Control of CCND1 ubiquitylation by the catalytic SAGA subunit USP22 is essential for cell cycle progression through G1 in cancer cells. Proc Natl Acad Sci U S A. 2018;115:E9298-E9307. [PMID: 30224477 PMCID: PMC6176615 DOI: 10.1073/pnas.1807704115]

USP22 promotes IRF3 nuclear translocation and antiviral responses by deubiquitinating the importin protein KPNA2

USP22 is a cytoplasmic and nuclear deubiquitinating enzyme, and the functions of cytoplasmic USP22 are unclear. Here, we discovered that cytoplasmic USP22 promoted nuclear translocation of IRF3 by deubiquitianting and stabilizing KPNA2 after viral infection. Viral infection induced USP22-IRF3 association in the cytoplasm in a KPNA2-depedent manner, and knockdown or knockout of USP22 or KPNA2 impaired IRF3 nuclear translocation and expression of downstream genes after viral infection. Consistently, Cre-ER Usp22^fl/fl or Lyz2-Cre Usp22^fl/fl mice produced decreased levels of type I IFNs after viral infection and exhibited increased susceptibility to lethal viral infection compared with the respective control littermates. Mechanistically, USP22 deubiquitinated and stabilized KPNA2 after viral infection to facilitate efficient nuclear translocation of IRF3. Reconstitution of KPNA2 into USP22 knockout cells restored virus-triggered nuclear translocation of IRF3 and cellular antiviral responses. These findings define a previously unknown function of cytoplasmic USP22 and establish a mechanistic link between USP22 and IRF3 nuclear translocation that expands potential therapeutic strategies for infectious diseases.

Long non-coding RNA XIST promotes the progression of esophageal squamous cell carcinoma through sponging miR-129-5p and upregulating CCND1 expression

Long non-coding RNA (lncRNA) X inactive specific transcript (XIST) has been identified as an oncogenic lncRNA in a series of human cancers, including esophageal squamous cell carcinoma (ESCC). In this study, we aimed to further explore the underlying mechanism of XIST on ESCC progression. qRT-PCR assay was used to determine the levels of XIST and miR-129-5p. Western blot analysis was performed to assess cyclin D1 (CCND1) expression. Bioinformatic analysis was performed using starBase v2.0 software. Dual-luciferase reporter and RNA immunoprecipitation assays were employed to confirm the interaction between XIST and miR-129-5p or miR-129-5p and CCND1. Cell cycle progression and apoptosis were measured by flow cytometric analysis, and cell migration and invasion were detected by transwell assay. Mouse studies were used to observe the effect of XIST silencing on tumor growth in vivo. Our results indicated that XIST was upregulated and miR-129-5p was downregulated in ESCC. XIST silencing or miR-129-5p overexpression repressed cell cycle progression, proliferation, migration, invasion, and promoted the apoptosis in ESCC cells. Moreover, XIST directly interacted with miR-129-5p and repressed miR-129-5p expression. MiR-129-5p mediated the regulatory effect of XIST on ESCC cell progression in vitro, and XIST promoted CCND1 expression by sponging miR-129-5p. Additionally, XIST silencing inhibited tumor growth in vivo. Our findings suggested that XIST silencing repressed the progression of ESCC at least partly through regulating the miR-129-5p/CCND1 axis. Targeting XIST might be a potential therapeutic strategy for ESCC treatment.

The Role of ARL4C in Erlotinib Resistance: Activation of the Jak2/Stat 5/β-Catenin Signaling Pathway

