Treatment of biliary tract cancer cells with polycomb repressive complex 1 inhibitor PTC-209 reduces putative cancer stem cell population and causes cell cycle arrest

C Mayr; A Wagner; M Beyreis; R Illig; F Berr; M Pichler; P Di Fazio; D Neureiter; T Kiesslich

doi:10.1055/s-0035-1551755

Zeitschrift für Gastroenterologie, Table of Contents

Treatment of biliary tract cancer cells with polycomb repressive complex 1 inhibitor PTC-209 reduces putative cancer stem cell population and causes cell cycle arrest

C Mayr ¹, A Wagner ², M Beyreis ³, R Illig ⁴, F Berr ², M Pichler ⁵, P Di Fazio ⁶, D Neureiter ⁴, T Kiesslich ¹

¹Salzburger Landeskliniken/Paracelsus Medical University, Department of Internal Medicine I/Laboratory for Tumour Biology and Experimental Therapies, Institute of Physiology and Pathophysiology, Salzburg, Austria
²Salzburger Landeskliniken/Paracelsus Medical University, Department of Internal Medicine I, Salzburg, Austria
³Paracelsus Medical University, Laboratory for Tumour Biology and Experimental Therapies, Institute of Physiology and Pathophysiology, Salzburg, Austria
⁴Paracelsus Medical University, Institute of Pathology, Salzburg, Austria
⁵Medical University of Graz (MUG), Division of Oncology, Department of Internal Medicine, Graz, Austria
⁶Philipps-University Marburg, Department of Visceral, Thoracic and Vascular Surge, Marburg, Germany

Abstract

Question:

The polycomb repressive complex 1 (PRC1) is an epigenetic regulator that plays a crucial role in various types of cancer including biliary tract cancer (BTC). BTC is a fatal disease associated with poor outcome. Hence, new therapeutic strategies are needed. Recently, the first small-molecule PRC1 inhibitor called PTC-209 has been developed. In this study, we examined the effect of PTC-209 on eight different BTC cell lines.

Methods:

Expression of PRC1 core components bmi1 and ring1b was measured with quantitative real time reverse transcription PCR. Cytotoxic effects of PTC-209 were evaluated using resazurin cell viability and caspase activity assays. As for cell cycle analysis we performed propidium iodide staining and gene expression analysis using RT2 Profiler PCR Array. Additionally, we measured aldehyde-dehydrogenase (ALDH) activity as a cancer stem cell (CSC) characteristic.

Results:

All eight BTC cell lines expressed the PRC1 core components bmi1 and ring1b at differing levels. Using a dilution series of PTC-209 ranging from 0.04 to 20µM we ascertained that – except for one cell line – the cell viability decreases in a cell line- and dose-dependent manner. Growth curve analysis showed that the cytotoxic effect of PTC-209 was mainly caused by a growth arrest of the cells. Subsequent cell cycle analysis revealed a decrease of cells in the S and 4N phases, respectively, accompanied by an increase of cells in the 2N phase. In line with this, numerous cell cycle-related genes were differentially regulated after PTC-209 treatment. PTC-209 also caused significant reduction of the ALDH-positive putative CSC subpopulation.

Conclusions:

Up to now, there are no published data available that address the effect of PTC-209 on BTC cells. Our data suggest that PTC-209 not only causes cell cycle arrest of BTC cells, but also might target CSC in BTC, making it an attractive drug for subsequent experiments.