ABL1-dependent OTULIN phosphorylation promotes genotoxic Wnt/β-catenin activation to enhance drug resistance in breast cancers

Upregulation of OTULIN Alleviated Recurrent Pregnancy Loss by Suppressing Trophoblast Dysfunction and NF-κB Signaling Pathway

Recurrent pregnancy loss (RPL) is one of obstetrical diseases with no effective therapy methods. Trophoblast cell dysfunction and inflammation induce embryo implantation insufficiency, thereby resulting in RPL. OTU deubiquitinase with linear linkage specificity (OTULIN) plays a role in regulating the immune response and cell death. However, the role of OTULIN in RPL remains unclear. Spontaneous abortion mouse model and lipopolysaccharide-treated HTR-8/SVneo cells were used to investigate the role of OTULIN in RPL. OTULIN expression was downregulated in the labyrinth trophoblast of RPL mice and LPS-treated trophoblast cells. The embryonic reabsorption rate was decreased in OTULIN-overexpressed spontaneous abortion mice, accompanied with the increase in placental/fetus weight ratio. OTULIN overexpression significantly inhibited apoptosis in vivo and in vitro, as evidenced by the decrease in the activity of caspase 3. The expression of pro-inflammatory cytokines was decreased with OTULIN overexpression. Moreover, OTULIN overexpression decreased p-IκBα/IκBα and p-p65/p65 ratio. The nuclear translocation of NF-κB was suppressed via OTULIN overexpression both in vivo and in vitro. Our study suggested that OTULIN deficiency might cause inflammation and trophoblast abnormalities in RPL. The supplementation with OTULIN might alleviate the development of RPL via inhibiting NF-κB mediated inflammation response.

Ubiquitination of transcription factors in cancer: unveiling therapeutic potential

Transcription factors, pivotal in gene expression regulation, are essential in cancer progression. Their function is meticulously regulated by post-translational modifications, including ubiquitination. This process, which marks proteins for degradation, can either enhance or inhibit the function of transcription factors, contingent on the context. In cancers, dysregulated ubiquitination of transcription factors contributes to the hallmark of uncontrolled growth and survival of tumors. For example, tumor suppressors such as p53 might be degraded prematurely due to abnormal ubiquitination, causing genomic instability. On the other hand, oncogenic transcription factors may gain stability via ubiquitination, thus facilitating tumorigenesis. Targeting the ubiquitin-proteasome system (UPS) therefore could be a viable therapeutic approach in cancer. Emerging treatments aim to block the ubiquitination of oncogenic transcription factors or to stabilize tumor suppressors. This review underscores the critical impact of transcription factor-altered ubiquitination on cancer progression. Additionally, it outlines innovative therapeutic approaches that involve inhibitors or drugs directed at specific ubiquitin E3 ligases and deubiquitinases (DUBs) that regulate transcription factor activity.

Interaction of PHGDH with IGF2BP1 facilitates m6A-dependent stabilization of TCF7L2 mRNA to confer multidrug resistance in gastric cancer

Multidrug resistance (MDR) remains a significant barrier to effective chemotherapy and results in a poor prognosis for gastric cancer (GC). Exploring the mechanism of MDR is highly important for identifying biomarkers for MDR and developing new treatment strategies. In this study, integrative analyses of multiomics and bioinformatics data were combined with experimental validation to explore the mechanism of MDR in GC. We found that phosphoglycerate dehydrogenase (PHGDH), the key rate-limiting enzyme in the serine synthesis pathway, was significantly upregulated in MDR GC cells. PHGDH was found to perform a noncanonical function to promote MDR by activating the Wnt/β-catenin signaling pathway, and this effect is mediated by transcription factor 7-like 2 (TCF7L2), a pivotal co-activator of β-catenin in the Wnt pathway. Specifically, PHGDH stabilizes TCF7L2 mRNA by interacting with insulin-like growth factor 2 mRNA binding protein 1 (IGF2BP1), a key m6A reader, in an m6A-dependent manner, thereby increasing the expression of TCF7L2. Moreover, TCF7L2 binds to the promoter of PHGDH and regulates its expression, which forms a positive feedback loop. This PHGDH/IGF2BP1-TCF7L2 loop contributes to GC MDR and is correlated with a poor prognosis of GC patients.

Prognostic and immunological implications of protein kinases in gastric cancer: a focus on hub gene ABL2 and its impact on the polarization of M2 macrophages

BACKGROUND

Protein kinases are essential cellular signal modulators involved in tumorigenesis, metastasis, immune response, and drug resistance. However, the comprehensive features and clinical significance of protein kinases in gastric cancer (GC) remain inconclusive.

METHODS

We analyzed the transcriptional profiles of protein kinases in GC patients from the GEO and TCGA databases. Based on differentially expressed kinase genes (DE-KGs), a novel cluster was identified to assess its association with patient survival and the tumor microenvironment (TME) in GC. Subsequently, an optimal DE-KGs-based model (DE-KGsM) was determined using 101 machine-learning algorithm combinations. This model was evaluated using multi-omics data to investigate its associations with patient prognosis, clinical features, tumor microenvironment, tumor-infiltrating immune cells (TIICs), and immunotherapy response. Furthermore, scRNA-seq analysis and TIMER algorithm were applied to determine the correlation between the hub gene (ABL2) in the DE-KGsM and Macrophages. Finally, in vitro experiments were performed to explore the immune-related mechanisms of ABL2 in GC.

RESULTS

We identified two molecular subtypes of GC patients based on 64 DE-KGs expression. Significant differences were observed in overall survival and TIIC characteristics between Cluster 1 and Cluster 2. Among these 64 DE-KGs, we identified an optimal DE-KGsM that could be a prognostic indicator in GC. TIICs and TIDE analyses exhibited that GC patients in the high-DE-KGsM score group had a higher proportion of M2 macrophages and lower response rates to ICI treatment. scRNA-seq analysis indicated that ABL2 might play an indispensable role in tumor immunity. Furthermore, in vitro experiments demonstrated that ABL2 accelerated the proliferation, migration, and invasion of GC cells, as well as the polarization of M2 macrophages.

CONCLUSIONS

The DE-KGsM could be a powerful predictor of GC patients' survival and might facilitate the development of personalized therapy. Furthermore, as a hub gene in the DE-KGsM, ABL2 could be an immunological biomarker that modulates the polarization of M2 macrophages, thereby promoting GC progression.

CLINICAL TRIAL NUMBER

Not applicable.

Cancer-associated fibroblasts promote doxorubicin resistance in triple-negative breast cancer through enhancing ZFP64 histone lactylation to regulate ferroptosis

BACKGROUND

Cancer-associated fibroblasts (CAFs) have been identified to drive chemotherapy resistance in triple-negative breast cancer (TNBC). This study evaluated the functions of CAFs-mediated suppressive ferroptosis in doxorubicin (DOX) resistance in TNBC and its detailed molecular mechanisms.

METHODS

TNBC cell lines were co-cultured with CAFs isolated from DOX-sensitive (CAF/S) or DOX-resistant (CAF/R) breast cancer tissues. Cell viability and death were assessed by cell counting Kit-8 (CCK-8) and propidium iodide (PI) staining. Ferroptosis was evaluated by detection of Fe2+, malondialdehyde (MDA), glutathione (GSH), and lipid reactive oxygen species (ROS) levels. Histone lactylation was determined by lactate production, pan-Kla and H3K18la expression. Molecular mechanism was determined by chromatin immunoprecipitation (ChIP) and dual luciferase reporter system. Molecule and protein expression was detected by quantitative Real-Time PCR (RT-qPCR), Western blotting, immunofluorescence and immunohistochemical staining. TNBC cells were injected into the mammary fat pad of nude mice to investigate DOX sensitivity in vivo.

RESULTS

CAFs-derived lactate repressed ferroptosis to confer resistance of TNBC cells to DOX. Moreover, zinc finger protein 64 (ZFP64) expression was elevated in DOX-resistant TNBC and was associated with high histone lactylation level. CAFs facilitated histone lactylation to enhance ZFP64 expression, which triggered ferroptosis inhibition and DOX resistance. In addition, ZFP64 bound to the promoters of GTP cyclohydrolase-1 (GCH1) and ferritin heavy chain 1 (FTH1), thereby promoting their expression. Rescue experiments indicated that ZFP64 silencing-induced ferroptosis and high sensitivity of TNBC cells to DOX could be counteracted by GCH1 or FTH1 overexpression.

