Search

In many tumor cell types, ionizing radiation or DNA-damaging anticancer drugs enhance sensitivity to death receptor-mediated apoptosis, which is of clinical interest. APO010, a form of CD95/Fas ligand is currently in a phase I trial in patients with solid tumors. To analyze the potential of combined modality treatment with APO010, we used p53-mutant Jurkat T leukemic cells, in which the mitochondrial pathway was blocked by Bcl-2 overexpression. These cells were strongly sensitized to APO010 by pretreatment with ionizing – or UV radiation, etoposide, histone deacetylase – or proteasome inhibitors. These stimuli alone did not induce apoptosis in J16-Bcl-2 cells. Sensitization could not be explained by the overruling of mitochondrial resistance imposed by Bcl-2, upregulation of CD95 membrane levels or modulation of inhibitor of apoptosis proteins. Rather, the stimuli commonly downregulated c-FLIPL/S protein levels, which was causally related to the sensitization: deliberate c-FLIPL/S downregulation by RNA interference largely overruled the capacity of the various stimuli to sensitize Jurkat-Bcl-2 cells to apoptotic execution by APO010. In p53-mutant, Bcl-2 overexpressing HCT-15 colon carcinoma cells, c-FLIP downregulation correlated with sensitization to APO010 for some, but not all stimuli. We conclude that c-FLIP downregulation represents a mechanism by which diverse anticancer regimens can facilitate tumor cell execution by CD95/Fas through the direct pathway of caspase activation. [ABSTRACT FROM AUTHOR]

We examined candidate biomarkers for efficacy outcomes in hospitalized COVID-19 patients who were treated with sirukumab, an IL-6 neutralizing antibody, in a randomized, double-blind, placebo-controlled, phase 2 trial. Between May 2020 and March 2021, 209 patients were randomized (sirukumab, n = 139; placebo, n = 70); 112 had critical COVID-19. Serum biomarkers were evaluated for the pharmacodynamic effect of sirukumab and for their potential prognostic and predictive effect on time to sustained clinical improvement up to Day 28, clinical improvement at Day 28, and mortality at Day 28. The absence of detectable IL-4 increase and smaller increases in CCL13 post-baseline were most significantly associated with better response to sirukumab (versus placebo) treatment for all clinical efficacy outcomes tested, especially in patients with critical COVID-19. These data suggest that patients with critical COVID-19 without detectable sirukumab-induced IL-4 levels are more likely to benefit from sirukumab treatment. ClinicalTrials.gov Identifier: NCT04380961., (© 2024. The Author(s).)

