The transcription regulator YAP controls organ size by regulating cell growth, proliferation and apoptosis. However, whether YAP has a role in innate antiviral immunity is largely unknown. Here we found that YAP negatively regulated an antiviral immune response. YAP deficiency resulted in enhanced innate immunity, a diminished viral load, and morbidity in vivo. YAP blocked dimerization of the transcription factor IRF3 and impeded translocation of IRF3 to the nucleus after viral infection. Notably, virus-activated kinase IKKɛ phosphorylated YAP at Ser403 and thereby triggered degradation of YAP in lysosomes and, consequently, relief of YAP-mediated inhibition of the cellular antiviral response. These findings not only establish YAP as a modulator of the activation of IRF3 but also identify a previously unknown regulatory mechanism independent of the kinases Hippo and LATS via which YAP is controlled by the innate immune pathway.

Exosomes, a specific subclass of the extracellular vesicles secreted by most cell types, play an important role in cell–cell communication by transporting diverse content including protein, mRNA, miRNA, and DNA. This cargo is closely associated with the pathogenesis of most human malignancies. Therefore, it is becoming an urgent demand to be able to isolate exosomes in a simple, efficient, and economical way for scientific research and clinical diagnosis. Here, several conventional and novel nano‐based techniques of exosome isolation and characterization are summarized, and the advantages and disadvantages among them are compared, with the hope that researchers will be provided with an overview in this field to detect and isolate exosomes in a suitable manner, matching the subsequent experiments.

Malignancies can compromise innate immunity, but the mechanisms of this are largely unknown. Here we found that, via tumor-derived exosomes (TEXs), cancers were able to transfer activated epidermal growth factor receptor (EGFR) to host macrophages and thereby suppress innate antiviral immunity. Screening of the human kinome identified the kinase MEKK2 in macrophages as an effector of TEX-delivered EGFR that negatively regulated the antiviral immune response. In the context of experimental tumor implantation, MEKK2-deficient mice were more resistant to viral infection than were wild-type mice. Injection of TEXs into mice reduced innate immunity, increased viral load and increased morbidity in an EGFR- and MEKK2-dependent manner. MEKK2 phosphorylated IRF3, a transcription factor crucial for the production of type I interferons; this triggered poly-ubiquitination of IRF3 and blocked its dimerization, translocation to the nucleus and transcriptional activity after viral infection. These findings identify a mechanism by which cancer cells can dampen host innate immunity and potentially cause patients with cancer to become immunocompromised.

Metastasis is the main cause of death in cancer patients. TGF-β is pro-metastatic for malignant cancer cells. Here we report a loss-of-function screen in mice with metastasis as readout and identify OTUD1 as a metastasis-repressing factor. OTUD1-silenced cancer cells show mesenchymal and stem-cell-like characteristics. Further investigation reveals that OTUD1 directly deubiquitinates the TGF-β pathway inhibitor SMAD7 and prevents its degradation. Moreover, OTUD1 cleaves Lysine 33-linked poly-ubiquitin chains of SMAD7 Lysine 220, which exposes the SMAD7 PY motif, enabling SMURF2 binding and subsequent TβRI turnover at the cell surface. Importantly, OTUD1 is lost in multiple types of human cancers and loss of OTUD1 increases metastasis in intracardial xenograft and orthotopic transplantation models, and correlates with poor prognosis among breast cancer patients. High levels of OTUD1 inhibit cancer stemness and shut off metastasis. Thus, OTUD1 represses breast cancer metastasis by mitigating TGF-β-induced pro-oncogenic responses via deubiquitination of SMAD7.

Cytosolic DNA is an indicator of pathogen invasion or DNA damage. The cytosolic DNA sensor cyclic guanosine monophosphateadenosine monophosphate (cGAMP) synthase (cGAS) detects DNA and then mediates downstream immune responses through the molecule stimulator of interferon genes (STING, also known as MITA, MPYS, ERIS and TMEM173). Recent studies focusing on the roles of the cGAS-STING pathway in evolutionary distant species have partly sketched how the mammalian cGAS-STING pathways are shaped and have revealed its evolutionarily conserved mechanism in combating pathogens. Both this pathway and pathogens have developed sophisticated strategies to counteract each other for their survival. Here, we summarise current knowledge on the interactions between the cGAS-STING pathway and pathogens from both evolutionary and mechanistic perspectives. Deeper insight into these interactions might enable us to clarify the pathogenesis of certain infectious diseases and better harness the cGAS-STING pathway for antimicrobial methods.

