Ubiquitin-specific protease 11 serves as a marker of poor prognosis and promotes metastasis in hepatocellular carcinoma

USP4 promotes proliferation and metastasis in human lung adenocarcinoma

Research the expression of USP4 in lung adenocarcinoma and its correlation with clinicopathological features and prognosis analysis, to explore the invasion and metastasis mechanism of USP4 in lung adenocarcinoma, and to clarify the mechanism of USP4's involvement in the occurrence and development of lung adenocarcinoma. The expressions of USP4, VEGF, MMP2 and Ki67 in lung adenocarcinoma and adjacent tissues of 139 patients with lung adenocarcinoma were detected by immunohistochemical method, and the correlation between expression and clinicopathological features and survival curve were analyzed by statistical method. The expression of USP4 was interfered by LIP-2000 cell transfection technology, and the expression of USP4 and its related factors in protein level was detected by Western Blot, and their correlation was analyzed. After silencing USP4 expression, the effects of USP4 on proliferation, invasion and migration of lung adenocarcinoma cells were detected by cell scratches assay, MTT assay, Transwell assay and tumorigenesis assay in nude mice. The expression of USP4 in lung adenocarcinoma tissues was higher than that in normal adjacent tissues, and the high expression of USP4 was significantly correlated with the differentiation degree of lung adenocarcinoma, clinical stage and pathological grade lymph node metastasis. After silencing USP4 expression, the expression of cyclin apoptosis protein invasion related proteins and phosphorylation factors were affected, and then cell migration and the proliferation ability decreased, the number of invasion and metastasis decreased, and the tumor volume decreased in nude mice. USP4 may play a certain role in the invasion and metastasis of lung adenocarcinoma by regulating the expression of tumor-related factors and affecting the prognosis of patients with lung adenocarcinoma. USP4 can be used as a potential therapeutic target for clinical diagnosis of lung adenocarcinoma and provide a new opportunity for clinical research on lung adenocarcinoma.

The activation of the Notch signaling pathway by UBE2C promotes the proliferation and metastasis of hepatocellular carcinoma

UBE2C, a ubiquitin-conjugating enzyme, functions as an oncogene in different types of human cancers. Nonetheless, the exact influence of UBE2C on the development of HCC via regulation of ubiquitination remains uncertain. Here, we found that UBE2C displayed elevated levels of expression in HCC and was associated with an unfavorable prognosis, as evidenced by the analysis of the TCGA database and the examination of clinical specimens. The role of UBE2C in HCC revealed its ability to promote the growth and metastasis of HCC. Mechanistically, UBE2C activated Notch signaling, as evidenced by the upregulation of N1ICD and Hes1, crucial components of the Notch pathway, and activation of the RBP-JK luciferase reporter by UBE2C. Finally, rescue experiments demonstrated that the oncogenic role of UBE2C was eliminated through treatment with the Notch inhibitor DAPT, while overexpression of N1ICD alleviated the anticarcinogenic impact of knockdown of UBE2C. Altogether, the results of our study indicate that UBE2C plays a role in the activation of Notch signaling and could potentially serve as a viable target for therapeutic interventions in HCC.

The deubiquitinating enzyme USP11 regulates breast cancer progression by stabilizing PGAM5

Breast cancer is common worldwide. Phosphoglycerate mutase 5 (PGAM5) belongs to the phosphoglycerate mutase family and plays an important role in many cancers. However, research on its role in breast cancer remains unclear. The present investigation highlights the significant expression of PGAM5 in breast cancer and its essential role in cell proliferation, invasion, apoptosis and the regulation of ferroptosis in breast cancer cells. Overexpression or knockdown of ubiquitin-specific protease 11 (USP11) promotes or inhibits the growth and metastasis of breast cancer cells, respectively, in vitro and in vivo. Mechanistically, USP11 stabilizes PGAM5 via de-ubiquitination, protecting it from proteasome-mediated degradation. In addition, the USP11/PGAM5 complex promotes breast cancer progression by activating iron death-related proteins, indicating that the synergy between USP11 and PGAM5 may serve as a predictor of disease outcome and provide a new treatment strategy for breast cancer.

