Cases Of Mastocytosis Research Articles

Sensitive and reliable detection of KIT p.D816V mutation in decalcified archival bone marrow trephines.

The majority of mastocytosis cases are characterized by an activating mutation in the KIT gene in codon 816. The detection of this alteration is of importance for proper diagnostic workup. Therefore, reliable and sensitive methods for the detection of KIT Codon 816 hotspot mutations in various types of patient samples are required. Since mutated cancer genes are often overexpressed, we evaluated the feasibility and sensitivity of KIT p.D816V detection by analysing mRNA/cDNA instead of genomic DNA. From 80 bone marrow trephines harboring a KIT p.D816 mutation, seven were only mutated by mRNA/cDNA pyrosequencing and 11 only by digital PCR analysis of genomic DNA. These results clearly demonstrate that detection of clinically relevant mutations in mRNA extracted from routinely processed decalcified archival bone marrow trephines is not only possible in a reliable fashion but under many circumstances advantageous. This enables the direct correlation of genomic data with high-quality morphological evaluation.

A comparison of mast cells in skin biopsies of cutaneous mastocytosis with other inflammatory dermatoses: A study of 33 cases.

Histopathologic criteria for diagnosis of cutaneous mastocytosis include 20 mast cells per high-power field or clusters of 15 mast cells. We aimed to determine the specificity of these criteria for cutaneous mastocytosis in comparison with inflammatory disorders of mast cell activation. Twenty-six cases of spongiotic dermatitis or urticaria were identified from 2021 to 2022. Recuts were stained with mast cell tryptase and slides were reviewed for the presence of 20 mast cells per high-power field and for clusters of 15 mast cells. In addition, seven cases of mastocytosis were reviewed for the same criteria. Twelve of 26 cases (46.1%) of spongiotic dermatitis/urticaria had at least 20 mast cells per high-power field. Three of 26 cases (11.5%) of spongiotic dermatitis/urticaria had a cluster of 15 mast cells. Six of seven cases (85.7%) of mastocytosis had at least 20 mast cells per high-power field; four of seven cases (57.1%) of mastocytosis had a cluster of 15 mast cells. In our study, the finding of 20 mast cells per high-power field was nonspecific as a single criterion for cutaneous mastocytosis. The finding of clusters of 15 mast cells was more specific but not sensitive.

Clinical and epidemiological features of cutaneous mastocytosis among the pediatric population of Moscow

BACKGROUND: Cutaneous mastocytosis is a rare disease that primarily develops in childhood.
 AIM: This study aimed to determine the clinical and epidemiological characteristics and frequency of detection of cutaneous mastocytosis among children in Moscow.
 MATERIALS AND METHODS: A single-center epidemiological retrospective study was conducted. Data from Form № 12 of the federal statistical observation "Information on the number of diseases registered in patients living in the service area of a medical organization" were used as a statistical source of information. To calculate the incidence rate in intensive indicators per 100 thousand population, data on the population of Moscow for the period 2019–2022 were used.
 RESULTS: Over the period 2019–2022, a gradual trend towards an increase in the number of newly identified cases of cutaneous mastocytosis in children and adolescents in Moscow was revealed. Number of initial applications from children and adolescents (0–17 years old) for this period increased by 4.8 times. The share of cutaneous mastocytosis in the structure of skin diseases and congenital anomalies (malformations) of the skin increases every year. In 2019, for every 1,834 pediatric visits (age category 0–17 years) regarding skin diseases, there was 1 case of mastocytosis; in 2020 the ratio was 1,863:1; in 2021 ― 491:1; in 2022 ― 376:1. Since 2019, there has been an increase in the primary incidence of cutaneous mastocytosis from 3.63 cases per 100,000 child population to 16.61 cases per 100,000 child population in 2022.
 CONCLUSION: The increase in incidence in the pediatric population and the share of cutaneous mastocytosis in the structure of skin diseases in recent years demonstrates the need to generate interest and attention of the medical community to this pathology.

