Establishment of a novel B-cell lymphoma cell line with suppressed growth by gamma-secretase inhibitors

Discovery and Preclinical Characterization of BIIB129, a Covalent, Selective, and Brain-Penetrant BTK Inhibitor for the Treatment of Multiple Sclerosis

Multiple sclerosis (MS) is a chronic disease with an underlying pathology characterized by inflammation-driven neuronal loss, axonal injury, and demyelination. Bruton's tyrosine kinase (BTK), a nonreceptor tyrosine kinase and member of the TEC family of kinases, is involved in the regulation, migration, and functional activation of B cells and myeloid cells in the periphery and the central nervous system (CNS), cell types which are deemed central to the pathology contributing to disease progression in MS patients. Herein, we describe the discovery of BIIB129 (25), a structurally distinct and brain-penetrant targeted covalent inhibitor (TCI) of BTK with an unprecedented binding mode responsible for its high kinome selectivity. BIIB129 (25) demonstrated efficacy in disease-relevant preclinical in vivo models of B cell proliferation in the CNS, exhibits a favorable safety profile suitable for clinical development as an immunomodulating therapy for MS, and has a low projected total human daily dose.

Design, Synthesis, and In Vitro and In Vivo Evaluation of Cereblon Binding Bruton's Tyrosine Kinase (BTK) Degrader CD79b Targeted Antibody-Drug Conjugates

Antibody-drug conjugates (ADCs) are an established modality that allow for targeted delivery of a potent molecule, or payload, to a desired site of action. ADCs, wherein the payload is a targeted protein degrader, are an emerging area in the field. Herein we describe our efforts of delivering a Bruton's tyrosine kinase (BTK) bifunctional degrader 1 via a CD79b mAb (monoclonal antibody) where the degrader is linked at the ligase binding portion of the payload via a cleavable linker to the mAb. The resulting CD79b ADCs, 3 and 4, exhibit in vitro degradation and cytotoxicity comparable with that of 1, and ADC 3 can achieve more sustained in vivo degradation than intravenously administered 1 with markedly reduced systemic exposure of the payload.

DCAF1-based PROTACs with activity against clinically validated targets overcoming intrinsic- and acquired-degrader resistance

Targeted protein degradation (TPD) mediates protein level through small molecule induced redirection of E3 ligases to ubiquitinate neo-substrates and mark them for proteasomal degradation. TPD has recently emerged as a key modality in drug discovery. So far only a few ligases have been utilized for TPD. Interestingly, the workhorse ligase CRBN has been observed to be downregulated in settings of resistance to immunomodulatory inhibitory drugs (IMiDs). Here we show that the essential E3 ligase receptor DCAF1 can be harnessed for TPD utilizing a selective, non-covalent DCAF1 binder. We confirm that this binder can be functionalized into an efficient DCAF1-BRD9 PROTAC. Chemical and genetic rescue experiments validate specific degradation via the CRL4DCAF1 E3 ligase. Additionally, a dasatinib-based DCAF1 PROTAC successfully degrades cytosolic and membrane-bound tyrosine kinases. A potent and selective DCAF1-BTK-PROTAC (DBt-10) degrades BTK in cells with acquired resistance to CRBN-BTK-PROTACs while the DCAF1-BRD9 PROTAC (DBr-1) provides an alternative strategy to tackle intrinsic resistance to VHL-degrader, highlighting DCAF1-PROTACS as a promising strategy to overcome ligase mediated resistance in clinical settings.

Defining cellular responses to HDAC-selective inhibitors reveals that efficient targeting of HDAC3 is required to elicit cytotoxicity and overcome naïve resistance to pan-HDACi in diffuse large B cell lymphoma

Approved histone deacetylase (HDAC) inhibitors have low efficacy against the most commonly-diagnosed non-Hodgkin lymphoma, diffuse large B cell lymphoma (DLBCL), but the mechanisms underlying clinical resistance are poorly understood. Using a DLBCL cell-based model, we previously demonstrated that resistance to pan-HDAC inhibitors (HDACi) is characterized by reversible growth arrest and sensitivity by mitotic arrest and apoptosis. The goal of the current study is to better define mechanisms of sensitivity and resistance to the cytotoxic effects of HDACi by using HDAC-selective inhibitors to determine which HDACs need to be targeted to achieve the sensitive and resistant phenotypes. We find that an inhibitor selective for HDACs 1 and 2 induces G1 arrest across DLBCL cell lines used, which is consistent with the resistant phenotype. In contrast an HDAC3-selective inhibitor induces DNA damage and cytotoxicity in a cell line that is sensitive to pan-HDACi but has no effect on resistant cell lines. RNAi-mediated depletion of HDAC3 indicate the presence of a long-lived population of HDAC3 in DLBCL cell lines. Finally, doses of pan-HDACi 3-5 times higher than the IC50 established for reversible growth inhibition induce the sensitive phenotype in resistant cell lines, suggesting that resistance may be associated with failure to efficiently inhibit HDAC3. Our findings indicate that selective inhibition of HDACs 1 and 2 is associated with G1 arrest and resistance to pan-HDACi while efficient targeting of HDAC3 could be key to achieving a cytotoxic response. Thus, our work reveals a potential novel mechanism of resistance to pan-HDACi.