CONCLUSION

CAFs acted as a ferroptosis inhibitor to cause DOX resistance of TNBC via histone lactylation-mediated ZFP64 up-regulation and subsequent promotion of GCH1-induced lipid peroxidation inhibition and FTH1-induced intracellular Fe2+ consumption.

Hsa_circ_0125356 promotes gemcitabine resistance by modulating WNT canonical and non-canonical pathways via miR-582-5p/FGF9 axis in non-small cell lung cancer

BACKGROUND

Non-small cell lung cancer (NSCLC) is the leading cause of cancer morbidity and mortality worldwide. The prognosis of patients has been significantly improved by chemotherapy, but acquired drug resistance remains a major obstacle to NSCLC treatment. Circular RNAs (circRNAs), which act as miRNA or protein sponges, are critically associated with the development and chemotherapy resistance of NSCLC.

METHODS

CircRNA sequencing was performed to analyze the differential expression of circRNAs between A549 and A549-GR cells. Chromogenic in situ hybridization (CISH) and immunohistochemistry (IHC) technologies were used to detect the expression of hsa_circ_0125356, miR-582-5p,and FGF9 in NSCLC tissues and para-carcinoma tissues. Fluorescence in situ hybridization (FISH), dual-luciferase reporter assays and RNA immunoprecipitation (RIP) were conducted to evaluate the expression and regulation of hsa_circ_0125356, miR-582-5p, and FGF9. Furthermore, the regulation of hsa_circ_0125356/miR-582-5p/FGF9 on gemcitabine sensitivity was confirmed by TUNEL, Transwell, EdU, CCK8 and immunohistochemistry.

RESULTS

We identified a novel hsa_circ_0125356 as a therapeutic target against gemcitabine resistance. Hsa_circ_0125356 was significantly elevated in clinical samples of patients with NSCLC. Moreover, hsa_circ_0125356 overexpression promoted gemcitabine resistance to NSCLC by upregulating FGF9 via sponging miR-582-5p in vivo and in vitro. Notably, WNT canonical (ERK/GSK3β/β-catenin) and non-canonical (Daam1/RhoA/ROCK2) signaling pathways were activated due to hsa_circ_0125356 acting as an endogenous miR-582-5p sponge to regulate the expression of FGF9, and thereby enhancing gemcitabine resistance via promoting DNA damage repair and inhibition of apoptosis. The results were further confirmed by two small molecule antagonists, WAY 316606 and XAV-939,which could inhibit the activation of WNT signaling pathway induced by hsa_circ_0125356.

CONCLUSION

We first demonstrated that hsa_circ_0125356 was significantly upregulated and served as a biomarker for gemcitabine resistance in NSCLC by sponging miR-582-5p/FGF9 axis to regulate the WNT canonical and non-canonical signaling pathways, which provided a new direction for identification of therapeutic targets for the treatment of gemcitabine resistance of NSCLC.

LRP5 enhances glioma cell proliferation by modulating the MAPK/p53/cdc2 pathway

Background: Glioma is a malignant neoplasm with generally poor prognosis and the treatment options and effective drugs are very limited. LRP5, a member of the low-density lipoprotein receptor (LDLR) gene family, has been reported to regulate the progression of various cancers such as gastric and colorectal cancer. However, the function of LRP5 in glioma has not been elucidated. The objective of this study is to explore the influence of LRP5 in glioma cell proliferation and its potential molecular mechanisms. Methods: LRP5 expression in glioma was assessed through bioinformatics analysis, and validation was conducted using clinical glioma tissues. Glioma cell lines with reduced LRP5 expression were established through RNA interference. A series of experiments such as cell proliferation assay, flow cytometry analysis, and Western blotting were used to determine the role of LRP5 in glioma cell proliferation, cell cycle progression, and the underlying mechanisms. Results: LRP5 was found to be upregulated in glioma tissues and exhibited significant variations across various subtypes of glioblastoma (GBM). When differentiating between normal individuals and glioma patients, the area under the receiver operating characteristic curve (ROC) for LRP5 was determined to be 0.981. Downregulating the expression of LRP5 in glioma cells can weaken their proliferative ability and reduce the number of cell colonies. There were more cells arrested in the G2/M phase of the cell cycle. The protein levels of phospho-p53 (p-p53), p21Cip1, and phospho-cdc2 (p-cdc2) were elevated. Moreover, LRP5 down-regulation suppressed the phosphorylation of the mitogen-activated protein kinase (MAPK) family members, JNK and p38 MAPK. Consistent results with those mentioned above can be achieved by using an LRP5 antagonist named DKK-1. Conclusion: This research has identified that LRP5 may promote glioma proliferation by influencing the G2/M transition and the activation of the MAPK/p53/cdc2 pathways, suggesting its value as a potential molecular target for glioma diagnosis and treatment.

Patterns of immune evasion in triple-negative breast cancer and new potential therapeutic targets: a review

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer characterized by the absence of progesterone and estrogen receptors and low (or absent) HER2 expression. TNBC accounts for 15-20% of all breast cancers. It is associated with younger age, a higher mutational burden, and an increased risk of recurrence and mortality. Standard treatment for TNBC primarily relies on cytotoxic agents, such as taxanes, anthracyclines, and platinum compounds for both early and advanced stages of the disease. Several targeted therapies, including bevacizumab and sunitinib, have failed to demonstrate significant clinical benefit in TNBC. The emergence of immune checkpoint inhibitors (ICI) has revolutionized cancer treatment. By stimulating the immune system, ICIs induce a durable anti-tumor response across various solid tumors. TNBC is a particularly promising target for treatment with ICIs due to the higher levels of tumor-infiltrating lymphocytes (TIL), increased PD-L1 expression, and higher mutational burden, which generates tumor-specific neoantigens that activate immune cells. ICIs administered as monotherapy in advanced TNBC yields only a modest response; however, response rates significantly improve when ICIs are combined with cytotoxic agents, particularly in tumors expressing PD-L1. Pembrolizumab is approved for use in both early and advanced TNBC in combination with standard chemotherapy. However, more research is needed to identify more potent biomarkers, and to better elucidate the synergism of ICIs with other targeted agents. In this review, we explore the challenges of immunotherapy in TNBC, examining the mechanisms of tumor progression mediated by immune cells within the tumor microenvironment, and the signaling pathways involved in both primary and acquired resistance. Finally, we provide a comprehensive overview of ongoing clinical trials underway to investigate novel immune-targeted therapies for TNBC.

Deubiquitinases as novel therapeutic targets for diseases

Deubiquitinating enzymes (DUBs) regulate substrate ubiquitination by removing ubiquitin or cleaving within ubiquitin chains, thereby maintaining cellular homeostasis. Approximately 100 DUBs in humans counteract E3 ubiquitin ligases, finely balancing ubiquitination and deubiquitination processes to maintain cellular proteostasis and respond to various stimuli and stresses. Given their role in modulating ubiquitination levels of various substrates, DUBs are increasingly linked to human health and disease. Here, we review the DUB family, highlighting their distinctive structural characteristics and chain-type specificities. We show that DUB family members regulate key signaling pathways, such as NF-κB, PI3K/Akt/mTOR, and MAPK, and play crucial roles in tumorigenesis and other diseases (neurodegenerative disorders, cardiovascular diseases, inflammatory disorders, and developmental diseases), making them promising therapeutic targets Our review also discusses the challenges in developing DUB inhibitors and underscores the critical role of the DUBs in cellular signaling and cancer. This comprehensive analysis enhances our understanding of the complex biological functions of the DUBs and underscores their therapeutic potential.

OTULIN Can Improve Spinal Cord Injury by the NF-κB and Wnt/β-Catenin Signaling Pathways

Spinal cord injury (SCI) is a significant health concern, as it presently has no effective treatment in the clinical setting. Inflammation is a key player in the pathophysiological process of SCI, with a number of studies evidencing that the inhibition of the NF-κB signaling pathway may impede the inflammatory response and improve SCI. OTULIN, as a de-ubiquitination enzyme, the most notable is its anti-inflammatory effect. OTULIN can inhibit the NF-κB signaling pathway to suppress the inflammatory reaction via de-ubiquitination. In addition, OTULIN may promote vascular regeneration through the Wnt/β-catenin pathway in the wake of SCI. In this review, we analyze the structure and physiological function of OTULIN, along with both NF-κB and Wnt/β-catenin signaling pathways. Furthermore, we examine the significant role of OTULIN in SCI through its impairment of the NF-κB signaling pathway, which could open the possibility of it being a novel interventional target for the condition.