Background: Upregulation of IL-6 has been associated with worse prognosis in COVID-19 patients. Impact on IL-6 signalling has mostly been limited to clinical outcomes in IL-6 receptor antagonist trials., Methods: We performed a phase 2, randomised, double-blind, placebo-controlled trial (NCT04380961) of US-based hospitalised adults (<85 years) with laboratory-confirmed SARS-CoV-2 infection and severe (low levels of supplemental oxygen) or critical disease (high levels of oxygen supplementation). Patients received sirukumab 5 mg/kg or placebo single dose IV on Day 1 plus standard of care. The primary endpoint was time to sustained clinical improvement up to Day 28 based on an ordinal scale. Secondary endpoints included clinical improvement, all-cause mortality, and safety. Following an interim analysis, the protocol was amended to only recruit patients with critical COVID-19., Findings: From May 2020 to March 2021, 209 patients were randomised; 112 had critical disease (72 sirukumab, 40 placebo) at baseline. Median time to sustained clinical improvement in critical patients was 17 and 23 days in the sirukumab and placebo groups (HR, 1∙1; 95% CI, 0∙66-1∙88; p > 0∙05). At Day 28, 59∙4% versus 55∙0% of patients achieved clinical improvement with sirukumab versus placebo and rates of all-cause mortality were 24∙6% versus 30∙0%, respectively. Rates of grade ≥3 adverse events were comparable between the sirukumab and placebo groups (25∙9% vs 32∙9%; all patients)., Interpretation: In critical COVID-19 patients who received sirukumab, there was no statistically significant difference in time to sustained clinical improvement versus placebo despite objective sequestration of circulating IL-6, questioning IL-6 as a key therapeutic target in COVID-19., Competing Interests: Declaration of Competing Interest Robert L. Gottlieb served as coordinating national principal investigator and as a consultant for this trial. He reports service on scientific advisory boards for AbbVie, AstraZeneca, Eli Lilly, Gilead Sciences, GSK, and Roche, and consulting via his institution for Kinevant Sciences, also related to COVID-19. Service on speakers bureau with Alnylam Pharmaceuticals and Pfizer, consultancy to Alnylam, research support from CareDx, and a gift-in-kind to his institution from Gilead Sciences to support NCT03383419 are also reported, all outside the submitted work. Meredith Clement has received research support (grants to institution) from Gilead Sciences and ViiV Healthcare, has served on advisory boards for Roche Diagnostics Corporation and ViiV Healthcare. Paul Cook is a PI for the following: NIH, Janssen, Gilead, ViiV, Seres, and Finch. Audra Deveikis, Kap Sum Foong, Philip Robinson, and Cedric W. Spak have nothing to declare. Jihad Slim serves on speakers bureaus for Gilead, ViiV, Merck, Janssen, AbbVie, and Thera. Katleen Callewaert is an employee of Janssen Pharmaceutica NV. Annemie Buelens, Sandra De Meyer, Liesbeth Van Wesenbeeck, and Erika Van Landuyt are employees of Janssen Pharmaceutica NV and own stock in Johnson & Johnson. Wai Ling Mo is an employee of Janssen-Cilag Limited. Inge Verbrugge and Magda Opsomer were employees of Janssen Pharmaceutica NV at the time of the study. Yanli Zhuang and Jacon Chien were employees of Janssen Research & Development, LLC at the time of the study., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Radiotherapy (RT) is considered immunogenic, but clinical data demonstrating RT-induced T cell priming are scarce. Here, we show in a mouse tumor model representative of human lymphocyte-depleted cancer that RT enhanced spontaneous priming of thymus-derived (FOXP3+Helios+) Tregs by the tumor. These Tregs acquired an effector phenotype, populated the tumor, and impeded tumor control by a simultaneous, RT-induced CD8+ cytotoxic T cell (CTL) response. Combination of RT with CTLA-4 or PD-1 blockade, which enables CD28 costimulation, further increased this Treg response and failed to improve tumor control. We discovered that upon RT, the CD28 ligands CD86 and CD80 differentially affected the Treg response. CD86, but not CD80, blockade prevented the effector Treg response, enriched the tumor-draining lymph node migratory conventional DCs that were positive for PD-L1 and CD80 (PD-L1+CD80+), and promoted CTL priming. Blockade of CD86 alone or in combination with PD-1 enhanced intratumoral CTL accumulation, and the combination significantly increased RT-induced tumor regression and OS. We advise that combining RT with PD-1 and/or CTLA-4 blockade may be counterproductive in lymphocyte-depleted cancers, since these interventions drive Treg responses in this context. However, combining RT with CD86 blockade may promote the control of such tumors by enabling a CTL response.

Background: Chronic hepatitis B (CHB) is responsible for major disease burden worldwide. However, the number of available therapies is limited; cure remains an elusive goal. JNJ-64794964 (JNJ-4964) is an oral toll-like receptor-7 (TLR7) agonist being evaluated for the treatment of CHB. Here, we investigated the capacity of JNJ-4964 to induce transcriptomic and immune cell changes in peripheral blood in healthy volunteers., Methods: Peripheral blood was collected in the JNJ-4964 first-in-human phase 1 trial at multiple time points to assess transcriptomics and changes in frequency and phenotype of peripheral-blood mononuclear cells. Correlation of changes to JNJ-4964 exposure (C max ) and changes in cytokine levels (C-X-C motif chemokine ligand 10 [CXCL10] and interferon alpha [IFN-α]) were evaluated., Results: Fifty-nine genes, mainly interferon-stimulated genes, were up-regulated between 6 hours and 5 days after JNJ-4964 administration. JNJ-4964 increased frequencies of CD69, CD134, CD137, and/or CD253-expressing natural killer (NK) cells, indicative of NK cell activation. These changes correlated with C max , increase of CXCL10, and induction of IFN-α and were observed at IFN-α levels that are associated with no/acceptable flu-like adverse events. JNJ-4964 administration resulted in increased frequencies of CD86-expressing B cells, indicative of B-cell activation. These changes were predominantly observed at high IFN-α levels, which are associated with flu-like adverse events., Conclusions: JNJ-4964 administration led to changes in transcriptional profiles and immune cell activation phenotype, particularly for NK cells and B cells. Together, these changes could represent a set of biomarkers for the characterization of the immune response in CHB patients receiving TLR7 agonists.

