Glioblastoma multiforme (GBM) contains a subpopulation of cells, GBM stem cells (GSCs), that maintain the bulk tumor and represent a key therapeutic target. Norrin is a Wnt ligand that binds Frizzled class receptor 4 (FZD4) to activate canonical Wnt signaling. Although Norrin, encoded by NDP, has a well-described role in vascular development, its function in human tumorigenesis is largely unexplored. Here, we show that NDP expression is enriched in neurological cancers, including GBM, and its levels positively correlated with survival in a GBM subtype defined by low expression of ASCL1, a proneural factor. We investigated the function of Norrin and FZD4 in GSCs and found that it mediated opposing tumor-suppressive and -promoting effects on ASCL1lo and ASCL1hi GSCs. Consistent with a potential tumor-suppressive effect of Norrin suggested by the tumor outcome data, we found that Norrin signaling through FZD4 inhibited growth in ASCL1lo GSCs. In contrast, in ASCL1hi GSCs Norrin promoted Notch signaling, independently of WNT, to promote tumor progression. Forced ASCL1 expression reversed the tumor-suppressive effects of Norrin in ASCL1lo GSCs. Our results identify Norrin as a modulator of human brain cancer progression and reveal an unanticipated Notch-mediated function of Norrin in regulating cancer stem cell biology. This study identifies an unanticipated role of Norrin in human brain cancer progression. In addition, we provide preclinical evidence suggesting Norrin and canonical Wnt signaling as potential therapeutic targets for GBM subtype–restricted cancer stem cells.
Ahmed El-Sehemy, Hayden Selvadurai, Arturo Ortin-Martinez, Neno Pokrajac, Yasin Mamatjan, Nobuhiko Tachibana, Katherine Rowland, Lilian Lee, Nicole Park, Kenneth Aldape, Peter Dirks, Valerie A. Wallace
Stroke is the second leading cause of death worldwide and a leading cause of disability. Most strokes are caused by occlusion of a major cerebral artery, and substantial advances have been made in elucidating how ischemia damages the brain. In particular, increasing evidence points to a double-edged role of the immune system in stroke pathophysiology. In the acute phase, innate immune cells invade brain and meninges and contribute to ischemic damage, but may also be protective. At the same time, danger signals released into the circulation by damaged brain cells lead to activation of systemic immunity, followed by profound immunodepression that promotes life-threatening infections. In the chronic phase, antigen presentation initiates an adaptive immune response targeted to the brain, which may underlie neuropsychiatric sequelae, a considerable cause of poststroke morbidity. Here, we briefly review these pathogenic processes and assess the potential therapeutic value of targeting immunity in human stroke.
Costantino Iadecola, Marion S. Buckwalter, Josef Anrather
Laura E. Crotty Alexander, Amy L. Bellinghausen, Michelle N. Eakin
Hepatic de novo lipogenesis is a major contributor to nonalcoholic fatty liver disease (NAFLD). In this issue of the JCI, Liu and Lin et al. identified Slug as an epigenetic regulator of lipogenesis. Their findings suggest that Slug is stabilized by insulin signaling, and that it promotes lipogenesis by recruiting the histone demethylase Lsd1 to the fatty acid synthase gene promoter. On the other hand, genetic deletion or acute depletion of Slug, or Lsd1 inhibition, reduced lipogenesis and protected against obesity-associated NAFLD and insulin resistance in mice. This study advances our understanding of how lipogenesis is regulated downstream of insulin signaling in health and disease.
