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T cells targeting shared oncogenic mutations can induce durable tumor regression in epithelial cancer patients. Such T cells can be detected in tumor infiltrating lymphocytes, but whether such cells can be detected in the peripheral blood of patients with the common metastatic epithelial cancer patients is unknown. Using a highly sensitive in vitro stimulation and cell enrichment of peripheral memory T cells from six metastatic cancer patients, we identified and isolated CD4 + , and CD8 + memory T cells targeting the mutated KRAS G12D and KRAS G12V variants, respectively, in three patients. In an additional two metastatic colon cancer patients, we detected CD8 + neoantigen-specific cells targeting the mutated SMAD5 and MUC4 proteins. Therefore, memory T cells targeting unique as well as shared somatic mutations 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. Adoptive cell therapy (ACT) using neoantigen-specific T cells can lead to tumor regression. Here the authors use an in vitro stimulation approach to isolate tumor specific memory T cells from peripheral blood of metastatic epithelial cancer patients targeting unique as well as shared mutations in the KRAS oncogene.

Gastric gastrointestinal stromal tumors (GIST) are rare, neuroectodermal tumors primarily residing in the stomach with characteristic genetic mutations. They are often identified using ultrasound and cross-sectional imaging, or they are noted during endoscopy. Localized gastric GISTs are commonly treated with surgical resection, with the possible use of neoadjuvant or adjuvant medical therapies as they are considered to have malignant potential. The use of tyrosine kinase inhibitors (TKI) such as imatinib has been shown to successfully reduce pre-operative tumor burden, recurrence, and disease progression. Surgical resection considerations vary depending on tumor size, location, and malignant potential. Neoadjuvant and adjuvant TKI therapy dosing varies in response to the type of GIST mutation present and greatly influences prognosis. Novel cooperative minimally invasive surgical techniques and targeted therapies are currently in development to address challenges in GIST treatment for tumors in challenging locations or with significant potential for progression. The management of localized gastric GISTs continues to rapidly evolve; each case should be managed individually, where care is taken in considering details, including tumor location, tumor size, and the molecular genetic profile, before embarking on a course of treatment.

The TP53 gene, encoding the critical p53 tumor suppressor, is the most commonly mutated gene in cancer. Intratumoral T cell responses to mutations occurring frequently at certain TP53 positions, termed hot spots, have not been systematically studied. The 8 most commonly mutated positions in TP53 were found in 33 (24%) of 140 common epithelial tumors analyzed. A TP53-specific screening assay was developed to evaluate T cell responses to these p53 neoepitopes presented though intracellular (tandem minigene) and extracellular (pulsed peptide) pathways on autologous antigen-presenting cells expressing all human leukocyte antigen (HLA) class I and II molecules. Tumor-infiltrating lymphocytes (TILs) from 11 patients recognized autologous p53 neoantigens, which accounted for 8% and 39% of all patients sequenced (n = 140) and screened (n = 28), respectively. These responses were restricted by a variety of HLA restriction elements, including common class I (A*02:01) and class II (DPB1*02:01 and DRB1*13:01) alleles. T cell receptors (TCRs) were identified from TP53 mutation-reactive helper (CD4) and cytotoxic (CD8) T cells, and TIL and TCR gene-engineered T cells recognized tumor cell lines endogenously expressing HLA and mutant TP53. Thus, the most commonly mutated gene in cancer, TP53, appears to be immunogenic and represents an attractive candidate for evaluating targeted immune cancer therapies.

Tumor neoepitopes presented by major histocompatibility complex (MHC) class I are recognized by tumor-infiltrating lymphocytes (TIL) and are targeted by adoptive T-cell therapies. Identifying which mutant neoepitopes from tumor cells are capable of recognition by T cells can assist in the development of tumor-specific, cell-based therapies and can shed light on antitumor responses. Here, we generate a ranking algorithm for class I candidate neoepitopes by using next-generation sequencing data and a dataset of 185 neoepitopes that are recognized by HLA class I-restricted TIL from individuals with metastatic cancer. Random forest model analysis showed that the inclusion of multiple factors impacting epitope presentation and recognition increased output sensitivity and specificity compared to the use of predicted HLA binding alone. The ranking score output provides a set of class I candidate neoantigens that may serve as therapeutic targets and provides a tool to facilitate in vitro and in vivo studies aimed at the development of more effective immunotherapies.