Gene expression changes following knockdown or overexpression of HHEX/PRH

Breast tumours progress from hyperplasia to ductal carcinoma in situ (DCIS) and invasive breast carcinoma (IBC). PRH/HHEX (Proline Rich Homeodomain/Haematopoietically expressed homeobox) is a transcription factor that displays both tumour suppressor and oncogenic activity in different disease contexts however, the role of PRH in breast cancer is poorly understood. To determine the consequences of PRH loss of function in breast cancer cells we generated inducible PRH depletion in MCF-7 cells. We show that PRH depletion results in increased MCF-7 cell proliferation in part at least due to increased vascular endothelial growth factor signaling. Moreover we demonstrate that PRH depletion increases the formation of breast cancer cells with cancer stem cell-like properties. Finally, and in keeping with these findings, we show that PRH over-expression inhibits the growth of mammary tumours in mice. Collectively these data indicate that PRH plays a tumour suppressive role in the breast and they provide an explanation for the finding that low PRH mRNA levels are associated with a poor prognosis in breast cancer. A 12 array study in which Proline-Rich Homeodomain protein (PRH/HHEX) is either knocked down or overexpressed in MCF7 cells. In the knockdown experiment there are 3 scrambled shRNA control replicates and 3 PRH shRNA replicates. In the overexpression experiment there are 3 empty vector transfected control replicates and 3 PRH transfected overexpression replicates.