Application of two-dimensional temperature response functions for reconstruction of divertor heat flux profile in commercial fusion reactors

To keep the tritium breeding rate TBR > 1 and to meet the high heat load and neutron shielding requirements for the first wall and divertor in fusion demonstration (DEMO) reactors, the number of port plugs and other openings must be limited. To accomplish this, it is necessary to develop alternatives to the use of infrared (IR) thermography to determine the peak heat flux and the heat flux profile onto divertor targets. A divertor tile equipped with multiple temperature monitoring channels can be used to reproduce the temperature profile. To avoid the high temperatures and high neutron flux environment in a DEMO, the monitoring positions can be set well away from the irradiated surface. However, the spatial resolution of this method is lower than that provided by IR thermography. In the present work, we apply two-dimensional temperature response functions and the corresponding heat conduction model to temperature data obtained from a divertor tile surface in the large helical device to study the effects of the spatial resolution of the monitored temperature profile on the reconstructed heat flux profile. The findings provide information that will be useful in defining a method for embedding thermocouples into the divertor tiles of future DEMO reactors.

Immuno-genomic analysis reveals eosinophilic feature and favorable prognosis of female non-smoking esophageal squamous cell carcinomas

Most of esophageal squamous cell carcinoma (ESCC) develop in smoking males in Japan, but the genomic etiology and immunological characteristics of rare non-smoking female ECSS remain unclear. To elucidate the genomic and immunological features of ESCC in non-smoking females, we analyzed whole-genome or transcriptome sequencing data from 94 ESCCs, including 20 rare non-smoking female cases. In addition, 31,611 immune cells were extracted from four ESCC tissues and subject to single-cell RNA-seq. We compared their immuno-genomic and microbiome profiles between non-smoking female and smoking ESCCs. Non-smoking females showed much better prognosis. Whole-genome sequencing analysis showed no significant differences in driver genes or copy number alterations depending on smoking status. The mutational signatures specifically observed in non-smoking females ESCC could be attributed to aging. Immune profiling from RNA-seq revealed that ESCC in non-smoking females had high tumor microenvironment signatures and a high abundance of eosinophils with a favorable prognosis. Single-cell RNA-sequencing of intratumor immune cells revealed gender differences of eosinophils and their activation in female cases. ESCCs in non-smoking females have age-related mutational signatures and gender-specific tumor immune environment with eosinophils, which is likely to contribute to their favorable prognosis.

Glioblastoma with high O6-methyl-guanine DNA methyltransferase expression are more immunologically active than tumors with low MGMT expression

Background

Glioblastoma (GBM) is a highly lethal brain tumor. The effectiveness of temozolomide (TMZ) treatment in GBM is linked to the methylation status of O6-methyl-guanine DNA methyltransferase (MGMT) promoter. Patients with unmethylated MGMT promoter have limited treatment options available. Consequently, there is a pressing need for alternative therapeutic strategies for such patients.

Methods

Data, including transcriptomic and clinical information, as well as information on MGMT promoter methylation status in primary GBM, were obtained from The Cancer Genome Atlas (TCGA) (n=121) and Chinese Glioma Genome Atlas (CGGA) (n=83) datasets. Samples were categorized into high and low MGMT expression groups, MGMT-high (MGMT-H) and MGMT-low (MGMT-L) tumors. A comprehensive transcriptome analysis was conducted to explore the tumor-immune microenvironment. Furthermore, we integrated transcriptome data from 13 GBM patients operated at our institution with findings from tumor-infiltrating lymphocyte (TIL) cultures, specifically investigating their response to autologous tumors.

Results

Gene signatures associated with various immune cells, including CD8 T cells, helper T cells, B cells, and macrophages, were noted in MGMT-H tumors. Pathway analysis confirmed the enrichment of immune cell-related pathways. Additionally, biological processes involved in the activation of monocytes and lymphocytes were observed in MGMT-H tumors. Furthermore, TIL culture experiments showed a greater presence of tumor-reactive T cells in MGMT-H tumors compared to MGMT-L tumors. These findings suggest that MGMT-H tumors has a potential for enhanced immune response against tumors mediated by CD8 T cells.

Conclusion

Our study provides novel insights into the immune cell composition of MGMT-H tumors, which is characterized by the infiltration of type 1 helper T cells and activated B cells, and also the presence of tumor-reactive T cells evidenced by TIL culture. These findings contribute to a better understanding of the immune response in MGMT-H tumors, emphasizing their potential for immunotherapy. Further studies are warranted to investigate on the mechanisms of MGMT expression and antitumor immunity.

Alterations in Intratumoral Immune Response before and during Early-On Nivolumab Treatment for Unresectable Advanced or Recurrent Gastric Cancer

We investigated the tumor immune response in gastric cancer patients receiving third-line nivolumab monotherapy to identify immune-related biomarkers for better patient selection. Nineteen patients (10 males, median age 67 years) who received nivolumab as a third- or later-line therapy were enrolled. We analyzed the tumor immune response in durable clinical benefit (DCB) and non-DCB patients. Pre-treatment and early-on-treatment tumor transcriptomes were examined, and gene expression profiles, immunograms, and T cell receptor (TCR) repertoire were analyzed. DCB was observed in 15.8% of patients, with comparable secondary endpoints (ORR; objective response rate, OS; overall survival, PFS; progression-free survival) to previous trials. The immunograms of individual subjects displayed no significant changes before or early in the treatment, except for the regulatory T cell (Treg) score. Moreover, there were no consistent alterations observed among cases experiencing DCB. The intratumoral immune response was suppressed by previous treatments in most third- or later-line nivolumab recipients. TCR repertoire analysis revealed newly emerged clonotypes in early-on-treatment tumors, but clonal replacement did not impact efficacy. High T cell/Treg ratios and a low UV-radiation-response gene signature were linked to DCB and treatment response. This study emphasizes the tumor immune response's importance in nivolumab efficacy for gastric cancer. High T cell/Treg ratios and specific gene expression signatures show promise as potential biomarkers for treatment response. The tumor-infiltrating immune response was compromised by prior treatments in third-line therapy, implying that, to enhance immunotherapeutic outcomes, commencing treatment at an earlier stage might be preferable. Larger cohort validation is crucial to optimize immune-checkpoint inhibitors in gastric cancer treatment.

Pulmonary abscess caused by Cladosporium cladosporioides after receiving outpatient chemotherapy

Cladosporium cladosporioides is one of the most ubiquitous dematiaceous fungi that seldomly occur human infection. Here, we demonstrate a rare case of pulmonary phaeohyphomycosis with a distinctive pulmonary lesion during the nadir period of outpatient chemotherapy against endometrial cancer. In addition to severe neutropenia, excessive exposure to C. cladosporioides at patient's residence was considered as dominant causative factor. More caution is considered necessary for pulmonary phaeohyphomycosis in patients who receive outpatient chemotherapy and are homebound during neutropenic status.

Predictive values of immune indicators on respiratory failure in the early phase of COVID-19 due to Delta and precedent variants

Background

Immune response indicators in the early phase of COVID-19, including interferon and neutralizing responses against SARS-CoV-2, which predict hypoxemia remains unclear.

Methods

This prospective observational study recruited patients hospitalized with COVID-19 (before emergence of omicron variant). As the immune indicators, we assessed the serum levels of IFN-I/III, IL-6, CXCL10 and VEGF, using an ELISA at within 5 days after the onset of symptoms, and serum neutralizing responses using a pseudovirus assay. We also assessed SARS-CoV-2 viral load by qPCR using nasal-swab specimens and serum, to assess the association of indicators and viral distribution.

Results

The study enrolled 117 patients with COVID-19, of which 28 patients developed hypoxemia. None received vaccine before admission. Serum IFN-I levels (IFN-α and IFN-β), IL-6, CXCL10, LDH and CRP were significantly higher in patients who developed hypoxemia. A significant association with nasopharyngeal viral load was observed only for IFN-I. The serum levels of IFN-α, IL-6, CXCL10 were significantly associated with the presence of RNAemia. Multivariable analysis showed higher odds ratio of IFN-α, with cut-off value of 107 pg/ml, in regard to hypoxemia (Odds ratio [OR]=17.5; 95% confidence interval [CI], 4.7-85; p<0.001), compared to those of IL-6, >17.9 pg/ml (OR=10.5; 95% CI, 2.9-46; p<0.001).

Conclusions

This study demonstrated that serum IFN-α levels in the early phase of SARS-CoV-2 infection strongly predict hypoxemic respiratory failure in a manner different from that of the other indicators including IL-6 or humoral immune response, and instead sensitively reflect innate immune response against SARS-CoV-2 invasion.