Integrative and comprehensive pan-cancer analysis of ubiquitin specific peptidase 11 (USP11) as a prognostic and immunological biomarker

The significance of USP11 as a critical regulator in cancer has garnered substantial attention, primarily due to its catalytic activity as a deubiquitinating enzyme. Nonetheless, a thorough evaluation of USP11 across various cancer types in pan-cancer studies remains absent. Our analysis integrates data from a variety of sources, including five immunotherapy cohorts, thirty-three cohorts from The Cancer Genome Atlas (TCGA), and sixteen cohorts from the Gene Expression Omnibus (GEO), two of which involve single-cell transcriptomic data. Our findings indicate that aberrant USP11 expression is predictive of survival outcomes across various cancer types. The highest frequency of genomic alterations was observed in uterine corpus endometrial carcinoma (UCEC), with single-cell transcriptome analysis revealing significantly higher USP11 expression in plasmacytoid dendritic cells and mast cells. Notably, USP11 expression was associated with the infiltration levels of CD8+ T cells and natural killer (NK) activated cells. Additionally, in the skin cutaneous melanoma (SKCM) phs000452 cohort, patients with higher USP11 mRNA levels during immunotherapy experienced a significantly shorter median progression-free survival. USP11 emerges as a promising molecular biomarker with significant potential for predicting patient prognosis and immunoreactivity across various cancer types.

USP11 promotes glycolysis by regulating HIF-1α stability in hepatocellular carcinoma

Understanding the mechanisms underlying metastasis in hepatocellular carcinoma (HCC) is crucial for developing new therapies against this fatal disease. Deubiquitinase ubiquitin-specific protease 11 (USP11) belongs to the deubiquitinating family and has previously been reported to play a critical role in cancer pathogenesis. Although it has been established that USP11 can facilitate the metastasis and proliferation ability of HCC, the underlying regulatory mechanisms are poorly understood. The primary objective of this research was to reveal hitherto undocumented functions of USP11 during HCC progression, especially those related to metabolism. Under hypoxic conditions, USP11 was found to significantly impact the glycolysis of HCC cells, as demonstrated through various techniques, including RNA-Seq, migration and colony formation assays, EdU and co-immunoprecipitation. Interestingly, we found that USP11 interacted with the HIF-1α complex and maintained HIF-1α protein stability by removing ubiquitin. Moreover, USP11/HIF-1α could promote glycolysis through the PDK1 and LDHA pathways. In general, our results demonstrate that USP11 promotes HCC proliferation and metastasis through HIF-1α/LDHA-induced glycolysis, providing new insights and the experimental basis for developing new treatments for this patient population.

USP11 potentiates HGF/AKT signaling and drives metastasis in hepatocellular carcinoma

USP11 is a member of the ubiquitin-specific protease family and plays a crucial role in tumor progression in various cancers. However, the precise mechanism by which USP11 promotes EMT and metastasis in hepatocellular carcinoma (HCC) is not fully understood. In this study, we demonstrated that the USP11 expression was dramatically upregulated in HCC tissues and cell lines. Increased USP11 expression was closely associated with tumor number, vascular invasion, and poor prognosis. Functional experiments demonstrated that USP11 markedly promoted metastasis and EMT in HCC via induction of the transcription factor Snail. Mechanistically, USP11 interacted with and deubiquitinated eEF1A1 on Lys439, thereby inhibiting its ubiquitin-mediated degradation. Subsequently, the elevated expression of eEF1A1 resulted in its binding to SP1, which in turn drove the binding of SP1 to its target HGF gene promoter to increase its transcription. This led to an enhanced expression of HGF and the activation of the downstream PI3K/AKT signaling pathway. We demonstrated that USP11 promotes EMT and metastasis in HCC via eEF1A1/SP1/HGF dependent-EMT. Our findings suggest that the USP11/ eEF1A1/SP1/HGF axis contributes to metastasis in HCC, and therefore, could be considered as a potential therapeutic target for the treatment of HCC.

