CXCR4 expression in neuroblastoma tumors correlates with disease severity. In this study, we describe mechanisms by which CXCR4 signaling controls neuroblastoma tumor growth and response to therapy. ...We found that overexpression of CXCR4 or stimulation with CXCL12 supports neuroblastoma tumorigenesis. Moreover, CXCR4 inhibition with the high-affinity CXCR4 antagonist BL-8040 prevented tumor growth and reduced survival of tumor cells. These effects were mediated by the upregulation of miR-15a/16-1, which resulted in downregulation of their target genes BCL-2 and cyclin D1, as well as inhibition of ERK. Overexpression of miR-15a/16-1 in cells increased cell death, whereas antagomirs to miR-15a/16-1 abolished the proapoptotic effects of BL-8040. CXCR4 overexpression also increased miR-15a/16-1, shifting their oncogenic dependency from the BCL-2 to the ERK signaling pathway. Overall, our results demonstrate the therapeutic potential of CXCR4 inhibition in neuroblastoma treatment and provide a rationale to test combination therapies employing CXCR4 and BCL-2 inhibitors to increase the efficacy of these agents.
These results provide a mechanistic rationale for combination therapy of CXCR4 and BCL-2 inhibitors to treat a common and commonly aggressive pediatric cancer.
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The potential of the high-affinity CXCR4 antagonist BL-8040 as a monotherapy-mobilizing agent and its derived graft composition and quality were evaluated in a phase I clinical study in healthy ...volunteers (NCT02073019).
The first part of the study was a randomized, double-blind, placebo-controlled dose escalation phase. The second part of the study was an open-label phase, in which 8 subjects received a single injection of BL-8040 (1 mg/kg) and approximately 4 hours later underwent a standard leukapheresis procedure. The engraftment potential of the purified mobilized CD34
cells was further evaluated by transplanting the cells into NSG immunodeficient mice.
BL-8040 was found safe and well tolerated at all doses tested (0.5-1 mg/kg). The main treatment-related adverse events were mild to moderate. Transient injection site and systemic reactions were mitigated by methylprednisolone, paracetamol, and promethazine pretreatment. In the first part of the study, BL-8040 triggered rapid and substantial mobilization of WBCs and CD34
cells in all tested doses. Four hours postdose, the count rose to a mean of 8, 37, 31, and 35 cells/μL (placebo, 0.5, 0.75, and 1 mg/kg, respectively). FACS analysis revealed substantial mobilization of immature dendritic, T, B, and NK cells. In the second part, the mean CD34
cells/kg collected were 11.6 × 10
cells/kg. The graft composition was rich in immune cells.
The current data demonstrate that BL-8040 is a safe and effective monotherapy strategy for the collection of large amounts of CD34
cells and immune cells in a one-day procedure for allogeneic HSPC transplantation.
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Treatment of Diffuse Large B Cell Lymphoma (DLBCL) patients with rituximab and the CHOP treatment regimen is associated with frequent intrinsic and acquired resistance. However, treatment with a CD47 ...monoclonal antibody in combination with rituximab yielded high objective response rates in patients with relapsed/refractory DLBCL in a phase I trial. Here, we report on a new bispecific and fully human fusion protein comprising the extracellular domains of SIRPα and 4-1BBL, termed DSP107, for the treatment of DLBCL. DSP107 blocks the CD47:SIRPα 'don't eat me' signaling axis on phagocytes and promotes innate anticancer immunity. At the same time, CD47-specific binding of DSP107 enables activation of the costimulatory receptor 4-1BB on activated T cells, thereby, augmenting anticancer T cell immunity.
Using macrophages, polymorphonuclear neutrophils (PMNs), and T cells of healthy donors and DLBCL patients, DSP107-mediated reactivation of immune cells against B cell lymphoma cell lines and primary patient-derived blasts was studied with phagocytosis assays, T cell activation and cytotoxicity assays. DSP107 anticancer activity was further evaluated in a DLBCL xenograft mouse model and safety was evaluated in cynomolgus monkey.
Treatment with DSP107 alone or in combination with rituximab significantly increased macrophage- and PMN-mediated phagocytosis and trogocytosis, respectively, of DLBCL cell lines and primary patient-derived blasts. Further, prolonged treatment of in vitro macrophage/cancer cell co-cultures with DSP107 and rituximab decreased cancer cell number by up to 85%. DSP107 treatment activated 4-1BB-mediated costimulatory signaling by HT1080.4-1BB reporter cells, which was strictly dependent on the SIRPα-mediated binding of DSP107 to CD47. In mixed cultures with CD47-expressing cancer cells, DSP107 augmented T cell cytotoxicity in vitro in an effector-to-target ratio-dependent manner. In mice with established SUDHL6 xenografts, the treatment with human PBMCs and DSP107 strongly reduced tumor size compared to treatment with PBMCs alone and increased the number of tumor-infiltrated T cells. Finally, DSP107 had an excellent safety profile in cynomolgus monkeys.