Immunotherapies targeting neoantigens are effective in PD-1 blockade-resistant tumors

Only a small fraction of tumor-infiltrating lymphocytes can specifically recognize and attack cancer cells in PD-1/PD-L1 blockade therapy. Here, we investigate approaches to expand the neoantigen-specific CD8⁺ T cells to overcome the difficulties in treating PD-1/PD-L1 blockade-resistant tumors. Mutation-associated neoepitopes of murine nonsmall cell lung cancer ASB-XIV were estimated by whole-exome and RNA sequencing and predicted by MHC-I binding affinity (FPKM >1) in silico. Using ASB-XIV-specific CD8⁺ T cells, we screened a panel of 257 neoepitope peptides derived from ASB-XIV missense and indel mutations. Mutated Phf3 peptide (mPhf3) was successfully identified as an immunogenic neoepitope. Prophylactic mPhf3-DC vaccination inhibited ASB-XIV tumor growth through CD8⁺ T cell-mediated antitumor immunity. Combining the mPhf3-DC vaccine and anti-PD-1 treatment elicited robust antitumor activity through the induction of mPhf3-specific CD8⁺ T cells in the tumor microenvironment. Furthermore, the adoptive transfer of mPhf3-specific CD8⁺ T cells eradicated ASB-XIV tumors. Likewise, the combination of mutated Cdt1 peptide (mCdt1)-DC vaccine and anti-PD-1 treatment or adoptive transfer of mCdt1-specific CD8⁺ T cells also led to significant regression of PD-1 blockade-resistant murine gastric YTN16 tumors. In conclusion, a novel immunogenic neoepitope of ASB-XIV was identified for immunotherapy targeting neoantigens. Identification of immunogenic neoantigens can extend the therapeutic strategies by increasing the frequency of neoantigen-specific T cells, even for PD-1/PD-L1 blockade-resistant tumors.

An IL-12-Based Nanocytokine Safely Potentiates Anticancer Immunity through Spatiotemporal Control of Inflammation to Eradicate Advanced Cold Tumors

Treatment of immunologically cold tumors is a major challenge for immune checkpoint inhibitors (ICIs). Interleukin 12 (IL-12) can invigorate ICIs against cold tumors by establishing a robust antitumor immunity. However, its toxicity and systemic induction of counteracting immunosuppressive signals have hindered translation. Here, IL-12 activity is spatiotemporally controlled for safely boosting efficacy without the stimulation of interfering immune responses by generating a nanocytokine that remains inactive at physiological pH, but unleashes its full activity at acidic tumor pH. The IL-12-based nanocytokine (Nano-IL-12) accumulate and release IL-12 in tumor tissues, eliciting localized antitumoral inflammation, while preventing systemic immune response, counteractive immune reactions, and adverse toxicities even after repeated intravenous administration. The Nano-IL-12-mediated spatiotemporal control of inflammation prompt superior anticancer efficacy, and synergize with ICIs to profoundly inflame the tumor microenvironment and completely eradicate ICI-resistant primary and metastatic tumors. The strategy could be a promising approach toward safer and more effective immunotherapies.

Effect of M2-like macrophages of the injured-kidney cortex on kidney cancer progression

Chronic kidney disease (CKD) affects kidney cancer patients' mortality. However, the underlying mechanism remains unknown. M2-like macrophages have pro-tumor functions, also exist in injured kidney, and promote kidney fibrosis. Thus, it is suspected that M2-like macrophages in injured kidney induce the pro-tumor microenvironment leading to kidney cancer progression. We found that M2-like macrophages present in the injured kidney promoted kidney cancer progression and induced resistance to anti-PD1 antibody through its pro-tumor function and inhibition of CD8⁺ T cell infiltration. RNA-seq revealed Slc7a11 was upregulated in M2-like macrophages. Inhibition of Slc7a11 with sulfasalazine inhibited the pro-tumor function of M2-like macrophages and synergized with anti-PD1 antibody. Moreover, SLC7A11-positive macrophages were associated with poor prognosis among kidney cancer patients. Collectively, this study dissects the characteristic microenvironment in the injured kidney that contributed to kidney cancer progression and anti-PD1 antibody resistance. This insight offers promising combination therapy with anti-PD1 antibody and macrophage targeted therapy.

Principal component analysis of early immune cell dynamics during pembrolizumab treatment of advanced urothelial carcinoma

Immune checkpoint inhibitors have been approved as second-line therapy for patients with advanced urothelial carcinoma (UC). However, which patients will obtain clinical benefit remains to be determined. To identify predictive biomarkers for the pembrolizumab (PEM) response early during treatment, the present study investigated 31 patients with chemotherapy-resistant recurrent or metastatic UC who received 200 mg PEM intravenously every 3 weeks. Blood was taken just before the first dose and again before the second dose, and the peripheral blood mononuclear cells of all 31 pairs of blood samples were immune phenotyped by flow cytometry. Data were assessed by principal component analysis (PCA), correlation analysis and Cox proportional hazards modeling in order to comprehensively determine the effects of PEM on peripheral mononuclear immune cells. Absolute counts of CD45RA+CD27-CCR7- terminally differentiated CD8+ T cells and KLRG1+CD57+ senescent CD8+ T cells were significantly increased after PEM administration (P=0.042 and P=0.043, respectively). Senescent and exhausted CD4⁺ and CD8⁺ T cell dynamics were strongly associated with each other. By contrast, counts of monocytic myeloid-derived suppressor cells (mMDSCs) were not associated with other immune cell phenotypes. The results of PCA and non-hierarchical clustering of patients suggested that excessive T cell senescence and differentiation early during treatment were not necessarily associated with a survival benefit. However, decreased mMDSC counts after PEM were associated with improved overall survival. In conclusion, early on-treatment peripheral T cell status was associated with response to PEM; however, it was not associated with clinical benefit. By contrast, decreased peripheral mMDSC counts did predict improved overall survival.

Immuno-genomic profiling of biopsy specimens predicts neoadjuvant chemotherapy response in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is one of the most aggressive cancers and is primarily treated with platinum-based neoadjuvant chemotherapy (NAC). Some ESCCs respond well to NAC. However, biomarkers to predict NAC sensitivity and their response mechanism in ESCC remain unclear. We perform whole-genome sequencing and RNA sequencing analysis of 141 ESCC biopsy specimens before NAC treatment to generate a machine-learning-based diagnostic model to predict NAC reactivity in ESCC and analyzed the association between immunogenomic features and NAC response. Neutrophil infiltration may play an important role in ESCC response to NAC. We also demonstrate that specific copy-number alterations and copy-number signatures in the ESCC genome are significantly associated with NAC response. The interactions between the tumor genome and immune features of ESCC are likely to be a good indicator of therapeutic capability and a therapeutic target for ESCC, and machine learning prediction for NAC response is useful.

•

Four different immune subtypes from RNA-seq of ESCC biopsy specimen

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Neutrophils within tumors are associated with tumor sensitivity to NAC

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Specific copy-number changes and signatures in ESCC are associated with NAC response

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Machine learning prediction for NAC response using immunogenomics of ESCC is useful

Abstract 2072: pH-activatable IL-12-loaded polymeric micelles safely enhance antitumor efficacy as monotherapy and in combination with immune checkpoint inhibitors

Background: IL-12 is a pro-inflammatory cytokine with antitumor potential that activates both innate and adaptive immunity. However, IL-12 shows poor pharmacokinetics and intolerable toxicities due to unspecific distribution. Herein, we present pH-sensitive polymeric micelles loading IL-12 (IL-12/m) that release fully active IL-12 after sensing intratumoral pH to safely potentiate immunotherapy.

Methods: IL-12/m with 40 nm in diameter were prepared by self-assembly in phosphate buffer. The IL-12 release was tested at different pH. The stimulation of IFN-γ release from IL-12 and IL-12/m was studied in mouse splenocytes. Pharmacokinetic, pharmacodynamic, and antitumor activity were studied in immunosuppressed (B16F10 and 4T1) mouse tumor models (staged ≥ 200 mm3) and in a lung metastasis model (4T1). The safety of IL-12 was evaluated by tracing levels of cytokines and blood markers of toxicity.

Results: IL-12/m selectively activated at intratumoral pH 6.5, releasing more than 80% of IL-12 in 24 h. While IL-12/m did not induce IFN-γ production in splenocytes, the released IL-12 showed similar activity to native IL-12. In mice, IL-12/m prolonged blood circulation with minimal leakage, yielding a 3-fold longer half-life than IL-12. Moreover, the accumulation in tumor for IL-12/m (7.5%ID/g of tumor) was 3-fold higher compared that of free IL-12, with more than 90% of IL-12/m being activated. The tumors treated with IL-12/m showed 2-3-fold higher levels of IFN-γ, IL-6 and TNF-α than those treated with IL-12, whereas anti-inflammatory IL-10 was 2-fold lower for IL-12/m. In blood and organs, IL-12/m lowered the cytokine levels compared to IL-12. Also, IL-12/m avoided the tachyphylaxis of IL-12 without peak effects of IFN-γ, and the blood markers of toxicity, i.e., BUN, ALT and AST, remained close to control levels, supporting the tumor selective activation of IL-12/m. IL-12/m was efficacious in the B16F10 tumor model (10 µg iv 3 injections every 4 days) as monotherapy, and in combination with anti-PD-1 (10 mg/kg IP 3 injections every 4 days), which led to 6 of 10 complete regressions (CR). IL-12/m was also effective at 1 µg (5 injections every 2 days) against 4T1 tumors. IL-12/m increase the number and activation of CD8+ T cells and NK cells in tumors. The combination of IL-12/m (10 µg iv 3 injections every 4 days) with anti-PD1 and anti-CTLA-4 (both 10 mg/kg IP 3 injections every 4 days) achieve complete CR in a spontaneous model of lung metastasis. Responders showed immunological memory after being rechallenged with fresh tumor cells.

