ERG Deregulation Induces PIM1 Over-Expression and Aneuploidy in Prostate Epithelial Cells

Vera Magistroni,James Frances Reid,Rocco Piazza,Guido Strada,Manuela Gariboldi,Michela Viltadi,Marco Grasso,Luca Mologni,Stefano Sanselicio,Carlo Gambacorti-Passerini,Giorgio Bovo,Sara Redaelli,Klaus Roemer

doi:10.1371/journal.pone.0028162

Abstract

The ERG gene belongs to the ETS family of transcription factors and has been found to be involved in atypical chromosomal rearrangements in several cancers. To gain insight into the oncogenic activity of ERG, we compared the gene expression profile of NIH-3T3 cells stably expressing the coding regions of the three main ERG oncogenic fusions: TMPRSS2/ERG (tERG), EWS/ERG and FUS/ERG. We found that all three ERG fusions significantly up-regulate PIM1 expression in the NIH-3T3 cell line. PIM1 is a serine/threonine kinase frequently over-expressed in cancers of haematological and epithelial origin. We show here that tERG expression induces PIM1 in the non-malignant prostate cell line RWPE-1, strengthening the relation between tERG and PIM1 up-regulation in the initial stages of prostate carcinogenesis. Silencing of tERG reversed PIM1 induction. A significant association between ERG and PIM1 expression in clinical prostate carcinoma specimens was found, suggesting that such a mechanism may be relevant in vivo. Chromatin Immunoprecipitation experiments showed that tERG directly binds to PIM1 promoter in the RWPE-1 prostate cell line, suggesting that tERG could be a direct regulator of PIM1 expression. The up-regulation of PIM1 induced by tERG over-expression significantly modified Cyclin B1 levels and increased the percentage of aneuploid cells in the RWPE-1 cell line after taxane-based treatment. Here we provide the first evidence for an ERG-mediated PIM1 up-regulation in prostate cells in vitro and in vivo, suggesting a direct effect of ERG transcriptional activity in the alteration of genetic stability.

Highlights

Distinct alterations of the transcription factor ERG, an ETSrelated gene, are observed in a variety of cancers
Chromosomal rearrangements driving the formation of EWS/ ERG and FUS/ERG fusion proteins have been described in a subset of Ewing sarcoma [3,4] and in acute myeloid leukaemia [5,6,7]
We used a homogeneous cellular model to compare the effect of the three main ERG oncogenic forms found in tumoral specimens and derived from non canonical chromosomal rearrangements: truncated ERG protein (tERG), EWS/ERG and FUS/ERG

Summary

Introduction

Distinct alterations of the transcription factor ERG, an ETSrelated gene, are observed in a variety of cancers. The EWS and FUS genes encode for two related RNA-binding proteins that lose their RNA binding domains during translocation with ERG. The resulting fusion proteins maintain the EWS or the FUS transactivator domains (able to bind to RNA polymerase II) and both acquire the ERG-derived DNA-binding domain [8,9,10]. In 2005 the most frequent genetic alteration involving ERG was found in prostate cancer (PCa), where the 59-untrascribed region of the prostate-specific and androgen-responsive TMPRSS2 gene is fused to ERG in approximately 50% of PCa cases [11]. As a consequence of this genetic alteration the TMPRSS2 promoter region determines the inappropriate and androgen-driven expression of ERG in prostate cells. In the most common rearrangement (T1/E4), a truncated ERG protein (tERG) that maintains its ERG DNA-binding domain is expressed. Since the first three exons are lost during rearrangement, an alternative translation initiation site from an internal ATG codon is used to translate the fusion transcript [13]

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Results

Conclusion