Systems-level analyses of protein-protein interaction network dysfunctions via epichaperomics identify cancer-specific mechanisms of stress adaptation

Systems-level assessments of protein-protein interaction (PPI) network dysfunctions are currently out-of-reach because approaches enabling proteome-wide identification, analysis, and modulation of context-specific PPI changes in native (unengineered) cells and tissues are lacking. Herein, we take advantage of chemical binders of maladaptive scaffolding structures termed epichaperomes and develop an epichaperome-based 'omics platform, epichaperomics, to identify PPI alterations in disease. We provide multiple lines of evidence, at both biochemical and functional levels, demonstrating the importance of these probes to identify and study PPI network dysfunctions and provide mechanistically and therapeutically relevant proteome-wide insights. As proof-of-principle, we derive systems-level insight into PPI dysfunctions of cancer cells which enabled the discovery of a context-dependent mechanism by which cancer cells enhance the fitness of mitotic protein networks. Importantly, our systems levels analyses support the use of epichaperome chemical binders as therapeutic strategies aimed at normalizing PPI networks.

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.

NRX-0492 degrades wild-type and C481 mutant BTK and demonstrates in vivo activity in CLL patient-derived xenografts

Bruton tyrosine kinase (BTK) is essential for B-cell receptor (BCR) signaling, a driver of chronic lymphocytic leukemia (CLL). Covalent inhibitors bind C481 in the active site of BTK and have become a preferred CLL therapy. Disease progression on covalent BTK inhibitors is commonly associated with C481 mutations. Here, we investigated a targeted protein degrader, NRX-0492, that links a noncovalent BTK-binding domain to cereblon, an adaptor protein of the E3 ubiquitin ligase complex. NRX-0492 selectively catalyzes ubiquitylation and proteasomal degradation of BTK. In primary CLL cells, NRX-0492 induced rapid and sustained degradation of both wild-type and C481 mutant BTK at half maximal degradation concentration (DC50) of ≤0.2 nM and DC90 of ≤0.5 nM, respectively. Sustained degrader activity was maintained for at least 24 hours after washout and was equally observed in high-risk (deletion 17p) and standard-risk (deletion 13q only) CLL subtypes. In in vitro testing against treatment-naïve CLL samples, NRX-0492 was as effective as ibrutinib at inhibiting BCR-mediated signaling, transcriptional programs, and chemokine secretion. In patient-derived xenografts, orally administered NRX-0492 induced BTK degradation and inhibited activation and proliferation of CLL cells in blood and spleen and remained efficacious against primary C481S mutant CLL cells collected from a patient progressing on ibrutinib. Oral bioavailability, >90% degradation of BTK at subnanomolar concentrations, and sustained pharmacodynamic effects after drug clearance make this class of targeted protein degraders uniquely suitable for clinical translation, in particular as a strategy to overcome BTK inhibitor resistance. Clinical studies testing this approach have been initiated (NCT04830137, NCT05131022).

BTG1 inactivation drives lymphomagenesis and promotes lymphoma dissemination through activation of BCAR1

Understanding the functional role of mutated genes in cancer is required to translate the findings of cancer genomics into therapeutic improvement. BTG1 is recurrently mutated in the MCD/C5 subtype of diffuse large B-cell lymphoma (DLBCL), which is associated with extranodal dissemination. Here, we provide evidence that Btg1 knock out accelerates the development of a lethal lymphoproliferative disease driven by Bcl2 overexpression. Furthermore, we show that the scaffolding protein BCAR1 is a BTG1 partner. Moreover, after BTG1 deletion or expression of BTG1 mutations observed in patients with DLBCL, the overactivation of the BCAR1-RAC1 pathway confers increased migration ability in vitro and in vivo. These modifications are targetable with the SRC inhibitor dasatinib, which opens novel therapeutic opportunities in BTG1 mutated DLBCL.

Investigation of the anti-tumor mechanism of tirabrutinib, a highly selective Bruton's tyrosine kinase inhibitor, by phosphoproteomics and transcriptomics

Tirabrutinib is a highly selective Bruton's tyrosine kinase (BTK) inhibitor used to treat hematological malignancies. We analyzed the anti-tumor mechanism of tirabrutinib using phosphoproteomic and transcriptomic methods. It is important to check the drug's selectivity against off-target proteins to understand the anti-tumor mechanism based on the on-target drug effect. Tirabrutinib's selectivity was evaluated by biochemical kinase profiling assays, peripheral blood mononuclear cell stimulation assays, and the BioMAP system. Next, in vitro and in vivo analyses of the anti-tumor mechanisms were conducted in activated B-cell-like diffuse large B-cell lymphoma (ABC-DLBCL) cells followed by phosphoproteomic and transcriptomic analyses. In vitro kinase assays showed that, compared with ibrutinib, tirabrutinib and other second-generation BTK inhibitors demonstrated a highly selective kinase profile. Data from in vitro cellular systems showed that tirabrutinib selectively affected B-cells. Tirabrutinib inhibited the cell growth of both TMD8 and U-2932 cells in correlation with the inhibition of BTK autophosphorylation. Phosphoproteomic analysis revealed the downregulation of ERK and AKT pathways in TMD8. In the TMD8 subcutaneous xenograft model, tirabrutinib showed a dose-dependent anti-tumor effect. Transcriptomic analysis indicated that IRF4 gene expression signatures had decreased in the tirabrutinib groups. In conclusion, tirabrutinib exerted an anti-tumor effect by regulating multiple BTK downstream signaling proteins, such as NF-κB, AKT, and ERK, in ABC-DLBCL.

