Blastic Plasmacytoid Dendritic Cell Neoplasm Patients Research Articles

Genome-wide DNA methylation-analysis of blastic plasmacytoid dendritic cell neoplasm identifies distinct molecular features

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) constitutes a rare and aggressive malignancy originating from plasmacytoid dendritic cells (pDCs) with a primarily cutaneous tropism followed by dissemination to the bone marrow and other organs. We conducted a genome-wide analysis of the tumor methylome in an extended cohort of 45 BPDCN patients supplemented by WES and RNA-seq as well as ATAC-seq on selected cases. We determined the BPDCN DNA methylation profile and observed a dramatic loss of DNA methylation during malignant transformation from early and mature DCs towards BPDCN. DNA methylation profiles further differentiate between BPDCN, AML, CMML, and T-ALL exhibiting the most striking global demethylation, mitotic stress, and merely localized DNA hypermethylation in BPDCN resulting in pronounced inactivation of tumor suppressor genes by comparison. DNA methylation-based analysis of the tumor microenvironment by MethylCIBERSORT yielded two, prognostically relevant clusters (IC1 and IC2) with specific cellular composition and mutational spectra. Further, the transcriptional subgroups of BPDCN (C1 and C2) differ by DNA methylation signatures in interleukin/inflammatory signaling genes but also by higher transcription factor activity of JAK-STAT and NFkB signaling in C2 in contrast to an EZH2 dependence in C1-BPDCN. Our integrative characterization of BPDCN offers novel molecular insights and potential diagnostic applications.

Transcriptional Landscape of CUT-Class Homeobox Genes in Blastic Plasmacytoid Dendritic Cell Neoplasm.

Homeobox genes encode developmental transcription factors regulating tissue-specific differentiation processes and drive cancerogenesis when deregulated. Dendritic cells (DCs) are myeloid immune cells occurring as two types, either conventional or plasmacytoid DCs. Recently, we showed that the expression of NKL-subclass homeobox gene VENTX is restricted to conventional DCs, regulating developmental genes. Here, we identified and investigated homeobox genes specifically expressed in plasmacytoid DCs (pDCs) and derived blastic plasmacytoid dendritic cell neoplasm (BPDCN). We analyzed gene expression data, performed RQ-PCR, protein analyses by Western blot and immuno-cytology, siRNA-mediated knockdown assays and subsequent RNA-sequencing and live-cell imaging. Screening of public gene expression data revealed restricted activity of the CUT-class homeobox gene CUX2 in pDCs. An extended analysis of this homeobox gene class in myelopoiesis showed that additional CUX2 activity was restricted to myeloid progenitors, while BPDCN patients aberrantly expressed ONECUT2, which remained silent in the complete myeloid compartment. ONECUT2 expressing BPDCN cell line CAL-1 served as a model to investigate its regulation and oncogenic activity. The ONECUT2 locus at 18q21 was duplicated and activated by IRF4, AUTS2 and TNF-signaling and repressed by BMP4-, TGFb- and IL13-signalling. Functional analyses of ONECUT2 revealed the inhibition of pDC differentiation and of CDKN1C and CASP1 expression, while SMAD3 and EPAS1 were activated. EPAS1 in turn enhanced survival under hypoxic conditions which thus may support dendritic tumor cells residing in hypoxic skin lesions. Collectively, we revealed physiological and aberrant activities of CUT-class homeobox genes in myelopoiesis including pDCs and in BPDCN, respectively. Our data may aid in the diagnosis of BPDCN patients and reveal novel therapeutic targets for this fatal malignancy.

Breakthrough in Blastic Plasmacytoid Dendritic Cell Neoplasm Cancer Therapy Owing to Precision Targeting of CD123.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and aggressive hematologic cancer originating from the malignant transformation of plasmacytoid dendritic cell precursors. This malignancy progresses rapidly, with frequent relapses and a poor overall survival rate, underscoring the urgent need for effective treatments. However, diagnosing and treating BPDCN have historically been challenging due to its rarity and the lack of standardized approaches. The recognition of BPDCN as a distinct disease entity is recent, and standardized treatment protocols are yet to be established. Traditionally, conventional chemotherapy and stem cell transplantation have been the primary methods for treating BPDCN patients. Advances in immunophenotyping and molecular profiling have identified potential therapeutic targets, leading to a shift toward CD123-targeted immunotherapies in both clinical and research settings. Ongoing developments with SL-401, IMGN632, CD123 chimeric antigen receptor (CAR) T-cells, and bispecific antibodies (BsAb) show promising advancements. However, the therapeutic effectiveness of CD123-targeting treatments needs improvement through innovative approaches and combinations of treatments with other anti-leukemic drugs. The exploration of combinations such as CD123-targeted immunotherapies with azacitidine and venetoclax is suggested to enhance antineoplastic responses and improve survival rates in BPDCN patients. In conclusion, this multifaceted approach offers hope for more effective and tailored therapeutic interventions against this challenging hematologic malignancy.

Diagnostic management of blastic plasmacytoid dendritic cell neoplasm (BPDCN) in close interaction with therapeutic considerations

Blastic plasmacytoid dendritic cell neoplasm (BPDCN), a rare malignancy derived from plasmacytoid dendritic cells, can mimic both acute leukemia and aggressive T-cell lymphoma. Therapy of this highly aggressive hematological disease should be initiated as soon as possible, especially in light of novel targeted therapies that have become available. However, differential diagnosis of BPDCN remains challenging. This retrospective study aimed to highlight the challenges to timely diagnoses of BPDCN. We documented the diagnostic and clinical features of 43 BPDCN patients diagnosed at five academic hospitals from 2001–2022. The frequency of BPDCN diagnosis compared to AML was 1:197 cases. The median interval from the first documented clinical manifestation to diagnosis of BPDCN was 3 months. Skin (65%) followed by bone marrow (51%) and blood (45%) involvement represented the most common sites. Immunophenotyping revealed CD4 + , CD45 + , CD56 + , CD123 + , HLA-DR + , and TCL-1 + as the most common surface markers. Overall, 86% (e.g. CD33) and 83% (e.g., CD7) showed co-expression of myeloid and T-cell markers, respectively. In the median, we detected five genomic alterations per case including mutational subtypes typically involved in AML: DNA methylation (70%), signal transduction (46%), splicing factors (38%), chromatin modification (32%), transcription factors (32%), and RAS pathway (30%), respectively. The contribution of patients (30%) proceeding to any form of upfront stem cell transplantation (SCT; autologous or allogeneic) was almost equal resulting in beneficial overall survival rates in those undergoing allogeneic SCT (p = 0.0001). BPDCN is a rare and challenging entity sharing various typical characteristics of other hematological diseases. Comprehensive diagnostics should be initiated timely to ensure appropriate treatment strategies.

