Epigenetic profiles guide improved CRISPR/Cas9-mediated gene knockout in human T cells.

Genetic modification of specific genes is emerging as a useful tool to enhance the functions of antitumor T cells in adoptive immunotherapy. Current advances in CRISPR/Cas9 technology enable gene knockout during in vitro preparation of infused T-cell products through transient transfection of a Cas9-guide RNA (gRNA) ribonucleoprotein complex. However, selecting optimal gRNAs remains a major challenge for efficient gene ablation. Although multiple in silico tools to predict the targeting efficiency have been developed, their performance has not been validated in cultured human T cells. Here, we explored a strategy to select optimal gRNAs using our pooled data on CRISPR/Cas9-mediated gene knockout in human T cells. The currently available prediction tools alone were insufficient to accurately predict the indel percentage in T cells. We used data on the epigenetic profiles of cultured T cells obtained from transposase-accessible chromatin with high-throughput sequencing (ATAC-seq). Combining the epigenetic information with sequence-based prediction tools significantly improved the gene-editing efficiency. We further demonstrate that epigenetically closed regions can be targeted by designing two gRNAs in adjacent regions. Finally, we demonstrate that the gene-editing efficiency of unstimulated T cells can be enhanced through pretreatment with IL-7. These findings enable more efficient gene editing in human T cells.

High CD62L expression predicts the generation of chimeric antigen receptor T cells with potent effector functions.

The efficient generation of chimeric antigen receptor (CAR) T cells is highly influenced by the quality of apheresed T cells. Healthy donor-derived T cells usually proliferate better than patients-derived T cells and are precious resources to generate off-the-shelf CAR-T cells. However, relatively little is known about the determinants that affect the efficient generation of CAR-T cells from healthy donor-derived peripheral blood mononuclear cells (PBMCs) compared with those from the patients' own PBMCs. We here examined the efficiency of CAR-T cell generation from multiple healthy donor samples and analyzed its association with the phenotypic features of the starting peripheral blood T cells. We found that CD62L expression levels within CD8+ T cells were significantly correlated with CAR-T cell expansion. Moreover, high CD62L expression within naïve T cells was associated with the efficient expansion of T cells with a stem cell-like memory phenotype, an indicator of high-quality infusion products. Intriguingly, genetic disruption of CD62L significantly impaired CAR-T cell proliferation and cytokine production upon antigen stimulation. Conversely, ectopic expression of a shedding-resistant CD62L mutant augmented CAR-T cell effector functions compared to unmodified CAR-T cells, resulting in improved antitumor activity in vivo. Collectively, we identified the surface expression of CD62L as a concise indicator of potent T-cell proliferation. CD62L expression is also associated with the functional properties of CAR-T cells. These findings are potentially applicable to selecting optimal donors to massively generate CAR-T cell products.

Genetic ablation of PRDM1 in antitumor T cells enhances therapeutic efficacy of adoptive immunotherapy.

Adoptive cancer immunotherapy can induce objective clinical efficacy in patients with advanced cancer; however, a sustained response is achieved in a minority of cases. The persistence of infused T cells is an essential determinant of a durable therapeutic response. Antitumor T cells undergo a genome-wide remodeling of the epigenetic architecture upon repeated antigen encounters, which inevitably induces progressive T-cell differentiation and the loss of longevity. In this study, we identified PR domain zinc finger protein 1 (PRDM1) ie, Blimp-1, as a key epigenetic gene associated with terminal T-cell differentiation. The genetic knockout of PRDM1 by clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) supported the maintenance of an early memory phenotype and polyfunctional cytokine secretion in repeatedly stimulated chimeric antigen receptor (CAR)-engineered T cells. PRDM1 disruption promoted the expansion of less differentiated memory CAR-T cells in vivo, which enhanced T-cell persistence and improved therapeutic efficacy in multiple tumor models. Mechanistically, PRDM1-ablated T cells displayed enhanced chromatin accessibility of the genes that regulate memory formation, thereby leading to the acquisition of gene expression profiles representative of early memory T cells. PRDM1 knockout also facilitated maintaining an early memory phenotype and cytokine polyfunctionality in T-cell receptor-engineered T cells as well as tumor-infiltrating lymphocytes. In other words, targeting PRDM1 enabled the generation of superior antitumor T cells, which is potentially applicable to a wide range of adoptive cancer immunotherapies.

