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

Mastocytosis 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.

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

BACKGROUND: 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). METHODS: 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. RESULTS: 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 (1-2 years) 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. CONCLUSION: 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.

Higher prevalence of vertebral fractures in systemic mastocytosis, but not in cutaneous mastocytosis and idiopathic mast cell activation syndrome.

Little is known about osteoporosis in mast cell disorders (MCDs) not related to systemic mastocytosis. We described osteoporosis and fractures in MCDs and showed that systemic mastocytosis was the only studied MCDs associated with osteoporotic vertebral fractures. INTRODUCTION: To describe osteoporosis (OP) and fragility fractures in mast cell disorders (MCDs). METHODS: We retrospectively analyzed data concerning all successive patients with systemic mastocytosis (SM), cutaneous mastocytosis (CM), and mast cell activation syndromes (MCAS) diagnosed in our mastocytosis expert center between 2004 and 2015. We collected data concerning demographic profiles, clinical signs of MCD, osteoporosis, fractures, densitometry, and biological assessment of MCD. We compared CM and MCAS patients with SM patients with regard to the characteristics of OP and fragility fractures. RESULTS: We assessed 89 SM patients, 20 CM patients, and 20 MCAS patients. Osteoporosis was less frequent in CM (15.0%) and MCAS (10.0%) than in SM (44.9%). Similarly, fractures were less frequent in non-SM MCDs, respectively 5.0%, 5.0%, and 28.1%. SM patients displayed high prevalence of vertebral fractures (22.5%), mostly multiple. Conversely, in non-SM patients, vertebral fractures appeared to be uncommon (5%) and more frequently associated with risk factors for osteoporosis. CONCLUSIONS: SM is associated with multiple vertebral osteoporotic fractures, whereas CM and MCAS do not appear to be associated with this phenotype.

Paediatric mastocytosis: long-term follow-up of 53 patients with whole sequencing of KIT. A prospective study.

BACKGROUND: Mastocytosis is a heterogeneous group of clinical disorders characterized by the abnormal accumulation of mast cells. The adult and paediatric forms differ in their clinical and genetic features and outcomes. OBJECTIVES: To describe the clinical evolution of a well-characterized cohort of paediatric mastocytosis (PM), and to analyse the relationship between KIT mutation and the clinical course. METHODS: This was a prospective cohort study performed at the National Clinical Reference Center for Mastocytosis. Diagnosis was confirmed by identification of KIT mutation on lesional skin biopsy. Mastocytosis subtype, mast cell mediator-related symptoms (MC MRS) and clinical course were recorded. Fifty-three patients with PM and > 4 years of disease course were enrolled. The mean ± SD age at the final evaluation was 13·2 ± 4·8 years. The main outcome was the type of KIT mutation as a predictor of evolution and clinical characteristics. RESULTS: Patients presented with maculopapular cutaneous mastocytosis (n = 44), diffuse cutaneous mastocytosis (n = 6) or mastocytoma (n = 3). The mean duration of disease was 12·1 years. Substantial or partial cutaneous regression (18 of 53 and 16 of 53), stabilization or aggravation (16 of 53) and complete cutaneous regression (three of 53) were noted. MC MRS mainly regressed (21 of 53). For 22 patients, evolution of MC MRS and evolution of cutaneous lesions were different. No significant association between evolution and KIT mutation or between evolution and type of cutaneous mastocytosis was found. A late onset of the disease (after 2 years) is associated with worse evolution. CONCLUSIONS: PM is not systematically self-regressive. MC MRS manifestations and cutaneous lesions can persist or increase overtime. KIT mutation is not a predictor of evolution.

IL-3-producing basophils are required to exacerbate airway hyperresponsiveness in a murine inflammatory model.

BACKGROUND: Basophils are commonly associated with allergic responses because of their ability to produce large amounts of pro-Th2 cytokines and histamine. However, the mechanisms through which bone marrow-resident basophils (BMRB) become fully competent cytokine and histamine producers in response to IgE crosslinking are poorly understood. Here, we sought to determine the role of IL-3 in promoting pro-Th2 basophils. METHODS: BMRB and basophils exposed to IL-3 in vitro and in vivo were evaluated for their production of Th2 cytokines and histamine in response to FcεRI crosslinking on both protein and gene expression levels. In vivo relevance of our findings was assessed in a model of ovalbumin-induced allergic asthma using IL-3-deficient and wild-type mice in a protocol of adoptive basophil transfer. RESULTS: We show that BMRB and basophils previously exposed to IL-3 differ in their ability to generate cytokines (IL-4, IL-6, IL-13, and GM-CSF) and histamine in response to FcεRI crosslinking, reflecting two stages of maturation. Exposure to IL-3 initiated an autocrine loop of endogenous IL-3 production that enhanced histamine and cytokine production upon FcεRI crosslinking. This increased responsiveness required calcium flux and was dependent on calcineurin and store-operated calcium channels. Our findings are of pathophysiological relevance, as assessed by the failure of IL-3-deficient mice to develop airway hyperreactivity, which could be restored by adoptive transfer of IL-3-derived basophils recovered from wild-type mice. CONCLUSION: IL-3-dependent basophils promote Th2 allergic AHR, which designates the IL-3/basophil axis as a promising therapeutic target for the treatment of basophil-dependent asthma.

