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S. Ma



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    MINI 24 - Epidemiology, Early Detection, Biology (ID 140)

    • Event: WCLC 2015
    • Type: Mini Oral
    • Track: Thymoma, Mesothelioma and Other Thoracic Malignancies
    • Presentations: 1
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      MINI24.14 - Use of Next Generation Sequencing to Improve Lung Tumor Immunotherapy (ID 1749)

      18:00 - 18:05  |  Author(s): S. Ma

      • Abstract
      • Presentation
      • Slides

      Background:
      Immunotherapy of pulmonary tumors is now a clinical reality, however most patients do not respond. To convert non-responders into responders one potential approach is to identify the tumor‐specific ‘neo‐antigens’ that arise from DNA mutations in order to follow tumor-specific responses and to design therapeutic vaccines to try to ‘enforce’ a response against these resistant tumors.

      Methods:
      First, in order to identify tumor neo-antigens we performed RNAseq and exome analysis to identify single nucleotide variants (SNV) in murine pulmonary tumors. An average of 485 SNVs was found. We focused on AB1 and AB1-HA (asbestos-induced mesotheliomas, which mimic human mesothelioma) and Line 1 (lung cancer). We used the NetMHCpan 2.8 algorithm to identify candidate mutation‐carrying peptides and screened them in an interferon‐γ ELISPOT assay. Second, to determine if more neo-antigens could be ‘unmasked’ by therapy, we tested three candidate therapies in our murine model then reanalyzed neo-antigen responses a) Treg depletion using Foxp3-DTR mice, b) gemcitabine, an immunogenic cytotoxic chemotherapy commonly used for pulmonary malignancies, and c) antiCTLA4 (a checkpoint blockade therapy).

      Results:
      We identified 20 candidate mutation‐carrying peptides in the ELISPOT assay. A strong spontaneous endogenous pre-treatment immune response was demonstrated to DUqcrc2, a component of the respiratory chain protein ubiquinol cytochrome complex. It was found to stimulate a strong response at a similar magnitude to the model neo-antigen viral haemagglutinin (HA). The DUqcrc2 peptide sequence (amino acid 405-413) is predicted to bind the H-2Kd, and the mutant has a proline to alanine substitution mutation at position 408. Treg depletion unmasked a second neo-antigen, DGANAB. GANAB is an alpha glucosidase which cleaves the 2 innermost alpha-1,3-linked glucose residues from the Glc-2-Man-9-GlcNAc-2 oligosaccharide precursor of immature glycoproteins. There is an arginine to glutamine substitution mutation at position 969 of DGANAB (965-972) sequence. This observation supports the theory that removing Treg cells may broaden the immune response to a greater number of neo-antigens, a response presumably otherwise restrained by Treg suppression. Gemcitabine and antiCTLA4 checkpoint blockade did not unmask any additional neo-antigens.

      Conclusion:
      Thus, removing some immune restraints may expose a greater number of neo-antigens as potential clinical targets. The results from these approaches suggest novel ways to improve the immunotherapy of lung tumor and are the basis for planning current clinical trials.

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