Exploring and validating the necroptotic gene regulation and related lncRNA mechanisms in colon adenocarcinoma based on multi-dimensional data

Necroptosis is intimately associated with the initiation and progression of colon adenocarcinoma (COAD). However, studies on necroptosis-related genes (NRGs) and the regulating long non-coding RNAs (NRGlncRNAs) in the context of COAD are limited. We retrieved the cancer genome atlas (TCGA) to collect datasets of NRGs and NRGlncRNAs on COAD patients. The risk model constructed using Cox and least absolute shrinkage and selection operator (LASSO) regression was then employed to identify NRGs and NRGlncRNAs with prognostic significance. Subsequently, we validated the results using gene expression omnibus (GEO) datasets from different populations, conducted Mendelian randomization (MR) analysis to explore the potential causal relationships between prognostic NRGs and COAD, and conducted cell experiments to verify the expression of prognostic NRGlncRNAs in COAD. Furthermore, we explored potential pathways and regulatory mechanisms of these prognostic NRGlncRNAs and NRGs in COAD through enrichment analysis, immune cell correlation analysis, tumor microenvironment analysis, immune checkpoint analysis, tumor sample clustering, and so on. We identified eight NRGlncRNAs (AC245100.5, AP001619.1, LINC01614, AC010463.3, AL162595.1, ITGB1-DT, LINC01857, and LINC00513) used for constructing the prognostic model and nine prognostic NRGs (AXL, BACH2, CFLAR, CYLD, IPMK, MAP3K7, ATRX, BRAF, and OTULIN) with regulatory relationships with them, and their validation was performed using GEO and GWAS datasets, as well as cell experiments, which showed largely consistent results. These prognostic NRGlncRNAs and NRGs modulate various biological functions, including immune inflammatory response, oxidative stress, immune escape, telomere regulation, and cytokine response, influencing the development of COAD. Additionally, stratified analysis of the high-risk and low-risk groups based on the prognostic model revealed elevated expression of immune cells, increased expression of tumor microenvironment cells, and upregulation of immune checkpoint gene expression in the high-risk group. Finally, through cluster analysis, we identified tumor subtypes, and the results of cluster analysis were essentially consistent with the analysis between risk groups. The prognostic NGRlncRNAs and NRGs identified in our study serve as prognostic indicators and potential therapeutic targets for COAD, providing a theoretical basis for the clinical diagnosis and treatment of COAD and offering guidance for further research.

Met1-linked ubiquitination in cell signaling regulation

Met1-linked ubiquitination (Met1-Ub), also known as linear ubiquitination, is a newly identified atypical type of polyubiquitination that is assembled via the N-terminal methionine (Met1) rather than an internal lysine (Lys) residue of ubiquitin. The linear ubiquitin chain assembly complex (LUBAC) composed of HOIP, HOIL-1L and SHARPIN is the sole E3 ubiquitin ligase that specifically generates Met1-linked ubiquitin chains. The physiological role of LUBAC-mediated Met1-Ub has been first described as activating NF-κB signaling through the Met1-Ub modification of NEMO. However, accumulating evidence shows that Met1-Ub is broadly involved in other cellular pathways including MAPK, Wnt/β-Catenin, PI3K/AKT and interferon signaling, and participates in various cellular processes including angiogenesis, protein quality control and autophagy, suggesting that Met1-Ub harbors a potent signaling capacity. Here, we review the formation and cellular functions of Met1-linked ubiquitin chains, with an emphasis on the recent advances in the cellular mechanisms by which Met1-Ub controls signaling transduction.

Ubiquitination and deubiquitination in cancer: from mechanisms to novel therapeutic approaches

Ubiquitination, a pivotal posttranslational modification of proteins, plays a fundamental role in regulating protein stability. The dysregulation of ubiquitinating and deubiquitinating enzymes is a common feature in various cancers, underscoring the imperative to investigate ubiquitin ligases and deubiquitinases (DUBs) for insights into oncogenic processes and the development of therapeutic interventions. In this review, we discuss the contributions of the ubiquitin-proteasome system (UPS) in all hallmarks of cancer and progress in drug discovery. We delve into the multiple functions of the UPS in oncology, including its regulation of multiple cancer-associated pathways, its role in metabolic reprogramming, its engagement with tumor immune responses, its function in phenotypic plasticity and polymorphic microbiomes, and other essential cellular functions. Furthermore, we provide a comprehensive overview of novel anticancer strategies that leverage the UPS, including the development and application of proteolysis targeting chimeras (PROTACs) and molecular glues.

OTULIN of exosomes derived from Schwann cells promotes peripheral nerve injury repair by regulating macrophage polarization via deubiquitination of ERBB2

A significant public health burden is peripheral nerve damage (PNI), which is frequently brought on by trauma. Macrophages were essential to the effective regeneration of nerves and restoration of function. It is still not entirely understood how macrophages and Schwann cells interact after damage during remyelination. Here, we established an inflammatory model in bone marrow-derived macrophages (BMDMs) and a rat sciatic nerve damage model to investigate the possible relationship between lipopolysaccharides (LPS)-induced exosomes derived from Schwann cells (LPS SCs-Exos) and peripheral nerve repair. The pro-inflammatory macrophage was changed into a pro-regeneration macrophage by LPS SC-Exos. Notably, it was discovered that SC-Exos had a substantial enrichment of OTULIN. OTULIN was a key mediator in the regulatory effects of LPS SC-Exos by deubiquitinating ERBB2 and preventing its degradation. The local injection of SC-Exos into the nerve damage site led in a faster functional recovery, axon regeneration and remyelination, and an increased M2 macrophage polarization, whereas OTULIN knockdown reversed these effects in vivo. Our results indicate that LPS SC-Exos may offer a therapeutic avenue for peripheral nerve regeneration by promoting macrophage polarization toward an M2 phenotype through the shuttling of OTULIN and deubiquitination of ERBB2. SIGNIFICANCE STATEMENT: OTULIN protein from SC-Exos mediated the macrophages polarization and axonal growth in BMDMs through promoting ubiquitination of ERBB2 and triggering the degradation of ERBB2. The findings offered prospective therapeutic hints for PNI therapy approaches that target axonal regrowth.

YAP1-induced RBM24 promotes the tumorigenesis of triple-negative breast cancer through the β-catenin pathway

Triple-negative breast cancer (TNBC) is the most aggressive breast cancer subtype and refractory to current treatments. RBM24 is an RNA-binding protein and shows the ability to regulate tumor progression in multiple cancer types. However, its role in TNBC is still unclear. In this study, we analyzed publicly available profiling data from TNBC tissues and cells. Loss- and gain-of-function experiments were performed to determine the function of RBM24 in TNBC cells. The mechanism for RBM24 action in TNBC was investigated. RBM24 was deregulated in TNBC tissues and TNBC cells with depletion of SIPA1, YAP1, or ARID1A, three key regulators of TNBC. Compared to MCF10A breast epithelial cells, TNBC cells had higher levels of RBM24. Knockdown of RBM24 inhibited TNBC cell proliferation, colony formation, and tumorigenesis, while overexpression of RBM24 promoted aggressive phenotype in TNBC cells. YAP1 overexpression induced the expression of RBM24 and the RBM24 promoter-driven luciferase reporter. YAP1 was enriched at the promoter region of RBM24. Overexpression of RBM24 increased β-catenin-dependent transcriptional activity. Most importantly, knockdown of CTNNB1 rescued RBM24 aggressive phenotype in TNBC cells. Collectively, the YAP1/RBM24/β-catenin axis plays a critical role in driving TNBC progression. RBM24 may represent a novel therapeutic target for TNBC treatment.

