-Author name in bold denotes the presenting author
-Asterisk * with author name denotes a Non-ASH member
Clinically Relevant Abstract denotes an abstract that is clinically relevant.

PhD Trainee denotes that this is a recommended PHD Trainee Session.

Ticketed Session denotes that this is a ticketed session.

2834 Histone Deacetylase Inhibitor SAHA Mediates Epigenetic Silencing of KIT D816V Mutated Systemic Mastocytosis Primary Mast Cells and Selective Apoptosis of Mutated Mast Cells

Myeloproliferative Syndromes: Basic Science
Program: Oral and Poster Abstracts
Session: 635. Myeloproliferative Syndromes: Basic Science: Poster II
Sunday, December 6, 2015, 6:00 PM-8:00 PM
Hall A, Level 2 (Orange County Convention Center)

Hani Abdulkadir1*, Jennine Grootens2*, Matilda Kjellander1*, Eva Hellström Lindberg, MD, PhD3, Gunnar Nilsson, Professor2* and Johanna Ungerstedt, Associate Professor1*

1Department of Medicine Huddinge, Karolinska Institutet, and Hematology Center, Karolinska University Hospital, Stockholm, Sweden, Stockholm, Sweden
2Clinical Immunology and Allergy Unit, Department of Medicine Solna, Karolinska University Hospital, Karolinska Institutet, Stockholm, Sweden, Stockholm, Sweden
3Center for Hematology and Regenerative Medicine, Department of Medicine, Karolinska Institutet, Karolinska University Hospital Huddinge, Sweden, Stockholm, Sweden

Systemic mastocytosis (SM) is a myeloproliferative disease for which there is currently no specific therapy. Over 90% of the patients carry the D816V point mutation that renders the KIT receptor constitutively active. In the current study, we assessed the sensitivity of mast cell line HMC1.2 and primary SM patient mast cells to histone deacetylase inhibitors, and found that SAHA is most efficient.  SAHA induced a rapid downregulation of KIT mRNA, with  a subsequent reduction in total KIT protein as well as cell surface KIT. This was followed by major mast cell apoptosis. Primary SM patient mast cells cultured ex vivo were even more sensitive to SAHA than HMC1.2 cells, whereas healthy subject mast cells were unaffected. There was a correlation between cell death and SM disease severity, where cell death was more pronounced in the case of aggressive disease, with almost 100% cell death among mast cells from the mast cell leukemia patient. Using ChIP qPCR, we found that the level of active chromatin mark H3K18ac/totalH3 decreased significantly in the KIT region, due to an increase in H3 density. This epigenetic silencing was specific to the KIT region and not seen in control genes upstream and downstream of KIT. Primary analysis of ChIP-seq data for histone marks H3K4me3 and H3K27me3, demonstrates a downregulation of transcription factors involved in activation of KIT receptor, such as MAPK, for the SAHA treated samples. This indicates an indirect epigenetic silencing of KIT. Our results therefore demonstrate that SAHA epigenetically silences KIT, and work is ongoing to elucidate the exact mechanisms of KIT regulation. Altogether, SAHA maybe a specific treatment for SM.

Disclosures: No relevant conflicts of interest to declare.

*signifies non-member of ASH