Synergistic Growth-Inhibitory Effects of Two Tyrosine Kinase Inhibitors, Dasatinib and PKC412, on Neoplastic Mast Cells Expressing the D816V-Mutated Oncogenic Variant of KIT.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 526-526 ◽  
Author(s):  
Karoline V. Gleixner ◽  
Matthias Mayerhofer ◽  
Karoline Sonneck ◽  
Alexander Gruze ◽  
Puchit Samorapoompichit ◽  
...  
Keyword(s):  
Mast Cell ◽  
Mast Cells ◽  
Tyrosine Kinase ◽  
Tyrosine Kinase Inhibitors ◽  
Kinase Inhibitors ◽  
Systemic Mastocytosis ◽  
Cell Leukemia ◽  
Inhibitory Effects ◽  
Mast Cell Leukemia ◽  
Kit D816v

Abstract In a majority of all patients with systemic mastocytosis (SM) including aggressive SM and mast cell leukemia (MCL), neoplastic cells display the D816V-mutated variant of KIT. The respective oncoprotein, KIT-D816V, exhibits constitutive tyrosine kinase (TK) activity and has been implicated in malignant cell growth. Therefore, several attempts have been made to identify KIT-D816V-targeting drugs. We found that the TK-inhibitor dasatinib (BMS-354825) inhibits TK activity of wild type (wt) KIT and KIT-D816V in Ba/F3 cells with doxycycline-inducible KIT-expression. In addition, dasatinib was found to inhibit KIT D816V-induced cluster formation and viability in Ba/F3 cells as well as growth of HMC-1.1 cells (KIT-D816V-negative) and HMC-1.2 cells (KIT-D816V-positive). The effects of dasatinib on growth of HMC-1 cells were dose-dependent, with 100–1,000-fold higher IC50-values in cells harbouring KIT-D816V compared to cells lacking KIT-D816V. Furthermore, dasatinib was found to inhibit the growth of primary neoplastic mast cells in SM in all patients examined. The inhibitory effects of dasatinib in HMC-1 cells were found to be associated with apoptosis and a decrease in expression of CD2 and CD63 as determined by flow cytometry. In addition, dasatinib was found to cooperate with the tyrosine kinase inhibitors PKC412 (midostaurin), AMN107 (nilotinib), and STI571 (imatinib), as well as with 2CdA (cladribine) in producing growth-inhibition in neoplastic mast cells. In HMC-1.1 cells, all drug-interactions applied were found to be synergistic. By contrast, in HMC-1.2 cells, only the combinations “dasatinib+PKC412” and “dasatinib+2CdA” were found to produce synergistic effects. These drug-combinations may thus represent an interesting pharmacologic approach for the treatment of patients with aggressive systemic mastocytosis or mast cell leukemia.

Detection of Activated STAT5 in Neoplastic Mast Cells in Patients with Systemic Mastocytosis: Role of c-kit D816V.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 3515-3515 ◽  
Author(s):  
Karoline Sonneck ◽  
Matthias Mayerhofer ◽  
Karoline V. Gleixner ◽  
Marc Kerenyi ◽  
Maria-Theresa Krauth ◽  
...  
Keyword(s):  
Mast Cell ◽  
Mast Cells ◽  
Systemic Mastocytosis ◽  
Cell Leukemia ◽  
Oncogenic Signaling ◽  
Kit Mutation ◽  
Knock Out ◽  
Mast Cell Leukemia ◽  
Kit D816v

Abstract Recent data suggest that activated STAT5 contributes to growth and differentiation of mast cells (MC) and that STAT5-knock out mice are MC-deficient. We have recently shown that constitutively activated STAT5 acts as a potent oncogenic signaling molecule in hematopoietic progenitor cells (Cancer Cell2005;7:87–99). In the present study, we examined the expression of activated STAT5 in neoplastic MC in systemic mastocytosis (SM) and asked whether the SM-related oncogene c-kit D816V is involved in STAT5-activation. For the immunohistochemical detection of activated tyrosine phosphorylated STAT5 (P-Y-STAT5), we used the specific monoclonal antibody AX1 (Advantex) which does not react with inactive STAT5. In all patients with SM tested (indolent SM, n=11; smouldering SM, n=2; aggressive SM, n=1; mast cell leukemia, n=1; all exhibiting c-kit D816V), MC were found to display P-Y-STAT5. Expression of activated STAT5 was also demonstrable in the c-kit D816V-positive mast cell leukemia-derived cell line HMC-1. The reactivity of HMC-1 cells with AX1 antibody was abrogated by a STAT5-specific blocking-peptide. To define the role of c-kit D816V in STAT5-activation, Ba/F3 cells with doxycycline-inducible expression of c-kit D816V (Ton.kit) were employed. In these cells, induction of c-kit D816V was followed by a massive increase in phosphorylated STAT5 as determined by a specific DNA-binding assay, whereas the total amounts of STAT5-mRNA and of the STAT5-protein showed only a slight increase or remained unchanged. In summary, these data show that neoplastic MC in SM express activated STAT5 (P-Y-STAT5), and that the transforming c-kit mutation D816V leads to persistent activation of STAT5 in these cells.