OTULIN deficiency: focus on innate immune system impairment

OTULIN deficiency is a complex disease characterized by a wide range of clinical manifestations, including skin rash, joint welling, lipodystrophy to pulmonary abscess, and sepsis shock. This disease is mechanistically linked to mutations in the OTULIN gene, resulting in an immune disorder that compromises the body's ability to effectively combat pathogens and foreign stimuli. The OTULIN gene is responsible for encoding a deubiquitinating enzyme crucial for hydrolyzing Met1-poly Ub chains, and its dysfunction leads to dysregulated immune responses. Patients with OTULIN deficiency often exhibit an increase in monocytes, including neutrophils and macrophages, along with inflammatory clinical features. The onset of symptoms typically occurs at an early age. However, individuals with OTULIN haploinsufficiency are particularly susceptible to life-threatening staphylococcal infections. Currently, the most effective treatment for patients with OTULIN biallelic mutations involves the use of TNF-blocking agents, which target the dysregulated immune response. In conclusion, OTULIN deficiency presents a complex clinical picture with diverse manifestations, attributed to mutations in the OTULIN gene. Understanding the underlying mechanisms is crucial for developing targeted therapeutic interventions to address this challenging condition. Further research into the pathophysiology of OTULIN deficiency is essential for improving clinical management and outcomes for affected individuals.

New insights in ubiquitin-dependent Wnt receptor regulation in tumorigenesis

Wnt signaling plays a crucial role in embryonic development and homeostasis maintenance. Delicate and sensitive fine-tuning of Wnt signaling based on the proper timings and positions is required to balance cell proliferation and differentiation and maintain individual health. Therefore, homeostasis is broken by tissue hypoplasia or tumor formation once Wnt signal dysregulation disturbs the balance of cell proliferation. The well-known regulatory mechanism of Wnt signaling is the molecular reaction associated with the cytoplasmic accumulation of effector β-catenin. In addition to β-catenin, most Wnt effector proteins are also regulated by ubiquitin-dependent modification, both qualitatively and quantitatively. This review will explain the regulation of the whole Wnt signal in four regulatory phases, as well as the different ubiquitin ligases and the function of deubiquitinating enzymes in each phase. Along with the recent results, the mechanism by which RNF43 negatively regulates the surface expression of Wnt receptors, which has recently been well understood, will be detailed. Many RNF43 mutations have been identified in pancreatic and gastrointestinal cancers and examined for their functional alteration in Wnt signaling. Several mutations facilitate or activate the Wnt signal, reversing the RNF43 tumor suppressor function into an oncogene. RNF43 may simultaneously play different roles in classical multistep tumorigenesis, as both wild-type and mutant RNF43 suppress the p53 pathway. We hope that the knowledge obtained from further research in RNF43 will be applied to cancer treatment in the future despite the fully unclear function of RNF43.

Systematic HOIP interactome profiling reveals critical roles of linear ubiquitination in tissue homeostasis

Linear ubiquitination catalyzed by HOIL-1-interacting protein (HOIP), the key component of the linear ubiquitination assembly complex, plays fundamental roles in tissue homeostasis by executing domain-specific regulatory functions. However, a proteome-wide analysis of the domain-specific interactome of HOIP across tissues is lacking. Here, we present a comprehensive mass spectrometry-based interactome profiling of four HOIP domains in nine mouse tissues. The interaction dataset provides a high-quality HOIP interactome resource with an average of approximately 90 interactors for each bait per tissue. HOIP tissue interactome presents a systematic understanding of linear ubiquitination functions in each tissue and also shows associations of tissue functions to genetic diseases. HOIP domain interactome characterizes a set of previously undefined linear ubiquitinated substrates and elucidates the cross-talk among HOIP domains in physiological and pathological processes. Moreover, we show that linear ubiquitination of Integrin-linked protein kinase (ILK) decreases focal adhesion formation and promotes the detachment of Shigella flexneri-infected cells. Meanwhile, Hoip deficiency decreases the linear ubiquitination of Smad ubiquitination regulatory factor 1 (SMURF1) and enhances its E3 activity, finally causing a reduced bone mass phenotype in mice. Overall, our work expands the knowledge of HOIP-interacting proteins and provides a platform for further discovery of linear ubiquitination functions in tissue homeostasis.

Deciphering drug resistance in gastric cancer: Potential mechanisms and future perspectives

Gastric cancer (GC) is a malignant tumor that originates from the epithelium of the gastric mucosa. The latest global cancer statistics show that GC ranks fifth in incidence and fourth in mortality among all cancers, posing a serious threat to public health. While early-stage GC is primarily treated through surgery, chemotherapy is the frontline option for advanced cases. Currently, commonly used chemotherapy regimens include FOLFOX (oxaliplatin + leucovorin + 5-fluorouracil) and XELOX (oxaliplatin + capecitabine). However, with the widespread use of chemotherapy, an increasing number of cases of drug resistance have emerged. This article primarily explores the potential mechanisms of chemotherapy resistance in GC patients from five perspectives: cell death, tumor microenvironment, non-coding RNA, epigenetics, and epithelial-mesenchymal transition. Additionally, it proposes feasibility strategies to overcome drug resistance from four angles: cancer stem cells, tumor microenvironment, natural products, and combined therapy. The hope is that this article will provide guidance for researchers in the field and bring hope to more GC patients.

UCHL3 inhibits ferroptosis by stabilizing β-catenin and maintains stem-like properties of hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is the most common type of primary hepatic liver cancer. Dysregulated Wnt/β-catenin activation is closely related to the progression of cancer. Nevertheless, the mechanism that sustains the abnormal expression of β-catenin in HCC has yet to be identified. In this study, we find that UCHL3 is overexpressed in HCC tissues and correlated with β-catenin protein level. High expression of UCHL3 is associated with poor prognosis. UCHL3 knockdown markedly reduces the protein level of β-catenin in HCC cells. TOP-luciferase activity and β-catenin target genes expression are also decreased upon UCHL3 depletion. We find that the ARM domain of β-catenin is required for the interaction with UCHL3. UCHL3 increases β-catenin protein stability via removing K48-specific poly-ubiquitin chains from β-catenin protein. Furthermore, the depletion of UCHL3 induces ferroptosis and hinders the growth, invasion, and stem cell properties of HCC cells. These impacts could be restored by the overexpression of β-catenin. In addition, the UCHL3 inhibitor TCID inhibits the aggressive phenotype of HCC through the degradation of β-catenin. In general, our results indicates that UCHL3 increases the stability of β-catenin, which in turn facilitates tumorigenesis of HCC, suggesting that targeting UCHL3 may be a promising approach for the treatment of HCC.

LUBAC promotes angiogenesis and lung tumorigenesis by ubiquitinating and antagonizing autophagic degradation of HIF1α

Hypoxia-inducible factor 1 (HIF1) is critically important for driving angiogenesis and tumorigenesis. Linear ubiquitin chain assembly complex (LUBAC), the only known ubiquitin ligase capable of catalyzing protein linear ubiquitination to date, is implicated in cell signaling and associated with cancers. However, the role and mechanism of LUBAC in regulating the expression and function of HIF1α, the labile subunit of HIF1, remain to be elucidated. Herein we showed that LUBAC increases HIF1α protein expression in cultured cells and tissues of human lung cancer and enhances HIF1α DNA-binding and transcriptional activities, which are dependent upon LUBAC enzymatic activity. Mechanistically, LUBAC increases HIF1α stability through antagonizing HIF1α decay by the chaperone-mediated autophagy (CMA)-lysosome pathway, thereby potentiating HIF1α activity. We further demonstrated that HIF1α selectively interacts with HOIP (the catalytic subunit of LUBAC) primarily in the cytoplasm. LUBAC catalyzes linear ubiquitination of HIF1α at lysine 362. Linear ubiquitination shields HIF1α from interacting with heat-shock cognate protein of 70 kDa and lysosome-associated membrane protein type 2 A, two components of CMA. Consequently, linear ubiquitination confers protection against CMA-mediated destruction of HIF1α, increasing HIF1α stability and activity. We found that prolyl hydroxylation is not a perquisite for LUBAC's effects on HIF1α. Functionally, LUBAC facilitates proliferation, clonogenic formation, invasion and migration of lung cancer cells. LUBAC also boosts angiogenesis and exacerbates lung cancer growth in mice, which are greatly compromised by inhibition of HIF1α. This work provides novel mechanistic insights into the role of LUBAC in regulating HIF1α homeostasis, tumor angiogenesis and tumorigenesis of lung cancer, making LUBAC an attractive therapeutic target for cancers.