In Vitro Diffuse Large B-Cell Lymphoma Cell Line Models as Tools to Investigate Novel Immunotherapeutic Strategies

Despite the high incidence of diffuse large B-cell lymphoma (DLBCL), its management constitutes an ongoing challenge. The most common DLBCL variants include activated B-cell (ABC) and germinal center B-cell-like (GCB) subtypes including DLBCL with MYC and BCL2/BCL6 rearrangements which vary among each other with sensitivity to standard rituximab (RTX)-based chemoimmunotherapy regimens and lead to distinct clinical outcomes. However, as first line therapies lead to resistance/relapse (r/r) in about half of treated patients, there is an unmet clinical need to identify novel therapeutic strategies tailored for these patients. In particular, immunotherapy constitutes an attractive option largely explored in preclinical and clinical studies. Patient-derived cell lines that model primary tumor are indispensable tools that facilitate preclinical research. The current review provides an overview of available DLBCL cell line models and their utility in designing novel immunotherapeutic strategies.

A novel IRAK4/PIM1 inhibitor ameliorates rheumatoid arthritis and lymphoid malignancy by blocking the TLR/MYD88-mediated NF-κB pathway

Interleukin-1 receptor-associated kinase 4 (IRAK4) is a pivotal enzyme in the Toll-like receptor (TLR)/MYD88 dependent signaling pathway, which is highly activated in rheumatoid arthritis tissues and activated B cell-like diffuse large B-cell lymphoma (ABC-DLBCL). Inflammatory responses followed by IRAK4 activation promote B-cell proliferation and aggressiveness of lymphoma. Moreover, proviral integration site for Moloney murine leukemia virus 1 (PIM1) functions as an anti-apoptotic kinase in propagation of ABC-DLBCL with ibrutinib resistance. We developed a dual IRAK4/PIM1 inhibitor KIC-0101 that potently suppresses the NF-κB pathway and proinflammatory cytokine induction in vitro and in vivo. In rheumatoid arthritis mouse models, treatment with KIC-0101 significantly ameliorated cartilage damage and inflammation. KIC-0101 inhibited the nuclear translocation of NF-κB and activation of JAK/STAT pathway in ABC-DLBCLs. In addition, KIC-0101 exhibited an anti-tumor effect on ibrutinib-resistant cells by synergistic dual suppression of TLR/MYD88-mediated NF-κB pathway and PIM1 kinase. Our results suggest that KIC-0101 is a promising drug candidate for autoimmune diseases and ibrutinib-resistant B-cell lymphomas.

Establishment and characterization of a new activated B-cell-like DLBCL cell line, TMD12

We report the establishment of a novel activated B-cell-like (ABC) diffuse large B-cell lymphoma (DLBCL) cell line, designated as TMD12, from a patient with highly refractory DLBCL. ABC-DLBCL is a subtype with a relatively unfavorable prognosis that was originally categorized using gene expression profiling according to its cell of origin. TMD12 cells were isolated from the pleural effusion of the patient at relapse and passaged continuously in vitro for >4 years. The cells displayed cluster of differentiation (CD)19, CD20, CD22, CD38, human leukocyte antigen-DR isotype, and κ positivity and CD5, CD10, CD23, and λ negativity, as detected using flow cytometric analysis. The chromosomal karyotypic analysis, including the spectral karyotyping method, confirmed t(1;19)(q21:q13.1), del(6q23), gain of chromosome 18, and other abnormalities. Mutation analyses, including whole-exome sequencing, revealed that TMD12 cells harbored mutations in MYD88 and CD79B, indicating an ABC subtype. TMD12 cells exhibited chronic active B-cell receptor signaling and constitutive activation of the nuclear factor κB pathway, which is typically associated with sensitivity to a specific Bruton tyrosine kinase inhibitor, ibrutinib. Intriguingly, TMD12 cells displayed moderate resistance to ibrutinib and lacked activation of Janus kinase/signal transducers and activators of transcription 3 signaling, another hallmark of this DLBCL subtype. Treatment with an inhibitor against tumor progression locus 2 (TPL2), a multifunctional intracellular kinase that is activated particularly downstream of Toll-like receptors or MYD88 and IκB kinase α/β (IKKα/β), suppressed the proliferation of TMD12 cells, implying the possible involvement of the TPL2-p105 pathway in the tumorigenesis of ABC-DLBCL. Because only a limited number of ABC-DLBCL cell lines are currently available, TMD12 cells might provide a useful tool in the search for novel druggable targets for this intractable lymphoma.