Clarence R. Manuel, Rebecca A. Haeusler
De novo lipogenesis is tightly regulated by insulin and nutritional signals to maintain metabolic homeostasis. Excessive lipogenesis induces lipotoxicity, leading to nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes. Genetic lipogenic programs have been extensively investigated, but epigenetic regulation of lipogenesis is poorly understood. Here, we identified Slug as an important epigenetic regulator of lipogenesis. Hepatic Slug levels were markedly upregulated in mice by either feeding or insulin treatment. In primary hepatocytes, insulin stimulation increased Slug expression, stability, and interactions with epigenetic enzyme lysine-specific demethylase-1 (Lsd1). Slug bound to the fatty acid synthase (Fasn) promoter where Slug-associated Lsd1 catalyzed H3K9 demethylation, thereby stimulating Fasn expression and lipogenesis. Ablation of Slug blunted insulin-stimulated lipogenesis. Conversely, overexpression of Slug, but not a Lsd1 binding-defective Slug mutant, stimulated Fasn expression and lipogenesis. Lsd1 inhibitor treatment also blocked Slug-stimulated lipogenesis. Remarkably, hepatocyte-specific deletion of Slug inhibited the hepatic lipogenic program and protected against obesity-associated NAFLD, insulin resistance, and glucose intolerance in mice. Conversely, liver-restricted overexpression of Slug, but not the Lsd1 binding-defective Slug mutant, had the opposite effects. These results unveil an insulin/Slug/Lsd1/H3K9 demethylation lipogenic pathway that promotes NAFLD and type 2 diabetes.
Yan Liu, Haiyan Lin, Lin Jiang, Qingsen Shang, Lei Yin, Jiandie D. Lin, Wen-Shu Wu, Liangyou Rui
Platinum-based chemotherapy–induced peripheral neuropathy is one of the most common causes of dose reduction and discontinuation of life-saving chemotherapy in cancer treatment; it often causes permanent impairment of quality of life in cancer patients. The mechanisms that underlie this neuropathy are not defined, and effective treatment and prevention measures are not available. Here, we demonstrate that SIRT2 protected mice against cisplatin-induced peripheral neuropathy (CIPN). SIRT2 accumulated in the nuclei of dorsal root ganglion sensory neurons and prevented neuronal cell death following cisplatin treatment. Mechanistically, SIRT2, an NAD+-dependent deacetylase, protected neurons from cisplatin cytotoxicity by promoting transcription-coupled nucleotide excision repair (TC-NER) of cisplatin-induced DNA cross-links. Consistent with this mechanism, pharmacological inhibition of NER using spironolactone abolished SIRT2-mediated TC-NER activity in differentiated neuronal cells and protection of neurons from cisplatin-induced cytotoxicity and CIPN in mice. Importantly, SIRT2’s protective effects were not evident in lung cancer cells in vitro or in tumors in vivo. Taken together, our results identified SIRT2’s function in the NER pathway as a key underlying mechanism of preventing CIPN, warranting future investigation of SIRT2 activation–mediated neuroprotection during platinum-based cancer treatment.
Manchao Zhang, Wuying Du, Scarlett Acklin, Shengkai Jin, Fen Xia
Herpesviruses infect virtually all humans and establish lifelong latency and reactivate to infect other humans. Latency requires multiple functions: maintaining the herpesvirus genome in the nuclei of cells; partitioning the viral genome to daughter cells in dividing cells; avoiding recognition by the immune system by limiting protein expression; producing noncoding viral RNAs (including microRNAs) to suppress lytic gene expression or regulate cellular protein expression that could otherwise eliminate virus-infected cells; modulating the epigenetic state of the viral genome to regulate viral gene expression; and reactivating to infect other hosts. Licensed antivirals inhibit virus replication, but do not affect latency. Understanding of the mechanisms of latency is leading to novel approaches to destroy latently infected cells or inhibit reactivation from latency.
Jeffrey I. Cohen
Patients with respiratory syncytial virus (RSV) infection exhibit enhanced susceptibility to subsequent pneumococcal infections. However, the underlying mechanisms involved in this increased susceptibility remain unclear. Here, we identified potentially novel cellular and molecular cascades triggered by RSV infection to exacerbate secondary pneumococcal pneumonia. RSV infection stimulated the local production of growth arrest–specific 6 (Gas6). The Gas6 receptor Axl was crucial for attenuating pneumococcal immunity in that the Gas6/Axl blockade fully restored antibacterial immunity. Mechanistically, Gas6/Axl interaction regulated the conversion of alveolar macrophages from an antibacterial phenotype to an M2-like phenotype that did not exhibit antibacterial activity, and the attenuation of caspase-1 activation and IL-18 production in response to pneumococcal infection. The attenuated IL-18 production failed to drive both NK cell–mediated IFN-γ production and local NO and TNF-α production, which impair the control of bacterial infection. Hence, the RSV-mediated Gas6/Axl activity attenuates the macrophage-mediated protection against pneumococcal infection. The Gas6/Axl axis could be a potentially novel therapeutic target for RSV-associated secondary bacterial infection.
