Proliferation Of Mast Cells Research Articles

1500 The Incidental Raised White Lesion: A Case of Indolent Mastocytosis

INTRODUCTION: Mastocytosis results from clonal proliferation of abnormally defective mast cells. The clinical presentation of mastocytosis can be heterogeneous, ranging from indolent disease to aggressive systemic mastocytosis, which can present with syncope, recurrent flushing, diarrhea, and abdominal pain. We present a case of an asymptomatic patient presenting for surveillance colonoscopy, found to have an isolated elevated white lesion in the colon which on biopsy was mastocytosis. CASE DESCRIPTION/METHODS: A 68-year-old man with history of hypertension and hyperlipidemia presented for surveillance colonoscopy. His last colonoscopy was five years prior and revealed one small adenomatous polyp. Vital signs were within normal limits and physical examination was unremarkable. He denied symptoms of flushing, pruritus, abdominal pain, nausea or vomiting. Colonoscopy revealed an isolated white, raised area of mucosa, measuring 5 mm in diameter which was encountered at the transverse colon (Figure 1). Biopsies of this area was obtained. Pathology of the elevated white mucosal area showed marked eosinophilic infiltrate admixed with round to spindle cells that stain positive for KIT and CD25. These findings are consistent with involvement by an abnormal mast cell infiltrate. The patient's complete blood count was normal and serum tryptase level was within normal limits. Given these findings, his diagnosis was consistent with asymptomatic indolent mastocytosis. He was recommended to have yearly complete blood count, liver function tests and tryptase level, in addition to bone density screening, bone marrow biopsy and close follow up with hematology and gastroenterology. DISCUSSION: Mastocytosis results from clonal proliferation of abnormal mast cells which can accumulate in the bone marrow, skin and other organs including the gastrointestinal tract. Gastrointestinal findings on colonoscopy can include normal mucosa, raised white-colored mucosa, polypoid lesions and ulcers or erosions involving the upper or lower gastrointestinal tract. While many patients with gastrointestinal tract involvement have symptoms of abdominal pain, nausea and diarrhea, this case highlights the importance of recognizing the endoscopic manifestations of asymptomatic indolent mastocytosis.

Potential effects of xylopic acid on acetic acid-induced ulcerative colitis in rats.

Xylopic acid (XA) has been reported to exhibit analgesic activity, alleviate neuropathic pain in rodents, and demonstrate anti-inflammatory effects. Intrarectal challenge of rats with acetic acid induces colitis that bears resemblance in terms of its pathogenesis, histopathology, and inflammatory profile to that in humans. Reactive oxygen species are implicated as the main driving force in this inflammatory bowel disease. This study aimed to investigate the anti-colitic potential of XA. We investigated the effect of XA on body weight, disease activity, inflammatory cell infiltration, and generation of reactive oxygen species. Rats were treated with XA or sulphasalazine, challenged intrarectally with acetic acid with macroscopic and microscopic findings made after eight days. Administration of XA to rats with colitis resulted in an increase in body weight with significant (p<0.05) improvement of the disease profile macroscopically. We observed decreased gross mucosal injury, reduced inflammation, and cellular proliferation with XA administration. Treatment with XA also resulted in decreased colonic epithelial expression of argyrophylic nucleolar organizer regions (AgNORs) with significant decrease (p<0.0001) in the quantitative expression of AgNORs/nucleus ratio to levels comparable with non-colitic control. We also observed reduced proliferation of mucosal mast cell in the colonic segment of the rats treated with XA. Treatment with XA also significantly (p<0.0001) increased the activity of SOD, CAT, and APx while it decreased the activity of MPO and MDA levels. Xylopic acid possesses anti-colitic activity in rats induced with acetic acid colitis.

Effects of ibrutinib on proliferation and histamine release in canine neoplastic mast cells.

The Bruton's tyrosine kinase (BTK) inhibitor ibrutinib is effective in the treatment of human chronic lymphocytic leukaemia and mantle cell lymphoma. Recent data have shown that ibrutinib also blocks IgE‐dependent activation and histamine release in human basophils (BAs) and mast cells (MCs). The aim of this study was to investigate whether BTK serves as a novel therapeutic target in canine mast cell tumours (MCTs). We evaluated the effects of ibrutinib on two canine MC lines, C2 and NI‐1 and on primary MCs obtained from canine MCTs (n = 3). Using flow cytometry, we found that ibrutinib suppresses phosphorylation of BTK and of downstream STAT5 in both MC lines. In addition, ibrutinib decreased proliferation of neoplastic MCs, with IC50 values ranging between 0.1 and 1 μM in primary MCT cells and between 1 and 3 μM in C2 and NI‐1 cells. In C2 cells, the combination “ibrutinib + midostaurin” produced synergistic growth‐inhibitory effects. At higher concentrations, ibrutinib also induced apoptosis in both MC lines. Finally, ibrutinib was found to suppress IgE‐dependent histamine release in primary MCT cells, with IC50 values ranging from 0.05 to 0.1 μM in NI‐1 cells, and from 0.05 to 1 μM in primary MCT cells. In summary, ibrutinib exerts anti‐proliferative effects in canine neoplastic MCs and counteracts IgE‐dependent histamine release in these cells. Based on our data, ibrutinib may be considered as a novel therapeutic agent for the treatment of canine MCT. The value of BTK inhibition in canine MCT patients remains to be elucidated in clinical trials.

