Proteasome inhibitors exert cytotoxicity and increase chemosensitivity via transcriptional repression of Notch1 in T-cell acute lymphoblastic leukemia

Bortezomib Is Effective in the Treatment of T Lymphoblastic Leukaemia by Inducing DNA Damage, WEE1 Downregulation, and Mitotic Catastrophe

T lymphoblastic leukemia (T-ALL) is an aggressive haematolymphoid malignancy comprising 15% of acute lymphoblastic leukemia (ALL). Although its prognosis has improved with intensive chemotherapy, the relapse/refractory disease still carries a dismal prognosis. Thus, there is an urgent need to develop novel therapy for T-ALL. Bortezomib, a 26S proteasome inhibitor, is licensed to treat plasma cell myeloma and mantle cell lymphoma. Due to its favorable side effect profile, it is a novel agent of research interest in the treatment of ALL. Despite an increasing number of clinical trials of bortezomib in T-ALL, its detailed mechanistic study in terms of DNA damage, cell cycle, and mitotic catastrophe remains elusive. Moreover, WEE1, a protein kinase overexpressed in ALL and involved in cell-cycle regulation, has been known to be a novel therapeutic target in many cancers. But the role of bortezomib in modulating WEE1 expression in ALL still remains elusive. In this study, we demonstrate the therapeutic efficacy of bortezomib on T-ALL primary samples and cell lines. Our findings reveal that bortezomib treatment induces DNA damage and downregulates WEE1, leading to G2-M cell-cycle progression with damaged DNA. This abnormal mitotic entry induced by bortezomib leads to mitotic catastrophe in T-ALL. In conclusion, our findings dissect the mechanism of action of bortezomib and provide further insights into the use of bortezomib to treat T-ALL. Our findings suggest the possibility of novel combination therapy using proteasome inhibitors together with DNA-damaging agents in the future, which may fill the research gaps and unmet clinical needs in treating ALL.

Modulation of Notch Signaling by Small-Molecular Compounds and Its Potential in Anticancer Studies

Notch signaling is responsible for conveying messages between cells through direct contact, playing a pivotal role in tissue development and homeostasis. The modulation of Notch-related processes, such as cell growth, differentiation, viability, and cell fate, offer opportunities to better understand and prevent disease progression, including cancer. Currently, research efforts are mainly focused on attempts to inhibit Notch signaling in tumors with strong oncogenic, gain-of-function (GoF) or hyperactivation of Notch signaling. The goal is to reduce the growth and proliferation of cancer cells, interfere with neo-angiogenesis, increase chemosensitivity, potentially target cancer stem cells, tumor dormancy, and invasion, and induce apoptosis. Attempts to pharmacologically enhance or restore disturbed Notch signaling for anticancer therapies are less frequent. However, in some cancer types, such as squamous cell carcinomas, preferentially, loss-of-function (LoF) mutations have been confirmed, and restoring but not blocking Notch functions may be beneficial for therapy. The modulation of Notch signaling can be performed at several key levels related to NOTCH receptor expression, translation, posttranslational (proteolytic) processing, glycosylation, transport, and activation. This further includes blocking the interaction with Notch-related nuclear DNA transcription. Examples of small-molecular chemical compounds, that modulate individual elements of Notch signaling at the mentioned levels, have been described in the recent literature.

Therapeutic approaches for HTLV-1-associated adult T-cell leukemia/lymphoma: a comprehensive review

Adult T-cell leukemia/lymphoma (ATLL), an infrequent malignancy resultant from human T-cell lymphotropic virus type I (HTLV-1), exhibits a spectrum of phenotypes, encompassing acute, smoldering, lymphomatous, and chronic variants, each bearing distinct clinical presentations. The preponderant acute manifestation is characterized by hypercalcemia, systemic manifestations, organomegaly, and dermatological eruptions. Conversely, the chronic phenotype is typified by lymphocytosis and/or cutaneous eruptions, while smoldering ATLL assumes an asymptomatic course. Immunocompromise afflicts ATLL patients, heightening their vulnerability to opportunistic infections that frequently intricately intertwine with disease progression. Therefore, an early diagnosis is crucial to manage the disease appropriately. While conventional chemotherapeutic regimens have shown limited success, especially in acute and lymphoma types, recent studies suggest that allogeneic stem cell transplantation might enhance treatment results because it has shown promising outcomes in some patients. Novel therapeutics, such as interferon and monoclonal antibodies, have also shown promise, but more research is needed to confirm their efficacy. Moreover, the identification of biomarkers for ATLL and genetic changes in HTLV-1 infected cells has led to the development of targeted therapies that have shown remarkable success in clinical trials. These targeted therapies have the potential to offer a more personalized approach to the treatment of ATLL. The aim of our review is to elaborate on conventional and novel therapies and the efficiency of mentioned treatments.

NOTCH Signaling in Mantle Cell Lymphoma: Biological and Clinical Implications

Despite major progress in mantle cell lymphoma (MCL) therapeutics, MCL remains a deadly disease with a median survival not exceeding four years. No single driver genetic lesion has been described to solely give rise to MCL. The hallmark translocation t(11;14)(q13;q32) requires additional genetic alterations for the malignant transformation. A short list of recurrently mutated genes including ATM, CCND1, UBR5, TP53, BIRC3, NOTCH1, NOTCH2, and TRAF2 recently emerged as contributors to the pathogenesis of MCL. Notably, NOTCH1 and NOTCH2 were found to be mutated in multiple B cell lymphomas, including 5-10% of MCL, with most of these mutations occurring within the PEST domain of the protein. The NOTCH genes play a critical role in the early and late phases of normal B cell differentiation. In MCL, mutations in the PEST domain stabilize NOTCH proteins, rendering them resistant to degradation, which subsequently results in the upregulation of genes involved in angiogenesis, cell cycle progression, and cell migration and adhesion. At the clinical level, mutated NOTCH genes are associated with aggressive features in MCL, such as the blastoid and pleomorphic variants, a shorter response to treatment, and inferior survival. In this article, we explore in detail the role of NOTCH signaling in MCL biology and the ongoing efforts toward targeted therapeutic interventions.

Phase 2 study of combination chemotherapy with bortezomib in children with relapsed and refractory acute lymphoblastic leukemia

Treatment outcomes for children with relapsed and refractory acute lymphoblastic leukemia (R/R-ALL) remain poor, and the optimal induction therapy has not been determined. Bortezomib is a proteasome inhibitor that acts synergistically and additively with standard chemotherapy for ALL. We evaluated the efficacy and safety of combination chemotherapy with bortezomib in children with R/R-ALL. This single-arm, multicenter, phase 2 study was conducted in Japan between 2016 and 2020. Eligible patients were divided into two cohorts: a high-risk first-relapse cohort of untreated patients with high-risk first-relapsed ALL and an expansion cohort of patients with refractory ALL, including multiple relapses, relapse after allogeneic hematopoietic cell transplantation, and induction failure. All patients received a single course of chemotherapy as induction therapy. Sixteen patients (10 in the high-risk first-relapse cohort, six in the expansion cohort) were evaluable. The overall remission rate after induction therapy was 60% in the high-risk first-relapse cohort and 16.7% in the expansion cohort. All patients had minimal residual disease. Adverse events were acceptable except for interstitial lung disease and hypoxia in a patient in the expansion cohort, but addition of bortezomib to conventional chemotherapy did not produce obvious improvement in children with R/R-ALL.

T-cell acute lymphoblastic leukemia: promising experimental drugs in clinical development

INTRODUCTION

Despite advances in treatment approaches in acute lymphoblastic leukemia (ALL), the prognosis of adults with newly diagnosed T-ALL remains poor, as well as that of adults and children with relapsed disease. Novel targeted therapies are therefore needed.

AREAS COVERED

This review summarizes promising emerging strategies for the treatment of T-ALL.

EXPERT OPINION

The recent molecular characterization of T-ALL has led to the identification of new therapeutic targets. Small-molecules inhibitors and other targeted therapies have therefore been recently developed and are currently under clinical investigations. Similarly, first studies involving monoclonal antibodies and chimeric antigen receptor (CAR) T cells have shown encouraging results. Improvement of outcome with these novel approaches, eventually combined with current standard chemotherapy, is therefore expected in a near future in T-ALL.