From hepatitis C virus infection to B-cell lymphoma.

In addition to liver disorders, hepatitis C virus (HCV) is also associated with extrahepatic immune manifestations and B-cell non-Hodgkin lymphoma (NHL), especially marginal zone lymphoma, de novo or transformed diffuse large B-cell lymphoma and to a lesser extent, follicular lymphoma. Epidemiological data and clinical observations argue for an association between HCV and lymphoproliferative disorders. The causative role of HCV in NHL has been further supported by the response to antiviral therapy. Pathophysiological processes at stake leading from HCV infection to overt lymphoma still need to be further elucidated. Based on reported biological studies, several mechanisms of transformation seem however to emerge. A strong body of evidence supports the hypothesis of an indirect transformation mechanism by which sustained antigenic stimulation leads from oligoclonal to monoclonal expansion and sometimes to frank lymphoma, mostly of marginal zone subtype. By infecting lymphocytes, HCV could play a direct role in cellular transformation, particularly in de novo large B-cell lymphoma. Finally, HCV is associated with follicular lymphoma in a subset of patients. In this setting, it may be hypothesized that inflammatory cytokines stimulate proliferation and transformation of IgH-BCL2 clones that are increased during chronic HCV infection. Unraveling the pathogenesis of HCV-related B-cell lymphoproliferation is of prime importance to optimize therapeutic strategies, especially with the recent development of new direct-acting antiviral drugs.

Midostaurin: a magic bullet that blocks mast cell expansion and activation.

Clinically relevant features in patients with systemic mastocytosis (SM) include the cosmetic burden of lesional skin, mediator-related symptoms, and organ damage resulting from mast cell (MC) infiltration in advanced forms of SM. Regardless of the SM variant, expansion of neoplastic MC in the skin and other organs is triggered by mutant forms of KIT, the most prevalent being D816V. Activation of MC with subsequent release of chemical mediators is often caused by IgE-dependent mechanisms in these patients. Midostaurin, also known as PKC412, blocks the kinase activity of wild-type KIT and KIT D816V, counteracts KIT-dependent growth of neoplastic MC, and inhibits IgE-dependent mediator secretion. Based on this activity-profile, the drug has been used for treatment of patients with advanced SM. Indeed, encouraging results have been obtained with the drug in a recent multi-center phase II trial in patients with advanced SM, with an overall response rate of 60% and a substantial decrease in the burden of neoplastic MC in various organs. Moreover, midostaurin improved the overall survival and relapse-free survival in patients with advanced SM compared with historical controls. In addition, midostaurin was found to improve mediator-related symptoms and quality of life, suggesting that the drug may also be useful in patients with indolent SM suffering from mediator-related symptoms resistant to conventional therapies or those with MC activation syndromes. Ongoing and future studies will determine the actual value of midostaurin-induced MC depletion and MC deactivation in these additional indications.

Neuroimaging evidence of brain abnormalities in mastocytosis.

Mastocytosis is a rare disease in which chronic symptoms are related to mast cell accumulation and activation. Patients can display depression-anxiety-like symptoms and cognitive impairment. The pathophysiology of these symptoms may be associated with tissular mast cell infiltration, mast cell mediator release or both. The objective of this study is to perform morphological or functional brain analyses in mastocytosis to identify brain changes associated with this mast cell disorder. We performed a prospective and monocentric comparative study to evaluate the link between subjective psycho-cognitive complaints, psychiatric evaluation and objective medical data using magnetic resonance imaging with morphological and perfusion sequences (arterial spin-labeled perfusion) in 39 patients with mastocytosis compared with 33 healthy controls. In the test cohort of 39 mastocytosis patients with psycho-cognitive complaints, we found that 49% of them had morphological brain abnormalities, mainly abnormal punctuated white matter abnormalities (WMA). WMA were equally frequent in cutaneous mastocytosis patients and indolent forms of systemic mastocytosis patients (42% and 41% of patients with WMA, respectively). Patients with WMA showed increased perfusion in the putamen compared with patients without WMA and with healthy controls. Putamen perfusion was also negatively correlated with depression subscores. This study demonstrates, for we believe the first time, a high prevalence of morphological and functional abnormalities in the brains of mastocytosis patients with neuropsychiatric complaints. Further studies are required to determine the mechanism underpinning this association and to ascertain its specificity.

