Overcoming resistance to anti-VEGF therapy via epigenetic regulation of BARD1 [SKOV3 BARD1 siRNA-RNASeq]

Despite widespread use of anti-vascular endothelial growth factor (VEGF) antibody (AVA) for cancer therapy, most patients develop progressive disease after initial response. Therefore, novel strategies are needed to understand and overcome AVA resistance. Here, we identify an unexpected role of BRCA1-associated RING domain 1 (BARD1) in overcoming adaptive resistance to AVA. We investigated the effects of epigenetic modulation on cellular response to AVA; in particular, the molecular effects of both global and targeted DNA methylation. Using in vitro assays, BARD1 was identified as being specifically involved in angiogenesis. Sequential treatment with azacytidine overcame AVA therapy resistance in cancer models in vivo. We further demonstrated that specifically targeting BARD1 with either small-interfering RNA or CpG-targeted demethylation reduced tumor growth when combined with AVA therapy (compared with AVA alone) in mouse models of ovarian cancer. These results identify a previously unrecognized role for BARD1 in tumor angiogenesis and show that targeted restoration of BARD1 can enhance the efficacy of AVA therapy in cancer models. To understand the effect of BARD1 silencing on tumor angiogenesis pathways, we performed RNA sequencing of BARD1-silenced SKOV3ip1 cells. We transfected SKOV3ip1 cells with BARD1 siRNA or control siRNA for 48h, then subjected to RNA isolation follewed by RNAsequencing.