Cisplatin resistance is a major challenge for systemic therapy against advanced bladder cancer (BC). Little information is available on the regulation of cisplatin resistance and the underlying mechanisms require elucidation. Here, we detected that downregulation of the tumor suppressor, PPP2R2B (a serine/threonine protein phosphatase 2 A regulatory subunit), in BC promoted cell proliferation and migration. What\'s more, low PPP2R2B expression was correlated with cisplatin resistance. In vitro and in vivo experiments verified that PPP2R2B could promote BC sensitivity to cisplatin. In terms of mechanism, we identified a novel function of PPP2R2B as a nucleocytoplasmic transport molecule. PPP2R2B promoted ISG15 entry into the nucleus by mediating binding of IPO5 with ISG15. Nuclear translocation of ISG15 inhibited DNA repair, further increasing ISG15 expression through activation of the STING pathway. Besides, PPP2R2B was down-regulated by SUV39H1-mediated histone 3 lysine 9 trimethylation, which could be restored by the SUV39H1-specific inhibitor, chaetocin. Our data suggest that PPP2R2B expression level is a potential biomarker for chemotherapy response and that chemotherapy in combination with chaetocin may be a feasible treatment strategy for patients with BC.

Although renal cell carcinoma (RCC) is a prevalent type of cancer, the most common pathological subtype, clear cell renal cell carcinoma (ccRCC), still has poorly understood molecular mechanisms of progression. Moreover, interferon-stimulated gene 15 (ISG15) is associated with various types of cancer; however, its biological role in ccRCC remains unclear.This study aimed to explore the role of ISG15 in ccRCC progression.ISG15 expression was upregulated in ccRCC and associated with poor prognosis. RNA sequence analysis and subsequent experiments indicated that ISG15 modulated IL6/JAK2/STAT3 signaling to promote ccRCC proliferation, migration, and invasion. Additionally, our animal experiments confirmed that sustained ISG15 knockdown reduced tumor growth rate in nude mice and promoted cell apoptosis. ISG15 modulates the IL6/JAK2/STAT3 pathway, making it a potential therapeutic target and prognostic biomarker for ccRCC.

The interferon stimulated gene 15 (ISG15), a ubiquitin like protein and its conjugates have been implicated in various human malignancies. However, its role in ovarian cancer progression and metastasis is largely unknown. In high grade serous ovarian cancer (HGSOC), ascites is the major contributor to peritoneal metastasis. In this study, we identified significantly elevated ISG15 protein expression in HGSOC patient ascites, ascites derived primary ovarian cancer cells (POCCs), POCC small extracellular vesicles (sEVs) as well as metastatic tissue. Our results demonstrates that ISG15 increases exocytosis in ascites-derived POCCs by decreasing the endosome-lysosomal fusion, indicating a key role in sEV secretion. Further, knockdown (KD) of ISG15 resulted in a significant decrease in vesicles secretion from HGSOC cells and in vivo mouse models, leading to reduced HGSOC cell migration and invasion. Furthermore, our pre-clinical mouse model studies revealed the influence of vesicular ISG15 on disease progression and metastasis. In addition, knockdown of ISG15 or using the ISG15 inhibitor, DAP5, in combination therapy with carboplatin showed to improve the platinum sensitivity in-vitro and reduce tumour burden in-vivo. We also found that ISG15 expression within sEV represents a promising prognostic marker for HGSOC patients. Our findings suggest that ISG15 is a potential therapeutic target for inhibiting progression and metastasis in HGSOC and that vesicular ISG15 expression could be a promising biomarker in the clinical management of ovarian cancer. Significance: High-grade serous ovarian cancer (HGSOC) has high morbidity and mortality rates, but its progression and metastasis are still poorly understood, and there is an urgent need for early detection and targeted therapies. Our study presents novel findings that implicate ISG15-mediated vesicular proteins in the advancement and spread of HGSOC. These results offer pre-clinical evidence of potential new molecular targets, prognostic markers and therapeutic strategies for HGSOC that could ultimately enhance patient survival.

