Genetic and pharmacologic evidence implicating the p85α, but not p85β, regulatory subunit of PI3K and Rac2 GTPase in regulating oncogenic KIT-induced transformation in acute myeloid leukemia and systemic mastocytosis

Veerendra Munugalavadla, Emily C. Sims, Jovencio Borneo, Rebecca J. Chan, Reuben Kapur

Research output: Contribution to journalArticle

28 Scopus citations


Oncogenic activation loop KIT mutations are observed in acute myeloid leukemia (AML) and systemic mastocytosis (SM); however, unlike the KIT juxtamembrane mutants, the activation loop mutants are insensitive to imatinib mesylate. Furthermore, as prior studies primarily used heterologous cell lines, the molecular mechanism(s) underlying oncogenic KIT-induced transformation in primary cells is poorly understood. We demonstrate that expression of KITD814V in primary hematopoietic stem/progenitor cells (HSC/Ps) and mast cell progenitors (MCps) induces constitutive KIT autophosphorylation, supports ligand-independent hyperproliferation, and promotes promiscuous cooperation with multiple cytokines. Genetic disruption of p85α, the regulatory subunit of class IA lipid kinase phosphoinositol-3-kinase (PI3K), but not of p85β, or genetic disruption of the hematopoietic cellspecific Rho GTPase, Rac2, normalizes KITD814V-induced ligand-independent hyperproliferation. Additionally, deficiency of p85α or Rac2 corrects the promiscuous hyperproliferation observed in response to multiple cytokines in both KITD814V-expressing HSC/Ps and MCps. Treatment of KITD814V-expressing HSC/Ps with a Rac inhibitor (NC23766) or with rapamycin showed a dose-dependent suppression in ligand-independent growth. Taken together, our results identify p85 and Rac2 as potential novel therapeutic targets for the treatment of KITD814V-bearing AML and SM.

Original languageEnglish (US)
Pages (from-to)1612-1620
Number of pages9
Issue number5
StatePublished - Sep 1 2007


ASJC Scopus subject areas

  • Biochemistry
  • Immunology
  • Hematology
  • Cell Biology

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