Mast cell leukemia

Blood ◽  
2013 ◽  
Vol 121 (8) ◽  
pp. 1285-1295 ◽  
Author(s):  
Sophie Georgin-Lavialle ◽  
Ludovic Lhermitte ◽  
Patrice Dubreuil ◽  
Marie-Olivia Chandesris ◽  
Olivier Hermine ◽  
...  
Keyword(s):  
Mast Cell ◽  
Mast Cells ◽  
Cell Activation ◽  
De Novo ◽  
Systemic Mastocytosis ◽  
Mast Cell Activation ◽  
Cell Leukemia ◽  
Mast Cell Leukemia ◽  
Kit D816v

Abstract Mast cell leukemia (MCL) is a very rare form of aggressive systemic mastocytosis accounting for < 1% of all mastocytosis. It may appear de novo or secondary to previous mastocytosis and shares more clinicopathologic aspects with systemic mastocytosis than with acute myeloid leukemia. Symptoms of mast cell activation—involvement of the liver, spleen, peritoneum, bones, and marrow—are frequent. Diagnosis is based on the presence of ≥ 20% atypical mast cells in the marrow or ≥ 10% in the blood; however, an aleukemic variant is frequently encountered in which the number of circulating mast cells is < 10%. The common phenotypic features of pathologic mast cells encountered in most forms of mastocytosis are unreliable in MCL. Unexpectedly, non-KIT D816V mutations are frequent and therefore, complete gene sequencing is necessary. Therapy usually fails and the median survival time is < 6 months. The role of combination therapies and bone marrow transplantation needs further investigation.

scholarly journals Mast Cell Leukemia: Clinical Heterogeneity, Molecular Aberrations, Treatment Responses, Survival, and Prognostic Factors

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 3109-3109 ◽  
Author(s):  
Mohamad Jawhar ◽  
Juliana Schwaab ◽  
Manja Meggendorfer ◽  
Nicole Naumann ◽  
Hans-Peter Horny ◽  
...  
Keyword(s):  
Mast Cell ◽  
Prognostic Factors ◽  
Mast Cells ◽  
Confidence Interval ◽  
Research Funding ◽  
Molecular Characteristics ◽  
Cell Leukemia ◽  
Mast Cell Leukemia ◽  
Treatment Responses ◽  
Kit D816v