A systematic literature review of 74 Chinese blastic plasmacytoid dendritic cell neoplasm patients.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and aggressive hematological cancer. Due to its low incidence, researchers struggle to gather sufficient prospective data to inform clinical treatment. We sought to summarize the clinical characteristics and current treatment methods of BPDCN and provide more specific guidance on treatment options. A systematic literature review using data from 74 Chinese BPDCN patients. We retrospectively analyzed the clinical manifestations, treatment response, survival outcomes, and prognostic factors of six BPDCN patients treated at the First Affiliated Hospital of Zhengzhou University and 68 patients described in 28 articles published in the China Knowledge Network database since 2019. In Chinese patients, the disease occurred with a male-to-female ratio of 2.52 and a median age of onset of 50 years in adults and 10 years in pediatric patients. Immunohistochemical analysis revealed distinctive immune phenotypes of BPDCN cells, characterized by high expression levels of CD4, CD56, CD123, and HLA-DR, while showing minimal to no expression of myeloperoxidase (MPO), CD20, and CD79a. There was no significant difference in the initial complete remission (CR) rate, relapse rate, and the overall survival (OS) time of patients receiving acute myeloid leukemia-like, acute lymphocytic leukemia-like, or non-Hodgkin's lymphoma-like chemotherapy regimens. Univariate analysis identified CD3 expression, male gender, and central nervous system infiltration as hazardous factors. In multivariate analysis, age proved to be an independent prognostic indicator, indicating better prognosis and longer OS time in younger patients. Notably, hematopoietic stem cell transplantation (HSCT) emerged as a significant factor in improving the survival outcomes for individuals diagnosed with BPDCN. However, further investigation is needed to explore the role of HSCT and the best timing for its implementation in pediatric BPDCN patients. Administering HSCT during the initial CR state following inductive chemotherapy might extend the OS and improve the prognosis of patients with BPDCN.

Heterogeneity and Differentiation Patterns of pDC Cells in pDC-AML: A Novel Perspective from Single-Cell RNA Sequencing

Background: Plasmacytoid dendritic cells (pDCs), being a primary source of natural type I interferon (IFN-I), have pivotal roles in orchestrating the immune response. Typically, only less than 1% pDCs can be detected in the total bone marrow or peripheral blood nuclear cells. However, the uncontrollable proliferation of transformed pDCs is a remarkable characteristic of blastic plasmacytoid dendritic cell neoplasm (BPDCN). Recently, an abnormal amplification of pDCs in myeloid neoplasms has also been reported in MDS/AML patients (pDC-AML/MDS). This abnormal increase in pDCs could potentially promote disease progression. In this study, we utilized single-cell RNA-sequencing (scRNA-seq) to examine the characteristics of pDCs in pDC-AML. Method: Our study employed a mixed retrospective and prospective design. 85 patients diagnosed with PDC-AML/MDS/BPDCN, including 1 pDC-MDS, 17 pDC-AML, 50 non-pDC-AML (AML patients without pDCs expansion), 17 BPDCN from Tongji Hospital of Huazhong University of Science and Technology in Wuhan, China, between July 2014 and June 2023. scRNA-seq using 10x Genomics platform were performed on bone marrow (BM) samples from 8 pDC-AML patients and 1 BPDCN patient. Furthermore, we expanded our dataset by integrating publicly available scRNA-seq data of BM samples from 5 BPDCN patients, 5 non-pDC-AML patients, and 5 healthy donors (HD). Result: The median pDCs proportion of pDC-AML/MDS was 8.0% (range 2.5-52.0%). As of June 2023, The median overall survival (OS) of patients with pDC-MDS/AML was 10.5 months shorter than non-pDC-AML (21.5 months; P＜0.05). In addition, the prognosis of pDC-AML/MDS patients can only be significantly improved after receiving allogenic hematopoietic stem cell transplantation, showing a similar OS to that of non-pDC-AML patients. To further clarified the role of pDCs in these patients, we performed scRNA-seq and acquired 126,693 cells across all samples (8 pDC-AML, 6 BPDCN, 5 non-pDC-AML and 5 HD), and identified 13 clusters based on their transcriptional profile in the overall UMAP (Figure 1 A). Firstly, our single-cell sequencing data revealed significant differences in the proportions of bone marrow pDCs across pDC-AML, HDs, non-pDC-AML, and BPDCN patients. Notably, pDC proportions were significantly elevated in pDC-AML and BPDCN patients. Further differential expression analysis revealed striking differences in the transcriptomes of pDCs across these four groups. When comparing pDC-AML to HDs, we identified 801 upregulated and 150 downregulated genes. Upon comparing pDC-AML to BPDCN, we found 1110 upregulated and 765 downregulated genes, and when comparing pDC-AML to non-pDC-AML, we observed 1674 upregulated and 945 downregulated genes. To explore the functional implications of these differentially expressed genes (DEGs), these findings were explored further through Gene Set Enrichment Analysis (GSEA), and indicated a heightened response to interferon signaling within the pDC cells of pDC-AML patients. Concurrently, we also discovered an increased expression of gene sets associated with tumorigenic pathways (such as KRAS, PTEN, p53, RAPA, etc.) and those related to embryonic stem cell states in pDCs of pDC-AML. Drawing on our findings and existing research, we hypothesize that interferon signaling might play a pivotal role in the pathogenesis of pDC-AML. This could be achieved through the enhancement of cell proliferation and self-renewal capabilities, thereby facilitating disease progression. This hypothesis is further supported by our pseudotime analysis. After conducting a more detailed subgroup classification of pDC-AML patients, we found a developmental trajectory linking AML_HSC and pDCs specific to pDC-AML patients. Notably, such a correlation was not observed in the non-pDC-AML patient group. Conclusions: Our study revealed heterogeneity and underscores the crucial role of pDCs in pDC-AML, as we found that these patients had worse OS. We observed upregulation of interferon signaling and tumorigenic pathways in these pDCs. Moreover, pseudotime analysis suggested a potential developmental relationship between pDCs and AML_HSCs. These findings provide invaluable insights for further investigations into pDCs biological properties in pDC-AML pathology and therapy design.

