Phosphoinositide 3-kinase signaling is essential for ABL oncogene-mediated transformation of B-lineage cells

BCR-ABL and v-ABL are oncogenic forms of the Abl tyrosine kinase that can cause leukemias in mice and humans. ABL oncogenes trigger multiple signaling pathways whose contribution to transformation varies among cell types. Activation of phosphoinositide 3-kinase (P13K) is essential for ABL-dependent proliferation and survival in some cell types, and global P13K inhibitors can enhance the antileukemia effects of the Abl kinase inhibitor imatinib. Although a significant fraction of BCR-ABL-induced human leukemias are of B-cell origin, little is known about P13K signaling mechanisms in B-lineage cells transformed by ABL oncogenes. Here we show that activation of class I-A P13K and downstream inactivation of FOXO transcription factors are essential for survival of murine pro/pre-B cells transformed by v-ABL or BCR-ABL. In addition, analysis of mice lacking individual P13K genes indicates that products of the Pik3r1 gene contribute to transformation efficiency by BCR-ABL. These findings establish a role for P13K signaling in B-lineage transformation by ABL oncogenes. (C) 2004 by The American Society of Hematology.