Takehiko Shibata, Airi Makino, Ruiko Ogata, Shigeki Nakamura, Toshihiro Ito, Kisaburo Nagata, Yoshihiko Terauchi, Taku Oishi, Mikiya Fujieda, Yoshimasa Takahashi, Manabu Ato
Acute myeloid leukemia (AML) disrupts the generation of normal blood cells, predisposing patients to hemorrhage, anemia, and infections. Differentiation and proliferation of residual normal hematopoietic stem and progenitor cells (HSPCs) are impeded in AML-infiltrated bone marrow (BM). The underlying mechanisms and interactions of residual hematopoietic stem cells (HSCs) within the leukemic niche are poorly understood, especially in the human context. To mimic AML infiltration and dissect the cellular crosstalk in human BM, we established humanized ex vivo and in vivo niche models comprising AML cells, normal HSPCs, and mesenchymal stromal cells (MSCs). Both models replicated the suppression of phenotypically defined HSPC differentiation without affecting their viability. As occurs in AML patients, the majority of HSPCs were quiescent and showed enrichment of functional HSCs. HSPC suppression was largely dependent on secreted factors produced by transcriptionally remodeled MSCs. Secretome analysis and functional validation revealed MSC-derived stanniocalcin 1 (STC1) and its transcriptional regulator HIF-1α as limiting factors for HSPC proliferation. Abrogation of either STC1 or HIF-1α alleviated HSPC suppression by AML. This study provides a humanized model to study the crosstalk among HSPCs, leukemia, and their MSC niche, and a molecular mechanism whereby AML impairs normal hematopoiesis by remodeling the mesenchymal niche.
Alexander Waclawiczek, Ashley Hamilton, Kevin Rouault-Pierre, Ander Abarrategi, Manuel Garcia Albornoz, Farideh Miraki-Moud, Nourdine Bah, John Gribben, Jude Fitzgibbon, David Taussig, Dominique Bonnet
Salt-inducible kinases (SIKs) are key regulators of cellular metabolism and growth, but their role in cardiomyocyte plasticity and heart failure pathogenesis remains unknown. Here, we showed that loss of SIK1 kinase activity protected against adverse cardiac remodeling and heart failure pathogenesis in rodent models and cardiomyocytes derived from human induced pluripotent stem cells. We found that SIK1 phosphorylated and stabilized histone deacetylase 7 (HDAC7) protein during cardiac stress, an event that is required for pathologic cardiomyocyte remodeling. Gain- and loss-of-function studies of HDAC7 in cultured cardiomyocytes implicated HDAC7 as a prohypertrophic signaling effector that can induce c-Myc expression, indicating a functional departure from the canonical MEF2 corepressor function of class IIa HDACs. Taken together, our findings reveal what we believe to be a previously unrecognized role for a SIK1/HDAC7 axis in regulating cardiac stress responses and implicate this pathway as a potential target in human heart failure.
