Identification of Neoantigens in Two Murine Gastric Cancer Cell Lines Leading to the Neoantigen-Based Immunotherapy.

To develop combination immunotherapies for gastric cancers, immunologically well-characterized preclinical models are crucial. Here, we leveraged two transplantable murine gastric cancer cell lines, YTN2 and YTN16, derived from the same parental line but differing in their susceptibility to immune rejection. We established their differential sensitivity to immune checkpoint inhibitors (ICI) and identified neoantigens. Although anti-CTLA-4 mAbs eradicated YTN16 tumors in 4 of 5 mice, anti-PD-1 and anti-PD-L1 mAbs failed to eradicate YTN16 tumors. Using whole-exome and RNA sequencing, we identified two and three neoantigens in YTN2 and YTN16, respectively. MHC class I ligandome analysis detected the expression of only one of these neoantigens, mutated Cdt1, but the exact length of MHC binding peptide was determined. Dendritic cell vaccine loaded with neoepitope peptides and adoptive transfer of neoantigen-specific CD8+ T cells successfully inhibited the YTN16 tumor growth. Targeting mutated Cdt1 had better efficacy for controlling the tumor. Therefore, mutated Cdt1 was the dominant neoantigen in these tumor cells. More mCdt1 peptides were bound to MHC class I and presented on YTN2 surface than YTN16. This might be one of the reasons why YTN2 was rejected while YTN16 grew in immune-competent mice.

Development of a novel monoclonal antibody that binds to most HLA-A allomorphs in a conformation-dependent yet peptide-promiscuous fashion.

Specificity analyses of peptide binding to human leukocyte antigen (HLA)-A molecules have been hampered due to a lack of proper monoclonal antibodies (mAbs) for certain allomorphs, such as the prevalent HLA-A1 for Caucasians and HLA-A11 for Asians. We developed a mAb that recognizes a conformational epitope common to most HLA-A allomorphs. The mAb, named A-1, does not discriminate peptides by amino acid sequences, making it suitable for measuring peptide binding. A stabilization assay using TAP-deficient cell lines and A-1 was developed to investigate the specificity of peptide binding to HLA-A molecules. Regarding the evolution of HLA-A genes, the A-1 epitope has been conserved among most HLA-A allomorphs but was lost when the HLA-A gene diversified into the HLA-A*32, HLA-A*31, and HLA-A*33 lineages together with HLA-A*29 after bifurcating from the HLA-A*25 and HLA-A*26 branchs. The establishment of A-1 is expected to help researchers investigate the peptide repertoire and develop computational tools to identify cognate peptides. Since no HLA-A locus-specific mAb has been available, A-1 will also be useful for analyzing the locus-specific regulation of the HLA gene expression.

Knockout of the interleukin-36 receptor protects against renal ischemia-reperfusion injury by reduction of proinflammatory cytokines.

IL-36, a newly named member of the IL-1 cytokine family, includes 3 isoforms, IL-36α, IL-36ß, and IL-36γ, all of which bind to a heterodimer containing the IL-36 receptor (IL-36R). Little is known about the role of the IL-36 axis in acute kidney injury (AKI) pathogenesis. Therefore, we evaluated IL-36 function in the bilateral renal ischemia-reperfusion injury model of AKI using IL-36R knockout and wild-type mice. IL-36R was found to be expressed in the kidney, mainly in proximal tubules. In IL-36R knockout mice, plasma creatinine, blood urea nitrogen, and IL-6 levels after ischemia-reperfusion injury were significantly lower than those in wild-type mice. Immunohistological analysis revealed mild tubular injury. IL-36α/ß/γ levels were increased after ischemia-reperfusion injury, and IL-36α was expressed in lymphocytes and proximal tubular cells, but post-ischemia-reperfusion injury mRNA levels of IL-6 and TNF-α were low in IL-36R knockout mice. In primary cultures of renal tubular epithelial cells, IL-36α treatment upregulated NF-κB activity and Erk phosphorylation. Notably, in patients with AKI, urine IL-36α levels were increased, and IL-36α staining in renal biopsy samples was enhanced. Thus, IL-36α/IL-36R blockage could serve as a potential therapeutic target in AKI.

Improvement of Peptide-Based Tumor Immunotherapy Using pH-Sensitive Fusogenic Polymer-Modified Liposomes.