Spatial Response to Pivekimab Sunirine (IMGN632) In Vivo in a BPDCN Model

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare, aggressive hematologic malignancy, which often manifests with skin lesions in addition to lymph node, blood, and bone marrow involvement. Standard of care treatments for BPDCN patients are intense chemotherapy or tagraxofusp (Elzonris®). Although many patients initially respond to standard-of-care therapies, most will eventually relapse. Overexpression of CD123 (IL-3Rα receptor) is a hallmark of BPDCN thus making this antigen an attractive target. Pivekimab sunirine is an antibody-drug-conjugate (ADC) comprised of a humanized anti-CD123 monoclonal antibody conjugated to a potent DNA-damaging agent, FGN849 via a cleavable linker. Pivekimab sunirine was granted orphan drug and Breakthrough Therapy designation and is currently being tested for the treatment of BPDCN patients as monotherapy and, as a triplet therapy in combination with azacitidine and venetoclax for the treatment of AML patients. Preclinically, pivekimab sunirine has demonstrated potent activity against BPDCN cells (Blood 2018 132:3956) and importantly, showed a favorable safety profile and promising efficacy in BPDCN patients (Hemasphere. 2022 Jun; 6 (Suppl): 1708-1709; ASH 2021, Abstract #1284). The goal of this study was to investigate the response to pivekimab sunirine in a pre-clinical model of BPDCN and to monitor spatial response in vivo. Pivekimab sunirine efficacy was evaluated in vitro on GEN2.2, a patient-derived BPDCN cell line, for 24h, 48h, or 72h at different concentrations. We observed a concentration and time-dependent efficacy at 48h or 72h of treatment with EC50s between 4pM and 12pM and between 1.3pM and 3pM respectively. Limited cytotoxicity was observed at the 24h time point. The efficacy of pivekimab sunirine was further confirmed in vivo in the GEN2.2 BPDCN model. Pivekimab sunirine treatment with either 0.024mg/kg or 0.08mg/kg doses at QWx3 (once weekly for 3 weeks) dosing regimen was able to restrain the tumor burden and significantly enhance survival compared to the vehicle group To assess spatial response to pivekimab sunirine, we utilized a bioluminescent (BLI) GEN2.2-luc model. Briefly, NSG mice were injected with 1x10 6 GEN2.2-luc cells followed by Fc receptor blockade on Day 2 for 24h. On Day 3, mice were treated with pivekimab sunirine (0.024mg/kg; QWx3) or vehicle intravenously. Organs were harvested on day 16 for the vehicle-treated group and day 30 for the pivekimab sunirine-treated group and tumor burden was assessed using luciferin. The vehicle group showed the presence of tumor cells in the bone marrow, spleen, and lungs. These results were confirmed by HES staining. Pivekimab sunirine treated mice showed no sign of tumor cells in any of the organs in BLI evaluation. HES staining confirmed the elimination of tumor cells in the lungs and the liver while few remaining tumor cells were observed in the spleen and the bone marrow. Overall, this work enabled us to validate the efficacy of pivekimab sunirine in a BPDCN model and to monitor its spatial effect. Data showed that pivekimab sunirine treatment significantly reduced tumor burden and increased survival compared to the vehicle group. Pivekimab sunirine treatment eradicated tumor cells in the lungs and the liver, while reducing the number of tumor cells in the spleen and bone marrow. Pivekimab sunirine is a potent ADC targeting CD123 and is highly efficacious against an aggressive BPDCN cell line model. This finding reinforces the importance of its use for the treatment of BPDCN patients.

Patient Characteristics and Outcomes of Allogeneic Hematopoietic Stem Cell Transplantation for Blastic Plasmacytoid Dendritic Cell Neoplasm (BPDCN)

Background: Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare, aggressive hematologic malignancy arising from plasmacytoid dendritic cells. It commonly presents as skin lesions with or without bone marrow, lymph node, central nervous system (CNS), or systemic involvement. Limited retrospective data have shown durable remissions after allogeneic (allo) hematopoietic cell transplantation (HCT). Methods: In this retrospective single-center analysis, we evaluated outcomes of 31 BPDCN patients treated with allo-HCT between September 2000 and June 2023 at our institution. Results: Median age of our cohort was 52 years [range 16-76 y]. Patient characteristics are summarized in the attached Table. Only 6 patients (19%) had their disease confined to skin and 4 (13%) had CNS/CSF involvement at diagnosis. Four patients (13%) had prior hematologic malignancies (HM), and 9 patients (29%) had a cytogenetic abnormality at baseline. Thirteen (42%) patients, who were evaluated by a next-generation sequencing Leukemia Mutation Panel, had TET2 mutation. Median time from diagnosis to HCT was 6.2 (3.2-42.4) months. Eight (26%) patients received tagraxofusp, matched unrelated donor was the most common donor type (39%), and fludarabine + busulfan-based conditioning was used in 17 (55%) patients. Post-transplant cyclophosphamide (PTCy) was used for GVHD prophylaxis in 23 (74%) patients. Median follow up was 23.9 (0.9-119.9) months. One-hundred day and 1-year non-relapse mortality was 9.7% and 23.1%, respectively. Grade 2 acute GVHD was seen in 9 patients (29%), and no grade 3-4 GVHD has been seen so far. Limited or extensive chronic GVHD was seen in 6 (21%) of 28 evaluable patients. Only 6 of the 31 (19%) allo-HCT patients progressed after HCT. Two-year PFS and OS was 56% and 67%, respectively. Patients receiving allo-HCT in first remission had significantly better median PFS (not reached vs. 11.3 months; p=0.034) and OS (not reached vs. 12.6 months; p=0.045). Conclusions: These results demonstrate the safety and efficacy of allo-HCT in BPDCN. Patients undergoing allo-HCT in first remission had significantly better outcomes. Prospective studies are needed to better define the role of allo-HCT in BPDCN.

