ALBERT

Description: Castleman disease (CD) describes a heterogeneous group of hematologic disorders that share characteristic lymph node histopathology. Patients of all ages present with either a solitary enlarged lymph node (unicentric CD) or multicentric lymphadenopathy (MCD) with systemic inflammation, cytopenias, and life-threatening multiple organ dysfunction resulting from a cytokine storm often driven by interleukin 6 (IL-6). Uncontrolled human herpesvirus-8 (HHV-8) infection causes approximately 50% of MCD cases, whereas the etiology is unknown in the remaining HHV-8-negative/idiopathic MCD cases (iMCD). The limited understanding of etiology, cell types, and signaling pathways involved in iMCD has slowed development of treatments and contributed to historically poor patient outcomes. Here, recent progress for diagnosing iMCD, characterizing etio-pathogenesis, and advancing treatments are reviewed. Several clinicopathological analyses provided the evidence base for the first-ever diagnostic criteria and revealed distinct clinical subtypes: thrombocytopenia, anasarca, fever, reticulin fibrosis/renal dysfunction, organomegaly (iMCD-TAFRO) or iMCD-not otherwise specified (iMCD-NOS), which are both observed all over the world. In 2014, the anti-IL-6 therapy siltuximab became the first iMCD treatment approved by the US Food and Drug Administration, on the basis of a 34% durable response rate; consensus guidelines recommend it as front-line therapy. Recent cytokine and proteomic profiling has revealed normal IL-6 levels in many patients with iMCD and potential alternative driver cytokines. Candidate novel genomic alterations, dysregulated cell types, and signaling pathways have also been identified as candidate therapeutic targets. RNA sequencing for viral transcripts did not reveal novel viruses, HHV-8, or other viruses pathologically associated with iMCD. Despite progress, iMCD remains poorly understood. Further efforts to elucidate etiology, pathogenesis, and treatment approaches, particularly for siltuximab-refractory patients, are needed.

Description: Castleman disease (CD) describes a group of at least 4 disorders that share a spectrum of characteristic histopathological features but have a wide range of etiologies, presentations, treatments, and outcomes. CD includes unicentric CD (UCD) and multicentric CD (MCD), the latter of which is divided into idiopathic MCD (iMCD), human herpes virus-8 (HHV8)-associated MCD (HHV8-MCD), and polyneuropathy, organomegaly, endocrinopathy, monoclonal plasma cell disorder, skin changes (POEMS)-associated MCD (POEMS-MCD). iMCD can be further subclassified into iMCD–thrombocytopenia, ascites, reticulin fibrosis, renal dysfunction, organomegaly (iMCD-TAFRO) or iMCD–not otherwise specified (iMCD-NOS). Advances in diagnosis, classification, pathogenesis, and therapy are substantial since the original description of UCD by Benjamin Castleman in 1954. The advent of effective retroviral therapy and use of rituximab in HHV8-MCD have improved outcomes in HHV8-MCD. Anti–interleukin-6–directed therapies are highly effective in many iMCD patients, but additional therapies are required for refractory cases. Much of the recent progress has been coordinated by the Castleman Disease Collaborative Network (CDCN), and further progress will be made by continued engagement of physicians, scientists, and patients. Progress can also be facilitated by encouraging patients to self-enroll in the CDCN’s ACCELERATE natural history registry (#NCT02817997; www.CDCN.org/ACCELERATE).

Description: Multicentric Castleman's disease (MCD) describes a heterogeneous group of disorders involving proliferation of morphologically benign lymphocytes due to excessive proinflammatory hypercytokinemia, most notably of interleukin-6. Patients demonstrate intense episodes of systemic inflammatory symptoms, polyclonal lymphocyte and plasma cell proliferation, autoimmune manifestations, and organ system impairment. Human herpes virus-8 (HHV-8) drives the hypercytokinemia in all HIV-positive patients and some HIV-negative patients. There is also a group of HIV-negative and HHV-8-negative patients with unknown etiology and pathophysiology, which we propose referring to as idiopathic MCD (iMCD). Here, we synthesize what is known about iMCD pathogenesis, present a new subclassification system, and propose a model of iMCD pathogenesis. MCD should be subdivided into HHV-8-associated MCD and HHV-8-negative MCD or iMCD. The lymphocyte proliferation, histopathology, and systemic features in iMCD are secondary to hypercytokinemia, which can occur with several other diseases. We propose that 1 or more of the following 3 candidate processes may drive iMCD hypercytokinemia: systemic inflammatory disease mechanisms via autoantibodies or inflammatory gene mutations, paraneoplastic syndrome mechanisms via ectopic cytokine secretion, and/or a non-HHV-8 virus. Urgent priorities include elucidating the process driving iMCD hypercytokinemia, identifying the hypercytokine-secreting cell, developing consensus criteria for diagnosis, and building a patient registry to track cases.