Combination therapy of niclosamide with gemcitabine inhibited cell proliferation and apoptosis via Wnt/β-catenin/c-Myc signaling pathway by inducing β-catenin ubiquitination in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a type of cancer with high morbidity and mortality rates worldwide. Owing to a lack of therapeutic options, the overall survival rate of patients with pancreatic cancer is low. Gemcitabine has been mainly used to treat patients with pancreatic cancer, but its efficacy is limited by chemoresistance. Therefore, a novel therapeutic agent for PDAC therapy is urgently needed. An anthelminthic drug, niclosamide, has already been researched in breast, lung, colon, and pancreatic cancer as an anti-cancer purpose by re-positioning its original purpose. However, combination therapy of gemcitabine and niclosamide was not informed yet. Here, we found that niclosamide co-administered with gemcitabine significantly inhibited tumorigenesis of pancreatic cancer compared to gemcitabine alone. Further, combining niclosamide and gemcitabine inhibited cell proliferation and induced apoptosis. Niclosamide induced cell cycle arrest at the G1 phase, and the levels of CDK4/6 and cyclin D1 were lowered after gemcitabine treatment. In addition, the combination of these chemical compounds more effectively increased the binding level of activated β-catenin destruction complex and β-catenin to enable phosphorylation, compared to gemcitabine alone. After phosphorylation, niclosamide - gemcitabine upregulated the ubiquitin level, which caused phosphorylated β-catenin to undergo proteasomal degradation; the combination was more potent than gemcitabine alone. Finally, the combination more effectively suppressed tumor growth in vivo, compared to gemcitabine alone. Altogether, our results indicate that niclosamide synergistically enhances the antitumor effect of gemcitabine in pancreatic cancer, by inducing the degradation of β-catenin with ubiquitination. Therefore, this drug combination can potentially be used in PDAC therapy.

USP7 promotes non-small-cell lung cancer cell glycolysis and survival by stabilizing and activating c-Abl

BACKGROUND

Abelson tyrosine kinase (c-Abl) is frequently mutated and highly expressed, and promotes non-small-cell lung cancer (NSCLC) survival, metastasis and tumorigenesis. c-Abl could also be modified through ubiquitination, but the underlying mechanism is not well understood.

METHODS

Mass spectrometry assays were performed to search c-Abl deubiquitination enzymes. The molecular mechanism was determined using Co-IP assays, pull-down assays, Western blotting upon gene knockdown or overexpression. Cell lines and animal models were used to investigate the role of c-Abl and USP7 in NSCLC. EdU staining assay and Transwell assay were performed to evaluate the proliferation and migration ability of NSCLC cells, respectively.

RESULTS

Ubiquitin-specific protease 7 (USP7) is found to upregulate c-Abl via the deubiquitinase screen. USP7 interacts with c-Abl and decreases its K48-linked polyubiquitination, thereby increasing the stability of c-Abl. In addition to the wild-type one, c-Abl mutants can also be deubiquitinated and stabilized by USP7. Moreover, USP7 promotes c-Abl accumulation in cytoplasm by increasing its binding to 14-3-3α/β and activates the oncogenic c-Abl signalling pathway. Furthermore, the USP7/c-Abl axis promotes NSCLC cell glycolysis by direct phosphorylating and stabilizing hexokinase-2 (HK2). Knockdown of USP7 or c-Abl suppresses NSCLC cell glycolysis and reduces lactate production. Further studies revealed that overexpression of USP7 facilitates NSCLC cell growth and metastasis as well as xenograft growth in nude mice, while these activities are suppressed with USP7 or c-Abl being knocked down.

CONCLUSIONS

USP7 is a deubiquitinase of c-Abl and upregulates its oncogenic activity. USP7 promotes NSCLC cell metabolism by activating c-Abl and HK2. Targeting the USP7/c-Abl/HK2 axis might be a potential strategy to the precision therapy of NSCLC.

AURKAIP1 actuates tumor progression through stabilizing DDX5 in triple negative breast cancer

Aurora-A kinase interacting protein 1 (AURKAIP1) has been proved to take an intermediary role in cancer by functioning as a negative regulator of Aurora-A kinase. However, it remains unclear whether and how AURKAIP1 itself would directly engage in regulating malignancies. The expression levels of AURKAIP1 were detected in triple negative breast cancer (TNBC) by immunohistochemistry and western blots. The CCK8, colony formation assays and nude mouse model were conducted to determine cell proliferation whereas transwell and wound healing assays were performed to observe cell migration. The interaction of AURKAIP1 and DEAD-box helicase 5 (DDX5) were verified through co-immunoprecipitation and successively western blots. From the results, we found that AURKAIP1 was explicitly upregulated in TNBC, which was positively associated with tumor size, lymph node metastases, pathological stage and unfavorable prognosis. AURKAIP1 silencing markedly inhibited TNBC cell proliferation and migration in vitro and in vivo. AURKAIP1 directly interacted with and stabilized DDX5 protein by preventing ubiquitination and degradation, and DDX5 overexpression successfully reversed proliferation inhibition induced by knockdown of AURKAIP1. Consequently, AURKAIP1 silencing suppressed the activity of Wnt/β-catenin signaling in a DDX5-dependent manner. Our study may primarily disclose the molecular mechanism by which AURKAIP1/DDX5/β-catenin axis modulated TNBC progression, indicating that AURKAIP1 might serve as a therapeutic target as well as a TNBC-specific biomarker for prognosis.

Mechanisms underlying linear ubiquitination and implications in tumorigenesis and drug discovery

Linear ubiquitination is a distinct type of ubiquitination that involves attaching a head-to-tail polyubiquitin chain to a substrate protein. Early studies found that linear ubiquitin chains are essential for the TNFα- and IL-1-mediated NF-κB signaling pathways. However, recent studies have discovered at least sixteen linear ubiquitination substrates, which exhibit a broader activity than expected and mediate many other signaling pathways beyond NF-κB signaling. Dysregulation of linear ubiquitination in these pathways has been linked to many types of cancers, such as lymphoma, liver cancer, and breast cancer. Since the discovery of linear ubiquitin, extensive effort has been made to delineate the molecular mechanisms of how dysregulation of linear ubiquitination causes tumorigenesis and cancer development. In this review, we highlight newly discovered linear ubiquitination-mediated signaling pathways, recent advances in the role of linear ubiquitin in different types of cancers, and the development of linear ubiquitin inhibitors. Video Abstract.

An interaction between OTULIN and SCRIB uncovers roles for linear ubiquitination in planar cell polarity

Planar cell polarity (PCP) plays critical roles in developmental and homeostatic processes. Membrane presentation of PCP complexes containing Van Gogh-like (VANGL) transmembrane proteins is central to PCP and can be directed by the scaffold protein scribble (SCRIB). The role atypical linear ubiquitin (Met1-Ub) chains might play in PCP is unknown. Here, HEK293 cell-based interactomic analyses of the Met1-Ub deubiquitinase OTULIN revealed that OTULIN can interact with SCRIB. Moreover, Met1-Ub chains associated with VANGL2 and PRICKLE1, but not SCRIB, can direct VANGL2 surface presentation. Mouse embryos lacking Otulin showed variable neural tube malformations, including rare open neural tubes, a deficit associated with PCP disruption in mice. In Madin-Darby canine kidney cells, in which the enrichment of VANGL2-GFP proteins at cell-cell contacts represents activated PCP complexes, endogenous OTULIN was recruited to these sites. In the human MDA-MB-231 breast cancer cell model, OTULIN loss caused deficits in Wnt5a-induced filopodia extension and trafficking of transfected HA-VANGL2. Taken together, these findings support a role for linear (de)ubiquitination in PCP signaling. The association of Met1-Ub chains with PCP complex components offers new opportunities for integrating PCP signaling with OTULIN-dependent immune and inflammatory pathways.

USP8 positively regulates hepatocellular carcinoma tumorigenesis and confers ferroptosis resistance through β-catenin stabilization

Hepatocellular carcinoma (HCC) is the most common type of primary hepatic carcinoma, which is a growing public health problem worldwide. One of the main genetic alterations in HCC is the deregulated Wnt/β-catenin signaling, activation of β-catenin is associated with the progression of HCC. In the present study, we aimed to identify novel modulators in controlling β-catenin ubiquitination and stability. USP8 was overexpressed in HCC tissues and correlated with β-catenin protein level. High expression of USP8 indicated poor prognosis of HCC patients. USP8 depletion significantly decreased β-catenin protein level, β-catenin target genes expression and TOP-luciferase activity in HCC cells. Further mechanistic study revealed that the USP domain of USP8 interacted with the ARM domain of β-catenin. USP8 stabilized β-catenin protein via inhibiting K48-specific poly-ubiquitination process on β-catenin protein. In addition, USP8 depletion inhibited the proliferation, invasion and stemness of HCC cells and conferred ferroptosis resistance, which effects could be further rescued by β-catenin overexpression. In addition, the USP8 inhibitor DUB-IN-3 inhibited the aggressive phenotype and promoted ferroptosis of HCC cells through degradation of β-catenin. Thus, our study demonstrated that USP8 activated the Wnt/beta-catenin signaling through a post-translational mechanism of β-catenin. High expression of USP8 promoted the progression and inhibited ferroptosis of HCC. Targeting the USP8 may serve as a promising strategy for patients with HCC.

