Mitochondrial dysfunction or loss is evident in neurodegenerative diseases. Furthermore, mitochondrial DNA (mtDNA) mutations associated with NADH dehydrogenase subunits and nuclear gene mutations that affect mitochondrial function result in optic neuropathies. In this issue of the JCI, Del Dotto et al. and Piro-Mégy et al. identify heterozygous mutations in nuclear-encoded mitochondrial single-strand binding protein 1 (SSBP1) in patients with apparently dominant optic neuropathy with or without extraocular phenotypes. Both research groups reported similar mitochondrial findings in response to SSBP1 mutations. However, the specific SSBP1 mitochondria–associated function in retinal ganglion cells (RGCs) and the resulting optic nerve remains unclear. We suggest that high expression of SSBP1 during RGC differentiation is critical for mtDNA maintenance to produce appropriate optic nerve connectivity and that SSBP1 mutations in dominant optic atrophy patients do not permit stable binding to N6-methyldeoxyadenosine on the heavy strand involved with replication, leading to disruptions of mtDNA and, eventually, optic nerve dysfunction.
Lina Zelinger, Anand Swaroop
Tumor-induced immunosuppression is a common obstacle for cancer treatment. Adrenergic signaling triggered by chronic stress participates in the creation of an immunosuppressive microenvironment by promoting myeloid-derived suppressor cell (MDSC) proliferation and activation. In this issue of the JCI, Mohammadpour et al. elegantly delve into the mechanisms underlying MDSC contribution to tumor development. They used in vitro and in vivo mouse models to demonstrate that chronic stress results in MDSC accumulation, survival, and immune-inhibitory activity. Of therapeutic relevance, the authors showed that propranolol, a commonly prescribed β-blocker, can reduce MDSC immunosuppression and enhance the effect of other cancer therapies.
Ignacio Iñigo-Marco, Marta M. Alonso
Cancer immunotherapy and its budding effectiveness at improving patient outcomes has revitalized our hope to fight cancer in a logical and safe manner. Immunotherapeutic approaches to reengage the immune system have largely focused on reversing immune checkpoint inhibitor pathways, which suppress the antitumor response. Although these approaches have generated much excitement, they still lack absolute success. Interestingly, newly described host-tumor sugar chains (glycosylations) and glycosylation-binding proteins (lectins) play key roles in evading the immune system to determine cancer progression. In this issue of the JCI, Nambiar et al. used patient head and neck tumors and a mouse model system to investigate the role of galactose-binding lectin 1 (Gal1) in immunotherapy resistance. The authors demonstrated that Gal1 can affect immune checkpoint inhibitor therapy by increasing immune checkpoint molecules and immunosuppressive signaling in the tumor. Notably, these results suggest that targeting a tumor’s glycobiological state will improve treatment efficacy.
Asmi Chakraborty, Charles J. Dimitroff
Manganese (Mn) participates in a variety of distinct physiological processes, including acting as a cofactor for several enzymes and metalloenzymes, in addition to playing a role in immune function, endocrine function, hematopoiesis, and oxidative stress regulation. Mn homeostasis is tightly regulated via intestinal absorption and hepatobiliary and intestinal excretion. In this issue of the JCI, Mercadante and colleagues explored the role of the metal transporter Slc30a10 in vivo using a mouse model system. The authors used whole-body and tissue-specific gene knockouts to show that Slc30a10 is paramount for Mn excretion in the liver and small intestines. These findings provide further insights into mechanisms for Mn homeostasis as well as potential targets for addressing Mn-associated disorders or environmental exposures.
Nathan Katz, Daniel J. Rader
Neutrophils are early wound healing and inflammation regulators that, due to functional plasticity, can adopt either pro- or antitumor functions. Until recently, beclin-1 was a protein known mainly for its role as a critical regulator of autophagy. In this issue of the JCI, Tan et al. describe the effects of the beclin-1 conditional myeloid cell–specific deletion in mice, in which immunostimulation resulted in hypersensitive neutrophils. The chronic proinflammatory effect of these neutrophils triggered spontaneous B cell malignancies to develop. Such tumorigenic effects were mediated primarily by IL-21 and CD40 signaling, leading to the upregulation of tolerogenic molecules, such as IL-10 and PD-L1. The authors went on to examine samples derived from patient lymphoid malignancies and showed that beclin-1 expression in neutrophils positively correlated with pre–B cell leukemia/lymphoma. Overall, the study provides an elegant model for neutrophil-driven carcinogenesis and identifies potential targets for immunotherapy of B cell malignancies.