Description: Key Points HIV-negative UCD and iMCD are heterogeneous at the clinical, immunophenotypic, and pathologic levels. Complete surgical resection is the primary option of treatment of UCD, while siltuximab is more effective for iMCD than rituximab.

Description: Idiopathic multicentric Castleman disease (iMCD) is a rare and poorly understood hematologic disorder characterized by lymphadenopathy, systemic inflammation, cytopenias, and life-threatening multiorgan dysfunction. Interleukin-6 (IL-6) inhibition effectively treats approximately one-third of patients. Limited options exist for nonresponders, because the etiology, dysregulated cell types, and signaling pathways are unknown. We previously reported 3 anti-IL-6 nonresponders with increased mTOR activation who responded to mTOR inhibition with sirolimus. We investigated mTOR signaling in tissue and serum proteomes from iMCD patients and controls. mTOR activation was increased in the interfollicular space of iMCD lymph nodes (N = 26) compared with control lymph nodes by immunohistochemistry (IHC) for pS6, p4EBP1, and p70S6K, known effectors and readouts of mTORC1 activation. IHC for pS6 also revealed increased mTOR activation in iMCD compared with Hodgkin lymphoma, systemic lupus erythematosus, and reactive lymph nodes, suggesting that the mTOR activation in iMCD is not just a product of lymphoproliferation/inflammatory lymphadenopathy. Further, the degree of mTOR activation in iMCD was comparable to autoimmune lymphoproliferative syndrome, a disease driven by mTOR hyperactivation that responds to sirolimus treatment. Gene set enrichment analysis of serum proteomic data from iMCD patients (n = 88) and controls (n = 42) showed significantly enriched mTORC1 signaling. Finally, functional studies revealed increased baseline mTOR pathway activation in peripheral monocytes and T cells from iMCD remission samples compared with healthy controls. IL-6 stimulation augmented mTOR activation in iMCD patients, which was abrogated with JAK1/2 inhibition. These findings support mTOR activation as a novel therapeutic target for iMCD, which is being investigated through a trial of sirolimus (NCT03933904).

Description: Idiopathic multicentric Castleman disease (iMCD) is a rare lymphoproliferative disorder. The anti–interleukin 6 (IL-6) therapy siltuximab is not available everywhere, and is not effective for over one-half of patients. Alternative treatment approaches are urgently needed. In the first iMCD clinical trial directed against a target other than IL-6 signaling, we investigated a thalidomide-cyclophosphamide-prednisone (TCP) regimen in newly diagnosed iMCD patients. This single-center, single-arm, phase 2 study enrolled 25 newly diagnosed iMCD patients between June 2015 and June 2018. The TCP regimen (thalidomide 100 mg daily for 2 years; oral cyclophosphamide 300 mg/m2 weekly for 1 year; prednisone 1 mg/kg twice a week for 1 year) was administered for 2 years or until treatment failure. The primary end point was durable tumor and symptomatic response for at least 24 weeks. Twelve patients (48%) achieved the primary end point with no relapse, 3 patients (12%) demonstrated stable disease, and 10 patients (40%) were evaluated as treatment failure. Even when considering all patients, there were significant (P 〈 .05) improvements in median symptom score, IL-6 level, hemoglobin, erythrocyte sedimentation rate, albumin, and immunoglobulin G. Among responders, the median levels of all evaluated parameters significantly improved, to the normal range, after treatment. The regimen was well tolerated. One patient died of pulmonary infection and 1 patient had a grade 3 adverse event (rash); 2 patients died following disease progression. Estimated 1-year progression-free survival and overall survival were 60% and 88%, respectively. The TCP regimen is an effective and safe treatment of newly diagnosed iMCD patients, particularly when siltuximab is unavailable. This trial was registered at www.clinicaltrials.gov as #NCT03043105.