Bortezomib is significantly beneficial for de novo pediatric AML patients with low phosphorylation of the NF-κB subunit RelA

PURPOSE

The addition of the proteasome inhibitor (PI) bortezomib to standard chemotherapy (ADE: cytarabine [Ara-C], daunorubicin, and etoposide) did not improve overall outcome of pediatric AML patients in the Children's Oncology Group AAML1031 phase 3 randomized clinical trial (AAML1031) . Bortezomib prevents protein degradation, including RelA via the intracellular NF-kB pathway. In this study, we hypothesized that subgroups of pediatric AML patients benefitting from standard therapy plus bortezomib (ADEB) could be identified based on pre-treatment RelA expression and phosphorylation status.

EXPERIMENTAL DESIGN

RelA-total and phosphorylation at serine 536 (RelA-pSer⁵³⁶ ) were measured in 483 patient samples using reverse phase protein array technology.

RESULTS

In ADEB-treated patients, low-RelA-pSer⁵³⁶ was favorably prognostic when compared to high-RelA-pSer⁵³⁶ (3-yr overall survival (OS): 81% vs. 68%, p = 0.032; relapse risk (RR): 30% vs. 49%, p = 0.004). Among low-RelA-pSer⁵³⁶ patients, RR significantly decreased with ADEB compared to ADE (RR: 30% vs. 44%, p = 0.035). Correlation between RelA-pSer⁵³⁶ and 295 other assayed proteins identified a strong correlation with HSF1-pSer³²⁶ , another protein previously identified as modifying ADEB response. The combination of low-RelA-pSer⁵³⁶ and low-HSF1-pSer³²⁶ was a significant predictor of ADEB response (3-yr OS: 86% vs. 67%, p = 0.013).

CONCLUSION AND CLINICAL RELEVANCE

Bortezomib may improve clinical outcome in a subgroup of AML patients identified by low-RelA-pSer⁵³⁶ and low-HSF1-pSer³²⁶ .

Gastric cancer-derived exosomal miR-135b-5p impairs the function of Vγ9Vδ2 T cells by targeting specificity protein 1

Recent studies have shown that tumor-derived exosomes participate in the communication between tumor cells and their microenvironment and mediate malignant biological behaviors including immune escape. In this study, we found that gastric cancer (GC) cell-derived exosomes could be effectively uptaken by Vγ9Vδ2 T cells, decrease the cell viability of Vγ9Vδ2 T cells, induce apoptosis, and reduce the production of cytotoxic cytokines IFN-γ and TNF-α. Furthermore, we demonstrated that exosomal miR-135b-5p was delivered into Vγ9Vδ2 T cells. Exosomal miR-135b-5p impaired the function of Vγ9Vδ2 T cells by targeting specificity protein 1 (SP1). More importantly, blocking the SP1 function by Plicamycin, an SP1 inhibitor, abolished the effect of stable miR-135b-5p knockdown GC cell-derived exosomes on Vγ9Vδ2 T cell function. Collectively, our results suggest that GC cell-derived exosomes impair the function of Vγ9Vδ2 T cells via miR-135b-5p/SP1 pathway, and targeting exosomal miR-135b-5p/SP1 axis may improve the efficiency of GC immunotherapy based on Vγ9Vδ2 T cells.

The Role of Proteasome Inhibitors in Treating Acute Lymphoblastic Leukaemia

Acute lymphoblastic leukaemia (ALL) is an aggressive haematolymphoid malignancy. The prognosis of ALL is excellent in paediatric population, however the outcome of relapse/refractory disease is dismal. Adult ALL has less favourable prognosis and relapse/refractory disease is not uncommonly encountered. Bortezomib is the first generation proteasome inhibitor licensed to treat plasma cell myeloma and mantle cell lymphoma with favourable side effect profile. Efficacy of bortezomib had been proven in other solid tumors. Clinical studies showed promising response for proteasome inhibitors in treating relapse/refractory ALL. Thus, proteasome inhibitors are attractive alternative agents for research in treating ALL. In the review article, we will introduce different proteasome inhibitors and their difference in pharmacological properties. Moreover, the mechanism of action of proteasome inhibitors on ALL will be highlighted. Finally, results of various clinical studies on proteasome inhibitors in both paediatric and adult ALL will be discussed. This review article provides the insights on the use of proteasome inhibitors in treating ALL with a summary of mechanism of action in ALL which facilitates future research on its use to improve the outcome of ALL.

Targeting Notch to Maximize Chemotherapeutic Benefits: Rationale, Advanced Strategies, and Future Perspectives

Simple Summary

The Notch signaling pathway regulates cell proliferation, apoptosis, stem cell self-renewal, and differentiation in a context-dependent fashion both during embryonic development and in adult tissue homeostasis. Consistent with its pleiotropic physiological role, unproper activation of the signaling promotes or counteracts tumor pathogenesis and therapy response in distinct tissues. In the last twenty years, a wide number of studies have highlighted the anti-cancer potential of Notch-modulating agents as single treatment and in combination with the existent therapies. However, most of these strategies have failed in the clinical exploration due to dose-limiting toxicity and low efficacy, encouraging the development of novel agents and the design of more appropriate combinations between Notch signaling inhibitors and chemotherapeutic drugs with improved safety and effectiveness for distinct types of cancer.

Abstract

Notch signaling guides cell fate decisions by affecting proliferation, apoptosis, stem cell self-renewal, and differentiation depending on cell and tissue context. Given its multifaceted function during tissue development, both overactivation and loss of Notch signaling have been linked to tumorigenesis in ways that are either oncogenic or oncosuppressive, but always context-dependent. Notch signaling is critical for several mechanisms of chemoresistance including cancer stem cell maintenance, epithelial-mesenchymal transition, tumor-stroma interaction, and malignant neovascularization that makes its targeting an appealing strategy against tumor growth and recurrence. During the last decades, numerous Notch-interfering agents have been developed, and the abundant preclinical evidence has been transformed in orphan drug approval for few rare diseases. However, the majority of Notch-dependent malignancies remain untargeted, even if the application of Notch inhibitors alone or in combination with common chemotherapeutic drugs is being evaluated in clinical trials. The modest clinical success of current Notch-targeting strategies is mostly due to their limited efficacy and severe on-target toxicity in Notch-controlled healthy tissues. Here, we review the available preclinical and clinical evidence on combinatorial treatment between different Notch signaling inhibitors and existent chemotherapeutic drugs, providing a comprehensive picture of molecular mechanisms explaining the potential or lacking success of these combinations.

NOTCH signaling in the pathogenesis of splenic marginal zone lymphoma-opportunities for therapy

NOTCH signaling is a highly conserved pathway mediated by four receptors (NOTCH 1-4) playing critical functions in proliferation, differentiation, and cell death. Under physiologic circumstances, NOTCH2 is a key regulator in marginal zone differentiation and development. Over the last decade, growing data demonstrated frequent NOTCH2 mutations in splenic marginal zone lymphoma (SMZL) underscoring its critical role in the pathogenesis of this disease. Moreover, NOTCH2 specificity across studies supports the rationale to assess its value as a diagnosis biomarker in a disease without pathognomonic features. These data make NOTCH signaling an appealing target for drug discovery in SMZL; however, prior efforts attempting to manipulate this pathway failed to demonstrate meaningful clinical benefit, or their safety profile prevented further development. In this review, we discuss the current knowledge of NOTCH implications in the pathogenesis and as a potential druggable target in SMZL.

Current and emerging therapeutic approaches for T-cell acute lymphoblastic leukaemia

T-cell ALL (T-ALL) is an aggressive malignancy of T-cell progenitors. Although survival outcomes in T-ALL have greatly improved over the past 50 years, relapsed and refractory cases remain extremely challenging to treat and those who cannot tolerate intensive treatment continue to have poor outcomes. Furthermore, T-ALL has proven a more challenging immunotherapeutic target than B-ALL. In this review we explore our expanding knowledge of the basic biology of T-ALL and how this is paving the way for repurposing established treatments and the development of novel therapeutic approaches.