To establish peptide vaccine-based cancer immunotherapy, we investigated the improvement of antigenic peptides by encapsulation with pH-sensitive fusogenic polymer-modified liposomes for induction of antigen-specific immunity. The liposomes were prepared by modification of egg yolk phosphatidylcholine and l-dioleoyl phosphatidylethanolamine with 3-methyl-glutarylated hyperbranched poly(glycidol) (MGlu-HPG) and were loaded with antigenic peptides derived from ovalbumin (OVA) OVA-I (SIINFEKL), and OVA-II (PSISQAVHAAHAEINEAPßA), which bind, respectively, to major histocompatibility complex (MHC) class I and class II molecules on dendritic cell (DCs). The peptide-loaded liposomes were taken up efficiently by DCs. The peptides were delivered into their cytosol. Administration of OVA-I-loaded MGlu-HPG-modified liposomes to mice bearing OVA-expressing E.G7-OVA tumors induced the activation of OVA-specific CTLs much more efficiently than the administration of free OVA-I peptide did. Mice strongly rejected E.G7-OVA cells after immunization with OVA-I peptide-loaded MGlu-HPG liposomes, although mice treated with free OVA-I peptide only slightly rejected the cells. Furthermore, efficient suppression of tumor volume was observed when tumor-bearing mice were immunized with OVA-I-peptide-loaded liposomes. Immunization with OVA-II-loaded MGlu-HPG-modified liposomes exhibited much lower tumor-suppressive effects. Results indicate that MGlu-HPG liposomes might be useful for improvement of CTL-inducing peptides for efficient cancer immunotherapy.

Novel combination therapy with imiquimod and sorafenib for renal cell carcinoma.

OBJECTIVES: To investigate whether the combination of the imidazoquinoline immune response modifier, imiquimod, and the multitargeted tyrosine-kinase inhibitor, sorafenib, inhibits the growth of renal cell carcinoma in mice. METHODS: Female BALB/c mice were implanted subcutaneously with 2 × 10(5) RENCA mouse kidney cancer cells, and were treated with transcutaneously applied cream containing imiquimod and oral administrations of sorafenib beginning 5 days after implantation of the cells. Tumor incidence and burden were determined at 28 days after initiation of therapy. T cell infiltration in the tumor was determined by immunofluorescence staining with anti-CD3-ε and CD8-α antibodies. RESULTS: Therapy with imiquimod, sorafenib or their combination was well tolerated. Combination therapy with imiquimod and sorafenib significantly inhibited tumor growth when compared with administration of control vehicle, imiquimod or sorafenib alone (P < 0.05). The CD3- and CD8-positive T cells infiltrated into tumors to a greater degree in response to the combination therapy when compared with tumors treated with control vehicle or sorafenib alone. CONCLUSIONS: Combination therapy with a tyrosine-kinase inhibitor and an imidazoquinoline could be a promising therapeutic strategy for patients with renal cell carcinoma.

Potent CTL induction by a whole cell pertussis vaccine in anti-tumor peptide immunotherapy.

Promising yet limited clinical responses have been reported for peptide based immunotherapy against tumors. In order to induce more potent cytolytic CD8 T cell responses, we investigated the use of Bordetella pertussis vaccine as an adjuvant for peptide immunization. A whole cell (Wc) vaccine has been known to induce a Th1 biased immune response while an acellular (Ac) vaccine tends to induce that of the Th2 type. Natural infection by B. pertussis helps to maintain a robust Th1 memory in the host population. To examine the adjuvant activity of the pertussis vaccine, we immunized mice with an ovalbumin peptide as a model tumor antigen, and monitored the development of anti-tumor activities. The addition of either the Ac or the Wc vaccine helped expand the specific CD8 T cells. However, there was a marked difference in the induced cytolytic activity where the Wc vaccine was superior to the Ac. The Wc vaccine was also more effective in inducing in vivo tumor rejection. The adjuvant activity was not only effective against ovalbumin, but was also evident when an endogenous tumor antigen, Wilms' tumor 1 gene product, was targeted. These results indicate that, although the Wc vaccine does not share the same antigen specificity with tumor cells, it can aid in the development of highly cytolytic CD8 T cells as an adjuvant at the site of peptide immunization.