Cell-autonomous Inflammation of BRCA1-deficient Ovarian Cancers Drives Intrinsic Immunoreactivity and Immune Resistance through STING and VEGF

BRCA1 loss leads to tumor cell transcriptional reprogramming, resulting in a DNA damage-driven, mandatory cell-autonomous type I IFN inflammatory activation mediated by STING and TREX1/2. PARP inhibition augmented this immunoreactivity, creating contextual lethality to dual immune checkpoint blockade (ICB) in vivo. BRCA1-deficient tumor can escape T-cell inflammation through targeted deletion or methylation of the DNA sensing/IFN pathway genes, such as STING, IFNB1 or the chemokine CCL5. Alternatively, BRCA-mutated carcinomas retaining immunoreactivity upregulate their VEGF-A expression driven by STING, which mediates immune resistance and tumor progression. STING elimination attenuated tumor growth and abrogated therapeutic resistance to dual ICB. VEGF-A blockade synergized with immune checkpoint blockade and/or PARP inhibition to control outgrowth of Brca1-/- ovarian tumors, offering opportunities for rational combination therapy of cancers with homologous recombination repair deficiency (HRD). RNAseq analysis of ID8 Trp53-/-Brca1-/- tumors treated with Olaparib and/or/or dual PD-L1/CTLA-4 blockade and/or anti-VEGFA