Calcium signals inhibition sensitizes ovarian carcinoma cells to anti-Bcl-xL strategies through Mcl-1 down-regulation.

Marie-Laure Bonnefond,Emilie Brotin,Laurent Poulain,Mor Sény Gueye,Pascal Gauduchon,Florence Giffard,Edwige Abeilard,Marie-Hélène Louis,Bernard Lambert,Monique N’Diaye

doi:10.1007/s10495-015-1095-3

Abstract

Ovarian carcinoma is the leading cause of death from gynecologic cancer in the developed world and is characterized by acquired chemoresistance leading to an overall 5-year survival rate of about 30 %. We previously showed that Bcl-xL and Mcl-1 cooperatively protect platinum-resistant ovarian cancer cells from apoptosis. Despite BH3-mimetics represent promising drugs to target Bcl-xL, anti-Mcl-1 strategies are still in pre-clinical studies and required new investigations. Calcium is a universal second messenger and dysregulation of calcium signal is often observed during carcinogenesis. As change in cytosolic free calcium concentration [Ca2+]i is known to control the fate of the cell by regulating Bcl-2 family members, we wonder if calcium signal could impact on Mcl-1 expression and if its pharmacological inhibition could be useful to sensitize ovarian carcinoma cells to anti-Bcl-xL strategies. We therefore studied the effect of different calcium signals inhibitors in ovarian carcinoma cell lines SKOV3 and IGROV1-R10 and analysed their effects on proliferation and Mcl-1 expression. We also exposed these cells to these inhibitors in combination with anti-Bcl-xL strategies (siRNA or BH3-mimetic: ABT-737). We found that calcium signaling regulates Mcl-1 through translational events and a calmodulin-mediated pathway. BAPTA-AM and calmodulin inhibitor combination with ABT-737 leads to apoptosis, a process that is reversed by Mcl-1 enforced expression. As Mcl-1 represents a crucial hurdle to the success of chemotherapy, these results could open to new area of investigation using calcium modulators to directly or indirectly target Mcl-1 and thus efficiently sensitize ovarian carcinoma cells to anti-Bcl-xL strategies.Electronic supplementary materialThe online version of this article (doi:10.1007/s10495-015-1095-3) contains supplementary material, which is available to authorized users.

Highlights

Ovarian cancer causes more than 140 000 deaths worldwide every year, and is the most lethal gynaecological malignancy in developed countries [1]
The downregulation of either Bcl-xL or Mcl-1 remains ineffective, we showed that the concomitant inhibition of these proteins with siRNA was sufficient to induce massive cell death, highlighting the pivotal role these anti-apoptotic proteins play in chemoresistant ovarian carcinoma and mesothelioma [5]
As Bcl-xL and Mcl-1 cooperates to prevent ovarian carcinoma cells from apoptosis, we evaluated the efficacy of BAPTA-AM/anti-BclxL strategies combinations

Summary

Introduction

Ovarian cancer causes more than 140 000 deaths worldwide every year, and is the most lethal gynaecological malignancy in developed countries [1]. Despite good initial response rates, acquired chemoresistance is a critical hurdle in the treatment of cancer and is responsible for relapse and leads to an overall survival rate of about 30 %. One major mode by which cancer cells evade chemotherapy is by an acquired ability to suppress intrinsic pathway of apoptosis [1]. The last group consists of the BH3-only members (Bad, Bid, Bim, Noxa, Puma...) those possess only the BH3 domain and act as sensors of cellular stress. They initiate apoptosis by either blocking the activity of anti-apoptotic members or directly activating pro-apoptotic members, which is mediated via interaction of the BH3 domain of one protein with the hydrophobic pocket of another [2]

Methods

Results

Conclusion