Abstract 850: The Pi3K/Akt pathway mediates epithelial-mesenchymal transition (EMT) and malignant progression in BRCA-defective epithelial ovarian cancer
Authors: Alexandre Mehida , Lin Z Ping , Ratner Elena S. 
Published: July 2017

Objectives: Despite improvement in therapy, the majority of patients with ovarian cancer relapses and eventually succumbs to the disease. Therefore, there is an urgent need for further understanding the development and progression of ovarian cancer. It is well established that the phosphatidylinositol 3-kinase (Pi3k/Akt) pathway is activated in 70% of ovarian cancers. We have previously shown that in AKT activity is up regulated in BRCA1 and BRCA-2 deficient cancer. Epithelial-mesenchymal transition (EMT), a process by which cells acquire motility and lose their intercellular adhesions, plays an important role in normal development. Cancer cells have been shown to exhibit similar EMT-like process during invasion and metastasis. Recently, the activation of the Pi3k/Akt pathway is emerging as a central feature of EMT. This study aims to investigate whether activation of the Pi3k/Akt pathway is necessary for promoting EMT and malignant progression in BRCA-defective ovarian cancer.

Methods: BRCA2-mutated PEO1 and BRCA2-wild type PEO4 epithelial ovarian cancer cell lines were derived from the same patient at first and second relapse, respectively, following platinum-based chemotherapy. Non-targeted siRNA control (NTC) and BRCA1-knockdown (BRCA1-kd) SKOV3 cell lines were previously established in our laboratory. Western blot analysis and luciferase reporter assay were performed to determine EMT markers (snail, slug, fibronectin) in BRCA defective ovarian cancer cells. Scratch wound assays were conducted to determine the ability of cells to migrate. Clonogenic and apoptosis assays were carried out to determine cell survival in response to various concentrations of carboplatin and olaparib with or without MK-2206, a small molecule inhibitor of AKT.

Results: PEO1 cells exhibited an increase in mesenchymal markers Snail and fibronectin, whereas PEO4 cells exhibited an increase in the epithelial marker E-cadherin. PEO1 cells also exhibited an increase in cell migration compared with PEO4 cells. In the luciferase reporter assay, BRCA2- mutated PEO1 and BRCA-1 Kd SKOV3 cells exhibited lower levels of the epithelial maker, E-cadherin compared to their BRCA-wild type counterparts, PEO4 and SKOV3 NTC, respectively. Treatment with MK-2206 caused increased susceptibility of BRCA1-kd SKOV3 cells to olaparib compared with BRCA1-wild type SKOV3-NTC cells.

Conclusions: BRCA2-mutated PEO1cells manifested an increase in mesenchymal markers and invasive phenotypes. BRCA1-Kd SKOV3 cells manifested a decrease in the epithelial trait, E-cadherin activity. In addition, AKT inhibition heightened susceptibility of BRCA-1Kd SKOV3 cells to DNA damaging agents such as olaparib. These findings suggest that BRCA-defective cells rely on the induction of EMT via activation of AKT to survive DNA damage and develop therapeutic resistance during malignant progression.

Citation Format: Mehida Alexandre, Z Ping Lin, Elena S. Ratner. The Pi3K/Akt pathway mediates epithelial-mesenchymal transition (EMT) and malignant progression in BRCA-defective epithelial ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 850. doi:10.1158/1538-7445.AM2017-850