Deubiquitylating Enzymes in Cancer and Immunity

Deubiquitylating enzymes (DUBs) maintain relative homeostasis of the cellular ubiquitome by removing the post-translational modification ubiquitin moiety from substrates. Numerous DUBs have been demonstrated specificity for cleaving a certain type of ubiquitin linkage or positions within ubiquitin chains. Moreover, several DUBs perform functions through specific protein-protein interactions in a catalytically independent manner, which further expands the versatility and complexity of DUBs' functions. Dysregulation of DUBs disrupts the dynamic equilibrium of ubiquitome and causes various diseases, especially cancer and immune disorders. This review summarizes the Janus-faced roles of DUBs in cancer including proteasomal degradation, DNA repair, apoptosis, and tumor metastasis, as well as in immunity involving innate immune receptor signaling and inflammatory and autoimmune disorders. The prospects and challenges for the clinical development of DUB inhibitors are further discussed. The review provides a comprehensive understanding of the multi-faced roles of DUBs in cancer and immunity.

USP11 plays a critical role in the onset and progression of acute graft-versus-host disease：Novel target for precision therapeutics

Acute graft-versus-host disease (aGvHD) is considered a result of "cytokine storm." Targeted therapeutic interventions on cytokines via ubiquitination regulatory pathways may provide a potential approach for aGvHD treatment. Ubiquitin-specific peptidase 11 (USP11) has been reported to play key roles in a variety of physiopathological processes by regulating the stability and function of several vital protein molecules. However, its role in aGvHD remains unclear. In this study, we identified USP11 was associated with aGvHD in patients. In the aGvHD mouse model, the colon and liver were more seriously affected in recipient mice who received USP11 wt bone marrow (BM) cells and eased after the donor was treated with a USP11 inhibitor or received USP11 ko BM cells. In mouse models, IL-6 was identified as a major effecter in accelerating aGvHD induced by USP11. In the cell model, IL-6 mRNA transcript was affected by USP11. In addition, USP11 also inhibited IL-6 degradation by affecting IL-6 ubiquitination. Furthermore, the positive correlation between USP11 and IL-6 was confirmed in the GvHD patients' samples. Collectively, all results indicated that USP11 played a critical role in the onset and progression of aGvHD. USP11 might be a potential target for aGvHD treatment.

Deubiquitinating enzyme USP11 promotes renal tubular cell senescence and fibrosis via inhibiting the ubiquitin degradation of TGF-β receptor II

Transforming growth factor-β1 (TGF-β1) is regarded as a key factor in promoting renal fibrosis during chronic kidney disease (CKD). Signaling transduction of TGF-β1 starts with binding to TGF-β type II receptor (Tgfbr2), a constitutively activated kinase that phosphorylates TGF-β type I receptor (Tgfbr1), and then activates downstream Smad2/3 or noncanonical pathways. Previous studies show that cellular senescence is associated with the progression of CKD, and accelerated tubular cell senescence is implicated in promoting renal fibrosis. In the present study we investigated the renal parenchymal cell senescence in fibrosis from the sight of posttranslational regulation and focused on Tgfbr2, the important gatekeeper for TGF-β1 downstream signaling. In mice with unilateral ureteral obstruction (UUO) and folic acid (FA)-induced fibrotic kidneys, we found that Tgfbr2 was markedly elevated without obvious change in its mRNA levels. As an important member of deubiquitinating enzymes, ubiquitin-specific protease 11 (Usp11) was also significantly increased in fibrotic kidneys, and co-distributed with Tgfbr2 in tubular epithelial cells. Pretreatment with Usp11 inhibitor mitoxantrone (MTX, 30 mg · kg-1 · d-1, i.p.) twice a week, for 2 weeks significantly attenuated the elevation of Tgfbr2, activation in downstream senescence-related signaling pathway, as well as renal senescence and fibrosis. In cultured mouse tubular epithelial cells (MTECs), treatment with angiotensin II (Ang-II, 10-7, 10-6 M) dose-dependently elevated both Tgfbr2 and Usp11 levels. Inhibition or knockdown on Usp11 attenuated Ang-II-induced elevation in Tgfbr2 level, and attenuated the activation of downstream senescent-related signaling pathway and as well as cell senescence. We conducted Co-IP experiments, which revealed that Usp11 was able to interact with Tgfbr2, and inhibition of Usp11 increased the ubiquitination of Tgfbr2. Taken together, these results demonstrate that the elevation of Usp11 under pathological condition is implicated in promoting renal fibrosis. Usp11 promotes the development of renal fibrosis by deubiquitinating Tgfbr2, reducing Tgfbr2 ubiquitination degradation, and then facilitating the activation of downstream senescent signaling pathway.