The role of heredity in cutaneous mastocytosis and C-KIT gene mutation

Introduction. Mastocytosis is a rare disease associated with the proliferation of clonal mast cells in the skin and other organs and systems. In the last decade, studies have appeared on the role of genetic factors in the development of the disease. According to their results, the mode of inheritance of mastocytosis was determined to be autosomal dominant with incomplete penetrance of the gene. Aim. To analyze the frequency of familial cases of mastocytosis and describe a familial case of monomorphic type maculopapular cutaneous mastocytosis (monoPPCM). Results. A family history was present in 6.7% of 341 children with mastocytosis. The article presents a description of the clinical, laboratory and instrumental features of monoPPCM in cousins (paternal kinship). The course of mastocytosis in a patient with the KIT D816V mutation in the peripheral blood was more severe than in her cousin without the mutation. Conclusion. The family case of monoMPCM presented in the article demonstrated the need for careful examination and dynamic monitoring of children with this pathology. The diagnosis of monomorphic (“adult”) type of MPCM is associated with a long course and the risk of developing systemic mastocytosis. Determining KIT mutations is necessary not only for prognosis, but also for developing a strategy for monitoring and treating the patient.

Clinical impact of the TPSAB1 genotype in mast cell diseases: A REMA study in a cohort of 959 individuals.

A close association between hereditary alpha-tryptasemia (HAT) and mast cell (MC) disorders has been previously reported. However, the relationship between HAT and the diagnostic subtypes and clinical features of MC disorders still remains to be established. To determine the prevalence of HAT in healthy donors (HD) vs patients with different diagnostic subtypes of MC activation syndromes (MCAS) and mastocytosis, and its relationship with the clinical behavior of the disease. A total of 959 subjects were studied including 346 healthy donors (HD), 464 mastocytosis, and 149 non-clonal MCAS patients. Molecular studies to assess the TPSAB1 genotype were performed, and data on serum baseline tryptase (sBT) and basal MC-mediator release episodes and triggers of anaphylaxis were collected. HAT was detected in 15/346 (4%) HD versus 43/149 (29%) non-clonal MCAS and 84/464 (18%) mastocytosis cases. Among mastocytosis, HAT was more frequently found in patients with MC-restricted KITD816V (21% vs. 10% among multilineage KITD816V patients; p = .008). Overall, median sBT was higher in cases presenting with HAT (28.9 vs. 24.5 ng/mL; p = .008), while no significant differences in sBT were observed among HAT+ mastocytosis patients depending on the presence of 1 vs. ≥2 extra copies of the α-tryptase gene (44.1 vs. 35.2 ng/mL, p > .05). In turn, anaphylaxis was more frequently observed in HAT+ versus HAT- mastocytosis patients (76% vs. 65%; p = .018), while HAT+ and HAT- patients who did not refer anaphylaxis as the presenting symptom (n = 308) showed a similar prevalence of subsequent anaphylaxis (35% vs. 36%, respectively). The frequency of HAT in MC disorders varies according to the diagnostic subtype of the disease. HAT does not imply a higher risk (and severity) of anaphylaxis in mastocytosis patients in whom anaphylaxis is not part of the presenting symptoms of the disease.

Comprehensive mastocytosis data analysis from a single center

Mastocytosis is a very rare disorder and is divided into three prognostically distinct variants by World Health Organization: Cutaneous mastocytosis (CM), systemic mastocytosis (SM), and mast cell sarcoma or localized mast cell (MC) tumors. The wide range of complaints may cause patients to consult various clinics, with resulting mis- or underdiagnosis. Therefore, cooperation between different subspecialties is of paramount importance. In this article, we have compiled 104 adult mastocytosis cases diagnosed and followed in our Hematology and other clinics. 86 (82.7%) of 104 patients had systemic mastocytosis. Osteoporosis, disease-related complications, and secondary malignancies are important topics in this group. We know that indolent form has great survival. But smoldering or aggressive mastocytosis has a poor prognosis. CM and indolent SM have a significantly better prognosis compared to aggressive SM (p < 0.001). We found that the presence of more than 25% of mast cells in the bone marrow, the presence of concomitant marrow dysplasia, and the presence of disease-related complications affect survival (p < 0.001). In addition to the WHO classification, the IPSM scoring system is indicative of the prognosis in this rare disease.

