Molecular profiling of blastic plasmacytoid dendritic cell neoplasm reveals a unique pattern and suggests selective sensitivity to NF-kB pathway inhibition

Newly-Discovered Neural Features Expand the Pathobiological Knowledge of Blastic Plasmacytoid Dendritic Cell Neoplasm

Simple Summary

For the first time, neuronal features are described in blastic plasmacytoid dendritic cell neoplasm (BPDCN) by a complex array of molecular techniques, including microRNA and gene expression profiling, RNA and Chromatin immunoprecipitation sequencing, and immunohistochemistry. The discovery of unexpected neural features in BPDCN may change our vision of this disease, leading to the designing of a new BPDCN cell model and to re-thinking the relations occurring between BPDCN and nervous system. The observed findings contribute to explaining the extreme tumor aggressiveness and also to propose novel therapeutic targets. In view of this, the identification, in this work of new potential neural metastatic inducers might open the way to therapeutic approaches for BPDCN patients based on the use of anti-neurogenic agents.

Abstract

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and highly aggressive hematologic malignancy originating from plasmacytoid dendritic cells (pDCs). The microRNA expression profile of BPDCN was compared to that of normal pDCs and the impact of miRNA dysregulation on the BPDCN transcriptional program was assessed. MiRNA and gene expression profiling data were integrated to obtain the BPDCN miRNA-regulatory network. The biological process mainly dysregulated by this network was predicted to be neurogenesis, a phenomenon raising growing interest in solid tumors. Neurogenesis was explored in BPDCN by querying different molecular sources (RNA sequencing, Chromatin immunoprecipitation-sequencing, and immunohistochemistry). It was shown that BPDCN cells upregulated neural mitogen genes possibly critical for tumor dissemination, expressed neuronal progenitor markers involved in cell migration, exchanged acetylcholine neurotransmitter, and overexpressed multiple neural receptors that may stimulate tumor proliferation, migration and cross-talk with the nervous system. Most neural genes upregulated in BPDCN are currently investigated as therapeutic targets.

A case series of blastic plasmacytoid dendritic cell neoplasia

Blastic plasmacytoid dendritic cell neoplasm (BPDCN), an extremely rare and aggressive tumor, derives from plasmacytoid dendritic cell precursors and is characterized by CD4 and CD56 positivity accompanied by the expression of isolated myeloid, B- or T-cell lineage markers. Despite the recent introduction of specific targeted therapies, prognosis is still poor with a median overall survival of one year, and allogeneic bone marrow transplantation remains the only curative treatment in eligible patients. In this series, we described two cases of adult BPDCN treated with high dose cytarabine and methotrexate and autologous hematopoietic stem cell transplantation, or fludarabine, cytarabine, and idarubicin achieving the first a complete lasting remission, while the second only a transient improvement in skin lesions.

Blastic Plasmacytoid Dendritic Cell Neoplasm: Progress in Cell Origin, Molecular Biology, Diagnostic Criteria and Therapeutic Approaches

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematological malignancy characterized by recurrent skin nodules, an aggressive clinical course with rapid involvement of hematological organs, and a poor prognosis with poor overall survival. BPDCN is derived from plasmacytoid dendritic cells (pDCs) and its pathogenesis is unclear. The tumor cells show aberrant expression of CD4, CD56, interleukin-3 receptor alpha chain (CD123), blood dendritic cell antigen 2 (BDCA 2/CD303), blood dendritic cell antigen 4 (BDCA4) and transcription factor (E protein) E2-2 (TCF4). The best treatment drugs are based on experience by adopting those used for either leukemia or lymphoma. Relapse with drug resistance generally occurs quickly. Stem cell transplantation after the first complete remission is recommended and tagraxofusp is the first targeted therapy. In this review, we summarize the differentiation of BPDCN from its cell origin, its connection with normal pDCs, clinical characteristics, genetic mutations and advances in treatment of BPDCN. This review provides insights into the mechanisms of and new therapeutic approaches for BPDCN.

Novel Therapeutic Approaches in Blastic Plasmacytoid Dendritic Cell Neoplasm (BPDCN): Era of Targeted Therapy

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematologic malignancy arising from the aberrant transformation of plasmacytoid dendritic cells (pDCs) and involving skin, bone marrow, lymph nodes, and central nervous system. Characteristically unique from other myeloid neoplasms, BPDCN cells express CD4, CD56, and CD123 as well as TCL-1 and TCF4 in almost all cases. Historically, this malignancy has exhibited a poor prognosis, with median survival of less than 2 years. Traditional treatment approaches have involved conventional cytotoxic chemotherapy followed by hematopoietic stem cell transplantation; however, patients frequently relapse with chemotherapy-resistant disease. We have recently entered a modern era of therapy with targeting of CD123, with first-in-class agent tagraxofusp, a CD123- targeted agent approved by the US Food and Drug Administration for therapy of patients with BPDCN ages 2 and older. Relapsed and refractory BPDCN remains an elusive therapeutic challenge, but better understanding of the underlying pathophysiology has led to the development of other CD123-targeted agents and combination therapy, as well as agents targeting beyond CD123. Specifically, the use of venetoclax in targeting BCL2 has been promising in BPDCN treatment. This review will focus on the underlying diagnostic markers of BPDCN which have led to novel targeted treatment strategies, as well as future directions in therapy we can expect in coming years.