An evaluation of masitinib for treating systemic mastocytosis

ABSTRACTIntroduction: Systemic Mastocytosis (SM) is a complex family of rare diseases, against which pharmacological therapies are still very few. It is a c-kit driven disease, whose disregulation leads to uncontrolled activation and proliferation of mast cells (MCs) with consequent release of effector molecules which are responsible for its clinical manifestations.Areas covered: Masitinib is a relatively new potential drug against SM and its chemical structure strictly derives from imatinib, the first tyrosine kinase inhibitor which entered the pharmaceutical market about 15 years ago. In this review, the authors present masitinib in all its properties, from chemistry to pharmacology and toxicity to its potential clinical application in SM, focusing the discussion on the few clinical trials in which it has been involved, with a particular attention on the still open challenge to determine how to measure the response to therapy.Expert opinion: In spite of their similarity in chemistry and biological activity against submolecular targets, masitinib is much more selective towards c-kit receptors than other tyrosine kinases, such as Bcl-Abl. Furthermore, its ability to inhibit degranulation, cytokine production and MCs migration from bone marrow gives it a great chance to become an important therapeutic option for selected SM patients.

Deletion of ΔdblGata motif leads to increased predisposition and severity of IgE-mediated food-induced anaphylaxis response.

BackgroundPrevious studies have revealed an important role for the transcription factor GATA-1 in mast cell maturation and degranulation. However, there have been conflicting reports with respect to the requirement of GATA-1 function in mast cell dependent inflammatory processes. Herein, we examine the requirement of GATA-1 signaling in mast cell effector function and IgE-mast cell-dependent anaphylaxis.ObjectiveTo study the requirement of GATA-1 dependent signaling in the development and severity of IgE-mast cell-dependent anaphylaxis in mice.MethodsWild type (Balb/c) and mutant ΔdblGata (Balb/c) mice were employed to study the role of GATA-1 signaling in in vitro IgE-mediated activation of bone marrow derived mast cells (BMMCs). Murine models of passive IgE-mediated and oral antigen-induced IgE-mediated anaphylaxis were employed in mice. Frequency of steady state mast cells in various tissues (duodenum, ear, and tongue), peritoneal cavity, and clinical symptoms (diarrhea, shock, and mast cell activation) and intestinal Type 2 immune cell analysis including CD4+ Th2 cells, type 2 innate lymphoid cells (ILC2), and IL-9 secreting mucosal mast cells (MMC9) were assessedResultsIn vitro analysis revealed that ΔdblGata BMMCs exhibit a reduced maturation rate, decreased expression of FcεRIα, and degranulation capacity when compared to their wildtype (WT) counterparts. These in vitro differences did not impact tissue resident mast cell numbers, total IgE, and susceptibility to or severity of IgE-mediated passive anaphylaxis. Surprisingly, ΔdblGata mice were more susceptible to IgE-mast cell-mediated oral antigen induced anaphylaxis. The increased allergic response was associated with increased Type 2 immunity (antigen-specific IgE, and CD4+ TH2 cells), MMC9 cells and small intestine (SI) mast cell load.ConclusionDiminished GATA-1 activity results in reduced in vitro mast cell FcεRIα expression, proliferation, and degranulation activity. However, in vivo, diminished GATA-1 activity results in normal homeostatic tissue mast cell levels and increased antigen-induced CD4+ Th2 and iMMC9 cell levels and heightened IgE-mast cell mediated reactions.

Neurocognitive dysfunction and anaphylaxis in pediatric maculopapular cutaneous mastocytosis

Cutaneous mastocytosis is a group of conditions associated with proliferation of mast cells in the skin. The most common form in children is maculopapular cutaneous mastocytosis (MPCM).1 Autism spectrum disorders were found to be more than 10-fold higher than baseline rates in patients with any form of mastocytosis,2 and learning disabilities have also tended to be more prevalent in the families of children with cutaneous mastocytosis.3 Similarly, systemic mastocytosis overall is associated with high rates of anaphylaxis,4 although the risk in pediatric MPCM may be lower.

Novel approaches to treating advanced systemic mastocytosis.