Abstract Mast cell leukemia (MCL) is a rare variant of advanced systemic mastocytosis (advSM) characterized by ≥20% mast cells (MCs) in a bone marrow (BM) smear. Our current knowledge of MCL, including clinical and molecular characteristics, treatment options, survival, and prognostic factors is limited to case reports, small case-series and/or literature reviews. While the KIT D816V mutation is present in >80-90% of patients in other SM subtypes, it has only been reported in approximately 50% of patients with MCL. Of interest, recent data have highlighted that the molecular pathogenesis of advSM/MCL is complex. In particular, additional mutations in SRSF2, ASXL1 or RUNX1 (S/A/Rpos), seen in 60-70% of advSM patients, have a significant adverse impact on disease phenotype and prognosis (Jawhar et al., Leukemia, 2016). Here, we sought to evaluate a) relevant clinical and molecular characteristics, b) treatment responses, and c) survival and prognostic factors in 28 MCL patients (median age 67 years; range, 45-82; male 57%), enrolled in the 'German Registry of Disorders on Eosinophils and Mast Cells'. The median percentages of MC in BM smears and trephine biopsies were 25% (range, 20-95) and 65% (range, 20-100; 82% ≥50%), respectively. MC in peripheral blood (PB) ≥10% (leukemic MCL) were seen in only 2/28 patients. Median serum tryptase level was 550 µg/L (range, 160-1850; 93% ≥200, normal value <11.4). An associated hematologic neoplasm (AHN), e.g. CMML (n=7), MDS/MPNu (n=6), MDS (n=5) or CEL (n=2), was diagnosed in 20/28 (71%) patients. Primary MCL was diagnosed in 16/28 (57%) patients and secondary MCL evolving from other advSM subtypes (SM-AHN, n=10; aggressive SM, n=2) in 12/28 (43%) patients with a median of 18 months (range, 4-71) to transformation. Hematologic C-findings such as hemoglobin <10 g/dL and/or platelets <100x109/L were identified in 26/28 (93%) patients. Non-hematologic signs of organ dysfunction included elevated alkaline phosphatase (AP), seen in 20/28 patients (71%, median 181; range 59-548) and splenomegaly in 28/28 (100%) patients. Spleen volumetry results obtained by magnetic resonance imaging were available in 16 patients and showed marked splenomegaly (≥1200 mL) in 8/16 cases (50%). Mutations in KIT were identified in 25/28 (89%) patients (D816V, n=19; D816H, n=3; D816Y, n=2; F522C, n=1) with a median KIT D816V expressed allele burden of 43% (range 20-98) in peripheral blood as measured by quantitative RT-PCR (RT-qPCR). S/A/Rpos were identified in 13/25 (52%) patients (by NGS analyses of 18 myeloid genes). Median observation from the time of MCL diagnosis was 13 months (range, 2-86) and 18/28 patients (64%) died with a median OS of 17 months (95% confidence interval [CI], 10-24). Cytoreductive treatment included midostaurin (n=13), cladribine followed by midostaurin or vice versa (n=9), cladribine (n=3), midostaurin and/or cladribine followed by intensive chemotherapy (n=3) with (n=1) or without (n=2) allogeneic stem cell transplantation. The median overall survival (OS) was 17 months (95% confidence interval, CI [10-24]) with a 2-year OS probability of 24% for all patients. In univariate analyses of multiple clinical, laboratory and molecular variables only bicytopenia (hemoglobin <10 g/dL and platelets <100x109/L, n=13 vs. hemoglobin ≥10 g/dL or platelets ≥100x109/L, n=13, P=0.02, hazard ratio, HR 3.2 [1.2-8.9]), elevated AP (P=0.009, HR 3.3 [1.3-8.3]) and S/A/Rpos (P=0.007, HR 5.0 [1.8-18.1]) were significantly inferior regarding OS. In multivariate analyses, S/A/Rpos remained the only independent poor risk marker for OS (Figure). There was no significant difference regarding OS between primary vs. secondary MCL (Figure) or MCL with vs. without AHN. Of interest, no difference regarding OS was detected in comparison between patients treated with midostaurin (n=13) vs. patients treated with cladribine following midostaurin or vice versa (n=9). In summary, we have found that a) leukemic MCL and MCL without C-findings are rare, b) secondary MCL is frequent and evolves from other advSM subtypes but not ISM, c) KIT D816V mutations are more frequent than previously reported and KIT D816V negative patients should be tested for other KIT mutations d) the prognostically highly relevant mutations in the S/A/R gene panel are present in approximately 50% of patients with MCL, and e) median OS is approximately 1.5 years with significantly inferior survival in S/A/Rpos patients. Disclosures Meggendorfer: MLL Munich Leukemia Laboratory: Employment. Valent:Amgen: Honoraria; Novartis: Honoraria, Research Funding; Celegene: Honoraria, Research Funding.

PKC412 Inhibits In Vitro Growth of Neoplastic Mast Cells Expressing the D816V-Mutated Variant of KIT: Comparison with AMN107 and Imatinib, and Evaluation of Drug-Interactions.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 3523-3523
Author(s):  
Karoline V. Gleixner ◽  
Matthias Mayerhofer ◽  
Karl J. Aichberger ◽  
Sophia Derdak ◽  
Karoline Sonneck ◽  
...  
Keyword(s):  
Mast Cell ◽  
Mast Cells ◽  
Drug Interactions ◽  
Leukemia Cell ◽  
Leukemia Cell Line ◽  
Human Mast Cell ◽  
Cell Leukemia ◽  
Kit Mutation ◽  
Mast Cell Leukemia ◽  
Kit D816v

