Characterizing ERG-Mediated Transcriptional Reprogramming of Prostatic Epithelial Cells towards a Cancer Stem Cell Phenotype


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Manju Sharma1,Yubin Guo2,Robert Bell2,Michael Cox2
1Vancouver Prostate centre,2Vancouver Prostate Centre

Abstract

Background

 ERG expression commonly occurs in prostate cancer (PCa). While often linked to poor prognosis, how ERG might mechanistically promote transformation remains to be elucidated.

Method

ERG-expressing RWPE1 prostatic epithelial cells (ERG-RWPE1) were constructed to test whether ERG transformation is caused by specific transcriptional profile changes. Microarray analysis of ERG-RWPE1 cells demonstrated up-regulation transcription of stem cell (SC)-related genes. Expression of the SC markers PROM1, c-KIT and CD33 were confirmed at the protein level by FACS and immunofluorescence. The transcriptional reprogramming events related to SC-like capacity were confirmed at mRNA in ERG-RWPE-1 attached and spheroid cultures.

Results

ERG-RWPE1 cells form self-renewable spheroids when cultured in non-adherent SC media. Spheroids uniformly express PROM1, c-KIT and CD33 and when re-plated in adherent conditions, re-establish the SC marker expression pattern of the parental adherent cultures. Transcript analysis of ERG-RWPE-1 spheroid cultures also revealed activation of transcriptional reprogramming events related to acquisition of SC-like capacity, including up-regulated expression of a panel of “Yamanaka-related” SC genes (OCT3/4, SOX2, MYC and KLF4), epigenetic control (PRC1, PRC2 and Homeobox C family genes) and genes belonging to DNA methyltransferase, long noncoding RNA and hypoxia pathways.

Conclusion

RWPE1–ERG cells exhibit up regulated expression of SC genes. ERG induces the formation of self-renewable prostaspheres that exhibit enriched expression of membrane SC markers including (PROM1, c-KIT and CD33). Prostaspheres and attached cells have different gene expression in the family groups of Transcription Factors (Yamanaka Factors), PRC1, PRC2, Homeobox C family, DNA Methyltransferase and long non-coding RNA. Prostaspheres functional groups rank Pluripotency > Maintenance > Differentiation. The genes of the Family groups are interconnected and form a complex network of interactions. This system is a useful model to interrogate the molecular mechanisms of transformation and control of cancer SC leading to the design of new therapies for prostate cancer.