Mastocytosis is a myeloproliferative neoplasm characterized by expansion of abnormal mast cells (MCs) in various tissues, including skin, bone marrow, gastrointestinal tract, liver, spleen, or lymph nodes. Subtypes include indolent systemic mastocytosis, smoldering systemic mastocytosis and advanced systemic mastocytosis (AdvSM), a term collectively used for the three most aggressive forms of the disease: aggressive systemic mastocytosis, mast cell leukemia, and systemic mastocytosis with an associated clonal hematological non-mast cell disease (SM-AHNMD). MC activation and proliferation is physiologically controlled in part through stem cell factor (SCF) binding to its cognate receptor, KIT. Gain-of-function KIT mutations that lead to ligand-independent kinase activation are found in most SM subtypes, and the overwhelming majority of AdvSM patients harbor the KITD816V mutation. Several approved tyrosine kinase inhibitors (TKIs), such as imatinib and nilotinib, have activity against wild-type KIT but lack activity against KITD816V. Midostaurin, a broad spectrum TKI with activity against KITD816V, has a 60% clinical response rate, and is currently the only drug specifically approved for AdvSM. While this agent improves the prognosis of AdvSM patients and provides proof of principle for targeting KITD816V as a driver mutation, most responses are partial and/or not sustained, indicating that more potent and/or specific inhibitors are required. Avapritinib, a KIT and PDGFRα inhibitor, was specifically designed to inhibit KITD816V. Early results from a Phase 1 trial suggest that avapritinib has potent antineoplastic activity in AdvSM, extending to patients who failed midostaurin. Patients exhibited a rapid reduction in both symptoms as well as reductions of bone marrow MCs, serum tryptase, and KITD816V mutant allele burden. Adverse effects include expected toxicities such as myelosuppression and periorbital edema, but also cognitive impairment in some patients. Although considerable excitement about avapritinib exists, more data are needed to assess long-term responses and adverse effects of this novel TKI.

Flow-mediated dilation shows impaired endothelial function in patients with mastocytosis

Mastocytosis is a rare disease characterized by clonal proliferation of mast cells (MCs) in different organs. Clinical manifestations of mastocytosis are mostly due to release of mediators from MCs and, in many cases, such as urticaria, flushing, angioedema, and anaphylaxis, are an expression of the biological effects of mediators on endothelial cells. Chronic secretion of mediators in patients with mastocytosis can lead to alteration of endothelial function. We sought to investigate endothelial function in patients with mastocytosis using a noninvasive technique of flow-mediated dilation (FMD). Twenty-five adult patients with indolent and advanced forms of mastocytosis and 20 healthy control subjects were enrolled in the study. Ultrasound assessment of FMD was performed by measuring changes in the diameter of the brachial artery after 5minutes of arterial occlusion. Changes in FMD were correlated with clinical parameters and serum tryptase levels. Patients with mastocytosis had lower FMD compared with healthy control subjects (P<.001). Advanced and smoldering forms showed a lower FMD compared with indolent forms (P<.001). FMD inversely correlated with age and serum tryptase levels and directly with median arterial pressure and recurrent flushing episodes. No correlation was found between FMD and osteoporosis, recurrent anaphylaxis, presence of skin lesions, and long-term antihistamine treatment. Endothelial dysfunction, as demonstrated by FMD reduction, is detectable in patients with mastocytosis and is more severe in patients with high tryptase levels and advanced disease. Endothelial function appears to be negatively influenced by MC proliferation rather than by the severity of mediator-related symptoms.

The upregulation of Pim kinases is essential in coordinating the survival, proliferation, and migration of KIT D816V-mutated neoplastic mast cells

About ˜80% of mast cell neoplasm patients harbor the c-Kit activating mutation D816 V, which is associated with c-Kit inhibitor resistance and poor prognosis. However, the molecular basis for these effects is not fully known. To address this issue, in this study we screened molecules whose expression is altered by KIT D816 V mutation and found that Pim kinases were overexpressed in D816V-mutant neoplastic mast cells. This was accompanied by upregulation of signal transducer and activator of transcription (STAT) and mammalian target of rapamycin (mTOR) and downregulation of Akt and extracellular signal-regulated kinase (ERK1/2). Activated Pim kinases promoted the survival of D816 V cells by maintaining mTOR and p70S6K activation even under nutrient starvation. Conversely, cell proliferation was suppressed by inhibiting Pim kinases. The mRNA level of C-X-C chemokine receptor type 4 (CXCR4) was about 2-fold higher in D816 V cells; this was associated with a 2-fold increase in migratory capacity, which was modulated by Pim kinases. We also confirmed that upregulation of Pim kinases is a feature specific to cells with the D816 V mutation and is not observed in cells with the c-Kit activating N822 K mutation. These data suggest Pim kinases as a promising therapeutic target for the treatment of mast cell neoplasms with KIT D816 V mutation.