Transcriptomic and genomic heterogeneity in blastic plasmacytoid dendritic cell neoplasms: from ontogeny to oncogenesis

Oncogenesis and ontogeny of blastic plasmacytoid dendritic cell neoplasm (BPDCN) remain uncertain, between canonical plasmacytoid dendritic cells (pDCs) and AXL+ SIGLEC6+ DCs (AS-DCs). We compared 12 BPDCN to 164 acute leukemia by Affymetrix HG-U133 Plus 2.0 arrays: BPDCN were closer to B-cell acute lymphoblastic leukemia (ALL), with enrichment in pDC, B-cell signatures, vesicular transport, deubiquitination pathways, and AS-DC signatures, but only in some cases. Importantly, 1 T-cell ALL clustered with BPDCN, with compatible morphology, immunophenotype (cCD3+ sCD3- CD123+ cTCL1+ CD304+), and genetics. Many oncogenetic pathways are deregulated in BPDCN compared with normal pDC, such as cell-cycle kinases, and importantly, the transcription factor SOX4, involved in B ontogeny, pDC ontogeny, and cancer cell invasion. High-throughput sequencing (HaloPlex) showed myeloid mutations (TET2, 62%; ASXL1, 46%; ZRSR2, 31%) associated with lymphoid mutations (IKZF1), whereas single-nucleotide polymorphism (SNP) array (Affymetrix SNP array 6.0) revealed frequent losses (mean: 9 per patient) involving key hematological oncogenes (RB1, IKZF1/2/3, ETV6, NR3C1, CDKN2A/B, TP53) and immune response genes (IFNGR, TGFB, CLEC4C, IFNA cluster). Various markers suggest an AS-DC origin, but not in all patients, and some of these abnormalities are related to the leukemogenesis process, such as the 9p deletion, leading to decreased expression of genes encoding type I interferons. In addition, the AS-DC profile is only found in a subgroup of patients. Overall, the cellular ontogenic origin of BPDCN remains to be characterized, and these results highlight the heterogeneity of BPDCN, with a risk of a diagnostic trap.

Survival outcomes in blastic plasmacytoid dendritic cell neoplasm by first-line treatment and stem cell transplant

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematologic malignancy with dismal clinical outcomes. Conventional chemotherapies such cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) and hyperfractionated cyclophosphamide, vincristine, doxorubicin, dexamethasone alternating with high-dose cytarabine and methotrexate (CVAD) have been commonly used for the BPDCN treatment until a recent study showed promising outcomes in patients treated with SL-401 (Tagraxofusp). In this single-institution retrospective study, we identified a total of 49 consecutive BPDCN patients. Among 42 patients who received treatment, hyper-CVAD regimen was associated with higher complete response rate compared with CHOP-based regimens or SL-401 (91% vs 50% vs 50%), although the difference did not achieve statistical significance. Furthermore, there was no significant overall survival (OS) difference between patients treated with SL-401 vs other chemotherapies as their first-line treatment (hazard ratio = 1.597; 95% CI, 0.460-5.548; P = .431). Of note, patients who received allogeneic stem cell transplant (allo-SCT) had significantly longer OS (hazard ratio = 0.160; 95% CI, 0.0453-0.56; P = .041). Extent of disease (skin vs bone marrow vs both) or younger age (<60 years old) did not have significant prognostic impact on OS. Collectively, our study confirmed the survival benefit of allo-SCT and suggests that conventional and intensive chemotherapies such as CHOP and hyper-CVAD as well as SL-401 would be comparable first-line choice for the BPDCN patients.

Blastic plasmacytoid dendritic cell neoplasm with genetic mutations in multiple epigenetic modifiers: a case report

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare, aggressive hematodermic malignancy derived from plasmacytoid dendritic cell precursors. Despite advances in our understanding of tumor cell surface markers, the pathogenesis of BPDCN remains largely unknown. No standard or optimal treatments are available for BPDCN, and the prognosis is usually poor. We report herein a case of BPDCN that harbored multiple genetic mutations in epigenetic modifiers such as TET2 and ZRSR2. Genetic studies in patients with BPDCN may provide insights into the underlying pathogenesis, prediction of clinical prognosis, and development of better targeted therapeutics for this rare clinical entity.

A Case Series of Blastic Plasmacytoid Dendritic Cell Neoplasia

Blastic plasmacytoid dendritic cell neoplasm (BPDCN), an extremely rare and aggressive tumor, derives from plasmacytoid dendritic cell precursors and is characterized by CD4 and CD56 positivity accompanied by the expression of isolated myeloid, B- or T-cell lineage markers. Despite the recent introduction of specific targeted therapies, prognosis is still poor with a median overall survival of one year, and allogeneic bone marrow transplantation remains the only curative treatment in eligible patients. In this series, we described two cases of adult BPDCN treated with high dose cytarabine and methotrexate and autologous hematopoietic stem cell transplantation, or fludarabine, cytarabine, and idarubicin achieving the first a complete lasting remission, while the second only a transient improvement in skin lesions.

Tagraxofusp and anti-CD123 in blastic plasmacytoid dendritic cell neoplasm: a new hope

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematological malignancy, characterized by poor prognosis if treated with conventional therapy. Allogenic hematologic stem cell transplant can improve survival and can be curative, but it is available in a small percentage of patients given that the median age at diagnosis is 70 years. In this scenario it is assumed that only the development of precision medicine-driven therapy will change BPDCN patient prognosis. CD123 (the α-subunit of interleukin (IL)-3 receptor) is over-expressed on BPDCN cells surface and seems to be the ideal marker to develop antibody-based therapies. Tagraxofusp (Elzonris^®), a recombinant immunotoxin consisting of human interleukin-3 fused to a truncated diphtheria toxin, has been approved by FDA in December 2018 for the treatment of BPDCN in adult and pediatric patients. tagraxofusp has shown promising clinical activity, with a high overall response rate and quite manageable safety profile even in elderly patients. It seems to improve overall survival too, but comparative trials are necessary to confirm this. Adverse events are commonly reported and the most important are transaminitis, thrombocytopenia and capillary leak syndrome (CLS). Therefore, to prevent the onset of severe CLS is recommended to reserve tagraxofusp for patients with preserved hepatic and cardiac functions, and to strictly observe serum albumin level. Further studies are required to resolve many several unanswered questions about tagraxofusp. In this review, we will resume and discuss pharmacological characteristic of tagraxofusp, results of clinical trials leading to its approval by FDA in 2018 and future perspectives about its use in BPDCN and other hematological malignancies.