Selection of highly responsive T cell receptors by an analysis combining the expression of multiple markers.

The clinical success of T cell receptor (TCR) gene-transduced T (TCR-T) cell therapy is expected as one of the next-generation immunotherapies for cancer, in which the selection of TCRs with high functional avidity (high-functional TCRs) is important. One widely used approach to select high-functional TCRs is a comparison of the EC50 values of TCRs, which involves laborious experiments. Therefore, the establishment of a simpler method to select high-functional TCRs is desired. We herein attempted to establish a simple method to select high-functional TCRs based on the expression of T cell activation markers using the mouse T cell line BW5147.3 (BW). We examined relationships between the EC50 values of TCRs in interleukin-2 production and the expression levels of TCR activation markers on BW cells. In TCR-expressing BW cells stimulated with antigenic peptides, the CD69, CD137, and PD-1 expression was differentially induced by various doses of peptides. An analysis of TCRs derived from the tumor-infiltrating lymphocytes of murine melanoma and peripheral blood T cells of hepatocellular carcinoma patients treated with a peptide vaccination revealed that an analysis combining CD69, CD137, and PD-1 expression levels in BW cells stimulated with a single dose of an antigenic peptide selected high-functional TCRs with functional avidity assessed by EC50 values. Our method facilitates the section of high-functional TCRs among tumor-reacting TCRs, which will promote TCR-T cell therapy. The stimulation of BW cells expressing objective TCRs with a single dose of antigenic peptides and analysis combining the expression of CD69, CD137, and PD-1 allows us to select highly responsive TCRs.

Tumor-Infiltrating T Cells Concurrently Overexpress CD200R with Immune Checkpoints PD-1, CTLA-4, and TIM-3 in Non-Small-Cell Lung Cancer.

INTRODUCTION: CD200R has been reported to be the receptor for the immune checkpoint molecule CD200 and can transduce immune-suppressive signals. In this study, we mainly focused on the expression level of CD200R in T cells in pulmonary artery (PA) blood and non-small-cell lung cancer (NSCLC) tumor tissue. METHODS: Immune cells were isolated from dissected tumor samples and PA blood of NSCLC patients and analyzed with multiparameter flow cytometry. The co-expression of CD200R with other immune checkpoints, including programmed cell death protein 1 (PD-1), cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), and T cell immunoglobulin and mucin domain-containing protein 3 (TIM-3), was also investigated. RESULTS: CD200R expression was observed on the surface of approximately 75% of T cells among tumor-infiltrating leukocytes (TILs). Compared to T cells extracted from TILs, only 55% of T cells extracted from PA blood exhibited CD200R expression. Moreover, with higher expression of CD200R, the expression of other immune checkpoints, including PD-1, CTLA-4, and TIM-3, was also increased in tumor-infiltrating T cells compared to T cells in PA blood. CONCLUSIONS: Our results showed that those tumors were dominated by T cells expressing CD200R together with other checkpoints, which suggests a phenotypic change after T cell infiltration into the tumor, such as T cell exhaustion.

Peptide vaccine as an adjuvant therapy for glypican-3-positive hepatocellular carcinoma induces peptide-specific CTLs and improves long prognosis.

There is no established postoperative adjuvant therapy for hepatocellular carcinoma (HCC), and improvement of patient prognosis has been limited. We conducted long-term monitoring of patients within a phase II trial that targeted a cancer antigen, glypican-3 (GPC3), specifically expressed in HCC. We sought to determine if the GPC3 peptide vaccine was an effective adjuvant therapy by monitoring disease-free survival and overall survival. We also tracked GPC3 immunohistochemical (IHC) staining, CTL induction, and postoperative plasma GPC3 for a patient group that was administered the vaccine (n = 35) and an unvaccinated patient group that underwent surgery only (n = 33). The 1-y recurrence rate after surgery was reduced by approximately 15%, and the 5-y and 8-y survival rates were improved by approximately 10% and 30%, respectively, in the vaccinated group compared with the unvaccinated group. Patients who were positive for GPC3 IHC staining were more likely to have induced CTLs, and 60% survived beyond 5 y. Vaccine efficacy had a positive relationship with plasma concentration of GPC3; high concentrations increased the 5-y survival rate to 75%. We thus expect GPC3 vaccination in patients with HCC, who are positive for GPC3 IHC staining and/or plasma GPC3 to induce CTL and have significantly improved long-term prognosis.