Austin Hsu, Qiming Duan, Sarah McMahon, Yu Huang, Sarah A.B. Wood, Nathanael S. Gray, Biao Wang, Benoit G. Bruneau, Saptarsi M. Haldar
Transcriptional reactivation of telomerase catalytic subunit (TERT) is a frequent hallmark of cancer, occurring in 90% of human malignancies. However, specific mechanisms driving TERT reactivation remain obscure for many tumor types and in particular gastric cancer (GC), a leading cause of global cancer mortality. Here, through comprehensive genomic and epigenomic analysis of primary GCs and GC cell lines, we identified the transcription factor early B cell factor 1 (EBF1) as a TERT transcriptional repressor and inactivation of EBF1 function as a major cause of TERT upregulation. Abolishment of EBF1 function occurs through 3 distinct (epi)genomic mechanisms. First, EBF1 is epigenetically silenced via DNA methyltransferase, polycomb-repressive complex 2 (PRC2), and histone deacetylase activity in GCs. Second, recurrent, somatic, and heterozygous EBF1 DNA–binding domain mutations result in the production of dominant-negative EBF1 isoforms. Third, more rarely, genomic deletions and rearrangements proximal to the TERT promoter remobilize or abolish EBF1-binding sites, derepressing TERT and leading to high TERT expression. EBF1 is also functionally required for various malignant phenotypes in vitro and in vivo, highlighting its importance for GC development. These results indicate that multimodal genomic and epigenomic alterations underpin TERT reactivation in GC, converging on transcriptional repressors such as EBF1.
Manjie Xing, Wen Fong Ooi, Jing Tan, Aditi Qamra, Po-Hsien Lee, Zhimei Li, Chang Xu, Nisha Padmanabhan, Jing Quan Lim, Yu Amanda Guo, Xiaosai Yao, Mandoli Amit, Ley Moy Ng, Taotao Sheng, Jing Wang, Kie Kyon Huang, Chukwuemeka George Anene-Nzelu, Shamaine Wei Ting Ho, Mohana Ray, Lijia Ma, Gregorio Fazzi, Kevin Junliang Lim, Giovani Claresta Wijaya, Shenli Zhang, Tannistha Nandi, Tingdong Yan, Mei Mei Chang, Kakoli Das, Zul Fazreen Adam Isa, Jeanie Wu, Polly Suk Yean Poon, Yue Ning Lam, Joyce Suling Lin, Su Ting Tay, Ming Hui Lee, Angie Lay Keng Tan, Xuewen Ong, Kevin White, Steven George Rozen, Michael Beer, Roger Sik Yin Foo, Heike Irmgard Grabsch, Anders Jacobsen Skanderup, Shang Li, Bin Tean Teh, Patrick Tan
Chimeric antigen receptor–T (CAR-T) cell therapies can eliminate relapsed and refractory tumors, but the durability of antitumor activity requires in vivo persistence. Differential signaling through the CAR costimulatory domain can alter the T cell metabolism, memory differentiation, and influence long-term persistence. CAR-T cells costimulated with 4-1BB or ICOS persist in xenograft models but those constructed with CD28 exhibit rapid clearance. Here, we show that a single amino acid residue in CD28 drove T cell exhaustion and hindered the persistence of CD28-based CAR-T cells and changing this asparagine to phenylalanine (CD28-YMFM) promoted durable antitumor control. In addition, CD28-YMFM CAR-T cells exhibited reduced T cell differentiation and exhaustion as well as increased skewing toward Th17 cells. Reciprocal modification of ICOS-containing CAR-T cells abolished in vivo persistence and antitumor activity. This finding suggests modifications to the costimulatory domains of CAR-T cells can enable longer persistence and thereby improve antitumor response.
Sonia Guedan, Aviv Madar, Victoria Casado-Medrano, Carolyn Shaw, Anna Wing, Fang Liu, Regina M. Young, Carl H. June, Avery D. Posey Jr.
Sustained persistence of chimeric antigen receptor T (CAR-T) cells is a key characteristic associated with long-term remission in patients with hematologic malignancies. Attempts to uncover mechanisms that enhance persistence and thus functionality will have a substantial impact in broadening application of CAR-T cell therapy, especially for solid tumors. In this issue of the JCI, Guedan et al. describe a promising strategy to limit T cell exhaustion and improve persistence by changing a single amino acid in the costimulatory domain of CD28. The authors demonstrated that this single amino acid substitution in CD28-based mesothelin CAR-T cells results in improved persistence and functionality in a xenograft model of pancreatic cancer. Furthermore, reciprocal alteration of the same residue in inducible costimulator–containing (ICOS-containing) CAR-T cells resulted in limited antitumor activity and persistence. These findings suggest that simple alterations in the costimulatory domain may enhance CAR-T cell persistence, warranting future evaluation in other CD28-costimulatory CARs in an effort to improve durable antitumor effects.