Abstract In most patients with systemic mastocytosis (SM) including aggressive SM and mast cell leukemia (MCL), neoplastic cells express the oncogenic c-KIT mutation D816V. KIT-D816V is associated with constitutive tyrosine kinase (TK) activity and thus represents an attractive target of drug therapy. However, most available TK inhibitors including STI571=imatinib, fail to block TK-activity of KIT D816V at pharmacologic concentrations. We provide evidence that the novel TK-targeting drugs PKC412 and AMN107 decrease TK-activity of D816V-mutated KIT and counteract growth of Ba/F3 cells with doxycycline-induced expression of KIT D816V as well as growth of the human mast cell leukemia cell line HMC-1 expressing this c-KIT mutation. PKC412 was found to be the superior drug with IC50 values of 50–250 nM and without differences seen between HMC-1 cells exhibiting or lacking KIT D816V. By contrast, AMN107 exhibited potent effects only in the absence of KIT D816V in HMC-1 cells. Corresponding results were obtained with Ba/F3 cells exhibiting wild-type or the D816V-mutated variant of KIT. Moreover, we found that PKC412 and AMN107 inhibit growth of primary neoplastic MC in a patient with KIT D816V+ SM. The growth-inhibitory effects of PKC412 and AMN107 on HMC-1 cells were associated with TK-inhibition of KIT and with induction of apoptosis. In addition, PKC412 was found to downregulate expression of CD2 and CD63, two cell surface antigens upregulated in SM. In co-incubation experiments, PKC412 was found to synergize with AMN107, imatinib, and 2CdA in producing growth inhibition in HMC-1 cells lacking KIT D816V, whereas in KIT D816V+ HMC-1 cells, drug-interactions were additive rather than synergistic. Together, PKC412 and AMN107 alone and in combination counteract growth of neoplastic mast cells. Both drugs may therefore be considered as novel promising agents for targeted therapy in patients with aggressive SM or MCL.

Aggressive Systemic Mastocytosis Is Associated with a High Kit D816V Allele Burden in Peripheral Blood.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 2899-2899
Author(s):  
Philipp Erben ◽  
Georg Bolz ◽  
Juliana Popa ◽  
Georgia Metzgeroth ◽  
Martin C Müller ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Detection Limit ◽  
Mast Cells ◽  
Tyrosine Kinase ◽  
Peripheral Blood ◽  
Kinase Inhibitors ◽  
Systemic Mastocytosis ◽  
Allele Burden ◽  
Minor Criteria ◽  
Kit D816v