Frontline Hyper-CVAD Plus Venetoclax for Pediatric Blastic Plasmacytoid Dendritic Cell Neoplasm.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematologic malignancy, especially in pediatrics, that can involve the bone marrow, skin, lymph nodes, and central nervous system (CNS). Given its variable clinical presentation, coupled with an immunohistochemistry pattern (CD4, CD56, TCF4, TCL-1, and CD123 positivity) that differs from other myeloid neoplasms, the diagnosis of BPDCN can be missed. Limited data are available to guide the treatment of pediatric BPDCN. Herein, we report a case of a pediatric patient who had BPDCN with central nervous system, orbital, and skin involvement. This patient achieved complete remission after receiving modified hyper-CVAD (hyperfractionated cyclophosphamide, vincristine, doxorubicin, and dexamethasone with venetoclax and intrathecal chemotherapy. He remains disease-free 200 days after receiving a stem cell transplant. This represents the first known published pediatric case using a modified hyper-CVAD plus venetoclax regimen for treating a pediatric BPDCN patient in the frontline setting.

Clinical Analysis of Patients with Blastic Plasmacytoid Dendritic Cell Neoplasm

To explore the clinical characteristics, treatment, and prognosis of patients with blastic plasmacytoid dendritic cell neoplasm(BPDCN). Clinical data of 5 patients diagnosed with BPDCN in Wuhan First Hospital and Wuhan Tongji Hospital from June 2016 to November 2021 were retrospectively analyzed. Among the 5 patients, 3 were male and 2 were female, with a median age of 28(10-52) years old. Four patients showed obvious skin damage at the initial diagnosis; the other one showed clinical manifestations of acute leukemia rather than obvious skin damage at the initial diagnosis, but infiltrated skin when the disease relapsed after treatment. Other infiltration sites of lesions included bone marrow (2/5), peripheral blood (2/5), lymph nodes (3/5), liver and spleen (2/5). All patients had no clinical manifestation of central nervous system infiltration. Tumor cell specific immune markers CD4, CD56, CD123 were all positive, and the median Ki-67 index was 70%. TET2, ASXL1 and NRAS gene mutations were found respectively in 3 patients by next-generation sequencing technique (NGS). ALL-like, AML-like and invasive NK/T cell lymphoma-like first-line induction chemotherapy regimens were used for the patients. One patient died of severe complications during the early stage of chemotherapy, 3 patients were evaluated as CR, and 1 patient was evaluated as PR. 2 patients were recurred and progressed after induction of chemotherapy, and one of them was evaluated as CR after re-treatment. One patient received autologous hematopoietic stem cell transplantation (auto-HSCT) and got long-term survival (OS 87 months). 3 patients received allogeneic hematopoietic stem cell transplantation (allo-HSCT), of which one died of transplantation related complications, and 2 cases survived. The median follow-up time of 4 patients with evaluable efficacy was 28.5(9-84) months, the median OS time was 31.5(10-87) months. BPDCN is a highly heterogeneous malignant tumor with a poor prognosis. HSCT, especially allo-HSCT can significantly improve the prognosis of BPDCN patients.

Primary blastic plasmacytoid dendritic cell neoplasm: a US population-based study.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and poorly understood hematopoietic malignancy. This study aimed to investigate the clinical characteristics and prognostic factors in patients with primary BPDCN. Patients diagnosed with primary BPDCN from 2001 to 2019 were extracted from the Surveillance, Epidemiology and End Results (SEER) database. Survival outcome was analysed with Kaplan-Meier method. Prognostic factors were evaluated based on the univariate and multivariate accelerated failure time (AFT) regression analysis. A total of 340 primary BPDCN patients were included in this study. The average age was 53.7 ± 19.4 years, with 71.5% being male. The mostly affected sites were lymph nodes (31.8%). Most patients (82.1%) received chemotherapy, while 14.7% received radiation therapy. For all the patients, the 1-year, 3-year, 5-year, and 10-year overall survival (OS) were 68.7%, 49.8%, 43.9%, and 39.2%, respectively, and the corresponding disease-specific survival (DSS) were 73.6%, 56.0%, 50.2%, and 48.1%, respectively. Univariate AFT analysis showed that older age, marital status of divorced, widowed and separated at diagnosis, primary BPDCN only, treatment delay for 3-6 months and without radiation therapy were significantly associated with poor prognosis of primary BPDCN patients. But multivariate AFT analysis indicated that older age was independently associated with worse survival, while second primary malignancies (SPMs) and radiation therapy were independently associated with extended survival. Primary BPDCN is a rare disease with poor prognosis. Advanced age was linked independently to poorer survival, while SPMs and radiation therapy were linked independently to prolonged survival.

Incidence, prognostic factors and survival outcomes in patients with blastic plasmacytoid dendritic cell neoplasm: a retrospective study in the SEER database.