Background: JNJ-4964 is a TLR7 agonist, which, via a type I interferon (IFN)-dependent mechanism, may enhance host immunity suppressed by persistent exposure to hepatitis B antigens in chronic hepatitis B., Methods: PK and PD data were pooled from 2 studies involving 90 participants ( n = 74 JNJ-4964, dose range 0.2-1.8 mg; n = 16 placebo) in a fasted state. Food effects on PK were studied in 24 participants (1.2 or 1.25 mg). A population PK model and PK/PD models were developed to characterize the effect of JNJ-4964 plasma levels on the time course of IFN-α, IFN-γ-inducible protein 10 (IP-10 or CXCL10), IFN-stimulated gene 15 ( ISG15 ), neopterin and lymphocytes following single and weekly dosing in healthy adults. Covariate effects, circadian rhythms and negative feedback were incorporated in the models., Results: A 3-compartment linear PK model with transit absorption adequately described JNJ-4964 PK. Bioavailability was 44.2% in fed state relative to fasted conditions. Indirect response models with maximum effect (E max ) stimulation on production rate constant (k in ) described IFN-α, IP-10, ISG15 and neopterin, while a precursor-dependent indirect response model with inhibitory effect described the transient lymphocyte reduction. E max , EC 50 and γ (steepness) estimates varied according to PD markers, with EC 50 displaying substantial between-subject variability. Female and Asian race exhibited lower EC 50 , suggesting higher responsiveness., Conclusions: PK/PD models well characterized the time course of immune system markers in healthy adults. Our results supported sex and race as covariates on JNJ-4964 responsiveness, as well as circadian rhythms and negative feedback as homeostatic mechanisms that are relevant in TLR7-induced type I IFN responses.

Autotaxin (ATX; ENPP2) produces lysophosphatidic acid (LPA) that regulates multiple biological functions via cognate G protein-coupled receptors LPAR1-6. ATX/LPA promotes tumor cell migration and metastasis via LPAR1 and T cell motility via LPAR2, yet its actions in the tumor immune microenvironment remain unclear. Here, we show that ATX secreted by melanoma cells is chemorepulsive for tumor-infiltrating lymphocytes (TILs) and circulating CD8 + T cells ex vivo, with ATX functioning as an LPA-producing chaperone. Mechanistically, T cell repulsion predominantly involves Gα 12/13 -coupled LPAR6. Upon anti-cancer vaccination of tumor-bearing mice, ATX does not affect the induction of systemic T cell responses but, importantly, suppresses tumor infiltration of cytotoxic CD8 + T cells and thereby impairs tumor regression. Moreover, single-cell data from melanoma tumors are consistent with intratumoral ATX acting as a T cell repellent. These findings highlight an unexpected role for the pro-metastatic ATX-LPAR axis in suppressing CD8 + T cell infiltration to impede anti-tumor immunity, suggesting new therapeutic opportunities., Competing Interests: Declaration of interests Z.J. is an employee and shareholder of iOnctura SA, a company developing an ATX inhibitor for use in cancer., (Copyright © 2021 The Author(s). Published by Elsevier Inc. All rights reserved.)

