Microenvironment mesenchymal cells protect ovarian cancer cell lines from apoptosis by inhibiting XIAP inactivation

M Castells,C Gandy,D Milhas,J-P Delord,B Couderc,A Rafii,B Thibault

doi:10.1038/cddis.2013.384

Abstract

Epithelial ovarian carcinoma is characterized by high frequency of recurrence (70% of patients) and carboplatin resistance acquisition. Carcinoma-associated mesenchymal stem cells (CA-MSC) have been shown to induce ovarian cancer chemoresistance through trogocytosis. Here we examined CA-MSC properties to protect ovarian cancer cells from carboplatin-induced apoptosis. Apoptosis was determined by Propidium Iodide and Annexin-V-FITC labelling and poly-ADP-ribose polymerase cleavage analysis. We showed a significant increase of inhibitory concentration 50 and a 30% decrease of carboplatin-induced apoptosis in ovarian cancer cells incubated in the presence of CA-MSC-conditioned medium (CM). A molecular analysis of apoptosis signalling pathway in response to carboplatin revealed that the presence of CA-MSC CM induced a 30% decrease of effector caspases-3 and -7 activation and proteolysis activity. CA-MSC secretions promoted Akt and X-linked inhibitor of apoptosis protein (XIAP; caspase inhibitor from inhibitor of apoptosis protein (IAP) family) phosphorylation. XIAP depletion by siRNA strategy permitted to restore apoptosis in ovarian cancer cells stimulated by CA-MSC CM. The factors secreted by CA-MSC are able to confer chemoresistance to carboplatin in ovarian cancer cells through the inhibition of effector caspases activation and apoptosis blockade. Activation of the phosphatidylinositol 3-kinase (PI3K)/Akt signalling pathway and the phosphorylation of its downstream target XIAP underlined the implication of this signalling pathway in ovarian cancer chemoresistance. This study reveals the potentialities of targeting XIAP in ovarian cancer therapy.

Highlights

Inside the microenvironment, we focused on the potential role of mesenchymal stem cells
We evaluated here if the factors released by CA-MSC could be associated to chemoresistance in ovarian cancer cells
We determined the drug concentrations to inhibit 50% cell growth in response to carboplatin in three different human ovarian adenocarcinoma cells (HOACs; OVCAR-3, IGROV-1 and SKOV-3 cells), as well as in CA-MSC and BM-MSC. Both CA-MSC and BM-MSC were highly sensitive to carboplatin treatment with a dose-dependent decrease of cell viability (IC50 1⁄4 40.5±12.5 mM for CA-MSC and 40±10 mM for BM-MSC) (Figure 1d and Supplementary Figure 1a)

Summary

Introduction

We focused on the potential role of mesenchymal stem cells Received 14.11.12; revised 23.8.13; accepted 26.8.13; Edited by T Brunner role in the uptake and distribution of therapeutic drugs, and their expression in the target tissue has been associated with resistance to treatment.[16] Rafii et al.[17] have shown that CA-MSC (called Hospicells in their study) are able to confer chemoresistance to ovarian and breast cancer cells by direct cell–cell contact and exchange of membrane patches (oncologic trogocytosis) and notably efflux pumps. MSC could induce chemoresistance through the release of multiple factors such as polyunsaturated fatty acids, interleukin-6 (IL-6) and vascular endothelial growth factor in the neighbourhood of tumours cells (for review see Castells et al.[19])

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Results

Conclusion