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Abstract

Heterozygous germline mutations in breast cancer 1 (BRCA1) strongly predispose women to breast cancer. BRCA1 plays an important role in DNA double-strand break (DSB) repair via homologous recombination (HR), which is important for tumor suppression. Although BRCA1-deficient cells are highly sensitive to treatment with DSB-inducing agents through their HR deficiency (HRD), BRCA1-associated tumors display heterogeneous responses to platinum drugs and poly(ADP-ribose) polymerase (PARP) inhibitors in clinical trials. It is unclear whether all pathogenic BRCA1 mutations have similar effects on the response to therapy. Here, we have investigated mammary tumorigenesis and therapy sensitivity in mice carrying the Brca1185stop and Brca15382stop alleles, which respectively mimic the 2 most common BRCA1 founder mutations, BRCA1185delAG and BRCA15382insC. Both the Brca1185stop and Brca15382stop mutations predisposed animals to mammary tumors, but Brca1185stop tumors responded markedly worse to HRD-targeted therapy than did Brca15382stop tumors. Mice expressing Brca1185stop mutations also developed therapy resistance more rapidly than did mice expressing Brca15382stop. We determined that both murine Brca1185stop tumors and human BRCA1185delAG breast cancer cells expressed a really interesting new gene domain–less (RING-less) BRCA1 protein that mediated resistance to HRD-targeted therapies. Together, these results suggest that expression of RING-less BRCA1 may serve as a marker to predict poor response to DSB-inducing therapy in human cancer patients.

Authors

Rinske Drost, Kiranjit K. Dhillon, Hanneke van der Gulden, Ingrid van der Heijden, Inger Brandsma, Cristina Cruz, Dafni Chondronasiou, Marta Castroviejo-Bermejo, Ute Boon, Eva Schut, Eline van der Burg, Ellen Wientjens, Mark Pieterse, Christiaan Klijn, Sjoerd Klarenbeek, Fabricio Loayza-Puch, Ran Elkon, Liesbeth van Deemter, Sven Rottenberg, Marieke van de Ven, Dick H.W. Dekkers, Jeroen A.A. Demmers, Dik C. van Gent, Reuven Agami, Judith Balmaña, Violeta Serra, Toshiyasu Taniguchi, Peter Bouwman, Jos Jonkers

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Abstract

A rare subset of HIV-1–infected individuals is able to maintain plasma viral load (VL) at low levels without antiretroviral treatment. Identifying the mechanisms underlying this atypical response to infection may lead to therapeutic advances for treating HIV-1. Here, we developed a proteomic analysis to compare peripheral blood cell proteomes in 20 HIV-1–infected individuals who maintained either high or low VL with the aim of identifying host factors that impact HIV-1 replication. We determined that the levels of multiple histone proteins were markedly decreased in cohorts of individuals with high VL. This reduction was correlated with lower levels of stem-loop binding protein (SLBP), which is known to control histone metabolism. Depletion of cellular SLBP increased promoter engagement with the chromatin structures of the host gene high mobility group protein A1 (HMGA1) and viral long terminal repeat (LTR), which led to higher levels of HIV-1 genomic integration and proviral transcription. Further, we determined that TNF-α regulates expression of SLBP and observed that plasma TNF-α levels in HIV-1–infected individuals correlated directly with VL levels and inversely with cellular SLBP levels. Our findings identify SLBP as a potentially important cellular regulator of HIV-1, thereby establishing a link between histone metabolism, inflammation, and HIV-1 infection.