IKKα inhibition re-sensitizes acquired adriamycin-resistant triple negative breast cancer cells to chemotherapy-induced apoptosis

IKKα has been shown to be responsible of multiple pro-tumorigenic functions and therapy resistance independent of canonical NF-κB, but its role in acquired chemotherapy resistance in breast cancer remains unclarified. In this study, we obtained pre-treatment biopsy and post-treatment mastectomy specimens from a retrospective cohort of triple-negative breast cancer (TNBC) patients treated with neoadjuvant chemotherapy(NAC) (n = 43). Immunohistochemical methods were used to detect the expression of IKKα before and after NAC, and the relationship between IKKα and the pathologic response to NAC was examined. In addition, we developed a new ADR-resistant MDA-MB-231 cell line(MDA-MB-231/ADR) and analyzed these cells for changes in IKKα expression, the role and mechanisms of the increased IKKα in promoting drug resistance were determined in vitro and in vivo. We demonstrated that the expression of IKKα in residual TNBC tissues after chemotherapy was significantly higher than that before chemotherapy, and was positively correlated with lower pathological reaction. IKKα expression was significantly higher in ADR-resistant TNBC cells than in ADR-sensitive cells, IKKα knockdown results in apoptotic cell death of chemoresistant cells upon drug treatment. Moreover, IKKα knockdown promotes chemotherapeutic drug-induced tumor cell death in an transplanted tumor mouse model. Functionally, we demonstrated that IKKα knockdown significantly upregulated the expression of cleaved caspase 3 and Bax and inhibited the expression of Bcl-2 upon ADR treatment. Our findings highlighted that IKKα exerts an important and previously unknown role in promoting chemoresistance in TNBC, combining IKKα inhibition with chemotherapy may be an effective strategy to improve treatment outcome in chemoresistant TNBC patients.

Biological functions and molecular interactions of Wnt/β-catenin in breast cancer: Revisiting signaling networks

Changes in lifestyle such as physical activity and eating habits have been one of the main reasons for development of various diseases in modern world, especially cancer. However, role of genetic factors in initiation of cancer cannot be ignored and Wnt/β-catenin signaling is such factor that can affect tumor progression. Breast tumor is the most malignant tumor in females and it causes high mortality and morbidity around the world. The survival and prognosis of patients are not still desirable, although there have been advances in introducing new kinds of therapies and diagnosis. The present review provides an update of Wnt/β-catenin function in breast cancer malignancy. The upregulation of Wnt is commonly observed during progression of breast tumor and confirms that tumor cells are dependent on this pathway Wnt/β-catenin induction prevents apoptosis that is of importance for mediating drug resistance. Furthermore, Wnt/β-catenin signaling induces DNA damage repair in ameliorating radio-resistance. Wnt/β-catenin enhances proliferation and metastasis of breast tumor. Wnt/β-catenin induces EMT and elevates MMP expression. Furthermore, Wnt/β-catenin participates in tumor microenvironment remodeling and due to its tumor-promoting factor, drugs for its suppression have been developed. Different kinds of upstream mediators Wnt/β-catenin signaling in breast cancer have been recognized that their targeting is a therapeutic approach. Finally, Wnt/β-catenin can be considered as a biomarker in clinical trials.

Identification of immunotherapy and chemotherapy-related molecular subtypes in colon cancer by integrated multi-omics data analysis

Background

Colon cancer is a highly heterogeneous disease, and identifying molecular subtypes can provide insights into deregulated pathways within tumor subsets, which may lead to personalized treatment options. However, most prognostic models are based on single-pathway genes.

Methods

In this study, we aimed to identify three clinically relevant subtypes of colon cancer based on multiple signaling pathways-related genes. Integrative multi-omics analysis was used to explain the biological processes contributing to colon cancer aggressiveness, recurrence, and progression. Machine learning methods were employed to identify the subtypes and provide medication guidance for distinct subtypes using the L1000 platform. We developed a robust prognostic model (MKPC score) based on gene pairs and validated it in one internal test set and three external test sets. Risk-related genes were extracted and verified by qPCR.

Results

Three clinically relevant subtypes of colon cancer were identified based on multiple signaling pathways-related genes, which had significantly different survival state (Log-Rank test, p<0.05). Integrative multi-omics analysis revealed biological processes contributing to colon cancer aggressiveness, recurrence, and progression. The developed MKPC score, based on gene pairs, was robust in predicting prognosis state (Log-Rank test, p<0.05), and risk-related genes were successfully verified by qPCR (t test, p<0.05). An easy-to-use web tool was created for risk scoring and therapy stratification in colon cancer patients, and the practical nomogram can be extended to other cancer types.

Conclusion

In conclusion, our study identified three clinically relevant subtypes of colon cancer and developed a robust prognostic model based on gene pairs. The developed web tool is a valuable resource for researchers and clinicians in risk scoring and therapy stratification in colon cancer patients, and the practical nomogram can be extended to other cancer types.

The origin of gastric cancer stem cells and their effects on gastric cancer: Novel therapeutic targets for gastric cancer

Gastric cancer (GC) is one of the most prevalent malignancies and the most common causes of cancer-related mortality worldwide. Furthermore, the prognosis of advanced GC remains poor even after surgery combined with chemoradiotherapy. As a small group of cells with unlimited differentiation and self-renewal ability in GC, accumulating evidence shows that GC stem cells (GCSCs) are closely associated with the refractory characteristics of GC, such as drug resistance, recurrence, and metastasis. With the extensive development of research on GCSCs, GCSCs seem to be promising therapeutic targets for GC. However, the relationship between GCSCs and GC is profound and intricate, and its mechanism of action is still under exploration. In this review, we elaborate on the source and key concepts of GCSCs, systematically summarize the role of GCSCs in GC and their underlying mechanisms. Finally, we review the latest information available on the treatment of GC by targeting GCSCs. Thus, this article may provide a theoretical basis for the future development of the novel targets based on GCSCs for the treatment of GC.

Reciprocal interplay between OTULIN-LUBAC determines genotoxic and inflammatory NF-κB signal responses

Targeting nuclear factor-kappa B (NF-κB) represents a highly viable strategy against chemoresistance in cancers as well as cell death. Ubiquitination, including linear ubiquitination mediated by the linear ubiquitin chain assembly complex (LUBAC), is emerging as a crucial mechanism of overactivated NF-κB signaling. Ovarian tumor family deubiquitinase OTULIN is the only linear linkage-specific deubiquitinase; however, the molecular mechanisms of how it counteracts LUBAC-mediated NF-κB activation have been largely unknown. Here, we identify Lys64/66 of OTULIN for linear ubiquitination facilitated in a LUBAC-dependent manner as a necessary event required for OTULIN-LUBAC interaction under unstressed conditions, which becomes deubiquitinated by OTULIN itself in response to genotoxic stress. Furthermore, this self-deubiquitination of OTULIN occurs intermolecularly, mediated by OTULIN dimerization, resulting in the subsequent dissociation of OTULIN from the LUBAC complex and NF-κB overactivation. Oxidative stress induces OTULIN dimerization via cysteine-mediated covalent disulfide bonds. Our study reveals that the status of the physical interaction between OTULIN and LUBAC is a crucial determining factor for the genotoxic NF-κB signaling, as measured by cell survival and proliferation, while OTULIN loss of function resulting from its dimerization and deubiquitination leads to a dissociation of OTULIN from the LUBAC complex. Of note, similar molecular mechanisms apply to the inflammatory NF-κB signaling in response to tumor necrosis factor α. Hence, a fuller understanding of the detailed molecular mechanisms underlying the disruption of the OTULIN-LUBAC interaction will be instrumental for developing future therapeutic strategies against cancer chemoresistance and necroptotic processes pertinent to numerous human diseases.

