Innate immune agonist, dsRNA, induces apoptosis in ovarian cancer cells and enhances the potency of cytotoxic chemotherapeutics.

Ovarian cancer is the most lethal gynecological cancer. Here we show that innate immune agonist, dsRNA, directly induces ovarian cancer cell death and identify biomarkers associated with responsiveness to this targeted treatment. Nuclear staining and MTT assays following dsRNA stimulation revealed two subpopulations, sensitive (OVCAR-3, CAOV-3; patient samples malignant 1 and 2) and resistant (DOV-13, SKOV-3). Microarray analysis identified 75 genes with differential expression that further delineated these two subpopulations. qPCR and immunoblot analyses showed increased dsRNA receptor expression after stimulation as compared to resistant and immortalized ovarian surface epithelial cells (e.g., 70-fold with malignant 2, 43-fold with OVCAR-3). Using agonists, antagonists, and shRNA-mediated knockdown of dsRNA receptors, we show that TLR3, RIG-I, and mda5 coordinated a caspase 8/9- and interferon-dependent cell death. In resistant cells, dsRNA receptor overexpression restored dsRNA sensitivity. When dsRNA was combined with carboplatin or paclitaxel, cell viability significantly decreased over individual treatments (1.5- to 7.5-fold). Isobologram analyses showed synergism in dsRNA combinations (CI=0.4-0.82) vs. an additive effect in carboplatin/paclitaxel treatment (CI=1.5-2). Our data identify a predictive marker, dsRNA receptor expression, to target dsRNA responsive populations and show that, in dsRNA-sensitive cells, dsRNA induces apoptosis and enhances the potency of cytotoxic chemotherapeutics.