Efficacy of immunotherapy targeting the neoantigen derived from epidermal growth factor receptor T790M/C797S mutation in non-small cell lung cancer.

Lung cancer is the leading cause of cancer-related deaths worldwide. Epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKI) often have good clinical activity against non-small cell lung cancer (NSCLC) with activating EGFR mutations. Osimertinib, which is a third-generation EGFR-TKI, has a clinical effect even on NSCLC harboring the threonine to methionine change at codon 790 of EGFR (EGFR T790M) mutation that causes TKI resistance. However, most NSCLC patients develop acquired resistance to osimertinib within approximately 1 year, and 40% of these patients have the EGFR T790M and cysteine to serine change at codon 797 (C797S) mutations. Therefore, there is an urgent need for the development of novel treatment strategies for NSCLC patients with the EGFR T790M/C797S mutation. In this study, we identified the EGFR T790M/C797S mutation-derived peptide (790-799) (MQLMPFGSLL) that binds the human leukocyte antigen (HLA)-A*02:01, and successfully established EGFR T790M/C797S-peptide-specific CTL clones from human PBMC of HLA-A2 healthy donors. One established CTL clone demonstrated adequate cytotoxicity against T2 cells pulsed with the EGFR T790M/C797S peptide. This CTL clone also had high reactivity against cancer cells that expressed an endogenous EGFR T790M/C797S peptide using an interferon-γ (IFN-γ) enzyme-linked immunospot (ELISPOT) assay. In addition, we demonstrated using a mouse model that EGFR T790M/C797S peptide-specific CTL were induced by EGFR T790M/C797S peptide vaccine in vivo. These findings suggest that an immunotherapy targeting a neoantigen derived from EGFR T790M/C797S mutation could be a useful novel therapeutic strategy for NSCLC patients with EGFR-TKI resistance, especially those resistant to osimertinib.

Higher human lymphocyte antigen class I expression in early-stage cancer cells leads to high sensitivity for cytotoxic T lymphocytes.

Human lymphocyte antigen (HLA) class I molecules play a central role in cytotoxic T lymphocytes (CTL)-based antitumor immunity. However, the expression rate of HLA class I in cancer cells remains a topic of discussion. We compared HLA class I expression levels between cancer cells and surrounding non-tumorous hepatocytes in 20 early-stage hepatocellular carcinoma (HCC) patients by immunohistochemistry using EMR 8-5. The expression levels of HLA class I were classified as negative, incomplete positive or complete positive. Similarly, for various types of solid cancers, HLA class I expression was examined. For the HLA class I expression in cancer cells, among 20 HCC patients, 13 were complete positive, 3 were incomplete positive, and 4 were negative. In addition, 15 (75.0%) had higher expression levels of HLA class I in cancer cells compared with that in surrounding non-tumorous hepatocytes. An interferon-γ (IFN-γ) enzyme-linked immunospot (ELISPOT) assay indicated that cancer cells with positive expression of HLA class I had strong sensitivity to antigen-specific CTL. We suggested that HLA class I expression in cancer cells could be involved in the clinical prognosis of HCC patients. Similarly, 66.7%, 100.0%, 66.7% and 62.5% of patients with early-stage pancreatic, gallbladder, esophageal and breast cancers, respectively, had higher expression levels of HLA class I in cancer cells than in surrounding normal tissue cells. We suggest that in several early-stage solid cancers, including HCC, HLA class I expression levels in cancer cells are higher than that in surrounding normal tissue cells, which could result in the anti-tumor effect of CTL-based cancer immunotherapy.

Heat shock protein 105 peptide vaccine could induce antitumor immune reactions in a phase I clinical trial.

