Cem Akin

Standards and standardization in mastocytosis: Consensus Statements on Diagnostics, Treatment Recommendations and Response Criteria

Although a classification for mastocytosis and diagnostic criteria are available, there remains a need to define standards for the application of diagnostic tests, clinical evaluations, and treatment responses. To address these demands, leading experts discussed current issues and standards in mastocytosis in a Working Conference. The present article provides the resulting outcome with consensus statements, which focus on the appropriate application of clinical and laboratory tests, patient selection for interventional therapy, and the selection of appropriate drugs. In addition, treatment response criteria for the various clinical conditions, disease‐specific symptoms, and specific pathologies are provided. Resulting recommendations and algorithms should greatly facilitate the management of patients with mastocytosis in clinical practice, selection of patients for therapies, and the conduct of clinical trials.

Characterization of novel stem cell factor responsive human mast cell lines LAD 1 and 2 established from a patient with mast cell sarcoma/leukemia; activation following aggregation of FcεRI or FcγRI

Two novel stem cell factor (SCF) dependent human mast cell lines, designated LAD 1 and 2, were established from bone marrow aspirates from a patient with mast cell sarcoma/leukemia. LAD 1 and 2 cells have the ultrastructural features of human mast cells, and express FcepsilonRI, CD4, 9, 13, 14, 22, 31, 32, 45, 64, 71, 103, 117, 132, CXCR4 (CD184), CCR5 (CD195); and intracytoplasmic histamine, tryptase and chymase. LAD 1 and 2 do not exhibit activating mutations at codon 816 of c-kit. Both LAD 1 and 2 release beta-hexosaminidase following FcepsilonRI or FcgammaRI aggregation. The availability of these cell lines offers an unparalleled circumstance to examine the biology of human mast cells.

Definitions, Criteria and Global Classification of Mast Cell Disorders with Special Reference to Mast Cell Activation Syndromes: A Consensus Proposal

Activation of tissue mast cells (MCs) and their abnormal growth and accumulation in various organs are typically found in primary MC disorders also referred to as mastocytosis. However, increasing numbers of patients are now being informed that their clinical findings are due to MC activation (MCA) that is neither associated with mastocytosis nor with a defined allergic or inflammatory reaction. In other patients with MCA, MCs appear to be clonal cells, but criteria for diagnosing mastocytosis are not met. A working conference was organized in 2010 with the aim to define criteria for diagnosing MCA and related disorders, and to propose a global unifying classification of all MC disorders and pathologic MC reactions. This classification includes three types of ‘MCA syndromes’ (MCASs), namely primary MCAS, secondary MCAS and idiopathic MCAS. MCA is now defined by robust and generally applicable criteria, including (1) typical clinical symptoms, (2) a substantial transient increase in serum total tryptase level or an increase in other MC-derived mediators, such as histamine or prostaglandin D2, or their urinary metabolites, and (3) a response of clinical symptoms to agents that attenuate the production or activities of MC mediators. These criteria should assist in the identification and diagnosis of patients with MCAS, and in avoiding misdiagnoses or overinterpretation of clinical symptoms in daily practice. Moreover, the MCAS concept should stimulate research in order to identify and exploit new molecular mechanisms and therapeutic targets.

Effects of tyrosine kinase inhibitor STI571 on human mast cells bearing wild-type or mutated c-kit

OBJECTIVE STI571 is a tyrosine kinase inhibitor which inhibits the kinase activity of kit, the receptor for stem cell factor (SCF). Because activating mutations of c-kit affecting codon 816 are associated with human mast cell neoplasms, we determined whether STI571 exerted a similar cytotoxic effect on neoplastic and normal human mast cells. METHODS We investigated the effect of addition of STI571 in increasing concentrations (0.01 to 10 micromolar) to two HMC-1 human mast cell leukemia cell lines carrying two different activating c-kit mutations in codons 816 or 560, as well as the effect of the drug on short-term bone marrow cultures obtained from patients who carry a mutated codon 816 or wild-type c-kit. RESULTS STI571 failed to inhibit the growth of HMC-1(560,816) cells bearing a codon 816 mutation but effectively suppressed the proliferation of HMC-1(560) carrying c-kit with the wild-type codon 816. STI571 did not induce preferential killing of neoplastic bone marrow mast cells in short-term cultures from patients bearing a codon 816 c-kit mutation. In contrast, STI571 caused a dramatic reduction in mast cells in patients without codon 816 c-kit mutations. CONCLUSION These results suggest that STI571, while effectively killing mast cells with wild-type c-kit, did not show preferential cytotoxicity to neoplastic human mast cells and thus may not be effective in the treatment of human systemic mastocytosis associated with codon 816 c-kit mutations.