Conclusions: IL-12/m, a pH-activated polymeric micelle loading IL-12, masked the activity of IL-12 in healthy tissues, while it unleashed full potency of IL-12 in tumors, improving tolerability and efficacy. IL-12/m presented greater antitumor activity than IL-12 as monotherapy and in combination with immune checkpoint inhibitors.

Citation Format: Horacio Cabral, Pengwen Chen, Kazuhiko Kakimi, Kazunori Kataoka, Takuya Miyazaki, Koji Nagaoka. pH-activatable IL-12-loaded polymeric micelles safely enhance antitumor efficacy as monotherapy and in combination with immune checkpoint inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2072.

Selection of RNA-based evaluation methods for tumor microenvironment by comparing with histochemical and flow cytometric analyses in gastric cancer

Understanding the tumor microenvironment (TME) and anti-tumor immune responses in gastric cancer are required for precision immune-oncology. Taking advantage of next-generation sequencing technology, the feasibility and reliability of transcriptome-based TME analysis were investigated. TME of 30 surgically resected gastric cancer tissues was analyzed by RNA-Seq, immunohistochemistry (IHC) and flow cytometry (FCM). RNA-Seq of bulk gastric cancer tissues was computationally analyzed to evaluate TME. Computationally analyzed immune cell composition was validated by comparison with cell densities established by IHC and FCM from the same tumor tissue. Immune cell infiltration and cellular function were also validated with IHC and FCM. Cell proliferation and cell death in the tumor as assessed by RNA-Seq and IHC were compared. Computational tools and gene set analysis for quantifying CD8⁺ T cells, regulatory T cells and B cells, T cell infiltration and functional status, and cell proliferation and cell death status yielded an excellent correlation with IHC and FCM data. Using these validated transcriptome-based analyses, the immunological status of gastric cancer could be classified into immune-rich and immune-poor subtypes. Transcriptome-based TME analysis is feasible and is valuable for further understanding the immunological status of gastric cancer.

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

Simple Summary

Despite the success of immune checkpoint inhibitors (ICI) for treating a variety of solid cancers, most gastric cancer patients are resistant to ICI monotherapies. Combinations of ICI with other therapies may be able to overcome this resistance. In order to develop combination immunotherapies, immunologically well-characterized preclinical gastric cancer models are required. To this end, in the present study, we characterized two murine gastric cancer cell lines, namely, YTN2 which spontaneously regresses, and YTN16 which grows progressively. Although anti-CTLA-4 monotherapy eradicated most YTN16 tumors, these were resistant to either anti-PD-1 or anti-PD-L1 treatment. Furthermore, we identified neoantigens in YTN2 and YTN16 tumors and conducted neoantigen-based immunotherapy for these tumors. In addition, the information on neoantigens facilitates the evaluation of tumor-specific immune responses induced by the combination therapies. These immunologically well-characterized gastric cancer models will contribute to the development of novel combination immunotherapies.

Abstract

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.

913 A murine gastric cancer YTN16 model for the rational design of combination immunotherapy

Background

Although Immune checkpoint blockade (ICB) has changed the standard of care of cancer, ICB monotherapy is largely ineffective in patients with solid cancer. Therefore, the rational combination of ICB with other treatment modalities is warranted. We have recently established chemically induced gastric cancer cell line YTN16, transplantable in immune-competent mice,1 and showed that inhibition of FGFR4 signaling suppressed the YTN16 tumor growth. We also demonstrated the depletion of IL-17-producing T cells in YTN16 tumors enhanced the anti-tumor effects of anti-PD-1 treatment.2 In this study, we identified the neoantigens of YTN16 to monitor the dynamics of tumor-specific CD8< sup >+</sup > T cells in response to combination immunotherapy.

Methods

Whole-exome and transcriptome sequencing analyses were performed to identify missense mutations. As a result, candidate neoepitopes were predicted as follows; FPKM≧25, variant allele frequency in RNAseq≧0.04, IC50 of NetMHCpan≦250nM, EL rank of NetMHCpan≦0.5 and presentation percentile of MHCflurry≦0.5.

Results

Exome sequencing identified 3,347 missense mutations in the YTN16 tumor. We synthesized 11 candidate neoepitope peptides and screened their reactivity to YTN16-reactive CD8< sup >+</sup > T cell lines established from YTN16-rejected mice by ICB. Out of 11 peptides, five peptides (3 neoantigens, m(mutated)Cdt1, mScarb2 and mZfp106) induced IFNγ production in YTN16-reactive CD8< sup >+</sup > T cells. MHC class I dimer assay identified these three neoantigen-specific T cells in YTN16 tumors. Anti-CTLA-4, but not anti-PD-1 increased neoantigen-specific T cells and completely eradicated tumors. Adoptive transfer of neoantigen-reactive CD8< sup >+</sup > T cell lines and therapeutic vaccines of DCs pulsed with neoantigen short or long peptides inhibited YTN16 growth. Neoantigen-specific TCRs were cloned from neoantigen-reactive CD8< sup >+</sup > T cell lines and retrovirally transduced to activated CD8< sup >+</sup > T cells. TCR-transduced T cells killed YTN16 in vitro and adoptive transfer of TCR-transduced T cells showed anti-tumor effects. These results indicated that these three neoantigens were de fact neoantigens.

Conclusions

We identified three neoantigens that induced CD8< sup >+</sup > T cell response with anti-tumor effects in YTN16. Thus, YTN16 is a well-characterized murine gastric cancer model for rational design and optimization of combination immunotherapy.

References

Yamamoto M, Nomura S, Hosoi A, Nagaoka K, Iino T, Yasuda T, Saito T, Matsushita H, Uchida E, Seto Y, Goldenring JR, Kakimi K, Tatematsu M, Tsukamoto T. Established gastric cancer cell lines transplantable into C57BL/6 mice show fibroblast growth factor receptor 4 promotion of tumor growth. Cancer Sci 2018;109(5):1480–1492.

Nagaoka K, Shirai M, Taniguchi K, Hosoi A, Sun C, Kobayashi Y, Maejima K, Fujita M, Nakagawa H, Nomura S, Kakimi K. Deep immunophenotyping at the single-cell level identifies a combination of anti-IL-17 and checkpoint blockade as an effective treatment in a preclinical model of data-guided personalized immunotherapy. J Immunother Cancer 2020;8(2):e001185.

579 Exploiting tumor neoantigen-targeted immunotherapy in immunologically hot versus cold murine lung cancer models

Background

The treatment of non-small cell lung cancer has been altered by immune-checkpoint therapy in the last 10 years. However, many patients still do not respond to it or, eventually, the disease progresses. One of the factors leading to primary resistance to ICI is the ”cold” tumor, characterized by the absence of T cell infiltration and not sufficiently primed for immune recognition. Here, we compared the neoantigen-based immunotherapy in two lung cancer cell lines: T cell-inflamed ASB-XIV and non-T cell-inflamed LLC1.

Methods

Whole-exome and RNA sequencing were performed to identify neoantigens. First, MHC binding scores of expressed mutated peptides (FPKM>1) were estimated to select candidate neoantigens. Next, the immunogenicity of predicted mutated peptides was investigated. Then, the anti-tumor effect of immunogenic mutated peptides was accessed. Finally, immunosuppressive molecules in the non-T cell inflamed tumor microenvironment were investigated and targeted for effective treatment.

Results

Inflamed ASB-XIV tumors were sensitive to ICI, while non-inflamed LCC1 tumors were resistant to ICI. Using ASB-XIV-specific CTLs, we screened the panel of candidate neoantigen peptides and identified Phf3 N1867K mutated peptide as neoepitope. Mutated Phf3 peptide-pulsed DCs induced peptide-specific CD8+ T cells and inhibited the ASB-XIV tumor growth in the prophylactic and therapeutic setting. Furthermore, adoptive transfer of mPhf3-specific CTLs also eradicated the ASB-XIV tumors. In the case of LLC1, twenty-five out of 132 short mutated peptides induced peptide-specific CD8+ T cell response, but they could not inhibit the LLC1 tumor growth. DC vaccines pulsed with long peptides (LP) induced both CD4+ and CD8+ T cell responses ex vivo. Of them, DC pulsed with LP82 partly delayed the LLC1 growth in vivo. By RNA-Seq, CD38 was highly expressed in LLC1. Thereby, an anti-CD38 antibody was administered in LLC1-bearing mice immunized with DC pulsed with LP82. The tumor growth was suppressed in the combination treatment, partly because CD38 blockade decreased regulatory T cells in the tumor.