Altered pathways and targeted therapy in double hit lymphoma

High-grade B-cell lymphoma with translocations involving MYC and BCL2 or BCL6, usually referred to as double hit lymphoma (DHL), is an aggressive hematological malignance with distinct genetic features and poor clinical prognosis. Current standard chemoimmunotherapy fails to confer satisfying outcomes and few targeted therapeutics are available for the treatment against DHL. Recently, the delineating of the genetic landscape in tumors has provided insight into both biology and targeted therapies. Therefore, it is essential to understand the altered signaling pathways of DHL to develop treatment strategies with better clinical benefits. Herein, we summarized the genetic alterations in the two DHL subtypes (DHL-BCL2 and DHL-BCL6). We further elucidate their implications on cellular processes, including anti-apoptosis, epigenetic regulations, B-cell receptor signaling, and immune escape. Ongoing and potential therapeutic strategies and targeted drugs steered by these alterations were reviewed accordingly. Based on these findings, we also discuss the therapeutic vulnerabilities that coincide with these genetic changes. We believe that the understanding of the DHL studies will provide insight into this disease and capacitate the finding of more effective treatment strategies.

An Overview on Diffuse Large B-Cell Lymphoma Models: Towards a Functional Genomics Approach

Simple Summary

Lymphoma research is a paradigm of integrating basic and applied research within the fields of molecular marker-based diagnosis and therapy. In recent years, major advances in next-generation sequencing have substantially improved the understanding of the genomics underlying diffuse large B-cell lymphoma (DLBCL), the most frequent type of B-cell lymphoma. This review addresses the various approaches that have helped unveil the biology and intricate alterations in this pathology, from cell lines to more sophisticated last-generation experimental models, such as organoids. We also provide an overview of the most recent findings in the field, their potential relevance for designing targeted therapies and the corresponding applicability to personalized medicine.

Abstract

Lymphoma research is a paradigm of the integration of basic and clinical research within the fields of diagnosis and therapy. Clinical, phenotypic, and genetic data are currently used to predict which patients could benefit from standard treatment. However, alternative therapies for patients at higher risk from refractoriness or relapse are usually empirically proposed, based on trial and error, without considering the genetic complexity of aggressive B-cell lymphomas. This is primarily due to the intricate mosaic of genetic and epigenetic alterations in lymphomas, which are an obstacle to the prediction of which drug will work for any given patient. Matching a patient’s genes to drug sensitivity by directly testing live tissues comprises the “precision medicine” concept. However, in the case of lymphomas, this concept should be expanded beyond genomics, eventually providing better treatment options for patients in need of alternative therapeutic approaches. We provide an overview of the most recent findings in diffuse large B-cell lymphomas genomics, from the classic functional models used to study tumor biology and the response to experimental treatments using cell lines and mouse models, to the most recent approaches with spheroid/organoid models. We also discuss their potential relevance and applicability to daily clinical practice.

Specific interactions of BCL-2 family proteins mediate sensitivity to BH3-mimetics in diffuse large B-cell lymphoma

The BCL-2-specific inhibitor, ABT-199 (venetoclax) has exhibited remarkable clinical activity in nearly all cases of chronic lymphocytic leukemia. In contrast, responses are usually much less in diffuse large B-cell lymphoma (DLBCL), despite high level expression of BCL-2 in over 40% of cases, indicating that co-expression of related anti-apoptotic BCL-2 family proteins may limit the activity of ABT-199. We have investigated the roles of BCL-2 proteins in DLBCL cells using a panel of specific BCL-2 homology 3 (BH3)-mimetics and identified subgroups of these cells that exhibited marked and specific dependency on either BCL-2, BCL-X_L or MCL-1 for survival. Dependency was associated with selective sequestration of the pro-apoptotic proteins BIM, BAX and BAK by the specific anti-apoptotic BCL-2 protein which was important for cellular survival. Sensitivity to BH3-mimetics was independent of genetic alterations involving the BCL-2 family and only partially correlated with protein expression levels. Treatment with ABT-199 displaced BAX and BIM from BCL-2, subsequently leading to BAK activation and apoptosis. In contrast, apoptosis induced by inhibiting BCL-X_L with A1331852 was associated with a displacement of both BAX and BAK from BCL-X_L and occurred independently of BIM. Finally, the MCL-1 inhibitor S63845 induced mainly BAX-dependent apoptosis mediated by a displacement of BAK, BIM and NOXA from MCL-1. In conclusion, our study indicates that in DLBCL, the heterogeneous response to BH3-mimetics is mediated by selective interactions between BAX, BAK and anti-apoptotic BCL-2 proteins.