Diagnosis and treatment of systemic mastocytosis: state of the art

Mast cells are tissue-fixed cells originating from uncommitted and mast cell-committed haematopoietic progenitors (Kitamura et al, 1981; Kirshenbaum et al, 1992; Agis et al, 1993; Rottem et al, 1994; Kempuraj et al, 1999). Mast cellcommitted progenitors co-express CD13 and KIT with CD34 (Kirshenbaum et al, 1999) and are detectable in the bone marrow as well as in the peripheral blood (Valent et al, 1992; Rottem et al, 1994; Valent, 1994). Homing, differentiation and maturation of mast cell progenitor cells are regulated by a complex network of growth factors, receptors and other antigens (Galli, 1990; Valent, 1994). The most important growth factor for human mast cells appears to be stem cell factor (SCF) (Irani et al, 1992; Kirshenbaum et al, 1992; Valent et al, 1992; Mitsui et al, 1993). This cytokine is a natural ligand for the c-kit proto-oncogene product, KIT, a tyrosine kinase receptor expressed on the surface of precommitted myelopoietic progenitor cells, mast cell-committed progenitor cells as well as mature mast cells (Galli et al, 1993; Simmons et al, 1994; Valent, 1994). Based on their unique phenotype and distinct functional properties, mast cells represent a distinct myeloid cell lineage within lympho-haematopoietic tissues. Likewise, mast cells express a unique composition of CD antigens and granular mediators when compared with other myeloid cells (Schwartz, 1985; Valent et al, 1989; Valent & Bettelheim, 1992; Agis et al, 1996) (Table I). Moreover, in contrast to blood basophils and other myeloid cells, mast cells exhibit an extremely long life span in vivo ranging from several months to years (Galli, 1990; Födinger et al, 1994). In contrast to other haematopoietic cells, mast cells produce substantial amounts of histamine and heparin and express the high-affinity IgE receptor on their surface (Ishizaka & Ishizaka, 1984; Schwartz, 1985; Galli, 1990). The concept that mast cells represent a unique myeloid lineage is in line with the notion that systemic mastocytosis (SM) is a distinct haematopoietic (myeloid) neoplasm with unique pathogenetic and clinical features (Lennert & Parwaresch, 1979; Parwaresch et al, 1985; Metcalfe, 1991a; Valent, 1996). The clonal nature of the disease has been reinforced by the association with the somatic c-kit mutation Asp-816-Val (Nagata et al, 1995; Longley et al, 1996, 1999; Buttner et al, 1998). This transforming mutation is detectable in the bone marrow (mast cells) in a majority of patients with SM but usually is not found in other myeloid neoplasms (Fritsche-Polanz et al, 2001). Remarkably, in a group of patients with (advanced) SM, the c-kit mutation Asp-816-Val is detectable not only in mast cells but also in other haematopoietic lineages, including blood monocytes (Akin et al, 2000a; Sotlar et al, 2000; Yavuz et al, 2002). Based on this notion and several clinical observations, SM can be regarded as a myeloproliferative disorder. In line with this concept, patients with SM are at a certain risk of acquiring a secondary myeloid leukaemia (Travis et al, 1988a,b; Horny et al, 1990a; Lawrence et al, 1991; Sperr et al, 2000). In the management of patients with SM, two major problems have to be faced. The first is mediator release from mast cells with respective clinical symptoms that can be observed frequently in these patients (Horan & Austen, 1991; Metcalfe, 1991a; Austen, 1992; Valent, 1996). In fact, mast cells store (in their granules) or generate a number of vasoactive mediators [histamine, tumour necrosis factor-a (TNFa), vascular endothelial growth factor (VEGF), leukotrienes, prostaglandin D2 (PGD2)] and other biologically active molecules (interleukins, proteases, heparin) (Roberts et al, 1980; Lewis & Austen, 1981; Serafin & Austen, 1987; Burd et al, 1989; Plaut et al, 1989; WodnarFilipowicz et al, 1989; Gordon et al, 1990; Gordon & Galli, 1990) (Table II). In response to activating stimuli, mast cells can generate and ⁄ or release their mediator substances (Lewis & Austen, 1981; Ishizaka & Ishizaka, 1984; Schwartz, 1985; Burd et al, 1989; Plaut et al, 1989; Wodnar-Filipowicz et al, 1989; Gordon et al, 1990). Resulting clinical symptoms include headache, flushing, pruritus, diarrhoea, vascular instability, hypotension and shock (Austen, 1992) (Table II). Such symptoms may be grave and life threatening, especially in patients with SM who also have a co-existing disease predisposing for mediator secretion (allergies). The second management problem in SM results from the uncontrolled (aggressive) growth and infiltration of mast cells in diverse organs with consecutive organopathy (Lennert & Parwaresch, 1979; Parwaresch et al, 1985; Metcalfe, 1991a; Valent, 1996). Such organopathies are seen in patients with aggressive systemic mastocytosis (ASM), mast cell leukaemia (MCL) and in a group of patients with an associated clonal haematological nonmast cell lineage disease (SM-AHNMD), but not in those with indolent systemic mastocytosis (ISM). The organ systems most frequently affected in patients with aggressive Correspondence: Peter Valent, Department of Internal Medicine I, Division of Haematology & Haemostaseology, University of Vienna, Währinger Gürtel 18–20, A-1090 Vienna, Austria. E-mail: peter.valent@akh-wien.ac.at British Journal of Haematology, 2003, 122, 695–717