How should we diagnose and treat blastic plasmacytoid dendritic cell neoplasm patients?

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and aggressive leukemia for which we developed a nationwide network to collect data from new cases diagnosed in France. In a retrospective, observational study of 86 patients (2000-2013), we described clinical and biological data focusing on morphologies and immunophenotype. We found expression of markers associated with plasmacytoid dendritic cell origin (HLA-DRhigh, CD303+, CD304+, and cTCL1+) plus CD4 and CD56 and frequent expression of isolated markers from the myeloid, B-, and T-lymphoid lineages, whereas specific markers (myeloperoxidase, CD14, cCD3, CD19, and cCD22) were not expressed. Fifty-one percent of cytogenetic abnormalities impact chromosomes 13, 12, 9, and 15. Myelemia was associated with an adverse prognosis. We categorized chemotherapeutic regimens into 5 groups: acute myeloid leukemia (AML)-like, acute lymphoid leukemia (ALL)-like, lymphoma (cyclophosphamide, doxorubicin, vincristine, and prednisone [CHOP])-like, high-dose methotrexate with asparaginase (Aspa-MTX) chemotherapies, and not otherwise specified (NOS) treatments. Thirty patients received allogeneic hematopoietic cell transplantation (allo-HCT), and 4 patients received autologous hematopoietic cell transplantation. There was no difference in survival between patients receiving AML-like, ALL-like, or Aspa-MTX regimens; survival was longer in patients who received AML-like, ALL-like, or Aspa-MTX regimens than in those who received CHOP-like regimens or NOS. Eleven patients are in persistent complete remission after allo-HCT with a median survival of 49 months vs 8 for other patients. Our series confirms a high response rate with a lower toxicity profile with the Aspa-MTX regimen, offering the best chance of access to hematopoietic cell transplantation and a possible cure.

Approval of tagraxofusp-erzs for blastic plasmacytoid dendritic cell neoplasm

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and clinically challenging hematologic malignancy with dismal outcomes. With a median age of ∼70 years, the majority of patients with BPDCN have experienced historically suboptimal responses with intensive chemotherapy regimens. The major scientific breakthrough in this field was the recognition of overexpression of a surface receptor, CD123/interleukin 3 (IL-3) receptor α, in all patients. Importantly, a novel therapeutic agent consisting of a truncated diphtheria toxin (DT) payload fused to recombinant human IL-3 was being developed, one that targeted CD123, initially known as DT-IL-3 (later known as SL401; tagraxofusp; tagraxofusp-erzs [Elzonris]). The identification of this agent, and subsequent clinical trials specifically dedicated to patients with BPDCN (including a pilot study, followed by a larger phase 1/2 multicenter study [90% overall response rate [ORR] in frontline and 67% ORR in relapsed/refractory setting]), in part led to approval of tagraxofusp-erzs on 21 December 2018. Tagraxofusp-erzs was the first agent approved for BPDCN (for patients ages 2 years and older), and importantly, established this drug as the first CD123-targeted agent ever approved. The most notable toxicity of tagraxofusp-erzs is occurrence of the capillary leak syndrome, which occurs frequently at all grades, and has also been observed to be life-threatening, appropriately leading to a US Food and Drug Administration "black box" warning in the package insert. The preclinical and clinical aspects of drug development of tagraxofusp-erzs as monotherapy leading to drug approval are reviewed herein, with discussion of future directions of this novel agent, including consideration for rational combinations in BPDCN and beyond.

Updates in Novel Therapies for Blastic Plasmacytoid Dendritic Cell Neoplasm (BPDCN)

PURPOSE OF REVIEW

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare, clinically aggressive hematologic malignancy that has heterogeneous presentation and can involve the skin, lymph nodes, and bone marrow. Recent advancements in our patho-biologic understanding of the disease have led to the development of new targeted therapies for BPDCN. In this review, we aimed to describe some of the novel treatments that are being put forward for the management of BPDCN.

RECENT FINDINGS

Tagraxofusp is the first CD123-targeted therapy approved as the first ever targeted treatment of BPDCN in patients aged 2 years and older. This agent was approved based on a pivotal clinical trial that showed that it was associated with high rates of clinical responses in both treatment-naïve and treatment-experienced patients. The most serious adverse event was occurrence of the capillary leak syndrome. Other targeted therapies are actively being investigated in clinical trials. These include other CD123-targeted approaches, as well as active investigation in targets beyond CD123, such as the BCL-2 inhibitor, venetoclax. BPDCN is a rare hematologic clonal disorder with historically poor outcomes. Newer targeted therapies have been recently introduced, with promising results and novel toxicities that are important to recognize and understand. Stem cell transplantation after achievement of complete remission remains the mainstay of therapy among younger/fit, eligible patients, regardless of treatment modality used.

Blastic Plasmacytoid Dendritic Cell Neoplasm: Single Center Experience on a Rare Hematological Malignancy

Purpose

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and poor prognostic hematological malignancy. There is still no standard treatment established for BPDCN patients. We aim to summarize the main clinical, biological features and treatment of 9 BPDCN patients.

Methods

Nine patients with BPDCN who had been diagnosed between July 2008 and December 2018 in Ankara University School of Medicine, were retrospectively evaluated.

