Oncogenic D816V-KIT signaling in mast cells causes persistent IL-6 production

• Published in: Haematologica (Roma) Vol. 105; no. 1; pp. 124 - 135
• Main Authors: Tobío, Araceli, Bandara, Geethani, Morris, Denise A, Kim, Do-Kyun, O'Connell, Michael P, Komarow, Hirsh D, Carter, Melody C, Smrz, Daniel, Metcalfe, Dean D, Olivera, Ana
• Format: Journal Article
• Language: English
• Published: Italy Ferrata Storti Foundation 01.01.2020
• Subjects: Humans; Interleukin-6 - genetics; Mast Cells; Mastocytosis, Systemic - diagnosis; Mastocytosis, Systemic - genetics; Mutation; Phosphatidylinositol 3-Kinases; Proto-Oncogene Proteins c-kit - genetics
• ISSN: 0390-6078; 1592-8721
• DOI: 10.3324/haematol.2018.212126

Persistent dysregulation of IL-6 production and signaling have been implicated in the pathology of various cancers. In systemic mastocytosis, increased serum levels of IL-6 associate with disease severity and progression, although the mechanisms involved are not well understood. Since systemic mastocytosis often associates with the presence in hematopoietic cells of a somatic gain-of-function variant in KIT, D816V-KIT, we examined its potential role in IL-6 upregulation. Bone marrow mononuclear cultures from patients with greater D816V allelic burden released increased amounts of IL-6 which correlated with the percentage of mast cells in the cultures. Intracellular IL-6 staining by flow cytometry and immunofluorescence was primarily associated with mast cells and suggested a higher percentage of IL-6 positive mast cells in patients with higher D816V allelic burden. Furthermore, mast cell lines expressing D816V-KIT, but not those expressing normal KIT or other KIT variants, produced constitutively high IL-6 amounts at the message and protein levels. We further demonstrate that aberrant KIT activity and signaling are critical for the induction of IL-6 and involve STAT5 and PI3K pathways but not STAT3 or STAT4. Activation of STAT5A and STAT5B downstream of D816V-KIT was mediated by JAK2 but also by MEK/ERK1/2, which not only promoted STAT5 phosphorylation but also its long-term transcription. Our study thus supports a role for mast cells and D816V-KIT activity in IL-6 dysregulation in mastocytosis and provides insights into the intracellular mechanisms. The findings contribute to a better understanding of the physiopathology of mastocytosis and suggest the importance of therapeutic targeting of these pathways.