Background: For many cancer types, including colorectal carcinoma (CRC), combined modality treatments have shown to improve outcome, but are frequently associated with significant toxicity, illustrating the need for new therapeutic approaches. Based on preclinical data, TRAIL receptor agonists appeared to be promising agents for cancer therapy especially in combination with DNA damaging regimens. Here, we present the combination of the second-generation TRAIL receptor agonist APG-880 with radiation in a new and clinically relevant 3D model system., Methods: To investigate the effect of APG-880 in combination with radiation we performed short-term cytotoxicity and long-term clonogenic survival assays in established CRC cell lines, and in tumor organoids derived from colon cancer patients., Results: APG-880 is a potent inducer of apoptosis in CRC cell lines and in patient-derived CRC organoids. Furthermore, a supra-additive effect on cytotoxicity was found when APG-880 and radiation were combined simultaneously, with combination indices around 0.7. Lastly, in the long-term survival assays, we demonstrated a radiosensitizing effect of APG-880 with dose enhancement factors between 1.3 and 1.5., Conclusions: In a new, clinically relevant CRC-organoid model system we demonstrated a more than additive combined effect between the second-generation TRAIL receptor agonist APG-880 and radiation., Competing Interests: This work was partially supported by a research grant from AbbVie Inc. The funding source had no role in the study design. AbbVie Inc. participated in the interpretation of data, review, and approval of this publication., (© 2020 The Author(s).)

To increase cancer immunotherapy success, PD-1 blockade must be combined with rationally selected treatments. Here, we examined, in a poorly immunogenic mouse breast cancer model, the potential of antibody-based immunomodulation and conventional anticancer treatments to collaborate with anti-PD-1 treatment. One requirement to improve anti-PD-1-mediated tumor control was to promote tumor-specific cytotoxic T-cell (CTL) priming, which was achieved by stimulating the CD137 costimulatory receptor. A second requirement was to overrule PD-1-unrelated mechanisms of CTL suppression in the tumor microenvironment (TME). This was achieved by radiotherapy and cisplatin treatment. In the context of CD137/PD-1-targeting immunotherapy, radiotherapy allowed for tumor elimination by altering the TME, rather than intrinsic CTL functionality. Combining this radioimmunotherapy regimen with low-dose cisplatin improved CTL-dependent regression of a contralateral tumor outside the radiation field. Thus, systemic tumor control may be achieved by combining immunotherapy protocols that promote T-cell priming with (chemo)radiation protocols that permit CTL activity in both the irradiated tumor and (occult) metastases., (©2019 American Association for Cancer Research.)

Despite the development of novel drugs, the prospects for many patients with acute myeloid leukemia (AML) remain dismal. This study reveals that the selective inhibitor of RNA polymerase I (Pol I) transcription, CX-5461, effectively treats aggressive AML, including mixed-lineage leukemia-driven AML, and outperforms standard chemotherapies. In addition to the previously characterized mechanism of action of CX-5461 (ie, the induction of p53-dependent apoptotic cell death), the inhibition of Pol I transcription also demonstrates potent efficacy in p53null AML in vivo. This significant survival advantage in both p53WT and p53null leukemic mice treated with CX-5461 is associated with activation of the checkpoint kinases 1/2, an aberrant G2/M cell-cycle progression and induction of myeloid differentiation of the leukemic blasts. The ability to target the leukemic-initiating cell population is thought to be essential for lasting therapeutic benefit. Most strikingly, the acute inhibition of Pol I transcription reduces both the leukemic granulocyte-macrophage progenitor and leukemia-initiating cell (LIC) populations, and suppresses their clonogenic capacity. This suggests that dysregulated Pol I transcription is essential for the maintenance of their leukemia-initiating potential. Together, these findings demonstrate the therapeutic utility of this new class of inhibitors to treat highly aggressive AML by targeting LICs., (© 2017 by The American Society of Hematology.)