Results

All patients (n = 9) were male, median age was 64 (21-80). Five patients (55.6%) had bone marrow infiltration, 5 patients (55.6%) cutaneous lesions, 6 patients (66.7%) lymph node involvement, 2 patients (22.2%) central nervous system involvement and 2 patients (22.2%) spleen involvement at time of diagnosis. Complex karyotype was observed in 2 patients. CHOP was given to 5 patients (55.6%), hyper-CVAD to 2 patients (22.2%), fludarabine, cyclophosphamide and mitoxantrone to 1 patient (11.1%) and cyclophosphamide, etoposide, methylprednisolone to 1 patient (11.1%) as first line chemotherapy. Four patients (44.4%) underwent allogeneic hematopoietic stem cell transplantation (AHSCT) in complete remission (CR) 1. Venetoclax was given to a transplant ineligible patient who had skin and lymph node involvement, with the off-label use. The median follow-up time was 15.9 months (3-48.6 months). Estimated median overall survival was 15.9 + 1.6 (95% CI 12.7-19.1) months.

Conclusion

Intensive induction therapies followed by AHSCT in CR seems to be best approaches for patients with BPDCN. Thus, more effective treatment strategies particularly targeted therapies should be warranted to improve the survival of patients with this rare disease.

Tagraxofusp as treatment for patients with blastic plasmacytoid dendritic cell neoplasm

INTRODUCTION

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare, aggressive hematologic malignancy that previously lacked standardized therapeutic approaches. CD123 (interleukin-3 receptor alpha unit) is highly expressed in many hematologic malignancies, including BPDCN. Tagraxofusp-ezrs (tagraxofusp from herein) is an agent that consists of interleukin-3 fused to a truncated diphtheria toxin, targeting CD123. The Food and Drug Administration recently approved tagraxofusp as therapy for BPDCN for adults and children aged 2 years and older.

AREAS COVERED

We discuss the history and clinical background of BPDCN along with tagraxofusp as its first-line therapy. We review the clinical efficacy and safety profile of tagraxofusp in adults including proposed sensitivity and resistance. Finally, we summarize tagraxofusp use in the pediatric population.

EXPERT OPINION

Tagraxofusp is a newly approved therapy for BPDCN, a hematologic malignancy that has overall historically poor outcomes. With its significant efficacy, many patients were successfully bridged to stem cell transplantation in the clinical trial leading to its ultimate approval. Clinical awareness for major toxicities, including capillary leak syndrome will be a critical aspect of using this novel agent. In the future, investigation of its use in other hematologic malignancies and expansion of clinical trials in pediatric populations with BPDCN are warranted.

Blastic plasmacytoid dendritic cell neoplasm: diagnosis, manifestations, and treatment

PURPOSE OF REVIEW

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and aggressive hematologic malignancy with historically poor outcomes. It typically manifests as asymptomatic skin lesions and cytopenias, which result from bone marrow involvement. Less commonly, it will present in lymph nodes or visceral organs as well. Although rare, BPDCN has been discussed more frequently in recent years as new drugs have been developed that could be effective at treating this disease.

RECENT FINDINGS

Until recently, treatment for BPDCN commonly included intensive chemotherapy regimens, which are generally reserved for management of acute myeloid leukemia or acute lymphoblastic leukemia. However, in 2018 tagraxofusp (SL-401) was approved as the only treatment specifically indicated for BPDCN. Additional clinical trials are ongoing evaluating the efficacy of newer agents, which could potentially further improve the long-term outcomes for patients with BPDCN.

SUMMARY

This manuscript reviews the diagnosis, manifestations and treatment of BPDCN.

Dendritic Cell Leukemia: a Review

PURPOSE OF REVIEW

The purpose of this review was to summarize the clinical, diagnostic, and therapeutic features of blastic plasmacytoid dendritic cell neoplasm (BPDCN).

RECENT FINDINGS

Several case reports and series revealed new clinical, molecular, diagnostic, and therapeutic aspects of the disease. The clinical presentation diversity has been confirmed, with frequent leukemic non-cutaneous or rare atypical manifestations. The clonal evolution in the development of BPDCN has not been sufficiently elucidated. Although certain immunophenotypic markers (CD4, TCL1, CD123, CD56, CD303) are indicative of BPDCN, the diagnosis remains in certain cases challenging. Adult (ALL)-type chemotherapy followed by hematopoietic stem cell transplantation (HSCT) is related to a favorable outcome, while chemotherapy alone seems enough in children. Future studies should continue to investigate whether CD123-directed therapies could be utilized. BPDCN is a rare aggressive malignancy that needs an aggressive induction therapy. Although a diagnostic consensus is still lacking, and large retrospective studies are also needed to obtain standardized treatment guidelines, the future perspectives are encouraging, because of novel therapeutic agents that are under investigation.

Immune cell diversity contributes to the pathogenesis of myocarditis

Myocarditis (MCD) is a type of inflammatory disease in which inflammatory cells infiltrate the myocardium, leading to cardiac dysfunction, myocardial necrosis, and fibrosis. Although it has been reported that MCD is mediated by T cells, the immune system is complex and includes many types of immune cells that interact with one another. Through investigations of the inflammatory responses in MCD including myocardial necrosis, fibrosis, and arrhythmia, we have gained further insight into the pathogenesis of MCD. This article aims to discuss the diversity and the roles of immune cells involved in the pathogenesis of MCD. Moreover, immunotherapy for the treatment of MCD remains controversial, and further investigation is required to identify accurate immunotherapies for special cell types.

Chemotherapy Options for Blastic Plasmacytoid Dendritic Cell Neoplasm

BPDCN is ultimately a bone marrow disease requiring induction-type eradication therapy followed by hematopoietic stem cell transplant (HSCT) to achieve long-lasting remissions or cure. Various regimens have been applied to this disease with varying success. A cumulative review of the literature suggests more intense regimens have greater efficacy with acute lymphoblastic leukemia regimens preferred to acute myeloid leukemia regimens. This approach benefits fit patients who are eligible for HSCT; however, most BPDCN patients require other treatment options. The recent FDA approval of the CD123-targeted agent tagraxofusp provides a novel therapeutic alternative to traditional chemotherapy but with potential toxicities.

