Therapeutic effect of lenalidomide in a novel xenograft mouse model of human blastic NK cell lymphoma/blastic plasmacytoid dendritic cell neoplasm

Diagnosis, treatment, and genetic characteristics of blastic plasmacytoid dendritic cell neoplasm: A review

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a highly aggressive and extremely rare hematologic disease with a poor prognosis, involving mainly the skin and bone marrow. The immunophenotype of these tumor cells is characterized by the expression of CD4, CD56, CD123, TCL-1, and CD303. To date, no consensus has been reached on the standard of care for BPDCN. Currently, clinical treatment is mainly based on high-dose chemotherapy combined with hematopoietic stem cell transplantation. However, this treatment method has limitations for elderly, frail, and relapsed/refractory patients. In recent years, breakthroughs in molecular biology and genetics have not only provided new ideas for the diagnosis of BPDCN but also helped develop targeted treatment strategies for this disease. The emergence of targeted drugs has filled the gap left by traditional therapies and shown great clinical promise. This article focuses on the latest advances in genetics and targeted therapies for BPDCN, especially the emerging therapies that may provide new ideas for the clinical treatment of BPDCN.

Expanded natural killer cells potentiate the antimyeloma activity of daratumumab, lenalidomide, and dexamethasone in a myeloma xenograft model

The development of new treatment agents in recent decades has significantly improved the survival of patients with multiple myeloma (MM). Nonetheless, MM remains an incurable disease; therefore, novel combination therapies are required. Natural killer (NK) cells are one of the safest immunotherapeutic options. In this study, we found that the anti-myeloma activity of expanded NK cells (eNKs) was improved by daratumumab, lenalidomide, and dexamethasone (DRd) in an MM xenograft mouse model. NK cells expanded from peripheral blood mononuclear cells collected from MM patients were highly cytotoxic against DRd pretreated tumor cells in vitro. To mimic the clinical protocol, a human MM xenograft model was developed using human RPMI8226-RFP-FLuc cells in NOD/SCID IL-2Rγnull (NSG) mice. MM bearing mice were randomly divided into six groups: no treatment, eNK, Rd, Rd + eNKs, DRd, and DRd + eNKs. DRd significantly enhanced the cytotoxicity of eNKs by upregulating NK cell activation ligands and effector function. DRd in combination with eNKs significantly reduced the serum M-protein level and prolonged mouse survival. In addition, DRd significantly increased the persistence of eNK and homing to MM sites. These results show that the anti-myeloma activity of ex vivo-expanded and activated NK cells is augmented by the immunomodulatory effect of DRd in MM-bearing mice, suggesting the therapeutic potential of this combination for MM patients.

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.

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.

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.

Blastic Plasmacytoid Dendritic Cell Neoplasm

OPINION STATEMENT

While there is a high initial response rate with standard chemotherapeutic regimens for blastic plasmacytoid dendritic cell neoplasm (BPDCN), the responses are typically not durable and this remains a very aggressive disease with generally poor outcomes. For this reason, the standard approach for eligible patients has been high-dose induction chemotherapy preferably with acute lymphoblastic leukemia (ALL)-based regimens followed by consolidation with allogeneic hematopoietic stem cell transplantation (alloHSCT). Unfortunately, many patients with this disease are elderly and/or frail and cannot tolerate this therapy, and the low-dose regimens being used in this population are generally not as effective. However, this paradigm may be changing with the advent of newer targeted therapies, particularly the exploitation of CD123. SL-401 has shown very promising results with manageable toxicities and durable responses and appears to be a viable option for elderly or frail patients who are not eligible for transplant. The other CD123-directed therapies, especially chimeric antigen receptor-therapy (CAR-T), may also give promising results in trials that are currently underway. CAR-T has shown promise in a number of other hematologic malignancies, and toxicities have become more manageable as its use is becoming more widespread. While SL-401 has shown potential to provide durable responses even without transplant, we do not yet know whether it will be effective as a means to avoid transplant in patients who are otherwise eligible. All transplant-eligible patients should undergo alloHSCT consolidation given the current available data indicating this is the optimal approach to achieve a long-term remission. Once the CD123-directed therapies are established as standard regimens, future studies may be designed to investigate whether these therapies can be utilized without the use of transplant. Furthermore, combination therapy using anti-CD123 agents with high-dose induction chemotherapy or other low-dose regimens for elderly/frail patients should be investigated. Given the promising results in early clinical trials, it appears CD123 is the most viable target for BPDCN, and future studies should continue to exploit its expression on BPDCN cells.