Description: Background: Multicentric Castleman disease (MCD) describes a heterogeneous group of poorly-understood diseases involving proinflammatory hypercytokinemia that ultimately results in systemic inflammatory symptoms, generalized lymphadenopathy, multiple organ system dysfunction, and even death. HHV-8 is responsible for driving MCD in immunosuppressed patients (HHV-8-associated MCD). There is also a cohort of HHV-8-negative MCD cases, referred to as idiopathic MCD (iMCD), in which the etiology remains unknown. No formal diagnostic criteria exist for iMCD, and knowledge is limited to small case series and case reports. Objectives: We conducted a systematic literature review to describe demographic, clinical, and laboratory features of iMCD as well as the treatments currently used in practice. Methods: PubMed was queried using a comprehensive list of terms to identify all published cases of HHV-8-negative MCD. Criteria for study inclusion were as follows: (1) Pathology-confirmed Castleman disease in multiple lymph nodes; (2) Exclusion of another cause of Castleman-like histopathology, such as SLE or POEMS syndrome; (3) Negative testing for HHV-8 via PCR of blood, PCR of lymph node tissue, serum serologies, and/or IHC for LANA-1; (4) Written in English and published from January 1995 to July 2013; and (5) Availability of specified minimum data elements. HIV-positive cases were excluded. Inclusion criteria were confirmed by three independent investigators, who also extracted data into a standardized database. Case report authors were contacted to gather additional data in a standardized case report form. Results: 3,428 articles were identified on PubMed. Initial evaluation for exclusion criteria yielded 1,951 MCD cases; 629 patients were HIV-positive (32%). Of the 999 HIV-negative and 323 HIV-unknown MCD cases, 626 were HHV-8 negative (32% of total MCD), 517 were HHV-8-unknown (26%), and 179 were HHV-8-positive (9%).129 cases of HHV-8-negative MCD met all inclusion criteria and were included in the final analysis. 58% were male and median age was 50 years (range: 2-80). Frequently reported clinical features included: fever (51/64), enlarged liver and/or spleen (45/60), pleural effusion (29/38), edema (26/36), and weight loss (21/29). There were 43 plasmacytic, 26 mixed, and 23 hyaline vascular cases out of 108 cases that reported histopathological subtype. The most commonly reported laboratory abnormalities included elevated CRP (70/79), anemia (76/90), hypergammaglobulinemia (63/82), hypoalbuminemia (57/63), elevated IL-6 (57/63), and positive ANA (14/38). Of cases with abnormal platelet levels, 28 had thrombocytopenia and 14 had thrombocytosis. There were 19 reported cases with elevated soluble IL-2R levels and 15 with elevated VEGF. 27 patients were diagnosed with a malignancy before (5), concurrently with (12), or after (10) diagnosis. Most commonly employed first line therapies included corticosteroid monotherapy (36%), combinations of cytotoxic chemotherapies (36%) that included regimens with cytoxan (17%) and rituxan (12%), and anti-IL-6 therapies, such as siltuximab and tocilizumab, without a cytotoxic agent (10%). Thalidomide, bortezomib, anakinra, and IVIG were used less frequently. Patients experienced no response (21%), partial response (42%), and complete response (37%) to first-line therapies. Failure (relapse, death, additional treatment) of first line therapy occurred in 41% of patients, and median time to treatment failure was 6 months. Overall, 22% of patients died by the time of most recent follow up (median: 28 months) with median length of survival among fatal cases being 26 months (range: 1-120). The most common causes of death were septic shock, multi-organ failure, including renal and cardiac, pulmonary complications, and malignancy. Conclusion: This study identified a significant proportion of MCD patients who are HIV-negative and HHV-8-negative (iMCD). 45% of patients did not demonstrate the plasmacytic variant alone, which has been classically associated with MCD. It is striking that 22% of patients died by the time of most recent follow up, which had a median length of 26 months. Despite the many limitations of analyzing case reports, this study provides the most comprehensive data on HHV-8-negative MCD to date. A global natural history study and Castleman disease registry are urgently needed to gather more extensive data on MCD. Disclosures Fajgenbaum: Janssen Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees. Off Label Use: Cyclophosphamide, rituximab, tocilizumab, thalidomide, bortezomib, anakinra, and intravenous immunoglobulin will be presented as drugs used in HHV-8-negative MCD. It is very important to inventory the treatments that a physician has available when conventional therapies do not work, which is frequent in MCD. At the time that this data set was assembled, there were no FDA approved therapies for this orphan disease. van Rhee:Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees.

