Yuriko Sato

A Potent Immunogenic General Cancer Vaccine That Targets Survivin, an Inhibitor of Apoptosis Proteins

We reported previously a HLA-A24-restricted antigenic peptide, survivin-2B80-88 (AYACNTSTL), recognized by CD8+ CTL. This peptide was derived from survivin protein, an inhibitor of apoptosis proteins, expressed in a variety of tumors, such as adenocarcinoma, squamous cell carcinoma, and malignant melanoma. In this report, we provide further evidence that survivin-2B80-88 peptide might serve as a potent immunogenic cancer vaccine for various cancer patients. Overexpression of survivin was detected in surgically resected primary tumor specimens of most breast and colorectal cancers and some gastric cancers as assessed by immunohistochemical study. HLA-A24/survivin-2B80-88 tetramer analysis revealed that there existed an increased number of CTL precursors in peripheral blood mononuclear cells (PBMC) of HLA-A24+ cancer patients, and in vitro stimulation of PBMCs from six breast cancer patients with survivin-2B80-88 peptide could lead to increases of the CTL precursor frequency. Furthermore, CTLs specific for this peptide were successfully induced from PBMCs in all 7 (100%) patients with breast cancers, 6 of 7 (83%) patients with colorectal cancers, and 4 of 7 (57%) patients with gastric cancers. These data indicate that survivin expressed in tumor tissues is antigenic in cancer patients, and survivin-2B80-88-specific CTLs are present in PBMCs of various cancer patients. Our study raises the possibility that this peptide may be applicable as a general cancer vaccine to a large proportion of HLA-A24+ cancer patients.

Phase I vaccination trial of SYT-SSX junction peptide in patients with disseminated synovial sarcoma

BackgroundSynovial sarcoma is a high-grade malignant tumor of soft tissue, characterized by the specific chromosomal translocation t(X;18), and its resultant SYT-SSX fusion gene. Despite intensive multimodality therapy, the majority of metastatic or relapsed diseases still remain incurable, thus suggesting a need for new therapeutic options. We previously demonstrated the antigenicity of SYT-SSX gene-derived peptides by in vitro analyses. The present study was designed to evaluate in vivo immunological property of a SYT-SSX junction peptide in selected patients with synovial sarcoma.MethodsA 9-mer peptide (SYT-SSX B: GYDQIMPKK) spanning the SYT-SSX fusion region was synthesized. Eligible patients were those (i) who have histologically and genetically confirmed, unresectable synovial sarcoma (SYT-SSX1 or SYT-SSX2 positive), (ii) HLA-A*2402 positive, (iii) between 20 and 70 years old, (iv) ECOG performance status between 0 and 3, and (v) who gave informed consent. Vaccinations with SYT-SSX B peptide (0.1 mg or 1.0 mg) were given subcutaneously six times at 14-day intervals. These patients were evaluated for DTH skin test, adverse events, tumor size, tetramer staining, and peptide-specific CTL induction.ResultsA total of 16 vaccinations were carried out in six patients. The results were (i) no serious adverse effects or DTH reactions, (ii) suppression of tumor progression in one patient, (iii) increases in the frequency of peptide-specific CTLs in three patients and a decrease in one patient, and (iv) successful induction of peptide-specific CTLs from four patients.ConclusionsOur findings indicate the safety of the SYT-SSX junction peptide in the use of vaccination and also give support to the property of the peptide to evoke in vivo immunological responses. Modification of both the peptide itself and the related protocol is required to further improve the therapeutic efficacy.

Detection and Induction of CTLs Specific for SYT-SSX-Derived Peptides in HLA-A24+ Patients with Synovial Sarcoma

To investigate the immunogenic property of peptides derived from the synovial sarcoma-specific SYT-SSX fusion gene, we synthesized four peptides according to the binding motif for HLA-A24. The peptides, SS391 (PYGYDQIMPK) and SS393 (GYDQIMPKK), were derived from the breakpoint of SYT-SSX, and SS449a (AWTHRLRER) and SS449b (AWTHRLRERK) were from the SSX region. These peptides were tested for their reactivity with CTL precursors (CTLps) in 16 synovial sarcoma patients using HLA-A24/SYT-SSX peptide tetramers and also for induction of specific CTLs from four HLA-A24+ synovial sarcoma patients. Tetramer analysis indicated that the increased CTLp frequency to the SYT-SSX was associated with pulmonary metastasis in synovial sarcoma patients (p < 0.03). CTLs were induced from PBLs of two synovial sarcoma patients using the peptide mixture of SS391 and SS393, which lysed HLA-A24+ synovial sarcoma cells expressing SYT-SSX as well as the peptide-pulsed target cells in an HLA class I-restricted manner. These findings suggest that aberrantly expressed SYT-SSX gene products have primed SYT-SSX-specific CTLps in vivo and increased their frequency in synovial sarcoma patients. The identification of SYT-SSX peptides may offer an opportunity to design peptide-based immunotherapeutic approaches for HLA-A24+ patients with synovial sarcoma.

