title: Expression of activated STAT5 in neoplastic mast cells in systemic mastocytosis: subcellular distribution and role of the transforming oncoprotein KIT D816V.
abstract: Recent data suggest that the signal transducer and activator of transcription (STAT)5 contributes to differentiation and growth of mast cells. It has also been described that constitutively phosphorylated STAT5 (pSTAT5) plays a pro-oncogenic role in various myeloid neoplasms. We examined the expression of pSTAT5 in neoplastic mast cells in systemic mastocytosis and asked whether the disease-related oncoprotein KIT D816V is involved in STAT5 activation. As assessed by immunohistochemistry using the anti-pSTAT5 antibody AX1, neoplastic mast cells were found to display pSTAT5 in all SM patients examined (n = 40). Expression of pSTAT5 was also demonstrable in the KIT D816V-positive mast cell leukemia cell line HMC-1. Using various staining-protocols, pSTAT5 was found to be located in both the cytoplasmic and nuclear compartment of mast cells. To define the functional role of KIT D816V in STAT5-activation, Ba/F3 cells with doxycycline-inducible expression of KIT D816V were used. In these cells, induction of KIT D816V resulted in an increased expression of pSTAT5 without substantial increase in total STAT5. Moreover, the KIT D816V-targeting kinase-inhibitor PKC412 was found to counteract expression of pSTAT5 in HMC-1 cells as well as doxycycline-induced expression of pSTAT5 in Ba/F3 cells. Finally, a dominant negative STAT5-construct was found to inhibit growth of HMC-1 cells. Together, our data show that neoplastic mast cells express cytoplasmic and nuclear pSTAT5, that KIT D816V promotes STAT5-activation, and that STAT5-activation contributes to growth of neoplastic mast cells.
authors.affiliation: Department of Internal Medicine I, Medical University of Vienna, Vienna, Austria.
authors.forename: Christian
authors.initials: C
authors.lastname: Baumgartner
authors.forename: Sabine
authors.initials: S
authors.lastname: Cerny-Reiterer
authors.forename: Karoline
authors.initials: K
authors.lastname: Sonneck
authors.forename: Matthias
authors.initials: M
authors.lastname: Mayerhofer
authors.forename: Karoline V
authors.initials: KV
authors.lastname: Gleixner
authors.forename: Richard
authors.initials: R
authors.lastname: Fritz
authors.forename: Marc
authors.initials: M
authors.lastname: Kerenyi
authors.forename: Cedric
authors.initials: C
authors.lastname: Boudot
authors.forename: Fabrice
authors.initials: F
authors.lastname: Gouilleux
authors.forename: Jan-Wilhelm
authors.initials: JW
authors.lastname: Kornfeld
authors.forename: Christian
authors.initials: C
authors.lastname: Sillaber
authors.forename: Richard
authors.initials: R
authors.lastname: Moriggl
authors.forename: Peter
authors.initials: P
authors.lastname: Valent
mesh_terms: D000328:Adult; D000368:Aged; D015153:Blotting, Western; D002469:Cell Separation; D024202:Electrophoretic Mobility Shift Assay; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008407:Mast Cells / Q000378:metabolism*; D034721:Mastocytosis, Systemic / Q000235:genetics* / Q000378:metabolism*; D008875:Middle Aged; D009154:Mutation; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics*; D050799:STAT5 Transcription Factor / Q000378:metabolism*
chemical_list: D050799:STAT5 Transcription Factor; D019009:Proto-Oncogene Proteins c-kit