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Background: The identification of epitope peptides from tumor‐associated antigens (TAAs) is informative for developing tumor‐specific immunotherapy. However, only a few epitopes have been detected in mouse TAAs of head and neck cancer (HNSCC). Methods: Novel mouse c‐Met‐derived T‐cell epitopes were predicted by computer‐based algorithms. Mouse HNSCC cell line‐bearing mice were treated with a c‐Met peptide vaccine. The effects of CD8 and/or CD4 T‐cell depletion, and vaccine combination with immune checkpoint inhibitors (ICIs) were evaluated. Tumor re‐inoculation was performed to assess T‐cell memory. Results: We identified c‐Met‐derived short and long epitopes that elicited c‐Met‐reactive antitumor CD8 and/or CD4 T‐cell responses. Vaccination using these peptides showed remarkable antitumor responses via T cells in which ICIs were not required. The c‐Met peptide‐vaccinated mice rejected the re‐inoculated tumors. Conclusions: We demonstrated that novel c‐Met peptide vaccines can induce antitumor T‐cell response, and could be a potent immunotherapy in a syngeneic mouse HNSCC model. [ABSTRACT FROM AUTHOR]

Homeobox B7 (HOXB7) is a master regulatory gene that regulates cell proliferation and activates oncogenic pathways. Overexpression of HOXB7 correlates with aggressive behavior and poor prognosis in patients with cancer. However, the expression and role of HOXB7 in head and neck squamous cell carcinoma (HNSCC) remain unclear. In this study, we observed that most samples from patients with oropharyngeal cancer and HNSCC expressed HOXB7. As no direct inhibitor has been reported, we identified a potent peptide epitope to target HOXB7‐expressing tumors through immune cells. A novel HOXB7‐derived peptide epitope (HOXB78–25) elicited antigen‐specific and tumor‐reactive promiscuous CD4+ T cell responses. These CD4+ T cells produced γ‐interferon (IFN‐γ) and had the direct ability to kill tumors through granzyme B. Notably, downregulation of HOXB7 using siRNA enhanced human leukocyte antigen class II expression on tumor cells by decreasing the phosphorylation of MAPK. Mitogen‐activated protein kinase inhibition augmented IFN‐γ production by HOXB7‐reactive CD4+ T cell responses without decreasing the expression of HOXB7. These results suggest that combining HOXB7 peptide‐based vaccine with MAPK inhibitors could be an effective immunological strategy for cancer treatment. [ABSTRACT FROM AUTHOR]

Tumor immune escape has been a major problem for developing effective immunotherapy. The human leukocyte antigen G (HLA-G) is a non-classical MHC class I molecule whose primary function is to protect the fetus from the mother's immune system. While HLA-G is hardly found in normal adult tissues, various tumor cells are known to express it, aiding their escape from the immune system. Thus, HLA-G is an attractive immunotherapy target. CD4+helper T lymphocytes (HTLs) play an important role in the immune reaction against tumors by assisting in the generation and persistence of CD8+cytotoxic T lymphocytes (CTLs) or by displaying direct antitumor effects. We report here that HLA-G expression in breast cancer significantly correlates with a poor prognosis. Also, we describe that the MHC class II-binding peptide HLA-G26–40was effective in eliciting tumor-reactive CD4+T cell responses. Furthermore, treatment with the DNA methyltransferase inhibitor 5-aza-2′-deoxycytidine increased HLA-G expression in tumors and subsequently enhanced recognition by HLA-G26–40-specific HTLs. These findings predict that a combination immunotherapy targeting HLA-G together with a DNA methyltransferase inhibitor could be useful against some cancers. [ABSTRACT FROM AUTHOR]