1. ¹Department of Oncology, Lombardi Comprehensive Cancer Center/Georgetown University, Washington, DC, USA
2. ²Department of Radiation Oncology, Long Island Jewish Medical Center, The Long Island Campus for the Albert Einstein College of Medicine, New York, NY, USA
3. ³Department of Neurooncology, The Kennedy Krieger Institute/Johns Hopkins University School of Medicine, Baltimore, MD, USA

Correspondence: Dr EM Rosen, Department of Oncology, Lombardi Comprehensive Cancer Center/Georgetown University, 3970 Reservoir Road, NW, Box 571469, Washington, DC 20057-1469, USA. E-mail: emr36@georgetown.edu

Received 15 August 2005; Revised 1 August 2006; Accepted 1 August 2006; Published online 13 November 2006.

Abstract

The cytokine scatter factor (SF) (hepatocyte growth factor) transduces various biologic actions, including cell motility, invasion, angiogenesis and apoptosis inhibition. The latter is relevant to understanding the role of SF in promoting tumor cell survival in different contexts, for example, detachment from basement membrane, growth in metastatic sites and responses to chemo- and radiotherapy. Previously, we showed that SF protects cells against apoptosis owing to DNA damage, by a mechanism involving phosphoinositol-3-kinase/c-Akt signaling. Here, we used DNA microarray assays to identify c-Akt-regulated genes that might contribute to cell protection. DU-145 human prostate cancer cells were transfecteda dominant-negative mutant Akt, treatedSF and analysed for gene expression using Affymetrix arrays. These studies identified SF-regulated genes for which induction was c-Akt-dependent vs -independent. Selected microarray findings were confirmed by semiquantitative and quantitative reverse transcription–polymerase chain reaction. We tested the contribution of four SF-inducible/c-Akt-dependent genes (AMPD3, EPHB2, MX1 and WNT4) to protection against adriamycin (a DNA topoisomerase II inhibitor) using RNA interference. Knockdown of each gene except EPHB2 caused a small but significant reduction in the SF cell protection. The lack of effect of EPHB2 knockdown may be due to the fact that DU-145 cells contain a single-mutant EPHB2 allele. A combination of three small interfering RNAs blocked most of the protection by SF in both DU-145 and T47D cells. These findings identify novel c-Akt-regulated genes, some of which contribute to SF-mediated cytoprotection.