Basic Study
Copyright ©The Author(s) 2017. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Jun 14, 2017; 23(22): 4007-4015
Published online Jun 14, 2017. doi: 10.3748/wjg.v23.i22.4007
Bcl-2 degradation is an additional pro-apoptotic effect of polo-like kinase inhibition in cholangiocarcinoma cells
Svenja Sydor, Sami Jafoui, Lena Wingerter, Sandra Swoboda, Joachim C Mertens, Guido Gerken, Ali Canbay, Andreas Paul, Christian D Fingas
Svenja Sydor, Sami Jafoui, Lena Wingerter, Guido Gerken, Ali Canbay, Department of Gastroenterology and Hepatology, University Hospital Essen, University Duisburg-Essen, 45122 Essen, Germany
Sandra Swoboda, Andreas Paul, Christian D Fingas, Department for General, Visceral and Transplantation Surgery, University Hospital Essen, University Duisburg-Essen, 45122 Essen, Germany
Joachim C Mertens, Division of Gastroenterology and Hepatology, University Hospital Zurich, 8091 Zurich, Switzerland
Author contributions: Sydor S contributed to acquisition, analysis and interpretation of data, statistical analysis, drafting of the manuscript; Jafoui S contributed to acquisition and analysis of data; Wingerter L contributed to acquisition and analysis of data; Swoboda S contributed to acquisition and analysis of data; Mertens JC contributed to critical revision of the manuscript for important intellectual content, technical support; Gerken G contributed to obtained funding, critical revision of the manuscript for important intellectual content; Canbay A contributed to obtained funding, critical revision of the manuscript for important intellectual content; Paul A contributed to obtained funding, critical revision of the manuscript for important intellectual content; Fingas CD contributed to study concept and design.
Supported by DFG/German Research Foundation, No. FI 1630/3-1 and No. IFORES D/107114400 (to CDF).
Institutional review board statement: For this study no human or animal derived material was used. All performed experiments and shown data were assessed by using established cell lines and were performed according to good laboratory practice guidelines. The study was reviewed and approved by the University of Duisburg-Essen Institutional Review Board.
Institutional animal care and use committee statement: For this study we did not perform animal experiments or use experimental material derived from animals. Provision of an institutional animal care and use committee statement is not applicable in this case.
Conflict-of-interest statement: The authors have no conflicts of interest.
Data sharing statement: There are no additional data available.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Christian D Fingas, MD, PhD, Associate Professor, Department for General, Visceral and Transplantation Surgery, University Hospital Essen, University Duisburg-Essen, Hufelandstraße 55, 45122 Essen, Germany. christian.fingas@uk-essen.de
Telephone: +49-201-723 83676 Fax: +49-201-7231131
Received: January 13, 2017
Peer-review started: January 14, 2017
First decision: February 23, 2017
Revised: April 5, 2017
Accepted: May 9, 2017
Article in press: May 9, 2017
Published online: June 14, 2017
Abstract
AIM

To examine the influence on apoptotic mechanisms following inhibition of polo-like kinases as therapeutically approach for cholangiocellular cancer treatment.

METHODS

As most cholangiocarcinomas are chemotherapy-resistant due to mechanisms preventing tumor cell death, we investigated the effect of Cisplatin on cholangiocellular carcinoma (CCA) cell lines KMCH-1 and Mz-Ch-1. Polo-like kinases (PLK) are important regulators of the cell cycle and their inhibition is discussed as a potential therapy while PLK inhibition can regulate apoptotic mediators. Here, cells were treated with PLK inhibitor BI6727 (Volasertib), Cisplatin, and in combination of both compounds. Cell viability was assessed by MTT; apoptosis was measured by DAPI staining and caspase-3/-7 assay. Western blot and qRT-PCR were used to measure expression levels of apoptosis-related molecules Bax and Bcl-2.

RESULTS

The cell viability in the CCA cell lines KMCH-1 and Mz-Ch-1 was reduced in all treatment conditions compared to vehicle-treated cells. Co-treatment with BI6727 and cisplatin could even enhance the cytotoxic effect of cisplatin single treatment. Thus, co-treatment of cisplatin with BI6727 could slightly enhance the cytotoxic effect of the cisplatin in both cell lines whereas there was evidence of increased apoptosis induction solely in Mz-Ch-1 as compared to KMCH-1. Moreover, PLK inhibition decreases protein levels of Bcl-2; an effect that can be reversed by the proteasomal degradation inhibitor MG-132. In contrast, protein levels of Bax were not found to be altered by PLK inhibition. These findings indicate that cytotoxic effects of Cisplatin in Mz-Ch-1 cells can be enhanced by cotreatment with BI6727.

CONCLUSION

In conclusion, BI6727 treatment can sensitize CCA cells to cisplatin-induced apoptosis with proteasomal Bcl-2 degradation as an additional pro-apoptotic effect.

Keywords: Tumor necrosis factor-related apoptosis-inducing ligand, Myeloid cell leukemia-1, Hedgehog pathway, Cisplatin, Chemotherapy resistance

Core tip: This manuscript addresses the timely and topical roles of cell cycle/apoptosis modulating enzymes for the tumor biology of human cholangiocarcinoma. These data suggest that polo-like kinases -Inhibition by BI6727 (volasertib) sensitizes some cholangiocarcinoma cell lines to cisplatin-induced apoptosis. Our findings include an enhanced cytotoxic effect of cisplatin by co-treatment with BI6727 (volasertib) and results in decreased protein expression levels of the anti-apoptotic molecule Bcl-2, which appears to be mediated via proteasomal degradation. Taken together, these data reveal another pro-apoptotic mechanism of polo-like kinase inhibition emphasizing the potential therapeutic benefit of polo-like kinase inhibitors for the treatment of cholangiocarcinoma.