DSP107 effectively (re)activated innate and adaptive anticancer immune responses and may be of therapeutic use alone and in combination with rituximab for the treatment of DLBCL patients.
The p53 tumor suppressor protein has a major role in protecting genome integrity. Under normal circumstances Mdmx and Mdm2 control the activity of p53. Both proteins inhibit the transcriptional ...regulation by p53, while Mdm2 also functions as an E3 ubiquitin ligase to target both p53 and Mdmx for proteasomal degradation. HAUSP counteracts the destabilizing effect of Mdm2 by direct deubiquitination of p53. Subsequently, HAUSP was shown to deubiquitinate Mdm2 and Mdmx, thereby stabilizing these proteins. The ATM protein kinase is a key regulator of the p53 pathway in response to double strand breaks (DSBs) in the DNA. ATM fine-tunes p53's response to DNA damage by directly phosphorylating it, by regulating additional post-translational modifications of this protein, and by affecting two p53 regulators: Mdm2 and Mdmx. ATM directly and indirectly induces Mdm2 and Mdmx phosphorylation, resulting in decreased activity and stability of these proteins. We recently provided a mechanism for the reduced stability of Mdm2 and Mdmx by showing that ATM-dependent phosphorylation lowers their affinity for the deubiquitinating enzyme HAUSP. Altogether, the emerging picture portrays an elaborate, but fine-tuned, ATM-mediated control of p53 activation and stabilization following DNA damage. Further insight into the mechanism by which ATM switches the interactions between HAUSP, Mdmx, Mdm2 and p53, to favor p53 activation may offer new tools for therapeutic intervention in the p53 pathway for cancer treatment.
Maintenance of genomic stability depends on the DNA damage response, an extensive signaling network that is activated by DNA lesions such as double-strand breaks (DSBs). The primary activator of the ...mammalian DSB response is the nuclear protein kinase ataxia-telangiectasia, mutated (ATM), which phosphorylates key players in various arms of this network. The activation and stabilization of the p53 protein play a major role in the DNA damage response and are mediated by ATM-dependent posttranslational modifications of p53 and Mdm2, a ubiquitin ligase of p53. p53's response to DNA damage also depends on Mdm2-dependent proteolysis of Mdmx, a homologue of Mdm2 that represses p53's transactivation function. Here we show that efficient damage-induced degradation of human Hdmx depends on functional ATM and at least three sites on the Hdmx that are phosphorylated in response to DSBs. One of these sites, S403, is a direct ATM target. Accordingly, each of these sites is important for Hdm2-mediated ubiquitination of Hdmx after DSB induction. These results demonstrate a sophisticated mechanism whereby ATM fine-tunes the optimal activation of p53 by simultaneously modifying each player in the process.
RB60 is an atypical protein disulfide isomerase (PDI) that functions as a member of a redox regulatory protein complex controlling translation in the chloroplast of Chlamydomonas reinhardtii, but ...also contains a C-terminal endoplasmic reticulum (ER) retention signal, -KDEL. Here, we show by fluorescence microscopy that RB60 resides in the chloroplast but also outside of the chloroplast colocalized with BiP, an ER marker protein. RB60 accumulates in microsomes that exhibit a typical ER magnesium-shift, and cotranslationally translocates into ER microsomes. The first 50-aa leader of RB60 is sufficient for both chloroplast and ER targeting. The leader is cleaved upon translocation into the ER, whereas it remains intact after import to the chloroplast. The leader sequence also contains an acidic domain that appears necessary for the protein's association with the thylakoid membranes. Based on these and additional results, we propose that the dual localization of RB60 occurs via the two conserved transport mechanisms, to the chloroplast and to the ER, that the chloroplast RB60 most likely carries an additional function in the ER, and that its mode of transport, including the differential cleavage of its N terminus, plays an important role in its suborganellar localization and organellar-specific function.
The protein kinase ATM (ataxia-telangiectasia mutated) activates the cellular response to double strand breaks (DSBs), a highly cytotoxic DNA lesion. ATM is activated by DSBs and in turn ...phosphorylates key players in numerous damage response pathways. ATM is missing or inactivated in the autosomal recessive disorder ataxia-telangiectasia (A-T), which is characterized by neuronal degeneration, immunodeficiency, genomic instability, radiation sensitivity, and cancer predisposition. The predominant symptom of A-T is a progressive loss of movement coordination due to ongoing degeneration of the cerebellar cortex and peripheral neuropathy. A major deficiency in understanding A-T is the lack of information on the role of ATM in neurons. It is unclear whether the ATM-mediated DSB response operates in these cells similarly to proliferating cells. Furthermore, ATM was reported to be cytoplasmic in neurons and suggested to function in these cells in capacities other than the DNA damage response. Recently we obtained genetic molecular evidence that the neuronal degeneration in A-T does result from defective DNA damage response. We therefore undertook to investigate this response in a model system of human neuron-like cells (NLCs) obtained by neuronal differentiation in culture. ATM was largely nuclear in NLCs, and their ATM-mediated responses to DSBs were similar to those of proliferating cells. Knocking down ATM did not interfere with neuronal differentiation but abolished ATM-mediated damage responses in NLCs. We concluded that nuclear ATM mediates the DSB response in NLCs similarly to in proliferating cells. Attempts to understand the neurodegeneration in A-T should be directed to investigating the DSB response in the nervous system.