Current genetically-engineered mouse melanoma models are often based on Tyr::CreER T2 -controlled MAPK pathway activation by the BRAF V600E mutation and PI3K pathway activation by loss of PTEN. The major drawback of these models is the occurrence of spontaneous tumors caused by leakiness of the Tyr::CreER T2 system, hampering long-term experiments. To address this problem, we investigated several approaches to optimally provide local delivery of Cre recombinase, including injection of lentiviral particles, DNA tattoo administration and particle-mediated gene transfer, to induce melanomas in Pten LoxP/LoxP ; Braf CA/+ mice lacking the Tyr::CreER T2 allele. We found that dermal delivery of the Cre recombinase gene under the control of a non-specific CAG promoter induced the formation of melanomas, but also keratoacanthoma and squamous cell carcinomas. Delivery of Cre recombinase DNA under the control of melanocyte-specific promoters in Pten LoxP/LoxP ; Braf CA/+ mice resulted in sole melanoma induction. The growth rate and histological features of the induced tumors were similar to 4-hydroxytamoxifen-induced tumors in Tyr::CreER T2 ; Pten LoxP/LoxP ; Braf CA/+ mice, while the onset of spontaneous tumors was prevented completely. These novel induction methods will allow long-term experiments in mouse models of skin malignancies., Competing Interests: The authors declare no conflict of interest.

In healthy individuals, immune-checkpoint molecules prevent autoimmune responses and limit immune cell-mediated tissue damage. Tumors frequently exploit these molecules to evade eradication by the immune system. Over the past years, immune-checkpoint blockade of cytotoxic T lymphocyte antigen-4 and programed death-1 emerged as promising strategies to activate antitumor cytotoxic T cell responses. Although complete regression and long-term survival is achieved in some patients, not all patients respond. This review describes promising, novel combination approaches involving immune-checkpoint blockade in the context of the cancer-immunity cycle, aimed at increasing response rates to the single treatments. Specifically, we discuss combinations that promote antigen release and presentation, that further amplify T cell activation, that inhibit trafficking of regulatory T cells or MSDCs, that stimulate intratumoral T cell infiltration, that increase cancer recognition by T cells, and that stimulate tumor killing.

Immunotherapy of advanced melanoma with CTLA-4 or PD-1/PD-L1 checkpoint blockade induces in a proportion of patients long durable responses. In contrast, targeting the MAPK-pathway by selective BRAF and MEK inhibitors induces high response rates, but most patients relapse. Combining targeted therapy with immunotherapy is proposed to improve the long-term outcomes of patients. Preclinical data endorsing this hypothesis are accumulating. Inhibition of the PI3K-Akt-mTOR pathway may be a promising treatment option to overcome resistance to MAPK inhibition and for additional combination with immunotherapy. We therefore evaluated to which extent dual targeting of the MAPK and PI3K-Akt-mTOR pathways affects tumor immune infiltrates and whether it synergizes with PD-1 checkpoint blockade in a BRAF V600E /PTEN -/- -driven melanoma mouse model. Short-term dual BRAF + MEK inhibition enhanced tumor immune infiltration and improved tumor control when combined with PD-1 blockade in a CD8 + T cell dependent manner. Additional PI3K inhibition did not impair tumor control or immune cell infiltration and functionality. Analysis of on-treatment samples from melanoma patients treated with BRAF or BRAF + MEK inhibitors indicates that inhibitor-mediated T cell infiltration occurred in all patients early after treatment initiation but was less frequent found in on-treatment biopsies beyond day 15. Our findings provide a rationale for clinical testing of short-term BRAF + MEK inhibition in combination with immune checkpoint blockade, currently implemented at our institutes. Additional PI3K inhibition could be an option for BRAF + MEK inhibitor resistant patients that receive targeted therapy in combination with immune checkpoint blockade.