BACKGROUND: Cancer cells frequently evolve necroptotic resistance to overcome various survival stress during tumorigenesis. However, we have previously showed that necroptosis is widespread in head and neck squamous cell carcinoma (HNSCC) and contributes to tumor progression and poor survival via DAMPs-induced migration and invasiveness in peri-necroptotic tumor cells. This implicated an alternative strategy that cancers cope with necroptotic stress by reprogramming a pro-invasive necroptotic microenvironment (NME). Here, we aim to decipher how necroptotic cells shape the NME and affect HNSCC progression.
METHODS: Both our pre-established cellular necroptotic model and newly established Dox-induce intratumoral necroptosis model were used to investigate how necroptosis affect HNSCC progression. Transcriptomic alterations in peri-necroptotic tumor cells were analyzed by RNA-seq and validated in the NME in mice and patients\' samples. The differential DAMPs compositon among apopotosis. Necrosis, and necroptosis were analyzed by label-free proteomic technique, and the necroptosis-specific DAMPs were then identified and validated. The potential receptor for ISG15 were simulated using molecular docking and further validated by in vitro assays. Then the ISG15-RAGE axis was blocked by either knockdown of necroptotic-ISG15 release and RAGE inhibitor FPS-ZM1, and the impact on tumor progression were tested. Last, we further tested our findings in a HNSCC-patients cohort.
RESULTS: Necroptosis played a crucial role in driving tumor-cell invasiveness and lymphatic metastasis via tumor-type dependent DAMPs-releasing. Mechanistically, necroptotic DAMPs induced peri-necroptotic EMT via NF-κB and STAT3 signaling. Furthermore, intrinsic orchestration between necroptotic and cGAS-STING signaling resulted in producing a group of interferon stimulated genes (ISGs) as HNSCC-dependent necroptotic DAMPs. Among them, ISG15 played an essential role in reprogramming the NME. We then identified RAGE as a novel receptor for extracellular ISG15. Either blockage of ISG15 release or ISG15-RAGE interaction dramatically impeded necroptosis-driven EMT and lymphatic metastasis in HNSCC. Lastly, clinicopathological analysis showed high ISG15 expression in NME. Extensive necroptosis and high tumor-cell RAGE expression correlated with tumor progression and poor survival of HNSCC patients.
CONCLUSIONS: Our data revealed a previously unknown cGAS-ISG15-RAGE dependent reprogramming of the necroptotic microenvironment which converts the necroptotic stress into invasive force to foster HNSCC-cell dissemination. By demonstrating the programmatic production of ISG15 via necroptosis-cGAS orchestration and its downstream signaling through RAGE, we shed light on the unique role of ISG15 in HNSCC progression. Targeting such machineries may hold therapeutic potential for restoring intratumoral survival stress and preventing lymphatic metastasis in HNSCC.

Telomeres, potential biomarkers of aging, are known to shorten with continued cigarette smoke exposure. In order to further investigate this process and its impact on cellular stress and inflammation, we used an in vitro model with cigarette smoke extract (CSE) and observed the downregulation of telomere stabilizing TRF2 and POT1 genes after CSE treatment. hTERT is a subunit of telomerase and a well-known oncogenic marker, which is overexpressed in over 85% of cancers and may contribute to lung cancer development in smokers. We also observed an increase in hTERT and ISG15 expression levels after CSE treatment, as well as increased protein levels revealed by immunohistochemical staining in smokers\' lung tissue samples compared to non-smokers. The effects of ISG15 overexpression were further studied by quantifying IFN-γ, an inflammatory protein induced by ISG15, which showed greater upregulation in smokers compared to non-smokers. Similar changes in gene expression patterns for TRF2, POT1, hTERT, and ISG15 were observed in blood and buccal swab samples from smokers compared to non-smokers. The results from this study provide insight into the mechanisms behind smoking causing telomere shortening and how this may contribute to the induction of inflammation and/or tumorigenesis, which may lead to comorbidities in smokers.