Genotoxicity-Stimulated and CYLD-Driven Malignant Transformation

Oxidative stress, which can cause DNA damage, can both activate TNF-R1 directly in the absence of TNF stimulation and phosphorylate c-Abl, thus promoting its cytoplasmic translocation. Persistent cytoplasmic localization of c-Abl has been associated with cellular transformation. c-Abl phosphorylates OTULIN at tyrosine 56, thereby disrupting its relationship with LUBAC. OTULIN-released LUBAC interacts with SPATA2 and is recruited to the TNF-R1sc, facilitating SPATA2-CYLD interaction. All these interactions are required for the activation of IKKβ to stimulate NF-κB transcriptional activity following genotoxic stress. IKKβ also induces the critical phosphorylation of CYLD at serine 568 to increase its deubiquitinating (DUB) activity required for the termination of signaling cascades. Contrary to the widespread belief that CYLD is an absolute tumor suppressor, CYLD initiates and terminates NF-κB activity by alternately using its oncoprotein and tumor suppressor activities, respectively. If IKKβ fails to achieve the DUB activity-inducing phosphorylation at serine 568, CYLD would operate in a sustained mode of oncogenic activity. The resulting dysregulated NF-κB activation and other accompanying pathologies will disrupt cellular homeostasis in favor of transformation.

Mechanisms orchestrating the enzymatic activity and cellular functions of deubiquitinases

Deubiquitinases (DUBs) are required for the reverse reaction of ubiquitination and act as major regulators of ubiquitin signaling processes. Emerging evidence suggests that these enzymes are regulated at multiple levels in order to ensure proper and timely substrate targeting and to prevent the adverse consequences of promiscuous deubiquitination. The importance of DUB regulation is highlighted by disease-associated mutations that inhibit or activate DUBs, deregulating their ability to coordinate cellular processes. Here, we describe the diverse mechanisms governing protein stability, enzymatic activity, and function of DUBs. In particular, we outline how DUBs are regulated by their protein domains and interacting partners. Intramolecular interactions can promote protein stability of DUBs, influence their subcellular localization, and/or modulate their enzymatic activity. Remarkably, these intramolecular interactions can induce self-deubiquitination to counteract DUB ubiquitination by cognate E3 ubiquitin ligases. In addition to intramolecular interactions, DUBs can also oligomerize and interact with a wide variety of cellular proteins, thereby forming obligate or facultative complexes that regulate their enzymatic activity and function. The importance of signaling and post-translational modifications in the integrated control of DUB function will also be discussed. While several DUBs are described with respect to the multiple layers of their regulation, the tumor suppressor BAP1 will be outlined as a model enzyme whose localization, stability, enzymatic activity, and substrate recognition are highly orchestrated by interacting partners and post-translational modifications.

PRR16/Largen Induces Epithelial-Mesenchymal Transition through the Interaction with ABI2 Leading to the Activation of ABL1 Kinase

Advanced or metastatic breast cancer affects multiple organs and is a leading cause of cancer-related death. Cancer metastasis is associated with epithelial-mesenchymal metastasis (EMT). However, the specific signals that induce and regulate EMT in carcinoma cells remain unclear. PRR16/Largen is a cell size regulator that is independent of mTOR and Hippo signalling pathways. However, little is known about the role PRR16 plays in the EMT process. We found that the expression of PRR16 was increased in mesenchymal breast cancer cell lines. PRR16 overexpression induced EMT in MCF7 breast cancer cells and enhances migration and invasion. To determine how PRR16 induces EMT, the binding proteins for PRR16 were screened, revealing that PRR16 binds to Abl interactor 2 (ABI2). We then investigated whether ABI2 is involved in EMT. Gene silencing of ABI2 induces EMT, leading to enhanced migration and invasion. ABI2 is a gene that codes for a protein that interacts with ABL proto-oncogene 1 (ABL1) kinase. Therefore, we investigated whether the change in ABI2 expression affected the activation of ABL1 kinase. The knockdown of ABI2 and PRR16 overexpression increased the phosphorylation of Y412 in ABL1 kinase. Our results suggest that PRR16 may be involved in EMT by binding to ABI2 and interfering with its inhibition of ABL1 kinase. This indicates that ABL1 kinase inhibitors may be potential therapeutic agents for the treatment of PRR16-related breast cancer.

Roles of ubiquitination in the crosstalk between tumors and the tumor microenvironment (Review)

The interaction between a tumor and the tumor microenvironment (TME) plays a key role in tumorigenesis and tumor progression. Ubiquitination, a crucial post-translational modification for regulating protein degradation and turnover, plays a role in regulating the crosstalk between a tumor and the TME. Thus, identifying the roles of ubiquitination in the process may assist researchers to investigate the mechanisms underlying tumorigenesis and tumor progression. In the present review article, new insights into the substrates for ubiquitination that are involved in the regulation of hypoxic environments, angiogenesis, chronic inflammation-mediated tumor formation, and the function of cancer-associated fibroblasts and infiltrating immune cells (tumor-associated macrophages, T-cells, myeloid-derived suppressor cells, dendritic cells, and natural killer cells) are summarized. In addition, the potential targets of the ubiquitination proteasome system within the TME for cancer therapy and their therapeutic effects are reviewed and discussed.

Wnt Signaling in the Breast: From Development to Disease

The Wnt cascade is a primordial developmental signaling pathway that plays a myriad of essential functions throughout development and adult homeostasis in virtually all animal species. Aberrant Wnt activity is implicated in embryonic and tissue morphogenesis defects, and several diseases, most notably cancer. The role of Wnt signaling in mammary gland development and breast cancer initiation, maintenance, and progression is far from being completely understood and is rather shrouded in controversy. In this review, we dissect the fundamental role of Wnt signaling in mammary gland development and adult homeostasis and explore how defects in its tightly regulated and intricated molecular network are interlinked with cancer, with a focus on the breast.

Wnt/beta-catenin signaling confers ferroptosis resistance by targeting GPX4 in gastric cancer

The development of chemotherapy resistance is the most vital obstacle to clinical efficacy in gastric cancer (GC). The dysregulation of the Wnt/beta-catenin signaling pathway is critically associated with GC development and chemotherapy resistance. Ferroptosis is a form of regulated cell death, induced by an iron-dependent accumulation of lipid peroxides during chemotherapy. However, whether the Wnt/beta-catenin signaling directly controls resistance to cell death, remains unclear. Here, we show that the activation of the Wnt/beta-catenin signaling attenuates cellular lipid ROS production and subsequently inhibits ferroptosis in GC cells. The beta-catenin/TCF4 transcription complex directly binds to the promoter region of GPX4 and induces its expression, resulting in the suppression of ferroptotic cell death. Concordantly, TCF4 deficiency promotes cisplatin-induced ferroptosis in vitro and in vivo. Thus, we demonstrate that the aberrant activation of the Wnt/beta-catenin signaling confers ferroptosis resistance and suggests a potential therapeutic strategy to enhance chemo-sensitivity for advanced GC patients.

Exosomal OTULIN from M2 macrophages promotes the recovery of spinal cord injuries via stimulating Wnt/β-catenin pathway-mediated vascular regeneration

Vascularization following spinal cord injury (SCI) provides trophic support for rebuilding up and maintaining the homeostasis of neuronal networks, and the promotion of angiogenesis is beneficial for functional recovery after SCI. M2 macrophages have been reported to exhibit powerful pro-angiogenic functions during tissue repair. Exosomes are important paracrine mediators of their parent cells and play critical roles in tissue regeneration. However, the role of M2 macrophage-derived exosomes (M2-Exos) in SCI is still largely unknown. In the present study, we determined that M2-Exos could augment the angiogenic activities of spinal cord microvascular endothelial cells (SCMECs) in vitro. Hydrogel-mediated sustained release of M2-Exos significantly promoted vascular regeneration and functional recovery in mice after SCI. Furthermore, proteomics analysis showed that ubiquitin thioesterase otulin (OTULIN) protein was highly enriched in M2-Exos. Functional assays demonstrated that OTULIN protein was required for the M2-Exos-induced pro-angiogenic effects in SCMECs, as well as positive effects on vascular regeneration, cell proliferation, and functional recovery in the mouse model of SCI. Mechanically, OTULIN from M2-Exos could activate the Wnt/β-catenin signaling by increasing the protein level of β-catenin via inhibiting its ubiquitination and trigger the expression of angiogenesis-related genes that are reported to be the downstream targets of Wnt/β-catenin signaling. Inhibition of the Wnt/β-catenin signaling by ICG001 markedly attenuated the pro-angiogenic activities of M2-Exos in vitro/vivo. Our findings indicate that M2-Exos positively modulate vascular regeneration and neurological functional recovery after SCI by activating Wnt/β-catenin signaling through the transfer of OTULIN protein. STATEMENT OF SIGNIFICANCE: M2 macrophages have been identified to promote vascular regeneration, cell proliferation and tissue growth after spinal cord injury (SCI), which is beneficial to the functional recovery. Exosomes are essential paracrine mediators involved in cell-to-cell communication and play important roles in tissue regeneration. In the present study, we revealed that M2 macrophages-derived exosomes (M2-Exos) could promote functional recovery post SCI by targeting angiogenesis. We demonstrated for the first time that OTULIN protein from M2-Exos mediated the angiogenic effects through activating Wnt/β-catenin signaling and triggering the expression of angiogenic-related genes in spinal cord microvascular endothelial cells (SCMECs). The hydrogel-M2-Exos sustained released system provides potential therapeutic clues of local cell-free interventions for the treatment of SCI.

