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A. De Biasi



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    ORAL 28 - T Cell Therapy for Lung Cancer (ID 132)

    • Event: WCLC 2015
    • Type: Oral Session
    • Track: Biology, Pathology, and Molecular Testing
    • Presentations: 1
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      ORAL28.04 - Tumor-Targeted Radiation Therapy Helps Overcome the Solid Tumor T-Cell Infiltration Barrier and Promotes Mesothelin CAR T-Cell Therapy (ID 3142)

      16:45 - 18:15  |  Author(s): A. De Biasi

      • Abstract
      • Slides

      Background:
      Translating recent chimeric antigen receptor (CAR) T-cell therapy successes in hematologic malignancies to solid cancers requires overcoming barriers unique to solid tumors such as inadequate tumor infiltration, proliferation, and persistence. Our laboratory has published the rationale to target mesothelin (MSLN), a cell-surface antigen expressed in the majority of thoracic malignancies. We hypothesized that the immune modulating effects of low-dose radiation therapy (RT) would enhance the infiltration and proliferation of mesothelin-targeted CAR T-cell therapy for thoracic cancers, thereby achieving long-term tumor eradication.

      Methods:
      Using human T cells retrovirally transduced to express mesothelin-targeted CARs, we evaluated T-cell cytotoxicity by chromium release assay, proliferation by cell count assay, cytokine-release by multiplex ELISA, phenotype by flow cytometry, and chemokine receptor profiles by PCR against MSLN-expressing mesothelioma and lung cancer cell lines with and without localized RT. In clinically relevant mouse models (NOD/SCID gamma mice) with established MSLN-expressing tumors, we monitored therapy response, T-cell kinetics and anti-tumor efficacy by utilizing bioluminescent imaging (BLI), and conducted flow cytometric analysis of splenic/peripheral blood T cells for characterization of CAR T-cell effector phenotype.

      Results:
      RT did not enhance CAR T-cell cytotoxicity. In vitro, RT enhanced CAR T-cell migration in chemotactic assays, and correlatively induced the secretion of chemokines by tumor cells (Fig.1A). In vivo, RT resulted in dose dependent chemokine secretion with robust early intratumoral CAR T-cell accumulation (p<0.05, Fig.1B) as demonstrated by T-cell BLI. Ex vivo tumor analysis by flow cytometry on day 7 post T-cell administration confirmed that RT increased early infiltration and proliferation (p<0.05). Also, single low-dose RT potentiated the efficacy of systemically administered CAR T cells (median survival 30d vs. 79d, p= 0.02) with at least 50% tumor eradication up to 100 days even with a 30-fold decreased dose (Fig.1C&D). Furthermore, in mice with tumor eradication, harvested spleen T-cell analysis at day 56 demonstrated a greater number of persisting CAR T cells in mice treated with RT (p=0.02, Fig.1E).Figure 1



      Conclusion:
      Our data provides the rationale to use localized RT as a preconditioning regimen prior to CAR T-cell administration in a clinical trial for thoracic malignancies. Furthermore, our mechanistic observation of RT-induced, chemokine-mediated, enhanced T-cell infiltration may also assist the trafficking of endogenous anti-tumor T cells, thereby shifting the balance towards a cohesive anti-tumor immune microenvironment.

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