Ubiquitin-specific protease 11 promotes partial epithelial-to-mesenchymal transition by deubiquitinating the epidermal growth factor receptor during kidney fibrosis

The aberrant expression of ubiquitin-specific protease 11 (USP11) is believed to be related to tumor progression. However, few studies have reported the biological function and clinical importance of USP11 in kidney fibrosis. Here, we demonstrated USP11 was highly upregulated in the kidneys from patients with chronic kidney disease and correlated positively with fibrotic lesion but negatively with kidney function. Conditional USP11 deletion or pharmacologic inhibition with Mitoxantrone attenuated pathological lesions and improved kidney function in both hyperuricemic nephropathy (HN)- and folic acid (FA)-induced mouse models of kidney fibrosis. Mechanistically, by RNA sequencing, USP11 was found to be involved in nuclear gene transcription of the epidermal growth factor receptor (EGFR). USP11 co-immunoprecipitated and co-stained with extra-nuclear EGFR and deubiquitinated and protected EGFR from proteasome-dependent degradation. Genetic or pharmacological depletion of USP11 facilitated EGFR degradation and abated augmentation of TGF-β1 and downstream signaling. This consequently alleviated the partial epithelial-mesenchymal transition, G2/M arrest and aberrant secretome of profibrogenic and proinflammatory factors in uric acid-stimulated tubular epithelial cells. Moreover, USP11 deletion had anti-fibrotic and anti-inflammatory kidney effects in the murine HN and FA models. Thus, our study provides evidence supporting USP11 as a promising target for minimizing kidney fibrosis and that inhibition of USP11 has potential to be an effective strategy for patients with chronic kidney disease.

Advances in prognostic and therapeutic targets for hepatocellular carcinoma and intrahepatic cholangiocarcinoma: The hippo signaling pathway

Primary liver cancer is the sixth most frequently diagnosed cancer worldwide and the third leading cause of cancer-related death. The majority of the primary liver cancer cases are hepatocellular carcinoma and intrahepatic cholangiocarcinoma. Worldwide, there is an increasing incidence of primary liver cancer cases due to multiple risk factors ranging from parasites and viruses to metabolic diseases and lifestyles. Often, patients are diagnosed at advanced stages, depriving them of surgical curability benefits. Moreover, the efficacy of the available chemotherapeutics is limited in advanced stages. Furthermore, tumor metastases and recurrence make primary liver cancer management exceptionally challenging. Thus, exploring the molecular mechanisms for the development and progression of primary liver cancer is critical in improving diagnostic, treatment, prognostication, and surveillance modalities. These mechanisms facilitate the discovery of specific targets that are critical for novel and more efficient treatments. Consequently, the Hippo signaling pathway executing a pivotal role in organogenesis, hemostasis, and regeneration of tissues, regulates liver cells proliferation, and apoptosis. Cell polarity or adhesion molecules and cellular metabolic status are some of the biological activators of the pathway. Thus, understanding the mechanisms exhibited by the Hippo pathway is critical to the development of novel targeted therapies. This study reviews the advances in identifying therapeutic targets and prognostic markers of the Hippo pathway for primary liver cancer in the past six years.

