Summary
A single protein, HMGB1, directs the triggering of inflammation, innate and adaptive immune responses, and tissue healing after damage. HMGB1 is the best characterized damage‐associated ...molecular pattern (DAMP), proteins that are normally inside the cell but are released after cell death, and allow the immune system to distinguish between antigens that are dangerous or not. Notably, cells undergoing severe stress actively secrete HMGB1 via a dedicated secretion pathway: HMGB1 is relocated from the nucleus to the cytoplasm and then to secretory lysosomes or directly to the extracellular space. Extracellular HMGB1 (either released or secreted) triggers inflammation and adaptive immunological responses by switching among multiple oxidation states, which direct the mutually exclusive choices of different binding partners and receptors. Immune cells are first recruited to the damaged tissue and then activated; thereafter, HMGB1 supports tissue repair and healing, by coordinating the switch of macrophages to a tissue‐healing phenotype, activation and proliferation of stem cells, and neoangiogenesis. Inevitably, HMGB1 also orchestrates the support of stressed but illegitimate tissues: tumors. Concomitantly, HMGB1 enhances the immunogenicity of mutated proteins in the tumor (neoantigens), promoting anti‐tumor responses and immunological memory. Tweaking the activities of HMGB1 in inflammation, immune responses and tissue repair could bring large rewards in the therapy of multiple medical conditions, including cancer.
CXCR4 is a G-Protein coupled receptor that is expressed nearly ubiquitously and is known to control cell migration via its interaction with CXCL12, the most ancient chemokine. The functions of ...CXCR4/CXCL12 extend beyond cell migration and involve the recognition and disposal of unhealthy or tumor cells. The CXCR4/CXCL12 axis plays a relevant role in shaping the tumor microenvironment (TME), mainly towards dampening immune responses. Notably, CXCR4/CXCL12 cross-signal via the T and B cell receptors (TCR and BCR) and co-internalize with CD47, promoting tumor cell phagocytosis by macrophages in an anti-tumor immune process called ImmunoGenic Surrender (IGS). These specific activities in shaping the immune response might be exploited to improve current immunotherapies.
The position of genes in the interphase nucleus and their association with functional landmarks correlate with active and/or silent states of expression. Gene activation can induce chromatin looping ...from chromosome territories (CTs) and is thought to require de novo association with transcription factories. We identify two types of factory: "poised transcription factories," containing RNA polymerase II phosphorylated on Ser5, but not Ser2, residues, which differ from "active factories" associated with phosphorylation on both residues. Using the urokinase-type plasminogen activator (uPA) gene as a model system, we find that this inducible gene is predominantly associated with poised (S5p(+)S2p(-)) factories prior to activation and localized at the CT interior. Shortly after induction, the uPA locus is found associated with active (S5p(+)S2p(+)) factories and loops out from its CT. However, the levels of gene association with poised or active transcription factories, before and after activation, are independent of locus positioning relative to its CT. RNA-FISH analyses show that, after activation, the uPA gene is transcribed with the same frequency at each CT position. Unexpectedly, prior to activation, the uPA loci internal to the CT are seldom transcriptionally active, while the smaller number of uPA loci found outside their CT are transcribed as frequently as after induction. The association of inducible genes with poised transcription factories prior to activation is likely to contribute to the rapid and robust induction of gene expression in response to external stimuli, whereas gene positioning at the CT interior may be important to reinforce silencing mechanisms prior to induction.
Chemokine heterodimers activate or dampen their cognate receptors during inflammation. The CXCL12 chemokine forms with the fully reduced (fr) alarmin HMGB1 a physiologically relevant heterocomplex ...(frHMGB1•CXCL12) that synergically promotes the inflammatory response elicited by the G-protein coupled receptor CXCR4. The molecular details of complex formation were still elusive. Here we show by an integrated structural approach that frHMGB1•CXCL12 is a fuzzy heterocomplex. Unlike previous assumptions, frHMGB1 and CXCL12 form a dynamic equimolar assembly, with structured and unstructured frHMGB1 regions recognizing the CXCL12 dimerization surface. We uncover an unexpected role of the acidic intrinsically disordered region (IDR) of HMGB1 in heterocomplex formation and its binding to CXCR4 on the cell surface. Our work shows that the interaction of frHMGB1 with CXCL12 diverges from the classical rigid heterophilic chemokines dimerization. Simultaneous interference with multiple interactions within frHMGB1•CXCL12 might offer pharmacological strategies against inflammatory conditions.
Boosting antitumor immunity has emerged as a powerful strategy in cancer treatment. While releasing T‐cell brakes has received most attention, tumor recognition by T cells is a pre‐requisite. ...Radiotherapy and certain cytotoxic drugs induce the release of damage‐associated molecular patterns, which promote tumor antigen cross‐presentation and T‐cell priming. Antibodies against the “do not eat me” signal CD47 cause macrophage phagocytosis of live tumor cells and drive the emergence of antitumor T cells. Here we show that CXCR4 activation, so far associated only with tumor progression and metastasis, also flags tumor cells to immune recognition. Both CXCL12, the natural CXCR4 ligand, and BoxA, a fragment of HMGB1, promote the release of DAMPs and the internalization of CD47, leading to protective antitumor immunity. We designate as Immunogenic Surrender the process by which CXCR4 turns in tumor cells to macrophages, thereby subjecting a rapidly growing tissue to immunological scrutiny. Importantly, while CXCL12 promotes tumor cell proliferation, BoxA reduces it, and might be exploited for the treatment of malignant mesothelioma and a variety of other tumors.
