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Adoptive cellular therapy (ACT) targeting neoantigens can achieve durable clinical responses in patients with cancer. Most neoantigens arise from patient-specific mutations, requiring highly individualized treatments. To broaden the applicability of ACT targeting neoantigens, we focused on TP53 mutations commonly shared across different cancer types. We performed whole-exome sequencing on 163 patients with metastatic solid cancers, identified 78 who had TP53 missense mutations, and through immunologic screening, identified 21 unique T-cell reactivities. Here, we report a library of 39 T-cell receptors (TCR) targeting TP53 mutations shared among 7.3% of patients with solid tumors. These TCRs recognized tumor cells in a TP53 mutation- and human leucocyte antigen (HLA)-specific manner in vitro and in vivo. Twelve patients with chemorefractory epithelial cancers were treated with ex vivo–expanded autologous tumor-infiltrating lymphocytes (TIL) that were naturally reactive against TP53 mutations. However, limited clinical responses (2 partial responses among 12 patients) were seen. These infusions contained low frequencies of mutant p53–reactive TILs that had exhausted phenotypes and showed poor persistence. We also treated one patient who had chemorefractory breast cancer with ACT comprising autologous peripheral blood lymphocytes transduced with an allogeneic HLA-A*02–restricted TCR specific for p53R175H. The infused cells exhibited an improved immunophenotype and prolonged persistence compared with TIL ACT and the patient experienced an objective tumor regression (-55%) that lasted 6 months. Collectively, these proof-of-concept data suggest that the library of TCRs targeting shared p53 neoantigens should be further evaluated for the treatment of patients with advanced human cancers. See related Spotlight by Klebanoff, p. 919

Adoptive transfer of T cells with engineered T-cell receptor (TCR) genes that target tumor-specific antigens can mediate cancer regression. Accumulating evidence suggests that the clinical success of many immunotherapies is mediated by T cells targeting mutated neoantigens unique to the patient. We hypothesized that the most frequent TCR clonotypes infiltrating the tumor were reactive against tumor antigens. To test this hypothesis, we developed a multistep strategy that involved TCRB deep sequencing of the CD8+PD-1+ T-cell subset, matching of TCRA–TCRB pairs by pairSEQ and single-cell RT-PCR, followed by testing of the TCRs for tumor-antigen specificity. Analysis of 12 fresh metastatic melanomas revealed that in 11 samples, up to 5 tumor-reactive TCRs were present in the 5 most frequently occurring clonotypes, which included reactivity against neoantigens. These data show the feasibility of developing a rapid, personalized TCR-gene therapy approach that targets the unique set of antigens presented by the autologous tumor without the need to identify their immunologic reactivity. Cancer Immunol Res; 4(9); 734–43. ©2016 AACR.

T-cells targeting shared oncogenic mutations can induce durable tumor regression in epithelial cancer patients. These T-cells can be detected in tumor-infiltrating lymphocytes, but whether such cells can be detected in the peripheral blood of patients with common metastatic epithelial cancer is unknown. Using a highly sensitive in vitro stimulation and enrichment of peripheral memory T-cells from six metastatic cancer patients, we identified and isolated memory T-cells targeting the mutated KRASG12D and KRASG12V variants, in three patients. In an additional two metastatic colon cancer patients, we detected CD8+ neoantigen-specific cells targeting the unique mutated SMAD5 and MUC4 proteins. Therefore, memory T-cells targeting KRAS and neoantigens can be detected in the peripheral blood of epithelial cancer patients and can potentially be used for the development of effective personalized T-cell-based cancer immunotherapy across multiple patients. Citation Format: Gal Cafri, Rami Yossef, Anna Pasetto, Drew Deniger, Jared J. Gartner, Todd Prickett, Paul F. Robbins, Steven A. Rosenberg. Memory T-cells targeting unique and shared oncogenic mutations detected in peripheral blood of epithelial cancer patients [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A175.