Heat shock protein 105 (HSP105) is overexpressed in many cancers, including colorectal cancer (CRC) and esophageal cancer (EC). We carried out a phase I clinical trial of HLA-A24- and HLA-A2-restricted HSP105 peptide vaccines in patients with CRC or EC. In this additional study of the trial, we examined the immunological efficacy of the novel vaccine. Thirty patients with advanced CRC or EC underwent HSP105 peptide vaccination. Immunological responses were evaluated by ex vivo and in vitro γ-interferon enzyme-linked immunospot assays and their correlation with patients' prognosis was analyzed. The HSP105 peptide vaccines induced peptide-specific CTLs in 15 of 30 patients. Among HLA-A24 patients (n = 15), 7 showed induction of CTLs only ex vivo, whereas among HLA-A2 patients (n = 15), 4 showed the induction ex vivo and 6 in vitro. Heat shock protein 105-specific CTL induction correlated with suppression of cancer progression and was revealed as a potential predictive biomarker for progression-free survival (P = .008; hazard ratio = 3.03; 95% confidence interval, 1.34-6.85) and overall survival (P = .025; hazard ratio = 2.72; 95% confidence interval, 1.13-6.52). Production of cytokines by HSP105 peptide-specific CTLs was observed at the injection sites (skin) and tumor tissues, suggesting that HSP105-specific CTLs not only accumulated at vaccination sites but also infiltrated tumors. Furthermore, we established 2 HSP105 peptide-specific CTL clones, which showed HSP105-specific cytokine secretion and cytotoxicity. Our results suggest that the HSP105 peptide vaccine could induce immunological effects in cancer patients and improve their prognosis.

Efficacy of the NCCV Cocktail-1 vaccine for refractory pediatric solid tumors: A phase I clinical trial.

Pediatric refractory solid tumors are aggressive malignant diseases, resulting in an extremely poor prognosis. KOC1, FOXM1, and KIF20A are cancer antigens that could be ideal targets for anticancer immunotherapy against pediatric refractory solid tumors with positive expression for these antigens. This nonrandomized, open-label, phase I clinical trial evaluated the safety and efficacy of the NCCV Cocktail-1 vaccine, which is a cocktail of cancer peptides derived from KOC1, FOXM1, and KIF20A, in patients with pediatric refractory solid tumors. Twelve patients with refractory pediatric solid tumors underwent NCCV Cocktail-1 vaccination weekly by intradermal injections. The primary endpoint was the safety of the NCCV Cocktail-1 vaccination, and the secondary endpoints were the immune response, as measured by interferon-r enzyme-linked immunospot assay, and the clinical outcomes including tumor response and progression-free survival. The NCCV Cocktail-1 vaccine was well tolerated. The clinical response of this trial showed that 4 patients had stable disease after 8 weeks and 2 patients maintained remission for >11 months. In 4, 8, and 5 patients, the NCCV Cocktail-1 vaccine induced the sufficient number of peptide-specific CTLs for KOC1, FOXM1, and KIF20A, respectively. Patients with high peptide-specific CTL frequencies for KOC1, FOXM1, and KIF20A had better progression-free survival than those with low frequencies. The findings of this clinical trial showed that the NCCV Cocktail-1 vaccine could be a novel therapeutic strategy, with adequate effects against pediatric refractory solid tumors. Future large-scale trials should evaluate the efficacy of the NCCV Cocktail-1 vaccination.

Cancer immunotherapy-targeted glypican-3 or neoantigens.

Immune checkpoint inhibitors have ushered in a new era in cancer therapy, although other therapies or combinations thereof are still needed for many patients for whom these drugs are ineffective. In this light, we have identified glypican-3 an HLA-24, HLA-A2 restriction peptide with extreme cancer specificity. In this paper, we summarize results from a number of related clinical trials showing that glypican-3 peptide vaccines induce specific CTLs in most patients (UMIN Clinical Trials Registry: UMIN000001395, UMIN000005093, UMIN000002614, UMN000003696, and UMIN000006357). We also describe the current state of personalized cancer immunotherapy based on neoantigens, and assess, based on our own research and experience, the potential of such therapy to elicit cancer regression. Finally, we discuss the future direction of cancer immunotherapy.

