Loss of enhancer of zeste homologue 2 (EZH2) at tumor invasion front is correlated with higher aggressiveness in colorectal cancer cells

Julian Böhm,Aylin Caliskan,Tilman T Rau,Benardina Ndreshkjana,Katharina Erlenbach-Wünsch,Roland Croner,Julienne Kathrin Muenzner,Carol Immanuel Geppert,Arndt Hartmann,Adriana Vial Roehe,Susanne Merkel,Regine Schneider-Stock

doi:10.1007/s00432-019-02977-1

Abstract

PurposeEnhancer of zeste homolog 2 (EZH2) is associated with epigenetic gene silencing and aggressiveness in many tumor types. However, the prognostic impact of high EZH2 expression is controversially discussed for colorectal cancer. For this reason, we immunohistochemically analyzed EZH2 expression in 105 specimens from colon cancer patients separately for tumor center and invasion front.MethodsAll sections from tissue microarrays were evaluated manually and digitally using Definiens Tissue Studio software (TSS). To mirror-image the EZH2 status at the tumor invasion front, we treated HCT116 colon cancer cells with the EZH2 inhibitor 3-Deazaneplanocin A (DZNep) and studied the growth of in ovo xenografts in the chorioallantoic membrane (CAM) assay.ResultsWe showed a significant decrease in EZH2 expression and the repressive H3K27me3 code at the tumor invasion front as supported by the TSS-constructed heatmaps. Loss of EZH2 at tumor invasion front, but not in tumor center was correlated with unfavorable prognosis and more advanced tumor stages. The observed cell cycle arrest in vitro and in vivo was associated with higher tumor aggressiveness. Xenografts formed by DZNep-treated HCT116 cells showed loosely packed tumor masses, infiltrative growth into the CAM, and high vessel density.ConclusionThe differences in EZH2 expression between tumor center and invasion front as well as different scoring and cutoff values can most likely explain controversial literature data concerning the prognostic value of EZH2. Epigenetic therapies using EZH2 inhibitors have to be carefully evaluated for each specific tumor type, since alterations in cell differentiation might lead to unfavorable results.

Highlights

As the catalytic subunit of the polycomb repressive complex (PRC2), histone methyltransferase Enhancer of zeste homolog 2 (EZH2), preferentially methylates lysine 27 on histone 3 (H3K27) and is associated with epigenetic gene silencing (Simon and Lange 2008; Kuzmichev et al 2002; Margueron and Reinberg 2011)
A high EZH2 expression has been linked to advanced disease and worse prognosis
2 recent meta-analyses concerning EZH2 expression in colorectal cancer (CRC) tumors, one including 8 studies and more than 1059 CRC patients, while the other one comprised 10 studies with 1461 CRC patients, showed that EZH2 overexpression indicates a better prognosis in CRC and that EZH2 is not an indicator of poor prognosis, respectively (Vilorio-Marqués et al 2017)

Summary

Introduction

As the catalytic subunit of the polycomb repressive complex (PRC2), histone methyltransferase EZH2, preferentially methylates lysine 27 on histone 3 (H3K27) and is associated with epigenetic gene silencing (Simon and Lange 2008; Kuzmichev et al 2002; Margueron and Reinberg 2011). Extended author information available on the last page of the article involved in metastasis by modulating tumor angiogenesis and the epithelial-to-mesenchymal transition, a process by which disseminating tumor cells acquire mesenchymal characteristics to migrate through the extracellular matrix (Simon and Lange 2008; Kim and Roberts 2016; Crea et al 2012). Fussbroich et al investigated the expression of EZH2 in colon cancer and adenomas immunohistochemically and reported a significant increase in EZH2 expression in CRC, especially in

Objectives

Methods

Results

Conclusion