Abstract Abstract 2899 Poster Board II-875 According to 2008 WHO definitions, diagnosis of systemic mastocytosis (SM) is based on the presence of one major criteria (multifocal dense infiltrates of mast cells in bone marrow or organ biopsies) and at least one of the following minor criteria (i) >25% are atypical cells on bone marrow smears or are spindle-shaped in mast cell infiltrates of visceral organs, ii) KIT point mutation at codon 816 in the bone marrow or other extracutaneous organs, iii) mast cells express CD2 and/or CD25, iv) baseline serum tryptase concentration >20 ng/mL) or the presence of at least three minor criteria. Patients with aggressive SM (ASM) have to present with one or more C-findings (i) neutrophils <1,000/μL, Hb <10g/dL, or platelets <100,000/μL, ii) hepatomegaly with impaired liver function – elevated transaminases and/or bilirubin levels and/or hypoalbuminemia, iii) palpable splenomegaly with signs of hypersplenism, iv) malabsorption with significant hypoalbuminemia and/or significant loss. ASM and MCL are clearly associated with an inferior survival. The activating KIT D816V point mutation is thought to be pivotal for pathogenesis and potential targeted therapy with novel tyrosine kinase inhibitors. However, conventional sequencing (CS) of RNA/DNA extracted from bone marrow (BM) samples of SM patients reveals the mutation in less than 50-60% of patients while peripheral blood (PB) samples are frequently negative as consequence of low numbers of malignant cells and poor assay sensitivity. For better qualitative and additional quantitative assessment of the KIT D816V allele burden (expressed as ratio KIT D816V vs. KIT wildtype), we sought to establish (i) a D-HPLC (denaturing-high performance liquid chromatography) assay combined with direct sequencing in case of a positive D-HPLC signal and (ii) a LightCyclerTM based quantitative PCR (RQ-PCR). The assay sensitivities were calculated through serial cell (KIT D816V positive HMC-1 cells in NB4 cells) and RNA dilutions. The detection limit was estimated between 0.1 and 0.5% for both assays which was thus significantly improved in comparison to the detection limit of CS which was at 10–15%. Patient material was available from BM (n=134) and PB (n=93) from 173 patients (88 m, 85 f, median age 54 years) with diagnosis of SM including 10 patients with confirmed ASM (n=9) or aleukemic variant of MCL (n=1) according to WHO definitions. At diagnosis, D-HPLC, RQ-PCR and CS were positive in 78% (104/134), 84% (112/134) and 60% (80/134) of BM samples, respectively. Two patients had a KIT D816H and one patient had a KIT D816L mutation. In 54 cases with contemporaneously collected BM and PB samples, the KIT D816V mutation was found in PB of BM positive patients by D-HPLC, RQ-PCR and CS in 47% (22/46), 55% (27/49) and 38% (14/37) of cases, respectively. This information allowed the detection of the KIT D816V mutation in an additional 27 of 39 (69%) patients without available bone marrow biopsies. All ASM patients were KIT D816V positive in PB with a median KIT D816V allele burden of 36% (range 26–98%) vs. 7.8% (range 0.1–61%) in other stages of SM (p=0.0021). Eleven of 124 (8.9%) SM patients with a KIT D816V allele burden >20% are currently explored for the potential diagnosis of ASM or MCL. In conclusion, D-HPLC is a reliable and sensitive method for the screening of variable KIT mutations in BM and PB of SM patients and is clearly superior to CS. Application of RQ-PCR assays for the most common D816V mutation may overlook rare mutations but allows quantification of the KIT D816V allele burden which may be useful for diagnosis of ASM and monitoring of residual disease during treatment with novel tyrosine kinase inhibitors, e.g. midostaurin or dasatinib. Disclosures: No relevant conflicts of interest to declare.

Aleukemic Mast Cell Leukemia (aMCL) - Clinical Characteristics and Outcomes

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 4255-4255 ◽  
Author(s):  
Preetesh Jain ◽  
Sa Wang ◽  
Hagop M. Kantarjian ◽  
Nawid Sarwari ◽  
Keyur P. Patel ◽  
...  
Keyword(s):  
Overall Survival ◽  
Mast Cell ◽  
Mast Cells ◽  
Research Funding ◽  
Median Overall Survival ◽  
Systemic Mastocytosis ◽  
Cell Transplant ◽  
Cell Leukemia ◽  
Mast Cell Leukemia