Description: Idiopathic multicentric Castleman disease (iMCD) is a rare hematologic illness involving episodic disease flares with polyclonal cytokine-induced lymphoproliferation, systemic inflammation, and life-threatening multi-organ dysfunction. iMCD is further classified by clinical features and the most severe cases of iMCD often fall into the thrombocytopenia, anasarca, fever/elevated C-reactive protein, reticulin myelofibrosis, renal dysfunction, and organomegaly (TAFRO) clinical subtype. A cytokine storm involving interleukin(IL)-6 drives disease pathogenesis in a subset of patients, however only 34% of patients were found to respond to anti-IL-6 therapy with siltuximab in its registrational clinical trial. The identification of next generation therapeutics for iMCD-TAFRO patients has been challenging as the etiology, pathological cell types, and signaling pathways involved in iMCD-TAFRO are largely unknown. In this study, we aimed to identify cellular drivers and pathophysiological mechanisms of iMCD-TAFRO through the use of an unbiased multi-omics approach. We obtained paired bulk peripheral blood mononuclear cells (PBMCs) from a cohort of ten iMCD-TAFRO patients isolated during disease flare and clinical remission. These paired PBMC samples were utilized for flow cytometry to assess immune cell frequency and phenotype between iMCD-TAFRO flare and remission as well as between flare and age/sex matched healthy donors (n = 10). Three paired iMCD-TAFRO samples were also selected for transcriptional profiling using single-cell RNA sequencing (scRNAseq). We observed phenotypic differences across the T cell, monocyte, and NK cell compartments. We observed a significant increase in the frequency of CD8 T cells within the T cell compartment as well as an increased frequency of granzyme B and perforin expressing CD8 T cells in iMCD-TAFRO flare compared to healthy donors. We also observed a significant increase in the frequency of CD56+ NK cells within the NK cell compartment and a significant increase in the frequency of CD14+ monocytes within the monocyte compartment during iMCD-TAFRO flare compared to healthy donors. Together, these data suggest activation and involvement of CD8 T cell, NK cell, and monocyte subsets during iMCD-TAFRO flare. We next utilized Gene Set Enrichment Analysis (GSEA) of our single-cell transcriptomics dataset to ask whether circulating immune cell frequencies display enrichment of the 50 Hallmark gene sets during flare compared to remission across three iMCD-TAFRO patients. We found significant enrichment (FDR 〈 0.01) of genes within the Interferon Alpha Response gene set in circulating non-naïve CD8 T cells, classical monocytes, nonclassical monocytes, NK cells, and dendritic cells. These data suggest that a number of circulating immune cell populations may be responding to Type I interferon (IFN-I) during iMCD-TAFRO flare. In addition, our group has recently reported mTORC1 activation in iMCD and has characterized in three iMCD-TAFRO patients a clinical response following mTOR inhibition with sirolimus. Within our scRNAseq dataset, we identified mTORC1 signaling to be enriched only in circulating classical and nonclassical monocytes during flare. Having observed enrichment of both the Interferon Alpha Response Gene set and the mTORC1 signaling gene set in circulating monocytes, we then asked whether the relative expression of IFN-I response genes and mTORC1 signaling genes are correlated within circulating classical and nonclassical monocytes. Indeed, we observed a significant positive correlation between the average relative expression of mTORC1 signaling genes and IFN-I Response genes across classical, but not nonclassical, monocytes from all three iMCD-TAFRO patients (all R2 ≥0.6, p