Blastic Plasmacytoid Dendritic Cell Neoplasm in Children

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare, aggressive hematological malignancy, derived from plasmacytoid dendritic cells. It mainly occurs in older adults, but has been reported across all age groups. Most patients present with skin lesions with or without marrow involvement and leukemic dissemination. Treatment with high-risk acute lymphoblastic leukemia therapy regimens with central nervous system prophylaxis is recommended in pediatric patients. Stem cell transplant in children is recommended for relapsed/refractory disease or high-risk disease at presentation. New targeted therapies including the recently FDA-approved anti-CD123 cytotoxin show great promise in improving the response rate.

Molecular Features of Blastic Plasmacytoid Dendritic Cell Neoplasm: DNA Mutations and Epigenetics

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematologic neoplasm with a dismal prognosis and no standard therapy. In the past, its cellular ontogenesis was obscure, and BPDCN had been erroneously named CD56⁺/TdT⁺ blastic NK cell tumor and CD4⁺/CD56⁺ hematodermic neoplasm. Finally, in 2008, the BPDCN was correctly recognized as a neoplasm deriving from the malignant transformation of plasmacytoid dendritic cell precursors and classified among the myeloid neoplasms. Since then, the understanding of BPDCN biology has improved rapidly: the DNA mutational status of BPDCN has been extensively investigated revealing a spectrum perfectly resembling its myeloid lineage derivation.

New perspectives in genetics and targeted therapy for blastic plasmacytoid dendritic cell neoplasm

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is one rare but clinically aggressive hematological malignancy, and it is typically characterized by skin lesion and bone marrow involvement. Diagnosis of BPDCN relies on the immunophenotype positive for four of CD4, CD56, CD123, TCL1 and BDCA-2, and commonly without the expression of MPO, cytoplasmic CD3, CD13, CD64, cytoplasmic CD79a, CD19 and CD20. Commonly, BPDCN is characterized by high CD123 expression, aberrant NF-κB activation, dependence on TCF4-/BRD4-network, and deregulated cholesterol metabolism. Under conventional therapy, the survival duration is only improved in a small number of BPDCN patients. Therefore, targeted therapy should be developed. Up to now, tagraxofusp is the leading edge and has been approved for BPDCN treatment. However, most of other targeted therapy agents were still not pushed to clinical trials for BPDCN. In this review, we emphatically discuss recent perspectives on BPDCN genetic features and developments of its targeted therapy.

Whole-genome analysis uncovers recurrent IKZF1 inactivation and aberrant cell adhesion in blastic plasmacytoid dendritic cell neoplasm

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and highly aggressive hematological malignancy with a poorly understood pathobiology and no effective therapeutic options. Despite a few recurrent genetic defects (eg, single nucleotide changes, indels, large chromosomal aberrations) have been identified in BPDCN, none are disease‐specific, and more importantly, none explain its genesis or clinical behavior. In this study, we performed the first high resolution whole‐genome analysis of BPDCN with a special focus on structural genomic alterations by using whole‐genome sequencing and RNA sequencing. Our study, the first to characterize the landscape of genomic rearrangements and copy number alterations of BPDCN at nucleotide‐level resolution, revealed that IKZF1, a gene encoding a transcription factor required for the differentiation of plasmacytoid dendritic cell precursors, is focally inactivated through recurrent structural alterations in this neoplasm. In concordance with the genomic data, transcriptome analysis revealed that conserved IKZF1 target genes display a loss‐of‐IKZF1 expression pattern. Furthermore, up‐regulation of cellular processes responsible for cell‐cell and cell‐ECM interactions, which is a hallmark of IKZF1 deficiency, was prominent in BPDCN. Our findings suggest that IKZF1 inactivation plays a central role in the pathobiology of the disease, and consequently, therapeutic approaches directed at reestablishing the function of this gene might be beneficial for patients.

Role of tagraxofusp in treating blastic plasmacytoid dendritic cell neoplasm (BPDCN)

Introduction: Advances and drug development in rare diseases, such as blastic plasmacytoid dendritic cell neoplasm (BPDCN), has historically been limited by small numbers of patients in the target population. In recent years, the development of tagraxofusp (SL-401) (ELZONRIS, Stemline Therapeutics) for the treatment of adult and pediatric BPDCN has been a successful story that led to US FDA approval in December 2018.Areas covered: In this evaluation of tagraxofusp, we briefly review chemistry; pharmacokinetics and pharmacodynamics, as we focus on the clinical experience and future directions.Expert Opinion: Tagraxofusp has been a welcome new addition and a successful initial development step in the targeted treatment of BPDCN. In phase I/II clinical trial, major responses were observed in 90% of treatment-naïve patients, with 72% of the responses observed as complete remissions. Limitations on the usage of tagraxofusp and strategies to handle those limitations were further explored in this review.

Features of non-activation dendritic state and immune deficiency in blastic plasmacytoid dendritic cell neoplasm (BPDCN)

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare, male-predominant hematologic malignancy with poor outcomes and with just one recently approved agent (tagraxofusp). It is characterized by the abnormal proliferation of precursor plasmacytoid dendritic cells (pDCs) with morphologic and molecular similarities to acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS)/chronic myelomonocytic leukemia (CMML) in its presentation within the bone marrow and peripheral blood. To identify disease-specific molecular features of BPDCN, we profiled the bone marrow, peripheral blood, and serum samples from primary patient samples using an in-house hematologic malignancy panel ("T300" panel), transcriptome microarray, and serum multiplex immunoassays. TET2 mutations (5/8, 63%) were the most prevalent in our cohort. Using the transcriptome microarray, genes specific to pDCs (LAMP5, CCDC50) were more highly expressed in BPDCN than in AML specimens. Finally, the serum cytokine profile analysis showed significantly elevated levels of eosinophil chemoattractants eotaxin and RANTES in BPDCN as compared with AML. Along with the high levels of PTPRS and dendritic nature of the tumor cells, these findings suggest a possible pre-inflammatory context of this disease, in which BPDCN features nonactivated pDCs.