Cancer patients who initially benefit from Erlotinib, a drug targeting EGFR path, eventually develop resistance to the drug. The underlying mechanism is largely unknown. This study investigated the role of ARL4C in Erlotinib resistance development of NSCLC. qRT-PCR and Western blotting were performed to analyze the expression of mRNA and protein of ARL4C in two NSCLC cell lines (HCC827 and PC-9). Several assays (MTS, colony formation, transwell migration, luciferase reporter, and chromatin-immunoprecipitation) were used to explore the role of ARL4C in biofunctional changes of Erlotinib-resistant cells and their associations with Jak2/Stat 5/β-catenin signaling. Results demonstrated that (1) long-term use of Erlotinib resulted in downregulation of ARL4C; (2) overexpression of ARL4C could regain the sensitivity to Erlotinib in the drug-resistant HCC827/ER cells, while downregulation of ARL4C increased HCC827, and PC-9 cells' resistance to the drug; (3) Erlotinib-induced downregulation of ARL4C resulted in phosphorylation of Jak2/Stat5 and upregulation of β-catenin and their related molecules Axin2, CD44, Ccnd1, Lgr-5, and MMP7, which promoted the malignant behaviors of Erlotinib-resistant cells; (4) chromatin immunoprecipitation and luciferase reporter assay revealed that Stat5 could bind to β-catenin promoter to upregulate molecules to maintain the malignant behaviors, which might count for how Erlotinib-resistant cell survived while EGFR path was blocked; (5) the expression of ARL4C was not associated with known EGFR gene mutations in both Erlotinib-resistant cells and NSCLC tissues. Our data suggest that Erlotinib resistance of NSCLCs is associated with downregulation of ARL4C via affecting Jak/Stat/β-catenin signaling. ARL4C could serve as a biomarker to predict the effectiveness of TKI targeting therapy and a potential therapeutic target for overcoming Erlotinib resistance in NSCLC.

The USP22 promotes the growth of cancer cells through the DYRK1A in pancreatic ductal adenocarcinoma

As a member of the ubiquitin-specific protease (USP) family, USP22 could remove ubiquitin moieties from its target proteins to control the function of the target proteins. Accumulating studies show that USP22 essentially participates in diverse types of cancer as an oncogene-like protein. However, the roles of USP22 in human pancreatic ductal adenocarcinoma (PDAC) and the underlying mechanism are unknown. Here we report that USP22 promotes the growth of PDAC cells by promoting the expression of dual-specificity tyrosine regulated kinase 1A (DYRK1A). Our results showed that the expression levels of USP22 were up-regulated in human PDAC tissues and cell lines (BxPC-3, AsPC-1, MIA-PaCa-2, PANC-1, and CAPAN-1). Lentivirus-mediated knockdown of USP22 repressed the rate of proliferation and capacity of colony formation of BxPC3 and CAPAN1 cancer cells and USP22 overexpression promoted the proliferation and capacity of the colony formation of BxPC3 and CAPAN1 cancer cells. The further mechanism study showed that USP22 elevated the expression of the mRNA and protein levels of DYRK1A in PDAC cancer cells. Inhibition of DYRK1A with EHT-5732 or lentivirus-mediated knockdown of DYRK1A blocked the function of USP22 overexpression in the regulation of the proliferation and colony formation of PDAC cells. Taken together, our findings demonstrated that USP22 overexpression in PDAC promoted the growth of the cancer cells partially through upregulating the expression of DYRK1A.

RNF220 promotes the proliferation of leukaemic cells and reduces the degradation of the Cyclin D1 protein through USP22

Ring finger proteins contain a characteristic ring finger motif and perform a wide range of biological functions in living organisms. These genes are abnormally expressed in many cancers. We found that the expression level of Ring finger protein 220 (RNF220) was negatively correlated with the disease-free survival (DFS) and overall survival (OS) of acute myeloid leukaemia (AML) patients. Moreover, the mRNA level of this gene is significantly higher in the bone marrow cells of AML patients than in the mobilized peripheral blood haematopoietic stem cells of healthy donors. The overexpression of RNF220 promotes the proliferation of AML cells and accelerates the transition from G1 phase to S phase. Increased protein levels and decreased ubiquitylation levels of Cyclin D1 were observed in the nuclei of cells overexpressing RNF220 compared to those of control cells. The protein level of USP22 was also increased in cells overexpressing RNF220. RNF220 cannot enhance the stability of the Cyclin D1 protein without increased expression of the USP22 protein. Our study provided proof of principle to show that RNF220 promotes stabilization of the Cyclin D1 protein via USP22.

The deubiquitinase USP22 regulates PD-L1 degradation in human cancer cells

Background

Many cancers evade immune surveillance by overexpressing PD-L1. PD-L1 interacted with its receptor PD-1, resulting in reduction of T cell proliferation and activation and thereafter cancer cell death mediated by T-lymphocyte. Understanding the mechanisms that regulate PD-L1 was of vital importance for immune checkpoint blockade therapy (ICBT).

