Cancer immunotherapy has attracted attention worldwide owing to the recent development of immune checkpoint inhibitors. However, these therapies have shown limited efficacy, and further advancements are needed before these modalities can progress to widespread use. Immune checkpoint inhibitors are a type of nonspecific cancer immunotherapy, and antitumor effects are only observed when cancer-specific T cells are found within the nonspecifically activated T-cell group. In order to facilitate the development of potent immunotherapies, selective enhancement of cancer-specific T cells is essential. In this report, we discuss current and future perspectives, including the latest clinical trials of cancer-specific immunotherapies, particularly cancer peptide vaccines.
The fields of cancer immunology and immunotherapy have made dramatic progress in the past 20 years. Various approaches to cancer immunotherapies, including cancer vaccines using peptides, proteins, DNA, and dendritic cells, have been developed to activate antigen-specific immune cells and their efficacy has been clinically examined. Herein, we summarize previously performed clinical trials of various immunotherapies against colorectal cancer (CRC), including our own novel immunotherapeutic approach, the "personalized peptide vaccine", in which human leukocyte antigen (HLA)-matched vaccine peptides are selected based on pre-existing host immunity before vaccination. In the near future, neoepitopes identified through massive DNA sequencing of the genetic alterations in tumor cells, combined with robust T cell epitope predictions in each patient might be targeted as a personalized immunotherapy for CRC. ARTICLE HISTORY
To clarify the mechanisms of the anti-mammary tumor activity of coffee cherry (CC), the residue left after the removal of beans from the fruit, the effects in SHN mice of CC on plasma and urine component levels, mammary gland growth, spontaneous motor activity and several related parameters were examined. Hot water extract of CC was given to 2-month-old mice in drinking water (0.5%) for 60 days. The treatment prevented the elevation of plasma and urine levels of alanin amino-transferase and asparate aminotransferase, indicating that CC can protect against metabolic abnormality, which is a cause of the high mammary tumor susceptibility of SHN mice. It also resulted in an inhibition of the formation of precancerous mammary hyperplastic alveolar nodules. Neither food and water intake nor spontaneous motor activity was affected by CC. The findings provide novel information on the mechanism of the protective effect of CC on mammary tumorigenesis and confirm the usefulness of CC as a safe chemopreventive agent of mammary and other types of tumors.
Colorectal cancer (CRC) is one of the most increasing cancers worldwide, and novel treatment modalities remain to be developed for advanced CRC patients. In recent years, immune checkpoint inhibitors have demonstrated impressive clinical efficacy in various types of cancers, but limited clinical responses were reported in CRC, except for MSI-high or MMR-deficient tumors. It has thus been suggested that immune suppressive mechanisms other than immune checkpoints might contribute to tumor progression in CRC. In the current study, various types of immune cells were isolated from peripheral blood or resected tumor/normal tissues and regional lymph nodes in 25 primary CRC patients, and their phenotypes and functions were comprehensively assessed. Flow cytometry analysis demonstrated a significant increase of CD4+FoxP3+ T cells, which might represent regulatory T cells, in proximal lymph nodes (N1 region), compared to distal (N2 or N3 region) or unrelated lymph nodes. In addition, the functional analysis of T cells assessed by cytokine production after non-specific stimulation (PMA and A23187) showed a significant decrease in the frequencies of IFN γ-producing CD8+ T cells in N1 region. Notably, reduction of IFN γ-producing CD8+ T cells seemed to be associated with advanced stages of disease. These results indicate that the immunosuppressive microenvironment, particularly in regional lymph nodes, may be related to tumor progression in CRC. The current study suggests that monitoring of immunosuppressive microenvironment would be useful as a predictive biomarker for cancer progression and patient prognosis in CRC. Further studies remain to be performed to more thoroughly elucidate immune suppressive mechanisms, and thereby to develop a novel immunotherapeutic strategy in CRC. Citation Format: Tetsuro Sasada, Junya Ohtake, Tetsuta Satoyoshi, Keisuke Kazama, Satoshi Wada, Erika Yada, Manabu Shiozawa. Elucidation of immunosuppressive microenvironment in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4739.
Neoantigens derived from tumor-specific genetic mutations can be recognized as foreign by the host immune system, and might be suitable as target for cancer immunotherapy possibly due to their higher immunogenicity. In this study, to really know the immunogenicity of tumor-specific neoantigens, we comprehensively investigated T cell responses against neoantigens derived from genetic mutations in gastric cancer. Using next-generation sequencing, 156 missense mutations were identified in tumor cells from two gastric cancer patients. From them, we selected 30 potentially immunogenic amino acid sequences, which were derived from the mutations and predicted to potentially bind to HLA-class I (A*0201, A*0206, or A*2402) by an epitope prediction server, IEBD. We synthesized 30 kinds of 27mer long peptides, in which the mutated sequences were located in the center, and then cultured peripheral blood mononuclear cells (PBMC) from healthy donors in the presence of the synthetic peptides to evaluate whether they could really induce antigen-specific T cell responses. In the analysis with PBMC from 18 healthy donors, 27/30 (90%) synthetic peptides showed an ability to induce antigen-specific T cell responses in at least one donor, assessed by cytokine production assay. Among them, 15 peptides were immunogenic in more than one donor. The antigen-specific T cell responses were detected more frequently in CD4+ T cells (70%) than in CD8+ T cells (43%). The specificity of T cell responses to mutated sequences, but not to the corresponding wild type sequences, were confirmed in 5 of 8 (63%) peptides examined. In addition, antigen-specific T cell responses induced by mutated peptides were shown to be much higher than those induced by the corresponding wild type peptides. These findings clearly demonstrated high immunogenicity and specificity of neoantigens derived from tumor-specific genetic mutations. Further studies would be recommended to develop a novel immunotherapeutic approach, “personalized cancer vaccination”, targeting mutation-derived neoantigens. Citation Format: Tetsuro Sasada, Junya Ohtake, Satoshi Wada, Erika Yada, Shintaro Yoshida. Comprehensive analysis of T cells responsive to neoantigens derived from tumor-specific genetic mutations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 636. doi:10.1158/1538-7445.AM2017-636
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