Description: Introduction: Castleman disease (CD) is an uncommon lymphoproliferative disorder of unclear etiology. CD is broadly subclassified into unicentric (UCD) and multicentric (MCD) disease based on based on clinical, radiological, laboratory and histomorphological findings. UCD presents with minimal symptoms, is restricted to a single lymph node station, and excision is usually curative. Multicentric CD, in contrast, presents with systemic inflammatory symptoms, multicentric lymphadenopathy, and vital organ dysfunction. MCD is further subclassified into Human Herpesvirus-8(HHV-8)-associated MCD and HHV-8-negative/idiopathic MCD (iMCD), the etiology of which is poorly understood. Histologically, UCD frequently shows a hyaline vascular pattern with atretic follicles, thickened mantle zones and increased interfollicular vascularity with hyalinization. iMCD frequently shows increased interfollicular plasma cells and hyperplastic follicles. iMCD is also characterized by a systemic hypercytokinemia that includes IL-6, VEGF, IL-2, TNF-α, IL-10 and CXCL13. However, the cell(s) involved in initiating and amplifying the cytokine network are unclear. We combined histomorphology and cytokine in situ hybridization to identify the hypercytokine-producing cells in lymph nodes from CD patients. In addition, T and B lymphocytes play important roles in initiating and amplifying the cytokine response and their clonality has not been well-studied in CD. Here, we performed deep sequencing of the immunoglobulin heavy chain and T cell receptor gene loci. Methods: Lymph node biopsies from patients with UCD and iMCD were identified from the pathology archives of the Children's Hospital of Philadelphia. 17 UCD cases and 8 HHV8-negative iMCD cases were examined. Reactive lymph nodes (N=10) with plasmacytosis and/or other CD-like features served as controls. Cytokine expression was determined by RNA in situ hybridization (RNAscope) on formalin fixed paraffin embedded tissue. IL-6, IL-6R, VEGF, IL-10, TNF-α, IL-1β, IL-2, and IL-8 RNA expression patterns were analyzed in conjunction with histomorphological features. Expression was manually quantified with a semi-quantitative grading scale (0-4) per manufacturer recommendations and statistical analysis was performed using the Chi-square test. Fresh frozen lymph node tissue was utilized for deep sequencing of the TCR Vβ and IgH gene loci. VDJ usage, clonal frequency and CDR3 sequence was determined and compared between subtypes of CD and reactive lymph node controls. Results: Lymph nodes from patients with iMCD express significantly higher levels of VEGF compared to patients with UCD and controls (75% vs. 29% vs. 0%; p=0.014). Atretic follicles and interfollicular regions were the source of increased VEGF expression. Potential cell types responsible for the increased VEGF production in these regions are follicular dendritic cells in the atretic follicles and plasma cells in the interfollicular areas. IL-6 expression was also significantly higher in iMCD cases compared to UCD and controls (75% vs. 25% vs. 20%, p=0.026) in a subset of cells within the interfollicular regions. This cellular source of the excess IL-6 in the interfollicular region may be endothelial cells. Thus, follicular dendritic cells in the germinal centers and endothelial cells, T cells, and plasma cells in the interfollicular spaces are potential sources for increased VEGF and IL-6. IL-6R, IL-10, TNF-α, IL-1β, IL-2, and IL-8 showed no significant differences between the various subtypes of CD. Deep sequencing of the TCRα gene loci revealed mildly expanded clonal T-cell populations (5% of total sequences) in a subset of iMCD cases (2/6) and UCD cases (1/9) compared to controls (0/15). B cell populations were polyclonal in both subtypes of CD and in reactive lymph nodes. Conclusion: The findings suggest that cells in the interfollicular region and atretic follicles in the lymph nodes are a potential source of the systemic hypercytokinemia in iMCD. The locations and patterns of cytokine expression implicate follicular dendritic cells, endothelial cells, and plasma cells specifically as potential hypercytokine-producing cells. Additionally, T cells in CD show oligoclonality in some cases and may play an important role in initiating or amplifying the immune response in CD. Disclosures Fajgenbaum: Janssen Pharmaceuticals, Inc.: Research Funding.