Conclusions

Responses to neoantigen-targeted immunotherapy preferentially observed in T cell-inflamed tumors. Regulation of immunosuppressive tumor microenvironment is required to make neoantigen-targeted immunotherapy effective in non-inflamed tumors.

647 Possibility of immunotherapy for the glioblastoma patients with O6-methyl-guanine DNA methyltransferase (MGMT) expression or promoter unmethylated

Background

It has been widely accepted that O6-methyl-guanine DNA methyltransferase (MGMT) promoter methylation in glioblastoma is associated with a benefit from temozolomide (TMZ) treatment. MGMT is a DNA repair protein that removes the cytotoxic O6-methylguanine (O6MG) DNA lesions generated by TMZ; thereby, MGMT expression is mechanistically linked to TMZ resistance. However, thus far, there is no effective treatment for these patients with MGMT promoter unmethylated. Therefore, a new treatment for GBM patients with MGMT expression is urgently needed.1 2 To this end, we examined the tumor microenvironment in GBM with or without MGMT expression.

Methods

Based on The Cancer Genome Atlas (TCGA) primary GBM cohort, the tumor-infiltrating lymphocyte expression level was calculated using the CIBERSORTx algorithms and the single-sample Gene Set Enrichment Analysis (ssGSEA) method. Furthermore, the differential expression gene analysis was conducted and pathway analysis was performed using Ingenuity Pathway Analysis (IPA). The results were validated using the GBM cohort from the Chinese Glioma Genome Atlas (CGGA) database. In addition, tumor-infiltrating lymphocytes (TILs) were isolated from 13 surgically removed primary GBM tumors in our institution. Their responses to autologous tumors were evaluated by IFNγ ELISA.

Results

T cells CD8 score by CIBERSORTx was significantly higher in the MGMT-high tumor. Similarly, ssGSEA scores for activated CD8 T cell, Macrophage, activated B cell, and Type 1 T helper cell were significantly higher in the MGMT-high tumor. Conversely, T cells CD4 naive was significantly higher in the MGMT-low tumor. These results indicate that more immune cell infiltration is associated with MGMT-high tumors. Consistently, tumor-reactive TILs were detected in the MGMT-high tumor. Pathway analysis showed that oxidative phosphorylation (OXPHOS) was highly enriched in the MGMT-high tumor.There were many CD8 T cells and tumor-reactive T cells in the MGMT-high tumors. However, it has been reported that anti-PD-1/PD-L1 monotherapy was not effective in glioblastoma. In this study, we demonstrated that OXPHOS was highly activated in the MGMT-high tumors. Thus, metabolic therapy can be combined with immunotherapy in these MGMT-high tumors to enhance anti-tumor immune responses.

Conclusions

Although MGMT-high tumors are resistant to TMZ, the existence of immune cell infiltration in the tumor microenvironment of MGMT-high tumors suggest the potential of immunotherapy in these patients.

References

Stupp R, Hegi ME, Mason WP, van den Bent MJ, Taphoorn MJB, Janzer RC, Ludwin SK, Allgeier A, Fisher B, Belanger K, Hau P, Brandes AA, Gijtenbeek J, Marosi C, Vecht CJ, Mokhtari K, Wesseling P, Villa S, Eisenhauer E, Gorlia T, Weller M, Lacombe D, Cairncross Jy, Mirimanoff R-O, European Organisation for Research and Treatment of Cancer Brain Tumour and Radiation Oncology Groups; National Cancer Institute of Canada Clinical Trials Group. Lancet Oncol 2009;10(5):459–66.

Wick W, Weller M, van den Bent M, Sanson M, Weiler M, von Deimling A, Plass C, Hegi M, Platten M, Reifenberger G. Nat Rev Neurol 2014;;10(7):372–85.

Ethics Approval

G3545-(26)

Consent

Written informed consent was obtained from the patient for publication of this abstract and any accompanying images. A copy of the written consent is available for review by the Editor of this journal.

64 A cloning and expression system of the neoantigen-specific TCRs from tumor-infiltrating lymphocytes by single-cell sequencing of paired TCRα and TCRβ chains

Background

T-cells that target tumor neoantigens arising from cancer mutations are the primary mediators of cancer immunotherapies. Identifying neoantigens and T-cells that recognize them is essential for T-cell-based immunotherapy. However, neoantigen-reactive Tumor-infiltrating lymphocytes (TILs) are highly differentiated or exhausted with a limited proliferative capacity; it is challenging to expand them for a sufficient number to probe their specificity. Therefore, we developed a novel cloning and expression system to examine TCRs discovered by single-cell sequencing of TILs for their neoantigen-specificity.

Methods

TILs of lung cancer and sarcoma were analyzed. Surgically removed tumors were divided into several pieces. They were enzymatically digested to prepare fresh tumor digest (FTD) and cryopreserved. They were used to generate TIL cultures and perform WES and RNA-Seq to identify tumor-specific mutations. MHCflurry was used to predict the binding affinity of potential epitopes arising from these mutations to HLA class I. Peptides that were predicted to bind to patients‘ own MHC class I molecules strongly were then synthesized. Single TILs isolated with the ICELL8® cx system (Takara Bio) were dispensed into a nanowell TCR chip containing preprinted barcodes. Barcoded cDNAs were PCR-amplified in-chip, pooled off-chip, and used as a template in the TCR-specific PCR or for the whole transcriptome library generation of 5’ ends of all transcripts. Based on single-cell transcriptome data and TCR profiles of TILs, we predict and prioritize neoantigen-specific TCRs and cloned them into siTCR® retrovirus vectors. These TCRs were transduced into SUP-T1-based reporter cells in which ZsGreen fluorescent protein expression is controlled by AP-1 and NFAT binding sites. TCR-expressing reporter cells were cocultured with patient autologous APCs pulsed with a pool of candidate neoantigen peptides. ZsGreen expression indicates that TCRs match their cognate neoantigens.

Results

In a lung cancer patient, we set up 18 TIL cultures and obtained 12 TILs. TILs were cocultured with FTD; IFN-γ production was measured by ELISA to evaluate their reactivity to the autologous tumor. NGS identified 197 somatic mutations, 4 fusion genes, and 8 highly expressed cancer-testis antigens. Among them, 339 candidate peptides were synthesized and screened. In addition, we cloned 3 pairs of TCRαβ chains from most expanded TIL cultures and 4 TCRs from ex vivo TILs with exhausted phenotype. Two reporter cells that express TCRs from exhausted TILs responded to the same neoantigen peptide.

Conclusions

Generating TCR expressing cell lines facilitated the identifying neoantigens and their cognate TCR sequences from patients.

Ethics Approval

G3545

Deep immunophenotyping at the single-cell level identifies a combination of anti-IL-17 and checkpoint blockade as an effective treatment in a preclinical model of data-guided personalized immunotherapy

BACKGROUND

Although immune checkpoint blockade is effective for several malignancies, a substantial number of patients remain refractory to treatment. The future of immunotherapy will be a personalized approach adapted to each patient's cancer-immune interactions in the tumor microenvironment (TME) to prevent suppression of antitumor immune responses. To demonstrate the feasibility of this kind of approach, we developed combination therapy for a preclinical model guided by deep immunophenotyping of the TME.

METHODS

Gastric cancer cell lines YTN2 and YTN16 were subcutaneously inoculated into C57BL/6 mice. YTN2 spontaneously regresses, while YTN16 grows progressively. Bulk RNA-Seq, single-cell RNA-Seq (scRNA-Seq) and flow cytometry were performed to investigate the immunological differences in the TME of these tumors.

RESULTS

Bulk RNA-Seq demonstrated that YTN16 tumor cells produced CCL20 and that CD8⁺ T cell responses were impaired in these tumors relative to YTN2. We have developed a vertical flow array chip (VFAC) for targeted scRNA-Seq to identify unique subtypes of T cells by employing a panel of genes reflecting T cell phenotypes and functions. CD8⁺ T cell dysfunction (cytotoxicity, proliferation and the recruitment of interleukin-17 (IL-17)-producing cells into YTN16 tumors) was identified by targeted scRNA-Seq. The presence of IL-17-producing T cells in YTN16 tumors was confirmed by flow cytometry, which also revealed neutrophil infiltration. IL-17 blockade suppressed YTN16 tumor growth, while tumors were rejected by the combination of anti-IL-17 and anti-PD-1 (Programmed cell death protein 1) mAb treatment. Reduced neutrophil activation and enhanced expansion of neoantigen-specific CD8⁺ T cells were observed in tumors of the mice receiving the combination therapy.