Identification of Human Autologous Cytotoxic T-Lymphocyte-Defined Osteosarcoma Gene That Encodes a Transcriptional Regulator, Papillomavirus Binding Factor

The prognosis for patients with osteosarcoma who do not respond to current chemotherapy protocols still remains poor. Toward the goal of establishing efficacious peptide-based immunotherapy for those patients, we previously developed an autologous pair of CTLs and an osteosarcoma cell line. In the current study, we screened the cDNA library of this osteosarcoma cell line using an autologous CTL clone and identified cDNA encoding an antigen. The isolated cDNA was identical to papillomavirus binding factor (PBF), which was recently reported as a DNA binding transcription factor cooperating with RUNX1. Reverse transcription-PCR analysis revealed that PBF was expressed in 16 of 19 cases of bone and soft-tissue sarcoma cell lines (5 of 6 of osteosarcoma lines) and 57 of 76 sarcoma tissue samples (11 of 14 of osteosarcoma tissues). Also, PBF was expressed in 10 of 13 epithelial cancer cell lines and 20 of 34 of cancer tissues. In contrast, PBF was detected in some normal organs including ovary, pancreas, spleen, and liver by reverse transcription-PCR but was restricted in the cytoplasm by immunostaining and undetectable by Western blotting. Furthermore, a 12-mer peptide, CTACRWKKACQR, located at the COOH terminus of PBF, was found to be a minimum requirement for recognition by the CTL clone in the context of the HLA-B*5502 molecule. These findings suggest that PBF is a shared tumor-associated antigen, which may serve as a source of peptides applicable to peptide-based immunotherapy for osteosarcoma and other malignant tumors.

Crisscross CTL Induction by SYT-SSX Junction Peptide and Its HLA-A*2402 Anchor Substitute

To investigate the effects of anchor substitutions in SYT-SSX junction peptide, an HLA-A24 anchor residue (position 9) of the SYT-SSX B peptide (GYDQIMPKK) was substituted to more favorable residues according to the HLA-A24-binding motif. Among four substitutes constructed, a substitute with isoleucine (termed K9I peptide) most apparently enhanced the affinity for HLA-A24 molecule. Subsequent in vitro CTL induction analysis using PBMCs of 15 HLA-A24+ synovial sarcoma patients revealed that the original B peptide allowed to induce synovial sarcoma-specific CTLs from 7 patients (47%), whereas such CTLs were inducible from 12 patients (80%) with K9I peptide. Moreover, the extent of cytotoxicity against HLA-A24+ synovial sarcoma cell lines was higher in K9I peptide-induced CTLs than B peptide-induced CTLs. Influence of anchor substitution on peptide/TCR interaction was evaluated by cytotoxicity assays against autologous cells and tetramer analysis. CTLs induced from a synovial sarcoma patient using K9I peptide did not lyse autologous PHA blasts or EBV-infected B cells. In vitro stimulations of PBMCs from 5 HLA-A24+ synovial sarcoma patients with K9I peptide increased the frequency of T cells reacting with both HLA-A24/K9I peptide tetramer and HLA-A24/B peptide tetramer. In contrast, the frequency of T cells reacting with HLA/HIV-derived peptide tetramer remained low. These findings support the validity in design of anchor residue substitution in SYT-SSX fusion gene-derived peptide, and provide a potential clue to the current stagnation in vaccination trials of fusion gene-derived natural junction peptides.