Synopsis
Induction of antitumor immunity is a successful strategy in cancer treatment. This study reports that BoxA, a fragment of the alarmin HMGB1, induces tumor remission and antitumor immunity in mouse models of mesothelioma and colon carcinoma.
Both BoxA and the chemokine CXCL12 bind the G‐Protein Coupled Receptor CXCR4.
CXCR4 and CD47 are in contact on the surface of tumor cells and co‐internalize upon CXCR4 engagement by either BoxA or CXCL12.
Both CXCL12 and BoxA induce the phagocytosis of tumor cells by macrophages.
BoxA inhibits tumor cell growth and induces antitumor immunological memory in syngeneic mouse models of mesothelioma or colon carcinoma.
CXCL12 is suggested to mediate a similar response (Immunogenic Surrender) in a fraction of untreated tumor‐bearing mice.
Induction of antitumor immunity is a successful strategy in cancer treatment. This study reports that BoxA, a fragment of the alarmin HMGB1, induces tumor remission and antitumor immunity in mouse models of mesothelioma and colon carcinoma.
In two experiments (N = 160) we predicted and found that an optimised video science communication was more effective than either a press release science communication (Experiment 1) and a ...non‐optimised video science communication (Experiment 2) in promoting (a) a better comprehension of the communication, (b) a higher perceived pleasantness, and (c) a stronger manifest interest in learning more about its findings, as reflected in participants’ explicit requests to receive supplemental material on the communicated and analogous findings. The results were consistent across experiments. They were also not influenced by the content type of the communication. Implications for communication professionals and future research in the field of media, social influence, education, and applied social psychology are discussed.
Malignant Mesothelioma is a highly aggressive cancer, which is difficult to diagnose and treat. Here we describe the molecular, cellular and morphological characterization of a syngeneic system ...consisting of murine AB1, AB12 and AB22 mesothelioma cells injected in immunocompetent BALB/c mice, which allows the study of the interplay of tumor cells with the immune system. Murine mesothelioma cells, like human ones, respond to exogenous High Mobility Group Box 1 protein, a Damage-Associated Molecular Pattern that acts as a chemoattractant for leukocytes and as a proinflammatory mediator. The tumors derived from AB cells are morphologically and histologically similar to human MM tumors, and respond to treatments used for MM patients. Our system largely recapitulates human mesothelioma, and we advocate its use for the study of MM development and treatment.
Background
Malignant mesothelioma (MM) is an aggressive tumor, with a poor prognosis, usually unresectable due to late diagnosis, mainly treated with chemotherapy. BoxA, a truncated form of “high ...mobility group box 1” (HMGB1), acting as an HMGB1 antagonist, might exert a defensive action against MM. We investigated the potential of BoxA for MM treatment using experimental 40-MHz ultrasound and optical imaging (OI) in a murine model.
Methods
Murine MM cells infected with a lentiviral vector expressing the luciferase gene were injected into the peritoneum of 14 BALB/c mice (7 × 10
4
AB1-B/c-LUC cells). These mice were randomized to treatment with BoxA (
n
= 7) or phosphate-buffered saline (controls,
n
= 7). The experiment was repeated with 40 mice divided into two groups (
n
= 20 + 20) and treated as above to confirm the result and achieve greater statistical power. Tumor presence was investigated by experimental ultrasound and OI; suspected peritoneal masses underwent histopathology and immunohistochemistry examination.
Results
In the first experiment, none of the 7 controls survived beyond day 27, whereas 4/7 BoxA-treated mice (57.1%) survived up to day 70. In the second experiment, 6/20 controls (30.0%) and 16/20 BoxA-treated mice (80.0%) were still alive at day 34 (
p
= 0.004). In both experiments, histology confirmed the malignant nature of masses detected using experimental ultrasound and OI.
Conclusion
In our preclinical experience on a murine model, BoxA seems to exert a protective role toward MM. Both experimental ultrasound and OI proved to be reliable techniques for detecting MM peritoneal masses.
Myosin VI is the only myosin that moves toward the minus end of actin filaments, suggesting a unique biological function. Here, we show that myosin VI is present in the nucleus of mammalian cells ...where it colocalizes with newly transcribed mRNA and with RNA polymerase II (RNAPII) and is detected in the RNAPII complex. The colocalization and interaction of myosin VI with RNAPII require transcriptional activity. Chromatin immunoprecipitation (ChIP) demonstrates that myosin VI is recruited to the promoter and intragenic regions of active genes, encoding urokinase plasminogen activator (uPA), eukaryotic initiation factor 6 (p27/eIF6), and low-density lipoprotein receptor (LDLR), but not to noncoding, nonregulatory intergenic regions. Downregulation of myosin VI reduces steady-state mRNA levels of these genes in vivo, and antibodies to myosin VI reduce transcription in vitro. We suggest that myosin VI modulates RNAPII-dependent transcription of active genes, implicating the possibility of an actin-myosin based mechanism of transcription.
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