Vaccination with liposome-coupled glypican-3-derived epitope peptide stimulates cytotoxic T lymphocytes and inhibits GPC3-expressing tumor growth in mice.

Because therapeutic manipulation of immunity can induce tumor regression, anti-cancer immunotherapy is considered a promising treatment modality. We previously reported that glypican-3 (GPC3), an oncofetal antigen overexpressed in hepatocellular carcinoma (HCC), is a useful target for cytotoxic T lymphocyte (CTL)-mediated cancer immunotherapy, and we have performed clinical trials using the GPC3-derived peptide vaccine. Although vaccine-induced GPC3-peptide-specific CTLs were often tumor reactive in vitro and were correlated with overall survival, no complete response was observed. In the current study, we synthesized liposome-coupled GPC3-derived CTL epitope peptide (pGPC3-lipsome) and investigated its antitumor potential. Vaccination with pGPC3-liposome induced peptide-specific CTLs at a lower dose than conventional vaccine emulsified in incomplete Freund's adjuvant. Coupling of pGPC3 to liposomes was essential for effective priming of GPC3-specific CTLs. In addition, immunization with pGPC3-liposome inhibited GPC3-expressing tumor growth. Thus, vaccination with tumor-associated antigen-derived epitope peptides coupled to the surfaces of liposomes may be a novel therapeutic strategy for cancer.

Protocol to measure human IL-6 secretion from CAR T cell-primed macrophage and monocyte lineage cells in vitro and in vivo using humanized mice.

Chimeric antigen receptor (CAR) T cell therapy often causes serious toxicities, such as cytokine release syndrome (CRS), mainly due to interleukin-6 (IL-6) secreted by monocyte lineage cells. Here, we describe a protocol to generate anti-CD19 CAR T cells and quantify human monocyte-derived IL-6 cocultured with CAR T cells and target tumor cells in vitro. We further describe a protocol to generate a humanized mouse model and evaluate CAR T cell-associated plasma IL-6 levels in vivo. For complete details on the use and execution of this protocol, please refer to Yoshikawa et al.1.

Development of a chimeric cytokine receptor that captures IL-6 and enhances the antitumor response of CAR-T cells.

The efficacy of chimeric antigen receptor (CAR)-engineered T cell therapy is suboptimal in most cancers, necessitating further improvement in their therapeutic actions. However, enhancing antitumor T cell response inevitably confers an increased risk of cytokine release syndrome associated with monocyte-derived interleukin-6 (IL-6). Thus, an approach to simultaneously enhance therapeutic efficacy and safety is warranted. Here, we develop a chimeric cytokine receptor composed of the extracellular domains of GP130 and IL6RA linked to the transmembrane and cytoplasmic domain of IL-7R mutant that constitutively activates the JAK-STAT pathway (G6/7R or G6/7R-M452L). CAR-T cells with G6/7R efficiently absorb and degrade monocyte-derived IL-6 in vitro. The G6/7R-expressing CAR-T cells show superior expansion and persistence in vivo, resulting in durable antitumor response in both liquid and solid tumor mouse models. Our strategy can be widely applicable to CAR-T cell therapy to enhance its efficacy and safety, irrespective of the target antigen.

Intratumoral peptide injection enhances tumor cell antigenicity recognized by cytotoxic T lymphocytes: a potential option for improvement in antigen-specific cancer immunotherapy.

