title: Genetic and pharmacologic evidence implicating the p85 alpha, but not p85 beta, regulatory subunit of PI3K and Rac2 GTPase in regulating oncogenic KIT-induced transformation in acute myeloid leukemia and systemic mastocytosis.
abstract: 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 p85 alpha, the regulatory subunit of class IA lipid kinase phosphoinositol-3-kinase (PI3K), but not of p85 beta, or genetic disruption of the hematopoietic cell-specific Rho GTPase, Rac2, normalizes KITD814V-induced ligand-independent hyperproliferation. Additionally, deficiency of p85 alpha 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 alpha and Rac2 as potential novel therapeutic targets for the treatment of KITD814V-bearing AML and SM.
authors.affiliation: Department of Pediatrics, Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
authors.forename: Veerendra
authors.initials: V
authors.lastname: Munugalavadla
authors.forename: Emily C
authors.initials: EC
authors.lastname: Sims
authors.forename: Jovencio
authors.initials: J
authors.lastname: Borneo
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Chan
authors.forename: Reuben
authors.initials: R
authors.lastname: Kapur
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D001549:Benzamides; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic / Q000187:drug effects / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D016207:Cytokines / Q000378:metabolism; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006412:Hematopoietic Stem Cells / Q000201:enzymology / Q000473:pathology; D000068877:Imatinib Mesylate; D015470:Leukemia, Myeloid, Acute / Q000188:drug therapy / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D034721:Mastocytosis, Systemic / Q000188:drug therapy / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D051379:Mice; D018345:Mice, Knockout; D020125:Mutation, Missense; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D010879:Piperazines / Q000494:pharmacology; D021122:Protein Subunits / Q000235:genetics; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics / Q000378:metabolism*; D011743:Pyrimidines / Q000494:pharmacology; D020123:Sirolimus / Q000494:pharmacology; D020744:rac GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000097766:RAC2 GTP-Binding Protein
chemical_list: D000903:Antibiotics, Antineoplastic; D001549:Benzamides; D016207:Cytokines; D004791:Enzyme Inhibitors; D000068877:Imatinib Mesylate; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010879:Piperazines; D021122:Protein Subunits; D019009:Proto-Oncogene Proteins c-kit; D011743:Pyrimidines; D020123:Sirolimus; D020744:rac GTP-Binding Proteins; D000097766:RAC2 GTP-Binding Protein