The ubiquitin-like protein ISG15 (interferon-stimulated gene 15) regulates the host response to bacterial and viral infections through its conjugation to proteins (ISGylation) following interferon production. ISGylation is antagonized by the highly specific cysteine protease USP18, which is the major deISGylating enzyme. However, mechanisms underlying USP18\'s extraordinary specificity towards ISG15 remains elusive. Here, we show that USP18 interacts with its paralog USP41, whose catalytic domain shares 97% identity with USP18. However, USP41 does not act as a deISGylase, which led us to perform a comparative analysis to decipher the basis for this difference, revealing molecular determinants of USP18\'s specificity towards ISG15. We found that USP18 C-terminus, as well as a conserved Leucine at position 198, are essential for its enzymatic activity and likely act as functional surfaces based on AlphaFold predictions. Finally, we propose that USP41 antagonizes conjugation of the understudied ubiquitin-like protein FAT10 (HLA-F adjacent transcript 10) from substrates in a catalytic-independent manner. Altogether, our results offer new insights into USP18\'s specificity towards ISG15, while identifying USP41 as a negative regulator of FAT10 conjugation.

The transcription of interferon-stimulated gene 15 (isg15) is induced by type I interferons. ISG15 can covalently modify target proteins through the sequential action of enzymesE1, E2, and E3, a process known as ISGylation. The ISGylation of host proteins is widely involved in immune responses, such as host antiviral defence. Ubiquitin-specific protease 18 (USP18), as a deubiquitinase (DUB), can remove ISG15 conjugated to target proteins and inhibit host immune responses by suppressing the type I interferon signaling. The dynamic balance between ISGylation and deISGylation mediated by ISG15 or USP18 respectively plays a significant role in the tuberculosis. Furthermore, similar to ISG15, USP18 is extensively involved in virus-host interaction. In this review, we summarize the roles of ISGylation and deISGylation in tuberculosis and other important diseases mediated by ISG15 and USP18 respectively, underlying regulator network. Further studies in this aspect will inspire new host-targeted strategies to control important diseases such as tuberculosis.
干扰素诱导基因15 (interferon-stimulated gene 15，isg15)的表达受Ⅰ型干扰素诱导，该基因编码的蛋白ISG15可以分别通过E1、E2和E3酶的作用共价修饰靶蛋白，此过程被称为ISG化(ISGylation)。宿主蛋白的ISG化广泛参与天然免疫例如宿主的抗病毒过程。泛素特异性蛋白酶18 (ubiquitin-specific protease 18，USP18)作为一种去泛素化酶(deubiquitinase，DUB)可以去除靶蛋白偶联的ISG15，并通过抑制Ⅰ型干扰素信号通路来抑制宿主的免疫应答。ISG15介导的ISG化和USP18介导的去ISG化(deISGylation)建立的动态平衡对结核病的发生、发展和转归有重要影响。此外，同ISG15一样，USP18也广泛参与病毒感染和宿主细胞抗病毒反应，多种先天性免疫疾病和免疫信号通路都受到USP18的调节。本文综述了ISG15和USP18相关的研究进展，重点介绍了ISG15介导的ISGylation和USP18介导的去ISG化在结核病及其他重要疾病中的调控作用，以期为靶向宿主蛋白的结核病等重要疾病防治提供新的策略。.

