Histone deacetylase inhibitor SAHA mediates mast cell death and epigenetic silencing of constitutively active D816V KIT in systemic mastocytosis.

Katarina Lyberg,Hans Hägglund,Hani Abdulkadir Ali,Gunnar Nilsson,Michel Arock,Matilda Kjellander,Johanna Ungerstedt,Jennine Grootens,Malin Tirfing

doi:10.18632/oncotarget.14181

Abstract

Systemic mastocytosis (SM) is a clonal bone marrow disorder, where therapeutical options are limited. Over 90% of the patients carry the D816V point mutation in the KIT receptor that renders this receptor constitutively active. We assessed the sensitivity of primary mast cells (MC) and mast cell lines HMC1.2 (D816V mutated), ROSA (KIT WT) and ROSA (KIT D816V) cells to histone deacetylase inhibitor (HDACi) treatment. We found that of four HDACi, suberoyl anilide hydroxamic acid (SAHA) was the most effective in killing mutated MC. SAHA downregulated KIT, followed by major MC apoptosis. Primary SM patient MC cultured ex vivo were even more sensitive to SAHA than HMC1.2 cells, whereas primary MC from healthy subjects were less affected. There was a correlation between cell death and SM disease severity, where cell death was more pronounced in the case of aggressive SM, with almost 100% cell death among MC from the mast cell leukemia patient. Additionally, ROSA (KIT D816V) was more affected by HDACi than ROSA (KIT WT) cells. Using ChIP qPCR, we found that the level of active chromatin mark H3K18ac/H3 decreased significantly in the KIT region. This epigenetic silencing was seen only in the KIT region and not in control genes upstream and downstream of KIT, indicating that the downregulation of KIT is exerted by specific epigenetic silencing. In conclusion, KIT D816V mutation sensitized MC to HDACi mediated killing, and SAHA may be of value as specific treatment for SM, although the specific mechanism of action requires further investigation.

Highlights

Systemic mastocytosis (SM) is a rare clonal bone marrow disease, previously defined as a subtype of myeloproliferative neoplasms but has recently been redefined as an own disease entity in the 2016 WHO classification of hematological malignancies [1]
We assessed the sensitivity of primary mast cells (MC) and mast cell lines HMC1.2 (D816V mutated), ROSA (KIT WT) and ROSA (KIT D816V) cells to histone deacetylase inhibitor (HDACi) treatment
We demonstrate that in human SM cell lines carrying the D816V mutation, suberoyl anilide hydroxamic acid (SAHA) downregulates KIT mRNA followed by decreased KIT protein levels, cell surface KIT expression and apoptosis, and that the mechanism is at least partially via epigenetic silencing

Summary

Introduction

Systemic mastocytosis (SM) is a rare clonal bone marrow disease, previously defined as a subtype of myeloproliferative neoplasms but has recently been redefined as an own disease entity in the 2016 WHO classification of hematological malignancies [1]. SM is characterized by elevated numbers of mast cells (MC) in one or more tissues, almost always including the bone marrow, and enhanced levels of MC mediators, typically tryptase and histamine [2, 3]. SM www.impactjournals.com/oncotarget may be indolent (ISM), with no impact on life expectancy, or aggressive (ASM) with a survival of 1-2 years. Mast cell leukemia (MCL), which is the most aggressive category of SM, is characterized by > 20% of malignant circulating MCs and has the worst prognosis of all SM categories, median overall survival being less than 6 months. Management options are limited to symptomatic treatment, and there is no curative therapy [2, 4, 5], except for allogeneic stem cell transplantation, the majority of ASM patients are elderly and not eligible for stem cell transplant [6]

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