B cells with aberrant activation of Notch1 signaling promote Treg and Th2 cell-dominant T-cell responses via IL-33

The Notch-signaling pathway in a variety of mature B-cell neoplasms is often activated by gene alterations, but its role remains unclear. Here, we show that B cells harboring dysregulated activation of Notch1 signaling have an immunomodulatory effect on T cells by amplifying regulatory T (Treg) and T helper 2 (Th2) cell responses in an interleukin-33 (IL-33)-dependent manner. A conditional mouse model, in which constitutive expression of an active form of Notch1 is induced in B cells by Aicda gene promoter-driven Cre recombinase, revealed no obvious phenotypic changes in B cells; however, mice demonstrated an expansion of Treg and Th2 cell subsets and a decrease in cytokine production by Th1 and CD8⁺ T cells. The mice were susceptible to soft tissue sarcoma and defective production of CD8⁺ T cells specific for inoculated tumor cells, suggesting impaired antitumor T-cell activity. Gene-expression microarray revealed that altered T-cell responses were due to increased IL-33 production by Notch1-activated B cells. Knockout of IL33 or blockade of IL-33 by a receptor-blocking antibody abrogated the Treg and Th2 cell-dominant T-cell response triggered by B cells. Gene-expression data derived from human diffuse large B-cell lymphoma (DLBCL) samples showed that an activated Notch-signaling signature correlates positively with IL33 expression and Treg cell-rich gene-expression signatures. These findings indicate that B cells harboring dysregulated Notch signaling alter T-cell responses via IL-33, and suggest that aberrant activation of Notch signaling plays a role in fostering immune privilege in mature B-cell neoplasms.

The γ-secretase inhibitor GSI-I interacts synergistically with the proteasome inhibitor bortezomib to induce ALK+ anaplastic large cell lymphoma cell apoptosis

Single agent treatment of the γ-secretase inhibitor (GSI-I) or proteasome inhibitor in anaplastic lymphoma kinase positive anaplastic large cell lymphoma (ALK+ ALCL) shows limited response and considerable toxicity. Here, we examined the effects of the combination of low dose GSI-I and the proteasome inhibitor bortezomib (BTZ) in ALK+ ALCL cells in vivo and in vitro. We found that ALK+ ALCL cells treated with the BTZ and GSI-I combination treatment showed elevated apoptosis, consistent with increased caspase activation, compared with BTZ or GSI-I alone. The combination treatment also inhibited AKT and extracellular signal-related kinase pathways, as well as stress-related cascades, including the c-jun N-terminal kinase and stress-activated kinases. Moreover, combined treatment in a murine xenograft model resulted in increased apoptosis in tumor tissues and reduced tumor growth. Our results reveal the synergistic anti-tumor effects of low dose inhibitors against γ-secretase and the proteasome and suggest the potential application of the tolerable BTZ/GSI-I combined agents in treating ALK+ ALCL in future clinical treatment.

The NOTCH Pathway and Its Mutations in Mature B Cell Malignancies

The systematic application of next-generation sequencing to large cohorts of oncologic samples has opened a Pandora's box full of known and novel genetic lesions implicated in different steps of cancer development and progression. Narrowing down to B cell malignancies, many previously unrecognized genes emerged as recurrently mutated. The challenge now is to determine how the mutation in a given gene affects the biology of the disease, paving the way to functional genomics studies. Mutations in NOTCH family members are shared by several disorders of the B series, even if with variable frequencies and mutational patterns. In silico predictions, revealed that mutations occurring in NOTCH receptors, despite being qualitatively different, may have similar effects on protein processing, ultimately leading to enhanced pathway activation. The discovery of mutations occurring also in downstream players, either potentiating positive signals or compromising negative regulators, indicates that multiple mechanisms in neoplastic B cells concur to activate NOTCH pathway. These findings are supported by results obtained in chronic lymphocytic leukemia and splenic marginal zone B cell lymphoma where deregulation of NOTCH signaling has been functionally characterized. The emerging picture confirms that NOTCH signaling is finely tuned in cell- and microenvironment-dependent ways. In B cell malignancies, it contributes to the regulation of proliferation, survival and migration. However, deeper biological studies are needed to pinpoint the contribution of NOTCH in the hierarchy of events driving B cells transformation, keeping in mind its role in normal B cells development. Because of its relevance in leukemia and lymphoma biology, the NOTCH pathway might represent an appealing therapeutic target: the next few years will tell whether this potential will be fulfilled.

Anti-tumor efficacy study of the Bruton's tyrosine kinase (BTK) inhibitor, ONO/GS-4059, in combination with the glycoengineered type II anti-CD20 monoclonal antibody obinutuzumab (GA101) demonstrates superior in vivo efficacy compared to ONO/GS-4059 in combination with rituximab

The activated B-cell diffuse large B-cell-like lymphoma (ABC-DLBCL) correlates with poor prognosis. The B-cell receptor signaling pathway is known to be dysregulated in NHL/CLL and given BTK is a downstream mediator of BCR signaling, BTK constitutes an interesting and obvious therapeutic target. Given the high potency and selectivity of the BTK inhibitor, ONO/GS-4059, it was hypothesized that, the anti-tumor activity of ONO/GS-4059 could be further enhanced by combining it with the anti-CD20 Abs, rituximab (RTX) or obinutuzumab (GA101). ONO/GS-4059 combined with GA101 or RTX was significantly better than the respective monotherapy with tumor growth inhibition (TGI) of 90% for the GA101 combination and 86% for the RTX combination. In contrast, ibrutinib (PCI-32765) combined with RTX did not result in improved efficacy compared with respective monotherapy. Taken together these data indicate that the combination of ONO/GS-4059 with rituximab and particularly obinutuzumab may be an effective treatment for ABC-DLBCL.