The innate immune response to viruses is formed in part by interferon (IFN)-induced restriction factors, including ISG15, p21, and SAMHD1. IFN production can be blocked by the ISG15-specific protease USP18. HIV-1 has evolved to circumvent host immune surveillance. This mechanism might involve USP18. In our recent studies, we demonstrate that HIV-1 infection induces USP18, which dramatically enhances HIV-1 replication by abrogating the antiviral function of p21. USP18 downregulates p21 by accumulating misfolded dominant negative p53, which inactivates wild-type p53 transactivation, leading to the upregulation of key enzymes involved in de novo dNTP biosynthesis pathways and inactivated SAMHD1. Despite the USP18-mediated increase in HIV-1 DNA in infected cells, it is intriguing to note that the cGAS-STING-mediated sensing of the viral DNA is abrogated. Indeed, the expression of USP18 or knockout of ISG15 inhibits the sensing of HIV-1. We demonstrate that STING is ISGylated at residues K224, K236, K289, K347, K338, and K370. The inhibition of STING K289-linked ISGylation suppresses its oligomerization and IFN induction. We propose that human USP18 is a novel factor that potentially contributes in multiple ways to HIV-1 replication.

Regulating nuclear export precisely is essential for maintaining mRNA homeostasis and impacts tumor progression. However, the mechanisms governing nuclear mRNA export remain poorly elucidated. Herein, it is revealed that the enhanced hypoxic long no-ncoding RNA (lncRNA prostate cancer associated transcript 6 (PCAT6) in breast cancer (BC) promotes the nuclear export of m6A-modified mRNAs, bolstering breast cancer stem cells (BCSCs) stemness and doxorubicin resistance. Clinically, hypoxic PCAT6 correlates with malignant BC features and poor prognosis. Mechanically, PCAT6 functions as a scaffold between interferon-stimulated gene 15 (ISG15) and heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNPA2B1), leading to ISGylation of hnRNPA2B1, thus protecting hnRNPA2B1 from ubiquitination-mediated proteasomal degradation. Interestingly, as an m6A reader, hnRNPA2B1 selectively mediates m6A-tagged mRNAs nuclear export via the Aly/REF export factor (ALYREF)/ nuclear RNA export factor 1 (NXF1) complex, which promotes stemness-related genes expression. HnRNPA2B1 knockdown or mRNA export inhibition can result in the retention of nuclear m6A-tagged mRNA associated with stemness maintenance, which suppresses BCSCs self-renewal and effectively improves the efficacy of doxorubicin therapy. These findings demonstrate the pivotal role of m6A-modified mRNA nuclear export in BC progression, highlighting that the inhibition of m6A-tagged mRNA and its nuclear export is a potential therapeutic strategy for the amelioration of cancer chemotherapy.

Drug-induced liver injury (DILI) is a significant global health issue that poses high mortality and morbidity risks. One commonly observed cause of DILI is acetaminophen (APAP) overdose. GSDME is an effector protein that induces non-canonical pyroptosis. In this study, the activation of GSDME, but not GSDMD, in the liver tissue of mice and patients with APAP-DILI is reported. Knockout of GSDME, rather than GSDMD, in mice protected them from APAP-DILI. Mice with hepatocyte-specific rescue of GSDME reproduced APAP-induced liver injury. Furthermore, alterations in the immune cell pools observed in APAP-induced DILI, such as the replacement of TIM4+ resident Kupffer cells (KCs) by monocyte-derived KCs, Ly6C+ monocyte infiltration, MerTk+ macrophages depletion, and neutrophil increase, reappeared in mice with hepatocyte-specific rescue of GSDME. Mechanistically, APAP exposure led to a substantial loss of interferon-stimulated gene 15 (ISG15), resulting in deISGylation of carbamoyl phosphate synthetase-1 (CPS1), promoted its degradation via K48-linked ubiquitination, causing ammonia clearance dysfunction. GSDME deletion prevented these effects. Delayed administration of dimethyl-fumarate inhibited GSDME cleavage and alleviated ammonia accumulation, mitigating liver injury. This findings demonstrated a previously uncharacterized role of GSDME in APAP-DILI by promoting pyroptosis and CPS1 deISGylation, suggesting that inhibiting GSDME can be a promising therapeutic option for APAP-DILI.