Cell-autonomous inflammation of BRCA1-deficient ovarian cancers drives both tumor-intrinsic immunoreactivity and immune resistance via STING

In this study, we investigate mechanisms leading to inflammation and immunoreactivity in ovarian tumors with homologous recombination deficiency (HRD). BRCA1 loss is found to lead to transcriptional reprogramming in tumor cells and cell-intrinsic inflammation involving type I interferon (IFN) and stimulator of IFN genes (STING). BRCA1-mutated (BRCA1mut) tumors are thus T cell inflamed at baseline. Genetic deletion or methylation of DNA-sensing/IFN genes or CCL5 chemokine is identified as a potential mechanism to attenuate T cell inflammation. Alternatively, in BRCA1mut cancers retaining inflammation, STING upregulates VEGF-A, mediating immune resistance and tumor progression. Tumor-intrinsic STING elimination reduces neoangiogenesis, increases CD8+ T cell infiltration, and reverts therapeutic resistance to dual immune checkpoint blockade (ICB). VEGF-A blockade phenocopies genetic STING loss and synergizes with ICB and/or poly(ADP-ribose) polymerase (PARP) inhibitors to control the outgrowth of Trp53−/−Brca1−/− but not Brca1+/+ ovarian tumors in vivo, offering rational combinatorial therapies for HRD cancers. [Display omitted] •STING and type I IFN pathway activation leads to T cell infiltration in BRCA1mut OC•STING drives VEGF-A upregulation in BRCA1mut tumor cells•STING loss reduces angiogenesis, boosts CD8 T cells, and reverts dual ICB resistance•Anti-VEGF-A, PARPis, and dual ICB combination control Brca1−/− tumor growth in vivo Bruand et al. provide insights into the dual role of STING in promoting tumor-intrinsic mechanisms of both immunoreactivity, driven by DNA sensing and type I IFN, and also VEGF-A-driven immune resistance in BRCA1mut ovarian cancers. STING elimination reduces neoangiogenesis, increases CD8+ T cell infiltration, and reverts therapeutic resistance to dual ICB.