Methods

Human non-small cell lung cancer cells and 293FT cells were used to investigate the function of USP22 upon PD-L1 and CSN5 by WB, Immunoprecipitation, Immunofluorescence and Flow cytometry analysis. B16-F10 cells were used to explore the role of USP22 on tumorigenesis and T cell cytotoxicity. The relationship between USP22 and PD-L1 expression was investigated by Immunohistochemistry analysis in human non-small cell lung cancer samples.

Results

Our data showed that USP22 interacted with PD-L1 and promoted its stability. USP22 deubiquitinated PD-L1 and inhibited its proteasome degradation. Moreover, USP22 also interacted with CSN5 and stabilized CSN5 through deubiquitination. Either USP22 or CSN5 could facilitate the interaction of PD-L1 with the other one. Furthermore, USP22 removed K6, K11, K27, K29, K33 and K63-linked ubiquitin chain of both CSN5 and PD-L1. In addition, USP22 depletion inhibited tumorigenesis and promoted T cell cytotoxicity. Besides, USP22 expression positively correlated with PD-L1 expression in human non-small cell lung cancer samples.

Conclusions

Here, we suggested that USP22 is a new regulator for PD-L1. On the one hand, USP22 could directly regulate PD-L1 stability through deubiquitination. On the other hand, USP22 regulated PD-L1 protein level through USP22-CSN5-PD-L1 axis. In addition, USP22 depletion inhibited tumorigenesis and promoted T cell cytotoxicity. Besides, USP22 expression positively correlated with PD-L1 expression in human non-small cell lung cancer samples. Together, we identified a new regulator of PD-L1 and characterized the important role of USP22 in PD-L1 mediated immune evasion. Targeting USP22 might be a new solution to ICBT.

The E2F Pathway Score as a Predictive Biomarker of Response to Neoadjuvant Therapy in ER+/HER2- Breast Cancer

E2F transcription factors play critical roles in the cell cycle. Therefore, their activity is expected to reflect tumor aggressiveness and responsiveness to therapy. We scored 3905 tumors of nine breast cancer cohorts for this activity based on their gene expression for the Hallmark E2F targets gene set. As expected, tumors with a high score had an increased expression of cell proliferation-related genes. A high score was significantly associated with shorter patient survival, greater MKI67 expression, histological grade, stage, and genomic aberrations. Furthermore, metastatic tumors had higher E2F scores than the primary tumors from which they arose. Although tumors with a high score had greater infiltration by both pro- and anti-cancerous immune cells, they had an increased expression of immune checkpoint genes. Estrogen receptor (ER)-positive/human epidermal growth factor receptor 2 (HER2)-negative cancer with a high E2F score achieved a significantly higher pathological complete response (pCR) rate to neoadjuvant chemotherapy. The E2F score was significantly associated with the expression of cyclin-dependent kinase (CDK)-related genes and strongly correlated with sensitivity to CDK inhibition in cell lines. In conclusion, the E2F score is a marker of breast cancer aggressiveness and predicts the responsiveness of ER-positive/HER2-negative patients to neoadjuvant chemotherapy and possibly to CDK and immune checkpoint inhibitors.

Dynamic modules of the coactivator SAGA in eukaryotic transcription

SAGA (Spt-Ada-Gcn5 acetyltransferase) is a highly conserved transcriptional coactivator that consists of four functionally independent modules. Its two distinct enzymatic activities, histone acetylation and deubiquitylation, establish specific epigenetic patterns on chromatin and thereby regulate gene expression. Whereas earlier studies emphasized the importance of SAGA in regulating global transcription, more recent reports have indicated that SAGA is involved in other aspects of gene expression and thus plays a more comprehensive role in regulating the overall process. Here, we discuss recent structural and functional studies of each SAGA module and compare the subunit compositions of SAGA with related complexes in yeast and metazoans. We discuss the regulatory role of the SAGA deubiquitylating module (DUBm) in mRNA surveillance and export, and in transcription initiation and elongation. The findings suggest that SAGA plays numerous roles in multiple stages of transcription. Further, we describe how SAGA is related to human disease. Overall, in this report, we illustrate the newly revealed understanding of SAGA in transcription regulation and disease implications for fine-tuning gene expression.

