XIAP Antagonist Embelin Inhibited Proliferation of Cholangiocarcinoma Cells

Authors

Cody J. Wehrkamp, University of Nebraska Medical Center
Ashley R. Gutwein, University of Nebraska Medical Center
Sathish Kumar Natarajan, University of Nebraska - LincolnFollow
Mary Anne Phillippi, University of Nebraska Medical Center
Justin L. Mott, University of Nebraska Medical Center

Document Type

Article

Date of this Version

2014

Citation

Wehrkamp CJ, Gutwein AR, Natarajan SK, Phillippi MA, Mott JL (2014) XIAP Antagonist Embelin Inhibited Proliferation of Cholangiocarcinoma Cells. PLoS ONE 9(3): e90238.

Comments

Copyright 2014 Wehrkamp et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License

Abstract

Cholangiocarcinoma cells are dependent on antiapoptotic signaling for survival and resistance to death stimuli. Recent mechanistic studies have revealed that increased cellular expression of the E3 ubiquitin-protein ligase X-linked inhibitor of apoptosis (XIAP) impairs TRAIL- and chemotherapy-induced cytotoxicity, promoting survival of cholangiocarcinoma cells. This study was undertaken to determine if pharmacologic antagonism of XIAP protein was sufficient to sensitize cholangiocarcinoma cells to cell death. We employed malignant cholangiocarcinoma cell lines and used embelin to antagonize XIAP protein. Embelin treatment resulted in decreased XIAP protein levels by 8 hours of treatment with maximal effect at 16 hours in KMCH and Mz-ChA-1 cells. Assessment of nuclear morphology demonstrated a concentrationdependent increase in nuclear staining. Interestingly, embelin induced nuclear morphology changes as a single agent, independent of the addition of TNF-related apoptosis inducing ligand (TRAIL). However, caspase activity assays revealed that increasing embelin concentrations resulted in slight inhibition of caspase activity, not activation. In addition, the use of a pan-caspase inhibitor did not prevent nuclear morphology changes. Finally, embelin treatment of cholangiocarcinoma cells did not induce DNA fragmentation or PARP cleavage. Apoptosis does not appear to contribute to the effects of embelin on cholangiocarcinoma cells. Instead, embelin caused inhibition of cell proliferation and cell cycle analysis indicated that embelin increased the number of cells in S and G2/M phase. Our results demonstrate that embelin decreased proliferation in cholangiocarcinoma cell lines. Embelin treatment resulted in decreased XIAP protein expression, but did not induce or enhance apoptosis. Thus, in cholangiocarcinoma cells the mechanism of action of embelin may not be dependent on apoptosis.