PS1461 FAMILIAL OCCURRENCE OF SYSTEMIC AND CUTANEOUS MASTOCYTOSIS IN AN ADULT MULTICENTER SERIES: A REPORT OF 22 CLUSTERED CASES

Background:Mastocytosis refers to a group of clonal disorders characterized by abnormal proliferation of mast cells infiltrating various tissues, especially skin and hematopoietic organs. Clinical presentation is heterogeneous and may vary from skin‐limited disease to more aggressive variants. The clonal nature of mastocytosis has been largely demonstrated by the identification of gain‐of‐function mutations in exon 17 causing constitutive activation of the c‐KIT protooncogene. In the large majority of patients with systemic disease a somatic aspartate‐to‐valine substitution in codon 816 (D816 V) of the KIT gene is demonstrable. Typically, mastocytosis is considered a non‐hereditary disease, although clustered cases were reported in pediatric series with an estimated frequency of 8–10%, in the absence or presence of c‐KIT mutations, generally located outside the exon 17. Prevalence data about familial cases in adults are lacking. To our knowledge, somatic D816 V KIT mutation was reported only in two adult clusters and in two pediatric familial cases.Aims:In this retrospective, observational, multicenter study we sought: a) to estimate the prevalence of familial disease in a series of 1541 patients with mastocytosis referred in adulthood (&gt;16 years old) to 8 Italian Institutions, and b) to describe the clinical and molecular characteristics of clustered cases.Methods:Diagnosis of mastocytosis was made according to the 2016 World Health Organization criteria. All patients were asked for the occurrence of the same disease in relatives. Clinical and molecular data were recorded in all patients and in the affected relatives, when available.Results:Familial occurrence of mastocytosis was reported in 22 patients (1.4% of the whole cohort). Clinical and molecular characteristics are reported in table I. Index cases were 12 males and 10 females, median age at diagnosis was 43 years (range 16–65 years). Diagnosis in index patients was systemic mastocytosis (SM) (n = 15), mastocytosis in the skin (MIS) (n = 3), and maculo‐papular cutaneous mastocytosis (MPCM) (n = 4). All but one SM patients harbored D816V KITmutation. Each index case reported a single affected relative: they were 14 males and 8 females, with median age at diagnosis of 20 years (range 0–70 years). Diagnosis in relatives was SM (n = 7), MIS (n = 3), MCPM (n = 6) and Mastocytoma (n = 6). The relationship between index and relatives was mainly “parent and child” (41%) and “siblings” (27%). Notably, 4 SM patients had one child who developed single or multiple mastocytoma; in other two families index and/or relatives developed an associated hematological neoplasia.Summary/Conclusion:To our knowledge, this is the largest report about the prevalence and the characteristics of familial cases in an adult population of patients with mastocytosis. Familial occurrence of mastocytosis with different clinical and molecular characteristics between indices and relatives suggests that D816 V KIT mutations may be a secondary genetic event. Further studies, including search for mutations in all patients with skin‐limited disease and genotyping of D816V‐mutated patients, are needed to confirm our hypothesis.image

Chrysophanol, an anthraquinone from AST2017-01, possesses the anti-proliferative effect through increasing p53 protein levels in human mast cells.

Natural products are well known as the source of drugs in the treatment of allergic inflammation. Chrysophanol, an anthraquinone from the AST2017-01 extract, showed a beneficial anti-inflammatory effect on activated human mast cells in our previous study. However, a regulatory effect of AST2017-01 and chrysophanol on mast cell proliferation induced by thymic stromal lymphopoietin (TSLP) remains unclear. The present study determined the anti-proliferative effect and the fundamental mechanism of AST2017-01 and chrysophanol in mast cells. We evaluated an anti-proliferative effect of AST2017-01 and chrysophanol in TSLP-stimulated human mast cell line, HMC-1. Without cytotoxicity, AST2017-01 and chrysophanol decreased mast cells growth and Ki67 mRNA expression increased by TSLP. AST2017-01 and chrysophanol enhanced expressions of p53 and Bax, whereas inhibited expression of Bcl-2. AST2017-01 and chrysophanol restored caspase-3 activity which was decreased by TSLP. AST2017-01 and chrysophanol suppressed expressions of murine double minute-2 protein and phosphorylated-signal transducer and activator of transcription six which are associated with the regulation of p53 protein. AST2017-01 and chrysophanol decreased levels of interleukin (IL)-13, IL-6, and tumor necrosis factor-α. Moreover, AST2017-01 and chrysophanol reduced mRNA expressions of TSLP receptor and IL-7 receptor α. Therefore, this study proposes that AST2017-01 and chrysophanol may be promising candidates for the development of potent anti-inflammatory or health functional foods.