Graphical Abstract Highlights d OTUB2 enhances metastasis through Hippo-independent activation of YAP/TAZ signaling d Poly-SUMOylation is required for OTUB2 to interact with and deubiquitinate YAP/TAZ d YAP/TAZ contain a SUMO-interacting motif (SIM) required for binding SUMOylated OTUB2 d EGF treatment or KRAS mutation stabilizes YAP/TAZ by stimulating OTUB2 SUMOylation In Brief Zhang et al. identified OTUB2 as a cancer stemness and metastasis-promoting factor that deubiquitinates and activates YAP/TAZ independent of the Hippo signaling. OTUB2 was induced by EGF/KRAS to be poly-SUMOylated on lysine 233, and this SUMOylation enables it to bind YAP/TAZ through a yetunknown SUMO-interacting motif (SIM). SUMMARY The transcriptional regulators YAP and TAZ play important roles in development, physiology, and tumorigenesis and are negatively controlled by the Hippo pathway. It is yet unknown why the YAP/ TAZ proteins are frequently activated in human malignancies in which the Hippo pathway is still active.Here, by a gain-of-function cancer metastasis screen, we discovered OTUB2 as a cancer stemness and metastasis-promoting factor that deubiquitinates and activates YAP/TAZ. We found OTUB2 to be poly-SUMOylated on lysine 233, and this SUMOylation enables it to bind YAP/TAZ. We also identified a yetunknown SUMO-interacting motif (SIM) in YAP and TAZ required for their association with SUMOylated OTUB2. Importantly, EGF and oncogenic KRAS induce OTUB2 poly-SUMOylation and thereby activate YAP/TAZ. Our results establish OTUB2 as an essential modulator of YAP/TAZ and also reveal a novel mechanism via which YAP/TAZ activity is induced by oncogenic KRAS.

Macrophages orchestrate inflammation and control the promotion or inhibition of tumors and metastasis. Ferumoxytol (FMT), a clinically approved iron oxide nanoparticle, possesses anti-tumor therapeutic potential by inducing pro-inflammatory macrophage polarization. Toll-like receptor 3 (TLR3) activation also potently enhances the anti-tumor response of immune cells. Herein, the anti-tumor potential of macrophages harnessed by FMT combined with the TLR3 agonist, poly (I:C) (PIC), and FP-NPs (nanoparticles composed of amino-modified FMT (FMT-NH2) surface functionalized with PIC) was explored.Methods: Proliferation of B16F10 cells co-cultured with macrophages was measured using immunofluorescence or flow cytometry (FCM). Phagocytosis was analyzed using FCM and fluorescence imaging. FP-NPs were prepared through electrostatic interactions and their properties were characterized using dynamic light scattering, transmission electron microscopy, and gel retardation assay. Anti-tumor and anti-metastasis effects were evaluated in B16F10 tumor-bearing mice, and tumor-infiltrating immunocytes were detected by immunofluorescence staining and FCM.Results: FMT, PIC, or the combination of both hardly impaired B16F10 cell viability. However, FMT combined with PIC synergistically inhibited their proliferation by shifting macrophages to a tumoricidal phenotype with upregulated TNF-α and iNOS, increased NO secretion and augmented phagocytosis induced by NOX2-derived ROS in vitro. Combined treatment with FMT/PIC and FMT-NH2/PIC respectively resulted in primary melanoma regression and alleviated pulmonary metastasis with elevated pro-inflammatory macrophage infiltration and upregulation of pro-inflammatory genes in vivo. In comparison, FP-NPs with properties of internalization by macrophages and accumulation in the lung produced a more pronounced anti-metastatic effect accompanied with decreased myeloid-derived suppressor cells, and tumor-associated macrophages shifted to M1 phenotype. In vitro mechanistic studies revealed that FP-NPs nanoparticles barely affected B16F10 cell viability, but specifically retarded their growth by steering macrophages to M1 phenotype through NF-κB signaling.Conclusion: FMT synergized with the TLR3 agonist PIC either in combination or as a nano-composition to induce macrophage activation for primary and metastatic melanoma regression, and the nano-composition of FP-NPs exhibited a more superior anti-metastatic efficacy.

Transforming growth factor-β (TGF-β) members are key cytokines that control embryogenesis and tissue homeostasis via transmembrane TGF-β type II (TβR II) and type I (TβRI) and serine/threonine kinases receptors. Aberrant activation of TGF-β signaling leads to diseases, including cancer. In advanced cancer, the TGF-β/SMAD pathway can act as an oncogenic factor driving tumor cell invasion and metastasis, and thus is considered to be a therapeutic target. The activity of TGF-β/SMAD pathway is known to be regulated by ubiquitination at multiple levels. As ubiquitination is reversible, emerging studies have uncovered key roles for ubiquitin-removals on TGF-β signaling components by deubiquitinating enzymes (DUBs). In this paper, we summarize the latest findings on the DUBs that control the activity of the TGF-β signaling pathway. The regulatory roles of these DUBs as a driving force for cancer progression as well as their underlying working mechanisms are also discussed.