Network analysis of genetic pathways active in the IF cohort shows a checkpoint arrest at G1/S transition. To identify biologic function and interactions in the differentially expressed genes in the 116-member genomic classifier, we used Ingenuity Systems software to map gene networks and identifying potentially dysregulated pathways in the IF T-ALL cohort. Network analysis shows that TGFβ1, LYN, and LATS2 interact with and down-regulate CDC2 and CDC25 to result in a arrest of cell cycle progression at the G1/S checkpoint. Absent from this network analysis are genes governing drug metabolism (p450 enzymes) or apoptotic pathways. Each gene node represents a functional class, for which an upward-pointing triangle indicates a phosphatase, a downward-pointing triangle indicates a kinase, a vertical rectangle indicates a G-protein–coupled receptor, a square indicates a cytokine, and a circle indicates genes having other functions, to include surface receptors and adhesive ligands. Nodes that are colored in red indicate relative up-regulation, and nodes in green indicate relative down-regulation.