Связь между хроническим воспалением и развитием мастоцитомы у шарпеев

This article is devoted to the study of the connection between autoinflammatory disease and the development of a mast cell tumor on the example of Shar-Pei. The HAS2 gene, which is responsible for the synthesis of hyaluronic acid, in Shar-Pei has an increased expression due to which hyaluronic acid accumulates in the dermis, forming breed-defining skin phenotype — thik skin folds. It became known that hyaluronic acid is involved in immune reactions. Under normal conditions, it is in the high molecular weight fraction, but in abundant it begins to fragment into low molecular weight polymers interacting with the membranes of mast cells, as an antigen, due to chemical similarity with the microbial surface. Thus, mast cells and other immunocompetent cells initiate the inflammatory process. Therefore, the breed predisposition of Shar-Pei to the accumulation of hyaluronic acid can cause self-inflammatory diseases in dogs. The link with mastocytoma can be traced because hyaluronic acid also affects the proliferation and terminal differentiation of mast cells, interacting with the CD44 co-receptor of c-kit receptor. The KIT gene is marked by researchers as the gene responsible for the active proliferation of mast cells. There were found mutations in the same gene in dogs with a mastocytoma. Perhaps the appearance of hyaluronic acid in chronic inflammation, as well as in the development of mastocytoma indicate the presence of a connection between both pathological processes.

Tumor⁻Microenvironment Interaction: Analysis of Mast Cell Populations in Normal Tissue and Proliferative Disorders of the Canine Prostate.

Mast cells (MCs) are involved in angiogenesis, tissue remodeling and immunomodulation in several human and animal tumors, although their exact role is still controversial. Since no information is available in canine prostate carcinoma (PC) and normal prostate tissues, the aims of this study were to evaluate the possible correlations between MC distribution, molecular expression and microvessel density (MVD) in normal prostatic tissue and proliferative disorders of the canine prostate. All samples (6 normal, 15 benign prostate hyperplasia-BPH, 8 PC) were stained with Toluidine Blue and immunohistochemically evaluated for tryptase, c-Kit (CD117) and CD31. Mast cell density (MCD) and MVD were quantified by the hot-spot method. MCD was significantly increased in periglandular/peritumoral areas, when compared with intraglandular/intratumoral areas, in all groups (p = 0.03). C-Kit expression was strongly associated with PC (ρ = 0.75 p = 0.03), whereas positive correlation between tryptase and c-Kit expression (ρ = 0.64 p = 0.01) was observed in periglandular areas of BPH. MVD showed a correlation with MCD in BPH (ρ = 0.54 p = 0.04). Our data support the importance of c-Kit in regulating MC proliferation. The predominant location of MCs in peritumoral areas of canine PC was similar to the human counterpart, in which PC cells are supposed to produce substances attracting MCs to the tumor microenvironment.

Atteinte osseuse au cours de la mastocytose systémique

Mastocytosis are characterized by an abnormal tissular proliferation of mast cells in at least one visceral organ. Considering the accumulation of mast cells in the bone marrow, bone complications as osteoporosis with an increased risk of vertebral fractures can be observed. Bone involvement may also be the sole presentation of abnormal proliferation and the diagnosis of mastocytosis should be discussed in case of bone fragility in young patients. Bone complications are related to mast cell's infiltration and to mediators’ release by stimulated mast cells. Considering bone involvement, it is useful to assess bone mineral density (BMD) and to perform bone radiographs, for the assessment of vertebral fractures. There are very few data on the bone efficacy of mastocytosis treatments. Antiresorptive treatments as bisphosphonates are logical because of the key role of osteoclast and are indicated in patients with history of low trauma fracture and/or low BMD.

Systemic mastocytosis in adults: 2019 update on diagnosis, risk stratification and management.

Systemic mastocytosis (SM) results from a clonal proliferation of abnormal mast cells (MCs) in extra-cutaneous organs. The major criterion is presence of multifocal clusters of abnormal MC in the bone marrow. Minor diagnostic criteria include elevated serum tryptase level, abnormal MC CD25 expression, and presence of KITD816V mutation. Establishing SM subtype as per the World Health Organization classification system is an important first step. Broadly, patients either have indolent/smoldering SM (ISM/SSM) or advanced SM, the latter includes aggressive SM (ASM), SM with associated hematological neoplasm (SM-AHN), and mast cell leukemia (MCL). Identification of poor-risk mutations (ie, ASXL1, RUNX1, SRSF2, NRAS) further refines the risk stratification. Recently, clinical and hybrid clinical-molecular risk models have been developed to more accurately assign prognosis in SM patients. ISM patients have a normal life expectancy and treatment is generally limited to anaphylaxis prevention/symptom control/osteoporosis treatment. Patients with advanced SM frequently need MC cytoreductive therapy to ameliorate disease-related organ dysfunction. High response rates have been seen with small-molecule inhibitors that target mutant-KIT, including midostaurin (Food and Drug Administration approved) or avapritinib (investigational). Other options for MC cytoreduction include cladribine or interferon-α, although head-to-head comparisons are lacking. Treatment of SM-AHN primarily targets the AHN component, if an aggressive disease such as acute myeloid leukemia is present. Allogeneic stem cell transplant can be considered in such patients, or in those with relapsed/refractory advanced SM. Imatinib has a limited therapeutic role in SM; effective cytoreduction is limited to those with imatinib-sensitive KIT mutations.