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.

Immunomodulatory Drugs Exert Anti-Leukemia Effects in Acute Myeloid Leukemia by Direct and Immunostimulatory Activities

Immunomodulatory drugs (IMiDs) are anticancer drugs with immunomodulatory, anti-angiogenesis, anti-proliferative, and pro-apoptotic properties. IMiDs are currently used for the treatment of multiple myeloma, myelodysplastic syndrome, and B-cell lymphoma; however, little is known about efficacy in acute myeloid leukemia (AML). We proposed in this study to investigate the relevance of IMiDs therapy for AML treatment. We evaluated the effect of IMiDs on primary AML blasts (n = 24), and the impact in natural killer (NK) cell-mediated immunosurveillance of AML. Using primary AML cells and an immunodeficient mouse leukemia xenograft model, we showed that IMiDs induce AML cell death in vitro and impair leukemia progression in vivo. In addition, treatment of AML blasts with IMiDs resulted in enhanced allogeneic NK cell anti-leukemia reactivity. Treatment by pomalidomide of AML blasts enhanced lysis, degranulation, and cytokine production by primary allogeneic NK cells. Furthermore, the treatment with lenalidomide of patients with myeloid malignancies resulted in NK cell phenotypic changes similar to those observed in vitro. IMiDs increased CD56 and decreased NKp30, NKp46, and KIR2D expression on NK cells. Finally, AML blasts treatment with IMiDs induced phenotypic alterations including downregulation of HLA-class I. The effect of pomalidomide was not correlated with cereblon expression and A/G polymorphism in AML cells. Our data revealed, a yet unobserved, dual effects on AML affecting both AML survival and their sensitivity to NK immunotherapy using IMiDs. Our study encourages continuing investigation for the use of IMiDs in AML, especially in combination with conventional therapy or immunotherapy strategies.

Bortezomib as a new therapeutic approach for blastic plasmacytoid dendritic cell neoplasm

Blastic plasmacytoid dendritic cell neoplasm is an aggressive hematologic malignancy with a poor prognosis. No consensus regarding optimal treatment modalities is currently available. Targeting the nuclear factor-kappa B pathway is considered a promising approach since blastic plasmacytoid dendritic cell neoplasm has been reported to exhibit constitutive activation of this pathway. Moreover, nuclear factor-kappa B inhibition in blastic plasmacytoid dendritic cell neoplasm cell lines, achieved using either an experimental specific inhibitor JSH23 or the clinical drug bortezomib, interferes in vitro with leukemic cell proliferation and survival. Here we extended these data by showing that primary blastic plasmacytoid dendritic cell neoplasm cells from seven patients were sensitive to bortezomib-induced cell death. We confirmed that bortezomib efficiently inhibits the phosphorylation of the RelA nuclear factor-kappa B subunit in blastic plasmacytoid dendritic cell neoplasm cell lines and primary cells from patients in vitro and in vivo in a mouse model. We then demonstrated that bortezomib can be associated with other drugs used in different chemotherapy regimens to improve its impact on leukemic cell death. Indeed, when primary blastic plasmacytoid dendritic cell neoplasm cells from a patient were grafted into mice, bortezomib treatment significantly increased the animals’ survival, and was associated with a significant decrease of circulating leukemic cells and RelA nuclear factor-kappa B subunit expression. Overall, our results provide a rationale for the use of bortezomib in combination with other chemotherapy for the treatment of patients with blastic plasmacytoid dendritic cell neoplasm. Based on our data, a prospective clinical trial combining proteasome inhibitor with classical drugs could be envisaged.