Ubiquitin specific peptidase 11 as a novel therapeutic target for cancer management

Ubiquitination is a critical biological process in post-translational modification of proteins and involves multiple signaling pathways in protein metabolism, apoptosis, DNA damage, cell-cycle progression, and cancer development. Deubiquitinase, a specific enzyme that regulates the ubiquitination process, is also thought to be closely associated with the development and progression of various cancers. In this article, we systematically review the emerging role of the deubiquitinase ubiquitin-specific peptidase 11 (USP11) in many cancer-related pathways. The results show that USP11 promotes or inhibits the progression and chemoresistance of different cancers, including colorectal, breast, ovarian, and hepatocellular carcinomas, via deubiquitinating several critical proteins of cancer-related pathways. We initially summarize the role of USP11 in different cancers and further discuss the possibility of USP11 as a therapeutic strategy.

The Dual Role of USP11 in Cancer

Ubiquitination is one of the most crucial ways of protein degradation and plays an indispensable role in various living activities of cells. The deubiquitinating enzyme (DUB) is the main practitioner of the reversal of ubiquitination. Up till the present moment, nearly 100 DUBs from six families have been confirmed. USP11 is a member of the largest subfamily of cysteine protease DUBs, involving in the regulation of cell cycle, DNA repair, regulating signaling pathways, tumor development, and other important biological behaviors. This review briefly describes the structure and function of USP11 and comprehensively describes its dual role in tumorigenesis and development, as well as its targeted therapy.

USP8 regulates liver cancer progression via the inhibition of TRAF6-mediated signal for NF-κB activation and autophagy induction by TLR4

Herein, we aimed to elucidate the molecular and cellular mechanism in which ubiquitin-specific protease 8 (USP8) is implicated in liver cancer progression via TRAF6-mediated signal. USP8 induces the deubiquitination of TRAF6, TAB2, TAK1, p62, and BECN1, which are pivotal roles for NF-κB activation and autophagy induction. Notably, the LIHC patient with low USP8 mRNA expression showed markedly shorter survival time, whereas there was no significant difference in the other 18-human cancers. Importantly, the TCGA data analysis on LIHC and transcriptome analysis on the USP8 knockout (USP8KO) SK-HEP-1 cells revealed a significant correlation between USP8 and TRAF6, TAB2, TAK1, p62, and BECN1, and enhanced NF-κB-dependent and autophagy-related cancer progression/metastasis-related genes in response to LPS stimulation. Furthermore, USP8KO SK-HEP-1 cells showed an increase in cancer migration and invasion by TLR4 stimulation, and a marked increase of tumorigenicity and metastasis in xenografted NSG mice. The results demonstrate that USP8 is negatively implicated in the LIHC progression through the regulation of TRAF6-mediated signal for the activation of NF-κB activation and autophagy induction. Our findings provide useful insight into the LIHC pathogenesis of cancer progression.

Novel oncogenes and tumor suppressor genes in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a very deadly disease. HCC initiation and progression involve multiple genetic events, including the activation of proto-oncogenes and disruption of the function of specific tumor suppressor genes. Activation of oncogenes stimulates cell growth and survival, while loss-of-function mutations of tumor suppressor genes result in unrestrained cell growth. In this review, we summarize the new findings that identified novel proto-oncogenes and tumor suppressors in HCC over the past five years. These findings may inspire the development of novel therapeutic strategies to improve the outcome of HCC patients.