Pre-transplant donor CD4- invariant NKT cell expansion capacity predicts the occurrence of acute graft-versus-host disease.

Clinically useful pre-transplant predictive factors of acute graft-versus-host-disease (aGVHD) after allogeneic hematopoietic stem cell transplantation (allo-SCT) are lacking. We prospectively analyzed HSC graft content in CD34+, NK, conventional T, regulatory T and invariant natural killer T (iNKT) cells in 117 adult patients before allo-SCT. Results were correlated with occurrence of aGVHD and relapse. In univariate analysis, iNKT cells were the only graft cell populations associated with occurrence of aGVHD. In multivariate analysis, CD4- iNKT/T cell frequency could predict grade II-IV aGVHD in bone marrow and peripheral blood stem cell (PBSC) grafts, while CD4- iNKT expansion capacity was predictive in PBSC grafts. Receiver operating characteristic analyses determined the CD4- iNKT expansion factor as the best predictive factor of aGVHD. Incidence of grade II-IV aGVHD was reduced in patients receiving a graft with an expansion factor above versus below 6.83 (9.7 vs 80%, P<0.0001), while relapse incidence at two years was similar (P=0.5).The test reached 94% sensitivity and 100% specificity in the subgroup of patients transplanted with human leukocyte antigen 10/10 PBSCs without active disease. Analysis of this CD4- iNKT expansion capacity test may represent the first diagnostic tool allowing selection of the best donor to avoid severe aGVHD with preserved graft-versus-leukemia effect after peripheral blood allo-SCT.

Striving to cure adult T-cell leukaemia/lymphoma: a role for allogeneic stem cell transplant?

Adult T-cell leukaemia/lymphoma (ATL) is an aggressive HTLV-1-related malignancy, rare outside of regions where the retrovirus is endemic. Although the use of antiviral therapy has improved outcomes, particularly for indolent forms of ATL, response to combination chemotherapy is poor and outcomes for aggressive subtypes remains dismal. Consolidation with allogeneic stem cell transplant (alloSCT) has an increasing role in the management of ATL in eligible patients, offering favourable long-term remission rates. However, relatively high-transplant-related mortality and issues with donor recruitment for certain ethnicities remain problematic. In this review, we discuss the rationale for and issues surrounding alloSCT in ATL in the context of conventional and emerging therapies.

Allogeneic stem cell transplantation for patients with mantle cell lymphoma who failed autologous stem cell transplantation: a national survey of the SFGM-TC.

Poly-chemotherapy plus rituximab followed by autologous stem cell transplantation (auto-SCT) is standard care for untreated young patients with mantle cell lymphoma (MCL). Despite this intensive treatment, transplant patients remain highly susceptible to relapse over time. The French SFGM-TC performed a national survey on reduced-intensity conditioning allogeneic stem cell transplantation (RIC-allo-SCT) for fit relapsed/refractory patients who failed after auto-SCT (n=106). Median times of relapse after auto-SCT, and from auto-SCT to RIC-allo-SCT were 28 months and 3.6 years, respectively. Sixty per cent of patients received at least three lines of treatment before RIC-allo-SCT. Conditioning regimens for RIC-allo-SCT were heterogeneous. Twenty patients experienced grade III/IV aGvHD, extensive cGvHD was reported in 28 cases. Median follow-up after RIC-allo-SCT was 45 months. Median PFS after RIC-allo-SCT was 30.1 months and median overall survival was 62 months. Treatment-related mortality (TRM) at 1 year and 3 years were estimated at 28% and 32%, respectively. A total of 52 patients died; major causes of death were related to toxicity (n=34) and MCL (n=11). Patients in good response before RIC-allo-SCT experienced a better PFS and OS. Our work highlights the need for new RIC-allo-SCT MCL-tailored approaches to reduce TRM, and early and late relapse.

Decreased tryptophan and increased kynurenine levels in mastocytosis associated with digestive symptoms.

The main metabolism pathway of tryptophan is protein formation, but it can also be metabolized into serotonin and kynurenine. Indoleamine 2,3-dioxygenase (IDO) is the enzyme that catalyzes the degradation of tryptophan into kynurenine. Mastocytosis is a heterogeneous disease characterized by mast cell accumulation in various tissues with 57% of patients having gastrointestinal involvement. We studied tryptophan metabolism in mastocytosis patients displaying or not gastrointestinal features and healthy subjects (n = 26 in each group). Mastocytosis patients with digestive symptoms displayed significantly increased kynurenine level and IDO activity as compared to healthy controls and mastocytosis patients without digestive symptoms. This could be linked to mast cell-mediated digestive inflammation among patients with mastocytosis. This work is the first focusing on kynurenine pathway in a mast cell disease and could help to understand the pathogenesis of digestive features in mastocytosis as well as in other mast cell-mediated diseases.