To prepare Translational relevanceAdoptive T cell therapy with neoantigen-specific T cell receptor (TCR)-engineered T cells is considered as a promising novel immunotherapy strategy. It takes four steps to prepare; (1) prediction of neoantigen epitopes, (2) neoantigen peptides synthesis, (3) identification of neoantigen-specific TCR and (4) production of virus vector to express TCR. Among them, the most challenging part is identification of neoantigen-specific TCRs. Our protocol required only two weeks from stimulation of T cells with peptides to the identification of neoantigen-specific TCRs. We conducted a pilot study to validate our time-efficient protocol in solid cancers with relatively lower mutational loads such as ovarian cancer. We successfully induced neoantigen-specific T cells against three neoantigens and established corresponding TCR-engineered T cells. One case of neoantigen-specific TCR-engineered T cells showed cross-reactivity against the corresponding wild-type peptide. These results give an important insight into the clinical application of adoptive T cell therapy with neoantigen-specific TCR-engineered T cells.Research. Author manuscripts have been peer reviewed and accepted for publication but have not yet been edited. Author Manuscript Published OnlineFirst on May 2, 2018; DOI: 10.1158/1078-0432.CCR-18-0142 4 ABSTRACTPurpose: Current evolution of cancer immunotherapies, such as immune checkpoint blockade, has implicated neoantigens as major targets of anti-cancer cytotoxic T cells. Adoptive T cell therapy with neoantigen-specific T cell receptor (TCR)-engineered T cells would be an attractive therapeutic option for advanced cancers where the host antitumor immune function is strongly inhibited. We previously developed a rapid and efficient pipeline for production of neoantigen-specific TCR-engineered T cells using peripheral blood from an HLA-matched healthy donor. Our protocol required only two weeks from stimulation of T cells with neoantigen-loaded dendritic cells to the identification of neoantigen-specific TCRs. We conducted the pilot study to validate our protocol. Experimental Design: We used tumors from 7 ovarian cancer patients to validate our protocol.Results: We chose 14 candidate neoantigens from 7 ovarian tumors (1-3 candidates for each patient), and then successfully induced 3 neoantigen-specific T cells from one healthy donor and identified their TCR sequences. Moreover, we validated functional activity of the three identified TCRs by generating TCR-engineered T cells which recognized the corresponding neoantigens and showed cytotoxic activity in an antigendose-dependent manner. However, one case of neoantigen-specific TCR-engineered T cells showed cross-reactivity against the corresponding wild-type peptide. Conclusion/discussions: This pilot study demonstrated the feasibility of our efficient process from identification of neoantigen to production of the neoantigen-targeting cytotoxic TCR-engineered T cells for ovarian cancer and revealed the importance of careful validati...

Neoantigens are the main targets of tumor-specific T cells reactivated by immune checkpoint-blocking antibodies or when using tumor-infiltrating T cells for adoptive therapy. While cancers often accumulate hundreds of mutations and harbor several immunogenic neoantigens, the repertoire of mutation-specific T cells in patients might be restricted. To bypass suboptimal conditions, which impede the reactivation of existing T cells or the priming of neoantigen-specific T cells in a patient, we employ T cells of healthy donors with an overlapping HLA repertoire to target cancer neoantigens. In this study, we focus on streamlining the process of in vitro-induction of neoantigen-specific T cells and isolating their T cell receptors (TCRs) to establish a time-efficient protocol that will allow the patient to benefit from subsequent therapy. We first optimized the priming of T cells to omit multiple restimulations and extended culturing. Neoantigen-specific T cells were enriched using specific dextramers and next-generation sequencing was applied to determine the TCR repertoire. This allowed us to circumvent the laborious process of expanding T cell clones. Using this protocol, we successfully identified HLA-A-restricted TCRs specific for neoantigens found in an esophageal cancer cell line (TE-8) and a primary ovarian cancer. To verify TCR specificity, we generated TCR-engineered T cells and confirmed recognition of the tumor-derived neoantigens. Our results also emphasize the importance of neoepitope selection in order to avoid cross-reactivity to corresponding wild-type peptide sequences. In conclusion, we established a 2-week protocol for generating and identifying neoantigen-specific TCRs from third-party donors making this strategy applicable for clinical use.