INFANTILE AGGRESSIVE SYSTEMIC MASTOCYTOSIS TREATED WITH ORAL MIDOSTAURIN

<h3>Introduction</h3> Systemic mastocytosis accounts for less than 10% of all pediatric mastocytosis cases. Midostaurin, a cytoreductive multi-kinase inhibitor, is approved for use in adult systemic mastocytosis. There are no FDA-approved cytoreductive therapies for pediatric patients. <h3>Case Description</h3> A 3-month-old male presented with diffuse pruritic patches and hepatosplenomegaly, in the setting of a markedly elevated tryptase of 187 ng/mL (<11.4mg/mL). Bone marrow biopsy showed multifocal mast cell infiltrates with a subset being spindle shaped. Mast cells immunostaining was positive for tryptase, CD117, CD2 and CD30. Skin biopsy revealed superficial dermal mast cell infiltration. Serum KITD816V mutation was positive. There were no cytopenias. The patient was started on a regimen of H1 and H2 antihistamines and oral cromolyn. Three months later, he presented with fever and progressive hepatosplenomegaly. Labs were notable for: increased tryptase (234 ng/mL), anemia (hemoglobin 9.3 g/dL), mild thrombocytopenia (133 k/uL)<i>,</i> elevated prothromobin time (15.9 sec [11.7-14.7 sec]) and low albumin (2.7 g/dL [2.9-5.5g/dL]). Local IRB approval and FDA emergency expanded use was obtained for oral midostaurin 30mg/m² every 12 hours with weekly monitoring of CBC and tryptase. Within 3 weeks of starting, the tryptase declined to 129 ng/mL and the patient had near complete resolution of head and neck lesions with reduction in hepatosplenomegaly. <h3>Discussion</h3> To our knowledge this is the second case of infantile systemic mastocytosis where oral midostaurin rapidly decreased serum tryptase and improved clinical symptoms without notable adverse effects. This treatment will be continued until normalization of serum tryptase unless adverse effects develop.

Histopathological characteristics are instrumental to distinguish monomorphic from polymorphic maculopapular cutaneous mastocytosis in children.

BackgroundMastocytosis is characterized by the accumulation of mast cells (MCs) in the skin or other organs, and can manifest at any age. A significant number of paediatric mastocytosis cases persist after puberty. In particular, monomorphic maculopapular cutaneous mastocytosis (mMPCM) is often persistent and associated with systemic mastocytosis. However, clinical differentiation of MPCM from polymorphic (p)MPCM can be difficult.AimTo identify histopathological features that can help to distinguish mMPCM from other subtypes of paediatric mastocytosis.MethodsThis was a retrospective study using skin biopsies from patients with any subtype of mastocytosis. The localization and density of the MC infiltrate, MC morphology and expression of aberrant markers were evaluated and correlated with clinical characteristics.ResultsIn total, 33 biopsies were available for evaluation from 26 children [(10 with mMPCM, 5 with mastocytoma, 3 with diffuse cutaneous mastocytosis (DCM), 8 with pMPCM)] and 7 adults with MPCM. The MC number was increased in all patients, but was higher in children than adults (P < 0.01). The presence of mMPCM was associated with sparing of the papillary dermis from MC infiltration, whereas MC density in the papillary dermis was highest in pMPCM and DCM (P < 0.01). The positive predictive value of the presence of a reticular MC infiltrate for mMPCM was 72.7% (95% CI 51.4–87.0), and the negative predictive value was 83.3% (95% CI 42.2–97.2). There were no relevant differences in the expression of CD2, CD25 or CD30 between the different subtypes.ConclusionSkin histopathology might enhance the phenotypical differentiation of mMPCM from other subtypes in children, thereby increasing the accuracy of one's prognosis.

Tyrosine kinase inhibitors for the treatment of indolent systemic mastocytosis: Are we there yet?