Yu-Lin Su, Marcin Kortylewski
With the approval of CD19-targeted chimeric antigen receptor (CAR) T cells for the treatment of B cell malignancies, clinicians have gained valuable insights into the power and challenges of cellular therapies. In this issue of the JCI, Maluski et al. showed that a CAR containing a CD28 costimulatory domain drives progeny differentiation to resemble that of NK cells, which have the potential for an off-the-shelf cell therapy. These CAR-induced killer (CARiK) cells displayed potent antitumor function and killed across the MHC barrier in vivo. After performing in vitro and in vivo mouse studies, the authors also successfully differentiated human umbilical cord blood–derived progenitor cells into CARiK cells. These unique cells may address some of the current challenges associated with first-generation CARs, such as prolonged production that requires patients to wait weeks for infusion. We believe this innovative progenitor gene-engineered lymphoid system has the potential for clinical translation.
Brigett D. Brandjes, Marco L. Davila
Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired disorder characterized by hemolysis, thrombosis, and bone marrow failure caused by defective expression of glycosylphosphatidylinositol-anchored (GPI-anchored) complement inhibitors. Most commonly, PNH is caused by loss of function of PIGA, which is required for GPI biosynthesis. In this issue of the JCI, Höchsmann et al. report on 4 PNH patients who also had marked autoinflammatory manifestations, including aseptic meningitis. All 4 patients had a germline mutation of the related gene PIGT and a somatically acquired myeloid common deleted region (CDR) on chromosome 20q that deleted the second PIGT allele. The biochemistry and clinical manifestations indicate that these patients have subtle but important differences from those with PNH resulting from PIGA mutations, suggesting PIGT-PNH may be a distinct clinical entity.
Robert A. Brodsky
The interleukin 3 receptor (CD123) is a transmembrane protein that is absent or hardly expressed on normal hematopoietic stem cells, but highly expressed on the surface of cancer cells in several hematologic malignancies. In this issue of the JCI, Togami et al. investigated the mechanism of resistance to the recently approved anti-CD123 agent tagraxofusp, which consists of interleukin 3 fused to a truncated diphtheria toxin (DT) molecule. The authors demonstrated that loss of the intracellular target for DT, diphthamide, a conservative modification of histidine 715 in eukaryotic elongation factor 2, resulted in tagraxofusp resistance. Specifically, hypermethylation of the DPH1 gene, encoding a key enzyme in diphthamide synthesis, resulted in diphthamide loss. Notably, treatment with a DNA hypomethylating agent restored DPH1 expression and resensitized cells to tagraxofusp. The recognition of this resistance mechanism may have important clinical implications and lead to the development of more effective multiagent therapies.
Lukasz P. Gondek
A strong Th17 inflammatory response aggravates ischemia reperfusion–induced (IR-induced) acute kidney injury (AKI), tissue fibrosis, and AKI-to–chronic kidney disease (CKD) progression. However, the underlying mechanisms of sustained Th17 activation following AKI and during AKI-to-CKD progression are unclear. In this issue of the JCI, Mehrotra et al. present compelling evidence that the store-operated calcium (Ca2+) channel Orai1 sustains Th17-driven inflammatory response after AKI and drives the AKI-to-CKD transition. Orai1 blockade significantly protected renal function from IR, attenuated high-salt–induced AKI-to-CKD progression in rats, and decreased Th17 response in rat and human T cells. Therapeutic targeting of Orai1 can potentially reduce AKI, AKI-to-CKD progression, and other Th17-driven diseases.
Cardiac tissue necrosis secondary to coronary artery occlusion is one of the most common and deadly sterile injuries in developed countries. In this issue of the JCI, Rieckmann et al. identified and characterized antigen-specific CD4+ T helper (Th) cells that developed in the context of myocardial infarction (MI) in mice. They showed that myosin heavy chain α (MYHCA) is a dominant cardiac autoantigen and that T cells with T cell receptor (TCR) specificity to MYHCA acquired a Treg phenotype when adoptively transferred into infarcted mice, which mediated a cardioprotective healing response. Thus, Rieckmann et al. showed that an acute ischemic insult to the heart, which induces sterile inflammation, promoted, rather than limited, protective T cell autoimmunity. Notably, strategies that support an antigen-specific Treg response may limit the immune-inflammatory response and promote cardiac repair after acute MI.
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