To develop a practically applicable method for T-cell receptor (TCR)-engineered T cell immunotherapy targeting neoantigens, we have been attempting to identify neoantigen-specific T cell receptors (TCRs) and establish TCR-engineered T cells in a 3–4-month period. In this study, we report the characterization of T cell repertoires in tumor microenvironment (TME) and identification of neoantigen-specific TCRs after stimulation of patient-derived T cells. We screened 15 potential neoantigen peptides and successfully identified two CD8 + HLA-dextramer + T cells, which recognized MAGOHB G17A and ZCCHC14 P368L . All three dominant TCR clonotypes from MAGOHB G17A -HLA dextramer-sorted CD8 + T cells were also found in T cells in TME, while none of dominant TCR clonotypes from ZCCHC14 P368L -HLA dextramer-sorted CD8 + T cells was found in the corresponding TME. The most dominant TCRA/TCRB pairs for these two neoantigens were cloned into HLA-matched healthy donors’ T lymphocytes to generate TCR-engineered T cells. The functional assay showed MAGOHB G17A TCR-engineered T cells could be significantly activated in a mutation-specific, HLA-restricted and peptide-dose-dependent manner while ZCCHC14 P368L TCR-engineered T cells could not. Our data showed neoantigen-reactive T cell clonotypes that were identified in the patient’s peripheral blood could be present in the corresponding TME and might be good TCRs targeting neoantigens.

Tumor draining lymph nodes (TDLNs) are located in the routes of lymphatic drainage from a primary tumor and have the highest risk of metastasis in various types of solid tumors. TDLNs are also considered as a tissue to activate the antitumor immunity, where antigen-specific effector T cells are generated. However, T cell receptor (TCR) repertoires in TDLNs have not been well characterized. We collected 23 colorectal cancer tumors with 203 lymph nodes with/without metastatic cancer cells (67 were metastasis-positive and the remaining 136 were metastasis-negative) and performed TCR sequencing. Metastasis-positive TDLNs showed a significantly lower TCR diversity and shared TCR clonotypes more frequently with primary tumor tissues compared to metastasis-negative TDLNs. Principal component analysis indicated that TDLNs with metastasis showed similar TCR repertoires. These findings suggest that cancer-reactive T cell clones could be enriched in the metastasis-positive TDLNs. ARTICLE HISTORY

Adoptive cell therapy using TCR-engineered T cells (TCR-T cells) represents a promising strategy for treating relapsed and metastatic cancers. We previously established methods to identify neoantigenspecific TCRs based on patients' PBMCs. However, in clinical practice isolation of PBMCs from advanced-stage cancer patients proves to be difficult. In this study, we substituted blood-derived T cells for tumor-infiltrating lymphocytes (TILs) and used an HLA-matched cell line of antigenpresenting cells (APCs) to replace autologous dendritic cells. Somatic mutations were determined in head and neck squamous cell carcinoma resected from two patients. HLA-A*02:01-restricted neoantigen libraries were constructed and transferred into HLA-matched APCs for stimulation of patient TILs. TCRs were isolated from reactive TIL cultures and functionality was tested using TCR-T cells in vitro and in vivo. To exemplify the screening approach, we identified the targeted neoantigen leading to recognition of the minigene construct that stimulated the strongest TIL response. Neoantigen peptides were used to load MHC-tetramers for T cell isolation and a TCR was identified targeting the KIAA1429 D1358E mutation. TCR-T cells were activated, exhibited cytotoxicity, and secreted cytokines in a dose-dependent manner, and only when stimulated with the mutant peptide. Furthermore, comparable to a neoantigen-specific TCR that was isolated from the patient's PBMCs, KIAA1429 D1358E -specific TCR T cells destroyed human tumors in mice. The established protocol provides the required flexibility to methods striving to identify neoantigen-specific TCRs. By using an MHC-matched APC cell line and neoantigen-encoding minigene libraries, autologous TILs can be stimulated and screened when patient PBMCs and/or tumor material are not available anymore.Abbreviations: Head and neck squamous cell carcinoma (HNSCC); adoptive T cell therapy (ACT); T cell receptor (TCR); tumor-infiltrating lymphocytes (TIL); cytotoxic T lymphocyte (CTL); peripheral blood mononuclear cell (PBMC); dendritic cell (DC); antigen-presenting cells (APC)