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M.C. Weiser-Evans



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    ORAL 41 - Immune Biology, Microenvironment and Novel Targets (ID 159)

    • Event: WCLC 2015
    • Type: Oral Session
    • Track: Biology, Pathology, and Molecular Testing
    • Presentations: 1
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      ORAL41.06 - Transcriptional Profiling of Distinct Macrophage Subsets in Lung Tumor Microenvironment Reveals Their Functional Heterogeneity (ID 3181)

      18:30 - 20:00  |  Author(s): M.C. Weiser-Evans

      • Abstract
      • Slides

      Background:
      Lung cancer is the leading cause of cancer-related deaths in both men and women. While extensive research has focused on genetic mutations in neoplastic epithelial cells, it has now become apparent that cancer progression and metastasis involve complex interactions between cancer cells and the cells of the tumor microenvironment. Myeloid cells of mononuclear phagocyte lineage are a significant component of the tumor microenvironment in lung cancer. Depending on the activation state, myeloid cells have been implicated in tumor – promoting processes such angiogenesis, tissue remodeling and immunosuppression, but also in anti-tumor immunity such as supporting immune surveillance and direct cytotoxicity. The goal of this study was to identify distinct populations of monocyte/macrophage cells and to gain insight into their functions through transcriptional profiling.

      Methods:
      We used an orthotopic immunocompetent mouse model, in which Lewis Lung carcinoma cells, a cell line derived from mouse adenocarcinoma, were injected directly into the left lung lobe of syngeneic C57BL/6 mice. Whole left lung lobes bearing primary tumors were harvested at 2 and at 3 weeks after cancer cell injection, together with lungs from uninjected mice. Tissues were processed into single-cell suspensions and analyzed by multi-color flow cytometry. The flow cytometry strategy employed a combination of myeloid specific surface markers such as CD11b, CD11c, CD64, and SiglecF to identify distinct monocyte/macrophage subpopulations. We recovered these cell populations by flow cytometry-based cell sorting, isolated RNA, and performed transcriptional profiling by RNA-seq. Sequencing data were analyzed by TopHat/Cufflinks/CuffDiff software package and EdgeR. To define the lineage of the isolated cells we correlated their transcriptional profiles to published profiles of immune cells from blood and lung of naïve mice. Further, we used hierarchical clustering and web-based bioinformatic pathway analysis tool to discover functions and pathways enriched in specific myeloid populations.

      Results:
      Based on the combination of myeloid markers and transcriptional profiling, we identified 4 distinct populations of monocyte/macrophage cells: MacA, which represent alveolar macrophages, MacB1, which represent a mixture of dendritic cells and Ly6C- monocytes, MacB2, which represent Ly6C+ monocytes, and MacB3, which represent interstitial/infiltrating macrophages. While the numbers of MacA and MacB1 remain unchanged with cancer progression, MacB2 and MacB3 expand rapidly. Pathway analysis indicated that each population of cells regulates distinct functions in the tumor microenvironment, such as lipid metabolism, cytokine or chemokine secretion, production and remodeling of extracellular matrix, antigen presentation.

      Conclusion:
      These data provide critical insights into the heterogeneous nature and diverse functions of myeloid cells in tumor microenvironment of lung cancer. This study has the potential for development of therapeutics that target specific subsets of myeloid cells that could complement conventional cancer-cell-targeted therapies.

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