Authors

Ming Li, Lynne D. Tucker, John M. Asara, Collins K. Cheruiyot, Huafei Lu, Zhijin J. Wu, Michael C. Newstein, Mark S. Dooner, Jennifer Friedman, Michelle A. Lally, Bharat Ramratnam

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Abstract

Following immune attack, solid tumors upregulate coinhibitory ligands that bind to inhibitory receptors on T cells. This adaptive resistance compromises the efficacy of chimeric antigen receptor (CAR) T cell therapies, which redirect T cells to solid tumors. Here, we investigated whether programmed death-1–mediated (PD-1–mediated) T cell exhaustion affects mesothelin-targeted CAR T cells and explored cell-intrinsic strategies to overcome inhibition of CAR T cells. Using an orthotopic mouse model of pleural mesothelioma, we determined that relatively high doses of both CD28- and 4-1BB–based second-generation CAR T cells achieved tumor eradication. CAR-mediated CD28 and 4-1BB costimulation resulted in similar levels of T cell persistence in animals treated with low T cell doses; however, PD-1 upregulation within the tumor microenvironment inhibited T cell function. At lower doses, 4-1BB CAR T cells retained their cytotoxic and cytokine secretion functions longer than CD28 CAR T cells. The prolonged function of 4-1BB CAR T cells correlated with improved survival. PD-1/PD-1 ligand [PD-L1] pathway interference, through PD-1 antibody checkpoint blockade, cell-intrinsic PD-1 shRNA blockade, or a PD-1 dominant negative receptor, restored the effector function of CD28 CAR T cells. These findings provide mechanistic insights into human CAR T cell exhaustion in solid tumors and suggest that PD-1/PD-L1 blockade may be an effective strategy for improving the potency of CAR T cell therapies.

Authors

Leonid Cherkassky, Aurore Morello, Jonathan Villena-Vargas, Yang Feng, Dimiter S. Dimitrov, David R. Jones, Michel Sadelain, Prasad S. Adusumilli

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Abstract

E2F-mediated transcriptional repression of cell cycle–dependent gene expression is critical for the control of cellular proliferation, survival, and development. E2F signaling also interacts with transcriptional programs that are downstream of genetic predictors for cancer development, including hepatocellular carcinoma (HCC). Here, we evaluated the function of the atypical repressor genes E2f7 and E2f8 in adult liver physiology. Using several loss-of-function alleles in mice, we determined that combined deletion of E2f7 and E2f8 in hepatocytes leads to HCC. Temporal-specific ablation strategies revealed that E2f8’s tumor suppressor role is critical during the first 2 weeks of life, which correspond to a highly proliferative stage of postnatal liver development. Disruption of E2F8’s DNA binding activity phenocopied the effects of an E2f8 null allele and led to HCC. Finally, a profile of chromatin occupancy and gene expression in young and tumor-bearing mice identified a set of shared targets for E2F7 and E2F8 whose increased expression during early postnatal liver development is associated with HCC progression in mice. Increased expression of E2F8-specific target genes was also observed in human liver biopsies from HCC patients compared to healthy patients. In summary, these studies suggest that E2F8-mediated transcriptional repression is a critical tumor suppressor mechanism during postnatal liver development.

Authors

Lindsey N. Kent, Jessica B. Rakijas, Shusil K. Pandit, Bart Westendorp, Hui-Zi Chen, Justin T. Huntington, Xing Tang, Sooin Bae, Arunima Srivastava, Shantibhusan Senapati, Christopher Koivisto, Chelsea K. Martin, Maria C. Cuitino, Miguel Perez, Julian M. Clouse, Veda Chokshi, Neelam Shinde, Raleigh Kladney, Daokun Sun, Antonio Perez-Castro, Ramadhan B. Matondo, Sathidpak Nantasanti, Michal Mokry, Kun Huang, Raghu Machiraju, Soledad Fernandez, Thomas J. Rosol, Vincenzo Coppola, Kamal S. Pohar, James M. Pipas, Carl R. Schmidt, Alain de Bruin, Gustavo Leone