Indolent systemic mastocytosis (ISM) is the most prevalent form of systemic mastocytosis. Many patients with ISM suffer from mast cell (MC) mediator-related symptoms. In a small number of patients, hematologic progression is seen in the follow-up. In some patients with ISM, symptoms arising from MC-derived mediators including gastrointestinal symptoms, anaphylaxis, and neuropsychiatric symptoms are kept under control with conventional mediator-targeting drugs or MC-stabilizing agents. However, in a substantial number of patients, the symptoms are refractory to such conventional therapy. For these patients, novel drugs and targeted approaches are considered. One reasonable approach may be to apply tyrosine kinase inhibitors directed against KIT and other key kinase targets expressed in neoplastic MCs in ISM. Because MCs in more than 90% of all patients with typical ISM display the KIT D816V mutant receptor, clinically effective KIT-targeting drugs have to be active against this mutant form of KIT. The 2 such most effective and well-studied agents currently available are midostaurin and avapritinib. Other KIT-targeting drugs, such as imatinib or masitinib, are less effective or even noneffective against KIT D816V and are thus recommended for use only in patients with other KIT mutant forms (noncodon 816 mutations) or with wild-type KIT. In the present article, we review the current state in the treatment of ISM with tyrosine kinase inhibitors, with special emphasis on treatment responses and potential adverse effects. In fact, all of these agents also have unique and common adverse effects, and their use to treat patients with ISM should be balanced against their toxicity and short- and long-term safety.

The Expressions of CD30 and CD123 of Mastocytosis in Taiwan.

Mastocytosis is a rare disease with a low incidence in Asia-Pacific populations. CD30 and CD123 may have potential prognostic and therapeutic value, but the results are inconsistent. Because racial disparities may exist, we aim to evaluate the expressions of CD30 and CD123 in a series of mastocytosis cases in Taiwan. Twelve patients with systemic and 7 with cutaneous forms of mastocytosis were studied. The expressions of CD30 and CD123 were correlated with the clinical features of the patients. Eighty-three percent (10/12) of patients with systemic mastocytosis (SM) had an associated hematological neoplasm. Four of the SM patients had both "B" and "C" findings, and they had a median survival time of 0.9 months. CD30 expression was positive in 50% (6/12) of SM cases and 100% (6/6) of cutaneous mastocytosis cases. CD123 was expressed focally or weakly in only 2 SM-associated hematological neoplasm cases. The distribution of mastocytosis subtypes and the expression of CD30 and CD123 in Taiwan differed from those reported in North America and Europe. However, mastocytosis, especially indolent forms, is easily overlooked as its heterogeneous and nonspecific clinical manifestations. A high index of suspicion and improved diagnostic methods can be helpful.

Utility of serum tryptase in Emergency Department patients with possible anaphylaxis

Background Diagnosing anaphylaxis is often straightforward but can be challenging if the presentation is atypical. In patients with atypical symptoms suspected to be due to an acute allergic reaction, s-tryptase can give additional diagnostic information. Measuring s-tryptase is also helpful in diagnosing mastocytosis. Obtaining s-tryptase levels has been done in the emergency department (ED) at Landspitali since 2011. The aim of this study was to evaluate the benefit of obtaining s-tryptase levels in the ED. Methods With institutional review board approval, all cases where s-tryptase level was obtained in ED patients from 2011-2018 were retrospectively reviewed. A database was collected including information on patient demographics, presenting symptoms, treatment, diagnosis, s-tryptase level and follow up. Results A total of 214 patients had a s-tryptase level measured. Serum tryptase was elevated (>12 μg/L) in 36 cases. Females were 131 and average age 40.6 years. Of the patients, 86.4% had skin or mucosal symptoms, 48.1% cardiovascular symptoms, 49.5% respiratory symptoms and 36.0% had gastrointestinal symptoms. An allergist reviewed 126 returning patients and 65 were considered to have had an episode of anaphylaxis. Of those 65 were 4 patients which did not meet the diagnostic criteria for anaphylaxis but had raised s-tryptase levels. Sensitivity of s-tryptase measurement was 40.9% and specificity 97.1%. Conclusions Obtaining a s-tryptase level from ED patients with possible anaphylaxis seems to be useful in atypical cases. The measurement is specific but not sensitive. No cases of mastocytosis were identified in the patient cohort.