A protein that helps add epigenetic information to genome, SAGA, controls many aspects of gene activation, potentially making it a target for cancer therapies. To fit inside the tiny cell nucleus, the genome is tightly packaged, and genes must be unpacked before they can be activated. Known to be important in genome opening, SAGA has now been shown to also play many roles in gene activation. Daeyoup Lee at the KAIST, Daejeon, South Korea, and co-workers have reviewed recent discoveries about SAGA’s structure, function, and roles in disease. They report that SAGA’s complex (19 subunits organized into four modules) allows it to play so many roles, genome opening, initiating transcription, and efficiently exporting mRNAs. Its master role means that malfunction of SAGA may be linked to many diseases.

Molecular crosstalk between cancer and neurodegenerative diseases

The progression of cancers and neurodegenerative disorders is largely defined by a set of molecular determinants that are either complementarily deregulated, or share remarkably overlapping functional pathways. A large number of such molecules have been demonstrated to be involved in the progression of both diseases. In this review, we particularly discuss our current knowledge on p53, cyclin D, cyclin E, cyclin F, Pin1 and protein phosphatase 2A, and their implications in the shared or distinct pathways that lead to cancers or neurodegenerative diseases. In addition, we focus on the inter-dependent regulation of brain cancers and neurodegeneration, mediated by intercellular communication between tumor and neuronal cells in the brain through the extracellular microenvironment. Finally, we shed light on the therapeutic perspectives for the treatment of both cancer and neurodegenerative disorders.

Long non-coding RNA SNHG7 promotes neuroblastoma progression through sponging miR-323a-5p and miR-342-5p

Dysregulation of long non-coding RNAs (lncRNAs) has been known to be relevant to the progression of human cancers, including neuroblastoma (NB). Small nucleolar RNA host gene 7 (SNHG7) has been identified as an oncogene in a series of human cancers. The purpose of the present study was to investigate the function and underlying mechanism of SNHG7 in NB progression. qRT-PCR was used to determine the levels of SNHG7, cyclin D1 (CCND1), miR-323a-5p and miR-342-5p. Cell migration and invasion abilities were detected by transwell assays. Glucose consumption and lactate production were assessed using the corresponding assay kits. The targeted interaction between SNHG7 and miR-323a-5p or miR-342-5p was verified by dual-luciferase reporter and RNA immunoprecipitation (RIP) assays. Xenograft tumor assays were performed to observe the effect of SNHG7 silencing on tumor growth in vivo. We found that SNHG7 was upregulated in NB tissues and cell lines, and high SNHG7 level was relevant to poor prognosis of NB patients. SNHG7 silencing resulted in the repression of NB cell migration, invasion and glycolysis. SNHG7 directly targeted miR-323a-5p and miR-342-5p and negatively modulated their expression in NB cells. The overexpression of miR-323a-5p or miR-342-5p weakened NB cell migration, invasion and glycolysis. Moreover, miR-323a-5p or miR-342-5p mediated the suppressive effect of SNHG7 silencing on NB cell progression. CCND1 was a direct target of miR-323a-5p and miR-342-5p. Additionally, SNHG7 knockdown repressed tumor growth in vivo. In conclusion, our study suggested that SNHG7 silencing hindered NB progression at least partly though sponging miR-323a-5p and miR-342-5p, illuminating its potential value as a therapeutic target.

USP22 positively modulates ERα action via its deubiquitinase activity in breast cancer

Estrogen receptor α (ERα) is the crucial factor in ERα-positive breast cancer progression. Endocrine therapies targeting ERα signaling is one of the widely used therapeutic strategies for breast cancer. However, a large number of the patients become refractory to therapy. Abnormal expression of ERα co-regulator facilitates breast cancer development and tendency of endocrine resistance. Thus, it is necessary to discover the novel co-regulators modulating ERα action. Here, we demonstrate that histone deubiquitinase USP22 is highly expressed in breast cancer samples compared with that in the benign tissue, and high expression of USP22 was significantly associated with poorer overall survival in BCa samples. Moreover, USP22 associates with ERα to be involved in maintenance of ERα stability. USP22 enhances ERα-induced transactivation. We further provide the evidence that USP22 is recruited together with ERα to cis-regulatory elements of ERα target gene. USP22 promotes cell growth even under hypoxia condition and with the treatment of ERα antagonist in breast cancer cells. Importantly, the deubiquitination activity of USP22 is required for its functions on maintenance of ERα stability, thereby enhancing ERα action and conferring endocrine resistance in breast cancer.

