title: KIT GNNK splice variants: expression in systemic mastocytosis and influence on the activating potential of the D816V mutation in mast cells.
abstract: Stem cell factor-dependent KIT activation is an essential process for mast cell homeostasis. The two major splice variants of KIT differ by the presence or absence of four amino acids (GNNK) at the juxta-membrane region of the extracellular domain. We hypothesized that the expression pattern of these variants differs in systemic mastocytosis and that transcripts containing the KIT D816V mutation segregate preferentially to one GNNK variant. A quantitative real-time PCR assay to assess GNNK(-) and GNNK(+) transcripts from bone marrow mononuclear cells was developed. The GNNK(-)/GNNK(+) copy number ratio showed a trend toward a positive correlation with the percentage of neoplastic mast cell involvement, and KIT D816V containing transcripts displayed a significantly elevated GNNK(-)/GNNK(+) copy number ratio. Relative expression of only the GNNK(-) variant correlated with increasing percentage of neoplastic mast cell involvement. A mast cell transfection system revealed that the GNNK(-) isoform of wild type KIT was associated with increased granule formation, histamine content, and growth. When accompanying the KIT D816V mutation, the GNNK(-) isoform enhanced cytokine-free metabolism and moderately reduced sensitivity to the tyrosine kinase inhibitor, PKC412. These data suggest that neoplastic mast cells favor a GNNK(-) variant predominance, which in turn enhances the activating potential of the KIT D816V mutation and thus could influence therapeutic sensitivity in systemic mastocytosis.
authors.affiliation: Mast Cell Biology Section, Laboratory of Allergic Diseases, Bethesda, MD, USA.
authors.forename: Eunice Ching
authors.initials: EC
authors.lastname: Chan
authors.forename: Yun
authors.initials: Y
authors.lastname: Bai
authors.forename: Geethani
authors.initials: G
authors.lastname: Bandara
authors.forename: Olga
authors.initials: O
authors.lastname: Simakova
authors.forename: Erica
authors.initials: E
authors.lastname: Brittain
authors.forename: Linda
authors.initials: L
authors.lastname: Scott
authors.forename: Kimberly D
authors.initials: KD
authors.lastname: Dyer
authors.forename: Amy D
authors.initials: AD
authors.lastname: Klion
authors.forename: Irina
authors.initials: I
authors.lastname: Maric
authors.forename: Alasdair M
authors.initials: AM
authors.lastname: Gilfillan
authors.forename: Dean D
authors.initials: DD
authors.lastname: Metcalfe
authors.forename: Todd M
authors.initials: TM
authors.lastname: Wilson
mesh_terms: D000328:Adult; D000368:Aged; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D004789:Enzyme Activation / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008297:Male; D008407:Mast Cells / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D034721:Mastocytosis, Systemic / Q000201:enzymology / Q000235:genetics* / Q000503:physiopathology*; D008875:Middle Aged; D009154:Mutation; D020033:Protein Isoforms / Q000235:genetics; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics* / Q000378:metabolism; D019311:Staurosporine / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D020033:Protein Isoforms; D019009:Proto-Oncogene Proteins c-kit; D051057:Proto-Oncogene Proteins c-akt; D019311:Staurosporine; C059539:midostaurin