Aggressive systemic mastocytosis and related mast cell disorders: current treatment options and proposed response criteria

Aggressive systemic mastocytosis (ASM) is a clonal mast cell disease characterized by progressive growth of neoplastic cells in diverse organs leading to organopathy. The organ-systems most frequently affected are the bone marrow, skeletal system, liver, spleen, and the gastrointestinal tract. Respective clinical findings (so called C-Findings) include cytopenias, osteolysis (or osteoporosis) with pathologic fractures, hepatosplenomegaly with impaired liver function and ascites, and malabsorption. During the past decade several treatment strategies for ASM have been proposed. One promising approach may be combination treatment with interferon-alpha (IFN-alpha) and glucocorticoids. This concept has been based on the notion that systemic mastocytosis involves multilineage hematopoietic progenitors indicating a relationship with myeloproliferative disorders. However, relatively little is known about the quality of responses to IFN-alpha in ASM and the actual response rates. This may be due in part to the fact that disease criteria for ASM have only recently been established, and no response criteria are available. In the current article, we propose surrogate markers and treatment response criteria for patients with ASM. In addition, we have applied these criteria retrospectively to ASM patients described in the available literature. In these analyses, the calculated rate of major response (=complete resolution of C-Findings) in patients treated with IFN-alpha (with or without additional glucocorticoids) amounts to approximately 21%. This confirms clinical activity in some patients for this drug-combination, but also points to the need to search for more effective strategies in the treatment of patients with aggressive mast cell disorders.

Mastocytosis: current concepts in diagnosis and treatment.

Abstract. Mastocytosis consists of a group of disorders characterized by a pathologic increase in mast cells in tissues including skin, bone marrow, liver, spleen, and lymph nodes. Mastocytosis is a rare disease. Because of this, general practitioners have limited exposure to its clinical manifestations, diagnosis, classification, and management. Diagnosis of mastocytosis is suspected on clinical grounds and is established by histopathologic examination of involved tissues such as skin and bone marrow. The most common clinical sign of mastocytosis is the presence of typical skin lesions of urticaria pigmentosa. Most patients experience symptoms related to mast cell mediator release, and prevention of the effects of these mediators on tissues constitutes the major therapeutic goal in the management of mastocytosis. Despite recent advances in knowledge about the pathophysiology, diagnosis, and classification of mastocytosis, a curative treatment for mastocytosis does not now exist. Management of patients within all categories of mastocytosis includes: (1) a careful counseling of patients (parents in pediatric cases) and care providers, (2) avoidance of factors triggering acute mediator release, (3) treatment of acute mast cell mediator release, (4) treatment of chronic mast cell mediator release, and if indicated (5) an attempt to treat organ infiltration by mast cells. The goal of this manuscript is to provide an overview of the mediators produced and released by mast cells, the diagnostic criteria for the different variants of mastocytosis, and the treatment options currently available.