&lt;i&gt;PBRM1&lt;/i&gt; Mutation Recruits More Mast Cells by Upregulating CCL5 in a Clear Cell Renal Cell Carcinoma Tumor Microenvironment

Background: PBRM1 (Polybromo-1) is the second most frequently mutated gene in ccRCC (clear cell renal cell carcinoma), and loss of PBRM1 was correlated with advanced tumor and tyrosine kinase inhibitor or immune checkpoint inhibitor clinical therapy in previously reported studies. However, the mechanisms of PBRM1 mutation in tumor microenvironment characterization are poorly understood. Methods: We investigated the tumor microenvironment in ccRCC by estimating immune cells in malignant tumors using CIBERSORT and estimating stromal and immune cells in malignant tumors using an expression data (ESTIMATE) algorithm. Gene set enrichment analysis hierarchical clustering and weighted correlation network analysis were used to analyze the characteristics and clinicopathologic features of ccRCC. Mast cell recruitment assay, colony formation assay, cell cycle assay, ELISA, and tube formation assay were applied to test PBRM1 function in vitro. Findings: We discovered that ccRCC patients with PBRM1 mutations were associated with inhibited CD8 T-cell infiltration but more resting mast cells in the tumor microenvironment. Silenced PBRM1 improved mast cell recruitment, angiogenesis, and cell proliferation among ccRCC cells. The molecular mechanism involved the upregulation ofCCL5 levels through PBRM1 mutations. CCL5 evoked immune-related pathways [including interferon-inflammatory signaling, interferon-gamma signaling, and IL-6-JAK- STAT3 (interleukin-6-Janus kinase-signal transducers and activators of transcription 3)] and recruited more mast cells to the tumor microenvironment. Furthermore, we confirmed that vascular endothelial growth factor family genes are overexpressed and that hypoxia-inducible factor-related processes are activated. Interpretation: These results demonstrated that PBRM1 mutation-CCL5-mast cell infiltration plays a key role in ccRCC clinical therapy. Funding Statement: This study was supported by the National Natural Science Foundation of China (NSFC No. 81602244 to Shan Xu) and Natural Science Basic Research Plan in Shaanxi Province of China (Program No. 2017JM8018 to Shan Xu). Declaration of Interests: The authors stated: None. Ethics Approval Statement: Not required.

Systemic Mastocytosis, Version 2.2019, NCCN Clinical Practice Guidelines in Oncology.

Mastocytosis is a group of heterogeneous disorders resulting from the clonal proliferation of abnormal mast cells and their accumulation in the skin and/or in various extracutaneous organs. Systemic mastocytosis is the most common form of mastocytosis diagnosed in adults, characterized by mast cell infiltration of one or more extracutaneous organs (with or without skin involvement). The identification of KIT D816V mutation and the emergence of novel targeted therapies have significantly improved the diagnosis and treatment of systemic mastocytosis. However, certain aspects of clinical care, particularly the diagnosis, assessment, and management of mediator-related symptoms continue to present challenges. This manuscript discusses the recommendations outlined in the NCCN Guidelines for the diagnosis and management of patients with systemic mastocytosis.

The CDK4/6 Inhibitor Palbociclib Exerts Growth-Inhibitory Effects on Neoplastic Mast Cells and Synergizes with Midostaurin in Producing Growth Arrest

