title: SOCS1 cooperates with FLT3-ITD in the development of myeloproliferative disease by promoting the escape from external cytokine control.
abstract: Activating mutations in the receptor tyrosine kinase FLT3 are frequently found in acute myelogenous leukemia patients and confer poor clinical prognosis. It is unclear how leukemic blasts escape cytokine control that regulates normal hematopoiesis. We have recently demonstrated that FLT3-internal tandem duplication (ITD), when localized to the biosynthetic compartment, aberrantly activates STAT5. Here, we show that one of the target genes induced by STAT5 is suppressor of cytokine signaling (SOCS)1-a surprising finding for a known tumor suppressor. Although SOCS1 expression in murine bone marrow severely impaired cytokine-induced colony growth, it failed to inhibit FLT3-ITD-supported colony growth, indicating resistance of FLT3-ITD to SOCS1. In addition, SOCS1 coexpression did not affect FLT3-ITD-mediated signaling or proliferation. Importantly, SOCS1 coexpression inhibited interferon-α and interferon-γ signaling and protected FLT3-ITD hematopoietic cells from interferon-mediated growth inhibitory effects. In a murine bone marrow transplantation model, the coexpression of SOCS1 and FLT3-ITD significantly shortened the latency of a myeloproliferative disease compared with FLT3-ITD alone (P < .01). Mechanistically, SOCS proteins shield FLT3-ITD from external cytokine control, thereby promoting leukemogenesis. The data demonstrate that SOCS1 acts as a conditional oncogene, providing novel molecular insights into cytokine resistance in oncogenic transformation. Restoring cytokine control may provide a new way of therapeutic intervention.
authors.affiliation: Department of Medicine, Hematology/Oncology, Goethe University, Frankfurt, Germany.
authors.forename: Pavankumar N G
authors.initials: PN
authors.lastname: Reddy
authors.forename: Bülent
authors.initials: B
authors.lastname: Sargin
authors.forename: Chunaram
authors.initials: C
authors.lastname: Choudhary
authors.forename: Stefan
authors.initials: S
authors.lastname: Stein
authors.forename: Manuel
authors.initials: M
authors.lastname: Grez
authors.forename: Carsten
authors.initials: C
authors.lastname: Müller-Tidow
authors.forename: Wolfgang E
authors.initials: WE
authors.lastname: Berdel
authors.forename: Hubert
authors.initials: H
authors.lastname: Serve
authors.forename: Christian H
authors.initials: CH
authors.lastname: Brandts
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D020440:Gene Duplication; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007372:Interferons / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D009196:Myeloproliferative Disorders / Q000235:genetics* / Q000276:immunology* / Q000473:pathology; D050799:STAT5 Transcription Factor / Q000235:genetics / Q000276:immunology; D000071222:Suppressor of Cytokine Signaling 1 Protein; D050826:Suppressor of Cytokine Signaling Proteins / Q000235:genetics* / Q000276:immunology; D051941:fms-Like Tyrosine Kinase 3 / Q000235:genetics* / Q000276:immunology
chemical_list: D050799:STAT5 Transcription Factor; C491590:Socs1 protein, mouse; D000071222:Suppressor of Cytokine Signaling 1 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D007372:Interferons; C497971:Flt3 protein, mouse; D051941:fms-Like Tyrosine Kinase 3