The E2F1/USP11 positive feedback loop promotes hepatocellular carcinoma metastasis and inhibits autophagy by activating ERK/mTOR pathway

Deubiquitinase ubiquitin-specific protease 11 (USP11), a member of the deubiquitinating family, plays an important but still controversial role in cancer development. Namely, USP11 has been shown to promote the proliferation and metastasis of hepatocellular carcinoma (HCC), but the underlying molecular basis is poorly understood. This study aimed to unravel novel functions of USP11 in HCC, especially those related to autophagy. Here, EdU, migration and colony formation assays, and mouse models showed that USP11 played a crucial role in HCC cell proliferation and metastasis in vitro and in vivo. Results from co-immunoprecipitation and ubiquitination assays demonstrated that USP11 interacted with E2F1 and maintained E2F1 protein stability by removing its ubiquitin. Notably, E2F1 regulated USP11 expression at the transcriptional level. Thus, the E2F1/USP11 formed a positive feedback loop to promote the proliferation and migration of HCC cells. Moreover, E2F1/USP11 inhibited autophagy by regulating ERK/mTOR pathway. In addition, the combination treatment inhibition of USP11 and autophagy enhanced the apoptosis of HCC cells and inhibited the tumor growth in mice more effective than either treatment alone. Taken together, these results indicate that the E2F1/USP11 signal axis promotes HCC proliferation and metastasis and inhibits autophagy, which provides an experimental basis for the treatment of HCC.

USP11 degrades KLF4 via its deubiquitinase activity in liver diseases

Krüppel‐like factor 4 (KLF4) is a zinc‐finger containing DNA‐binding transcription factor involved in tumorigenesis and acts as a tumour suppressor or an oncogene depending on the tissue. In hepatocellular carcinoma (HCC), KLF4 has been considered as a tumour suppressor, although the mechanism underlying its action remains largely unknown. In this study, we identified the ubiquitin‐specific peptidase USP11 as a KLF4‐interacting deubiquitinating enzyme using a proteomic approach. USP11 destabilizes KLF4 through the removal of K63‐dependent polyubiquitination, thereby inhibiting KLF4 expression. We also provide mechanistic insights into KLF4 degradation and show that USP11 depletion inhibits growth and chemoresistance of HCC cells by enhancing KLF4 stability. Importantly, lipid content was reduced and genes involved in fatty acid metabolism were down‐regulated in an in vitro steatosis conditions upon USP11 knockout. Finally, elevated USP11 and reduced KLF4 levels were detected both in a hepatic steatosis in vitro model and in public clinical data of non‐alcoholic fatty liver disease and HCC patients. Collectively, these findings suggest that USP11, as KLF4‐binding partner, is an important mediator of hepatic tumorigenesis that functions via degradation of KLF4 and is a potential treatment target for liver diseases.

Identification and Validation of Ubiquitin-Specific Proteases as a Novel Prognostic Signature for Hepatocellular Carcinoma

Purpose

Ubiquitin-specific proteases (USPs), as a sub-family of deubiquitinating enzymes (DUBs), are responsible for the elimination of ubiquitin-triggered modification. USPs are recently correlated with various malignancies. However, the expression features and clinical significance of USPs have not been systematically investigated in hepatocellular carcinoma (HCC).

Methods

Genomic alterations and expression profiles of USPs were investigated in CbioPortal and The Cancer Genome Atlas (TCGA) Liver hepatocellular carcinoma (LIHC) dataset. Cox regression and least absolute shrinkage and selection operator (LASSO) analyses were conducted to establish a risk signature for HCC prognosis in TCGA LIHC cohort. Subsequently, Kaplan-Meier analysis, receiver operating characteristic (ROC) curves and univariate/multivariate analyses were performed to evaluate the prognostic significance of the risk signature in TCGA LIHC and international cancer genome consortium (ICGC) cohorts. Furthermore, we explored the alterations of the signature genes during hepatocarcinogenesis and HCC progression in GSE89377. In addition, the expression feature of USP39 was further explored in HCC tissues by performing western blotting and immunohistochemistry.

