BRCA status dictates Wnt responsiveness in epithelial ovarian cancer.

The association of BRCA1 and BRCA2 mutations with increased risk for developing epithelial ovarian cancer is well established. However, the observed clinical differences, particularly the improved therapy response and patient survival in BRCA2 mutant (BRCA2mt) patients are unexplained. Our objective is to identify molecular pathways that are differentially regulated upon the loss of BRCA1 and BRCA2 function in ovarian cancer. Transcriptomic and pathway analysis comparing BRCA1 mutant (BRCA1mt), BRCA2mt and homologous recombination wild-type (HRwt) ovarian tumors showed differential regulation of the Wnt/β-catenin pathway. Using Wnt3A-treated BRCA1/2 wild-type (BRCAwt), BRCA1null and BRCA2null mouse ovarian cancer cells, we observed preferential activation of the canonical Wnt/β-catenin signaling in BRCAwt ovarian cancer cells while the non-canonical Wnt/β-catenin signaling was preferentially activated in the BRCA1null cells. Interestingly, BRCA2null mouse ovarian cancer cells, demonstrated a unique response to Wnt3A with the preferential upregulation of the Wnt signaling inhibitor, Axin2. In addition, decreased phosphorylation and enhanced stability of β-catenin were observed in BRCA2null mouse ovarian cancer cells, which correlated with increased inhibitory phosphorylation on GSK3β. These findings open venues for the translation of these molecular observations into modalities that can impact patient survival.