Ciclopirox and bortezomib synergistically inhibits glioblastoma multiforme growth via simultaneously enhancing JNK/p38 MAPK and NF-κB signaling

Ciclopirox (CPX) is an antifungal drug that has recently been reported to act as a potential anticancer drug. However, the effects and underlying molecular mechanisms of CPX on glioblastoma multiforme (GBM) remain unknown. Bortezomib (BTZ) is the first proteasome inhibitor-based anticancer drug approved to treat multiple myeloma and mantle cell lymphoma, as BTZ exhibits toxic effects on diverse tumor cells. Herein, we show that CPX displays strong anti-tumorigenic activity on GBM. Mechanistically, CPX inhibits GBM cellular migration and invasion by reducing N-Cadherin, MMP9 and Snail expression. Further analysis revealed that CPX suppresses the expression of several key subunits of mitochondrial enzyme complex, thus leading to the disruption of mitochondrial oxidative phosphorylation (OXPHOS) in GBM cells. In combination with BTZ, CPX promotes apoptosis in GBM cells through the induction of reactive oxygen species (ROS)-mediated c-Jun N-terminal kinase (JNK)/p38 mitogen-activated protein kinase (MAPK) signaling. Moreover, CPX and BTZ synergistically activates nuclear factor kappa B (NF-κB) signaling and induces cellular senescence. Our findings suggest that a combination of CPX and BTZ may serve as a novel therapeutic strategy to enhance the anticancer activity of CPX against GBM.

High-Risk Mantle Cell Lymphoma in the Era of Novel Agents

PURPOSE OF REVIEW

Mantle cell lymphoma (MCL) is a heterogenous disease with a variety of morphologic and genetic features, some of which are associated with high risk disease. Here we critically analyze the current state of the understanding of MCL's biology and its implications in therapy, with a focus on chemotherapy-free and targeted therapy regimens.

RECENT FINDINGS

Mantle cell lymphoma (MCL) is a rare subtype of non-Hodgkin's lymphoma, defined by a hallmark chromosomal translocation t(11;14) which leads to constitutive expression of cyclin D1. Recent discoveries in the biology of MCL have identified a number of factors, including TP53 mutations and complex karyotype, that lead to unresponsiveness to traditional chemoimmunotherapy and poor outcomes. Bruton tyrosine kinase inhibitors, BH3-mimetics and other novel agents thwart survival of the neoplastic B-cells in a manner independent of high-risk mutations and have shown promising activity in relapsed/refractory MCL. These therapies are being investigated in the frontline setting, while optimal responses to chemotherapy-free regimens, particularly in high-risk disease, might require combination approaches. High-risk MCL does not respond well to chemoimmunotherapy. Targeted agents are highly active in the relapsed refractory setting and show promise in high-risk disease. Novel approaches may soon replace the current standard of care in both relapsed and frontline settings.

Advances of target therapy on NOTCH1 signaling pathway in T-cell acute lymphoblastic leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is one of the hematological malignancies. With the applications of chemotherapy regimens and allogeneic hematopoietic stem cell transplantation, the cure rate of T-ALL has been significantly improved. However, patients with relapsed and refractory T-ALL still lack effective treatment options. Gene mutations play an important role in T-ALL. The NOTCH1 gene mutation is the important one among these genetic mutations. Since the mutation of NOTCH1 gene is considered as a driving oncogene in T-ALL, targeting the NOTCH1 signaling patheway may be an effective option to overcome relapsed and refractory T-ALL. This review mainly summarizes the recent research advances of targeting on NOTCH1 signaling pathway in T-ALL.

Notch1 in Cancer Therapy: Possible Clinical Implications and Challenges

The Notch family consists of four highly conserved transmembrane receptors. The release of the active intracellular domain requires the enzymatic activity of γ-secretase. Notch is involved in embryonic development and in many physiologic processes of normal cells, in which it regulates growth, apoptosis, and differentiation. Notch1, a member of the Notch family, is implicated in many types of cancer, including breast cancer (especially triple-negative breast cancer), leukemias, brain tumors, and many others. Notch1 is tightly connected to many signaling pathways that are therapeutically involved in tumorigenesis. Together, they impact apoptosis, proliferation, chemosensitivity, immune response, and the population of cancer stem cells. Notch1 inhibition can be achieved through various and diverse methods, the most common of which are the γ-secretase inhibitors, which produce a pan-Notch inhibition, or the use of Notch1 short interference RNA or Notch1 monoclonal antibodies, which produce a more specific blockade. Downregulation of Notch1 can be used alone or in combination with chemotherapy, which can achieve a synergistic effect and a decrease in chemoresistance. Targeting Notch1 in cancers that harbor high expression levels of Notch1 offers an addition to therapeutic strategies recruited for managing cancer. Considering available evidence, Notch1 offers a legitimate target that might be incorporated in future strategies for combating cancer. In this review, the possible clinical applications of Notch1 inhibition and the obstacles that hinder its clinical application are discussed. SIGNIFICANCE STATEMENT: Notch1 plays an important role in different types of cancer. Numerous approaches of Notch1 inhibition possess potential benefits in the management of various clinical aspects of cancer. The application of different Notch1 inhibition modalities faces many challenges.

Upregulated expression and function of the α4β1 integrin in multiple myeloma cells resistant to bortezomib

The interaction of multiple myeloma (MM) cells with the bone marrow (BM) microenvironment promotes MM cell retention, survival, and resistance to different anti-MM agents, including proteasome inhibitors (PIs) such as bortezomib (BTZ). The α4β1 integrin is a main adhesion receptor mediating MM cell-stroma interactions and MM cell survival, and its expression and function are downregulated by BTZ, leading to inhibition of cell adhesion-mediated drug resistance (CAM-DR) and MM cell apoptosis. Whether decreased α4β1 expression and activity are maintained or recovered upon development of resistance to BTZ represents an important question, as a potential rescue of α4β1 function could boost MM cell survival and disease progression. Using BTZ-resistant MM cells, we found that they not only rescue their α4β1 expression, but its levels were higher than in parental cells. Increased α4β1 expression in resistant cells correlated with enhanced α4β1-mediated cell lodging in the BM, and with disease progression. BTZ-resistant MM cells displayed enhanced NF-κB pathway activation relative to parental counterparts, which contributed to upregulated α4 expression and to α4β1-dependent MM cell adhesion. These data emphasize the upregulation of α4β1 expression and function as a key event during resistance to BTZ in MM, which might indirectly contribute to stabilize this resistance, as stronger MM cell attachment to BM stroma will regain CAM-DR and MM cell growth and survival. Finally, we found a strong correlation between high ITGB1 (integrin β1) expression in MM and poor progression-free survival (PFS) and overall survival (OS) during treatment of MM patients with BTZ and IMIDs, and combination of high ITGB1 levels and presence of the high-risk genetic factor amp1q causes low PFS and OS. These results unravel a novel prognostic value for ITGB1 in myeloma. © 2020 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Biology and Treatment Paradigms in T Cell Acute Lymphoblastic Leukemia in Older Adolescents and Adults

OPINION STATEMENT

T cell acute lymphoblastic leukemia (T-ALL) occurs in approximately 25-30% of adult ALL diagnoses. Historically, B cell ALL (B-ALL) and T-ALL have been treated in the same fashion despite differences in the biology of disease. Outcomes in the adolescent/young adult (AYA) population have improved significantly with the utilization of pediatric-based regimens. In addition, there may now be a role for the addition of nelarabine to frontline treatment in the AYA population. In older adults, choices in which regimen to pursue should account for the potential toxicities associated with pediatric-based regimens. Measurable residual disease (MRD) has taken on increasing prognostic value in T-ALL and may help to identify which patients should receive an allogeneic stem cell transplant. T cell lymphoblastic lymphoma (T-LBL) has traditionally been treated similarly to T-ALL, but additional management questions must be considered. Mediastinal irradiation does not seem to clearly improve outcomes, and there is considerable heterogeneity in the central nervous system (CNS) prophylaxis strategy used in prospective trials. CNS prophylaxis in AYA patients with T-ALL, on the other hand, can be safely achieved with intrathecal chemotherapy alone. Prospective data regarding CNS prophylaxis strategies in older adults are currently not available. Nelarabine-based regimens currently remain the standard in relapsed/refractory T-ALL; however, novel therapies targeting molecular aberrations in T-ALL are actively being investigated.

