**5. Survivin modulates gene expression in LSC that connects through an EGFR signaling pathway**

Functional annotation analysis indicates that genes related with dorso-ventral axis formation or epidermal growth factor receptor signaling pathway (EGFR) are significantly enriched in the shared genes associated with LSC and Survivin signaling in the KEGG database (http://www.genome.jp/kegg/) (P<0.03). Similarly, genes associated with regulation of EGFR signaling pathway are enriched in the Gene Ontology database (P<0.02). Our analysis shows that molecules shared by LSC and Survivin signaling are mapped on a functional signaling network that connects through the EGFR pathway (Figure 4). EGFR signaling

Fig. 4. Genes regulated by Survivin in ITD-Flt3+ KSL cells and deregulated in LSC are mapped on a functional signaling network associated with the epidermal growth factor receptor signaling pathway. Epidermal growth factor receptor signaling pathway (EGFR) is significantly enriched in the shared genes associated with LSC and Survivin signaling by pathway enrichment analysis in KEGG and Gene Ontology databases. Our analysis shows that 13 molecules shared by LSC and Survivin signaling are mapped on a functional signaling network associated with EGFR. The network was created based on the KEGG database using Cytoscape software. Gray and black circle represents down regulation and up regulation by Survivin gene deletion, respectively. The hatched circle shows EGFR.

activates signaling cascades involved in cell proliferation, such as Src, Sos and MAP-kinases and is known to be dysregulated in a number of solid tumors (Alvarez et al., 2010; Harris & McCormick, 2010). These findings suggest a potential role of EGFR signaling downstream of Survivin in AML stem cells, despite the fact that EGFR is not usually up regulated in AML cells (Hahn et al., 2009). However, recent studies indicate an anti-neoplastic effect of an EGFR inhibitor in AML via off-target effects (Boehrer et al., 2008; Hahn et al., 2009). Thus, our data would support EGFR signaling as a candidate pathway for treatment of patients with AML, even though the number of molecules detected that associates with EGFR signaling is small.