CONCLUSIONS

Deep phenotyping of YTN16 tumors identified a sequence of events on the axis CCL20->IL-17-producing cells->IL-17-neutrophil-angiogenesis->suppression of neoantigen-specific CD8⁺ T cells which was responsible for the lack of tumor rejection. IL-17 blockade together with anti-PD-1 mAb therapy eradicated these YTN16 tumors. Thus, the deep immunological phenotyping can guide immunotherapy for the tailored treatment of each individual patient's tumor.

Abstract 1571: Neoantigen vaccine plus CD38 blockade suppress the proliferation of murine cold lung cancer LLC1

Immune checkpoint inhibitors are now the mainstay for the treatment of lung cancer. However, so-called cold tumors are known to be resistant to checkpoint inhibitors. Neoantigens associated with genetic mutations of the tumor have the potential to stimulate a potent and highly specific immune response. To develop effective immunotherapy for cold lung cancer, we examined whether neoantigen-based immunotherapy can develop immune responses and display anti-tumor effects on the cold lung cancer model, Lewis lung carcinoma cells (LLC1) resistant to anti-CTLA-4 or anti-PD-1 therapy.

LLC1 cells were subjected to whole-exome and RNA sequencing. Mutation-associated neoantigens were predicted and prioritized by their affinity to MHC class I molecules and their expression. Using netMHCpan, sixty mutated peptides with IC50 &lt;200 nM and 68 mutated peptides with IC50&gt;200 nM, but the wild to corresponding mutated peptide ratio of binding affinity&gt;10 were selected as candidate neoantigens. C57BL/6 mice were immunized with dendritic cells pulsed with these neoantigen short peptides (8-10mer). Twenty-five out of 128 short mutated peptides induced peptide-specific CD8+ T cell response to some extent. Next, 25 long peptides (21mer), which incorporated corresponding immunogenic short peptide sequences, were synthesized and used to immunize mice. DC vaccines pulsed with neoantigen in long peptide format (LP) induced both CD4+ and CD8+ T cell response ex vivo. Of them, DC pulsed with LP82 partly delayed the LLC1 growth in vivo.

By RNA-Seq, CD38 was highly expressed in LLC1. Thereby, an anti-CD38 antibody was administered in LLC1-bearing mice immunized with DC pulsed with LP82. The tumor growth was suppressed in the combination treatment. Although CD38 plays an important role in converting nicotinamide adenine dinucleotide (NAD+) to adenosine, adenosine receptor antagonist could not inhibit the tumor growth in mice immunized with LP82. Alternatively, NAD+ accumulation due to CD38 blockade decreased regulatory T cells in the tumor immune microenvironment, consistent with the decreased Foxp3+ transcription and increased IFNg and IL2 production of CD4+ T cells sorted from tumor immune microenvironment.

Our study suggested that the prioritization of neoantigens that can induce anti-tumor response is critical for developing neoantigen-targeting immunotherapy. Combining an effective neoantigen vaccine and precise immune modulator could enhance anti-tumor activities even in cold lung tumors.

Citation Format: Changbo Sun, Koji Nagaoka, Akihiro Hosoi, Yukari Kobayashi, Jun Nakajima, Kazuhiro Kakimi. Neoantigen vaccine plus CD38 blockade suppress the proliferation of murine cold lung cancer LLC1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1571.

Presence of low voltage area predicts atrial tachyarrhythmia inducibility with atrial burst pacing after pulmonary vein isolation

Background

Induction of atrial fibrillation (AF)/atrial tachycardia (AT) by atrial burst pacing following ablation procedure may reflect the presence of residual substrates in the atria that maintain AF. However, the relation between the inducibility and left atrial low voltage area (LVA) has not been established.

Methods

Fifty-nine patients (65 years old, 43 males) with persistent AF who underwent pulmonary vein isolation (PVI)-based ablation were studied. All patients underwent left atrial voltage mapping during sinus rhythm and atrial burst pacing after PVI. Atrial burst pacing was performed with 30-beat at an amplitude of 10V from the ostium of the coronary sinus; increasing from 240 to 320 ppm in steps of 20 ppm or failure to 1:1 atrial capture. Inducibility was defined as AF/AT lasting more than 5 minutes following burst pacing. Left atrial LVA and other co-variates were analyzed with regard to burst pacing positivity.

Results

AF/AT was induced by burst pacing in 23 patients (39%). Univariate analysis revealed that past history of stroke, CHADS2 score and presence of left atrial LVA were significantly associated with the inducibility of AF/AT. Multivariate analysis revealed that only the presence of LVA was associated with the inducibility (OR 1.5: per 10% increase; p=0.04). We focused on the relationship between the extent of LVA and burst positivity. AF/AT inducibility increased as low voltage area increased, and it was as high as 72.7% when low voltage area was more than 20% (P&lt;0.05). Interestingly, induced arrhythmia type was AT rather than AF when low voltage area was more than 20%.

Conclusions

Presence of left atrial LVA is an independent predictor of atrial tachyarrhythmia inducibility after PVI in patients with persistent AF. A large amount of low voltage area is related to AT inducibility rather than AF.

Extent of LVA and burst positivity

Funding Acknowledgement

Type of funding source: None

Integrative immunogenomic analysis of gastric cancer dictates novel immunological classification and the functional status of tumor-infiltrating cells

Objectives

A better understanding of antitumor immunity will help predict the prognosis of gastric cancer patients and tailor the appropriate therapies in each patient. Therefore, we propose a novel immunological classification of gastric cancer.

Methods

We performed whole‐exome sequencing (WES), RNA‐Seq and flow cytometry in 29 gastric cancer patients who received surgery. The TCGA data set of 323 gastric cancer patients and RNA‐Seq data of 45 patients who received pembrolizumab (Kim et al. Nat Med 2018; 24: 1449–1458) were also analysed.

Results

Immunogram analysis of cancer–immunity interaction of gastric cancer revealed immune signatures of four main types, designated Hot1, Hot2, Intermediate and Cold. Immunologically hot tumors displayed a dysfunctional T‐cell signature, while cold tumors had an exclusion signature. Ex vivo tumor‐infiltrating lymphocyte analysis documented T‐cell dysfunction with the expression of checkpoint molecules and impaired cytokine production. The T‐cell function was more profoundly damaged in Hot1 than Hot2 tumors. Patients in Hot2 subtypes had better survival in our cohort and TCGA cohort. Although these immunological subtypes overlapped to some degree with the molecular subtypes in the TCGA, intratumoral immune responses cannot be predicted solely based on histological or molecular subtyping of gastric cancer. Molecular and immunological classifications complement each other to predict the responses to anti‐PD‐1 therapy and have the potential to be a biomarker for the treatment of gastric cancer.

Conclusion

The immunological classification of gastric cancer resulted in four subtypes. Hot tumors were further divided into two subtypes, between which the functional status of T cells was different.

Adoptive transfer of zoledronate-expanded autologous Vγ9Vδ2 T-cells in patients with treatment-refractory non-small-cell lung cancer: a multicenter, open-label, single-arm, phase 2 study

BACKGROUND

Not all non-small cell lung cancer (NSCLC) patients possess drug-targetable driver mutations, and response rates to immune checkpoint blockade therapies also remain unsatisfactory. Therefore, more effective treatments are still needed. Here, we report the results of a phase 2 clinical trial of adoptive cell therapy using zoledronate-expanded autologous Vγ9Vδ2 T-cells for treatment-refractory NSCLC.

METHODS

NSCLC patients who had undergone at least two regimens of standard chemotherapy for unresectable disease or had had at least one treatment including chemotherapy or radiation for recurrent disease after surgery were enrolled in this open-label, single-arm, multicenter, phase 2 study. After preliminary testing of Vγ9Vδ2 T-cell proliferation, autologous peripheral blood mononuclear cells were cultured with zoledronate and IL-2 to expand the Vγ9Vδ2 T-cells. Cultured cells (>1×10⁹) were intravenously administered every 2 weeks for six injections. The primary endpoint of this study was progression-free survival (PFS), and secondary endpoints included overall survival (OS), best objective response rate (ORR), disease control rate (DCR), safety and immunomonitoring. Clinical efficacy was defined as median PFS significantly >4 months.