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Abstract

Tumor suppression that is mediated by oncogene-induced senescence (OIS) is considered to function as a safeguard during development of pancreatic ductal adenocarcinoma (PDAC). However, the mechanisms that regulate OIS in PDAC are poorly understood. Here, we have determined that nuclear RelA reinforces OIS to inhibit carcinogenesis in the Kras mouse model of PDAC. Inactivation of RelA accelerated pancreatic lesion formation in Kras mice by abrogating the senescence-associated secretory phenotype (SASP) gene transcription signature. Using genetic and pharmacological tools, we determined that RelA activation promotes OIS via elevation of the SASP factor CXCL1 (also known as KC), which activates CXCR2, during pancreatic carcinogenesis. In Kras mice, pancreas-specific inactivation of CXCR2 prevented OIS and was correlated with increased tumor proliferation and decreased survival. Moreover, reductions in CXCR2 levels were associated with advanced neoplastic lesions in tissue from human pancreatic specimens. Genetically disabling OIS in Kras mice caused RelA to promote tumor proliferation, suggesting a dual role for RelA signaling in pancreatic carcinogenesis. Taken together, our data suggest a pivotal role for RelA in regulating OIS in preneoplastic lesions and implicate the RelA/CXCL1/CXCR2 axis as an essential mechanism of tumor surveillance in PDAC.

Authors

Marina Lesina, Sonja Maria Wörmann, Jennifer Morton, Kalliope Nina Diakopoulos, Olga Korneeva, Margit Wimmer, Henrik Einwächter, Jan Sperveslage, Ihsan Ekin Demir, Timo Kehl, Dieter Saur, Bence Sipos, Mathias Heikenwälder, Jörg Manfred Steiner, Timothy Cragin Wang, Owen J. Sansom, Roland Michael Schmid, Hana Algül

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Abstract

BACKGROUND. Administration of conventional antithrombotic treatment (low-dose aspirin plus low–molecular weight heparin [LDA+LMWH]) for obstetric antiphospholipid syndrome (APS) does not prevent life-threatening placenta insufficiency–associated complications such as preeclampsia (PE) and intrauterine growth restriction (IUGR) in 20% of patients. Statins have been linked to improved pregnancy outcomes in mouse models of PE and APS, possibly due to their protective effects on endothelium. Here, we investigated the use of pravastatin in LDA+LMWH-refractory APS in patients at an increased risk of adverse pregnancy outcomes.

METHODS. We studied 21 pregnant women with APS who developed PE and/or IUGR during treatment with LDA+LMWH. A control group of 10 patients received only LDA+LMWH. Eleven patients received pravastatin (20 mg/d) in addition to LDA+LMWH at the onset of PE and/or IUGR. Uteroplacental blood hemodynamics, progression of PE features (hypertension and proteinuria), and fetal/neonatal outcomes were evaluated.

RESULTS. In the control group, all deliveries occurred preterm and only 6 of 11 neonates survived. Of the 6 surviving neonates, 3 showed abnormal development. Patients who received both pravastatin and LDA+LMWH exhibited increased placental blood flow and improvements in PE features. These beneficial effects were observed as early as 10 days after pravastatin treatment onset. Pravastatin treatment combined with LDA+LMWH was also associated with live births that occurred close to full term in all patients.

CONCLUSION. The present study suggests that pravastatin may improve pregnancy outcomes in women with refractory obstetric APS when taken at the onset of PE or IUGR until the end of pregnancy.

Authors

Eleftheria Lefkou, Apostolos Mamopoulos, Themistoklis Dagklis, Christos Vosnakis, David Rousso, Guillermina Girardi

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Abstract

Patients with cancers that harbor breast cancer 1 (BRCA1) mutations initially respond well to platinum and poly(ADP-ribose) polymerase inhibitor (PARPi) therapy; however, resistance invariably arises in these patients and is a major clinical problem. The BRCA1185delAG allele is a common inherited mutation located close to the protein translation start site that is thought to produce a shortened, nonfunctional peptide. In this study, we investigated the mechanisms that lead to PARPi and platinum resistance in the SUM1315MO2 breast cancer cell line, which harbors a hemizygous BRCA1185delAG mutation. SUM1315MO2 cells were initially sensitive to PARPi and cisplatin but readily acquired resistance. PARPi- and cisplatin-resistant clones did not harbor secondary reversion mutations; rather, PARPi and platinum resistance required increased expression of a really interesting gene (RING) domain–deficient BRCA1 protein (Rdd-BRCA1). Initiation of translation occurred downstream of the frameshift mutation, probably at the BRCA1-Met-297 codon. In contrast to full-length BRCA1, Rdd-BRCA1 did not require BRCA1-associated RING domain 1 (BARD1) interaction for stability. Functionally, Rdd-BRCA1 formed irradiation-induced foci and supported RAD51 foci formation. Ectopic overexpression of Rdd-BRCA1 promoted partial PARPi and cisplatin resistance. Furthermore, Rdd-BRCA1 protein expression was detected in recurrent carcinomas from patients who carried germline BRCA1185delAG mutations. Taken together, these results indicate that RING-deficient BRCA1 proteins are hypomorphic and capable of contributing to PARPi and platinum resistance when expressed at high levels.