Emily M. Hsieh, Lauren D. Scherer, Rayne H. Rouce
Although autophagy is generally protective, uncontrolled or excessive activation of autophagy can be detrimental. However, it is often difficult to distinguish death by autophagy from death with autophagy, and whether autophagy contributes to death in cardiomyocytes (CMs) is still controversial. Excessive activation of autophagy induces a morphologically and biochemically defined form of cell death termed autosis. Whether autosis is involved in tissue injury induced under pathologically relevant conditions is poorly understood. In the present study, myocardial ischemia/reperfusion (I/R) induced autosis in CMs, as evidenced by cell death with numerous vacuoles and perinuclear spaces, and depleted intracellular membranes. Autosis was observed frequently after 6 hours of reperfusion, accompanied by upregulation of Rubicon, attenuation of autophagic flux, and marked accumulation of autophagosomes. Genetic downregulation of Rubicon inhibited autosis and reduced I/R injury, whereas stimulation of autosis during the late phase of I/R with Tat–Beclin 1 exacerbated injury. Suppression of autosis by ouabain, a cardiac glycoside, in humanized Na+,K+-ATPase–knockin mice reduced I/R injury. Taken together, these results demonstrate that autosis is significantly involved in I/R injury in the heart and triggered by dysregulated accumulation of autophagosomes due to upregulation of Rubicon.
Jihoon Nah, Peiyong Zhai, Chun-Yang Huang, Álvaro F. Fernández, Satvik Mareedu, Beth Levine, Junichi Sadoshima
Class IIa histone deacetylases (HDACs) repress cardiomyocyte hypertrophy through association with the prohypertrophic transcription factor (TF) myocyte enhancer factor-2 (MEF2). The four class IIa HDACs — HDAC4, -5, -7, and -9 — are subject to signal-dependent phosphorylation by members of the Ca2+/calmodulin-dependent protein kinase (CaMK) group. In response to stress, HDAC4, HDAC5, and HDAC9 undergo phosphorylation-induced nuclear export in cardiomyocytes, freeing MEF2 to stimulate progrowth genes; it was generally assumed that HDAC7 is also antihypertrophic. However, in this issue of the JCI, Hsu and colleagues demonstrate that, in sharp contrast to the other class IIa HDACs, HDAC7 is constitutively localized to the cardiomyocyte cytoplasm, where it promotes cardiac hypertrophy. Phosphorylation of HDAC7 by the CaMK group member salt-inducible kinase 1 (SIK1) stabilized the deacetylase, leading to increased expression of c-Myc, which in turn stimulated a pathological gene program. These unexpected findings highlight the SIK1/HDAC7 signaling axis as a promising target for the treatment of cardiac hypertrophy and heart failure.
Joshua G. Travers, Tianjing Hu, Timothy A. McKinsey
The precise mechanism leading to profound immunodeficiency of HIV-infected patients is still only partially understood. Here, we show that more than 80% of CD4+ T cells from HIV-infected patients have morphological abnormalities. Their membranes exhibited numerous large abnormal membrane microdomains (aMMDs), which trap and inactivate physiological receptors, such as that for IL-7. In patient plasma, we identified phospholipase A2 group IB (PLA2G1B) as the key molecule responsible for the formation of aMMDs. At physiological concentrations, PLA2G1B synergized with the HIV gp41 envelope protein, which appears to be a driver that targets PLA2G1B to the CD4+ T cell surface. The PLA2G1B/gp41 pair induced CD4+ T cell unresponsiveness (anergy). At high concentrations in vitro, PLA2G1B acted alone, independently of gp41, and inhibited the IL-2, IL-4, and IL-7 responses, as well as TCR-mediated activation and proliferation, of CD4+ T cells. PLA2G1B also decreased CD4+ T cell survival in vitro, likely playing a role in CD4 lymphopenia in conjunction with its induced IL-7 receptor defects. The effects on CD4+ T cell anergy could be blocked by a PLA2G1B-specific neutralizing mAb in vitro and in vivo. The PLA2G1B/gp41 pair constitutes what we believe is a new mechanism of immune dysfunction and a compelling target for boosting immune responses in HIV-infected patients.
