TY - JOUR T1 - Immune microenvironment modulation unmasks therapeutic benefit of radiotherapy and checkpoint inhibition JF - Journal for ImmunoTherapy of Cancer JO - J Immunother Cancer DO - 10.1186/s40425-019-0698-6 VL - 7 IS - 1 SP - 216 AU - Jared M. Newton AU - Aurelie Hanoteau AU - Hsuan-Chen Liu AU - Angelina Gaspero AU - Falguni Parikh AU - Robyn D. Gartrell-Corrado AU - Thomas D. Hart AU - Damya Laoui AU - Jo A. Van Ginderachter AU - Neeraja Dharmaraj AU - William C. Spanos AU - Yvonne Saenger AU - Simon Young AU - Andrew G. Sikora Y1 - 2019/12/01 UR - http://jitc.bmj.com/content/7/1/216.abstract N2 - Background Immune checkpoint inhibitors (ICIs) for solid tumors, including those targeting programmed cell death 1 (PD-1) and cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), have shown impressive clinical efficacy, however, most patients do not achieve durable responses. One major therapeutic obstacle is the immunosuppressive tumor immune microenvironment (TIME). Thus, we hypothesized that a strategy combining tumor-directed radiation with TIME immunomodulation could improve ICI response rates in established solid tumors.Methods Using a syngeneic mouse model of human papillomavirus (HPV)-associated head and neck cancer, mEER, we developed a maximally effective regimen combining PD-1 and CTLA-4 inhibition, tumor-directed radiation, and two existing immunomodulatory drugs: cyclophosphamide (CTX) and a small-molecule inducible nitric oxide synthase (iNOS) inhibitor, L-n6-(1-iminoethyl)-lysine (L-NIL). We compared the effects of the various combinations of this regimen on tumor growth, overall survival, establishment of immunologic memory, and immunologic changes with flow cytometry and quantitative multiplex immunofluorescence.Results We found PD-1 and CTLA-4 blockade, and radiotherapy alone or in combination, incapable of clearing established tumors or reversing the unfavorable balance of effector to suppressor cells in the TIME. However, modulation of the TIME with cyclophosphamide (CTX) and L-NIL in combination with dual checkpoint inhibition and radiation led to rejection of over 70% of established mEER tumors and doubled median survival in the B16 melanoma model. Anti-tumor activity was CD8+ T cell-dependent and led to development of immunologic memory against tumor-associated HPV antigens. Immune profiling revealed that CTX/L-NIL induced remodeling of myeloid cell populations in the TIME and tumor-draining lymph node and drove subsequent activation and intratumoral infiltration of CD8+ effector T cells.Conclusions Overall, this study demonstrates that modulation of the immunosuppressive TIME is required to unlock the benefits of ICIs and radiotherapy to induce immunologic rejection of treatment-refractory established solid tumors.Abbreviations:APCsAntigen-presenting cellsCPRCTX/L-NIL+ αPD-1/αCTLA-4 + radiation combination treatmentCTLA-4Cytotoxic T lymphocyte associated antigen-4CTXCyclophosphamideDCsDendritic cellsHNSCCHead and neck squamous cell carcinomaHPVHuman papillomavirusICIsImmune checkpoint inhibitorsiNOSInducible nitric oxide synthaseKLRG1Killer cell lectin-like receptorL-NILL-n6-(1-iminoethyl)-lysineMDSCMyeloid-derived suppressor cellsMHCMajor histocompatibility complexPBMCsPeripheral blood mononuclear cellsPD-1Programmed cell death protein-1pDCsPlasmacytoid dendritic cellsRTRadiotherapySBRTStereotactic body radiotherapySTINGStimulator of interferon genestdLNTumor-draining lymph nodeTIMETumor immune microenvironmentTregsRegulatory T cellst-SNEt-stochastic neighbor embedding ER -