Dysregulated expression of Fau and MELK is associated with poor prognosis in breast cancer.
BACKGROUND
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.
Pickard
Mark R
MR
Institute for Science and Technology in Medicine and School of Life Sciences, Keele University, Huxley Building, Keele ST5 5BG, UK. m.r.pickard@biol.keele.ac.uk
Green
Andrew R
AR
Ellis
Ian O
IO
Caldas
Carlos
C
Hedge
Vanessa L
VL
Mourtada-Maarabouni
Mirna
M
Williams
Gwyn T
GT
D000230:Adenocarcinoma / Q000235:genetics* / Q000401:mortality; D017209:Apoptosis / Q000235:genetics / Q000528:radiation effects; D001943:Breast Neoplasms / Q000235:genetics* / Q000401:mortality; D045744:Cell Line, Tumor / Q000166:cytology / Q000528:radiation effects; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D055785:Gene Knockdown Techniques; D056726:Genetic Association Studies; D006801:Humans; D053208:Kaplan-Meier Estimate; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D011379:Prognosis; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000494:pharmacology; D012269:Ribosomal Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D014410:Tumor Stem Cell Assay; D014466:Ultraviolet Rays
C428448:BCL2L14 protein, human; D009363:Neoplasm Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D012269:Ribosomal Proteins; C076845:FAU protein, human; C484610:MELK protein, human; D017346:Protein Serine-Threonine Kinases