RESULTS

Twenty-five patients (20 adenocarcinoma, 4 squamous cell carcinoma and 1 large cell carcinoma) were enrolled. Autologous Vγ9Vδ2 T-cell therapy was administered to all 25 patients, of which 16 completed the foreseen course of 6 injections of cultured cells. Median PFS was 95.0 days (95% CI 73.0 to 132.0 days); median OS was 418.0 days (179.0-479.0 days), and best overall responses were 1 partial response, 16 stable disease (SD) and 8 progressive disease. ORR and DCR were 4.0% (0.1%-20.4%) and 68.0% (46.5%-85.1%), respectively. Severe adverse events developed in nine patients, mostly associated with disease progression. In one patient, pneumonitis and inflammatory responses resulted from Vγ9Vδ2 T-cell infusions, together with the disappearance of a massive tumor.

CONCLUSIONS

Although autologous Vγ9Vδ2 T-cell therapy was well tolerated and may have an acceptable DCR, this trial did not meet its primary efficacy endpoint.

TRIAL REGISTRATION NUMBER

UMIN000006128.

Abstract 2050: Novel immunological classification of gastric cancer by integrative analysis

Traditional classifications of gastric cancer are based on gross appearance, anatomical sites, histological types, and etiologies. Recent advances in NGS technologies have made comprehensive molecular characterizations of gastric cancer possible. Four subtypes were proposed by the TCGA project, namely, EBV, MSI, GS, and CIN. These molecular subtypes are clinically relevant and contribute to the stratification of patients for targeted therapies and immunotherapies. However, understanding the landscape of the tumor-immune microenvironment is critical for improving the efficacy of current immunotherapies or developing novel combination immunotherapies. To this end, we performed whole-exome sequencing, RNA-Seq, and flow cytometry in 29 patients with primary gastric adenocarcinomas. We focused on factors related to the cancer-immunity cycle and tumor cell proliferation and metabolism using 9 selected gene sets, innate immunity, priming and activation, T cells, IFNγ response, inhibitory molecules, Tregs, recognition of tumor cells, proliferation, and glycolysis. By integrating them, we generated an immunogram for each patient to visualize the state of cancer-immune system interactions and have investigated the tumor-immune microenvironment in gastric cancer. Our results demonstrate that the anti-tumor immune response in gastric cancer is heterogeneous. Based on Immunogram analysis, the hierarchical clustering of gastric cancers from 29 patients resulted in 4 novel immunological subtypes, designated Hot 1, Hot 2, Intermediate, and Cold. Hot 1 and Hot 2 were distinguished from one another by glycolysis, which was low in the latter. These immunological subtypes overlapped to some degree with the molecular subtypes in the TCGA. All 4 MSI tumors in our cohort were included in the Hot 1 group, and all 3 EBV tumors in the Hot 2 group, whereas 4 of the 6 mesenchymal tumors fell into the Intermediate group. Immunologically hot tumors displayed a dysfunctional T cell signature, while cold tumors had an exclusion signature. We also determined the phenotypes and functions ex vivo of tumor-infiltrating T cells by flow cytometry. T cell dysfunction was confirmed by documenting very low percentages of polyfunctional CD8+ T cells producing ≥2 of the cytokines IFNγ, TNFα and IL-2 in the Hot 1 subtype. T cell function was entirely lacking in 2 of 11 Cold subtype tumors. These dysfunctional T cells could be recoverable in most patients if appropriate signals are supplied or immunosuppressive signals blocked. Applying our immunogram analysis to the TCGA cohort also resulted in its classification into four subtypes, validating the overlap between molecular and immunological subtypes. Overall survival in patients with a Hot 1 tumor was worse than for Hot 2 subtypes under conventional therapy not including checkpoint blockade, suggesting that early administration of anti-PD-1 therapy should be recommended for patients with Hot 1 tumors.

Citation Format: Yasuyoshi Sato, Ikuo Wada, Akihiro Hosoi, Yukari Kobayashi, Koji Nagaoka, Takahiro Karasaki, Hirokazu Matsushita, Koichi Yagi, Hiroharu Yamashita, Shunji Takahashi, Yasuyuki Seto, Kazuhiro Kakimi. Novel immunological classification of gastric cancer by integrative analysis [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2050.

Abstract 1550: Single-cell RNA-Seq identified an immunosuppressive IL-17 producing tumor-infiltrating T cells in murine gastric tumor model

BACKGROUND: YTN2 and YTN16 cells are chemically induced gastric cancer cell lines. YTN2 is spontaneously rejected in C57BL/6 mice in CD8+ T cell-dependent manner, while YTN16 grows progressively. To investigate the interaction of tumor microenvironment and T cells, bulk RNA-Seq of total tumor RNA and single-cell RNA-Seq of tumor-infiltrating T cells were performed in YTN2 and YTN16 gastric tumor-bearing mice.

METHOD: Tumor cells (5×106) were subcutaneously inoculated into C57BL/6 mice. On day 7, tumors were harvested, and total tumor RNA and tumor-infiltrating lymphocytes were isolated. CD8+ and CD4+ cells were sorted from YTN2 and YTN16 tumor tissues. Single-cell RNA-sequencing analysis was performed using vertical flow array chips (VAFC) for 44 T cell-related genes. IL-17 production in tumor-infiltrating T cells was evaluated by intracellular cytokine staining. Anti-IL-17(clone 17F3) and anti-PD-1(RMP1-14) mAbs were injected into YTN16 tumor-bearing mice on days 3, 6, 9, and 12 and days 6, 9, and 12, respectively.

RESULT: Bulk RNA-Seq revealed that higher gene expression of immune-related genes, including cytokines, chemokines, their receptors and checkpoint molecules, were detected in YTN2 tumors than YTN16. IL-17 expression was not detected in YTN2 or YTN16. We analyzed 1142 tumor infiltrating CD4+ and CD8+ T cells isolated from YTN2 and YTN16 tumor tissues. Unsupervised clustering of all T cells using the Louvain method identified 7 clusters, including 3 clusters (clusters 1, 4, 5) for CD8+ and 3 clusters (clusters 2, 3, 6, 7) for CD4+ T cells. Clusters 1-6 included T cells from both YTN2 and YTN16. Cluster 7 consisted of CD4+ T cells only from YTN16. CD8+ T cells in cluster 5 highly expressed Slc2a1, Ifng, Tnf, Fasl, Cxcr3, Il2rb, Il2rg, Il7r, Pdcd1, Tigit, Eomes, Bcl2, and Tbx21. In contrast, these genes were scarcely expressed in cluster 4. Cluster 1 was an intermediate phenotype of these two clusters. CD8+ T cells from YTN16, but not YTN2 in cluster 5, expressed Il17. CD4+ T cells in cluster 2 expressed Slc2a1, Tnfrsf9, Pdcd1, Clta4, Tigit, Hif-1a and Icos at high level. Cluster 2 CD4+ T cells from YTN2 expressed more Havcr2 and Tbx21 and less Il17 than those from YTN16. T cells in cluster 3 did not express these genes. Cluster 7 was characterized by high Il17 expression. By single-cell RNA-Seq analysis, IL-17-producing cells were only detected in YTN16 tumors. Consistent with single-cell analysis, we detected IL-17 producing cells in the YTN16 tumor by flow cytometry. To elucidate the function of IL-17 in the tumor, we used anti-IL-17 blocking mAb and showed that blocking of IL-17 suppressed YTN16 tumor growth. Combination therapy of anti-IL-17 and anti-PD-1 enhanced the anti-tumor effect.

CONCLUSION: Single-cell RNA-sequencing analysis, but not bulk RNA-Seq, identified IL-17-producing CD4+ T cells in YTN16 tumors and revealed an immunosuppressive role of IL-17 in progressive cancer.

Citation Format: Masataka Shirai, Koji Nagaoka, Kiyomi Taniguchi, Changbo Sun, Akihiro Hosoi, Kazuhiro Kakimi. Single-cell RNA-Seq identified an immunosuppressive IL-17 producing tumor-infiltrating T cells in murine gastric tumor model [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1550.

Abstract 6610: To identify neoantigens relevant to anti-tumor activity is challenging even with NGS-based prediction combined with MHC ligandome profiling

Background T cells that target neoantigens, which are mutant peptides encoded by tumor-specific mutations in cancer cells, have a pivotal role in response to immunotherapy. Current affordable NGS and bioinformatics have facilitated neoantigen research. However, the prediction of neoantigens in silico analysis lacks actual proof that the predicted neoantigens are indeed relevant to anti-tumor immune response. In this study, immunogenicity and anti-tumor activity of in silico predicted neoepitopes of gastric cancer cell lines, YTN2 and YTN16, were evaluated in vitro and in vivo. Besides, MHC ligandome profiling was performed on whether predicted neoantigens were presented by cancer cells.

Methods YTN2 and YTN16 are subclones established from a chemically induced murine gastric cancer (Cancer Sci. 2018;109:1480-1492). Whole-exome sequencing and microarray analysis were performed. Binding affinities of peptides with MHC-I were predicted using NetMHCpan. Peptides with IC50≤250 nM were considered as candidate neoantigen.