Linear Ubiquitination Mediates EGFR-Induced NF-κB Pathway and Tumor Development

Epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase that instigates several signaling cascades, including the NF-κB signaling pathway, to induce cell differentiation and proliferation. Overexpression and mutations of EGFR are found in up to 30% of solid tumors and correlate with a poor prognosis. Although it is known that EGFR-mediated NF-κB activation is involved in tumor development, the signaling axis is not well elucidated. Here, we found that plakophilin 2 (PKP2) and the linear ubiquitin chain assembly complex (LUBAC) were required for EGFR-mediated NF-κB activation. Upon EGF stimulation, EGFR recruited PKP2 to the plasma membrane, and PKP2 bridged HOIP, the catalytic E3 ubiquitin ligase in the LUBAC, to the EGFR complex. The recruitment activated the LUBAC complex and the linear ubiquitination of NEMO, leading to IκB phosphorylation and subsequent NF-κB activation. Furthermore, EGF-induced linear ubiquitination was critical for tumor cell proliferation and tumor development. Knockout of HOIP impaired EGF-induced NF-κB activity and reduced cell proliferation. HOIP knockout also abrogated the growth of A431 epidermal xenograft tumors in nude mice by more than 70%. More importantly, the HOIP inhibitor, HOIPIN-8, inhibited EGFR-mediated NF-κB activation and cell proliferation of A431, MCF-7, and MDA-MB-231 cancer cells. Overall, our study reveals a novel linear ubiquitination signaling axis of EGFR and that perturbation of HOIP E3 ubiquitin ligase activity is potential targeted cancer therapy.

Roles and Mechanisms of Deubiquitinases (DUBs) in Breast Cancer Progression and Targeted Drug Discovery

Deubiquitinase (DUB) is an essential component in the ubiquitin—proteasome system (UPS) by removing ubiquitin chains from substrates, thus modulating the expression, activity, and localization of many proteins that contribute to tumor development and progression. DUBs have emerged as promising prognostic indicators and drug targets. DUBs have shown significant roles in regulating breast cancer growth, metastasis, resistance to current therapies, and several canonical oncogenic signaling pathways. In addition, specific DUB inhibitors have been identified and are expected to benefit breast cancer patients in the future. Here, we review current knowledge about the effects and molecular mechanisms of DUBs in breast cancer, providing novel insight into treatments of breast cancer-targeting DUBs.

ABL1 Is a Prognostic Marker and Associated with Immune Infiltration in Hepatocellular Carcinoma

Background

The role of ABL1 in hepatocellular carcinoma (HCC) is still unclear. Therefore, this study aims to explore the potential role of ABL1 in the progression of HCC using bioinformatics methods.

Methods

We analyzed the expression, prognostic potential, and immune cell effect of ABL1 in HCC by using a variety of datasets.

Results

ABL1 is highly expressed in HCC and associated with unfavorable overall survival (OS) and disease-free survival (DFS). Functional network analysis revealed that ABL1 plays an important role in mitochondrial activity, ATP metabolism, protein translation and metabolism, various neurological diseases, nonalcoholic fatty liver disease, and notch signaling pathway. In addition, we found that ABL1 expression was closely correlated with B cells, CD8 + T cells, CD4 + T cells, macrophages, neutrophils, and dendritic cells. Furthermore, ABL1 expression was positively associated with the expression levels of immune checkpoint genes, such as PD-1L, TIM3, TIGIT, and CTLA4.

Conclusion

ABL1 is associated with immune infiltration and prognosis of HCC.

Fine-tuning ALK1 linear polyubiquitination to control angiogenesis

Editing linear polyubiquitination of protein substrates by LUBAC and OTULIN is known to play a critical role in immune responses. A recent study by Fu et al. reveals how reversible linear polyubiquitination of the activin receptor-like kinase (ALK1) controls developmental angiogenesis and how its dysfunction leads to vascular malformations in humans.

Post-Translational Modifications of Deubiquitinating Enzymes: Expanding the Ubiquitin Code

Post-translational modifications such as ubiquitination play important regulatory roles in several biological processes in eukaryotes. This process could be reversed by deubiquitinating enzymes (DUBs), which remove conjugated ubiquitin molecules from target substrates. Owing to their role as essential enzymes in regulating all ubiquitin-related processes, the abundance, localization, and catalytic activity of DUBs are tightly regulated. Dysregulation of DUBs can cause dramatic physiological consequences and a variety of disorders such as cancer, and neurodegenerative and inflammatory diseases. Multiple factors, such as transcription and translation of associated genes, and the presence of accessory domains, binding proteins, and inhibitors have been implicated in several aspects of DUB regulation. Beyond this level of regulation, emerging studies show that the function of DUBs can be regulated by a variety of post-translational modifications, which significantly affect the abundance, localization, and catalytic activity of DUBs. The most extensively studied post-translational modification of DUBs is phosphorylation. Besides phosphorylation, ubiquitination, SUMOylation, acetylation, oxidation, and hydroxylation are also reported in DUBs. In this review, we summarize the current knowledge on the regulatory effects of post-translational modifications of DUBs.

OTULIN in NF-κB signaling, cell death, and disease

Tight control of inflammatory signaling pathways is an absolute requirement to avoid chronic inflammation and disease. One of the proteins responsible for such control is OTU deubiquitinase with linear linkage specificity (OTULIN), the only mammalian deubiquitinating enzyme (DUB) exclusively hydrolyzing linear ubiquitin chains from proteins modified by the linear ubiquitin chain assembly complex (LUBAC) described thus far. Recent findings show that loss-of-function mutations in OTULIN underlie a severe early-onset human autoinflammatory disease and severe pathology in experimental mouse models. Here, we review the molecular and cellular mechanisms by which OTULIN controls inflammation and discuss the involvement of OTULIN in inflammatory disease development. We also highlight several newly identified roles for OTULIN, including a ubiquitin-independent function.

Met1-linked ubiquitin signalling in health and disease: inflammation, immunity, cancer, and beyond

Post-translational modification of proteins with ubiquitin (ubiquitination) provides a rapid and versatile mechanism for regulating cellular signalling systems. Met1-linked (or 'linear') ubiquitin chains have emerged as a key regulatory signal that controls cell death, immune signalling, and other vital cellular functions. The molecular machinery that assembles, senses, and disassembles Met1-linked ubiquitin chains is highly specific. In recent years, the thorough biochemical and genetic characterisation of the enzymes and proteins of the Met1-linked ubiquitin signalling machinery has paved the way for substantial advances in our understanding of how Met1-linked ubiquitin chains control cell signalling and biology. Here, we review current knowledge and recent insights into the role of Met1-linked ubiquitin chains in cell signalling with an emphasis on their role in disease biology. Met1-linked ubiquitin has potent regulatory functions in immune signalling, NF-κB transcription factor activation, and cell death. Importantly, mounting evidence shows that dysregulation of Met1-linked ubiquitin signalling is associated with multiple human diseases, including immune disorders, cancer, and neurodegeneration. We discuss the latest evidence on the cellular function of Met1-linked ubiquitin in the context of its associated diseases and highlight new emerging roles of Met1-linked ubiquitin chains in cell signalling, including regulation of protein quality control and metabolism.