Recent developments in the treatment of blastic plasmacytoid dendritic cell neoplasm

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a clinically aggressive hematologic malignancy derived from precursors of dendritic cells and involves most frequently the skin, bone marrow and lymph nodes. Diagnosis depends upon identification of specific tumor markers including CD4, CD56 and CD123. Historically, the median survival has been less than 2 years in most reported series. While for many years, conventional chemotherapy followed by stem cell transplantation was the standard of care, recently tagraxofusp, a cytotoxin directed against CD123, received United States Food and Drug Administration approval specifically for patients with BPDCN. In this review, we will discuss the markers used for diagnosis of BPDCN and focus on the new targeted treatments available. Specifically in BPDCN, tagraxofusp was highly effective with a safety profile found to be acceptable overall, with the noted occurrence of capillary leak syndrome. Future directions in therapy approaches for patients with BPDCN will include the development of other CD123-targeted agents, agents targeting beyond CD123 and investigation of rational combination approaches of CD123-directed therapy with other therapies.

Transcriptional Analysis of Lennert Lymphoma Reveals a Unique Profile and Identifies Novel Therapeutic Targets

Lennert lymphoma (LL) is a lymphoepithelioid morphological variant of peripheral T-cell lymphoma-not otherwise specified (PTCL/NOS), clinically characterized by better prognosis if compared with other PTCL/NOS. Although well characterized as far as morphology and phenotype are concerned, very little is known regarding its molecular features. In this study, we investigated the transcriptional profile of this tumor aiming 1) to identify its cellular counterparts; 2) to better define its relation with other PTCLs-and, therefore, its possible position in lymphoma classification; and 3) to define pathogenetic mechanisms, possibly unveiling novel therapeutic targets. To address these issues, we performed gene and microRNA expression profiling on LL and other PTCL/NOS cases; we identified different genes and microRNAs that discriminated LL from other PTCL/NOS. Particularly, LL revealed a molecular signature significantly enriched in helper function and clearly distinguishable from other PTCL/NOS. Furthermore, PI3K/Akt/mTOR pathway emerged as novel potential therapeutic target. In conclusion, based on the already known particular morphological and clinical features, the new molecular findings support the hypothesis that LL might be classified as a separate entity. Preclinical and clinical studies testing the efficacy of PI3K/MTOR inhibitors in this setting are warranted.

Targeting BCL2 in Chronic Lymphocytic Leukemia and Other Hematologic Malignancies

Apoptosis, the process of programmed cell death, occurs normally during development and aging. Members of the B-cell lymphoma 2 (BCL2) family of proteins are central regulators of apoptosis, and resistance to apoptosis is one of the hallmarks of cancer. Targeting the apoptotic pathway via BCL2 inhibitors has been considered a promising treatment strategy in the past decade. Initial efforts with small molecule BH3 mimetics such as ABT-737 and ABT-263 (navitoclax) pioneered the development of the first-in-class Food and Drug Administration (FDA)-approved oral BCL2 inhibitor, venetoclax. Venetoclax was approved for the treatment of chronic lymphocytic leukemia and acute myeloid leukemia, and is now being studied in a number of hematologic malignancies. Several other inhibitors targeting different BCL2 family members are now in early stages of development.

Multicenter analysis of outcomes in blastic plasmacytoid dendritic cell neoplasm offers a pretargeted therapy benchmark

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an uncommon hematologic malignancy with poor outcomes. Existing data on the clinical behavior of BPDCN are limited because reported outcomes are from small retrospective series, and standardized treatment guidelines are lacking. The interleukin-3 cytotoxin conjugate tagraxofusp was recently tested in phase 1/2 trials that led to US Food and Drug Administration approval, the first ever for BPDCN. However, because there was no matched internal comparator in this or any clinical study to date, results of BPDCN trials testing new drugs are difficult to compare with alternative therapies. We therefore sought to define the clinical characteristics and outcomes of a group of patients with BPDCN treated at 3 US cancer centers in the modern era but before tagraxofusp was available. In 59 studied patients with BPDCN, the median overall survival from diagnosis was 24 months, and outcomes were similar in patients with "skin only" or with systemic disease at presentation. Intensive first-line therapy and "lymphoid-type" chemotherapy regimens were associated with better outcomes. Only 55% of patients received intensive chemotherapy, and 42% of patients underwent stem cell transplantation. Clinical characteristics at diagnosis associated with poorer outcomes included age >60 years, abnormal karyotype, and terminal deoxynucleotidyltransferase (TdT) negativity in the BPDCN cells. We also identified disease responses to pralatrexate and enasidenib in some patients. This study highlights poor outcomes for patients with BPDCN in the modern era and the need for new treatments. Outcomes from ongoing clinical trials for BPDCN can be evaluated relative to this contemporary cohort.

Blastic Plasmacytoid Dendritic Cell Neoplasm: State of the Art and Prospects

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an extremely rare tumour, which usually affects elderly males and presents in the skin with frequent involvement of the bone-marrow, peripheral blood and lymph nodes. It has a dismal prognosis, with most patients dying within one year when treated by conventional chemotherapies. The diagnosis is challenging, since neoplastic cells can resemble lymphoblasts or small immunoblasts, and require the use of a large panel of antibodies, including those against CD4, CD56, CD123, CD303, TCL1, and TCF4. The morphologic and in part phenotypic ambiguity explains the uncertainties as to the histogenesis of the neoplasm that led to the use of various denominations. Recently, a series of molecular studies based on karyotyping, gene expression profiling, and next generation sequencing, have largely unveiled the pathobiology of the tumour and proposed the potentially beneficial use of new drugs. The latter include SL-401, anti-CD123 immunotherapies, venetoclax, BET-inhibitors, and demethylating agents. The epidemiologic, clinical, diagnostic, molecular, and therapeutic features of BPDCN are thoroughly revised in order to contribute to an up-to-date approach to this tumour that has remained an orphan disease for too long.