Lenalidomide, celecoxib, and azacitidine therapy for blastic plasmocytoid dendritic cell neoplasm: a case report

Blastic plasmocytoid dendritic cell neoplasm is characterized by aggressive behavior with a tendency for systemic dissemination and a predilection for skin, lymph nodes, soft tissues, peripheral blood, or bone marrow. It usually occurs in elderly patients with a mean age between 60 and 70 years. Despite initial response to chemotherapy, the disease regularly relapses with a short median overall survival. Better outcomes have been reported with high-dose acute leukemia-like induction chemotherapy followed by consolidation with allogeneic hematopoietic stem cell transplantation. However, elderly patients are not candidates for intensive therapy or allogeneic stem cell transplantation. So, new active and tolerable drugs are needed. Our case illustrates that one cycle of lenalidomide and celecoxib provides at least a partial cutaneous and hematologic response, but this regimen was discontinued due to toxicity and followed by a consolidation/maintenance phase with azacitidine, thus achieving a final complete response with a much higher than expected progression-free and overall survival in an elderly patient with comorbidities. This information may be useful in the design of treatment approaches for elderly patients with blastic plasmocytoid dendritic cell neoplasm. However, it should be confirmed in clinical trials as well as by optimizing the induction and extending the consolidation/maintenance period to avoid early relapses after discontinuation and improve progression-free survival.

The presence of wild type p53 in hematological cancers improves the efficacy of combinational therapy targeting metabolism

Manipulation of metabolic pathways in hematological cancers has therapeutic potential. Here, we determined the molecular mechanism of action of the metabolic modulator dichloroacetate (DCA) in leukemic cells. We found that DCA induces the AMP-activated protein kinase (AMPK)/p53 pathway with increased efficacy in tumors expressing wild type (wt p53). Clinically relevant, low concentrations of doxorubicin synergize in vitro and in vivo with DCA to further enhance p53 activation and to block tumor progression. Leukemia cell lines and primary leukemic cells containing mutant p53 are resistant to the above-described combination approach. However, DCA synergized with the Hsp90 inhibitor 17-AAG to specifically eliminate these cells. Our studies strongly indicate that depending on the p53 status, different combination therapies would provide better treatment with decreased side effects in hematological cancers.

Blastic plasmacytoid dendritic cell neoplasm: diagnostic criteria and therapeutical approaches

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare haematological malignancy derived from the precursors of plamacytoid dendritic cells, with an aggressive clinical course and high frequency of cutaneous and bone marrow involvement. Neoplastic cells express CD4, CD43 (also termed SPN), CD45RA and CD56 (also termed NCAM1), as well as the plasmacytoid dendritic cell-associated antigens CD123 (also termed IL3RA), BDCA-2 (also termed CD303, CLEC4E) TCL1 and CTLA1 (also termed GZMB). The median survival is only a few months as the tumour exhibits a progressive course despite initial response to chemotherapy. The best modality of treatment remains to be defined. Generally, patients receive acute leukaemia-like induction, according to acute myeloid leukaemia (AML)-type or acute lymphoid leukaemia (ALL)-type regimens. The frequent neuromeningeal involvement indicates systematic pre-emptive intrathecal chemotherapy in addition to intensive chemotherapy. Allogeneic haematopoietic stem cell transplantation (HSCT), particularly when performed in first remission, may improve the survival. Preliminary data suggest a potential role for immunomodulatory agents and novel targeted drugs. Herein epidemiology, clinical manifestations, diagnosis and management of BPDCN will be presented. In detail, this review focuses on the therapeutic aspects of BPDCN, proposing a treatment algorithm for the management of the disease, including induction chemotherapy, allogeneic HSCT and intrathecal prophylaxis at different steps of treatment, according to compliance, biological and clinical characteristics of patients.

