RT Journal Article SR Electronic T1 Reshaping the tumor microenvironment with oncolytic viruses, positive regulation of the immune synapse, and blockade of the immunosuppressive oncometabolic circuitry JF Journal for ImmunoTherapy of Cancer JO J Immunother Cancer FD BMJ Publishing Group Ltd SP e004935 DO 10.1136/jitc-2022-004935 VO 10 IS 7 A1 Teresa T Nguyen A1 Dong Ho Shin A1 Sagar Sohoni A1 Sanjay K Singh A1 Yisel Rivera-Molina A1 Hong Jiang A1 Xuejun Fan A1 Joy Gumin A1 Frederick F Lang A1 Christopher Alvarez-Breckenridge A1 Filipa Godoy-Vitorino A1 Lisha Zhu A1 W Jim Zheng A1 Lijie Zhai A1 Erik Ladomersky A1 Kristen L Lauing A1 Marta M Alonso A1 Derek A Wainwright A1 Candelaria Gomez-Manzano A1 Juan Fueyo YR 2022 UL http://jitc.bmj.com/content/10/7/e004935.abstract AB Background Oncolytic viruses are considered part of immunotherapy and have shown promise in preclinical experiments and clinical trials. Results from these studies have suggested that tumor microenvironment remodeling is required to achieve an effective response in solid tumors. Here, we assess the extent to which targeting specific mechanisms underlying the immunosuppressive tumor microenvironment optimizes viroimmunotherapy.Methods We used RNA-seq analyses to analyze the transcriptome, and validated the results using Q-PCR, flow cytometry, and immunofluorescence. Viral activity was analyzed by replication assays and viral titration. Kyn and Trp metabolite levels were quantified using liquid chromatography–mass spectrometry. Aryl hydrocarbon receptor (AhR) activation was analyzed by examination of promoter activity. Therapeutic efficacy was assessed by tumor histopathology and survival in syngeneic murine models of gliomas, including Indoleamine 2,3-dioxygenase (IDO)-/- mice. Flow cytometry was used for immunophenotyping and quantification of cell populations. Immune activation was examined in co-cultures of immune and cancer cells. T-cell depletion was used to identify the role played by specific cell populations. Rechallenge experiments were performed to identify the development of anti-tumor memory.Results Bulk RNA-seq analyses showed the activation of the immunosuppressive IDO-kynurenine-AhR circuitry in response to Delta-24-RGDOX infection of tumors. To overcome the effect of this pivotal pathway, we combined Delta-24-RGDOX with clinically relevant IDO inhibitors. The combination therapy increased the frequency of CD8+ T cells and decreased the rate of myeloid-derived suppressor cell and immunosupressive Treg tumor populations in animal models of solid tumors. Functional studies demonstrated that IDO-blockade-dependent activation of immune cells against tumor antigens could be reversed by the oncometabolite kynurenine. The concurrent targeting of the effectors and suppressors of the tumor immune landscape significantly prolonged the survival in animal models of orthotopic gliomas.Conclusions Our data identified for the first time the in vivo role of IDO-dependent immunosuppressive pathways in the resistance of solid tumors to oncolytic adenoviruses. Specifically, the IDO-Kyn-AhR activity was responsible for the resurface of local immunosuppression and resistance to therapy, which was ablated through IDO inhibition. Our data indicate that combined molecular and immune therapy may improve outcomes in human gliomas and other cancers treated with virotherapy.All data relevant to the study are included in the article or uploaded as online supplemental information.