RT Journal Article SR Electronic T1 Tumor microenvironment modulation enhances immunologic benefit of chemoradiotherapy JF Journal for ImmunoTherapy of Cancer JO J Immunother Cancer FD BMJ Publishing Group Ltd SP 10 DO 10.1186/s40425-018-0485-9 VO 7 IS 1 A1 Aurelie Hanoteau A1 Jared M. Newton A1 Rosemarie Krupar A1 Chen Huang A1 Hsuan-Chen Liu A1 Angelina Gaspero A1 Robyn D. Gartrell A1 Yvonne M. Saenger A1 Thomas D. Hart A1 Saskia J. Santegoets A1 Damya Laoui A1 Chad Spanos A1 Falguni Parikh A1 Padmini Jayaraman A1 Bing Zhang A1 Sjoerd H. Van der Burg A1 Jo A. Van Ginderachter A1 Cornelis J. M. Melief A1 Andrew G. Sikora YR 2019 UL http://jitc.bmj.com/content/7/1/10.abstract AB Background Chemoradiotherapy (CRT) remains one of the most common cancer treatment modalities, and recent data suggest that CRT is maximally effective when there is generation of an anti-tumoral immune response. However, CRT has also been shown to promote immunosuppressive mechanisms which must be blocked or reversed to maximize its immune stimulating effects.Methods Therefore, using a preclinical model of human papillomavirus (HPV)-associated head and neck squamous cell carcinoma (HNSCC), we developed a clinically relevant therapy combining CRT and two existing immunomodulatory drugs: cyclophosphamide (CTX) and the small molecule inducible nitric oxide synthase (iNOS) inhibitor L-n6-(1-iminoethyl)-lysine (L-NIL). In this model, we treated the syngeneic HPV-HNSCC mEER tumor-bearing mice with fractionated (10 fractions of 3 Gy) tumor-directed radiation and weekly cisplatin administration. We compared the immune responses induced by CRT and those induced by combinatory treatment (CRT + CTX/L-NIL) with flow cytometry, quantitative multiplex immunofluorescence and by profiling immune-related gene expression changes.Results We show that combination treatment favorably remodels the tumor myeloid immune microenvironment including an increase in anti-tumor immune cell types (inflammatory monocytes and M1-like macrophages) and a decrease in immunosuppressive granulocytic myeloid-derived suppressor cells (MDSCs). Intratumoral T cell infiltration and tumor antigen specificity of T cells were also improved, including a 31.8-fold increase in the CD8+ T cell/ regulatory T cell ratio and a significant increase in tumor antigen-specific CD8+ T cells compared to CRT alone. CTX/LNIL immunomodulation was also shown to significantly improve CRT efficacy, leading to rejection of 21% established tumors in a CD8-dependent manner.Conclusions Overall, these data show that modulation of the tumor immune microenvironment with CTX/L-NIL enhances susceptibility of treatment-refractory tumors to CRT. The combination of tumor immune microenvironment modulation with CRT constitutes a translationally relevant approach to enhance CRT efficacy through enhanced immune activation.Abbreviations:CRTChemoradiotherapyCTXCyclophosphamideDCDendritic cellKLRG1Killer cell lectin-like receptorHNSCCHead and neck squamous cell carcinomaHPVHuman papillomavirusICDImmunogenic cell deathIDOIndoleamine 2,3- dioxygenaseILInterleukinsiNOSInducible nitric oxide synthaseIR-Immune response negativeIR+Immune response positiveL-NILL-n6-(1-iminoethyl)-lysineMDSCMyeloid-derived suppressor cellMHCMajor histocompatibility complexOPSCCOropharyngeal squamous cell carcinomaPCAPrincipal component analysiss.c.SubcutaneouslyTGF-βTransforming growth factor betaTLRToll-like receptorTregRegulatory T celltSNEt Stochastic neighborhood embedding