Synergistic induction of apoptosis by combination of BTK and dual mTORC1/2 inhibitors in diffuse large B cell lymphoma

Diffuse large B cell lymphoma is generally treated by chemotherapy and there is an unmet medical need for novel targeted therapies or combination therapies. Using in vitro screening, we have identified the combination of ibrutinib, an inhibitor of the tyrosine kinase BTK, and AZD2014, an mTOR catalytic inhibitor, as being highly synergistic in killing ABC-subtype DLBCL cell lines. Simultaneous inhibition of BTK and mTOR causes apoptosis both in vitro and in vivo and results in tumor regression in a xenograft model. We identify two parallel mechanisms that underlie apoptosis in this setting: cooperative inhibition of cap-dependent translation, and the inhibition of an NF-κB/IL10/STAT3 autocrine loop. Combined disruption of these pathways is required for apoptosis. These data represent a rational basis for the dual inhibition of BTK and mTOR as a potential treatment for ABC-subtype DLBCL.

The Link between Autoimmunity and Lymphoma: Does NOTCH Signaling Play a Contributing Role?

An association between certain autoimmune conditions and increased risk of developing lymphoma is well documented. Recent evidence points to NOTCH signaling as a strong driver of autoimmunity. Furthermore, a role for NOTCH in various lymphomas, including classical Hodgkin lymphoma, non-Hodgkin lymphoma, and T cell lymphoma has also been described. In this mini-review, we will outline what is known about involvement of NOTCH signaling in those autoimmune conditions, such as rheumatoid arthritis and primary Sjörgren’s syndrome, which show an increased risk for subsequent diagnosis of lymphoma. Furthermore, we will detail what is known about the lymphomas associated with these autoimmune conditions and how aberrant or sustained NOTCH signaling in the immune cells that mediate these diseases may contribute to lymphoma.

The truncate mutation of Notch2 enhances cell proliferation through activating the NF-κB signal pathway in the diffuse large B-cell lymphomas

The Notch2 is a critical membrane receptor for B-cell functions, and also displays various biological roles in lymphoma pathogenesis. In this article, we reported that 3 of 69 (4.3%) diffuse large B-cell lymphomas (DLBCLs) exhibited a truncate NOTCH2 mutation at the nucleotide 7605 (G/A) in the cDNA sequence, which led to partial deletion of the C-terminal of PEST (proline-, glutamic acid-, serine- and threonine-rich) domain. The truncate Notch2 activated both the Notch2 and the NF-κB signals and promoted the proliferation of B-cell lymphoma cell lines, including DLBCL and Burkitt's lymphoma cell lines. Moreover, the ectopic proliferation was completely inhibited by ammonium pyrrolidinedithiocarbamate (PDTC), an NF-κB inhibitor. Simultaneously, PDTC also reduced the expression level of Notch2. Based on these results, we conclude that the Notch2 receptor with PEST domain truncation enhances cell proliferation which may be associated with the activation of the Notch2 and the NF-κB signaling. Our results are expected to provide a possible target for new DLBCL therapies by suppressing the Notch2 and the NF-κB signaling.

Essential role of the linear ubiquitin chain assembly complex in lymphoma revealed by rare germline polymorphisms

Constitutive activation of NF-κB is a hallmark of the activated B cell-like (ABC) subtype of diffuse large B-cell lymphoma (DLBCL), owing to upstream signals from the B-cell receptor (BCR) and MYD88 pathways. The linear polyubiquitin chain assembly complex (LUBAC) attaches linear polyubiquitin chains to IκB kinase-γ, a necessary event in some pathways that engage NF-κB. Two germline polymorphisms affecting the LUBAC subunit RNF31 are rare among healthy individuals (∼1%) but enriched in ABC DLBCL (7.8%). These polymorphisms alter RNF31 α-helices that mediate binding to the LUBAC subunit RBCK1, thereby increasing RNF31-RBCK1 association, LUBAC enzymatic activity, and NF-κB engagement. In the BCR pathway, LUBAC associates with the CARD11-MALT1-BCL10 adapter complex and is required for ABC DLBCL viability. A stapled RNF31 α-helical peptide based on the ABC DLBCL-associated Q622L polymorphism inhibited RNF31-RBCK1 binding, decreased NF-κB activation, and killed ABC DLBCL cells, credentialing this protein-protein interface as a therapeutic target.

SIGNIFICANCE

We provide genetic, biochemical, and functional evidence that the LUBAC ubiquitin ligase is a therapeutic target in ABC DLBCL, the DLBCL subtype that is most refractory to current therapy. More generally, our findings highlight the role of rare germline-encoded protein variants in cancer pathogenesis.