Posttranslational Regulation of the Exon Skipping Machinery Controls Aberrant Splicing in Leukemia

Splicing alterations are common in diseases such as cancer, where mutations in splicing factor genes are frequently responsible for aberrant splicing. Here we present an alternative mechanism for splicing regulation in T-cell acute lymphoblastic leukemia (T-ALL) that involves posttranslational stabilization of the splicing machinery via deubiquitination. We demonstrate there are extensive exon skipping changes in disease, affecting proteasomal subunits, cell-cycle regulators, and the RNA machinery. We present that the serine/arginine-rich splicing factors (SRSF), controlling exon skipping, are critical for leukemia cell survival. The ubiquitin-specific peptidase 7 (USP7) regulates SRSF6 protein levels via active deubiquitination, and USP7 inhibition alters the exon skipping pattern and blocks T-ALL growth. The splicing inhibitor H3B-8800 affects splicing of proteasomal transcripts and proteasome activity and acts synergistically with proteasome inhibitors in inhibiting T-ALL growth. Our study provides the proof-of-principle for regulation of splicing factors via deubiquitination and suggests new therapeutic modalities in T-ALL. SIGNIFICANCE: Our study provides a new proof-of-principle for posttranslational regulation of splicing factors independently of mutations in aggressive T-cell leukemia. It further suggests a new drug combination of splicing and proteasomal inhibitors, a concept that might apply to other diseases with or without mutations affecting the splicing machinery.This article is highlighted in the In This Issue feature, p. 1241.

Differential antitumor activity of compounds targeting the ubiquitin-proteasome machinery in gastrointestinal stromal tumor (GIST) cells

The majority of gastrointestinal stromal tumors (GISTs) are driven by oncogenic KIT signaling and can therefore be effectively treated with the tyrosine kinase inhibitor (TKI) imatinib mesylate. However, most GISTs develop imatinib resistance through secondary KIT mutations. The type of resistance mutation determines sensitivity to approved second-/third-line TKIs but shows high inter- and intratumoral heterogeneity. Therefore, therapeutic strategies that target KIT independently of the mutational status are intriguing. Inhibiting the ubiquitin-proteasome machinery with bortezomib is effective in GIST cells through a dual mechanism of KIT transcriptional downregulation and upregulation of the pro-apoptotic histone H2AX but clinically problematic due to the drug’s adverse effects. We therefore tested second-generation inhibitors of the 20S proteasome (delanzomib, carfilzomib and ixazomib) with better pharmacologic profiles as well as compounds targeting regulators of ubiquitination (b-AP15, MLN4924) for their effectiveness and mechanism of action in GIST. All three 20S proteasome inhibitors were highly effective in vitro and in vivo, including in imatinib-resistant models. In contrast, b-AP15 and MLN4924 were only effective at high concentrations or had mostly cytostatic effects, respectively. Our results confirm 20S proteasome inhibitors as promising strategy to overcome TKI resistance in GIST, while highlighting the complexity of the ubiquitin-proteasome machinery as a therapeutic target.

Therapeutic Targeting of Notch Signaling Pathway in Hematological Malignancies

The Notch pathway plays a key role in several processes, including stem-cell self-renewal, proliferation, and cell differentiation. Several studies identified recurrent mutations in hematological malignancies making Notch one of the most desirable targets in leukemia and lymphoma. The Notch signaling mediates resistance to therapy and controls cancer stem cells supporting the development of on-target therapeutic strategies to improve patients’ outcome. In this brief review, we outline the therapeutic potential of targeting Notch pathway in T-cell acute jlymphoblastic leukemia, chronic lymphocytic leukemia, and mantle cell lymphoma.

Strategies to Overcome Resistance Mechanisms in T-Cell Acute Lymphoblastic Leukemia

Chemoresistance is a major cause of recurrence and death from T-cell acute lymphoblastic leukemia (T-ALL), both in adult and pediatric patients. In the majority of cases, drug-resistant disease is treated by selecting a combination of other drugs, without understanding the molecular mechanisms by which malignant cells escape chemotherapeutic treatments, even though a more detailed genomic characterization and the identification of actionable disease targets may enable informed decision of new agents to improve patient outcomes. In this work, we describe pathways of resistance to common chemotherapeutic agents including glucocorticoids and review the resistance mechanisms to targeted therapy such as IL7R, PI3K-AKT-mTOR, NOTCH1, BRD4/MYC, Cyclin D3: CDK4/CDK6, BCL2 inhibitors, and selective inhibitors of nuclear export (SINE). Finally, to overcome the limitations of the current trial-and-error method, we summarize the experiences of anti-cancer drug sensitivity resistance profiling (DSRP) approaches as a rapid and relevant strategy to infer drug activity and provide functional information to assist clinical decision one patient at a time.

CRLF2 expression associates with ICN1 stabilization in T-cell acute lymphoblastic leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematopoietic malignancy with few molecular alterations showing a consensual prognostic value. CRLF2 overexpression was recently identified in high-risk T-ALL patients. For these cases, no genomic abnormality was found to be associated with CRLF2 overexpression. IKZF1 has been recently shown to be a direct transcriptional regulator of CRLF2 expression. Moreover, it is known that NOTCH1 antagonizes IKZF1 in T-ALL. In light of these pieces of evidence, we reasoned that IKZF1 binding perturbation and CRLF2 upregulation could be associated in T-ALL. We evaluated two independent series of pediatric T-ALL cases (PHOP, n = 57 and TARGET, n = 264) for the presence of common T-ALL molecular abnormalities, such as NOTCH1/FBXW7 mutations. We also assessed CRLF2 and IKZF1 gene expression. CRLF2 overexpression was observed in 14% (PHOP) and 16% (TARGET) of T-ALL patients. No correlation was found between mRNA expression of CRLF2 and IKZF1 in both cohorts. Interestingly, we show that patients with mutations affecting NOTCH1-PEST domain and/or FBXW7 had higher CRLF2 expression (P = .04). In summary, we demonstrate for the first time that only mutations resulting in ICN1 (intracellular domain of NOTCH1) stabilization are associated with CRLF2 overexpression.

Eradication of Central Nervous System Leukemia of T-Cell Origin with a Brain-Permeable LSD1 Inhibitor

PURPOSE

Lysine-specific demethylase 1 (LSD1) regulates several biological processes via the bifunctional modulation of enhancer functions. Recently, we reported that LSD1 overexpression is a founder abnormality of T-cell leukemogenesis and is maintained in fully transformed T-cell acute lymphoblastic leukemia (T-ALL) cells. On the basis of this finding, we attempted to develop novel LSD1 inhibitors effective for T-ALL with central nervous system (CNS) involvement.

EXPERIMENTAL DESIGN

We chemically modified the prototype LSD inhibitor tranylcypromine (TCP) and screened for cytotoxicity against TCP-resistant T-ALL cell lines. In vivo efficacy of novel LSD1 inhibitors was examined in immunodeficient mice transplanted with luciferase-expressing T-ALL cell lines, which faithfully reproduce human T-ALL with CNS involvement.

RESULTS

We found robust cytotoxicity against T-ALL cells, but not normal bone marrow progenitors, for two N-alkylated TCP derivatives, S2116 and S2157. The two compounds induced apoptosis in TCP-resistant T-ALL cells in vitro and in vivo by repressing transcription of the NOTCH3 and TAL1 genes through increased H3K9 methylation and reciprocal H3K27 deacetylation at superenhancer regions. Both S2116 and S2157 significantly retarded the growth of T-ALL cells in xenotransplanted mice and prolonged the survival of recipients as monotherapy and in combination with dexamethasone. Notably, S2157 could almost completely eradicate CNS leukemia because of its ability to efficiently pass through the blood-brain barrier.