There are few large-scale epidemiological and prognostic studies on blastic plasmacytoid dendritic cell neoplasm (BPDCN) due to its rarity. We used the Surveillance, Epidemiology, and End Results (SEER) database to investigate the incidence, clinical characteristics, prognostic factors, and survival trends of BPDCN. The age-adjusted incidence of BPDCN had a bimodal pattern with peaks in those under 20 and above 60 years. Of 697 patients, the median age at diagnosis was 31 years. The most common primary sites were lymph nodes (59.4%), followed by bone marrow (17.1%) and skin (11.6%). Extranodal involvement (59.7%) was more common in patients aged 60 years and above, while lymph node involvement was predominant in other age groups. The 1-year, 3-year, and 5-year OS rates were 90.7%, 83.7%, and 82.3% in patients aged under 20, but dropped to 53.1%, 27.7%, and 20.0% in patients aged 60 and above. Multivariate Cox regression analysis revealed that age, sex, and first malignancy were independent prognostic factors for OS. Based on this regression model, a nomogram was built with high discrimination and calibration. The incidence, clinical characteristics, and prognosis of BPDCN patients vary by age group. Moreover, using the nomogram to predict OS can help guide individualized evaluations and clinical decisions.

Unmet Clinical Needs and Management Recommendations for Blastic Plasmacytoid Dendritic Cell Neoplasm: A Consensus-based Position Paper From an Ad Hoc International Expert Panel.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a hematological malignancy characterized by recurrent skin nodules, an aggressive clinical course with rapid involvement of hematological organs, and a poor prognosis with overall survival. The rarity of the disease results in a few large-scale studies, a lack of controlled clinical trials for its management, and a lack of evidence-based guidelines. Here, we present a review of unmet clinical needs on the management of BPDCN by a panel of eleven experts involved in the research and clinical practice of BPDCN. Recommendations and proposals were achieved by multiple-step formalized procedures to reach a consensus after a comprehensive analysis of the scientific literature. The panel analyzed the critical issues of diagnostic pathway, prognostic stratification, therapy for young and fit patients and elderly and unfit patients, indication for allotransplant and for autotransplant, indication for central nervous system prophylaxis, and management of pediatric BPDCN patients. For each of these issues, consensus opinions were provided and, when appropriate, proposals for advancement in clinical practice were addressed. The hope is that this comprehensive overview will serve to improve the practice of BPDCN and inform the design and implementation of new studies in the field.

Clinical Characteristics and Treatment of Blastic Plasmacytoid Dendritic Cell Neoplasm

To explore the clinical manifestations, diagnosis, treatment and prognosis of blastic plasmacytoid dendritic cell neoplasm(BPDCN). The clinical features, bone marrow morphology and immunophenotyping, treatment and prognosis of 4 patients with BPDCN were analyzed retrospectively. 4 patients had bone marrow， spleen and lymph nodes involvement， 2 patients had skin lesions， and 3 patients had central nervous system infiltration． Tailing phenomenon of abnormally cells could be seen in bone marrow. The immunophenotyping showed that CD56, CD4 and CD123 expression was observed in 4 patients， and CD304 in 3 patients． One patient refused chemotherapy and died early. Both patients achieved complete remission after the initial treatment with DA+VP regimen, 1 of them achieved complete remission after recurrence by using the same regimen again． One patient failed to respond to reduced dose of DA+VP chemotherapy, and then achieved complete remission with venetoclax+azacitidine. The malignant cells in BPDCN patients often infiltrate bone marrow, spleen and lymph nodes, and have specical phenotypes, with poor prognosis. The treatment should take into account both myeloid and lymphatic systems. The treatment containing new drugs such as BCL-2 inhibitors combined with demethylation drugs is worth trying.

Clonal Hematopoiesis Evolves into Dendritic Cell Neoplasm through the Acquisition of UV Mutations in the Skin

Background Expansion of blood cells derived from a single mutated blood stem cell - clonal hematopoiesis - often precedes leukemic transformation. However, the circumstances that promote or prevent transformation are poorly understood. Here, we investigate the evolution of clonal hematopoiesis into blastic plasmacytoid dendritic cell neoplasm (BPDCN), an aggressive blood cancer that often presents with malignant cells isolated to the skin (referred to as skin-only disease). We gain a better understanding of the influence of site-specific selective pressures and the role of TET2 mutations, which may inform interventions to prevent disease progression. Methods We analyzed bone marrow and skin from 13 BPDCN patients using targeted, exome, and whole-genome sequencing, with germline controls. We performed multimodal single-cell sequencing (10x 3' v3.1 single-cell RNA-seq with genotyping of expressed variants) on bone marrow from 6 healthy donors (20,411 cells), 5 skin-only BPDCN patients with malignant cells in the skin but not conventionally detectable in marrow (36,018 cells), and 6 BPDCN patients with overt bone marrow involvement (30,582 cells). For functional studies, we targeted Tet2 using CRISPR/Cas9 in mouse blood progenitor cells immortalized by an estrogen receptor hormone binding domain fused to HoxB8, which undergo synchronized differentiation to myeloid and dendritic cells upon estrogen withdrawal. We used CellRanger, Seurat, RandomForest machine learning, and the R tidyverse package collection for bioinformatics. Results Genetics allowed us to reconstruct the evolution of BPDCN across bone marrow and skin (representative patient, panel a). Invariably, we detected founder mutations in marrow, including TET2 inactivation in 9/13 patients (two mutations, likely bi-allelic, in 5/9). Single-cell sequencing of marrow from 5 skin-only patients showed that pre-malignant mutant stem cells contributed to multiple lineages, and that TET2 mutated clones were myeloerythroid-biased. We generated a gene expression signature to identify rare malignant BPDCN cells in marrow of skin-only patients. In 3/5 patients, we identified rare cells (0.03-0.19%) with the transcriptional profile of fully transformed cells, and concurrent single-cell genetic analysis suggested that these cells originated from the skin tumor (panel b). To assess whether disseminated skin tumor cells establish bone marrow disease, we quantified mutational signatures: skin tumors and malignant BPDCN marrow cells in 5/5 patients harbored UV-induced mutations, likely acquired in a single skin-resident plasmacytoid dendritic cell (pDC) during malignant transformation. Finally, we edited Tet2 in mouse myelo-dendritic progenitors and tested the response to UV irradiation in vitro. In addition to observing that Tet2 inactivation increases dendritic cell commitment, the more striking result was a survival advantage of Tet2-mutated cells in the presence of UV (n = 6, fold change 1.803, P = 0.0012). These results highlight an unexpected function of TET2 that may predispose mutated pDCs to survive UV-induced DNA damage in the skin, leading to disease progression. Conclusion The complex evolution of BPDCN traverses multiple anatomic sites prior to full transformation. This allows for accurate sequencing of oncogenic events. Disease evolution frequently starts with acquisition of a leukemia-associated mutation in a multipotent blood stem cell, leading to clonal expansion. In the most frequently observed scenario, bi-allelic TET2 inactivation promotes myeloerythroid bias, increases dendritic cell commitment, and confers resistance to UV-mediated cell death. Subsequent evolution of skin-resident mutant pDCs leads to a high burden of UV-induced mutations and ultimate transformation. Dissemination of malignant cells, which can be detected by integrating single-cell gene expression and mutation profiles, initiates "retrograde" bone marrow disease. Our discovery that multiple anatomic sites - and local selective pressures - play a role in disease progression provides a template to study multi-site evolution of clonal hematopoiesis. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