Abstract ABSTRACT Introduction: Systemic mastocytosis (SM) is a complex and rare disease of clonal mast cells. Mast cell leukemia (MCL) is a very rare form of SM seen in <1% patients. We describe here our experience with MCL patients treated at our institution. Methods: We reviewed the medical records of 218 patients with mastocytosis who presented to our institution between 1994 and 2016. The survival of patients was calculated from the date of initial presentation to the date of last follow up. Kaplan-Meier product limit method was used to estimate the median survival. Results: From the 218 patients with mastocytosis, we identified 13 patients with MCL (6.5%). All 13 had aleukemic variant of MCL (aMCL; no presence of mast cells in blood measured by standard CBC technique but with ≥ 20% atypical mast cells in the marrow aspirate). In addition, in 4 of 13 patients, associated hematologic neoplasm (AHN) was present: 2 with myelodysplastic syndrome, 1 with chronic myelomonocytic leukemia and 1 with multiple myeloma. Median age of 13 patients was 62 years (range 24-75 years). Baseline features are summarized in Table-1. During their initial clinical presentation, 85% had constitutional symptoms, 54% had skin rash and other cutaneous symptoms, 31% gastrointestinal symptoms and 23% had joint pains. Imaging studies were performed in 6 patients: 5/6 had enlarged liver and/or spleen, 3 patients had nodal involvement, 2 had sclerotic bony lesions and 1 pt had adrenal involvement. Serum tryptase was >200 ng/ml in all the patients. Testing for c-KITD816V mutation was performed in 9 patients using mutation-specific quantitative (real-time) PCR, of which mutation was undetectable in 6 and detected in 3 patients. The sensitivity of detection was approximately 1 in 1000 mutation-bearing cells. None had FIP1L1-PDGFRA mutations. Treatments given were heterogeneous. Two patients each received imatinib with no response, 2 received dasatinib (one [positive for KITD816V mutation] had significant improvement in hepatosplenomegaly and pruritus but progressed after 1 year of dasatinib therapy), 2 cladribine based therapy with no response, and 2 with stem cell transplant and progression after it. Overall, median follow up was 111 months (1.4-131); 3 patients were alive and 9 died at the time of last follow up. Interestingly, among our 13 aMCL patients, those 4 with AHN appear to have had worse outcome: Figure-1A, shows the median overall survival (OS) of aMCL vs aMCL-AHN (32 vs 25 months; p=0.22). Overall, the median overall survival (OS) of aMCL without AHN was significantly inferior compared to aggressive systemic mastocytosis (ASM) and indolent systemic mastocytosis (ISM) without AHN: 31 months and not reached respectively (Figure-1B; p<0.001). Conclusions: In this analysis, we have shown that aMCL is very rare and these patients have very poor outcome. Based on the recent data from Gotlib et al NEJM 2016, role of midostaurin in the treatment of MCL should be explored. Further studies to characterize the genomic profile of patients with MCL are needed to identify potential therapeutic targets and disease resistance pathways. Table Survival of patients with aleukemic mast cell leukemia (aMCL) with/without AHN (A) and survival comparison of aMCL to other types of systemic mastocytosis, all without AHN (B) Table. Survival of patients with aleukemic mast cell leukemia (aMCL) with/without AHN (A) and survival comparison of aMCL to other types of systemic mastocytosis, all without AHN (B) Figure Figure. Disclosures Daver: Sunesis: Consultancy, Research Funding; Kiromic: Research Funding; Ariad: Research Funding; Pfizer: Consultancy, Research Funding; Otsuka: Consultancy, Honoraria; Karyopharm: Honoraria, Research Funding; BMS: Research Funding. Cortes:ARIAD: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Teva: Research Funding. Verstovsek:Celgene: Research Funding; Bristol-Myers Squibb: Research Funding; AstraZeneca: Research Funding; Incyte Corporation: Membership on an entity's Board of Directors or advisory committees, Research Funding; Galena BioPharma: Research Funding; Gilead: Research Funding; CTI BioPharma Corp: Research Funding; Lilly Oncology: Research Funding; NS Pharma: Research Funding; Geron: Research Funding; Promedior: Research Funding; Seattle Genetics: Research Funding; Roche: Research Funding; Pfizer: Research Funding; Genentech: Research Funding.

The Kit-activating mutation D816V enhances stem cell factor–dependent chemotaxis

Blood ◽  
2001 ◽  
Vol 98 (4) ◽  
pp. 1195-1199 ◽  
Author(s):  
Marcia L. Taylor ◽  
Jaroslaw Dastych ◽  
Devinder Sehgal ◽  
Magnus Sundstrom ◽  
Gunnar Nilsson ◽  
...  
Keyword(s):  
Mast Cell ◽  
Stem Cell ◽  
Mast Cells ◽  
Tyrosine Kinase ◽  
Tyrosine Kinase Inhibitors ◽  
Stem Cell Factor ◽  
Kinase Inhibitors ◽  
Jurkat Cells ◽  
Wild Type ◽  
Kit Mutation

The D816V mutation of c-kit has been detected in patients with mastocytosis. This mutation leads to constitutive tyrosine kinase activation of Kit. Because stem cell factor (SCF), the ligand for Kit (CD117+), is a chemoattractant for CD117+ cells and one feature of mastocytosis is an abnormal collection of mast cells in tissues derived from CD34+CD117+ mast cell precursors, the hypothesis was considered that the D816V mutation would enhance chemotaxis of these precursor cells. Constructs encoding wild-type Kit or Kit bearing the D816V mutation were transfected into Jurkat cells, labeled with Calcein-am, and migration to SCF assessed in the presence or absence of tyrosine kinase inhibitors. Chemotaxis to SCF was enhanced in D816V transfectants compared to wild-type Kit transfectants (P &lt; .002). Migration of both transfectants was inhibited by tyrosine kinase inhibitors, although D816V transfectants were more sensitive. Chemotaxis was next performed on CD34+CD117+ circulating mast cell precursors obtained from patients with mastocytosis. Analysis of prechemotaxis and migrated cells showed that whereas less than 10% in the prechemotaxis sample had the D816V mutation, 40% to 80% of migrated cells had this mutation. These results demonstrate that the D816V Kit mutation enhances chemotaxis of CD117+ cells, offering one explanation for increased mast cells observed in tissues of patients with mastocytosis.

