A33 alleles share binding motifs as an HLA-A3 supertype family, which is widely distributed in many ethnic populations. Among them, the 2 peptides, IEX 47-56 and IEX 61-69, induced peptide-specific CTLs from peripheral blood mononuclear cells of cancer patients with the HLA-A11 and HLA-A31 alleles more efficiently than the other 3 peptides. Antibody blocking and cold inhibition experiments revealed that the cytotoxicity of peptide-induced CTLs against cancer cells was attributable to peptide-specific and CD8+ T cells. Together with our previous findings, these results indicate that the 2 IEX peptides could be appropriate vaccine candidates for HLA-A11, HLA-A31, and HLA-A33 positive epithelial cancer patients. This information could expand the chance of a peptide-based cancer vaccine for epithelial cancer patients of many ethnic populations.

A peptide derived from hepatitis C virus (HCV) core protein inducing cellular responses in patients with HCV with various HLA class IA alleles.

C35‐44 peptide is a well known HLA‐A2‐restricted CTL epitope originating from hepatitis C virus (HCV) core protein. It was reported that the majority of HCV positive patients had significant levels of serum IgG specific to this peptide. This study addressed whether C35‐44 peptide could induce CTL activity restricted to various HLA class IA alleles or could not. This peptide demonstrated binding activity to HLA‐A*2402, ‐A*2601, ‐A*3101, and ‐A*3303 molecules, but not to HLA‐A*1101 by means of stabilization assay. This peptide also induced CTL activity restricted to each of them, except HLA‐A11+ peripheral blood mononuclear cells from HCV 1b+ patients by means of 51Cr‐release assay. With regard to HLA‐A2 subtypes, this peptide demonstrated binding activity to HLA‐A*0201 and ‐A*0206, but not to ‐A*0207 molecules. Furthermore, this peptide induced CTL activity from both the patients and healthy donors with all the HLA class IA molecules mentioned above by means of interferon‐γ production assay. These results may provide new insights for the development of a novel peptide vaccine against HCV compatible with various HLA class IA types. J. Med. Virol. 81:1232–1240, 2009.