Authors

Yifan Wang, John J. Krais, Andrea J. Bernhardy, Emmanuelle Nicolas, Kathy Q. Cai, Maria I. Harrell, Hyoung H. Kim, Erin George, Elizabeth M. Swisher, Fiona Simpkins, Neil Johnson

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Abstract

Inflammation and oxidative stress are known risk factors for preterm birth (PTB); however, the mechanisms and pathways that influence this condition are not fully described. Previously, we showed that mTORC1 signaling is increased in mice harboring a uterine-specific deletion of transformation-related protein 53 (p53d/d mice), which exhibit premature decidual senescence that triggers spontaneous and inflammation-induced PTB. Treatment with the mTORC1 inhibitor rapamycin reduced the incidence of PTB in the p53d/d mice. Decidual senescence with heightened mTORC1 signaling is also a signature of human PTB. Here, we have identified an underlying mechanism for PTB and a potential therapeutic strategy for treating the condition. Treatment of pregnant p53d/d mice with either the antidiabetic drug metformin or the antioxidant resveratrol activated AMPK signaling and inhibited mTORC1 signaling in decidual cells. Both metformin and resveratrol protected against spontaneous and inflammation-induced PTB in p53d/d females. Using multiple approaches, we determined that p53 interacts with sestrins to coordinate an inverse relationship between AMPK and mTORC1 signaling that determines parturition timing. This signature was also observed in human decidual cells. Together, these results reveal that p53-dependent coordination of AMPK and mTORC1 signaling controls parturition timing and suggest that metformin and resveratrol have therapeutic potential to prevent PTB.

Authors

Wenbo Deng, Jeeyeon Cha, Jia Yuan, Hirofumi Haraguchi, Amanda Bartos, Emma Leishman, Benoit Viollet, Heather B. Bradshaw, Yasushi Hirota, Sudhansu K. Dey

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Abstract

The recent clinical success of chimeric antigen receptor (CAR) T cell therapy for B cell malignancies represents a paradigm shift in cancer immunotherapy. Unfortunately, application of CAR T cell–mediated therapy for solid tumors has so far been disappointing, and the reasons for this poor response in solid tumors remain unknown. In this issue of the JCI, Cherkassky and colleagues report on their use of a murine model of human pleural mesothelioma to explore potential factors that limit CAR T cell efficacy. Their studies have uncovered the importance of the tumor microenvironment in the inhibition of CAR T cell functions, revealed a critical role for the programmed death-1 (PD-1) pathway in CAR T cell exhaustion within the tumor microenvironment, and demonstrated improved antitumor effects with a CAR T cell–intrinsic PD-1 blockade strategy using a dominant negative form of PD-1. Together, the results of this study lay the groundwork for further evaluation of mechanisms underlying CAR T cell immune evasion within the tumor microenvironment for the improvement of CAR T cell–mediated therapy for solid tumors.

Authors

Xiaopei Huang, Yiping Yang

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Abstract

Pregnant women with antiphospholipid syndrome (APS) are at a high risk of obstetrical complications. The current standard of care, including the use of low-dose aspirin and heparin, has not been shown to prevent preeclampsia or intrauterine growth restriction (IUGR). Due to the similarities in pathophysiology among preeclampsia, IUGR, and atherosclerotic cardiovascular disease, statins have been proposed for treating and/or preventing these obstetrical complications. In this issue of the JCI, Lefkou et al. report on a small, observational trial that showed a dramatic improvement in both maternal and fetal/neonatal outcomes in women with APS given pravastatin after the onset of preeclampsia and/or IUGR compared with women in the control group. These results, along with other recent clinical studies, support further evaluation of statins for prevention of preeclampsia in a large-scale randomized clinical trial.

