Project description:Langerhans cell histiocytosis (LCH) is a potentially fatal condition characterized by granulomatous lesions with characteristic clonal mononuclear phagocytes (MNPs) harboring activating somatic mutations in mitogen-activated protein kinase (MAPK) pathway genes, most notably BRAFV600E. We recently discovered that the BRAFV600E mutation can also affect multipotent hematopoietic progenitor cells (HPCs) in multisystem LCH disease. How the BRAFV600E mutation in HPCs leads to LCH is not known. Here we show that enforced expression of the BRAFV600E mutation in early mouse and human multipotent HPCs induced a senescence program that led to HPC growth arrest, apoptosis resistance and a senescence-associated secretory phenotype (SASP). SASP, in turn, promoted HPC skewing toward the MNP lineage, leading to the accumulation of senescent MNPs in tissue and the formation of LCH lesions. Accordingly, elimination of senescent cells using INK-ATTAC transgenic mice, as well as pharmacologic blockade of SASP, improved LCH disease in mice. These results identify senescent cells as a new target for the treatment of LCH.

| S-EPMC9295868 | biostudies-literature

Single-agent dabrafenib for BRAFV600E-mutated histiocytosis.

Project description: Not available

| S-EPMC5865413 | biostudies-literature

BRAF V600E mutation correlates with suppressive tumor immune microenvironment and reduced disease-free survival in Langerhans cell histiocytosis.

Project description:Langerhans cell histiocytosis (LCH) is a neoplasm of myeloid origin characterized by a clonal proliferation of CD1a(+)/CD207(+) dendritic cells. Recurrent BRAF V600E mutation has been reported in LCH. In the present report, we confirm the feasibility of the high-specificity monoclonal antibody VE1 for detecting BRAF V600E mutation in 36/97 (37.1%) retrospectively enrolled patients with LCH; concordant immunohistochemistry and Sanger sequencing results were seen in 94.8% of cases. We then assessed the tumor immune microenvironment status in LCH, and found that the GATA binding protein 3 (GATA3)(+)/T-bet(+) ratio could distinguish between clinical multi-system/single-system (SS) multifocal and SS unifocal LCH. Notably, we found that BRAF V600E mutation is significantly correlated with increased programmed cell death 1 ligand 1 (PDL1) expression and forkhead box protein 3 (FOXP3)(+) regulatory T cells (p < 0.001, 0.009, respectively). Moreover, Cox multivariate survival analysis showed that BRAF V600E mutation and PDL1 were independent prognostic factors of poor disease-free survival (DFS) in LCH (hazard ratio [HR] = 2.38, 95% confidence interval [CI] 1.02-5.56, p = 0.044; HR = 3.06, 95%CI 1.14-7.14, p = 0.025, respectively), and the superiority of PDL1 in sensitivity and specificity as biomarker for DFS in LCH was demonstrated by receiver operator characteristic (ROC) curves when compared with BRAF V600E and risk category. Collectively, this study identifies for the first time relationship between BRAF V600E mutation and a suppressive tumor immune microenvironment in LCH, resulting in disruption of host-tumor immune surveillance, which is DFS. Our findings may provide a rationale for combining immunotherapy and BRAF-targeted therapy for treating patients with BRAF V600E mutant LCH.

| S-EPMC5006923 | biostudies-literature

ddPCR Analysis Reveals BRAF V600E Mutations Are Infrequent in Isolated Pituitary Langerhans Cell Histiocytosis Patients.

Project description:Langerhans cell histiocytosis (LCH) is an inflammatory myeloid neoplasia with a highly variable clinical presentation affecting people of all ages. Mutations in BRAF V600E are the most identifiable molecular alteration in LCH although its incidence in pediatric patients with isolated pituitary stalk involvement is not well described. Pediatric patients with LCH and isolated pituitary stalk involvement typically present with central diabetes insipidus. Diagnosis requires a transcranial biopsy which often yields scant tissue. We sought to determine the prevalence of BRAF V600E mutations in patients with isolated pituitary stalk LCH using digital droplet polymerase chain reaction because this method requires minimal tumor DNA. We identified 8 patients with isolated pituitary stalk thickening who underwent a biopsy at Children's Hospital Colorado from January 2001 to December 2019, as well as 6 patients with systemic LCH diagnosed by biopsy in the same period as a comparison. Only one out of the 8 patients with isolated thickened pituitary stalk was found to have a detectable BRAF V600E mutation. Five out of the 6 patients with systemic LCH had a detectable BRAF V600E mutation. In our series, BRAF V600E mutations are rare in pediatric patients with LCH and isolated pituitary stalk involvement.

| S-EPMC8453605 | biostudies-literature

Mutations in SLC29A3, encoding an equilibrative nucleoside transporter ENT3, cause a familial histiocytosis syndrome (Faisalabad histiocytosis) and familial Rosai-Dorfman disease.