Results

Genomic alterations and overexpression of USPs were observed in HCC tissues. The consensus analysis indicated that the USPs-overexpressed sub-Cluster was correlated with aggressive characteristics and poor prognosis. Cox regression with LASSO algorithm identified a risk signature formed by eight USPs for HCC prognosis. High-risk group stratified by the signature score was correlated with advanced tumor stage and poor survival HCC patients in TCGA LIHC cohort. In addition, the 8-USPs based signature could also robustly predict overall survival of HCC patients in ICGC(LIRI-JP) cohort. Furthermore, gene sets enrichment analysis (GSEA) showed that the high-risk score was associated with tumor-related pathways. According to the observation in GSE89377, USP39 expression was dynamically increased with hepatocarcinogenesis and HCC progression. The overexpression of USP39 was further determined in a local HCC cohort and correlated with poor prognosis. The co-concurrence analysis suggested that USP39 might promote HCC by regulating cell-cycle- and proliferation- related genes.

Conclusion

The current study provided a USPs-based signature, highlighting its robust prognostic significance and targeted value for HCC treatment.

High expression of FOXM1 critical for sustaining cell proliferation in mitochondrial DNA-less liver cancer cells

The copy number of mitochondrial DNA (mtDNA) is decreased in most cancer types, including hepatocellular carcinoma (HCC), compared to normal counterparts. However, a decrease in mtDNA usually leads to defects in cell proliferation, which contradicts the robustness of cancer cell proliferation. In this study, we found that four out of seven HCC cell lines were of the mtDNA-less type. Interestingly, FOXM1, a member of the FOX transcription factor family, was highly expressed in a subset of them with proliferative potential maintained. B-MYB, a partner of FOXM1, was also expressed in the same cell lines. RNAi-mediated experiments demonstrated that when FOXM1/B-MYB was silenced in the cell lines, cell cycle-related genes were downregulated, while p21^Cip1 was induced with senescence-associated β-galactosidase, resulting in G₁/S cell cycle arrest. These results suggest that high expression of FOXM1/B-MYB is critical for sustaining cell proliferation in mtDNA-less cells. In addition, we found that high expression of FOXM1 was mediated by the deubiquitinating enzyme, OTUB1, in one cell line. Thus, interference with FOXM1/B-MYB expression, such as through OTUB1 inhibition, may induce a dormant state of senescence-like proliferation arrest in mtDNA-less cancer cells. This finding may be utilized for the development of precision medicine for relevant cancers.

USP11 acts as a histone deubiquitinase functioning in chromatin reorganization during DNA repair

How chromatin dynamics is regulated to ensure efficient DNA repair remains to be understood. Here, we report that the ubiquitin-specific protease USP11 acts as a histone deubiquitinase to catalyze H2AK119 and H2BK120 deubiquitination. We showed that USP11 is physically associated with the chromatin remodeling NuRD complex and functionally involved in DNA repair process. We demonstrated that USP11-mediated histone deubiquitination and NuRD-associated histone deacetylation coordinate to allow timely termination of DNA repair and reorganization of the chromatin structure. As such, USP11 is involved in chromatin condensation, genomic stability, and cell survival. Together, these observations indicate that USP11 is a chromatin modifier critically involved in DNA damage response and the maintenance of genomic stability.

Long noncoding RNA lnc-DILC stabilizes PTEN and suppresses clear cell renal cell carcinoma progression

Background

Increasing evidence has indicated that long noncoding RNAs (lncRNAs) are crucial regulators affecting the progression of human cancers. Recently, lncRNA downregulated in liver cancer stem cells (lnc-DILC) was identified to function as a tumor suppressor inhibiting the tumorigenesis and metastasis in liver cancer and colorectal cancer. However, to date, little is known about the functional roles of lnc-DILC in modulating malignant phenotypes of clear cell renal cell carcinoma (ccRCC) cells.

Methods

lnc-DILC expression in human ccRCC tissues was detected by qRT-PCR. Overexpression and knockdown experiments were carried out to determine the effects of lnc-DILC on ccRCC cell proliferation, migration and invasion. To reveal the underlying mechanisms of lnc-DILC functions in ccRCC cells. RNA immunoprecipitation, RNA pull-down, in vivo ubiquitination, co-immunoprecipitation and western blot assays were performed.

