Anatomically and Functionally Distinct Lung Mesenchymal Populations Marked by Lgr5 and Lgr6

The diversity of mesenchymal cell types in the lung that influence epithelial homeostasis and regeneration is poorly defined. We used genetic lineage tracing, single-cell RNA sequencing, and organoid culture approaches to show that Lgr5 and Lgr6, well-known markers of stem cells in epithelial tissues, are markers of mesenchymal cells in the adult lung. Lgr6 + cells comprise a subpopulation of smooth muscle cells surrounding airway epithelia and promote airway differentiation of epithelial progenitors via Wnt-Fgf10 cooperation. Genetic ablation of Lgr6 + cells impairs airway injury repair in vivo. Distinct Lgr5 + cells are located in alveolar compartments and are sufficient to promote alveolar differentiation of epithelial progenitors through Wnt activation. Modulating Wnt activity altered differentiation outcomes specified by mesenchymal cells. This identification of region- and lineage-specific crosstalk between epithelium and their neighboring mesenchymal partners provides new understanding of how different cell types are maintained in the adult lung. Keywords: mesenchymal cells; bronchiolar epithelium; alveolar epithelium; lung stem cells; lung; differentiation; niche; Wnt signalin

31st Annual Meeting and Associated Programs of the Society for Immunotherapy of Cancer (SITC 2016) : part two

Background The immunological escape of tumors represents one of the main ob- stacles to the treatment of malignancies. The blockade of PD-1 or CTLA-4 receptors represented a milestone in the history of immunotherapy. However, immune checkpoint inhibitors seem to be effective in specific cohorts of patients. It has been proposed that their efficacy relies on the presence of an immunological response. Thus, we hypothesized that disruption of the PD-L1/PD-1 axis would synergize with our oncolytic vaccine platform PeptiCRAd. Methods We used murine B16OVA in vivo tumor models and flow cytometry analysis to investigate the immunological background. Results First, we found that high-burden B16OVA tumors were refractory to combination immunotherapy. However, with a more aggressive schedule, tumors with a lower burden were more susceptible to the combination of PeptiCRAd and PD-L1 blockade. The therapy signifi- cantly increased the median survival of mice (Fig. 7). Interestingly, the reduced growth of contralaterally injected B16F10 cells sug- gested the presence of a long lasting immunological memory also against non-targeted antigens. Concerning the functional state of tumor infiltrating lymphocytes (TILs), we found that all the immune therapies would enhance the percentage of activated (PD-1pos TIM- 3neg) T lymphocytes and reduce the amount of exhausted (PD-1pos TIM-3pos) cells compared to placebo. As expected, we found that PeptiCRAd monotherapy could increase the number of antigen spe- cific CD8+ T cells compared to other treatments. However, only the combination with PD-L1 blockade could significantly increase the ra- tio between activated and exhausted pentamer positive cells (p= 0.0058), suggesting that by disrupting the PD-1/PD-L1 axis we could decrease the amount of dysfunctional antigen specific T cells. We ob- served that the anatomical location deeply influenced the state of CD4+ and CD8+ T lymphocytes. In fact, TIM-3 expression was in- creased by 2 fold on TILs compared to splenic and lymphoid T cells. In the CD8+ compartment, the expression of PD-1 on the surface seemed to be restricted to the tumor micro-environment, while CD4 + T cells had a high expression of PD-1 also in lymphoid organs. Interestingly, we found that the levels of PD-1 were significantly higher on CD8+ T cells than on CD4+ T cells into the tumor micro- environment (p < 0.0001). Conclusions In conclusion, we demonstrated that the efficacy of immune check- point inhibitors might be strongly enhanced by their combination with cancer vaccines. PeptiCRAd was able to increase the number of antigen-specific T cells and PD-L1 blockade prevented their exhaus- tion, resulting in long-lasting immunological memory and increased median survival

Investigation of endogenous and adoptively transferred T cell function in a genetic mouse model of lung adenocarcinoma

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Biology, 2019Cataloged from PDF version of thesis. Vita.Includes bibliographical references.The clinical success of immune checkpoint blockade, including in patients with lung cancer, has clearly demonstrated that the body's immune system is capable of tumor cytotoxicity if modulated appropriately. Unfortunately, only a minority of patients with solid tumors respond to checkpoint blockade, and even fewer respond to other immunotherapeutic modalities like adoptive cell therapy (ACT). The reasons for these low response rates are not well understood, suggesting an improved understanding of the mechanisms which shape a tumor immune response and promote T cell dysfunction is needed. Toward these ends, we first sought to characterize the transcriptional changes leading to toward dysfunction in endogenous T cell responses. Using an autochthonous mouse model of lung adenocarcinoma, we longitudinally profiled CD8⁺ T cells from the lungs of tumor bearing mice using single cell RNAseq (scRNAseq).We identified significant longitudinal changes within the tumor specific T cell population over the course of more than 20 weeks of tumor development. Among these transcriptional changes was a transition from functional effector cells, to states of T cell exhaustion. We used this information to develop a signature which identifies T cells that are more readily reinvigorated by checkpoint blockade. We also identified multiple factors which promote heterogeneity within the tumor specific T cell response including TCR affinity for antigen and antigen identity within a dominance hierarchy. We close this 2nd chapter by demonstrating that this transcriptional information allows for the identification of mediators limiting anti-tumor T cell responses. Modern adoptive cell therapy has demonstrated remarkable, durable efficacy in treating patients with hematological malignancies but has failed to deliver comparable efficacy in patients with solid tumors like NSCLC.In Chapter 3, we transcriptionally profiled adoptively transferred cells in our autochthonous mouse model of lung cancer and identified multiple mechanisms which limit ACT efficacy. We used this transcriptional data to perform focused in vivo CRISPR mediated screens to identify mediators of T cell dysfunction. We identify a number of genes limiting T cell persistence and functionality within the tumor microenvironment and demonstrate that by ablating expression of these genes, we can dramatically improve the efficacy of ACT.by David Canner.Ph. D.Ph.D. Massachusetts Institute of Technology, Department of Biolog

IL-33 Signaling Alters Regulatory T Cell Diversity in Support of Tumor Development

Regulatory T cells (Tregs) can impair anti-tumor immune responses and are associated with poor prognosis in multiple cancer types. Tregs in human tumors span diverse transcriptional states distinct from those of peripheral Tregs, but their contribution to tumor development remains unknown. Here, we use single-cell RNA sequencing (RNA-seq) to longitudinally profile dynamic shifts in the distribution of Tregs in a genetically engineered mouse model of lung adenocarcinoma. In this model, interferon-responsive Tregs are more prevalent early in tumor development, whereas a specialized effector phenotype characterized by enhanced expression of the interleukin-33 receptor ST2 is predominant in advanced disease. Treg-specific deletion of ST2 alters the evolution of effector Treg diversity, increases infiltration of CD8+ T cells into tumors, and decreases tumor burden. Our study shows that ST2 plays a critical role in Treg-mediated immunosuppression in cancer, highlighting potential paths for therapeutic intervention