Project description:The histiocytoses are a heterogeneous group of disorders characterised by an excessive number of histiocytes. In most cases the pathophysiology is unclear and treatment is nonspecific. Faisalabad histiocytosis (FHC) (MIM 602782) has been classed as an autosomal recessively inherited form of histiocytosis with similarities to Rosai-Dorfman disease (RDD) (also known as sinus histiocytosis with massive lymphadenopathy (SHML)). To elucidate the molecular basis of FHC, we performed autozygosity mapping studies in a large consanguineous family and identified a novel locus at chromosome 10q22.1. Mutation analysis of candidate genes within the target interval identified biallelic germline mutations in SLC29A3 in the FHC kindred and in two families reported to have familial RDD. Analysis of SLC29A3 expression during mouse embryogenesis revealed widespread expression by e14.5 with prominent expression in the central nervous system, eye, inner ear, and epithelial tissues including the gastrointestinal tract. SLC29A3 encodes an intracellular equilibrative nucleoside transporter (hENT3) with affinity for adenosine. Recently germline mutations in SLC29A3 were also described in two rare autosomal recessive disorders with overlapping phenotypes: (a) H syndrome (MIM 612391) that is characterised by cutaneous hyperpigmentation and hypertrichosis, hepatomegaly, heart anomalies, hearing loss, and hypogonadism; and (b) PHID (pigmented hypertrichosis with insulin-dependent diabetes mellitus) syndrome. Our findings suggest that a variety of clinical diagnoses (H and PHID syndromes, FHC, and familial RDD) can be included in a new diagnostic category of SLC29A3 spectrum disorder.

| S-EPMC2816679 | biostudies-literature

A study of pathological characteristics and BRAF V600E status in Langerhans cell histiocytosis of Vietnamese children.

Project description:BackgroundLangerhans cell histiocytosis (LCH) is more common in children than adults and involves many organs. In children, the BRAF V600E mutation is associated with recurrent and high-risk LCH.MethodsWe collected paraffin blocks of 94 pediatric LCH patients to detect BRAF V600E mutation by sequencing. The relationship between BRAF V600E status and clinicopathological parameters were also critically analyzed.ResultsBRAF V600E mutation exon 15 was detected in 45 cases (47.9%). Multiple systems LCH showed a significantly higher BRAF V600E mutation rate than a single system (p=.001). No statistical significance was evident for other clinical characteristics such as age, sex, location, risk organs involvement, and CD1a expression.ConclusionsIn Vietnamese LCH children, the proportion of BRAF V600E mutational status was relatively high and related to multiple systems.

| S-EPMC7987525 | biostudies-literature

BRAF V600E is associated with higher incidence of second cancers in adults with Langerhans cell histiocytosis.

Project description:In this retrospective study, BRAF mutation status did not correlate with disease extent or (event-free) survival in 156 adults with Langerhans cell histiocytosis. BRAFV600E was associated with an increased incidence of second malignancies, often comprising hematological cancers, which may be clonally related.

| S-EPMC10797504 | biostudies-literature

Rosai dorfman disease of the orbit.

Project description:ObjectiveTo report the clinico-histopathologic features, management and outcome of Rosai-Dorfman disease of the orbit.DesignNon-comparative case series.ResultsRosai-Dorfman disease of the orbit constituted 0.09% of all ocular specimens received at our Institute, presenting with a firm rubbery mass causing proptosis; bilateral in 4 (57%) cases. The median age at presentation was 13 years (range 5-65); median duration of symptoms was 6 (range 3-15) years. Lymphadenopathy was noted in 4 (57%); extranodal involvement in 3 (43%). After biopsy, 3 cases were treated with systemic corticosteroids, 2 cases developed local recurrence that responded to systemic corticosteroid therapy. Polymorphous population of lymphocytes, plasma cells, and characteristic S-100-positive histiocytes showing emperipolesis were pathognomonic histologic features.ConclusionRosai-Dorfman disease of the orbit, although rare, should be considered in young individuals with chronic proptosis with rubbery masses. Excision and corticosteroid therapy provide a favorable outcome.

| S-EPMC2474646 | biostudies-literature

Dabrafenib, alone or in combination with trametinib, in BRAF V600-mutated pediatric Langerhans cell histiocytosis.

Project description:Langerhans cell histiocytosis (LCH) is a rare, heterogenous, neoplastic disorder primarily affecting children. BRAF mutations have been reported in >50% of patients with LCH. The selective BRAF inhibitor, dabrafenib, in combination with the MEK1/2 inhibitor, trametinib, has been approved in select BRAF V600-mutant solid tumors. Two open-label phase 1/2 studies were conducted in pediatric patients with BRAF V600-mutant, recurrent/refractory malignancies treated with dabrafenib monotherapy (CDRB436A2102; NCT01677741) or dabrafenib plus trametinib (CTMT212X2101; NCT02124772). The primary objectives of both studies were to determine safe and tolerable doses that achieve similar exposure to the approved doses for adults. Secondary objectives included safety, tolerability, and preliminary antitumor activity. Thirteen and 12 patients with BRAF V600-mutant LCH received dabrafenib monotherapy and in combination with trametinib, respectively. Investigator-assessed objective response rates per Histiocyte Society criteria were 76.9% (95% confidence interval [CI], 46.2-95.0) and 58.3% (95% CI, 27.7-84.8) in the monotherapy and combination studies, respectively. More than 90% of responses were ongoing at study completion. The most common treatment-related adverse events (AEs) were vomiting and increased blood creatinine with monotherapy and pyrexia, diarrhea, dry skin, decreased neutrophil count, and vomiting with combination therapy. Two patients each discontinued treatment with monotherapy and combination therapy because of AEs. Overall, dabrafenib monotherapy or in combination with trametinib demonstrated clinical efficacy and manageable toxicity in relapsed/refractory BRAF V600-mutant pediatric LCH, with most responses ongoing. Safety was consistent with that reported in other pediatric and adult conditions treated with dabrafenib plus trametinib.

| S-EPMC10393756 | biostudies-literature