Results

Here, we identified that lnc-DILC levels were dramatically downregulated in ccRCC tissues. Loss of lnc-DILC expression was correlated with larger tumor size, advanced tumor grade and lymph node metastasis, and also predicted worse prognosis in patients with ccRCC. Functionally, knockdown and overexpression experiments demonstrated that lnc-DILC inhibited cell proliferation, migration and invasion in ccRCC cells. Mechanistic investigation revealed that lnc-DILC bound to tumor suppressor PTEN and suppressed its degradation. lnc-DILC repressed the PTEN ubiquitination through blocking the interaction between PTEN and E3 ubiquitin ligase WWP2 and recruiting the deubiquitinase USP11 to PTEN. Moreover, we demonstrated that PTEN–AKT signaling was crucial for lnc-DILC-mediated suppressive effects.

Conclusions

In summary, our research revealed a novel mechanism by which lnc-DILC regulates PTEN stability via WWP2 and USP11, and shed light on potential therapeutic strategies by the restoration of lnc-DILC expression in patients with ccRCC.

Identification and Characterization of USP7 Targets in Cancer Cells

The ubiquitin specific protease, USP7, regulates multiple cellular pathways relevant for cancer through its ability to bind and sometimes stabilize specific target proteins through deubiquitylation. To gain a more complete profile of USP7 interactions in cancer cells, we performed affinity purification coupled to mass spectrometry to identify USP7 binding targets in gastric carcinoma cells. This confirmed reported associations of USP7 with USP11, PPM1G phosphatase and TRIP12 E3 ubiquitin ligase as well as identifying novel interactions with two DEAD/DEAH-box RNA helicases, DDX24 and DHX40. Using USP7 binding pocket mutants, we show that USP11, PPM1G, TRIP12 and DDX24 bind USP7 through its TRAF domain binding pocket, while DHX40 interacts with USP7 through a distinct binding pocket in the Ubl2 domain. P/A/ExxS motifs in USP11 and DDX24 that are critical for USP7 binding were also identified. Modulation of USP7 expression levels and inhibition of USP7 catalytic activity in multiple cells lines showed that USP7 consistently stabilizes DDX24, DHX40 and TRIP12 dependent on its catalytic activity, while USP11 and PPM1G levels were not consistently affected. Our study better defines the mechanisms of USP7 interaction with known targets and identifies DDX24 and DHX40 as new targets that are specifically bound and regulated by USP7.

Overexpression and clinical relevance of the RNA helicase DHX15 in hepatocellular carcinoma

DHX15 is an outstanding member of the DEAH-box RNA helicase family. A few studies suggest that DHX15 contributes to carcinogenesis in several tumor cell lines. However, whether DHX15 acts as an oncogene or tumor suppressor and its association with hepatocellular carcinoma (HCC) prognosis are still poorly understood. To address this question, we used immunohistochemistry to evaluate DHX15 expression patterns and their association with clinicopathological factors and the prognosis of patients with HCC. Our results showed that DHX15 expression was significantly higher in cancerous tissues than that in nontumor tissues (P < .0001). DHX15 expression in HCC patients was associated with differentiation status (P = .018), tumor number (P = .048), intrahepatic or extrahepatic metastasis (P = .001), serum α-fetoprotein (P = .006), hepatitis B virus level (P = .018), and recurrence (P < .001). In addition, the survival analysis revealed that the DHX15-high group had significantly decreased overall survival time (P = .004) and lower 1-year survival rates (P = .002) compared with the DHX15-low group. Furthermore, multivariate analysis identified DHX15 expression as an independent factor associated with poor prognosis in HCC (P = .036). In summary, these findings demonstrate, for the first time, that DHX15 is significantly upregulated in HCC and its high expression was correlated with poor prognosis, suggesting its pivotal role in the progression of HCC. The present results suggest that DHX15 may serve as a potential prognostic biomarker for HCC patients.