KIT-D816V–independent oncogenic signaling in neoplastic cells in systemic mastocytosis: role of Lyn and Btk activation and disruption by dasatinib and bosutinib

Blood ◽  
2011 ◽  
Vol 118 (7) ◽  
pp. 1885-1898 ◽  
Author(s):  
Karoline V. Gleixner ◽  
Matthias Mayerhofer ◽  
Sabine Cerny-Reiterer ◽  
Gregor Hörmann ◽  
Uwe Rix ◽  
...  
Keyword(s):  
Systemic Mastocytosis ◽  
Leukemia Cell ◽  
Malignant Neoplasm ◽  
Leukemia Cell Line ◽  
Oncogenic Signaling ◽  
Independent Manner ◽  
Growth Inhibitory ◽  
Indolent Disease ◽  
Kit D816v

Abstract Systemic mastocytosis (SM) either presents as a malignant neoplasm with short survival or as an indolent disease with normal life expectancy. In both instances, neoplastic mast cells (MCs) harbor D816V-mutated KIT, suggesting that additional oncogenic mechanisms are involved in malignant transformation. We here describe that Lyn and Btk are phosphorylated in a KIT-independent manner in neoplastic MCs in advanced SM and in the MC leukemia cell line HMC-1. Lyn and Btk activation was not only detected in KIT D816V-positive HMC-1.2 cells, but also in the KIT D816V-negative HMC-1.1 subclone. Moreover, KIT D816V did not induce Lyn/Btk activation in Ba/F3 cells, and deactivation of KIT D816V by midostaurin did not alter Lyn/Btk activation. siRNAs against Btk and Lyn were found to block survival in neoplastic MCs and to cooperate with midostaurin in producing growth inhibition. Growth inhibitory effects were also obtained with 2 targeted drugs, dasatinib which blocks KIT, Lyn, and Btk activation in MCs, and bosutinib, a drug that deactivates Lyn and Btk without blocking KIT activity. Together, KIT-independent signaling via Lyn/Btk contributes to growth of neoplastic MCs in advanced SM. Dasatinib and bosutinib disrupt Lyn/Btk-driven oncogenic signaling in neoplastic MC, which may have clinical implications and explain synergistic drug interactions.

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.

Delineation of a KIT-Independent Oncogenic Pathway in Neoplastic Mast Cells That Involves Lyn and Btk, and Can Be Disrupted by the KIT/Lyn/Btk-Targeting Drug Dasatinib

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 1541-1541 ◽  
Author(s):  
Karoline V. Gleixner ◽  
Matthias Mayerhofer ◽  
Uwe Rix ◽  
Gregor Hoermann ◽  
Alexander Gruze ◽  
...  
Keyword(s):  
Mast Cells ◽  
Potent Inhibitor ◽  
Systemic Mastocytosis ◽  
Synergistic Effects ◽  
Leukemia Cell ◽  
Leukemia Cell Line ◽  
Growth And Survival ◽  
Myeloid Neoplasm ◽  
Oncogenic Pathway ◽  
Kit D816v

Abstract Systemic mastocytosis (SM) is a myeloid neoplasm characterized by increased growth and survival of neoplastic mast cells (MC). Aggressive SM (ASM) and MC leukemia (MCL) are advanced disease variants that usually are drug-resistant and have an unfavorable prognosis. In most patients, the D816V-mutated ′oncogenic′ variant of KIT is detectable. However, the mutant is also detectable in patients with indolent SM exhibiting a normal life-expectancy, and therefore is not considered to represent a fully transforming oncoprotein. This assumption is also supported by studies in Ba/F3 cells, and whether KIT D816V-targeting drugs are able to induce long-term remission in ASM or MCL, remains to be seen. Therefore, it has been hypothesized that in addition to KIT, other pro-oncogenic molecules and signaling pathways play a role in malignant transformation/progression in SM. We here describe a novel KIT D816V-independent oncogenic pathway in neoplastic MC that involves Lyn and Bruton’s tyrosine kinase (Btk). Western blotting and immunostaining revealed that neoplastic MC display the Btk- and Lyn protein. Both molecules were found to be constitutively phosphorylated in primary neoplastic MC and in the MC leukemia cell line HMC-1. Lyn/Btk-activation was not only detectable in KIT D816V-positive HMC-1.2 cells, but also in the KIT D816V-negative HMC-1.1 subclone. In studies employing Ba/F3 cells with doxycycline-inducible expression of KIT, we were able to show that KIT D816V induces activation of STAT5 and Akt, but does not induce activation of Btk. Correspondingly, pharmacologic deactivation/dephosphorylation of KIT in HMC-1 cells by midostaurin (PKC412) (Novartis, Basel, Switzerland) was not accompanied by a decrease in phosphorylation of Lyn or Btk. The functional significance of Btk expression/activation in neoplastic MC could be demonstrated by a Btk-specific siRNA that reduced the proliferation and survival in HMC-1 cells, and was found to cooperate with midostaurin in producing growth inhibition. In consecutive experiments, we identified the Src/Abl kinase-targeting drug dasatinib (BMS, Princeton, NJ) as a potent inhibitor of Lyn/Btk activation in neoplastic MC. In particular, dasatinib (1 μM) was found to block Lyn and Btk activity in HMC-1.1 cells as well as in HMC-1.2 cells, and corresponding results were obtained with primary neoplastic MC. Finally, as assessed by a chemical proteomics approach, we were able to show that dasatinib directly binds to Btk and Lyn in neoplastic MC. In summary, our data show that a KIT-independent Lyn/Btk-driven signaling pathway contributes to growth and survival of neoplastic MC, and possibly to disease progression in SM. Our study also identifies dasatinib as a potent inhibitor of the Lyn/Btk pathway, which may have clinical implications and may explain some of the synergistic effects obtained with combinations of dasatinib and other KIT-targeting TK inhibitors in neoplastic MC.