Lineage-specific RUNX2 super-enhancer activates MYC and promotes the development of blastic plasmacytoid dendritic cell neoplasm

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an aggressive subtype of acute leukemia, the cell of origin of which is considered to be precursors of plasmacytoid dendritic cells (pDCs). Since translocation (6;8)(p21;q24) is a recurrent anomaly for BPDCN, we demonstrate that a pDC-specific super-enhancer of RUNX2 is associated with the MYC promoter due to t(6;8). RUNX2 ensures the expression of pDC-signature genes in leukemic cells, but also confers survival and proliferative properties in BPDCN cells. Furthermore, the pDC-specific RUNX2 super-enhancer is hijacked to activate MYC in addition to RUNX2 expression, thereby promoting the proliferation of BPDCN. We also demonstrate that the transduction of MYC and RUNX2 is sufficient to initiate the transformation of BPDCN in mice lacking Tet2 and Tp53, providing a model that accurately recapitulates the aggressive human disease and gives an insight into the molecular mechanisms underlying the pathogenesis of BPDCN.

Therapeutic Approaches for Blastic Plasmacytoid Dendritic Cell Neoplasm: Allogeneic Hematopoietic Cell Transplantation and Novel Therapies

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a clinically aggressive hematologic malignancy derived from precursors of plasmacytoid dendritic cells. There is no established standard therapy for BPDCN and the efficacy of conventional chemotherapy is limited, with an anticipated median overall survival ranging from 8 to 14 months. No randomized controlled trials have ever been performed to evaluate the benefit of frontline consolidation with an allogeneic hematopoietic cell transplant (allo-HCT) in BPDCN. Yet, offering an allograft has become the de facto option in BPDCN, and remains the only known long-term curative option for these patients, even in the modern era of targeted therapies. In our opinion, allo-HCT is recommended as part of frontline consolidation, especially in patients achieving first complete remission and who are deemed capable of tolerating the procedure, as published data show 3- to 4-year progression-free survival ranging from 69% to 74% in this population. Prompt referral to a transplant center, at the time of a diagnosis of BPDCN, is important to confirm allo-HCT candidacy and to initiate the process of identifying a suitable human leukocyte antigen (HLA)-compatible donor. Because disease relapse remains a major concern, additional strategies, such as post-allograft consolidation/maintenance therapy, are certainly needed to help further improve outcomes. Finally, patients deemed ineligible to receive an allo-HCT, due to lack of response and/or poor performance status, should be considered for enrollment in clinical trials.

[Clinical characteristics of 6 patients with blastic plasmacytoid dendritic cell neoplasm]

目的

探讨母细胞性浆细胞样树突细胞肿瘤（BPDCN）的临床特征、治疗和预后。

方法

回顾性分析2008年1月至2016年5月北京协和医院确诊的6例BPDCN患者的临床资料。

结果

6例患者起病时均有皮肤受累，常见表现包括骨髓受累（5例）、淋巴结肿大（4例）、脾大（4例）和肝大（3例）。皮肤外的结外器官受累包括乳腺、上颌窦、椎体和中枢神经系统各1例。肿瘤细胞特征性的免疫表型CD4、CD56、CD123均为阳性。治疗均采用急性淋巴细胞白血病样方案，4例达到完全缓解。中位随访9.5（7~37）个月，中位无进展生存期7个月，中位总生存期9个月。死亡3例，均在诊断后1年内死于原发病复发或进展。

结论

BPDCN侵袭性强，常以皮肤受累为首发症状，骨髓受累、淋巴结和肝脾大较为常见；特征性免疫标志包括CD4、CD56和CD123；目前缺乏有效、标准的治疗方案，预后不良。

Blastic plasmacytoid dendritic cell neoplasm: genomics mark epigenetic dysregulation as a primary therapeutic target

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and aggressive hematologic malignancy for which there is still no effective therapy. In order to identify genetic alterations useful for a new treatment design, we used whole-exome sequencing to analyze 14 BPDCN patients and the patient-derived CAL-1 cell line. The functional enrichment analysis of mutational data reported the epigenetic regulatory program to be the most significantly undermined (P<0.0001). In particular, twenty-five epigenetic modifiers were found mutated (e.g. ASXL1, TET2, SUZ12, ARID1A, PHF2, CHD8); ASXL1 was the most frequently affected (28.6% of cases). To evaluate the impact of the identified epigenetic mutations at the gene-expression and Histone H3 lysine 27 trimethylation/acetylation levels, we performed additional RNA and pathology tissue-chromatin immunoprecipitation sequencing experiments. The patients displayed enrichment in gene signatures regulated by methylation and modifiable by decitabine administration, shared common H3K27-acetylated regions, and had a set of cell-cycle genes aberrantly up-regulated and marked by promoter acetylation. Collectively, the integration of sequencing data showed the potential of a therapy based on epigenetic agents. Through the adoption of a preclinical BPDCN mouse model, established by CAL-1 cell line xenografting, we demonstrated the efficacy of the combination of the epigenetic drugs 5’-azacytidine and decitabine in controlling disease progression in vivo.

