Metronomic Radiotherapy Reverses Tumor Immune Desertification and Resistance to Immunotherapy
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ABSTRACT: The development of approaches for inflaming cold tumors is critical for increasing response to immunotherapy (IMT) reliant upon the re-invigoration of T cells for tumor control. Here we report, in a pre-clinical advanced ID8 ovarian cancer model, that metronomic low-dose radiotherapy (LDRT; 1 Gy) promotes T-cell infiltration and enables responsiveness to treatment including low-dose cyclophosphamide (CP), and combinatorial IMT comprising immune checkpoint blockade (ICB) targeting PD-1 and CTLA-4, and anti-CD40 agonist antibody, for significant tumor control and survival. Responses to this radio-combinatorial immunotherapy (RACIM) relied upon re-programming of both innate and adaptive immunity. We further identified RACIM-induced intratumoral dendritic cell states with co-stimulatory capacity and expressing the stress ligand RAE1, as well as of polyfunctional NKG2D+TCF1-PD1+CD4+T cells. We further report major tumor regressions in a subset of advanced cancer patients for which cold tumors were treated with LDRT, CP, aspirin, and ICB (NCT03728179). Unbiased analyses of biopsies revealed T-cell infiltration, up-regulation of type I IFN, and Th1 signatures as well as down-regulation of M2 macrophage and epithelial to mesenchymal transition gene-signatures, and a more oligoclonal TCR repertoire after RACIM, in responding patients.
ORGANISM(S): Mus musculus
PROVIDER: GSE166303 | GEO | 2021/08/16
REPOSITORIES: GEO
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