T cell checkpoint blockade with antibodies targeting programmed cell death (ligand)-1 (PD-1/PD-L1) and/or cytotoxic T lymphocyte-antigen 4 (CTLA-4) has improved therapy outcome in melanoma patients. However, a considerable proportion of patients does not benefit even from combined α-CTLA-4 and α-PD-1 therapy. We therefore examined to which extent T cell (co)stimulation and/or stereotactic body radiation therapy (SBRT) could further enhance the therapeutic efficacy of T cell checkpoint blockade in a genetically engineered mouse melanoma model that is driven by PTEN-deficiency, and BRAFV600 mutation, as in human, but lacks the sporadic UV-induced mutations. Tumor-bearing mice were treated with different combinations of immunomodulatory antibodies (α-CTLA-4, α-PD-1, α-CD137) or interleukin-2 (IL-2) alone or in combination with SBRT. None of our immunotherapeutic approaches (alone or in combination) had any anti-tumor efficacy, while SBRT alone delayed melanoma outgrowth. However, α-CD137 combined with α-PD-1 antibodies significantly enhanced the anti-tumor effect of SBRT, while the anti-tumor effect of SBRT was not enhanced by interleukin-2, or the combination of α-CTLA-4 and α-PD-1. We conclude that α-CD137 and α-PD-1 antibodies were most effective in enhancing SBRT-induced tumor growth delay in this mouse melanoma model, outperforming the ability of IL-2, or the combination of α-CTLA-4 and α-PD-1 to synergize with SBRT. Given the high mutational load and increased immunogenicity of human melanoma with the same genotype, our findings encourage testing α-CD137 and α-PD-1 alone or in combination with SBRT clinically, particularly in patients refractory to α-CTLA-4 and/or α-PD-1 therapy.

Translocations of the mixed lineage leukemia (MLL) gene occur in 60% to 80% of all infant acute leukemias and are markers of poor prognosis. MLL-AF9 and other MLL fusion proteins aberrantly recruit epigenetic regulatory proteins, including histone deacetylases (HDAC), histone methyltransferases, bromodomain-containing proteins, and transcription elongation factors to mediate chromatin remodeling and regulate tumorigenic gene expression programs. We conducted a small-molecule inhibitor screen to test the ability of candidate pharmacologic agents targeting epigenetic and transcriptional regulatory proteins to induce apoptosis in leukemic cells derived from genetically engineered mouse models of MLL-AF9-driven acute myeloid leukemia (AML). We found that the CDK inhibitor dinaciclib and HDAC inhibitor panobinostat were the most potent inducers of apoptosis in short-term in vitro assays. Treatment of MLL-rearranged leukemic cells with dinaciclib resulted in rapidly decreased expression of the prosurvival protein Mcl-1, and accordingly, overexpression of Mcl-1 protected AML cells from dinaciclib-induced apoptosis. Administration of dinaciclib to mice bearing MLL-AF9-driven human and mouse leukemias elicited potent antitumor responses and significantly prolonged survival. Collectively, these studies highlight a new therapeutic approach to potentially overcome the resistance of MLL-rearranged AML to conventional chemotherapies and prompt further clinical evaluation of CDK inhibitors in AML patients harboring MLL fusion proteins., (©2015 American Association for Cancer Research.)

Radiotherapy is a successful treatment modality for localized cancer. Our group has been exploring radiotherapy in combination with immunotherapy (radioimmunotherapy) to enhance systemic antitumor responses. Previously, we have shown that when local radiotherapy was combined with monoclonal antibodies (mAbs) (that enable T-cell responses by engaging costimulation [anti (α)-CD137] and blocking coinhibition [α-PD-1] [corrected], up to 100% of mice bearing established syngeneic AT-3 mammary tumors were cured, but single modality treatments were not curative. Here, we investigated the molecular mechanisms underlying responses to this radioimmunotherapy approach. We observed that inhibition of signaling through the mammalian target of rapamycin (mTOR) pathway during the first 10 days of treatment severely impaired the curative effect of radioimmunotherapy, at least in part by reducing MHC class I expression on tumor cells, reducing dendritic cell (DC) activation status and CD8+ T-cell function. This data indicates that the efficacy of this type of radioimmunotherapy approach involves mTOR signaling and therefore, mTOR inhibitory drugs may impede the efficacy of similar radioimmunotherapy approaches in humans.

