authors contributed equally 2 One Sentence Summary: A STAT1-driven inflammatory phenotype associated with response to checkpoint blocking antibodies can be therapeutically attained and sensitizes cancers to immunotherapy. Abstract:Cancer immunotherapy using antibodies that target immune checkpoints has delivered outstanding results. However, responses only occur in a subset of patients and it is not fully understood what biological processes determine an effective outcome. This lack of understanding hinders the development of rational combination treatments. We set out to define the pretreatment microenvironment associated with an effective outcome by utilizing the fact that inbred mouse strains bearing monoclonal cancer cell line-derived tumors respond in a dichotomous manner to immune checkpoint blockade (ICB). We compared the cellular composition and gene expression profiles of responsive and non-responsive tumors from mice before ICB, and validated the findings in cancer patient cohorts treated with antibodies targeting the PD-1/PD-L1 pathway. We found that responsive tumors were characterized by an inflammatory gene expression signature consistent with upregulation of STAT1 and TLR3 signaling, and down-regulation of IL-10 signaling. In addition, responsive tumors had more infiltrating activated natural killer (NK) cells, which were necessary for response. Pretreatment of different mouse strains with large established tumors, using a combination of the STAT1activating cytokine IFNγ, the TLR3 ligand poly(I:C) and an anti-IL-10 antibody sensitized tumors to ICB by attracting IFNγ-producing NK cells into the tumor, resulting in increased cure rates. Our results identify a pretreatment cellular and molecular tumor microenvironment that predicts response to ICB, which can be therapeutically attained. This data anticipates a biomarker-driven approach to patient management to establish whether a patient would benefit from treatment with sensitizing therapeutics before ICB. Introduction:

2018) Combination immune checkpoint blockade as an effective therapy for mesothelioma, OncoImmunology, 7:10, e1494111, ABSTRACT Mesothelioma is an aggressive asbestos induced cancer with extremely poor prognosis and limited treatment options. Immune checkpoint blockade (ICPB) has demonstrated effective therapy in melanoma and is now being applied to other cancers, including mesothelioma. However, the efficacy of ICPB and which immune checkpoint combinations constitute the best therapeutic option for mesothelioma have yet to be fully elucidated. Here, we used our well characterised mesothelioma tumour model to investigate the efficacy of different ICBP treatments to generate effective therapy for mesothelioma. We show that tumour resident regulatory T cell co-express high levels of CTLA-4, OX40 and GITR relative to T effector subsets and that these receptors are co-expressed on a large proportion of cells. Targeting any of CTLA-4, OX40 or GITR individually generated effective responses against mesothelioma. Furthermore, the combination of αCTLA-4 and αOX40 was synergistic, with an increase in complete tumour regressions from 20% to 80%. Other combinations did not synergise to enhance treatment outcomes. Finally, an early pattern in T cell response was predictive of response, with activation status and ICP receptor expression profile of T effector cells harvested from tumour and dLN correlating with response to immunotherapy. Taken together, these data demonstrate that combination ICPB can work synergistically to induce strong, durable immunity against mesothelioma in an animal model. ARTICLE HISTORY