Chitinase 3-Like 1 Promotes Candida albicans Killing and Preserves Corneal Structure and Function by Controlling Host Antifungal Responses

Chitinase 3-like 1 (CHI3L1) has been shown to play a role in promoting antibacterial responses, decreasing tissue injury, and enhancing pulmonary repair. This study sought to elucidate the role of CHI3L1 in augmenting the corneal innate immune response to Candida albicans infection in an animal model of fungal keratitis. Flagellin applied topically 24 h prior to C. albicans inoculation significantly protected the corneal from C. albicans and induced CHI3L1 expression in C57BL/6 mouse corneas. CHI3L1, however, played a detectable but minor role in flagellin-induced protection. While C. albicans keratitis was more severe in the corneas treated with Chi3l1 small interfering RNA (siRNA), corneas treated with recombinant CHI3L1 before C. albicans inoculation had markedly ameliorated keratitis, reduced fungal load, and decreased polymorphonucleocyte (PMN) infiltration in an interleukin 13 receptor α2 (IL-13Rα2)-dependent manner. CHI3L1 treatment resulted in the induction of the antimicrobial peptides β-defensin 3, CRAMP, and chemokine CXCL10 and its receptor CXCR3 in corneal epithelial cells. Importantly, CHI3L1 administered after C. albicans inoculation also had strong protection against fungal keratitis, suggesting a therapeutic window. This is the first report demonstrating that CHI3L1 is induced during fungal infection, where it acts as an immunomodulator to promote fungal clearance and to regulate antifungal innate immune responses in the cornea.

Construction of Anti-CD20 Single-Chain Antibody-CD28-CD137-TCRζ Recombinant Genetic Modified T Cells and its Treatment Effect on B Cell Lymphoma

Background

Immunotherapy has been explored as a new therapy for B cell lymphoma, which is a non-Hodgkin’s lymphoma. Because CD20 is a B lymphocyte-specific marker, anti-CD20 single chain-tagged T lymphocytes have already begun to be experimentally used in B cell lymphoma treatment, but its use is still limited because of its unspecific targeting. T cells transfected with CD28 and CD137 can significantly improve the ability of cytokines secretion and anti-tumor effect, as well as extending T cell survival time and improving their proliferation ability.

Material/Methods

Genes containing anti-CD20-CD28-CD137-TCRζ were constructed. After cloning and sequencing, the plasmid was constructed and packaged by lentivirus. It was transfected to the peripheral blood T lymphocyte after identification transfection to induce the fusion protein expression. The cells were incubated with Raji cells and the LDH test was performed to detect the cytotoxic effect of CAR-T cells; the tumor volume and survival rate were measured to observe its inhibitory effect on B cell lymphoma in nude mice.

Results

Gene with anti-CD20-CD28-CD137-TCRζ was successfully constructed and transfected to the T cell surface. LDH assay revealed that CAR-T cells can kill the Raji cells with a killing rate of 32.89±6.26%. It can significantly inhibit B cell lymphoma growth in nude mice.

Conclusions

T lymphocytes transfected with anti-CD20-CD28-CD137-TCRζ fusion gene can kill B cell lymphoma, which could provide a new strategy for tumor treatment.

Blastic plasmacytoid dendritic cell neoplasm: update on molecular biology, diagnosis, and therapy

BACKGROUND

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematological malignancy with an aggressive clinical course. Most patients with BPDCN have skin lesions and simultaneous involvement of the peripheral blood, bone marrow, and lymph nodes.

METHODS

A search of PubMed and Medline was conducted for English-written articles relating to BPDCN, CD4(+)CD56(+) hematodermic neoplasm, and blastic natural killer cell lymphoma. Data regarding diagnosis, prognosis, and treatment were analyzed.