The challenge of targeting notch in hematologic malignancies

Notch signaling can play oncogenic and tumor suppressor roles depending on cell type. Hematologic malignancies encompass a wide range of transformed cells, and consequently the roles of Notch are diverse in these diseases. For example Notch is a potent T-cell oncogene, with >50% of T-cell acute lymphoblastic leukemia (T-ALL) cases carry activating mutations in the Notch1 receptor. Targeting Notch signaling in T-ALL with gamma-secretase inhibitors, which prevent Notch receptor activation, has shown pre-clinical activity, and is under evaluation clinically. In contrast, Notch signaling inhibits acute myeloblastic leukemia growth and survival, and although targeting Notch signaling in AML with Notch activators appears to have pre-clinical activity, no Notch agonists are clinically available at this time. As such, despite accumulating evidence about the biology of Notch signaling in different hematologic cancers, which provide compelling clinical promise, we are only beginning to target this pathway clinically, either on or off. In this review, we will summarize the evidence for oncogenic and tumor suppressor roles of Notch in a wide range of leukemias and lymphomas, and describe therapeutic opportunities for now and the future.

RBPJ is a novel target for rhabdomyosarcoma therapy

The Notch pathway regulates a broad spectrum of cell fate decisions and differentiation processes during fetal and postnatal development. In addition, the Notch pathway plays an important role in controlling tumorigenesis. However, the role of RBPJ, a transcription factor in the Notch pathway, in the development of tumors is largely unknown. In this study, we focused on the role of RBPJ in the pathogenesis of rhabdomyosarcoma (RMS). Our data showed that Notch pathway genes were upregulated and activated in human RMS cell lines and patient samples. Inhibition of the Notch pathway by a γ-secretase inhibitor (GSI) decreased the in vitro proliferation of RMS cells. Knockdown of RBPJ expression by RNAi inhibited the anchorage-independent growth of RMS cells and the growth of xenografts in vivo. Additionally, overexpression of RBPJ promoted the anchorage-independent growth of RMS cells. Further, we revealed that RBPJ regulated the cell cycle in RMS xenograft tumors and decreased proliferation. Our findings suggest that RBPJ regulates the RMS growth, and that the inhibition of RBPJ may be an effective therapeutic approach for patients with RMS.

Therapeutic approaches to modulating Notch signaling: current challenges and future prospects

Dysregulated Notch signaling has been implicated in numerous human diseases, including a broad spectrum of cancers. Mutations in Notch1 are prevalent in T-cell acute lymphoblastic leukemia, and abnormal expression of different human Notch receptors contributes to B-cell tumors as well as cancers of the breast, lung, pancreas, skin, prostate, colon, brain and other tissues. Several γ-secretase inhibitors, small chemical compounds that were initially developed to inhibit the activity of the γ-secretase aspartyl protease in Alzheimer's disease, are now being explored for their potential chemotherapeutic applications in Notch-associated cancers. An alternative approach involves the development of antibodies to inhibit specific Notch receptors, their activating ligands, or other components of the Notch pathway in tumors. Here we review recent progress and current challenges in the use of these strategies to modulate Notch signaling for cancer therapy.

Notch-ing from T-cell to B-cell lymphoid malignancies

Notch receptors are transmembrane proteins critically determining cell fate and maintenance of progenitor cells in many developmental systems. Notch signaling is involved in stem cell self-renewal and regulates the main functions of cell life at different levels of development: cell proliferation, differentiation and apoptosis. By virtue of its involvement in the regulation of cell physiology, it is not surprising that a deregulation of the Notch pathway leads to the development of different tumors. In this review, we critically discuss the latest findings concerning Notch roles in hematologic oncology, with a special focus on T-cell acute lymphoblastic leukemia and B-cell malignancies. We also describe the molecular mediators of Notch-driven oncogenic effects and the current pharmacological approaches targeting Notch signaling.

GSI-I (Z-LLNle-CHO) inhibits γ-secretase and the proteosome to trigger cell death in precursor-B acute lymphoblastic leukemia

Gamma secretase inhibitors (GSIs) comprise a growing class of compounds that interfere with the membrane-bound Notch signaling protein and its downstream intra-nuclear transcriptional targets. As GSI-I (Z-LLNle-CHO) is also a derivative of a widely used proteosome inhibitor MG-132, we hypothesized that this compound might be active in precursor-B acute lymphoblastic leukemia (ALL) cell lines and patient samples. We found that GSI-I treatment of precursor-B ALL blasts induced apoptotic cell death within 18-24 h. With confirmation using RNA and protein analyses, GSI-I blocked nuclear accumulation of cleaved Notch1 and Notch2, and inhibited Notch targets Hey2 and Myc. Microarray analyses of 207 children with high-risk precursor-B ALL demonstrate that Notch pathway expression is a common feature of these neoplasms. However, microarray studies also implicated additional transcriptional targets in GSI-I-dependent cell death, including genes in the unfolded protein response, nuclear factor-κB and p53 pathways. Z-LLNle-CHO blocks both γ-secretase and proteosome activity, inducing more robust cell death in precursor-B ALL cells than either proteosome-selective or γ-secretase-selective inhibitors alone. Using Z-LLNle-CHO in a nonobese diabetes/severe combined immunodeficiency (NOD/SCID) precursor-B ALL xenograft model, we found that GSI-I alone delayed or prevented engraftment of B-lymphoblasts in 50% of the animals comprising the experimental group, suggesting that this compound is worthy of additional testing.