CONCLUSIONS

These findings provide a molecular basis and rationale for the inclusion of a brain-permeable LSD1 inhibitor, S2157, in treatment strategies for T-ALL with CNS involvement.

USP7 deubiquitinates and stabilizes NOTCH1 in T-cell acute lymphoblastic leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is a highly aggressive leukemia that is primarily caused by aberrant activation of the NOTCH1 signaling pathway. Recent studies have revealed that posttranslational modifications, such as ubiquitination, regulate NOTCH1 stability, activity, and localization. However, the specific deubiquitinase that affects NOTCH1 protein stability remains unestablished. Here, we report that ubiquitin-specific protease 7 (USP7) can stabilize NOTCH1. USP7 deubiquitinated NOTCH1 in vivo and in vitro, whereas knockdown of USP7 increased the ubiquitination of NOTCH1. USP7 interacted with NOTCH1 protein in T-ALL cells, and the MATH and UBL domains of USP7 were responsible for this interaction. Depletion of USP7 significantly suppressed the proliferation of T-ALL cells in vitro and in vivo, accompanied by downregulation of the NOTCH1 protein level. Similarly, pharmacologic inhibition of USP7 led to apoptosis of T-ALL cells. More importantly, we found that USP7 was significantly upregulated in human T-ALL cell lines and patient samples, and a USP7 inhibitor exhibited cell cytotoxicity toward primary T-ALL cells, indicating the clinical relevance of these findings. Overall, our results demonstrate that USP7 is a novel deubiquitinase that stabilizes NOTCH1. Therefore, USP7 may be a promising therapeutic target in the currently incurable T-ALL.

Inhibiting the protein ubiquitin-specific protease 7 (USP-7) may offer a treatment option for patients with T-cell acute lymphoblastic leukemia (T-ALL), an incurable and aggressive cancer. T-ALL is primarily caused by aberrant activation of the protein NOTCH1, which regulates gene expression relating to cell survival, proliferation, and metastasis. Ying-Li Wu, from China’s Shanghai Jiao Tong University School of Medicine, and a team of researchers report that, in their experiments, USP-7 prevented the breakdown of NOTCH1 by removing the protein tag that would normally signal it for degradation. In addition, USP-7 expression was upregulated in all human T-ALL cells and samples tested. Inhibition of USP-7 suppressed the proliferation of T-ALL cells in vitro and in vivo. These results reveal the role of USP-7 in the pathophysiology of T-ALL and offer USP-7 as a promising potential therapeutic target.

A Bortezomib-Based Protocol Induces a High Rate of Complete Remission with Minor Toxicity in Adult Patients with Relapsed/Refractory Acute Lymphoblastic Leukemia

The treatment of relapsed/refractory acute lymphoblastic leukemia (RR-ALL) presents a true clinical challenge. In 2012, a protocol combining bortezomib, dexamethasone, asparaginase, doxorubicin, and vincristine administered to children with RR-ALL was published with encouraging results. Over the past 5 years, we have implemented this protocol in the adult RR-ALL population (> 18 years) and addressed its feasibility in terms of remission rate and toxicity. Here, we present the results of our experience in 9 patients, all of whom received multiple previous chemotherapy protocols, two of them relapsing after an allogeneic bone marrow transplantation. All of the five B-ALL patients, and two of the four T-ALL achieved complete remission. Of the seven patients achieving complete remission, two patients were referred for allogeneic bone marrow transplantation, two patients were subsequently given blinatumomab, and one patient subsequently received donor lymphocyte infusion followed by blinatumomab. Thus, five out of nine patients treated (55%) were able to proceed to best available therapy in a complete remission. We observed minimal adverse effects, mainly hematological toxicity. We conclude that the bortezomib-based protocol should be evaluated as an effective and well-tolerated treatment option for adult patients either unfit for or failing standard salvage chemotherapy, as a bridge to immunotherapy or allogeneic bone marrow transplantation.

DCZ3301, a novel aryl-guanidino inhibitor, induces cell apoptosis and cell cycle arrest via suppressing the PI3K/AKT pathway in T-cell leukemia/lymphoma

DCZ3301, a novel aryl-guanidino compound, was previously found to have potent anti-tumor activity in myeloma and B-cell lymphoma. In the present study, we investigated the effects of DCZ3301 on T-cell leukemia/lymphoma cells both in vitro and in vivo via cell proliferation, cell cycle analysis, apoptosis assay, mitochondrial membrane potential (MMP) assay, western blot analysis and tumor xenograft models. We found that DCZ3301 inhibited the viability of T-cell leukemia/lymphoma cells in a dose- and time-dependent manner. DCZ3301-induced G2/M cell cycle arrest, associated with downregulation of CDK1, cyclin B1, and cdc25C. DCZ3301 also induced cell apoptosis by decreasing MMP in T-cell leukemia/lymphoma cells, but had no significant pro-apoptotic effect on normal peripheral blood mononuclear cells (PBMCs). In addition, DCZ3301-induced apoptosis may be mediated by the caspase-dependent pathway and suppressing the phosphoinositide 3-kinase (PI3K)/AKT pathway. Finally, we showed that DCZ3301 treatment effectively inhibited tumor growth, with no significant side effects, in xenograft mouse models. In conclusion, these results suggest that DCZ3301 may be regarded as a new therapeutic strategy for T-cell leukemia/lymphoma patients.

ETS1 and SP1 drive DHX15 expression in acute lymphoblastic leukaemia

DHX15 plays a role in leukaemogenesis and leukaemia relapse. However, the mechanism underlying the transcriptional regulation of DHX15 in ALL has not been elucidated. Our present study aimed to explore the functional promoter region of DHX15 and to investigate the transcription factors controlling the transcription of this gene. A luciferase assay performed with several truncated constructs identified a 501-bp region as the core promoter region of DHX15. Site-directed mutagenesis, electrophoretic mobility shift and chromatin immunoprecipitation assays showed that ETS1 and SP1 occupied the DHX15 promoter. Furthermore, knockdown of ETS1 and SP1 resulted in suppression of DHX15, whereas the overexpression of these genes led to up-regulation of DHX15. Interestingly, in samples obtained from patients with ALL at diagnosis, both ETS1 and SP1 correlated positively with DHX15 expression. Additionally, differences in methylation of the DHX15 core promoter region were not observed between the patients and controls. In conclusion, we identified the core promoter region of DHX15 and demonstrated that ETS1 and SP1 regulated DHX15 expression in ALL.

CXCR4-mediated signaling regulates autophagy and influences acute myeloid leukemia cell survival and drug resistance

CXCR4 surface expression is considered an independent prognostic factor for disease relapse and survival in acute myeloid leukemia (AML) patients. Herein, we investigated targetable autophagy-related mechanisms of CXCR4 for AML therapy. Our experiments show that activation of CXCR4 signaling in AML cells increases autophagic activity and decreases cytarabine-induced apoptosis. Accordingly, combined use of autophagy inhibitors significantly increased the sensitivity of AML cells to cytarabine in vitro and in vivo. Moreover, expression of autophagy-related protein SIRT1 was correlated with SDF-1α-CXCR4 signaling, which interacts with autophagy proteins, such as ATG5 and LC3. Furthermore, in primary human AML samples, high CXCR4 expression was associated with elevated expression levels of SIRT1 and other autophagy-related proteins. Collectively, our data suggest new roles of SDF-1α-CXCR4 signaling on autophagy induction in AML cells, which further promoted their survival under stress. Targeting the SDF-1α-CXCR4-autophagy signaling may contribute to an enhanced efficacy of active treatments.