Aggressive systemic mastocytosis (ASM) and mast cell leukemia (MCL) are rare, malignant diseases with an unfavorable prognosis. In a majority of patients, the transforming KIT mutation D816V is detectable. Currently, several drugs are available for the treatment of ASM/MCL, including midostaurin, a KIT D816V-targeting drug that has recently been approved for the treatment of advanced SM in the US and in Europe. However, when applied as single drug, midostaurin usually fails to induce durable remissions in patients with ASM/MCL, and the same holds true for all other drugs tested in the ASM/MCL context so far. Therefore, drug combinations, including established drugs and novel targeted drugs are currently being examined for their anti-neoplastic effects in ASM/MCL. CDK4 and CDK6 are kinases that play an essential role in cell cycle-initiation in normal and neoplastic cells. However, the role of CDK4/6 as potential therapeutic targets in neoplastic mast cells (MC) has not been analyzed so far. Recently, three CDK4/6 inhibitors, palbociclib, ribociclib and abemaciclib, have been translated into clinical application. The aim of the current study was to evaluate the effects of these CDK4/6 inhibitors on cell cycle progression, proliferation and survival of neoplastic MC. In initial experiments, we employed the MCL-related cell lines HMC-1.1 (lacking KIT D816V), HMC-1.2 (KIT D816V+), ROSAKIT WT, ROSAKIT D816V and MCPV-1 (expressing RAS G12V, Large T and hTert). In 3H-thymidine incorporation experiments, all three CDK4/6-inhibitors were found to block proliferation in both HMC-1 sub-clones and both ROSA sub-clones, with comparable IC50 values (<0.5 µM). In MCPV-1 cells, similar results were obtained, but higher concentrations of palbociclib, ribociclib and abemaciclib were required to block proliferation (IC50 1-5 µM). These data suggest that CDK4/6-inhibitors exert anti-proliferative effects in neoplastic MC independent of the presence of KIT D816V. In a next step, we examined drug effects on primary bone marrow cells obtained from patients with KIT D816V+ indolent SM (n=3), ASM (n=1), SM with an associated hematologic neoplasm, ASM-AHN (n=5) and MCL (n=2). As determined by 3H-thymidine uptake, palbociclib was found to inhibit cell proliferation at pharmacologically meaningful concentrations in all donors tested, with IC50 values ranging between 5 nM and 250 nM. Similar effects were obtained when applying ribociclib (25-500 nM) and abemaciclib (5-500 nM). To learn more about the mechanisms underlying the effects of the CDK4/6 inhibitors on neoplastic MC, cell cycle progression and apoptosis were examined in HMC-1.1 and HMC-1.2 cells after drug exposure. In both cell lines, the palbociclib-induced growth inhibition was found to be accompanied by cell cycle arrest in the G1-phase. Moreover, all three CDK4/6 inhibitors were found to produce time- and dose-dependent apoptosis in HMC-1.1 and HMC-1.2 cells during 72 hours of incubation. In a next step, Western blot experiments were performed using antibodies against the main downstream target of CDK6, retinoblastoma protein-1 (Rb-1). The Rb-1 antigen was found to be expressed in phosphorylated form (p-Rb-1) in HMC-1.1 and HMC-1.2 cells. As expected, all 3 CDK4/6 inhibitors were found to suppress p-Rb-1 expression in both HMC-1 cell lines, suggesting specific drug effects. In a final step, we examined potential cooperative drug effects using palbociclib and the KIT D816V-targeting drug midostaurin. In these experiments, palbociclib was found to synergize with midostaurin in inducing growth inhibition in HMC-1 cells. In conclusion our data suggest that inhibition of CDK4/6 may be a new promising approach for the treatment of patients with advanced SM. In addition, our data suggest that CDK4/6 inhibitors may represent promising combination partners for midostaurin in the treatment of ASM/MCL. Whether treatment with CDK4/6 inhibitors alone or in combination with KIT inhibition, is indeed sufficient to control proliferation of neoplastic MC in vivo in patients with advanced SM remains to be determined in forthcoming studies. DisclosuresHoermann:Novartis: Honoraria, Research Funding; Bristol-Myers Squibb: Honoraria; Pfizer: Honoraria. Sperr:Novartis: Honoraria; Pfizer: Honoraria; Daiichi Sankyo: Honoraria. Reiter:Incyte: Consultancy, Honoraria. Valent:Incyte: Honoraria; Pfizer: Honoraria; Novartis: Honoraria.