An analysis of blastic plasmacytoid dendritic cell neoplasm with translocations involving the MYC locus identifies t(6;8)(p21;q24) as a recurrent cytogenetic abnormality

AIMS

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an aggressive neoplasm with leukaemic features and frequent skin involvement. Translocations involving the MYC locus have been recently identified as recurrent cytogenetic abnormalities in this entity. The aim of this study was to assess the clinicopathological, immunophenotypic and genetic features in MYC-rearranged BPDCN cases.

METHODS AND RESULTS

Pathology archives from six major institutes were queried for cases of BPDCN with 8q24 MYC translocations, and two cases were identified. A literature review identified 14 cases. Clinicopathological features, immunophenotype and cytogenetic and molecular data were reviewed. In these 16 MYC-rearranged cases, the median age at diagnosis was 70.5 years, and there was a male predominance. Whereas all cases showed marrow involvement, skin lesions (62.5%) and lymphadenopathy (50%) were variably seen. The median survival was 11 months. The median percentage of blasts in peripheral blood was 9%. All cases showed expression of CD4, with 10 of 16 being positive for CD56. HLA-DR, CD123, TCL1 and CD303 were positive in all cases tested. Cytogenetic analysis revealed a single recurrent translocation partner of MYC at 6p21 in 11 cases (69%), whereas four cases showed different MYC translocation partners (2p12, Xq24, 3p25, and 14q32). Interestingly, the group of patients with t(6;8)(p21;q24) showed an older median age at diagnosis (74 years) and a remarkably shorter median survival (3 months).

CONCLUSIONS

Translocations involving the 8q24 MYC locus more frequently manifest as t(6;8)(p21;q24), and, given its association with specific clinicopathological features suggesting even more aggressive behaviour, t(6;8)(p21;q24) indicate a genetically defined subgroup within BPDCN.

Analysis of First-Year Twitter Metrics of a Rare Disease Community for Blastic Plasmacytoid Dendritic Cell Neoplasm (BPDCN) on Social Media: #BPDCN

PURPOSE OF REVIEW

The use of Twitter, one of the most commonly engaged social media platforms in the world, is increasing among the general public. Notably, this trend has also been observed among those involved in the healthcare field. With its ability to readily connect diverse groups of stakeholders in a given area of interest, Twitter has become a focal point for those involved in increasing awareness and information exchange in orphan disease fields. Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare, aggressive hematologic malignancy with generally poor long-term outcomes for adult patients and no standard therapeutic guidelines. Coupled with its low incidence rate, the disease has experienced a number of name changes over the past three decades (e.g., blastic NK cell lymphoma, CD4+CD56+ hematodermic tumor), thereby historically resulting in difficulties in its clinico-pathologic diagnosis and treatment approaches. All of these factors have led to a striking gap in terms of accurate information available to patients and the general public. Therefore, there is an urgent need for the development of more venues for the dissemination of information, particularly online, for this rare cancer.

RECENT FINDINGS

In this context, we began the Twitter medical community, #BPDCN, over a year ago, to help fill this information void. Now, completing its first year of existence, we aimed to analyze the metrics of Twitter use in order to better understand and to describe the characteristics and reach in of #BPDCN, and to determine the feasibility of starting and maintaining a disease-specific hashtag community in a particularly rare cancer.

Recurrent 8q24 rearrangement in blastic plasmacytoid dendritic cell neoplasm: association with immunoblastoid cytomorphology, MYC expression, and drug response

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare skin-tropic hematological malignancy of uncertain pathogenesis and poor prognosis. We examined 118 BPDCN cases for cytomorphology, MYC locus rearrangement, and MYC expression. Sixty-two (53%) and 41 (35%) cases showed the classic and immunoblastoid cytomorphology, respectively. Forty-one (38%) MYC⁺BPDCN (positive for rearrangement and expression) and 59 (54%) MYC^-BPDCN (both negative) cases were identified. Immunoblastoid cytomorphology was significantly associated with MYC⁺BPDCN. All examined MYC⁺BPDCNs were negative for MYB/MYBL1 rearrangement (0/36). Clinically, MYC⁺BPDCN showed older onset, poorer outcome, and localized skin tumors more commonly than MYC^-BPDCN. MYC was demonstrated by expression profiling as one of the clearest discriminators between CAL-1 (MYC⁺BPDCN) and PMDC05 (MYC^-BPDCN) cell lines, and its shRNA knockdown suppressed CAL-1 viability. Inhibitors for bromodomain and extra-terminal protein (BETis), and aurora kinases (AKis) inhibited CAL-1 growth more effectively than PMDC05. We further showed that a BCL2 inhibitor was effective in both CAL-1 and PMDC05, indicating that this inhibitor can be used to treat MYC^-BPDCN, to which BETis and AKis are probably less effective. Our data will provide a rationale for the development of new treatment strategies for patients with BPDCN, in accordance with precision medicine.

Cutaneous presentation preceding acute myeloid leukemia with CD4+/CD56+ expression misdiagnosed as a blastic plasmocytoid dendritic cell neoplasm: A case report

Acute myeloid leukemia (AML) may initially present as cutaneous lesions corresponding to blasts involving the skin as the first clinical manifestation prior to blood and bone marrow (BM) infiltration. Such presentation is known as myeloid leukemia cutis (LC). Blastic plasmocytoid dendritic cell neoplasm (BPDCN) is an aggressive tumor derived from the precursors of plasmocytoid dendritic cells with cutaneous and BM involvement and leukemic dissemination. Myeloid LC and BPDCN may be difficult to distinguish as they share similar clinical and histopathological features, in particular AML with monocytic differentiation. Nevertheless, the correct diagnosis has to be made to determine adequate and effective therapy. Here, we report the case of a 61-year-old woman who presented with an AML with MLL rearrangement and CD4+/CD56+ expression presenting as LC and that was misdiagnosed as BPDCN. We emphasize that careful and exhaustive analyses should be performed to make the correct diagnosis.