Results Exome sequencing identified 3329 and 3347 missense mutations in YTN2 and YTN16 tumors, respectively. Most of the mutations (3007) were common in YTN2 and YTN16. Among them, 2356 and 2166 mutations were expressed in YTN2 and YTN16, respectively. Candidate neoantigen peptides were 263 and 250 in YTN2 and YTN16, respectively. Although we detected 75 neoantigen-peptide-specific T cell responses, only six neoantigens (Cdt1, Cers4, Nlrp1a, Scarb2, Vmn2r121, and Zfp106)-specific T cells could recognize YTN2 or YTN16 cell line and produced IFNγ. To evaluate in vivo anti-tumor effects of neoantigen-specific T cells, we expanded four neoantigens (Cdt1, Nlrp1a, Vmn2r121, and Zfp106)-specific CD8+ T cell lines and injected them into YTN16 tumor-bearing mice. Only Cdt1-specific T cells completely eradicated the tumor, and Nlrp1a-specific T cells partially inhibited tumor growth. However, Vmn2r121- or Zfp106-specific CD8+ T cell lines could not inhibit the tumor growth. MHC ligandome profiling identified 424 Db-binding peptides and 228 Kb-binding peptides in YTN2, while 317 Db-binding peptides and 228 Kb-binding peptides were detected in YTN16. Almost all MHC-binding peptides had wild type sequences. Only one mutated peptide, Cdt1, was detected in YTN2 but not YTN16. Although Cdt1-specific CD8+ T cells recognized both YTN2 and YTN16. Other neoantigens, Cers4, Nlrp1a, Scarb2, Vmn2r121, and Zfp106, were not detected by MHC ligandome profiling, though T cells specific to these neoantigens responded to cancer cells.

Conclusion Currently available technologies anyhow identified neoantigens that are relevant to anti-tumor immune response. However, any single methodology is not sufficient to identify real neoantigens. Detection of neoantigen-specific T cells is still important.

Citation Format: Koji Nagaoka, Takayuki Kanaseki, Changbo Sun, Akihiro Hosoi, Serina Tokita, Kazuhiro Maejima, Masashi Fujita, Hidewaki Nakagawa, Toshihiko Torigoe, Kazuhiro Kakimi. To identify neoantigens relevant to anti-tumor activity is challenging even with NGS-based prediction combined with MHC ligandome profiling [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6610.

Different immunological effects of the molecular targeted agents sunitinib, everolimus and temsirolimus in patients with renal cell carcinoma

Treatment with molecular targeted agents together with immune checkpoint inhibitors will most likely improve the efficacy of current cancer immunotherapy. Because molecular targeted agents not only directly affect cancer cells, but also influence immune cells and modulate the tumor microenvironment, a better understanding of the overall immunological effects of these drugs will contribute to the rational design of combination therapies. Therefore, this study performed extensive immune monitoring of patients' peripheral blood mononuclear cells (PBMCs) to investigate the immunological effects of the molecular targeted agents sunitinib, everolimus and temsirolimus, which have been widely used for the treatment of renal cell carcinoma (RCC). Immunophenotyping and functional analysis of PBMCs revealed that these molecular targeted agents exerted different immunological effects on patients with RCC. Sunitinib decreased the percentage of early‑stage myeloid‑derived suppressor cells (eMDSCs) and increased natural killer cells, but did not affect the phenotypes and effector functions of CD4+ or CD8+ T cells. Everolimus decreased effector regulatory T cells, but also decreased IL‑2‑producing CD4+ T cells and increased dysfunctional CD8+ T cells. Conversely, temsirolimus decreased programmed cell death protein 1+CD8+ T cells and eMDSCs, but increased interferon‑γ and tumor necrosis factor‑α double producers at the same time as decreasing dysfunctional CD8+ T cells, albeit not significantly. In conclusion, although everolimus and temsirolimus are mTOR inhibitors, their effects on overall T‑cell functions are very different. Therefore, although it may increase the risk of immune‑related toxicity, temsirolimus is expected to offer the best outcome when combined with other immunomodulators for the development of cancer immunotherapy.

Spatial distribution of negative ion density near the plasma grid

Density distributions of negative hydrogen (H^-) ions and negative deuterium (D^-) ions were measured with the laser photodetachment method in the extraction region of the negative ion source. The distribution of H^- ion density peaks at the center of the ion source, while that of the D^- ion shows a flatter profile in the direction parallel to the plasma grid. The positive ion densities of hydrogen and deuterium estimated from the positive saturation current indicate similar profiles with different amounts close to the grid. The difference in the H^- ion and D^- ion distributions can be explained by the difference in the negative ion yield and the survival probability of the ions due to the isotope effect.

Extension of high power deuterium operation of negative ion based neutral beam injector in the large helical device

Second deuterium operation of the negative ion based neutral beam injector was performed in 2018 in the large helical device. The electron and ion current ratio improves to I_e/I_acc(D) = 0.31 using the short extraction gap distance of 7 mm between the plasma grid (PG) and the extraction grid (EG). The strength of the magnetic field by the electron deflection magnet installed in the EG increases by 17% at the PG ingress surface, which effectively reduces the electron component in the negative ion rich plasma in the vicinity of PG apertures. The reduction of the electron current made it possible to operate at a high power arc discharge and beam extraction. Then, the deuterium negative ion current increases to 55.4 A with the averaged current density of 233 A/m². The thermal load on the EG using 7 mm gap distance is 0.6 times smaller than the thermal load using a 8 mm gap caused by the reduction of coextracted electron current. The injection beam power increases to 2.9 MW in the beam line BL3, and the total beam injection power increases to 7 MW by three beam lines in the second deuterium campaign.

P3764Morphological mechanisms of atrial functional mitral regurgitation in patients with atrial fibrillation

Background

Atrial functional mitral regurgitation (AFMR) occurs in patients with atrial fibrillation. However, morphological mechanisms of AFMR are poorly understood.

Purpose

The purpose of this study was to examine the morphological characteristics in patients with AFMR.

Methods

Among consecutive 795 patients undergoing initial radiofrequency catheter ablation (RFCA) at our hospital, twenty-five patients with persistent AF accompanied by AFMR (≥ moderate) before RFCA (AFMR group) were studied. Age-matched 25 patients with persistent AF without MR were defined as a control group.

Results

Left ventricular ejection fraction (LVEF) was lower and left atrium volume index was larger in the AFMR group (Table). Mitral valve annulus diameter and length of anterior mitral leaflet (AML) were similar between groups, whereas length of posterior mitral leaflet (PML) was significantly shorter in the AFMR group. Smaller tethering angle of AML (γ in the figure) and shorter tethering height were significantly associated with the occurrence of AFMR, which were different from morphology of functional mitral regurgitation in patients with dilated LV. Multiple regression analysis revealed that less tenting height (p<0.05) and LA dilatation toward the posterior (p<0.01) were significantly related to AFMR.

Echocardiographic parameters AFMR (n=25) Control (n=25) P value Age, y 69±8 66±10 NS Male, n (%) 9 (36) 20 (80) P=0.001 LVEF,% 60±9 67±6 P=0.004 LAD, mm 44±5 41±7 NS LAVI, ml/m2 56±17 41±13 P<0.001 MV diameter, mm 3.9±0.4 3.8±0.5 NS α angle, ° 34±9 35±7 NS β angle, ° 48±9 50±8 NS γ angle, ° 32±5 37±5 P=0.0005 AML length, mm 3.0±0.5 3.0±0.5 NS PML length, mm 2.1±0.1 2.4±0.1 P=0.03 Tenting height, mm 1.5±0.1 1.8±0.1 P=0.02 D, mm 0.8±0.3 0.5±0.3 P=0.001 LVEF: left ventricular ejection fraction; LAD: left atrial diameter; LAVI: left atrial volume index; AML: anterior mitral leaflet; PML: posterior mitral leaftlet.

Conclusions

AFMR occurs in patients with unique morphological features, such as less tethering height and LA dilatation toward the posterior.

P1025Clinical predictors for the improvement of left ventricular ejection fraction and prognosis after catheter ablation of atrial fibrillation in patients with systolic dysfunction

Background

Catheter ablation (CA) of atrial fibrillation (AF) improves left ventricular ejection fraction (LVEF) and clinical outcomes in patients with left ventricular systolic dysfunction (LVSD). However, predictors of the improvement of LV function and clinical outcomes by CA were poorly understood.

Purpose

We examined the efficacy of CA in AF patients with LVSD and predictive factors associated with clinical outcomes.

Method

Among consecutive 795 patients undergone initial RFCA at our hospital, we studied 51 patients with LVSD (LVEF ≤50%). Improved LVEF more then 5% at 1-year after CA was classified as “responder” to CA. We analyzed clinical variables and echocardiographic parameters before and after the CAs.