Julien Pothlichet, Thierry Rose, Florence Bugault, Louise Jeammet, Annalisa Meola, Ahmed Haouz, Frederick Saul, David Geny, José Alcami, Ezequiel Ruiz-Mateos, Luc Teyton, Gérard Lambeau, Jacques Thèze
Nadine Haase, Donald J. Foster, Mark W. Cunningham, Julia Bercher, Tuyen Nguyen, Svetlana Shulga-Morskaya, Stuart Milstein, Sarfraz Shaikh, Jeff Rollins, Michaela Golic, Florian Herse, Kristin Kräker, Ivo Bendix, Meray Serdar, Hanna Napieczynska, Arnd Heuser, Alexandra Gellhaus, Kristin Thiele, Gerd Wallukat, Dominik N. Müller, Babbette LaMarca, Ralf Dechend
M. Bishr Omary, Jeetendra Eswaraka, S. David Kimball, Prabhas V. Moghe, Reynold A. Panettieri Jr., Kathleen W. Scotto
Plasmacytoid dendritic cells (pDCs) are robust producers of IFNα and one of the first immune cells to respond to SIV infection. To elucidate responses to early HIV-1 replication, we studied blood pDCs in 29 HIV-infected participants who initiated antiretroviral therapy during acute infection and underwent analytic treatment interruption (ATI). We observed an increased frequency of partially activated pDCs in the blood before detection of HIV RNA. Concurrent with peak pDC frequency, we detected a transient decline in the ability of pDCs to produce IFNα in vitro, which correlated with decreased phosphorylation of IFN regulatory factory 7 (IRF7) and NF-κB. The levels of phosphorylated IRF7 and NF-κB inversely correlated with plasma IFNα2 levels, implying that pDCs were refractory to in vitro stimulation after IFNα production in vivo. After ATI, decreased expression of IFN genes in pDCs inversely correlated with the time to viral detection, suggesting that pDC IFN loss is part of an effective early immune response. These data from a limited cohort provide a critical first step in understanding the earliest immune response to HIV-1 and suggest that changes in blood pDC frequency and function can be used as an indicator of viral replication before detectable plasma viremia.
Julie L. Mitchell, Hiroshi Takata, Roshell Muir, Donn J. Colby, Eugène Kroon, Trevor A. Crowell, Carlo Sacdalan, Suteeraporn Pinyakorn, Suwanna Puttamaswin, Khunthalee Benjapornpong, Rapee Trichavaroj, Randall L. Tressler, Lawrence Fox, Victoria R. Polonis, Diane L. Bolton, Frank Maldarelli, Sharon R. Lewin, Elias K. Haddad, Praphan Phanuphak, Merlin L. Robb, Nelson L. Michael, Mark de Souza, Nittaya Phanuphak, Jintanat Ananworanich, Lydie Trautmann, on behalf of the RV397, RV411, and RV254 Study Groups
Plasmodium vivax bench research greatly lags behind Plasmodium falciparum because of an inability to culture in vitro. A century ago, intentionally inducing a malaria infection was a strategy commonly used to cure late-stage syphilis. These controlled human malaria infections were used with expertise and persisted to the end of World War II. While controlled malaria liver-stage infection has been achieved for both P. vivax and P. falciparum, controlled human transmission to mosquitoes falls short for both species. In this issue of the JCI, Collins et al. present groundbreaking work that establishes a system to transmit P. vivax gametocytes from humans to mosquitoes. The authors injected a unique human isolate of P. vivax that reached high gametocyte density within weeks. This study provides a technical advance that will facilitate the study and eradication of the human parasite P. vivax.
David J. Sullivan, Peter Agre