Therapeutic potential and functional interaction of carfilzomib and vorinostat in T-cell leukemia/lymphoma

We previously showed that the proteasome inhibitor carfilzomib and the histone deacetylase inhibitor (HDACI) vorinostat cooperated to induce cell apoptosis in one T-cell leukemia cell line in vitro, implying the possibility of the combination treatment of carfilzomib and vorinostat as a potential therapeutic strategy in human T-cell leukemia/lymphoma. Here we report that combination treatment of carfilzomib and vorinostat enhanced cell apoptosis and induced a marked increase in G2-M arrest, reactive oxygen species (ROS) generation, and activated the members of mitogen-activated protein kinases (MAPK) family, including the stress-activated kinases JNK, p38MAPK, and ERK1/2. Carfilzomib/vorinostat-mediated apoptosis was blocked by the ROS scavenger N-acetylcysteine (NAC). The JNK inhibitor SP600125 and the p38MAPK inhibitor SB203580 but not the MEK1/2 inhibitor U0126 significantly attenuated carfilzomib/vorinostat-induced apoptosis, suggesting that p38MAPK and JNK activation contribute to carfilzomib and vorinostat-induced apoptosis. This was further confirmed via short hairpin (shRNA) RNA knockdown of p38MAPK and JNK. Interestingly, the ROS scavenger NAC attenuated carfilzomib/vorinostat-mediated activation of p38MAPK and JNK. However, p38MAPK shRNA but not JNK shRNA diminished carfilzomib/vorinostat-mediated ROS generation. In contrast, overexpression of p38MAPK significantly increased carfilzomib/vorinostat-mediated ROS generation, suggesting that an amplification loop exists between ROS and p38MAPK pathway. Combination treatment of carfilzomib and vorinostat enhanced their individual antitumor activity in both a human xenograft model as well as human primary T-cell leukemia/lymphoma cells. These data suggest the potential clinical benefit and underlying molecular mechanism of combining carfilzomib with vorinostat in the treatment of human T-cell leukemia/lymphoma.

Lysine-specific demethylase 1 inhibitors prevent teratoma development from human induced pluripotent stem cells

Human induced pluripotent stem cells (hiPSCs) are creating great expectations for regenerative medicine. However, safety strategies must be put in place to guard against teratoma formation after transplantation of hiPSC-derived cells into patients. Recent studies indicate that epigenetic regulators act at the initial step of tumorigenesis. Using gain-of-function and loss-of-function approaches, we show here that the expression and function of lysine-specific demethylase 1 (LSD1) are tightly regulated in hiPSCs, and their deregulation underlies the development of teratomas. Consistent with these results, we demonstrate that an LSD1 inhibitor, S2157, prevented teratoma formation from hiPSCs transplanted into immunodeficient mice. This novel action of LSD1 and the effects of its inhibition potentially allow for the development of new clinical applications and therapeutic strategies using hiPSCs.

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.

Combination of bortezomib and daunorubicin in the induction of apoptosis in T-cell acute lymphoblastic leukemia

Despite advances in the treatment of T‑cell acute lymphoblastic leukemia (T‑ALL), the outcome of T‑ALL treatment remains unsatisfactory, therefore, more effective treatment is urgently required. The present study examined the cytotoxicities of bortezomib in combination with daunorubicin against human Jurkat and Molt‑4 T‑ALL cells and primary T‑ALL cells. Compared with treatment alone, co‑exposure of cells to bortezomib and daunorubicin resulted in a significant increase in cell death in the Jurkat cells, as evidenced by the increased percentage of Annexin V‑positive cells, the formation of apoptotic bodies. In addition, the administration sequence of bortezomib and daunorubicin had an effect on cell viability. Treatment with bortezomib followed by daunorubicin treatment was more effective, compared with treatment with daunorubicin followed by bortezomib. Co-treatment with bortezomib and daunorubicin markedly enhanced the activation of caspase‑3, ‑8 and ‑9, which was reversed by the pan‑caspase inhibitor, Z‑VAD‑FMK. In addition, cotreatment with bortezomib and daunorubicin enhanced the collapse of mitochondrial transmembrane potential and upregulated the proapoptotic protein, B‑cell lymphoma 2 (Bcl‑2)‑interacting mediator of cell death (Bim), but not Bcl‑2 or Bcl‑extra large. Consistent with this, it was demonstrated that cotreatment of bortezomib and daunorubicin efficiently induced apoptosis in primary T‑ALL cells, and cell death was associated with the collapse of mitochondrial transmembrane potential and the upregulation of Bim. Taken together, these findings indicated that the combination of bortezomib and daunorubicin significantly enhanced their apoptosis‑inducing effect in T‑ALL cells, which may warrant further investigation in preclinical and clinical investigations.

Identification of a tumor suppressor network in T-cell leukemia

To identify novel cancer-related genes targeted by copy number alterations, we performed genomic profiling of T-cell acute lymphoblastic leukemia (T-ALL) cell lines. In 3/8, we identified a shared deletion at chromosomal position 2p16.3-p21. Within the minimally deleted region, we recognized several candidate tumor suppressor (TS) genes, including FBXO11 and FOXN2. An additional deletion at chromosome 14q23.2-q32.11 included FOXN3, highlighting this class of FOX genes as potential TS. Quantitative expression analyses of FBXO11, FOXN2, and FOXN3 confirmed reduced transcript levels in the identified cell lines. Moreover, reduced expression of these genes was also observed in about 7% of T-ALL patients, showing their clinical relevance in this malignancy. Bioinformatic analyses revealed concurrent reduction of FOXN2 and/or FOXN3 together with homeobox gene ZHX1. Consistently, experiments demonstrated that both FOXN2 and FOXN3 directly activated transcription of ZHX1. Taken together, we identified novel TS genes forming a regulatory network in T-cell development and leukemogenesis.

The combination of bortezomib with chemotherapy to treat relapsed/refractory acute lymphoblastic leukaemia of childhood

Achieving complete remission (CR) in childhood relapsed/refractory acute lymphoblastic leukaemia (ALL) is a difficult task. Bortezomib, a proteasome inhibitor, has in vitro activity against ALL blasts. A phase I-II trial, reported by the Therapeutic Advances in Childhood Leukaemia and Lymphoma (TACL) consortium, demonstrated that bortezomib with chemotherapy has acceptable toxicity and remarkable activity in patients with relapsed ALL failing 2-3 previous regimens. We evaluated bortezomib in combination with chemotherapy in 30 and 7 children with B-cell precursor (BCP) and T-cell ALL, respectively. Bortezomib (1·3 mg/m² /dose) was administered intravenously on days 1, 4, 8, and 11. Chemotherapy agents were the same as those used in the TACL trial, consisting of dexamethasone, doxorubicin, vincristine and pegylated asparaginase. Three patients (8·1%) died due to infections. Twenty-seven patients (72·9%) achieved CR or CR with incomplete platelet recovery (CRp). Fourteen had minimal residual disease (MRD) lower than 0·1%. Twenty-two of 30 BCP-ALL patients (73·3%) and 5/7 patients (71%) with T-cell ALL achieved CR/CRp. The 2-year overall survival (OS) is 31·3%; CR/CRp patients with an MRD response had a remarkable 2-year OS of 68·4%. These data confirm that the combination of bortezomib with chemotherapy is a suitable/effective option for childhood relapsed/refractory ALL.

Synergistic cytotoxic effects of bortezomib and CK2 inhibitor CX-4945 in acute lymphoblastic leukemia: turning off the prosurvival ER chaperone BIP/Grp78 and turning on the pro-apoptotic NF-κB

The proteasome inhibitor bortezomib is a new targeted treatment option for refractory or relapsed acute lymphoblastic leukemia (ALL) patients. However, a limited efficacy of bortezomib alone has been reported. A terminal pro-apoptotic endoplasmic reticulum (ER) stress/unfolded protein response (UPR) is one of the several mechanisms of bortezomib-induced apoptosis. Recently, it has been documented that UPR disruption could be considered a selective anti-leukemia therapy. CX-4945, a potent casein kinase (CK) 2 inhibitor, has been found to induce apoptotic cell death in T-ALL preclinical models, via perturbation of ER/UPR pathway. In this study, we analyzed in T- and B-ALL preclinical settings, the molecular mechanisms of synergistic apoptotic effects observed after bortezomib/CX-4945 combined treatment. We demonstrated that, adding CX-4945 after bortezomib treatment, prevented leukemic cells from engaging a functional UPR in order to buffer the bortezomib-mediated proteotoxic stress in ER lumen. We documented that the combined treatment decreased pro-survival ER chaperon BIP/Grp78 expression, via reduction of chaperoning activity of Hsp90. Bortezomib/CX-4945 treatment inhibited NF-κB signaling in T-ALL cell lines and primary cells from T-ALL patients, but, intriguingly, in B-ALL cells the drug combination activated NF-κB p65 pro-apoptotic functions. In fact in B-cells, the combined treatment induced p65-HDAC1 association with consequent repression of the anti-apoptotic target genes, Bcl-xL and XIAP. Exposure to NEMO (IKKγ)-binding domain inhibitor peptide reduced the cytotoxic effects of bortezomib/CX-4945 treatment. Overall, our findings demonstrated that CK2 inhibition could be useful in combination with bortezomib as a novel therapeutic strategy in both T- and B-ALL.