Effects of the Mcl-1/Bcl-2 Inhibitor GX015-070 (Obatoclax®) on Growth and Viability of Canine and Human Neoplastic Mast Cells

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 861-861
Author(s):  
Barbara Peter ◽  
Karl J. Aichberger ◽  
Karoline V. Gleixner ◽  
Veronika Ferenc ◽  
Alexander Gruze ◽  
...  
Keyword(s):  
Mast Cells ◽  
Cell Line ◽  
Systemic Mastocytosis ◽  
Leukemia Cell ◽  
Leukemia Cell Line ◽  
Thymidine Uptake ◽  
Dependent Manner ◽  
Growth And Survival ◽  
Kit D816v

Abstract Mcl-1 is a Bcl-2 family-member that has been described to act anti-apoptotic in various myeloid neoplasms. We and others have recently shown that neoplastic mast cells (MC) in patients with systemic mastocytosis (SM) display Mcl-1, Bcl-2, and Bcl-xL. In the present study, we examined the effects of the Mcl-1/Bcl-2-targeting drug GX015-070 (obatoclax®; GeminX, Montréal, Quebéc, Canada) on growth and viability of primary neoplastic MC obtained from patients with SM (n=3), the human MC leukemia cell line HMC-1, and the canine mastocytoma cell line C2. Two HMC-1 subclones, one lacking KIT D816V (HMC- 1.1) and one expressing KIT D816V (HMC-1.2) were examined. As assessed by RT-PCR and immunostaining, primary neoplastic MC as well as HMC-1 cells (both subclones) were found to express Mcl-1 mRNA and the Mcl-1 protein in a constitutive manner, but did not express significant amounts of proapoptotic Bim. Transfection of HMC-1 cells with Mcl-1-specific siRNA resulted in reduced proliferation and increased apoptosis compared to cells transfected with a control siRNA. GX015-070 was found to inhibit 3H-thymidine uptake and thus proliferation in HMC-1 cells in a dose-dependent manner, with higher IC50 values obtained in HMC-1.2 cells (0.5 μM) compared to HMC-1.1 cells (0.05 μM). GX015-070 also inhibited the growth and survival in the canine mastocytoma cell line C2 (IC50: 0.5-1 μM). Moreover, GX015-070 was found to inhibit the proliferation of primary human neoplastic MC in all SM patients tested (IC50: 0.05-0.1 μM). We next attempted to combine obatoclax with a modulator of Mcl-1/Bim expression in MC, in order to enhance drug effects. Since Bim is degraded via the proteasome, we applied the proteasome inhibitor bortezomib. Whereas GX015-07 did not modulate the production/expression of Mcl-1 or Bim in HMC-1 cells, bortezomib was found to promote the expression of Bim in our Western blot experiments. In addition, bortezomib was found to suppress 3H-thymidine uptake in both HMC-1 subclones. Finally, bortezomib was found to cooperate with GX015-070 in producing apoptosis in HMC-1.1 cells, HMC-1.2 cells, and C2 cells. Together, our data show that the Mcl-1/Bcl-2-targeting drug GX015-070 is a potent inhibitor of in vitro growth and survival of canine and human neoplastic MC. Targeting of Mcl-1 in neoplastic MC alone or in combination with a Bim-regulator may be an interesting pharmacologic approach in advanced SM.