Adoptive cell transfer (ACT) of selected tumor-infiltrating lymphocytes (TILs) targeting neoantigens can mediate tumor regression in selected patients with metastatic epithelial cancer. However, effectively identifying and harnessing neoantigen-reactive T-cells for patient treatment remains a challenge and it is unknown whether current methods to detect neoantigen-reactive T-cells are missing potentially clinically relevant neoantigen reactivities. We thus investigated whether the detection of tumor-neoantigen reactive TILs in epithelial cancers could be enhanced by enriching T-cells that express PD-1 and/or T-cell activation markers (CD134, CD137) followed by microwell culturing at limiting dilution cell concentrations to avoid overgrowth of non-reactive T-cells. Using this approach, in six patients with metastatic epithelial cancer including stomach, colon pancreatic and ovarian cancers, this method led to the detection of CD4 and CD8 T-cells targeting 19 neoantigens compared to only eight neoantigens recognized using our standard TIL fragment screening approach. In two patients, no recognition of mutated peptides was observed using our conventional screen, while our high-throughput approach led to the identification of five neoantigen reactive-TCRs against five different mutations from one patient and a highly potent MHC-II-restricted KRASG12V reactive TCR from a second patient. In addition, in a metastatic tumor sample from a patient with serous ovarian cancer, we isolated three MHC class-II-restricted TCRs targeting the TP53G245S “hot-spot” mutation. In conclusion, this approach provides a highly sensitive and specific platform to isolate clinically relevant neoantigen-reactive T-cells or their TCRs for cancer treatment. Citation Format: Rami Yossef, Eric Tran, Alena Gros, Drew Deniger, Gal Cafri, Steven A. Rosenberg. Enhanced detection of T-cells targeting unique neoantigens and shared mutated oncogenes for personalized cancer immunotherapy [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr B055.

Functionally pleiotropic human γδ T cells are a unique set of immune cells that exhibit qualities of both innate and adaptive immune responses. In contrast to αβ T cells, γδ T cells recognize their ligands independent of MHC and are infrequent (1%–5% of T cells) in peripheral blood. Studies have shown that γδ T cells exhibit endogenous cytotoxicity towards tumor cells by directly recognizing a diverse array of Tumor Associated Antigen (TAA) and have the ability to present TAA to elicit an antitumor response. This broad recognition of antitumor activity is achieved because these cells express a diverse TCR γδ repertoire (combination of Vδ1, Vδ2, or Vδ3 with one of fourteen Vγ chains). Because of their characteristics γδ T cells are attractive targets for clinical manipulation and tumor immunotherapy. To obtain clinically significant numbers of cells for immunotherapy current ex vivo γδ T cells expansion protocol uses Zoledronic acid, an aminobisphosphonate that results only in selective propagation of Vγ9Vδ2. These cells however, showed clinical response against both solid and hematologic tumors. We have previously shown a novel ex vivo expansion protocol using artificial antigen presenting cells (aAPC), IL2 and IL21 assist aAPC in activating and expanding polyclonal γδ T-cells (Vδ1, Vδ2 and Vδ1neg Vδ2neg T cell subtypes) to clinically significant numbers. These expanded cell subsets secrete proinflammatory cytokines, lysed a broad range of malignancies and improved survival in ovarian cancer xenograft model. To better define the role of the subsets and their application in immunotherapy here we present high-resolution transcriptome, microRNA and secreted cytokine-chemokine signatures of ex vivo expanded subsets. Our data provide an atlas of transcriptional, epigenetic and secretome of three defined subsets, and subset-specific signatures. The data presented here will have a broader impact in understanding the immunobiology of γδ T cell subsets and facilitate improving the human application of these cells in cancer immunotherapy. Citation Format: Sourindra Maiti, Drew Deniger, Jianliang Dai, Laurence Cooper. Transcriptional and epigenetic signatures of ex vivo propagated three distinct TCR Vδ1, TCR Vδ2 and TCR Vδ3 cell subtypes with broad specificity for malignancies. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr B028.