Human CD8 and CD4 T cell epitopes of epithelial cancer antigens

Abstract Recent human tumor immunology research has identified several genes coding immunogenic peptides recognized by CD8 cytotoxic T lymphocytes (CTLs) in melanoma tumors. Very recently, CD4 T cell antigenic epitopes were also determined in certain melanoma tumors. The use of these peptides in conjunction with human immunotherapy could prove to be of great benefit. However, such peptides in clinically common tumors of epithelial cell origin, such as of the stomach, colon, lung, etc., have not yet been determined extensively. We describe for the first time an HLA-A31 (A*31012)-restricted natural antigenic peptide recognized by the CD8 CTL TcHST-2 of gastric signet ring cell carcinoma cell line HST-2. We also identified the HLA-DRB1*08032-restricted peptide recognized by the CD4 T cell line TcOSC-20 of squamous cell carcinoma OSC-20 derived from the oral cavity. The antigenic peptide of HST-2, designated F4.2, is composed of 10 amino acid residues with two anchor motif residues necessary for binding to HLA-A31 molecules. The synthetic F4.2 peptide enhanced the reactivity of TcHST-2 against HST-2 cells. Furthermore, introduction of an expression minigene coding F4.2 peptide to HLA-A31(+) cells conferred cytotoxic susceptibility to TcHST-2 on the cells. Some stomach cancer lines into which the HLA-A31 gene had been introduced, such as MKN28-A31-2, were lysed by TcHST-2, suggesting the presence of F4.2 peptide in at least some HLA-A31(+) stomach cancers. Furthermore, F4.2 peptide induced an F4.2 peptide-specific CTL response in at least 30–40% of HLA-A31(+) peripheral blood lymphocytes from gastric cancer patients, suggesting that F4.2 peptide could be used as a cancer vaccine for gastric tumors. The natural antigenic peptide of OSC-20 was also determined using acid extraction and biochemical separation and by mass spectrometry. Consequently, OSC-20 peptide was designated as the 6-1-5 peptide, an HLA-DRB1*08032-restricted 16-mer peptide with two possible anchor motifs. It has an amino acid sequence identical to that of human α-enolase, suggesting that it was derived from the processed parental α-enolase protein. We are presently attempting to determine the genes that code tumor rejection antigens recognized by HLA-A24- and A26-restricted T cells, including those of pulmonary and pancreatic carcinomas. The search for these antigenic peptides may lead to the identification of immunogenic peptide antigens that would be suitable for clinical use in commonly occurring epithelial cancers.

Induction of cytotoxic T lymphocytes from peripheral blood of human histocompatibility antigen (HLA)-A31+ gastric cancer patients by in vitro stimulation with antigenic peptide of signet ring cell carcinoma

Antigenic peptides have been used as a cancer vaccine in melanoma patients and have led to a drastic regression of metastatic tumors. However, few antigens have been identified in non‐melanoma tumors. We recently purified a new natural antigenic peptide, designated F4.2, by biochemical elution from a human gastric signet cell carcinoma cell line and showed that it is recognized by an autologous human histocompatibility antigen (HLA)‐A31‐restricted cytotoxic T lymphocyte (CTL) clone. Here we describe in vitro induction of F4.2‐specific CTLs from peripheral blood T lymphocytes of HLA‐A31+ gastric cancer patients. The T cells of seven HLA‐A31+ patients with gastric cancers were stimulated in vitro by F4.2‐pulsed autologous dendritic cells which had been induced from peripheral blood of each patient by incubation in the presence of granulocyte macrophage colony‐stimulating factor (GM‐CSF) and IL‐4. We tested the cytotoxicity of the T cells against F4.2‐loaded C1R‐A *31012 by a 6‐h 51Cr release assay after 3 stimulations with F4.2‐pulsed dendritic cells. F4.2‐specific cytotoxicity was detectable in the stimulated T cells from two of the seven HLA‐A31+ patients. Further, both F4.2‐specific CTLs also lysed the gastric cancer cell line, HST‐2, from which F4.2 was derived. These results suggest that F4.2 peptide may be useful as an HLA‐A31‐restricted peptide vaccine in certain patients with gastric cancer.

Frequent detection of anti-recoverin cytotoxic T-lymphocyte precursors in peripheral blood of cancer patients by using an HLA-A24-recoverin tetramer

Recoverin is a photoreceptor-specific calcium binding protein that is only expressed in the retina in normal tissues. Aberrant expression of recoverin, however, has been observed in several cancer tissues and may cause a very rare autoimmune disease, cancer-associated retinopathy (CAR). It has been suggested that CAR-positive cancer patients have a more favorable prognosis than CAR-negative cancer patients. To estimate the status of recoverin-specific T cells in such cancer patients, we generated an HLA-Aff24-recoverin peptide tetramer. By use of the tetramer, we could directly assess the frequency of CTL precursors (CTLp) of 20 HLA-Aff24+ cancer patients with ten colon, six stomach and four breast cancers, and seven healthy individuals. Four cancer patients showed a CTLp frequency higher than 0.9%. Seven cancer patients including the former four patients and two healthy individuals showed specific anti-recoverin cytotoxic responses in an HLA-Aff24-restricted manner after in vitro stimulation with the recoverin peptide. Moreover, five cancer patients analyzed in an independent experiment using different peripheral blood mononuclear cells (PBMC) samples showed similar CTLp and cytotoxic T lymphocyte (CTL) frequencies and cytotoxic responses, suggesting that the CTLp frequency analyzed by the tetramer and the cytotoxic response may have a good correlation. Thus, we hypothesize that anti-recoverin CTLp may exist in some cancer patients, and that anti-recoverin CTL may be readily induced.