Notch3 induces epithelial-mesenchymal transition and attenuates carboplatin-induced apoptosis in ovarian cancer cells

Objective. Notch3 is implicated in chemoresistance of ovarian cancer, yet the molecular mechanism underlying Notch3-mediated drug resistance remains to be elucidated. Here, we investigated the role of Notch3 in carboplatin-induced apoptosis in ovarian cancer cells. Methods. Ovarian cancer cell line OVCA429 cells were stably transduced with an empty vector or a retroviral vector expressing the Notch3 intracellular domain (NICD3, the constitutively active form of Notch3) to generate OVCA429/vector and OVCA429/NICD3 cells. Epithelial-mesenchymal transition (EMT) was determined by morphological change and expression of the EMT markers. Carboplatin-induced cytotoxicity was determined by the neutral red uptake assay. Apoptosis was determined by Annexin V staining and Western blotting. Carboplatin-induced phosphorylation of extracellular signal-regulated kinase (ERIC) was identified by a phospho-kinase array and confirmed by Western blotting. Results. Activation of Notch3 in OVCA429 cells causes a spindle and fibroblast-like morphology, induces the expression of smooth muscle et-actin, Slug and Snail, but decreases the expression of E-cadherin, indicating that Notch3 activation induces EMT in OVCA429 cells. Furthermore, Notch3 activation renders OVCA429 cells more resistant to carboplatin-indriced cytotoxicity and attenuates carboplatin-induced apoptosis in these cells. Our results indicate that phosphorylation of ERIC is a positive regulator of carboplatin-induced apoptosis in OVCA429 cells. Interestingly, carboplatin-induced ERIC phosphorylation is inhibited by Notch3 activation. Conclusions. Notch3 activation induces EMT and attenuates carboplatin-induced apoptosis in OVCA429 cells. ERIC phosphorylation plays a pro-apoptotic role in carboplatin-induced apoptosis in OVCA429 cells. Interestingly, Notch3 activation attenuates carboplatin-induced ERIC phosphorylation in these cells. (C) 2013 Elsevier Inc. All rights reserved.