Research article

Dysregulated expression of Fau and MELK is associated with poor prognosis in breast cancer

Mark R Pickard¹ , Andrew R Green² , Ian O Ellis² , Carlos Caldas³ , Vanessa L Hedge¹ , Mirna Mourtada-Maarabouni¹ and Gwyn T Williams¹

¹  Institute for Science and Technology in Medicine and School of Life Sciences, Keele University, Huxley Building, Keele ST5 5BG, UK

²  Division of Pathology, School of Molecular Medical Sciences, University of Nottingham and Nottingham University Hospitals, Derby Road, Nottingham NG7 2UH, UK

³  Cancer Research UK Cambridge Research Institute and Department of Oncology, University of Cambridge, Hills Road, Cambridge CB2 0RE, UK

author email corresponding author email

Breast Cancer Research 2009, 11:R60doi:10.1186/bcr2350

Published:	11 August 2009

Abstract

Introduction

Programmed cell death through apoptosis plays an essential role in the hormone-regulated physiological turnover of mammary tissue. Failure of this active gene-dependent process is central both to the development of breast cancer and to the appearance of the therapy-resistant cancer cells that produce clinical relapse. Functional expression cloning in two independent laboratories has identified Finkel–Biskis–Reilly murine sarcoma virus-associated ubiquitously expressed gene (Fau) as a novel apoptosis regulator and candidate tumour suppressor. Fau modifies apoptosis-controller Bcl-G, which is also a key target for candidate oncoprotein maternal embryonic leucine zipper kinase (MELK).

Methods

We have used RNA interference to downregulate Fau and Bcl-G expression, both simultaneously and independently, in breast cancer cells in vitro to determine the importance of their roles in apoptosis. Expression of Fau, Bcl-G and MELK was measured by quantitative RT-PCR in breast cancer tissue and in matched breast epithelial tissue from the same patients. Expression data of these genes obtained using microarrays from a separate group of patients were related to patient survival in Kaplan–Meier analyses.

Results

siRNA-mediated downregulation of either Fau or Bcl-G expression inhibited apoptosis, and the inhibition produced by combining the two siRNAs was consistent with control of Bcl-G by Fau. Fau expression is significantly reduced in breast cancer tissue and this reduction is associated with poor patient survival, as predicted for a candidate breast cancer tumour suppressor. In addition, MELK expression is increased in breast cancer tissue and this increase is also associated with poor patient survival, as predicted for a candidate oncogene. Bcl-G expression is reduced in breast cancer tissue but decreased Bcl-G expression showed no correlation with survival, indicating that the most important factors controlling Bcl-G activity are post-translational modification (by Fau and MELK) rather than the rate of transcription of Bcl-G itself.

Conclusions

The combination of in vitro functional studies with the analysis of gene expression in clinical breast cancer samples indicates that three functionally interconnected genes, Fau, Bcl-G and MELK, are crucially important in breast cancer and identifies them as attractive targets for improvements in breast cancer risk prediction, prognosis and therapy.