Yoshihiro Komohara

Phase I trial of personalized peptide vaccination for cytokine-refractory metastatic renal cell carcinoma patients

The aim of this clinical trial was to investigate the toxicity and immunological responses of personalized peptide vaccination for cytokine‐refractory metastatic renal cell carcinoma patients. Patients were confirmed to be human leukocyte antigen (HLA)‐A24 or HLA‐A2 positive and had histologically confirmed renal cell carcinoma. Ten patients were enrolled in the present study. The peptides to be administered were determined based on the presence of peptide‐specific cytotoxic T lymphocyte precursors in peripheral blood mononuclear cells (PBMC) and peptide‐specific IgG in the plasma of cancer patients. Patients received subcutaneous injections of four different peptides (3 mg/peptide) every 2 weeks. Vaccinations were well tolerated without any major adverse events. A minimal increase in peptide‐specific interferon‐γ production in postvaccination PBMC was observed, regardless of higher levels of cytotoxic T lymphocyte activity in prevaccination PBMC. In contrast, an increase in peptide‐specific IgG levels of postvaccination (sixth) plasma was observed in the majority of patients. After progression, five patients received interleukin‐2 therapy and continuous vaccination, with survival of 31, 25, 23, 17, and 15 months, but interleukin‐2 did not impede humoral responses boosted by the vaccination. These results encourage further clinical trials of personalized peptide vaccinations. (Cancer Sci 2007; 98: 1965–1968)

High expression of APOBEC3G in patients infected with hepatitis C virus

APOBEC3G (an apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like 3G; also known as CEM15), a member of the APOBEC family, which possesses cytidine deaminase activity that causes C/G to T/A transition mutations in virus genomes such as human immunodeficiency virus 1 and hepatitis B virus, is reported to play an important role in host-defense mechanisms. However, APOBEC3G expression in patients infected with chronic hepatitis C virus (HCV), of which there are currently more than 170 million worldwide, has not yet been well studied. We investigated this issue herein, and demonstrated an increased expression of APOBEC3G in both hepatocytes and lymphocytes of chronic hepatitis patients infected with HCV. Transfection of the NS5A gene, but not any other non-structural protein genes of HCV tested, to the hepatocellular carcinoma cell line enhanced APOBEC3G expression. Incubation of the cells with interferon also resulted in the augmentation. These results may provide new insight into the pathogenesis of chronic HCV infection.

Erythropoietin-producing hepatocyte B6 variant-derived peptides with the ability to induce glioma-reactive cytotoxic T lymphocytes in human leukocyte antigen-A2+ glioma patients.

We recently cloned a variant form of erythropoietin‐producing hepatocyte (Eph)B6, a member of the Eph receptor tyrosine kinase family. In the present study, we examined the expression of the EphB6 variant (EphB6v) in a panel of brain tumor cell lines and glioblastoma tissues and we found that EphB6v was preferentially expressed in malignant brain tumors, such as glioblastomas and anaplastic astrocytomas. The EphB6v has a unique 54 amino acid sequence at the C‐terminal that is not found in normal EphB6. Therefore, we attempted to identify antigenic peptides unique to EphB6v for immunotherapy. The two EphB6v‐derived peptides exhibited the ability to bind to human leukocyte antigen (HLA)‐A0201 molecules, and each of them was able to induce cytotoxic T lymphocytes in vitro in the peripheral blood mononuclear cells of HLA‐A2+ glioma patients. The cytotoxicity was mediated by peptide‐specific CD8+ T cells in an HLA‐A2‐restricted manner. The expression of EphB6v was also observed in different types of cancer (e.g. lung, colon, stomach, liver and pancreatic) cells. Taken together, the two peptides derived from EphB6v might be appropriate targets for peptide‐based specific immunotherapy for HLA‐A2+ patients with various cancers. (Cancer Sci 2008; 99: 1656–1662)

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.