Authors

Maged M. Costantine

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Abstract

Pancreatic ductal adenocarcinoma (PDAC) is a deadly cancer in which NF-κB pathways promote biological aggressiveness. In this issue of the JCI, Lesina et al. investigated the role of RelA, the p65 partner of p50 that together form the most common NF-κB complex, in the early stages of pancreatic malignant transformation and in established PDAC. By deleting Rela in the context of an oncogenic Kras-driven autochthonous model of PDAC, the authors demonstrated that RelA is a mediator of oncogene-induced senescence (OIS) and the senescence-associated secretory phenotype (SASP) that attenuates acinar-to-ductal metaplasia, pancreatic intraepithelial neoplasia (PanIN) formation, and PanIN progression to PDAC. Loss of the tumor-suppressor function of RelA in the early stages of Kras-driven pancreatic neoplastic transformation was associated with decreased OIS and SASP and a protumorigenic tumor microenvironment that harbored more M2 macrophages and myeloid-derived suppressor cells. The beneficial effects of RelA were mediated by increased expression of CXCL1 and its activation of CXCR2. By contrast, in advanced stages of Kras-driven murine PDAC, loss of p53 or p16 was associated with senescence bypass, and RelA deficiency in this context attenuated cancer cell proliferation and prolonged mouse survival, indicating that RelA enhances tumor progression in established PDAC.

Authors

Murray Korc

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Abstract

Germline breast cancer 1 (BRCA1) variants are associated with a high risk of breast and ovarian cancers. Many BRCA1-mediated cancers are initially responsive to platinum-based therapy; however, resistance commonly develops. The BRCA1185delAG mutation is common in the Ashkenazi Jewish population and has been thought to result in loss of function due to the introduction of a stop codon in the 5′ region of the BRCA1 transcript. Two studies in this issue of the JCI reveal that the BRCA1185delAG mutation results in the production of BRCA1 that lacks the N-terminal really interesting new gene (RING) domain. RING-less BRCA1 was shown to directly mediate chemoresistance, while maintaining some homologous recombination function. These results provide important insight into BRCA1 function and indicate that other truncated proteins could arise through similar alterations in codon usage.

Authors

Simon N. Powell

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July 2016

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July 2016 Issue

On the cover:
Mitochondrial metabolism in asthma

The cover image is a false-colored electron micrograph showing the ultrastructure of mitochondria in bronchial epithelium from an asthmatic. On page 2465, Xu et al. describe a protective role for arginine metabolism in maintaining airway epithelial cell bioenergetics and inhibiting inflammation.

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Jci this month 2016 07

July 2016 JCI This Month

JCI This Month is a digest of the research, reviews, and other features published each month.

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Review Series - More

Extracellular Vesicles

Series edited by Laurence Zitvogel

Cell-to-cell communication is an essential component in multicellular organisms, allowing for rapid, coordinated responses to changes within the environment. Classical signaling mediators include direct cell-cell contact as well as secreted factors, such as cytokines, metabolites, and hormones. In the past decade, extracellular vesicles (EVs), including exosomes, microvesicles, and apoptotic bodies, have emerged as important mediators of intercellular communication. EVs are double-membrane vesicles containing cargoes of multiple proteins, lipids, and nucleic acids, which are derived from their cells of origin, and EV cargoes can change depending on the status of their originating cells. Importantly, EVs are found in all body fluids and can carry their cargoes to distant sites within the body as well as neighboring cells. Reviews in this series discuss the role of EV-mediated signaling in physiological and pathophysiological conditions, including infection, host immune responses, and cancer. Additionally, these reviews cover the potential clinical use of EVs as therapeutics and diagnostic biomarkers.

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