High grade serous ovarian cancer differentiation and invasion post chemotherapy: Role of NRF2.

Abstract

e17611 Background: Epithelial ovarian cancer accounts for 90% of ovarian cancer diagnoses, about 70% of which are high grade serous ovarian cancer (HGSOC). HGSOC is the most aggressive type of ovarian cancer with limited therapeutic options. The Cancer Genome Atlas (TCGA) and other studies have shown that several molecular subtypes of HGSOC exist such as immunoreactive, differentiated, proliferative, and mesenchymal, which further complicates the effort to find therapies for this deadly cancer. HGSOC is still treated as a single disease with a combination of surgery and systemic platinum-based chemotherapy being standard initial therapy. The expression of NRF2, an antioxidant gene and anti-inflammatory pathway, is altered in about 50% of HGSOC, but its significance is unclear. In this project, we aimed to investigate the NRF2-chemotherapy interaction and the impact on treatment. Methods: We used two NRF2 Low human HGSOC cell lines, OVCAR8, and ES-2. We induced the expression of NRF2 pathway through the activation of E79Q mutation, one of the most common mutations of NRF2 found in human tumors, using pInducer20 system. Cells were treated with carboplatin or paclitaxel. Doxycycline induced the expression of NRF2 E79Q which resulted in high levels of all down stream targets of NRF2. Both cell lines with and without NRF2 expression were also treated with carboplatin or paclitaxel and differentiation markers and downstream targets were evaluated using western blot protein quantification. Results: NRF2 activation changed the differentiation markers that represent squamous (P63), growth (C-MYC), immune checkpoint (PDL-1), and epithelial to mesenchymal transition (EMT) pathways in both cell lines. Interestingly, treatment with carboplatin or paclitaxel changed NRF2 protein levels and impacted differentiation markers. Further, scratch testing showed that NRF2 Low (OVCAR8 and ES-2) cell lines treated with paclitaxel demonstrated more rapid invasion, compared to those exposed to carboplatin and no treatment (which showed similar activity). These results were different in the NRF2 High versions of OVCAR8 and ES-2, where we observed slower invasion with both carboplatin and paclitaxel treated cells compared to untreated cells. Conclusions: Our results suggest that NRF2-chemotherapy interaction may result in pathways that impact the differentiation and invasion of HGSOC.