Bosutinib Blocks Lyn and Btk Activation and Synergizes with the KIT D816V-Targeting Drug Midostaurin in Inducing Apoptosis in Neoplastic Human Mast Cells.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 1717-1717
Author(s):  
Karoline Veronika Gleixner ◽  
Matthias Mayerhofer ◽  
Gregor Hörmann ◽  
Karina Schuch ◽  
Sabine Cerny-Reiterer ◽  
...  
Keyword(s):  
Mast Cells ◽  
Growth Inhibition ◽  
Research Funding ◽  
Systemic Mastocytosis ◽  
Leukemia Cell ◽  
Target Function ◽  
Leukemia Cell Line ◽  
Thymidine Uptake ◽  
Organ Systems ◽  
Kit D816v

Abstract Abstract 1717 Poster Board I-743 Advanced systemic mastocytosis (SM) is a malignant hematopoietic neoplasm characterized by destructive growth of neoplastic mast cells (MC) in various organ systems. In these patients, the response to conventional cytoreductive therapy is poor and the prognosis is grave. The D816V-mutated variant of c-KIT is found in most patients and is considered to be a major transforming oncoprotein in SM that leads to abnormal survival and growth of neoplastic MC. Therefore, agents interfering with the kinase activity of KIT D816V have been developed. One promising agent is midostaurin (PKC412). However, in most patients with advanced SM, therapy with midostaurin is not sufficient to induce long term remissions. In addition, midostaurin is unable to block all pro-oncogenic signaling molecules, such as Lyn and Btk, in neoplastic MC, suggesting that additional oncoproteins and survival factors may play a role in malignant transformation in SM, and that novel therapeutic strategies are required to block such KIT-independent oncogenic pathways. Especially Lyn and Btk have attracted attention as potential new targets in neoplastic MC. Bosutinib (SKI-606) is a novel multikinase inhibitor that targets a broad spectrum of kinases including Lyn and Btk. The aim of the current study was to evaluate the effect of bosutinib on neoplastic MC, and potential cooperative drug interactions between bosutinib and midostaurin. As assessed by 3H-thymidine uptake, bosutinib was found to inhibit the growth of the MC leukemia cell line HMC-1, including the HMC-1.1 subclone that lacks KIT D816V and HMC-1.2 cells expressing KIT D816V, with similar IC50 values (1-5 μM). Furthermore, bosutinib was found to induce apoptosis in both HMC-1 subclones. Growth-inhibitory and apoptosis-inducing effects of bosutinib were also seen in primary neoplastic MC obtained from the bone marrow of patients with SM (n=3). As assessed by phosphoblotting, bosutinib did not inhibit the autophosphorylation of mutant KIT in HMC-1 cells, but was found to completely inhibit the phosphorylation of Lyn and Btk. To confirm the target-function of Lyn and Btk in neoplastic MC, siRNA experiments were performed. Knockdown of Lyn or Btk resulted in induction of apoptosis and growth-inhibition in HMC-1 cells. We next attempted to exploit target-specific and complementing effects of midostaurin and bosutinib by combining both substances. As expected, combined application of bosutinib and midostaurin resulted in a complete inhibition of phosphorylation of KIT, Lyn, and Btk in HMC-1.1 and HMC-1.2 cells. We were also able to show that bosutinib synergizes with midostaurin in inducing apoptosis in both HMC-1 subclones. Synergistic effects were also observed when combining midostaurin with Lyn- or Btk-siRNA. Together, we have identified Lyn and Btk as novel KIT-independent survival molecules in neoplastic MC. Inhibition of these kinases by siRNA-knockdown or by bosutinib leads to growth-inhibition and apoptosis. Synergistic pro-apoptotic effects were observed with the combination “bosutinib + midostaurin”, suggesting that simultaneous targeting of KIT and Lyn/Btk may be a powerful strategy to counteract the survival of neoplastic MC. This drug combination may therefore be an interesting approach to overcome drug-resistance in advanced forms of SM. Disclosures Valent: Bristol Myers Squibb: Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding.