The association of Greig syndrome and mastocytosis reveals the involvement of the hedgehog pathway in advanced mastocytosis

AbstractMastocytosis is a heterogeneous disease characterized by an abnormal accumulation of mast cells (MCs) in 1 or several organs. Although a somatic KIT D816V mutation is detected in ∼85% of patients, attempts to demonstrate its oncogenic effect alone have repeatedly failed, suggesting that additional pathways are involved in MC transformation. From 3 children presenting with both Greig cephalopolysyndactyly syndrome (GCPS, Mendelian Inheritance in Man [175700]) and congenital mastocytosis, we demonstrated the involvement of the hedgehog (Hh) pathway in mastocytosis. GCPS is an extremely rare syndrome resulting from haploinsufficiency of GLI3, the major repressor of Hh family members. From these familial cases of mastocytosis, we demonstrate that the Hh pathway is barely active in normal primary MCs and is overactive in neoplastic MCs. GLI3 and KIT mutations had a synergistic, tumorigenic effect on the onset of mastocytosis in a GCPS mouse model. Finally, Hh inhibitors suppressed neoplastic MC proliferation in vitro and extend the survival time of mice with aggressive systemic mastocytosis (ASM). This work revealed, for the first time, the involvement of Hh signaling in the pathophysiology of mastocytosis and demonstrated the cooperative effects of the KIT and Hh oncogenic pathways in mice with ASM, leading to the identification of new promising therapeutic targets.

M554 A RARE PATHOGENIC MUTATION ASSOCIATED WITH A PEDIATRIC CASE OF DIFFUSE CUTANEOUS MASTOCYTOSIS

Diffuse cutaneous mastocytosis (DCM) is a rare disease resulting from widespread mast cell accumulation within the dermis. Disease manifestations may include erythroderma and blistering skin rashes with systemic symptoms related to mast cell mediator release. DCM has commonly been associated with sporadic gain-of-function KIT D816V mutations. Familial mastocytosis cases from germline mutations are rare and not well described.

Retrospective Evaluation of Childhood Cutaneous Mastocytosis Cases

Retrospective Evaluation of Childhood Cutaneous Mastocytosis Cases

Frequency of isolated cutaneous involvement in adult mastocytosis: a cohort study.

Mastocytosis is characterized by the accumulation/proliferation of abnormal mast cells. The frequency of isolated cutaneous involvement in adults with mastocytosis has not been fully determined. The main objective of our study was to assess the frequency of isolated cutaneous mastocytosis (CM) in adults with mastocytosis skin lesions. The second objective was to compare the clinical, histological, biological and imaging features in patients with isolated CM and patients with systemic mastocytosis (SM). We included all patients with histology-proven mastocytosis skin lesions between January 2009 and December 2017. The mastocytosis diagnosis was made according to the international diagnostic criteria. All data were collected from a dedicated specific case report. Among 160 patients with mastocytosis skin lesions, 25 patients had isolated CM (15.6%), 105 had SM and 30 (18.7%) patients had undetermined mastocytosis. Skin KIT mutation (OR: 51.9, 95% CI: 3.9-678, P=0.001) and high bone marrow tryptase (OR: 97.4, 95% CI: 10.3-915, P=0.001) were strong predictors of SM. The prevalence of osteoporosis was higher in the SM population than in the isolated CM population. Moreover, a decrease in bone mineral density over a short period of follow-up (1-2years) was associated with SM. There were no differences between the two groups regarding the frequency of mast cell activation symptoms, the presentation of skin lesions, the number of mast cells in the dermis and the level of serum tryptase. We propose considering the KIT mutation status and bone marrow tryptase levels to aid the diagnosis of isolated CM in adult mastocytosis patients. Only a small minority of adults with mastocytosis skin lesions has isolated cutaneous involvement. In 18.7% of mastocytosis cases, even complete workup does not allow for a precise classification of patients.