Systemic Mastocytosis in United States: A Population Based Study

Introduction:Systemic mastocytosis (SM) is a rare hematological disorder characterized by clonal proliferation and activation of abnormal mast cells. It can vary from an indolent form to an aggressive form including progression to leukemia. There is limited data on epidemiology, clinical characteristics and outcome of this disease in population based setting. Till date, a retrospective study by Lim, Ken-Hong, et.al which included 342 patients diagnosed with systemic mastocytosis in Mayo clinic, is the largest series of patient published so far. This study reports the clinical presentation and outcome of patients with SM but there are no population based study in United States so far. We therefore conducted this population based study to determine epidemiology, survival pattern and incidence of second primary malignancy among patients with SM.Methods:We used SEER 18 database (2000-2014) to select all adult patients with age 20 or above with SM. Patient population was divided into various cohorts based on age (20-59, 60-79 and 80+ years), sex, race (Caucasians, African American and Others), area of residence (rural, urban and metropolitan) and annual household income (<$25000, $25000-<$50000 and ≥$50000). Age adjusted incidence rate was calculated using 2000 US standard population using SEER stat rate session. 5-year relative survival (RS) rate was calculated using SEER stat and compared using Z test. Cox proportional hazard model was used for multivariate analysis of factors associated with relative survival using Cansurv software. MP-SIR session in SEER stat was used to calculate the risk of second primary malignancy.Result:The incidence was found to be 0.046 per 10000 among general population. Incidence was found to be higher among Caucasians compared to African American (0.056 vs. 0.018 per 100000). Median age at diagnosis was 55 years. Of the total 425 patients, majority were Caucasians (92.5%), age <60 years (59.3%) and from metropolitan area (84.7%) but there was equal distribution among male and females.10 year overall survival was found to be 61.5±3.1% by KM curve. 5-year RS was found to be 74.0±2.7% for the whole population. Females had significantly better survival compared to males, 5-year RS of 84.7±3.1% vs. 62.3±4.3%, P <0.0001. Survival trended to be better for Caucasians compared to African American but didn't reach clinical significance, 74.6±2.8 vs. 50±14.8, p 0.08. Patients <60 years had significant better survival compared to 60 to 79 and 80+ years ( 5-year RS of 88.6±2.4 vs. 58.4±5.2 and 16.0±11.2 respectively with P <0.0001 for both comparison). In multivariate analysis, younger age group, female sex and Caucasian race were found to be independent predictor of better 5 year relative survival with P<0.0001 compared to their counterparts.Patients with systemic mastocytosis were found to have higher risk of developing both solid organ as well as hematological malignancy within 5 years of diagnosis (as shown in table 1). After that the risk decreased and was comparable to general population.Conclusion:Our study shows that systemic mastocytosis is rare disease in general population and survival is better among specific subgroup of patients including females, younger patient and Caucasians. As the majority deaths occurred in first 5 years after diagnosis and as incidence of second primary malignancy is higher in the first 5 years, we recommend close follow up for first five years after diagnosis. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

AK002, a Novel Humanized Monoclonal Antibody to Siglec-8, Inhibits Mast Cell Activity and Depletes Eosinophils in Ex Vivo Bone Marrow Tissue from Patients with Systemic Mastocytosis

INTRODUCTION: Systemic Mastocytosis (SM) is a rare disease characterized by the clonal proliferation and accumulation of mast cells in the bone marrow, respiratory and gastrointestinal tracts, and organs such as the skin, liver, spleen, and brain. Common symptoms include pruritus, flushing, headache, cognitive impairment, fatigue, diarrhea, abdominal pain, hypotension and skin lesions, as well as an increased risk for osteoporosis and anaphylaxis. SM is currently managed with antihistamines, cromolyn sodium, and leukotriene blocking agents, which lack specificity and efficacy. In addition, glucocorticoids can provide temporary relief in some cases; however long-term treatment with steroids is not appropriate due to their many side effects.Siglec-8 is an inhibitory receptor selectively expressed on human mast cells and eosinophils, and therefore represents a novel target for the treatment of SM. Antibodies to Siglec-8 have been shown to inhibit mast cell activity and induce apoptosis of eosinophils. AK002 is a novel, humanized, non-fucosylated IgG1 monoclonal antibody to Siglec-8. This study evaluates the expression of Siglec-8 and ex vivo activity of AK002 on mast cells and eosinophils in bone marrow biopsies from patients with SM.METHODS: Bone marrow aspirates were obtained from patients clinically diagnosed with SM and processed to remove red blood cells. Multi-color flow cytometry was used to quantify eosinophils and mast cells and to evaluate the activation state of mast cells. The ex vivo activity of AK002 against eosinophils and mast cells was evaluated by flow cytometry. The inhibitory activity of AK002 agaist mast cells was also examined by quantifying cytokine levels in cultured bone marrow aspirate supernatants.RESULTS: All mast cells and eosinophils in bone marrow aspirates from SM patients displayed high Siglec-8 receptor expression (Figure 1). These mast cells also expressed the SM specific markers, CD25 (Figure 1) and CD30 and increased levels of cell surface degranulation markers. The expression of CD25 on mast cells significantly decreased following overnight treatment with AK002. AK002 also significantly reduced the level of mast cell-associated cytokines produced in cultured bone marrow supernatants, including IL-6, IL-8, and TNFα (Figure 2A). These changes in mast cell activity after AK002 treatment were not due to a reduction in mast cell numbers. In contrast, overnight incubation of AK002 significantly reduced the number of bone marrow eosinophils compared to an isotype control (Figure 2B).CONCLUSIONS: Bone marrow aspirates from patients with SM had activated mast cells and eosinophils that displayed robust expression of Siglec-8. AK002 demonstrated SM mast cell inhibition in ex vivo bone marrow aspirates. AK002 also had depleting effects on eosinophils, which may be valuable to SM patients with associated eosinophilia. These encouraging results could represent a novel approach for the treatment of SM. [Display omitted] DisclosuresYoungblood:Allakos, Inc.: Employment. Brock:Allakos, Inc.: Employment. Leung:Allakos, Inc.: Employment. Chang:Allakos, Inc.: Employment. Bebbington:Allakos, Inc.: Employment. Tomasevic:Allakos, Inc.: Employment.