Identification of proapoptotic Bim as a tumor suppressor in neoplastic mast cells: role of KIT D816V and effects of various targeted drugs

Blood ◽  
2009 ◽  
Vol 114 (26) ◽  
pp. 5342-5351 ◽  
Author(s):  
Karl J. Aichberger ◽  
Karoline V. Gleixner ◽  
Irina Mirkina ◽  
Sabine Cerny-Reiterer ◽  
Barbara Peter ◽  
...  
Keyword(s):  
Mast Cells ◽  
Tumor Suppressor ◽  
Systemic Mastocytosis ◽  
Leukemia Cell ◽  
Myeloid Neoplasm ◽  
Myeloid Neoplasms ◽  
Leukemia Cell Lines ◽  
Survival And Growth ◽  
Kit D816v

Abstract Systemic mastocytosis (SM) is a myeloid neoplasm involving mast cells (MCs) and their progenitors. In most cases, neoplastic cells display the D816V-mutated variant of KIT. KIT D816V exhibits constitutive tyrosine kinase (TK) activity and has been implicated in increased survival and growth of neoplastic MCs. Recent data suggest that the proapoptotic BH3-only death regulator Bim plays a role as a tumor suppressor in various myeloid neoplasms. We found that KIT D816V suppresses expression of Bim in Ba/F3 cells. The KIT D816–induced down-regulation of Bim was rescued by the KIT-targeting drug PKC412/midostaurin. Both PKC412 and the proteasome-inhibitor bortezomib were found to decrease growth and promote expression of Bim in MC leukemia cell lines HMC-1.1 (D816V negative) and HMC-1.2 (D816V positive). Both drugs were also found to counteract growth of primary neoplastic MCs. Furthermore, midostaurin was found to cooperate with bortezomib and with the BH3-mimetic obatoclax in producing growth inhibition in both HMC-1 subclones. Finally, a Bim-specific siRNA was found to rescue HMC-1 cells from PKC412-induced cell death. Our data show that KIT D816V suppresses expression of proapoptotic Bim in neoplastic MCs. Targeting of Bcl-2 family members by drugs promoting Bim (re)-expression, or by BH3-mimetics such as obatoclax, may be an attractive therapy concept in SM.

PKC412 inhibits in vitro growth of neoplastic human mast cells expressing the D816V-mutated variant of KIT: comparison with AMN107, imatinib, and cladribine (2CdA) and evaluation of cooperative drug effects

Blood ◽  
2006 ◽  
Vol 107 (2) ◽  
pp. 752-759 ◽  
Author(s):  
Karoline V. Gleixner ◽  
Matthias Mayerhofer ◽  
Karl J. Aichberger ◽  
Sophia Derdak ◽  
Karoline Sonneck ◽  
...  
Keyword(s):  
Mast Cells ◽  
Systemic Mastocytosis ◽  
Drug Effects ◽  
Kit Mutation ◽  
Growth Inhibitory ◽  
Ic50 Values ◽  
Tk Inhibitors ◽  
Mast Cell Leukemia ◽  
Kit D816v

AbstractIn most patients with systemic mastocytosis (SM), including aggressive SM and mast cell leukemia (MCL), neoplastic cells express the oncogenic KIT mutation D816V. KIT D816V is associated with constitutive tyrosine kinase (TK) activity and thus represents an attractive drug target. However, imatinib and most other TK inhibitors fail to block the TK activity of KIT D816V. We show that the novel TK-targeting drugs PKC412 and AMN107 counteract TK activity of D816V KIT and inhibit the growth of Ba/F3 cells with doxycycline-inducible expression of KIT D816V as well as the growth of primary neoplastic mast cells and HMC-1 cells harboring this KIT mutation. PKC412 was a superior agent with median inhibitory concentration (IC50) values of 50 to 250 nM without differences seen between HMC-1 cells exhibiting or lacking KIT D816V. By contrast, AMN107 exhibited more potent effects in KIT D816V- HMC-1 cells. Corresponding results were obtained with Ba/F3 cells exhibiting wild-type or D816V-mutated KIT. The growth-inhibitory effects of PKC412 and AMN107 on HMC-1 cells were associated with induction of apoptosis and down-regulation of CD2 and CD63. PKC412 was found to cooperate with AMN107, imatinib, and cladribine (2CdA) in producing growth inhibition in HMC-1, but synergistic drug interactions were observed only in cells lacking KIT D816V. Together, PKC412 and AMN107 represent promising novel agents for targeted therapy of SM. (Blood. 2006;107: 752-759)

Dasatinib Inhibits the Growth of Neoplastic Human Eosinophils (EOL-1) through Targeting of FIP1L1-PDGFRα.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 3559-3559
Author(s):  
Christian Baumgartner ◽  
Karoline V. Gleixner ◽  
Alexander Gruze ◽  
Puchit Samorapoompichit ◽  
Harald Esterbauer ◽  
...  
Keyword(s):  
Kinase Inhibitor ◽  
Systemic Mastocytosis ◽  
Leukemia Cell ◽  
Malignant Cell ◽  
Organ Damage ◽  
Leukemia Cell Line ◽  
Dependent Manner ◽  
Growth And Survival ◽  
Chronic Eosinophilic Leukemia ◽  
Dose Dependent

