It is noteworthy that the patient with MCL did not have the classical D816V mutation, but a D820Y KIT mutation. 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 Rabbit Polyclonal to VANGL1 HDACi mediated killing, and SAHA may ABT-888 (Veliparib) be of value as specific treatment for SM, although the specific mechanism of action requires further investigation. expression in normal or neoplastic human MC. Epigenetic changes include DNA methylation and posttranslational modifications of histones, the regulation of which is frequently perturbed in myeloid malignancies such as the myelodysplastic syndromes and myeloproliferative neoplasms [13]. In recent years, several point mutations in genes encoding epigenetic regulators have been detected in such malignancies, with implications for their pathogenesis, progression and prognosis [14, 15]. Similar mutation patterns are also present in SM [16, 17] and accumulating evidence indicates that improved understanding of these recurrent mutations allow prediction of ABT-888 (Veliparib) development towards aggressive disease phenotypes [18C21]. Histone deacetylase inhibitors (HDACi) are small molecules of various structure background of which many are in clinical trials for solid and hematological tumors, and a few are already approved for some specific tumor subtypes [22]. The HDACi suberoyl anilide hydroxamic acid (SAHA) is ABT-888 (Veliparib) a pan-inhibitor of class I and II HDACs, and in addition also affects acetylation of non-histone proteins, of which one of the most extensively studied is HSP90 [23, 24]. Treatment with SAHA alters the expression of 5-15% of protein coding ABT-888 (Veliparib) genes, depending on cell type [22, 25, 26]. SAHA induces apoptosis in malignant cells [27] and is currently in phase I-III clinical trials for treatment of a variety of solid and hematological malignancies, and is approved for treatment of cutaneous T cell lymphoma, as is Romidepsin in the US. Recently, Panobinostat, another HDACi similar in function to SAHA, was approved as third line treatment in a combination regimen, for myeloma. In human GIST tumors that frequently carry KIT mutations, however not commonly the D816V mutation, SAHA and other HDACi have been shown to decrease KIT mRNA levels and acetylate HSP90, abrogating its activity as a KIT chaperone [24]. Additionally, the HDACi AR-42 has been described to downregulate constitutively active KIT in malignant murine and canine mast cells [28], although the underlying mechanism remains unclear. The purpose of this study was to characterize the effect of HDACi in human SM cells. We demonstrate that in human SM cell lines carrying the D816V mutation, 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. In addition, we show that primary mast cells from SM patients are highly sensitive to SAHA-induced cell death, whereas normal bone marrow mast cells are resistant. Thus, HDACi may be a potential clinical treatment option for SM patients. RESULTS HDACi reduces HMC1.2 growth and viability SAHA, Romidepsin and Panobinostat, three inhibitors of class I and II HDACs, and Valproic acid, an inhibitor of class I HDACs, were assessed for dose- and time-dependent effects on HMC1.2 growth and viability. All HDACi induced a dose-.