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We hypothesized that analysis of single nucleotide polymorphism arrays (SNP-A) and new molecular defects may provide new insight in the pathogenesis of systemic mastocytosis (SM). SNP-A karyotyping was applied to identify recurrent areas of loss of heterozygosity and bidirectional sequencing was performed to evaluate the mutational status of TET2, DNMT3A, ASXL1, EZH2, IDH1/IDH2 and the CBL gene family. Overall survival (OS) was analyzed using the Kaplan-Meier method. We studied a total of 26 patients with SM. In 67% of SM patients, SNP-A karyotyping showed new chromosomal abnormalities including uniparental disomy of 4q and 2p spanning TET2/KIT and DNMT3A. Mutations in TET2, DNMT3A, ASXL1 and CBL were found in 23%, 12%, 12%, and 4% of SM patients, respectively. No mutations were observed in EZH2 and IDH1/IDH2. Significant differences in OS were observed for SM mutated patients grouped based on the presence of combined TET2/ DNMT3A/ASXL1 mutations independent of KIT (P = 0.04) and sole TET2 mutations (P,0.001). In conclusion, TET2, DNMT3A and ASXL1 mutations are also present in mastocytosis and these mutations may affect prognosis, as demonstrated by worse OS in mutated patients. [ABSTRACT FROM AUTHOR]

Stem cell factor (SCF) mediated KIT receptor activation plays a pivotal role in mast cell growth, maturation and survival. However, the signaling events downstream from KIT are poorly understood. Mast cells express multiple regulatory subunits of class 1A PI3Kinase (PI3K) including p85α, p85β, p50α, and p55α. While it is known that PI3K plays an essential role in mast cells; the precise mechanism by which these regulatory subunits impact specific mast cell functions including growth, survival and cycling are not known. We show that loss of p85α impairs the growth, survival and cycling of mast cell progenitors (MCp). To delineate the molecular mechanism (s) by which p85α regulates mast cell growth, survival and cycling, we performed microarray analyses to compare the gene expression profile of MCps derived from WT and p85α-deficient mice in response to SCF stimulation. We identified 151 unique genes exhibiting altered expression in p85α-deficient cells in response to SCF stimulation compared to WT cells. Functional categorization based on DAVID bioinformatics tool and Ingenuity Pathway Analysis (IPA) software relates the altered genes due to lack of p85α to transcription, cell cycle, cell survival, cell adhesion, cell differentiation, and signal transduction. Our results suggest that p85α is involved in mast cell development through regulation of expression of growth, survival and cell cycle related genes. [ABSTRACT FROM AUTHOR]