BPDCN MYB Fusions Bind Cell Cycle Gene Promoters, Reactivate Self-Renewal in Progenitor Cells and Induce Myeloid/Dendritic Leukemia

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare acute leukemia with poor prognosis arising from the plasmacytoid dendritic cell (pDC) lineage. MYB is a hematopoietic transcription factor overexpressed in many leukemias. Genomic rearrangements of MYB were identified in a significant fraction of BPDCNs, including in cases without any other clear driver mutations, and result in its fusion to one of several partner genes (Suzuki et al., Leukemia 2017). These fusions are rare or absent in other acute leukemias and the mechanisms by which they contribute to BPDCN oncogenesis are not understood. To examine the impact of Myb fusions on hematopoietic differentiation and leukemogenesis, we used mouse bone marrow progenitors immortalized by estradiol (E2)-dependent activation of HoxB8 and culture with Flt3 ligand (HoxB8-FL cells). We used HoxB8-FL cells deficient in Cdkn2a, since CDKN2A deletion is present in up to ~67% of BPDCNs (Lucioni et al., Blood 2011) but is rare in other myeloid leukemias. HoxB8-FL cells differentiate into myeloid, lymphoid and dendritic cells in vitro upon withdrawal of E2, or in vivo upon transplantation. They therefore represent lymphoid-primed multipotent progenitor (LMPP)-like cells that are unable to self-renew in the absence of E2. We co-expressed a dTom reporter with V5-tagged Myb constructs in HoxB8-FL cells: wild-type full-length Myb (Myb-FL), truncated Myb (Myb-TR) or Myb-PLEKHO1. MYB-PLEKHO1 is the most frequent fusion in BPDCN patients, while truncated Myb is analogous to recurrent BPDCN MYB fusions in which the partner is out-of-frame. Empty vector was used as a control. HoxB8-FL cells expressing Myb-FL, Myb-TR or Myb-PLEKHO1 displayed arrested differentiation upon withdrawal of E2 in vitro (Figure 1). While all empty vector-transduced cells had upregulated CD11b and/or CD11c at day 7 post-E2 withdrawal, Myb overexpression caused an accumulation of CD11b-CD11c- undifferentiated cells. In vivo, a similar effect was observed at day 7 post-transplantation: dTom+ CD11b-CD11c-CD19-B220- undifferentiated cells were still present in the bone marrow of Myb-FL, Myb-TR and Myb-PLEKHO1 recipient mice, while in empty vector recipients all dTom+ cells expressed at least one of these differentiation markers. Surprisingly, we observed long-term persistence of dTom+ cells in the peripheral blood of Myb-TR and Myb-PLEKHO1, but not Myb-FL, recipients. This developed into lethal malignancy in 100% of Myb-TR and Myb-PLEKHO1 recipients by 28 weeks (Figure 2). Malignant cells showed blast-like morphology of acute leukemia and expressed markers of a myeloid/dendritic progenitor (Kit+CD11b+Cx3cr1+). dTom+ disease was never observed in Myb-FL or empty vector recipients (log-rank P<0.001). Together, while expression of either full-length Myb or Myb fusions impaired myeloid/dendritic differentiation, only Myb rearrangements associated with BPDCN generated a fully penetrant leukemia. To investigate chromatin-level differences between physiologically expressed wild-type MYB and MYB fusions, we performed Cut&Run in K562 cells with V5-tagged MYB-FL, MYB-TR or MYB-PLEKHO1 knocked in to the endogenous MYB locus using CRISPR/Cas9 and homology-directed repair. We observed increased binding of MYB-TR and MYB-PLEKHO1 relative to MYB-FL at promoters of cell cycle genes that function at the G2/M checkpoint, including CDC20, CDCA3 and CKS2. These binding sites contained canonical MYB binding motifs, indicating that MYB fusions increase direct DNA binding at chromatin involved in control of specific cell cycle genes. Cut&Run for V5-Myb-PLEKHO1 in mouse leukemias revealed similar direct DNA binding at cell cycle gene promoters. Moreover, expression of G2/M cell cycle genes was enriched in patient BPDCNs relative to normal pDCs. Our data suggest that BPDCN MYB fusions exert distinct oncogenic effects to overexpression of wild-type MYB. In addition to arresting differentiation, BPDCN MYB fusions can reactivate self-renewal in progenitor cells, which may occur through increased direct DNA binding at cell cycle gene promoters. This may explain the simple genetics of MYB-rearranged BPDCN, which lack other recurrent myeloid-type mutations, if the fusions are sufficient to generate leukemia via these dual roles. These data also indicate that therapeutic strategies targeting MYB and/or specific cell cycle checkpoints may be active in BPDCN. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Genome-Wide DNA Methylation Profiling in Blastic Plasmacytoid Dendritic Cell Neoplasm