Successful mast-cell-targeted treatment of chronic dyspareunia, vaginitis, and dysfunctional uterine bleeding

Dyspareunia, vaginitis and dysfunctional uterine bleeding (DUB) are common problems which, despite their polygenicity, commonly appear idiopathic and treatment-refractory. Mast cell (MC) activation syndrome (MCAS) is a newly-recognised, prevalent, chronic multisystem polymorbidity of general themes of inflammation ± allergic-type phenomena ± aberrant growth/development in assorted tissues. MCs produce significant quantities of heparin, too. As such, MCAS may underlie some cases of chronic dyspareunia, vaginitis or DUB. We report five such patients; all who responded well to MC-targeted treatment. We review aspects of MC biology and pathobiology of potential relevance to otherwise idiopathic persistent inflammatory or coagulopathic genital tract problems. Diagnostic testing for MCAS may be warranted in some patients with chronic dyspareunia, vaginitis or DUB (especially patients whose histories well fit the general profile of MCAS), and prospective therapeutic trials of MC-directed topical and/or systemic therapies may be warranted in such populations. Impact statement What is already known on this subject? Chronic, idiopathic, treatment-refractory female genital tract inflammation or bleeding are common problems for which mast cell (MC) disease, previously generally thought to consist of just rare cases of mastocytosis, and is seldom considered in the differential diagnosis. What do the results of this study add? The substantial prevalence of the newly recognised ‘mast cell activation syndrome’ (MCAS), featuring chronic inappropriate MC activation with little-to-no MC neoplasia, and its clinical presentation with chronic multisystem inflammation ± allergic-type phenomena ± aberrant growth/development in assorted tissues, raises the possibility that MCAS might underlie the aforementioned genital tract problems, especially in patients whose larger clinical presentations fit the MCAS profile. We report five example patients (among many more we have similarly treated) who enjoyed excellent responses to safe, inexpensive MC-targeted treatments, often given just intravaginally. What are the implications of these findings for clinical practice and/or further research? Our report identifies a potentially significant new MC-focused direction, of relevance to millions of affected women worldwide, for clinical treatment as well as for basic and clinical research, which historically has yielded major advancements disappointingly disproportionate to the scope of the affected population.

Prevalence of CD30 immunostaining in neoplastic mast cells: A retrospective immunohistochemical study.

Mastocytosis is a rare disease characterized by clonal neoplastic proliferation of mast cells (MCs). It ranges from skin lesions as cutaneous mastocytosis (CM) which may spontaneously regress to highly aggressive neoplasms with multiorgan involvement corresponding to some aggressive systemic mastocytosis (ASM), mast cell leukemia (MCL), and/or mast cell sarcoma (MCS).There is increasing evidence of CD30 expression in neoplastic MCs of the bone marrow. This expression has been described almost exclusively in aggressive forms of systemic mastocytosis (SM).The aim of the present study is to evaluate CD30 expression both in cutaneous and systemic forms of mastocytosis. Forty-two mastocytosis cases were reviewed, including cutaneous (n = 29) and systemic (n = 13) forms to assess the prevalence of CD30 expression. Thirty-nine out of 42 (92.8%) cases were CD30 positive. In cases of CM, 28/29 (96.5%) cases were CD30 positive, 11/13 cases of SM (84.6%) were positive for CD30. MCs in normal skin biopsies and in urticaria lesions were CD30-negative. This study found that CD30 is also frequently expressed in CM as well as in systemic forms. This finding is a major departure from the prevailing concept that CD30 expression is often related to aggressive systemic forms of mastocytosis.

Clinical cases of mastocytosis in clinical practice

Mastocytosis is a relatively rare group of diseases caused by the proliferation of mast cells in various organs and tissues. The article presents data on the etiology, pathogenesis, clinical presentations, diagnosis and differential diagnosis of mastocytosis, and own clinical observations. Presented clinical cases picture the features of the clinical course of the disease in different age groups. The first clinical case clearly shows the onset of the disease in early childhood (6 months), and misdiagnosis of this disease. The clinical picture of mastocytosis was wrongly assessed as a manifestation of atopic dermatitis, for which the patient received topical treatment without clinical effect. The second clinical observation is in 30 year old patient. The nature and spreading of the disease were assessed, proper treatment was administered. Both patients improved after treatment. Presented clinical observations reflect the importance of the problem in medical practice. Early diagnosis improves the prognosis of the disease and improves the quality of life.