RESULTS

BPDCN is derived from precursor plasmacytoid dendritic cells. The diagnosis of BPDCN is based on the characteristic cytology and immunophenotype of malignant cells coexpressing CD4, CD56, CD123, blood dendritic cell antigens 2 and 4, and CD2AP markers. Multiple chromosomal abnormalities and gene mutations previously reported in patients with myeloid and selected lymphoid neoplasms were identified in approximately 60% of patients with BPDCN. Prospectively controlled studies to guide treatment decisions are lacking. The overall response rate with aggressive acute lymphoblastic leukemia-type induction regimens was as high as 90%, but the durability of response was short. Median survival rates ranged between 12 and 16 months. Patients with relapsed disease may respond to L-asparaginase-containing regimens. Allogeneic hematopoietic stem cell transplantation, particularly when performed during the first remission, may produce durable remissions in selected adults.

CONCLUSIONS

BPDCN is a rare aggressive disease that typically affects elderly patients. The most commonly affected nonhematopoietic organ is the skin. Although BPDCN is initially sensitive to conventional chemotherapy regimens, this response is relatively short and long-term prognosis is poor. In the near future, novel targeted therapies may improve outcomes for patients with BPDCN.

In vivo and in vitro sensitivity of blastic plasmacytoid dendritic cell neoplasm to SL-401, an interleukin-3 receptor targeted biologic agent

Blastic plasmacytoid dendritic cell neoplasm is an aggressive malignancy derived from plasmacytoid dendritic cells. There is currently no accepted standard of care for treating this neoplasm, and therapeutic strategies have never been prospectively evaluated. Since blastic plasmacytoid dendritic cell neoplasm cells express high levels of interleukin-3 receptor α chain (IL3-Rα or CD123), antitumor effects of the interleukin-3 receptor-targeted drug SL-401 against blastic plasmacytoid dendritic cell neoplasm were evaluated in vitro and in vivo. The cytotoxicity of SL-401 was assessed in patient-derived blastic plasmacytoid dendritic cell neoplasm cell lines (CAL-1 and GEN2.2) and in primary blastic plasmacytoid dendritic cell neoplasm cells isolated from 12 patients using flow cytometry and an in vitro cytotoxicity assay. The cytotoxic effects of SL-401 were compared to those of several relevant cytotoxic agents. SL-401 exhibited a robust cytotoxicity against blastic plasmacytoid dendritic cell neoplasm cells in a dose-dependent manner. Additionally, the cytotoxic effects of SL-401 were observed at substantially lower concentrations than those achieved in clinical trials to date. Survival of mice inoculated with a blastic plasmacytoid dendritic cell neoplasm cell line and treated with a single cycle of SL-401 was significantly longer than that of untreated controls (median survival, 58 versus 17 days, P<0.001). These findings indicate that blastic plasmacytoid dendritic cell neoplasm cells are highly sensitive to SL-401, and support further evaluation of SL-401 in patients suffering from blastic plasmacytoid dendritic cell neoplasm.

A phase I/II study of lenalidomide in combination with sunitinib in patients with advanced or metastatic renal cell carcinoma

BACKGROUND

This phase I/II study was conducted to determine the maximum tolerated dose (MTD), safety, and efficacy of lenalidomide plus sunitinib in metastatic renal cell carcinoma (RCC) patients.

PATIENTS AND METHODS

Patients with histologically confirmed, metastatic RCC were treated with 10 mg/day lenalidomide plus 37.5 mg/day sunitinib, orally in 21-day cycles. Doses were escalated to determine the MTD in phase I, with additional patients planned at this dose in phase II. Primary end points were MTD and response rate.