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and aggressive blood cancer and an ongoing therapeutic challenge. In a recent multiomics analysis, we characterized the unique molecular landscape of BPDCN. Beyond an expected classical pDC-derived subtype, we thereby identified a common(c)DC-enriched subtype, which was shown to predominantly arise in elderly patients, whilst harboring fewer mutations and an inferior outcome. The identification of several therapeutically targetable vulnerabilities may pave the way for precision oncology approaches toward this rare cancer. Several genomic alterations in both subtypes were found to be known determinants of the epigenetic regulation of gene expression. However, the epigenetic landscape of BPDCN remains sparsely characterized. We therefore characterized the genome-wide DNA methylation patterns in 54 BPDCN patients on the Illumina MethylationEPIC BeadChip and correlated our findings with WES/RNA-seq data from both previous and new studies. Further, we evaluated our observations according to the newly defined subtypes of BPDCN. Unsupervised clustering of the 420 most variably methylated cytosine guanine dinucleotide (CpG) sites resulted in the segregation of the study cohort into four clusters. These were subsequently annotated genomically and transcriptionally in a clinical context. Cluster two was hereby shown to be of special interest as it was exclusively composed of C2-BPDCN cases with SRSF2 or DNMT3A mutations. Cluster four revealed a strong C1-BPDCN predominance and typical C1 driver mutations including EP300, ARID2 and NF1 (Figure 1). Secondly, differential methylation analysis according to our recently established subtypes of BPDCN revealed a subset of significantly differentially methylated genes between the two clusters. Overall, we observed more methylation among C2 patients with regulation of several oncogenes and tumor suppressor genes such as NOTCH4 and MAP3K13 but a predominant regulation of inflammatory genes including TLR9, IL10RA and IL2RA. Our current observations suggest that genome-wide DNA methylation levels resemble and potentially help shape clinically and genomically distinct subgroups of BPDCN. Synoptic analysis of the methylome in concert with gene-expression profiling data alongside ATAC-Seq of our BPDCN samples is currently under way in order to integratively assess chromatin accessibility and ultimately transcriptional impact. Figure legend Figure 1. Genome-wide DNA methylation profiling in blastic plasmacytoid dendritic cell neoplasm. Unsupervised clustering of the 420 most variably methylated CpG sites resulted in the segregation of the study cohort into four clusters. These were subsequently annotated genomically and transcriptionally in a clinical context. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Genetic Landscape of BPDCN Arising in CML Remission

Background BPDCN (blastic plasmacytoid dendritic cell neoplasm) is a rare and highly aggressive hematologic malignancy which often affects skin lesion. BPDCN initially responds to traditional chemotherapy, but has a high relapse rate and a poor prognosis even after autologous or allogeneic stem cell transplantation (SCT). Almost all patients have CD123 positive tumor, and CD123 targeting therapies are being developed. BPDCN mainly develops de novo, however, up to 20% of BPDCN patients have prior history of other hematologic malignancies (CMML, AML, MDS). Some groups propose to classify BPDCN with PCHM (preexisting or concurrent hematologic malignancies) into a unique subtype based on the clinical course (Blood (2019) 134 (Supp.1): 2723). On the other hand, there are attempts to classify BPDCN according to molecular profile, and they defined two subclasses based on somatic mutations (Blood Cancer Journal (2022) 12:101). Thus substantial efforts are being made to classify BPDCN from various aspects, the classification is still under development due to insufficient number of cases. Herein we experienced a rare case of BPDCN arising in the course of CML as a history of PCHM. Unexpectedly, there have been no reports of BPDCN with preexisting CML, therefore, we report the clinical course and genetic background in our case. Case: 70 year old male Clinical course of CML: He was referred to our hospital at age 60 with elevated white blood cell count (93,550/ul, blast 1.0%). Diagnosis of CML (chronic phase) was made; Sokal score was 0.31 (low risk). With initial therapy of dasatinib 100 mg, his disease status achieved complete molecular response (CMR) at 24 months of treatment; achieved CMR (MR 4.5) at 43 months. Due to side effects (pleural effusion and cytopenia), dasatinib was discontinued at month 74 of treatment, and however, CMR has been maintained. Clinical course of BPDCN: At 48 months after completion of dasatinib treatment, multiple bruise-like skin lesions appeared on the head and abdomen. Skin biopsy revealed diffuse proliferation of blastic cells. Immunohistochemistry and flow cytometry were positive for CD4, CD56, and CD123, and a diagnosis of BPDCN was made. Bone marrow involvement (13%) was also observed. HyperCVAD/MA (cyclophosphamide, vincristine, doxorubicin, dexamethasone, methotrexate and arabinocytocine) was selected as induction therapy. The skin and bone marrow lesions rapidly improved and the patient achieved hematological remission, but a few CD123-positive tumor cells remained in the bone marrow. Considering autologous SCT, peripheral blood stem cell collection was performed. Unfortunately, the graft was contaminated with CD123-positive cells, and it was determined that autologous SCT was not expected. Allogeneic SCT was not planned due to age and regimen related toxicity. We are currently preparing to conduct a clinical trial of CD123-targeting agent. Molecular Analysis WES of peripheral blood and bone marrow samples was performed. At the hematological remission after 2 cycles of HyperCVAD/MA, high VAF mutations in the splicing factor ZRSR2 gene (p.Y292X (84.6-85.2% VAF)) as well as the histone modifiers ASXL1 (p.L743fs (40.6-43.1% VAF)) and TET2 (c.3955-2A>G (36.2-38.3% VAF), p.T1959fs (42.1-47.0% VAF)) were observed. ZRSR2 nonsense mutation site in our case was located 3 residues upstream of the previously reported site, which has not been reported in previous BPDCN cases (Cancer Discovery (2022) 12: 522-541). Although the tumor cell rate in each sample was less than 10%, the VAF of ZRSR2 mutation was high (84.6-85.2%), indicating that clonal hematopoiesis with ZRSR2 mutations underlies the development of BPDCN. Conclusion This is the first report of BPDCN with a history of CML as a preceding hematologic malignancy. Based on WES data at the remission of BPDCN, we confirmed that the patient had clonal hematopoiesis with not only ASXL1 and TET2 mutations, but also ZRSR2 mutation, a driver mutation characteristic of BPDCN. Despite the fact that clonal hematopoiesis with ASXL1 and TET2 mutations is occasionally observed after CML treatment with TKIs (Blood (2017) 129: 38-47), there were no case reports of BPDCN in patients with preexisting CML. These facts suggest that the presence of mechanism is essential for the development of BPDCN other than driver mutation in ZRSR2. Further investigation of BPDCN with PCHM would provide useful information on the pathogenesis of BPDCN. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