Notch-regulation upon Dll4-stimulation of TGFb-induced apoptosis and gene expression in human B-cell non-Hodgkin lymphomas

Notch-signalling has been implicated as a pathogenetic factor and a therapeutical target in T-cell leukaemias and in some lymphomas of B-cell origin. Our aim was to investigate the role of Notch-signalling in apoptosis regulation in human non-Hodgkin B-cell lymphoma (B-NHL) cell lines and in primary chronic lymhocytic leukaemia (CLL) cells using Delta-like 4 (Dll4) ligand mediated Notch activation and gamma-secretase inhibitor (GSI) mediated Notch inhibition in vitro. The potential cross-talk of Notch with the transforming growth factor-beta (TGFb) pathway in apoptosis induction was also explored, and the effect of GSI on drug-induced apoptosis was assessed. Modulation of Notch-signalling by itself did not change the rate of apoptosis in B-NHL cell lines and in CLL cells. TGFb-induced apoptosis was decreased - but not completely abolished - by GSI in TGFb-sensitive cell lines, but resistance to the apoptotic effects of TGFb were not reversed by Notch activation or inhibition. Drug-induced apoptosis was not modified by GSI. We identified Hairy/Enhancer of Split (HES)-1 as a TGFb target gene in selected - TGFb-sensitive - B-NHL cell lines. TGFb-induced HES-1 was only partially Notch-dependent in later phases. Apoptosis regulation by TGFb and GSI was not dependent on the transcriptional regulation of c-myc. In conclusion, our data does not support a unifying role of Notch in regulating apoptosis in B-NHL, but warns that gamma-secretase inhibitors may actually counteract apoptosis in some cases.

z-Leucinyl-leucinyl-norleucinal induces apoptosis of human glioblastoma tumor-initiating cells by proteasome inhibition and mitotic arrest response

Gamma-secretase inhibitors have been proposed as drugs able to kill cancer cells by targeting the NOTCH pathway. Here, we investigated two of such inhibitors, the Benzyloxicarbonyl-Leu-Leu-Nle-CHO (LLNle) and the N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT), to assess whether they were effective in killing human glioblastoma tumor-initiating cells (GBM TIC) in vitro. We found that only LLNle was able at the micromolar range to induce the death of GBM TICs by apoptosis. To determine the cellular processes that were activated in GBM TICs by treatment with LLNle, we analyzed the amount of the NOTCH intracellular domain and the gene expression profiles following treatment with LLNle, DAPT, and DMSO (vehicle). We found that LLNIe, beside inhibiting the generation of the NOTCH intracellular domain, also induces proteasome inhibition, proteolytic stress, and mitotic arrest in these cells by repressing genes required for DNA synthesis and mitotic progression and by activating genes acting as mitotic inhibitors. DNA content flow cytometry clearly showed that cells treated with LLNle undergo arrest in the G(2)-M phases of the cell cycle. We also found that DAPT and L-685,458, another selective Notch inhibitor, were unable to kill GBM TICs, whereas lactacystin, a pure proteasome inhibitor, was effective although at a much less extent than LLNle. These data show that LLNle kills GBM TIC cells by inhibiting the proteasome activity. We suggest that LLNle, being able to target two relevant pathways for GBM TIC survival, may have a potential therapeutic value that deserves further investigation in animal models.

Mechanisms and clinical prospects of Notch inhibitors in the therapy of hematological malignancies

Activation of Notch signaling has been implicated in pathogenesis of various hematologic tumors including leukemias, lymphomas, and multiple myeloma. Pre-clinical studies have suggested that inhibition of Notch could be an attractive new approach to treatment of hematologic malignancies. This review discusses most recent findings in the field and potential role of Notch signaling as a therapeutic target focusing on the effects of gamma-secretase inhibitors.

Activity of the notch-signalling pathway in circulating human chronic lymphocytic leukaemia cells

Dysregulation of the Notch-pathway has been implicated in the pathogenesis of chronic lymphocytic leukaemia (B-CLL). We characterized the mRNA expression of Notch pathway elements in circulating normal B- and B-CLL cells, and compared expression profiles with clinical and prognostic data. Similar expression profiles were found in normal B-cells and B-CLL cells, however, most B-CLL samples showed lower Hairy/Enhancer of Split-1 expression than normal B-cells, which suggests that the pathway is not over-activated in B-CLL. The expression of Notch-pathway genes did not correlate with other prognostic factors of B-CLL. The importance of Notch-signalling in CLL cells in lymphatic tissue microenvironments remains to be determined.