Arsenic induced complete remission in a refractory T-ALL patient with a distinct T-cell clonal evolution without molecular complete remission: A case report

Currently, arsenic trioxide therapy is widely used for the treatment of acute promyelocytic leukemia (APL), relapsed and refractory adult T-cell leukemia/lymphoma and myelodysplastic syndrome. Regarding the broad antitumor activity of arsenic, certain studies have been undertaken to test its efficacy in treating acute T-cell lymphoblastic leukemia (T-ALL) cell lines and patients; however, to the best of our knowledge, no reports document that arsenic is able to induce the remission of T-ALL patients. The present study reports the case of young male patient diagnosed with T-ALL, with no significant response to common chemotherapy regimens, who finally achieved complete remission without minimal residual disease (as detected by flow cytometry) due to arsenic treatment. This result is encouraging, and the present study has shown that malignant TCRαβ⁺ cell clones can be detected at the molecular level using reverse transcription-polymerase chain reaction (PCR) combined with the GeneScan technique. The result is mainly based on the T-cell receptor (TCR) Vβ1 clone (a 190-base pair PCR product that with the same complementarity determining region 3 length can be detected for all samples collected during various statuses) and on undetectable TCR Vγ subfamily members, at the time of disease diagnosis. It is important to analyze the dynamically changing TCR pool in leukemia patients during therapy. Although the molecular mechanism through which arsenic contributes to malignant clone elimination remains unclear in the case presented, the use of arsenic is expected to be effective for clinically treating refractory and relapsed T-ALL patients.

Therapeutic targeting of IL-7Rα signaling pathways in ALL treatment

Increased understanding of pediatric acute lymphoblastic leukemia (ALL) pathobiology has led to dramatic improvements in patient survival. However, there is still a need to develop targeted therapies to enable reduced chemotherapy intensity and to treat relapsed patients. The interleukin-7 receptor α (IL-7Rα) signaling pathways are prime therapeutic targets because these pathways harbor genetic aberrations in both T-cell ALL and B-cell precursor ALL. Therapeutic targeting of the IL-7Rα signaling pathways may lead to improved outcomes in a subset of patients.

Targeting Notch1 and proteasome as an effective strategy to suppress T-cell lymphoproliferative neoplasms

The T-cell lymphoproliferative neoplasms (T-LPN) are characterized by a poor clinical outcome. Current therapeutics are mostly non-selective and may induce harmful side effects. It has been reported that NOTCH1 activation mutations frequently associate T-LPN. Because anti-Notch1 based therapies such as γ-secretase inhibitors (GSI) are less efficient and induce considerable side effects, we hypothesized that combining low concentrations of GSI and the proteasome inhibitor bortezomib (BTZ) may provide an effective and tolerable approach to treat T-LPN. Hence, we analyzed the in vitro and in vivo effects of GSI-I and BTZ, alone or in combination, against T-LPN. GSI-I and BTZ synergistically decreased cell viability, proliferation, and colony formation, and induced apoptosis in T-LPN cell lines. Furthermore, combining GSI-I and BTZ decreased the viability of primary T-LPN cells from patients. These effects were accompanied by deregulation of Notch1, AKT, ERK, JNK, p38 MAPK, and NF-κB survival pathways. Moreover, combination treatment inhibited T-LPN tumor growth in nude mice. In all experiments, combining low concentrations of GSI-I and BTZ was superior to using a single agent. Our data support that a synergistic antitumor activity exists between GSI-I and BTZ, and provide a rationale for successful utilization of dual Notch1 and proteasome inhibition to treat T-LPN.

Selective activation of TNFR1 and NF-κB inhibition by a novel biyouyanagin analogue promotes apoptosis in acute leukemia cells

BACKGROUND

Acquired resistance towards apoptosis is a hallmark of cancer. Elimination of cells bearing activated oncogenes or stimulation of tumor suppressor mediators may provide a selection pressure to overcome resistance. KC-53 is a novel biyouyanagin analogue known to elicit strong anti-inflammatory and anti-viral activity. The current study was designed to evaluate the anticancer efficacy and molecular mechanisms of KC-53 against human cancer cells.

METHODS

Using the MTT assay we examined initially how KC-53 affects the proliferation rates of thirteen representative human cancer cell lines in comparison to normal peripheral blood mononuclear cells (PBMCs) and immortalized cell lines. To decipher the key molecular events underlying its mode of action we selected the human promyelocytic leukemia HL-60 and the acute lymphocytic leukemia CCRF/CEM cell lines that were found to be the most sensitive to the antiproliferative effects of KC-53.

RESULTS

KC-53 promoted rapidly and irreversibly apoptosis in both leukemia cell lines at relatively low concentrations. Apoptosis was characterized by an increase in membrane-associated TNFR1, activation of Caspase-8 and proteolytic inactivation of the death domain kinase RIP1 indicating that KC-53 induced mainly the extrinsic/death receptor apoptotic pathway. Regardless, induction of the intrinsic/mitochondrial pathway was also achieved by Caspase-8 processing of Bid, activation of Caspase-9 and increased translocation of AIF to the nucleus. FADD protein knockdown restored HL-60 and CCRF/CEM cell viability and completely blocked KC-53-induced apoptosis. Furthermore, KC-53 administration dramatically inhibited TNFα-induced serine phosphorylation on TRAF2 and on IκBα hindering therefore p65/NF-κΒ translocation to nucleus. Reduced transcriptional expression of pro-inflammatory and pro-survival p65 target genes, confirmed that the agent functionally inhibited the transcriptional activity of p65.

CONCLUSIONS

Our findings demonstrate, for the first time, the selective anticancer properties of KC-53 towards leukemic cell lines and provide a detailed understanding of the molecular events underlying its dual anti-proliferative and pro-apoptotic properties. These results provide new insights into the development of innovative and targeted therapies for the treatment of some forms of leukemia.

Phosphorylation-mediated EZH2 inactivation promotes drug resistance in multiple myeloma

Alterations in chromatin modifications, such as histone methylation, have been suggested as mediating chemotherapy resistance in several cancer types; therefore, elucidation of the epigenetic mechanisms that underlie drug resistance may greatly contribute to the advancement of cancer therapies. In the present study, we identified histone H3-lysine 27 (H3K27) as a critical residue for epigenetic modification in multiple myeloma. We determined that abrogation of drug-induced H3K27 hypermethylation is associated with cell adhesion-mediated drug resistance (CAM-DR), which is the most important form of drug resistance, using a coculture system to evaluate stroma cell adhesion-dependent alterations in multiple myeloma cells. Cell adhesion counteracted anticancer drug-induced hypermethylation of H3K27 via inactivating phosphorylation of the transcription regulator EZH2 at serine 21, leading to the sustained expression of antiapoptotic genes, including IGF1, B cell CLL/lymphoma 2 (BCL2), and hypoxia inducible factor 1, α subunit (HIF1A). Pharmacological and genetic inhibition of the IGF-1R/PI3K/AKT pathway reversed CAM-DR by promoting EZH2 dephosphorylation and H3K27 hypermethylation both in vitro and in refractory murine myeloma models. Together, our findings identify and characterize an epigenetic mechanism that underlies CAM-DR and suggest that kinase inhibitors to counteract EZH2 phosphorylation should be included in combination chemotherapy to increase therapeutic index.