RESULTS

Sixteen patients received a median of 2, 3, and 5 cycles in cohort 1 [lenalidomide 10 mg (days 1-21) and sunitinib 37.5 mg (days 1-21)], cohort 2 [lenalidomide 10 mg (days 1-21) and sunitinib 37.5 mg (days 1-14)], and cohort 3 [lenalidomide 15 mg (days 1-21) and sunitinib 37.5 mg (days 1-14)], respectively. Median treatment durations were 41, 63, and 97 days for lenalidomide; and 41, 57, and 97.5 days for sunitinib. The MTD was found to be continuous dosing of lenalidomide 10 mg/day plus sunitinib 37.5 mg/day for 14 of 21 days. Dose-limiting toxicities included neutropenia, leukopenia, thrombocytopenia, asthenia, atrial fibrillation, and increased transaminases. The most frequent grade 3-4 treatment-emergent adverse events were hematologic, including neutropenia and leukopenia. One patient achieved partial response, and seven had stable disease of which three were confirmed at subsequent tumor assessments. B cells and several T-cell subsets were modulated versus baseline.

CONCLUSION

The dose schedules of lenalidomide and sunitinib evaluated in this study were not well tolerated; cumulative toxicity precluded enrollment at the MTD.

Human cancer growth and therapy in immunodeficient mouse models

Since the discovery of the "nude" mouse more than 40 years ago, investigators have attempted to model human tumor growth in immunodeficient mice. Here, we summarize how the field has advanced over the ensuing years owing to improvements in the murine recipients of human tumors. These improvements include the discovery of the scid mutation and development of targeted mutations in the recombination-activating genes 1 and 2 (Rag1(null), Rag2(null)) that severely cripple the adaptive immune response of the murine host. More recently, mice deficient in adaptive immunity have been crossed with mice bearing targeted mutations designed to weaken the innate immune system, ultimately leading to the development of immunodeficient mice bearing a targeted mutation in the gene encoding the interleukin 2 (IL2) receptor common γ chain (IL2rg(null), also known in humans as cytokine receptor common subunit γ). The IL2rg(null) mutation has been used to develop several immunodeficient strains of mice, including the NOD-scid IL2rg(null) (NSG) strain. Using NSG mice as human xenograft recipients, it is now possible to grow almost all types of primary human tumors in vivo, including most solid tumors and hematological malignancies that maintain characteristics of the primary tumor in the patient. Programs to optimize patient-specific therapy using patient-derived xenograft tumor growth in NSG mice have been established at several institutions, including The Jackson Laboratory. Moreover, NSG mice can be engrafted with functional human immune systems, permitting for the first time the potential to study primary human tumors in vivo in the presence of a human immune system.

Diagnostic and therapeutic advances in blastic plasmacytoid dendritic cell neoplasm: a focus on hematopoietic cell transplantation

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an exceedingly rare disorder categorized under acute myeloid leukemia by the World Health Organization. Phenotypically, malignant cells coexpress CD4(+) and CD56(+) without coexpressing common lymphoid or myeloid lineage markers. BPDCN frequently expresses CD123, TCL1, BDCA-2, and CD2AP. Restriction of CD2AP expression to plasmacytoid dendritic cells makes it a useful tool to help confirm diagnosis. Clonal complex chromosome aberrations are described in two-thirds of cases. Eighty percent of BPDCN cases present with nonspecific dermatological manifestations, prompting inclusion in the differential diagnosis of atypical skin rashes refractory to standard treatment. Prognosis is poor, with a median survival of less than 18 months. No prospective randomized data exist to define the most optimal frontline chemotherapy. Current practice considers acute myeloid leukemia-like or acute lymphoblastic leukemia-like regimens acceptable for induction treatment. Unfortunately, responses are short-lived, with second remissions difficult to achieve, underscoring the need to consider hematopoietic cell transplantation early in the disease course. Allografting, especially if offered in first remission, can result in long-term remissions. Preclinical data suggest a potential role for immunomodulatory agents in BPCDN. However, further research efforts are needed to better understand BPDCN biology and to establish evidence-based treatment algorithms that might ultimately improve overall prognosis of this disease.