This Article Full Text Full Text (PDF) Supplementary Data Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Gallagher, J. W. Articles by Jefferson, L. S. Search for Related Content PubMed PubMed Citation Articles by Gallagher, J. W. Articles by Jefferson, L. S.

Reduced Eukaryotic Initiation Factor 2B-Subunit Expression Suppresses the Transformed Phenotype of Cells Overexpressing the Protein

¹ Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania and ² Department of Cell Biology, Harvard Medical School, Boston, Massachusetts

Requests for reprints: Scot R. Kimball, Department of Cellular and Molecular Physiology, The Pennsylvania State College of Medicine, P.O. Box 850, Hershey, PA 17033. Phone: 717-531-8970; Fax: 717-531-7667; E-mail: skimball{at}psu.edu.

Key Words: eIF2B5 • transformation • shRNA • siRNA

Eukaryotic initiation factor 2B (eIF2B), a five-subunit guanine nucleotide exchange factor, plays a key role in the regulation of mRNA translation. Expression of its -subunit is specifically up-regulated in certain conditions associated with increased cell growth. Therefore, the purpose of the present study was to examine the effect of repressing eIF2B expression on growth rate, protein synthesis, and other characteristics of two tumorigenic cell lines that display up-regulated expression of the -subunit. Experiments were designed to compare spontaneously transformed fibroblasts to transformed mouse embryonic fibroblasts infected with a lentivirus containing a short hairpin RNA directed against eIF2B. Cells expressing the short hairpin RNA displayed a reduction in eIF2B abundance to 30% of the value observed in uninfected transformed mouse embryonic fibroblasts, with no change in the expression of any of the other four subunits. The repression of eIF2B expression was accompanied by reductions in guanine nucleotide exchange factor activity and global rates of protein synthesis. Moreover, repressed eIF2B expression led to marked reductions in cell growth rate in culture, colony formation in soft agar, and tumor progression in nude mice. Similar results were obtained in MCF-7 human breast cancer cells in which eIF2B expression was repressed through transient transfection with a small interfering RNA directed against the -subunit. Overall, the results support a role for eIF2B in the regulation of cell growth and suggest that it might represent a therapeutic target for the treatment of human cancer. [Cancer Res 2008;68(21):8752–60]