Analysis of the surface expression of c-kit and occurrence of the c-kit Asp816Val activating mutation in T cells, B cells, and myelomonocytic cells in patients with mastocytosis

OBJECTIVE The Asp816Val c-kit activating mutation is detectable in the peripheral blood cells of some patients with mastocytosis and in lesional skin biopsies obtained from adult patients with urticaria pigmentosa. These observations led to the conclusion that this mutation is present in mast cells and mast cell precursors that express c-kit. However, the distribution of the Asp816Val mutation among hematopoietic lineages is unknown. To determine the distribution of the Asp816Val mutation among hematopoietic lineages and to explore its relationship to clinical disease, we examined cells bearing differentiation markers for myelomonocytic cells as well as T and B lymphocytes, in both peripheral blood and bone marrow obtained from patients with mastocytosis. MATERIALS AND METHODS The presence of Asp816Val c-kit mutation in cells magnetically sorted from peripheral blood or bone marrow according to surface differentiation markers was studied by reverse transcriptase polymerase chain reaction (RT-PCR) restriction fragment length polymorphism (RFLP) analysis. The surface expression of c-kit was determined by flow cytometry. RESULTS The mutation was detectable by RT-PCR in at least one cell lineage in the bone marrow in 7 of 7 patients examined and in the peripheral blood of 11 of 11 adult patients with urticaria pigmentosa and indolent disease. The mutation was identified most frequently in B cells and myeloid cells. Flow cytometric analysis demonstrated that the differentiated cells expressing mutated c-kit were negative for surface KIT. CONCLUSION These results are consistent with the conclusion that the c-kit Asp816Val mutation occurs in an early progenitor cell and is carried by myelomonocytic cells, T cells, and B cells in addition to mast cells. However, unlike mast cells, these myelomonocytic cells, T cells, and B cells do not concomitantly express surface c-kit and thus may be less susceptible to the effects of this mutation.

Mast Cells, Mastocytosis, and Related Disorders

This article provides an overview of recent developments concerning the physiology and pathobiology of mast cells and discusses current diagnostic and therapeutic approaches to mast-cell disorders, with an emphasis on mastocytosis.

Phase II Study of Dasatinib in Philadelphia Chromosome–Negative Acute and Chronic Myeloid Diseases, Including Systemic Mastocytosis

Purpose: Molecular characterization of Philadelphia chromosome–negative (Ph−) chronic myeloproliferative disorders, such as systemic mastocytosis (SM), has provided a clear rationale for investigating novel targeted therapies. The tyrosine kinase (TK) inhibitor dasatinib is 325-fold more potent against Bcr-Abl TK than imatinib in vitro, significantly inhibiting wild-type KIT and platelet-derived growth factor receptor β TKs, and is active against cells carrying the mutant KIT-D816V gene. Experimental Design: In this phase 2, open-label study, the efficacy of dasatinib (140 mg/d) was investigated in 67 patients with various Ph− myeloid disorders, including SM (n = 33; 28 KIT-D816V positive). Results: The overall response rate to dasatinib in patients with SM was 33%. Only two patients, one with SM-myelofibrosis and one with SM-chronic eosinophilic leukemia, achieved complete response (elimination of mastocytosis) lasting for 5 and 16 months, respectively. Both patients were negative for KIT-D816V mutation, had low tryptase levels, abnormal WBC counts, and anemia, and had failed prior therapy with erythropoietin. Additional nine SM patients had symptomatic response, lasting 3 to 18+ months. Complete responses were achieved in two other patients (acute myeloid leukemia and hypereosinophilic syndrome). No responses were observed among patients with myelodysplastic syndromes and primary myelofibrosis. The majority of adverse events were grade 1/2. Conclusion: These data show that dasatinib therapy may benefit a selected group of SM patients, primarily by improving their symptoms, but it does not eliminate the disease in the patients with KIT-D816V mutation.