Abstract Chronic eosinophilic leukemia (CEL) is a myeloproliferative disorder characterized by molecular and/or cytogenetic evidence of monoclonality of eosinophils, sustained marked eosinophilia, and consecutive organ damage. In a majority of patients with CEL with or without associated mastocytosis, the transforming mutation FIP1L1-PDGFRα and the related CHIC2 deletion is found. The respective oncoprotein, FIP1L1-PDGFRα, is considered to play a major role in malignant cell growth in CEL. The tyrosine kinase (TK) inhibitor imatinib (STI571) has been described to counteract the TK activity of FIP1L1-PDGFRα in most patients, and has been introduced as a novel effective therapy in CEL. However, not all patients with CEL show a response to imatinib. Therefore, several attempts have been made to identify other TK inhibitors that counteract growth of neoplastic eosinophils in CEL. We provide evidence that dasatinib, a multi-targeted kinase inhibitor, blocks the growth and survival of EOL-1, an eosinophil leukemia cell line carrying FIP1L1-PDGFRα. The effects of dasatinib on proliferation of EOL-1 cells were dose-dependent, with an IC50 of 0.5–1 nM, that was found to be in the same range compared to IC50 values produced by imatinib. Dasatinib was also found to induce apoptosis in EOL-1 cells in a dose-dependent manner (IC-50: 1–10 nM). The apoptosis-inducing effects of dasatinib on EOL-1 cells were demonstrable by light microscopy, flow cytometry, and by a Tunel assay. To further examine the mechanism of growth inhibition induced by dasatinib in neoplastic eosinophils, Western blot experiments were performed using antibodies directed against phosphorylated or total PDGFRα. In these experiments, we were able to show that dasatinib at 1 μM completely blocks the phosphorylation of FIP1L1-PDGFRα in EOL-1 cells. In summary, our data show that dasatinib inhibits the growth of leukemic eosinophils through targeting of the TK activity of the disease-related oncoprotein FIP1L1-PDGFRα. Based on this observation, dasatinib may be considered as a new interesting treatment option for patients with CEL. As dasatinib is also known to block various KIT mutants as well as wild type KIT, such therapy may also be of interest for patients who have systemic mastocytosis (SM) with an associated CEL (SM-CEL).

Tyrosine phosphorylation modulates binding preference to cyclin-dependent kinases and subcellular localization of p27Kip1 in the acute promyelocytic leukemia cell line NB4

Blood ◽  
2006 ◽  
Vol 107 (3) ◽  
pp. 1133-1140 ◽  
Author(s):  
Christian Kardinal ◽  
Marc Dangers ◽  
Angelika Kardinal ◽  
Alexandra Koch ◽  
Dominique Tobias Brandt ◽  
...  
Keyword(s):  
Subcellular Localization ◽  
Cell Line ◽  
Tyrosine Phosphorylation ◽  
Acute Promyelocytic Leukemia ◽  
Leukemia Cell ◽  
Promyelocytic Leukemia ◽  
Leukemia Cell Line ◽  
Acute Promyelocytic Leukemia Cell ◽  
Promyelocytic Leukemia Cell Line

AbstractWe have investigated the role of tyrosine phosphorylation of the cyclin-dependent kinase (cdk) inhibitor p27Kip1 using the acute promyelocytic leukemia cell line NB4 together with granulocyte colony-stimulating factor (G-CSF). Short-term G-CSF stimulation resulted in a rapid tyrosine dephosphorylation of p27Kip1 accompanied by a change in its binding preferences to cdks. On G-CSF stimulation, p27Kip1 dissociated from cdk4 and associated with cdk2. Binding assays with recombinant p27Kip1 confirmed that tyrosine-phosphorylated p27Kip1 preferentially bound to cdk4, whereas unphosphorylated protein preferentially associated with cdk2. In addition, studies with p27Kip1 point mutations revealed a decisive role of Tyr88 and Tyr89 in binding to cdk4. Furthermore, phosphorylation of Tyr88 and Tyr89 was accompanied by strong nuclear translocation of p27Kip1. Taken together, this report provides the first evidence that tyrosine phosphorylation of p27Kip1 plays a crucial role in binding to cdks and its subcellular localization. Moreover, both effects are mediated by application of G-CSF.

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.

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.

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