Abstract 128: Tyrosine 823 in the activation loop of c-Kit regulates the transforming capacity of the oncogenic mutant D816V and its sensitivity to kinase inhibitors

Abstract Oncogenic mutations in c-Kit have been shown to lead to ligand-independent receptor activation and contribute to transformation. A substitution of an aspartate for a valine at position 816 (D816V) is one of the most commonly found oncogenic c-Kit mutation and is found in more than 90% of cases of mastocytosis and in a subgroup of germ cell tumors, core-binding factor acute myeloid leukemia and mucosal melanomas. Previous studies have shown that the D816V mutation causes a structural change in the activation loop resulting in weaker binding of the activation loop to the juxtamembrane domain, leading to a release of the negative constraint it poses on kinase activity. Here we have investigated the role of Y823 in the activation loop of c-Kit and its role in oncogenic transformation by c-Kit/D816V. Although dispensable for the kinase activity of c-Kit/D816V, the presence of Y823 was shown to be crucial for cell proliferation and survival. Furthermore, mutation of Y823 selectively down-regulated the Ras/Erk and Akt pathways. It also led to decreased phosphorylation of STAT5 and reduced the transforming capacity of D816V/c-Kit in vitro. The sensitivity to kinase inhibitors, such as dasatinib and nilotinib, was decreased in cells expressing c-Kit/Y823F/D816V compared to cells c-Kit/D816V. Mice injected with cells expressing c-Kit/D816V/Y823F displayed significantly reduced tumor size as well as tumor weight compared to controls. Finally, microarray array analysis, comparing c-Kit/Y823F/D816V cells with cells expressing c-Kit/D816V, demonstrate that mutation of Y823 causes up-regulation of pro-apoptotic genes whereas genes of survival pathways are down-regulated. Thus, phosphorylation of Y823 is not necessary for kinase activation, but essential for the transforming ability of the c-Kit/D816V mutant. Citation Format: Shruti Agarwal, Julhash U. Kazi, Sofie Mohlin, Sven Påhlman, Lars Rönnstrand. Tyrosine 823 in the activation loop of c-Kit regulates the transforming capacity of the oncogenic mutant D816V and its sensitivity to kinase inhibitors. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 128. doi:10.1158/1538-7445.AM2015-128

Detection of the KIT D816V mutation in peripheral blood of systemic mastocytosis: diagnostic implications

Recent studies have found the KIT D816V mutation in peripheral blood of virtually all adult systemic mastocytosis patients once highly sensitive PCR techniques were used; thus, detection of the KIT D816V mutation in peripheral blood has been proposed to be included in the diagnostic work-up of systemic mastocytosis algorithms. However, the precise frequency of the mutation, the biological significance of peripheral blood-mutated cells and their potential association with involvement of bone marrow hematopoietic cells other than mast cells still remain to be investigated. Here, we determined the frequency of peripheral blood involvement by the KIT D816V mutation, as assessed by two highly sensitive PCR methods, and investigated its relationship with multilineage involvement of bone marrow hematopoiesis. Overall, our results confirmed the presence of the KIT D816V mutation in peripheral blood of most systemic mastocytosis cases (161/190; 85%)—with an increasing frequency from indolent systemic mastocytosis without skin lesions (29/44; 66%) to indolent systemic mastocytosis with skin involvement (124/135; 92%), and more aggressive disease subtypes (11/11; 100%)—as assessed by the allele-specific oligonucleotide-qPCR method, which was more sensitive (P<.0001) than the peptide nucleic acid-mediated PCR approach (84/190; 44%). Although the presence of the KIT mutation in peripheral blood, as assessed by the allele-specific oligonucleotide-qPCR technique, did not accurately predict for multilineage bone marrow involvement of hematopoiesis, the allele-specific oligonucleotide-qPCR allele burden and the peptide nucleic acid-mediated-PCR approach did. These results suggest that both methods provide clinically useful and complementary information through the identification and/or quantification of the KIT D816V mutation in peripheral blood of patients suspected of systemic mastocytosis.