MPN-467 Findings From an Observational, Multicenter, Retrospective Analysis of Patients With Blastic Plasmacytoid Dendritic Cell Neoplasm Treated With Tagraxofusp in the European Expanded Access Program.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN), an aggressive hematologic malignancy with poor prognosis, is characterized by clonal expansion of plasmacytoid dendritic tumor cells expressing specific markers including the interleukin-3 receptor alpha (CD123). Tagraxofusp (TAG) is a CD123-targeted therapy approved by the FDA and EMA. A global expanded access program (EAP) was implemented prior to TAG's EMA authorization to provide access to patients in real-world practice. Main objectives were rates of complete response and incidence/severity of capillary leak syndrome (CLS). Key secondary objectives included rate of patients bridged to transplantation, survival, safety, number of cycles administered. Non-interventional, retrospective analysis of BPDCN patients enrolled in the European EAP from 08.2019-12.2021. 57 European centers (Germany, France, Italy, Switzerland, United Kingdom, Spain, Austria). 76 adult (median age 64 years, range 21-85 years) and 4 pediatric patients with BPDCN confirmed by hematopathology with established marker panels (including CD123). TAG 12 mcg/kg was administered intravenously once daily on days 1-5 (up to day 10 allowed) of a 21-day cycle. Hospitalization was required for the first cycle (subsequent cycles allowed outpatient administration). Review of case report forms and individual records of patients who met criteria for TAG prior to regulatory approval. Most patients were male (78%), representing real-world distribution. Sixty-three patients received TAG first-line and 17 patients as second/or further line of treatment. The median number of cycles was 2.5 (range 1-8) in first-line and 2.6 (range 1-13) in second-line/further, respectively. No deaths due to CLS were reported. Adverse events (AEs) mainly occurred in cycle 1, with similar rates and severity in older vs younger patients. Analysis is ongoing; data on safety, efficacy, transplantation, and time-related parameters will be reported. The is the largest retrospective analysis of real-world clinical practice outside of a clinical trial in BPDCN patients treated with TAG. Adherence to the EAP and multidisciplinary training is thought to have positively affected prevention and management of CLS and other grade 3-4 AEs. These preliminary results confirm the feasibility and safety of TAG, including in elderly patients, with manageable safety.

AML-465 Tagraxofusp, an Anti-CD123 Therapy, in Patients With Blastic Plasmacytoid Dendritic Cell Neoplasm: Sub-Analysis of a Pivotal Trial by Age and Baseline Disease Involvement

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an aggressive myeloid malignancy characterized by plasmacytoid dendritic cells that aberrantly express IL-3 receptor alpha (CD123). Tagraxofusp (TAG), a first-in-class CD123-targeted therapy, is the only approved treatment for BPDCN. In the pivotal trial TAG demonstrated a 57% complete response (CR) or clinical CR (CRc) and 75% objective response rate (ORR) in first-line patients. To determine CR+CRc, ORR, survival, and safety by age and baseline disease site involvement (skin-only, systemic-only, and skin+systemic). Sub-analysis of a 4-stage, single-arm phase 1/2 trial (NCT02113982) Setting: Eight US institutions Patients: 65 BPDCN patients receiving first-line therapy. TAG 12 mcg/kg on days 1-5 of a 21-day cycle. Response criteria for BPDCN and CTCAE criteria. CR/CRc and ORR were similar among age groups: <60y (n=17): 59% and 77%; >/=60-</=75y (n=39): 59% and 74%; and >75y (n=9): 44% and 78%, respectively. Patients with skin+systemic baseline disease (65%) had CR/CRc and ORRs of 50% and 76%, respectively. Twenty-one patients were bridged to hematopoietic stem cell transplantation (HSCT); 58% had baseline disease in ≥2 sites, with probability of survival at 12 and 24 months of 81% and 69%, respectively. In 44 patients not transplanted, four had prolonged responses >6 months; probability of survival at 12 and 24 months was 42% and 24%, respectively. Most common treatment-emergent adverse events (TEAEs) across all age cohorts were increased ALT (67%) and increased AST (61%). Most common TEAEs in the skin-only group were increased ALT and pyrexia (53% each); increased ALT, increased AST, fatigue, and nausea (75% each) in systemic-only group; increased ALT (71%) and increased AST (64%) in the skin+systemic group. Thirteen patients experienced capillary leak syndrome (3 grade 3, 1 grade 4, 2 grade 5). TAG as a first-line treatment for BPDCN was efficacious across all cohorts including older and patients with significant baseline disease. High rates of durable CRs enabled over half of patients in CR to be bridged to HSCT. Safety events were manageable and similar for older vs younger patients. Baseline disease involvement did not appear to predispose patients to different TEAEs.