Expression, epitope analysis, and functional role of the LFA-2 antigen detectable on neoplastic mast cells

Blood ◽  
2001 ◽  
Vol 98 (13) ◽  
pp. 3784-3792 ◽  
Author(s):  
Gerit-Holger Schernthaner ◽  
John-Hendrik Jordan ◽  
Minoo Ghannadan ◽  
Hermine Agis ◽  
Dorian Bevec ◽  
...  
Keyword(s):  
Mast Cell ◽  
Mast Cells ◽  
Messenger Rna ◽  
Functional Role ◽  
Systemic Mastocytosis ◽  
Cell Leukemia ◽  
Natural Ligand ◽  
Mast Cell Leukemia ◽  
And Function

Abstract Recent data suggest that mast cells (MCs) in patients with systemic mastocytosis or mast cell leukemia express a CD2-reactive antigen. To explore the biochemical nature and function of this antigen, primary MCs as well as the MC line HMC-1 derived from a patient with mast cell leukemia were examined. Northern blot experiments revealed expression of CD2 messenger RNA in HMC-1, whereas primary nonneoplastic MCs did not express transcripts for CD2. In cell surface staining experiments, bone marrow (BM) MCs in systemic mastocytosis (n = 12) as well as HMC-1 cells (30%-80%) were found to express the T11-1 and T11-2 (but not T11-3) epitopes of CD2. By contrast, BM MCs in myelodysplastic syndromes and nonhematologic disorders (bronchiogenic carcinoma, foreskin phimosis, uterine myeomata ) were consistently CD2−. All MC species analyzed including HMC-1 were found to express LFA-3 (CD58), the natural ligand of CD2. To study the functional role of CD2 on neoplastic MCs, CD2+ and CD2− HMC-1 cells were separated by cell sorting. CD2+ HMC-1 cells were found to form spontaneous aggregates and rosettes with sheep erythrocytes in excess over CD2−cells, and a T11-1 antibody inhibited both the aggregation and rosette formation. Moreover, exposure of CD2+ HMC-1 cells to T11-1 or T11-2 antibody was followed by expression of T11-3. In addition, stimulation of neoplastic MCs through T11-3 and a second CD2 epitope resulted in histamine release. These data show that neoplastic MCs express functionally active CD2. It is hypothesized that expression of CD2 is associated with pathologic accumulation and function of MCs in systemic mastocytosis.

scholarly journals Serum Total Tryptase Level Confirms Itself as a More Reliable Marker of Mast Cells Burden in Mast Cell Leukaemia (Aleukaemic Variant)

2015 ◽  
Vol 2015 ◽  
pp. 1-4
Author(s):  
P. Savini ◽  
M. Rondoni ◽  
G. Poletti ◽  
A. Lanzi ◽  
O. Quercia ◽  
...  
Keyword(s):  
Mast Cell ◽  
Mast Cells ◽  
Systemic Mastocytosis ◽  
Organ Damage ◽  
High Serum ◽  
Cell Leukaemia ◽  
Cell Leukemia ◽  
Tryptase Level ◽  
Mast Cell Leukemia ◽  
Reliable Marker

Mast cell leukemia (MCL) is a very rare form of systemic mastocytosis (SM) with a short median survival of 6 months. We describe a case of a 65-year-old woman with aleukaemic variant of MCL with a very high serum total tryptase level of 2255 μg/L at diagnosis, which occurred following an episode of hypotensive shock. She fulfilled the diagnostic criteria of SM, with a bone marrow smear infiltration of 50–60% of atypical mast cells (MCs). She tested negative for the KIT D816V mutation, without any sign of organ damage (no B- or C-findings) and only few mediator-related symptoms. She was treated with antihistamine alone and then with imatinib for the appearance of anemia. She maintained stable tryptase level and a very indolent clinical course for twenty-two months; then, she suddenly progressed to acute MCL with a serum tryptase level up to 12960 μg/L. The patient died due to haemorrhagic diathesis twenty-four months after diagnosis. This clinical case maybe represents an example of the chronic form of mast cell leukemia, described as unpredictable disease, in which the serum total tryptase level has confirmed itself as a reliable marker of mast cells burden regardless of the presence of other signs or symptoms.

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