Results

In the responder group, LVEF was significantly improved 1-year after catheter ablation compared with the non-responder group. (ΔLVEF 22±12% vs. −1±4%, p<0.001). The responder group was significantly younger, had more non-paroxysmal AF, smaller LV systolic diameter and lower plasma BNP level before CA (Table). Late gadolinium enhancement (LGE)-positive rate in cardiovascular magnetic resonance imaging (CMR) before CA was higher in the non-responder group than in the responder group (100% [6/6] vs. 38% [5/13], p<0.005). After CAs of AF, event-free survival from hospitalization for heart failure was significantly higher in the responder group (Figure) with less AF recurrence (27% vs. 47%, p=0.04) than in the non-responder group.

Baseline characteristics Responder (N=35) Non-Responder (N=16) P value Age, y 62±11 69±8 p<0.01 Male, n (%) 26 (74) 13 (76) NS Non-pAF 26 (74) 4 (24) p<0.01 LAD, mm 48±7 48±8 NS LAVI, ml/m2 54±17 58±20 NS LVDd, mm 54±7 58±10 NS LVDs, mm 43±7 48±10 p=0.05 EF, % 37±8 38±8 NS BNP (pg/ml) 278±225 684±848 p<0.05

Conclusion

Younger age, absence of LV dilatation, lower plasma BNP, or absence of LGE may well predict favorable clinical outcomes after CA in patients with LVSD.

Development of a dual beamlet monitor system for negative ion beam measurements

To evaluate negative ion beam properties, a dual beamlet monitor system has been developed. The dual beamlet monitor system has two diagnostics in one hexagonal box. One diagnostic is a "fast beamlet monitor" for measuring the time evolution of beamlet current profiles with the time resolution of up to 25 MHz. The other diagnostic is a "pepper-pot-type phase space analyzer," which is applied for the evaluation of a phase space structure of the negative ion beamlet. The dual beamlet monitor system is applied to the measurement of the beamlet in the Neutral Beam Test Stand at National Institute for Fusion Science (NIFS-NBTS), in which the beam accelerator is almost identical to those of working beam injectors in the large helical device. It is demonstrated that the overlapping components from the neighboring beamlet can be eliminated, and the phase space structure can be obtained for the single beamlet.

Established gastric cancer cell lines transplantable into C57BL/6 mice show fibroblast growth factor receptor 4 promotion of tumor growth

Previously no mouse gastric cancer cell lines have been available for transplantation into C57BL/6 mice. However, a gastric cancer model in immunocompetent mice would be useful for analyzing putative therapies. N-Methyl-N-nitrosourea (MNU) was given in drinking water to C57BL/6 mice and p53 heterozygous knockout mice. Only 1 tumor from a p53 knockout mouse could be cultured and the cells s.c. transplanted into a C57BL/6 mouse. We cultured this s.c. tumor, and subcloned it. mRNA expression in the most aggressive YTN16 subline was compared to the less aggressive YTN2 subline by microarray analysis, and fibroblast growth factor receptor 4 (FGFR4) in YTN16 cells was knocked out with a CRISPR/Cas9 system and inhibited by an FGFR4 selective inhibitor, BLU9931. These transplanted cell lines formed s.c. tumors in C57BL/6 mice. Four cell lines (YTN2, YTN3, YTN5, YTN16) were subcloned and established. Their in vitro growth rates were similar. However, s.c. tumor establishment rates, metastatic rates, and peritoneal dissemination rates of YTN2 and YTN3 were lower than for YTN5 and YTN16. YTN16 established 8/8 s.c. tumors, 7/8 with lung metastases, 3/8 with lymph node metastases and 5/5 with peritoneal dissemination. FGFR4 expression by YTN16 was 121-fold higher than YTN2. FGFR4-deleted YTN16 cells failed to form s.c. tumors and showed lower rates of peritoneal dissemination. BLU9931 significantly inhibited the growth of peritoneal dissemination of YTN16. These studies present the first transplantable mouse gastric cancer lines. Our results further indicate that FGFR4 is an important growth signal receptor in gastric cancer cells with high FGFR4 expression.

Dendritic cell vaccine induces antigen-specific CD8+ T cells that are metabolically distinct from those of peptide vaccine and is well-combined with PD-1 checkpoint blockade

The success of immune checkpoint blockade has unequivocally demonstrated that anti-tumor immunity plays a pivotal role in cancer therapy. Because endogenous tumor-specific T-cell responsiveness is essential for the success of checkpoint blockade, combination therapy with cancer vaccination may facilitate tumor rejection. To select the best vaccine strategy to combine with checkpoint blockade, we compared dendritic cell-based vaccines (DC-V) with peptide vaccines for induction of anti-tumor immunity that could overcome tumor-induced immunosuppression. Using B16 melanoma and B16-specific TCR-transgenic T-cells (pmel-1), we found that DC-V efficiently primed and expanded pmel-1 cells with an active effector and central memory phenotype that were not exhausted. Vaccine-primed cells were metabolically distinct from naïve cells. DC-V-primed pmel-1 cells contained the population that shifted metabolic pathways away from glycolysis to mitochondrial oxidative phosphorylation. They displayed better effector function and proliferated more than those induced by peptide vaccination. DC-V inhibited tumor growth in prophylactic and therapeutic settings. Only DC-V but not peptide vaccine showed augmented anti-tumor activity when combined with anti-PD-1 therapy. Thus, DC-V combined with PD-1 checkpoint blockade mediates optimal anti-cancer activity in this model.

Abstract 4571: Advantage of dendritic cells for the therapeutic cancer vaccine

Background: To develop effective cancer vaccine, we examined CTLs induced by peptide vaccination (CTLpep) and DC vaccination (CTLDC) in terms of their antitumor effects.

Methods: For preparation of peptide vaccine, 50 µg hgp100 peptide (KVPRNQDWL) and 20 µg CpG were emulsified with 50 µl CFA or IFA. Bone marrow-derived DCs were matured with LPS and pulsed with hgp100 peptide at 1 µg/ml and used as DC vaccine. To induce CTLpep and CTLDC, C57BL/6 mice were first injected with 1 x 107 naive spleen cells from Pmel-1 TCR transgenic mice to increase hgp100-specific CTL precursors. Then mice were vaccinated twice with 2 weeks interval. The induction of CTLs were evaluated 2 weeks after the second vaccination. To evaluate their antitumor activity, 1 x 106 B16F10 were inoculated into vaccinated mice (prophylactic model). For therapeutic model, 1 x 106 B16F10 were inoculated into mice on day 0. Five days later 1 x 107 Pmel-1 splenocytes were transferred. Then, mice were vaccinated on days 5 and 12, followed by the measurement of tumor growth.

Results: DC vaccine induced 5-times more CTLs than peptide vaccine. The numbers of CTLpep and CTLDC obtained in the spleen were 2.4±0.2x105 and 1.2±0.4x106, respectively. CTLpep expressed PD-1 and Tim-3 at higher level than CTLDC. Most of CTLpep showed effector memory phenotype (CD44hiCD62L-), while CTLDC contained a considerable fraction of central memory cells (CD44hiCD62L+). Although both CTLpep and CTLDC produce IFN-γ and TNF-α at similar level, more CD107a were detected on CTLDC than CTLpep upon re-stimulation. CTLDC displayed better proliferation potential than CTLpep. These phenotypic differences were confirmed by the comprehensive gene expression analysis. Transcriptome analysis revealed that considerable portion of CTLpep and CTLDC were comparable and different from that of naïve CTLs. However, several genes were expressed differentially. CTLpep expressed higher amount of inhibitory receptors, such as Pdcd1, Lag3, Ctla4 and Tigit than CTLDC. CTLDC expressed Fbp1, which inhibits glycolysis, and Cpt1a, which is the rate-limiting enzyme of mitochondrial fatty acid oxidation, suggesting that their metabolic statuses were shifted from glycolysis to fatty acid oxidation. DC vaccine completely inhibited the tumor growth in prophylactic vaccine setting, while peptide vaccine delayed tumor growth compared to control mice. In therapeutic protocol, peptide vaccine showed no antitumor effect, while DC vaccine significantly suppressed tumor growth. The numbers of intratumoral CTLpep and CTLDC on day 19 were 5.2±2.8 x 104/g and 5.0±1.4 x 105/g, respectively. Intratumoral CTLDC expressed lower levels of PD-1, Tim-3 and LAG-3 and more Ki67 than CTLpep. Furthermore, Intratumoral CTLDC produce more IFN-γ and TNF-α than CTLpep.

Conclusion: DC vaccine induced intratumoral CTLs with multi-functionality and high proliferation potential. Therefore, DC vaccine is our choice for the therapeutic cancer vaccine.

Citation Format: Koji Nagaoka, Akihiro Hosoi, Tamaki Iino, Hirokazu Matsushita, Kazuhiro Kakimi. Advantage of dendritic cells for the therapeutic cancer vaccine [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 4571. doi:10.1158/1538-7445.AM2017-4571