Author of

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  MA04 - Models and Biomarkers (ID 122)

  • Event: WCLC 2019
  • Type: Mini Oral Session
  • Track: Biology
  • Presentations: 1
  • Now Available
  • Moderators:Montse Sanchez-Cespedes, Kwok-kin Wong
  • Coordinates: 9/08/2019, 13:30 - 15:00, Interlaken (1988)

  • 29986

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    MA04.11 - Biological and Prognostic Implications of the Long Non-Coding Transcriptome in Tumour-Infiltrating Immune Cells (Now Available) (ID 2838)

    13:30 - 15:00  |  Presenting Author(s): Kevin W Ng
    • Abstract
    • Presentation
    • Slides

    Background
    

    The lung tumour microenvironment is defined by complex infiltration patterns of immune cells which can contribute to both tumour progression and rejection. The advent of targeted immunotherapies has transformed cancer therapy, leading to durable regression even in late-stage lung tumours. Single-cell RNA sequencing and deconvolution of bulk tumour samples have provided insight into the transcriptomes of tumour-infiltrating immune populations and the regulatory networks that promote cytotoxicity and exhaustion transcriptional programs. Long non-coding RNAs (lncRNAs) have emerged as master regulators of gene expression in tumour cells, but their role in immune cells remains undercharacterized. We sought to delineate lncRNA expression profiles in healthy and lung tumour-infiltrating immune cells in order to better understand transcriptional reprogramming in tumour-infiltrating immune cells and to explore their potential as biomarkers of patient outcome and response to immunotherapy.

    Method
    

    RNAseq profiles of flow-purified adaptive and innate immune subsets were analysed for lncRNA expression, yielding 4919 expressed lncRNAs. Immune lncRNAs were then mapped to tumour and paired non-malignant lung adenocarcinoma samples (TCGA n=108, BCCA n=72) and associated with infiltrating immune populations by deconvolution and methylation-based purity scores. Associations with tumour immunogenicity were assessed by somatic mutational load and expression of tumour-associated antigens. Immune-specific expression of lncRNAs was confirmed in an external single cell RNAseq dataset of lung adenocarcinomas (n=5).

    Result
    

    We found that lncRNA expression patterns display markedly greater cell-type specificity than protein-coding genes in healthy samples, supporting their role in cell-intrinsic transcriptional regulation. 323 immune lncRNAs were differentially expressed in lung tumours compared to matched non-malignant tissue, with enriched expression of immune lncRNAs in tumours with high antigenic load. Many of these genes were positively correlated with CD45 expression and negatively correlated with tumour purity, suggestive of immune cell-restricted expression patterns. Furthermore, a substantial proportion of these genes showed decreased expression in microdissected tumour samples, suggesting that immune-derived lncRNAs may account for gene expression patterns observed in bulk tumour data. We validated these findings in a scRNAseq dataset and analysed co-expression patterns of immune lncRNAs with immune cell markers in order to identify specific immune cell phenotypes and assess the interaction of immune lncRNAs with cytotoxicity and exhaustion transcriptional networks. We identify immune lncRNAs which may regulate expression of important immune genes related to NK and CD8+ T cell cytotoxicity, as well as immune lncRNAs which predict patient outcome and response.

    Conclusion
    

    We present an atlas of lncRNAs expressed in innate and adaptive immune cells, emphasizing the multifaceted roles of lncRNAs in homeostasis and anti-tumour immunity. We highlight the potential of immune infiltrate to confound differential expression analysis of bulk tumour RNAseq data, with consideration needed for tumour purity and immune infiltration levels. Our data provide a resource that will facilitate further identification of functionally and clinically useful lncRNAs.

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