Epigenetic modifying enzymes such as histone deacetylases (HDACs), p300, and PRMT1 are recruited by AML1/ETO, the pathogenic protein for t(8;21) acute myeloid leukemia (AML), providing a strong molecular rationale for targeting these enzymes to treat this disease. Although early phase clinical assessment indicated that treatment with HDAC inhibitors (HDACis) may be effective in t(8;21) AML patients, rigorous preclinical studies to identify the molecular and biological events that may determine therapeutic responses have not been performed. Using an AML mouse model driven by expression of AML1/ETO9a (A/E9a), we demonstrated that treatment of mice bearing t(8;21) AML with the HDACi panobinostat caused a robust antileukemic response that did not require functional p53 nor activation of conventional apoptotic pathways. Panobinostat triggered terminal myeloid differentiation via proteasomal degradation of A/E9a. Importantly, conditional A/E9a deletion phenocopied the effects of panobinostat and other HDACis, indicating that destabilization of A/E9a is critical for the antileukemic activity of these agents.

The eleven members of the membrane-associated RING-CH (MARCH) ubiquitin ligase family are relatively unexplored. Upon exogenous (over)expression, a number of these ligases can affect the trafficking of membrane molecules. However, only for MARCH-1 endogenous functions have been demonstrated. For the other endogenous MARCH proteins, no functions or substrates are known. We report here that TRAIL-R1 is a physiological substrate of the endogenous MARCH-8 ligase. Human TRAIL-R1 and R2 play a role in immunosurveillance and are targets for cancer therapy, because they selectively induce apoptosis in tumor cells. We demonstrate that TRAIL-R1 is down-regulated from the cell surface, with great preference over TRAIL-R2, by exogenous expression of MARCH ligases that are implicated in endosomal trafficking, such as MARCH-1 and -8. MARCH-8 attenuated TRAIL-R1 cell surface expression and apoptosis signaling by virtue of its ligase activity. This suggested that ubiquitination of TRAIL-R1 was instrumental in its down-regulation by MARCH-8. Indeed, in cells with endogenous MARCH expression, TRAIL-R1 was ubiquitinated at steady-state, with the conserved membrane-proximal lysine 273 as one of the potential acceptor sites. This residue was also essential for the interaction of TRAIL-R1 with MARCH-1 and MARCH-8 and its down-regulation by these ligases. Gene silencing identified MARCH-8 as the endogenous ligase that ubiquitinates TRAIL-R1 and attenuates its cell surface expression. These findings reveal that endogenous MARCH-8 regulates the steady-state cell surface expression of TRAIL-R1.

The development and use of combination immunotherapy-based anticancer regimens is at an early but clearly exciting stage. We now demonstrate that the antibody-based co-targeting of multiple immunostimulatory and/or inhibitory pathways can be used safely and effectively in combination with single dose or fractionated radiotherapy to cure mice bearing established mammary tumors.

It is becoming increasingly evident that radiotherapy may benefit from coincident or subsequent immunotherapy. In this study, we examined whether the antitumor effects of radiotherapy, in established triple-negative breast tumors could be enhanced with combinations of clinically relevant monoclonal antibodies (mAb), designed to stimulate immunity [anti-(α)-CD137, α-CD40] or relieve immunosuppression [α-programmed death (PD)-1]. While the concomitant targeting of the costimulatory molecules CD137 and CD40 enhanced the antitumor effects of radiotherapy and promoted the rejection of subcutaneous BALB/c-derived 4T1.2 tumors, this novel combination was noncurative in mice bearing established C57BL/6-derived AT-3 tumors. We identified PD-1 signaling within the AT-3 tumors as a critical limiting factor to the therapeutic efficacy of α-CD137 therapy, alone and in combination with radiotherapy. Strikingly, all mice bearing established orthotopic AT-3 mammary tumors were cured when α-CD137 and α-PD-1 mAbs were combined with single- or low-dose fractionated radiotherapy. CD8+ T cells were essential for curative responses to this combinatorial regime. Interestingly, CD137 expression on tumor-associated CD8+ T cells was largely restricted to a subset that highly expressed PD-1. These CD137+PD-1High CD8+ T cells, persisted in irradiated AT-3 tumors, expressed Tim-3, granzyme B and Ki67 and produced IFN-γ ex vivo in response to phorbol 12-myristate 13-acetate (PMA) and ionomycin stimulation. Notably, radiotherapy did not deplete, but enriched tumors of functionally active, tumor-specific effector cells. Collectively, these data show that concomitant targeting of immunostimulatory and inhibitory checkpoints with immunomodulatory mAbs can enhance the curative capacity of radiotherapy in established breast malignancy., (©2012 AACR.)