Antigen-specific cancer immunotherapy is a promising strategy for improving cancer treatment. Recently, many tumor-associated antigens and their epitopes recognized by cytotoxic T lymphocytes (CTLs) have been identified. However, the density of endogenously presented antigen-derived peptides on tumor cells is generally sparse, resulting in the inability of antigen-specific CTLs to work effectively. We hypothesize that increasing the density of an antigen-derived peptide would enhance antigen-specific cancer immunotherapy. Here, we demonstrated that intratumoral peptide injection leads to additional peptide loading onto major histocompatibility complex class I molecules of tumor cells, enhancing tumor cell recognition by antigen-specific CTLs. In in vitro studies, human leukocyte antigen (HLA)-A*02:01-restricted glypican-3144-152 (FVGEFFTDV) and cytomegalovirus495-503 (NLVPMVATV) peptide-specific CTLs showed strong activity against all peptide-pulsed cell lines, regardless of whether the tumor cells expressed the antigen. In in vivo studies using immunodeficient mice, glypican-3144-152 and cytomegalovirus495-503 peptides injected into a solid mass were loaded onto HLA class I molecules of tumor cells. In a peptide vaccine model and an adoptive cell transfer model using C57BL/6 mice, intratumoral injection of ovalbumin257-264 peptide (SIINFEKL) was effective for tumor growth inhibition and survival against ovalbumin-negative tumors without adverse reactions. Moreover, we demonstrated an antigen-spreading effect that occurred after intratumoral peptide injection. Intratumoral peptide injection enhances tumor cell antigenicity and may be a useful option for improvement in antigen-specific cancer immunotherapy against solid tumors.

CD83 expression characterizes precursor exhausted T cell population.

T cell exhaustion is a main obstacle against effective cancer immunotherapy. Exhausted T cells include a subpopulation that maintains proliferative capacity, referred to as precursor exhausted T cells (TPEX). While functionally distinct and important for antitumor immunity, TPEX possess some overlapping phenotypic features with the other T-cell subsets within the heterogeneous tumor-infiltrating T-lymphocytes (TIL). Here we explore surface marker profiles unique to TPEX using the tumor models treated by chimeric antigen receptor (CAR)-engineered T cells. We find that CD83 is predominantly expressed in the CCR7+PD1+ intratumoral CAR-T cells compared with the CCR7-PD1+ (terminally differentiated) and CAR-negative (bystander) T cells. The CD83+CCR7+ CAR-T cells exhibit superior antigen-induced proliferation and IL-2 production compared with the CD83- T cells. Moreover, we confirm selective expression of CD83 in the CCR7+PD1+ T-cell population in primary TIL samples. Our findings identify CD83 as a marker to discriminate TPEX from terminally exhausted and bystander TIL.

Glypican-3 could be an effective target for immunotherapy combined with chemotherapy against ovarian clear cell carcinoma.

Glypican-3 (GPC3) is useful not only as a novel tumor marker, but also as an oncofetal antigen for immunotherapy. We recently established HLA-A2-restricted GPC3(144-152) peptide-specific CTL clones from hepatocellular carcinoma patients after GPC3(144-152) peptide vaccination. The present study was designed to evaluate the tumor reactivity of a HLA-A2-restricted GPC3(144-152) peptide-specific CTL clone against ovarian clear cell carcinoma (CCC) cell lines. The GPC3(144-152) peptide-specific CTL clone could recognize HLA-A2-positive and GPC3-positive ovarian CCC cell lines on interferon (IFN)-γ enzyme-linked immunospot assay and showed cytotoxicity against KOC-7c cells. The CTL clone recognized naturally processed GPC3-derived peptide on ovarian CCC cells in a HLA class I-restricted manner. Moreover, we confirmed that the level of GPC3 expression was responsible for CTL recognition and that subtoxic-dose chemotherapy made tumor cells more susceptible to the cytotoxic effect of CTL. Thus, it might be possible to treat ovarian CCC patients by combining chemotherapy with immunotherapy. Our data suggest that GPC3 could be an effective target for immunotherapy against ovarian CCC.

HLA-A2-restricted glypican-3 peptide-specific CTL clones induced by peptide vaccine show high avidity and antigen-specific killing activity against tumor cells.

