PRH/HHex inhibits the migration of breast and prostate epithelial cells through direct transcriptional regulation of Endoglin

R M Kershaw,Y H Siddiqui,P-S Jayaraman,K Gaston,D Roberts

doi:10.1038/onc.2013.496

Abstract

PRH/HHex (proline-rich homeodomain protein) is a transcription factor that controls cell proliferation and cell differentiation in a variety of tissues. Aberrant subcellular localisation of PRH is associated with breast cancer and thyroid cancer. Further, in blast crisis chronic myeloid leukaemia, and a subset of acute myeloid leukaemias, PRH is aberrantly localised and its activity is downregulated. Here we show that PRH is involved in the regulation of cell migration and cancer cell invasion. We show for the first time that PRH is expressed in prostate cells and that a decrease in PRH protein levels increases the migration of normal prostate epithelial cells. We show that a decrease in PRH protein levels also increases the migration of normal breast epithelial cells. Conversely, PRH overexpression inhibits cell migration and cell invasion by PC3 and DU145 prostate cancer cells and MDA-MB-231 breast cancer cells. Previous work has shown that the transforming growth factor-β co-receptor Endoglin inhibits the migration of prostate and breast cancer cells. Here we show that PRH can bind to the Endoglin promoter in immortalised prostate and breast cells. PRH overexpression in these cells results in increased Endoglin protein expression, whereas PRH knockdown results in decreased Endoglin protein expression. Moreover, we demonstrate that Endoglin overexpression abrogates the increased migration shown by PRH knockdown cells. Our data suggest that PRH controls the migration of multiple epithelial cell lineages in part at least through the direct transcriptional regulation of Endoglin. We discuss these results in terms of the functions of PRH in normal cells and the mislocalisation of PRH seen in multiple cancer cell types.

Highlights

The transcription factor PRH is essential for formation of the vertebrate body axis and the development of most organs including the heart, thyroid, pancreas, vasculature and haematopoietic compartment.[1]
Our findings suggest that in prostate cancer cells and breast cancer cells the regulation of Endoglin by PRH may be attenuated resulting in increased cell migration and cell invasion
To determine whether PRH has an important role in these cells, we performed a PRH knockdown experiment using specific short hairpin RNAs

Summary

Introduction

The transcription factor PRH (proline-rich homeodomain/HHex) is essential for formation of the vertebrate body axis and the development of most organs including the heart, thyroid, pancreas, vasculature and haematopoietic compartment.[1]. Aberrant subcellular localisation of PRH with loss of nuclear PRH is associated with blast crisis chronic myeloid leukaemia and some subtypes of acute myeloid leukaemia.[12] Further, in one human acute myeloid leukaemia the only characterised genetic change is a fusion of the prh gene with the nucleoporin gene Nup[98] and this is thought to decrease the activity of endogenous PRH.[11] We have shown that in a chronic myeloid leukaemia cell line, BCR-ABL activity indirectly results in the downregulation of PRH transcriptional repression activity and the de-repression of several PRH target genes including Vegfa, Vegfr-1 and Vegfr-2.13 The repression of these genes in chronic myeloid leukaemia K562 cells by PRH results in decreased vascular endothelial growth factor (VEGF) autocrine signalling and decreased cell survival.[13]

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Conclusion