The mainstay of treatment for Diffuse Large B cell Lymphoma (DLBCL) is conventional chemotherapy combined with anti-CD20 monoclonal antibody rituximab (RTX). However, a subset of patients is ...refractory to treatment and between 20 to 50% of patients will, after experiencing an initial complete response (CR), develop resistance to treatment and relapse with poor prognosis. Therefore, additional therapeutic options are urgently needed. In this respect, combination of RTX treatment with CD47 monoclonal antibodies has yielded high objective response rates in patients with relapsed/refractory DLBCL in recent phase I trials. Interestingly, although CD47-targeting specifically activates the innate immune system, treatment with CD47 antibodies augments antigen-presentation in the context of MHC by macrophages and dendritic cells, thereby, triggering cross-priming of T cells in murine models. This T cell activation was pivotal in vivo efficacy in these murine models. Thus, a clear rationale exists for the development of novel therapeutics that exploit CD47 checkpoint inhibition while simultaneously stimulating anticancer T cell immunity.
Here, we report on such an immunotherapeutic, termed Dual Signaling Protein 107 (DSP107), comprising a computationally-designed fusion of human soluble SIRPα and 4-1BBL. DSP107 was designed to bind to CD47 on cancer cells and block the CD47/SIRPα inhibitory signal delivered to phagocytes. Further, DSP107 was designed to bind to 4-1BB, a costimulatory receptor upregulated upon TCR/MHC interaction and a validated surrogate marker for the tumor-reactive subset of T cells in tumor tissue. Since 4-1BB activation by soluble 4-1BBL requires cross-linking, DSP107 will trigger 4-1BB signaling only after binding to CD47. This CD47-mediated surface immobilization of DSP107 enables delivery of the 4-1BBL-4-1BB costimulatory signal to tumor localized T cells. This dual immunomodulatory effect of DSP107 is designed to unleash both innate and adaptive immune responses targeted to the tumor site (Figure 1).
Treatment with DSP107 alone or in combination with RTX triggered significant phagocytosis of a panel of DLBCL cancer cell lines as well as primary patient-derived DLBCL cells by macrophages and neutrophils within 3 hours. Further, after longer term incubation of 24h an ~85% reduction in remaining tumor cells was detected upon combined DSP107 and RTX treatment compared to medium control, whereas an increase in apoptosis was detected in the remaining cells. The pro-phagocytic activity of DSP107 was equal to both CD47 antibody as well as SIRPα:Fc. Simultaneously, binding of DSP107 to CD47 enabled 4-1BB costimulatory signaling by reporter cell line HT1080.4-1BB only on CD47-coated plates. Further, in co-cultures of HT1080.4-1BB with CHO.wt and CHO cells ectopically expressing human CD47, 41BB activation was only observed after binding of DSP107 to human CD47. This activation of 4-1BB costimulatory signaling triggered prominent T cell proliferation in mixed cultures of isolated peripheral blood T cells with cancer cells and augmented T cell cytotoxicity in vitro in a concentration and Effector to Target ratio dependent manner. Finally, injection of peripheral blood mononuclear cells (PBMCs) in mice with established SUDHL6 xenografts and simultaneous treatment with DSP107 triggered a strong reduction in tumor size compared to treatment with PBMCs alone.
In conclusion, DSP107 clearly inhibits the CD47/SIRPα inhibitory axis and augments phagocytic removal of cancer cells by innate immune cells. Moreover, binding of DSP107 to CD47 enables the 4-1BBL-mediated costimulation of antitumor T cell cytotoxicity. Thus, DSP107 activates both innate and adaptive anticancer immunity and may be of use for the treatment of DLBCL alone or in combination with RTX.
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Cendrowicz:Kahr Medical: Research Funding. Jacob:Kahr Medical: Current Employment. Greenwald:Kahr Medical: Current Employment. Tamir:Kahr Medical: Current Employment. Huls:Kahr Medical: Research Funding. Foley-Comer:Kahr Medical: Current Employment. Pereg:Kahr Medical: Current Employment. Chajut:Kahr Medical: Current Employment. Peled:Kahr Medical: Consultancy. Bremer:Kahr Medical: Consultancy, Research Funding.
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