In this issue of Cancer Discovery, Bellail and colleagues unravel how overexpression of the ubiquitin-modifying enzyme A20 results in TNF-related apoptosis-inducing ligand (TRAIL) resistance in glioblastoma. After TRAIL receptor stimulation, A20 mediates the polyubiquitination of RIP1 at the TRAIL receptor tail, resulting in the interaction of the polyubiquin chain to procaspase-8 that is recruited to the TRAIL-bound receptors. The inability of ubiquitin-bound procaspase-8 to be dimerized and activated prevents the execution of the apoptotic program., (©2012 AACR.)

The occurrence of epigenetic aberrations in cancer and their role in promoting tumorigenesis has led to the development of various small molecule inhibitors that target epigenetic enzymes. In preclinical settings, many epigenetic inhibitors demonstrate promising activity against a variety of both hematological and solid tumors. The therapeutic efficacy of those inhibitors that have entered the clinic however, is restricted predominantly to hematological malignancies. Here we outline the observed epigenetic aberrations in various types of cancer and the clinical responses to epigenetic drugs. We furthermore discuss strategies to improve the responsiveness of both hematological and solid malignancies to epigenetic drugs.

Purpose: Various proapoptotic agents are currently being explored to improve the outcome of radiotherapy. We have evaluated whether APO010-a novel recombinant ligand of the Fas/CD95 death receptor-enhanced the cytotoxic effect of radiation on lymphoid and solid tumor cell types., Experimental Design: A Bcl-2-overexpressing T-leukemic cell line (Jurkat), a colon carcinoma cell line (HCT116), and a mesothelioma cell line were used as model systems in vitro and in a subcutaneous transplant setting in immunodeficient mice. Sensitivity to single and combined treatment was read out by apoptosis hallmarks and clonogenic survival in vitro, and by tumor growth delay using bioluminescence and palpation in vivo., Results: Whereas the three cell lines resisted apoptosis induction by irradiation and APO010 alone, combined treatment greatly enhanced their apoptotic response. In clonogenic survival assays, APO010 reduced the outgrowth of Jurkat-Bcl-2 and HCT116 cells and sensitized the mesothelioma cell line to radiation. In vivo, systemic treatment with APO010 alone caused tumor growth delay in Jurkat-Bcl-2 and HCT116 cells. However, APO010 did not improve the efficacy of radiotherapy in any of the model systems at the selected single dose, which had moderate and reversible systemic toxicity., Conclusions: Although APO010 and radiation had a clear combined cytotoxic effect on tumor cells in vitro, a combined therapeutic effect was not achieved on the same cells subcutaneously grafted in mice, at APO010 doses approximating the maximally tolerable level. These findings suggest that it will be difficult to identify a therapeutic window for this combined modality approach in a clinical setting.

Background and Purpose: Resistance to apoptosis is a contributing factor in the response to radiotherapy. Aim of this study was to evaluate whether TRAIL--in a soluble isoleucine zippered form--enhances the cytotoxic effect of irradiation on tumour cells with a blockade in the mitochondrial apoptosis route and/or a dysfunctional p53 pathway., Materials and Methods: The p53 mutant human T acute lymphoblastic leukemia line Jurkat transduced with the Bcl-2 gene was used as model system in vitro and in a subcutaneous transplant setting in immunodeficient mice. Sensitivity to single and combined treatment was read out by apoptosis hallmarks and clonogenic survival in vitro, and by bioluminescence and palpation in vivo., Results: Jurkat cells overexpressing Bcl-2 did not undergo apoptosis after irradiation, but the combination with TRAIL synergistically induced apoptosis without breaking mitochondrial resistance. TRAIL also reduced clonogenic survival after irradiation. In vivo, radiotherapy or TRAIL alone delayed tumour outgrowth, but combination treatment had the most profound effect., Conclusions: Isoleucine zippered TRAIL can strongly enhance the efficacy of tumour therapy with ionising radiation in an unfavourable setting of p53 mutation and Bcl-2 overexpression.