Deubiquitinases (DUBs) and DUB inhibitors: a patent review

INTRODUCTION

Deubiquitinating-enzymes (DUBs) are key components of the ubiquitin-proteasome system (UPS). The fundamental role of DUBs is specific removal of ubiquitin from substrates. DUBs contribute to activation/deactivation, recycling and localization of numerous regulatory proteins, and thus play major roles in diverse cellular processes. Altered DUB activity is associated with a multitudes of pathologies including cancer. Therefore, DUBs represent novel candidates for target-directed drug development.

AREAS COVERED

The article is a thorough review/accounting of patented compounds targeting DUBs and stratifying/classifying the patented compounds based on: chemical-structures, nucleic-acid compositions, modes-of-action, and targeting sites. The review provides a brief background on the UPS and the involvement of DUBs. Furthermore, methods for assessing efficacy and potential pharmacological utility of DUB inhibitor (DUBi) are discussed.

EXPERT OPINION

The FDA's approval of the 20S proteasome inhibitors (PIs): bortezomib and carfilzomib for treatment of hematological malignancies established the UPS as an anti-cancer target. Unfortunately, many patients are inherently resistant or develop resistance to PIs. One potential strategy to combat PI resistance is targeting upstream components of the UPS such as DUBs. DUBs represent a promising potential therapeutic target due to their critical roles in various cellular processes including protein turnover, localization and cellular homeostasis. While considerable efforts have been undertaken to develop DUB modulators, significant advancements are necessary to move DUBis into the clinic.

Overexpression of the shortest isoform of histone demethylase LSD1 primes hematopoietic stem cells for malignant transformation

Recent investigations indicate that epigenetic regulators act at the initial step of myeloid leukemogenesis by forming preleukemic hematopoietic stem cells (HSCs), which possess the increased self-renewal potential but retain multidifferentiation ability, and synergize with genetic abnormalities in later stages to develop full-blown acute myeloid leukemias. However, it is still unknown whether this theory is applicable to other malignancies. In this study, we demonstrate that lysine-specific demethylase 1 (LSD1) overexpression is a founder abnormality for the development of T-cell lymphoblastic leukemia/lymphoma (T-LBL) using LSD1 transgenic mice. LSD1 expression is tightly regulated via alternative splicing and transcriptional repression in HSCs and is altered in most leukemias, especially T-LBL. Overexpression of the shortest isoform of LSD1, which is specifically repressed in quiescent HSCs and demethylates histone H3K9 more efficiently than other isoforms, increases self-renewal potential via upregulation of the HoxA family but retains multidifferentiation ability with a skewed differentiation to T-cell lineages at transcriptome levels in HSCs. Transgenic mice overexpressing LSD1 in HSCs did not show obvious abnormalities but developed T-LBL at very high frequency after γ-irradiation. LSD1 overexpression appears to be the first hit in T-cell leukemogenesis and provides an insight into novel strategies for early diagnosis and effective treatment of the disease.

Inhibition of autophagy enhances the anticancer activity of bortezomib in B-cell acute lymphoblastic leukemia cells

B-cell acute lymphoblastic leukemia (B-ALL) remains a challenging disease to treat in adults because of the high rates of relapse and refractory. Bortezomib, as a proteasome inhibitor, exerts obvious cytotoxicity against ALL cells and increases the sensitivity of ALL cells to conventional chemotherapeutic agents. We observed that bortezomib inhibited proliferation, induced apoptosis, arrested the cell cycle and induced autophagy in the Nalm-6 cell line and CD34(+) primary cells. Additionally, we demonstrated that bortezomib promoted the disruption of the Bcl-2/Beclin-1 complex and increased the formation of the Beclin-1/PI3KC3 complex, leading to the initiation of autophagy. Autophagy inhibitors were employed in this study, and we found that autophagy inhibitors enhanced the anti-ALL activity of bortezomib. Taken together, these results revealed that autophagy protected B-ALL cells against the cytotoxicity of bortezomib and, in combination with autophagy inhibitors, can enhance the anticancer effects of bortezomib.

A Phase 2 study of bortezomib combined with either idarubicin/cytarabine or cytarabine/etoposide in children with relapsed, refractory or secondary acute myeloid leukemia: a report from the Children's Oncology Group

BACKGROUND

This Phase 2 study tested the tolerability and efficacy of bortezomib combined with reinduction chemotherapy for pediatric patients with relapsed, refractory or secondary acute myeloid leukemia (AML). Correlative studies measured putative AML leukemia initiating cells (AML-LIC) before and after treatment.

PROCEDURE

Patients with <400 mg/m(2) prior anthracycline received bortezomib combined with idarubicin (12 mg/m(2) days 1-3) and low-dose cytarabine (100 mg/m(2) days 1-7) (Arm A). Patients with ≥400 mg/m(2) prior anthracycline received bortezomib with etoposide (100 mg/m(2) on days 1-5) and high-dose cytarabine (1 g/m(2) every 12 hours for 10 doses) (Arm B).

RESULTS

Forty-six patients were treated with 58 bortezomib-containing cycles. The dose finding phase of Arm B established the recommended Phase 2 dose of bortezomib at 1.3 mg/m(2) on days 1, 4, and 8 with Arm B chemotherapy. Both arms were closed after failure to meet predetermined efficacy thresholds during the first stage of the two-stage design. The complete response (CR + CRp) rates were 29% for Arm A and 43% for Arm B. Counting additional CRi responses (CR with incomplete neutrophil recovery), the overall CR rates were 57% for Arm A and 48% for Arm B. The 2-year overall survival (OS) was 39 ± 15%. Correlative studies showed that LIC depletion after the first cycle was associated with clinical response.

CONCLUSION

Bortezomib is tolerable when added to chemotherapy regimens for relapsed pediatric AML, but the regimens did not exceed preset minimum response criteria to allow continued accrual. This study also suggests that AML-LIC depletion has prognostic value.

Pleiotropic roles of Notch signaling in normal, malignant, and developmental hematopoiesis in the human

The Notch signaling pathway is evolutionarily conserved across species and plays an important role in regulating cell differentiation, proliferation, and survival. It has been implicated in several different hematopoietic processes including early hematopoietic development as well as adult hematological malignancies in humans. This review focuses on recent developments in understanding the role of Notch signaling in the human hematopoietic system with an emphasis on hematopoietic initiation from human pluripotent stem cells and regulation within the bone marrow. Based on recent insights, we summarize potential strategies for treatment of human hematological malignancies toward the concept of targeting Notch signaling for fate regulation.

Purine analog-like properties of bendamustine underlie rapid activation of DNA damage response and synergistic effects with pyrimidine analogues in lymphoid malignancies

Bendamustine has shown considerable clinical activity against indolent lymphoid malignancies as a single agent or in combination with rituximab, but combination with additional anti-cancer drugs may be required for refractory and/or relapsed cases as well as other intractable tumors. In this study, we attempted to determine suitable anti-cancer drugs to be combined with bendamustine for the treatment of mantle cell lymphoma, diffuse large B-cell lymphoma, aggressive lymphomas and multiple myeloma, all of which are relatively resistant to this drug, and investigated the mechanisms underlying synergism. Isobologram analysis revealed that bendamustine had synergistic effects with alkylating agents (4-hydroperoxy-cyclophosphamide, chlorambucil and melphalan) and pyrimidine analogues (cytosine arabinoside, gemcitabine and decitabine) in HBL-2, B104, Namalwa and U266 cell lines, which represent the above entities respectively. In cell cycle analysis, bendamustine induced late S-phase arrest, which was enhanced by 4-hydroperoxy-cyclophosphamide, and potentiated early S-phase arrest by cytosine arabinoside (Ara-C), followed by a robust increase in the size of sub-G1 fractions. Bendamustine was able to elicit DNA damage response and subsequent apoptosis faster and with shorter exposure than other alkylating agents due to rapid intracellular incorporation via equilibrative nucleoside transporters (ENTs). Furthermore, bendamustine increased the expression of ENT1 at both mRNA and protein levels and enhanced the uptake of Ara-C and subsequent increase in Ara-C triphosphate (Ara-CTP) in HBL-2 cells to an extent comparable with the purine analog fludarabine. These purine analog-like properties of bendamustine may underlie favorable combinations with other alkylators and pyrimidine analogues. Our findings may provide a theoretical basis for the development of more effective bendamustine-based combination therapies.