Glypican-3 (GPC3) is an onco-fetal antigen that is overexpressed in human hepatocellular carcinoma (HCC), and is only expressed in the placenta and embryonic liver among normal tissues. Previously, we identified an HLA-A2-restricted GPC3(144-152) (FVGEFFTDV) peptide that can induce GPC3-reactive CTLs without inducing autoimmunity in HLA-A2 transgenic mice. In this study, we carried out a phase I clinical trial of HLA-A2-restricted GPC3(144-152) peptide vaccine in 14 patients with advanced HCC. Immunological responses were analyzed by ex vivo γ-interferon enzyme-linked immunospot assay. The frequency of GPC3(144-152) peptide-specific CTLs after vaccination (mean, 96; range, 5-441) was significantly larger than that before vaccination (mean, 6.5; range, 0-43) (P < 0.01). An increase in the GPC3(144-152) peptide-specific CTL frequency was observed in 12 (86%) of 14 patients after vaccination. Additionally, there was a significant correlation between the maximum value of GPC3(144-152) peptide-specific CTLs after vaccination and the dose of the peptide injected (P = 0.0166, r = 0.665). Moreover, we established several GPC3(144-152) peptide-specific CTL clones from PBMCs of patients vaccinated with GPC3(144-152) peptide by single cell sorting using Dextramer and CD107a antibody. These CTL clones had high avidity (the recognition efficiency showing 50% cytotoxicity was 10(-10) or 10(-11) M) and could recognize HCC cell lines expressing GPC3 in an HLA-class I-restricted manner. These results suggest that GPC3(144-152) peptide vaccine can induce high avidity CTLs capable of killing HCC cells expressing GPC3. This trial was registered with University Hospital Medical Information Network number 000001395.

Heat Shock Protein 105 as an Immunotherapeutic Target for Patients With Cervical Cancer.

BACKGROUND/AIM: Heat shock protein 105 (HSP105) is overexpressed in various cancers, but not in normal tissues. We investigated the expression levels of HSP105 in cervical cancer and the efficacy of immunotherapy targeting HSP105. MATERIALS AND METHODS: Previously, we established human leukocyte antigen-A*02:01 (HLA-A2) restricted HSP105 peptide-specific cytotoxic T lymphocyte (CTL) clones from a colorectal cancer patient vaccinated with an HSP105 peptide. Herein, we evaluated the expression of HSP105 in cervical cancer and cervical intraepithelial neoplasia. Moreover, we tested the effectiveness of an HLA-A2-restricted HSP105 peptide-specific CTL clone against cervical cancer cell lines. RESULTS: HSP105 was expressed in 95% (19/20) of examined cervical cancer tissues. Moreover, the HSP105 peptide-specific CTL clone recognized HSP105- and HLA-A*02:01-positive cervical cancer cell lines and also showed that cytotoxicity against the cervical cancer cell lines depends on HSP105 peptide and HLA class I restricted manners. CONCLUSION: HSP105 could be an effective target for immunotherapy in patients with cervical cancer.

Aberrant splicing isoforms detected by full-length transcriptome sequencing as transcripts of potential neoantigens in non-small cell lung cancer.

BACKGROUND: Long-read sequencing of full-length cDNAs enables the detection of structures of aberrant splicing isoforms in cancer cells. These isoforms are occasionally translated, presented by HLA molecules, and recognized as neoantigens. This study used a long-read sequencer (MinION) to construct a comprehensive catalog of aberrant splicing isoforms in non-small-cell lung cancers, by which novel isoforms and potential neoantigens are identified. RESULTS: Full-length cDNA sequencing is performed using 22 cell lines, and a total of 2021 novel splicing isoforms are identified. The protein expression of some of these isoforms is then validated by proteome analysis. Ablations of a nonsense-mediated mRNA decay (NMD) factor, UPF1, and a splicing factor, SF3B1, are found to increase the proportion of aberrant transcripts. NetMHC evaluation of the binding affinities to each type of HLA molecule reveals that some of the isoforms potentially generate neoantigen candidates. We also identify aberrant splicing isoforms in seven non-small-cell lung cancer specimens. An enzyme-linked immune absorbent spot assay indicates that approximately half the peptide candidates have the potential to activate T cell responses through their interaction with HLA molecules. Finally, we estimate the number of isoforms in The Cancer Genome Atlas (TCGA) datasets by referring to the constructed catalog and found that disruption of NMD factors is significantly correlated with the number of splicing isoforms found in the TCGA-Lung Adenocarcinoma data collection. CONCLUSIONS: Our results indicate that long-read sequencing of full-length cDNAs is essential for the precise identification of aberrant transcript structures in cancer cells.