Activated H-Ras regulates hematopoietic cell survival by modulating Survivin q Seiji Fukuda, Louis M. Pelus * Department of Microbiology and Immunology, Walther Oncology Center, Indiana University School of Medicine, and the Walther Cancer Institute, Indianapolis, IN 46202, USA Received 16 August 2004 Abstract Survivin expression and Ras activation are regulated by hematopoietic growth factors. We investigated whether activated Ras could circumvent growth factor-regulated Survivin expression and if a Ras/Survivin axis mediates growth factor independent sur- vival and proliferation in hematopoietic cells. Survivin expression is up-regulated by IL-3 in Ba/F3 and CD34 + cells and inhibited by the Ras inhibitor, farnesylthiosalicylic acid. Over-expression of constitutively activated H-Ras (CA-Ras) in Ba/F3 cells blocked down-modulation of Survivin expression, G 0 /G 1 arrest, and apoptosis induced by IL-3 withdrawal, while dominant-negative (DN) H-Ras down-regulated Survivin. Survivin disruption by DN T34A Survivin blocked CA-Ras-induced IL-3-independent cell survival and proliferation; however, it did not affect CA-Ras-mediated enhancement of S-phase, indicating that the anti-apoptotic activity of CA-Ras is Survivin dependent while its S-phase enhancing effect is not. These results indicate that CA-Ras modulates Survivin expression independent of hematopoietic growth factors and that a CA-Ras/Survivin axis regulates survival and prolifer- ation of transformed hematopoietic cells. Ó 2004 Elsevier Inc. All rights reserved. Keywords: Survivin; Ras; Leukemia; Apoptosis; Cell cycle Hematopoietic growth factors maintain normal blood cell production by coordinately regulating intra- cellular signaling pathways that control cell prolifera- tion, cell cycle progression, and apoptosis [1,2]. We previously reported that hematopoietic growth factors selectively up-regulate Survivin expression in normal CD34 + cells, coincident with cell cycle progression and reduced apoptosis [3–5]. In contrast, growth factor with- drawal reduces Survivin expression and induces cell cy- cle arrest, activation of effector caspases, and apoptosis [3,6]. These findings suggest that hematopoietic growth factors strictly regulate normal hematopoietic cell sur- vival and proliferation by regulating Survivin expression and caspase activation. Transformed hematopoietic cells demonstrate robust proliferation, resistance to apoptosis, and escape from normal growth factor control [7,8]. A number of mole- cules are believed to be involved in these processes dur- ing malignant cell development [7,9]. The inhibitor of apoptosis protein, Survivin, is over-expressed in acute myeloid leukemia (AML) cells [10,11], where it blocks apoptosis [12,13] by inhibiting caspase-3 activation [14–17] and accelerates cell cycle progression [4,18,19]. In AML cells, GM-CSF can regulate Survivin expres- sion [11] and constitutively activated STAT3 can con- tribute to Survivin over-expression in some lymphoma cells [20]. However, the mechanism through which Sur- vivin expression is up-regulated in malignant hemato- poietic cells is not understood. 0006-291X/$ - see front matter Ó 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.bbrc.2004.08.149 q Supported by US Public Health Service Grant HL079654 (to L.M.P.) from the National Institutes of Health. * Corresponding author. Fax: +1 317 274 7592. E-mail address: lpelus@iupui.edu (L.M. Pelus). www.elsevier.com/locate/ybbrc Biochemical and Biophysical Research Communications 323 (2004) 636–644 BBRC