Dissenting degradation: Deubiquitinases in cell cycle and cancer

Since its discovery forty years ago, protein ubiquitination has been an ever-expanding field. Virtually all biological processes are controlled by the post-translational conjugation of ubiquitin onto target proteins. In addition, since ubiquitin controls substrate degradation through the action of hundreds of enzymes, many of which represent attractive therapeutic candidates, harnessing the ubiquitin system to reshape proteomes holds great promise for improving disease outcomes. Among the numerous physiological functions controlled by ubiquitin, the cell cycle is among the most critical. Indeed, the discovery that the key drivers of cell cycle progression are regulated by the ubiquitin-proteasome system (UPS) epitomizes the connection between ubiquitin signaling and proliferation. Since cancer is a disease of uncontrolled cell cycle progression and proliferation, targeting the UPS to stop cancer cells from cycling and proliferating holds enormous therapeutic potential. Ubiquitination is reversible, and ubiquitin is removed from substrates by catalytic proteases termed deubiquitinases or DUBs. While ubiquitination is tightly linked to proliferation and cancer, the role of DUBs represents a layer of complexity in this landscape that remains poorly captured. Due to their ability to remodel the proteome by altering protein degradation dynamics, DUBs play an important and underappreciated role in the cell cycle and proliferation of both normal and cancer cells. Moreover, due to their enzymatic protease activity and an open ubiquitin binding pocket, DUBs are likely to be important in the future of cancer treatment, since they are among the most druggable enzymes in the UPS. In this review we summarize new and important findings linking DUBs to cell cycle and proliferation, as well as to the etiology and treatment of cancer. We also highlight new advances in developing pharmacological approaches to attack DUBs for therapeutic benefit.

USP32 promotes tumorigenesis and chemoresistance in gastric carcinoma via upregulation of SMAD2

USP32, a member of the ubiquitin-specific proteases family, has been implicated in the development of breast cancer and small lung cancer. However, its biological functions and clinical significance in gastric cancer (GC) remain unclear. In the present study, we reported that knockdown or depletion of USP32 significantly inhibited GC cell proliferation and migration in vitro and in vivo, indicating that USP32 functions as an oncogene in GC. Importantly, results from immunohistochemical staining in a tissue microarray revealed that USP32 was upregulated in GC tissues compared with paracancerous tissues. Further analyses showed that high expression of USP32 was closely related with high T-staging and poor outcomes of GC patients. Mechanistically, USP32 silencing caused a decrease in the expression of SMAD2, which resulted in the inhibitory effects of GC cells on growth, motility, and chemoresistance to cisplatin. Therefore, our findings strongly suggest the involvement of USP32 in GC progression and provide a potential target for future therapy of GC.

A Robust 6-lncRNA Prognostic Signature for Predicting the Prognosis of Patients With Colorectal Cancer Metastasis

Objective: Our study aimed to construct a robust long non-coding RNA (lncRNA) prognostic signature for colorectal cancer (CRC) metastasis.

Methods: Differentially expressed lncRNAs were identified between metastatic CRC and non-metastatic CRC samples from The Cancer Genome Atlas Database (TCGA) using the edgeR package. The differentially expressed lncRNAs with prognosis of patients with CRC metastasis were identified by univariate Cox regression analysis, followed by a stepwise multivariate Cox regression model. The survminer package in R was used to identify the optimal cutoff point for high-risk and low-risk groups. The receiver operating characteristic (ROC) curves were plotted to assess this signature. To explore potential signaling pathways associated with these lncRNAs, Gene Set Enrichment Analysis (GSEA) was performed.

Results: A 6-lncRNA signature was built based on the lncRNA expression profile for CRC metastasis. The optimal cutoff value was used to classify high-risk and low-risk groups using the survminer package. The high-risk groups could have poorer survival time than the low-risk groups. ROC curve result indicated that this lncRNA signature had high sensitivity and accuracy. GSEA analysis results showed that the six lncRNAs were significantly enriched in several CRC metastasis-related signaling pathways such as “cell cycle,” “DNA replication,” “mismatch repair,” “oxidative phosphorylation,” “regulation of autophagy,” and “insulin signaling pathway.”

Conclusion: Our study constructed a 6-lncRNA model for predicting the survival outcomes of patients with CRC metastasis, which could become potential prognostic biomarkers, and therapeutic targets for CRC metastasis.

USP22 Functions as an Oncogenic Driver in Prostate Cancer by Regulating Cell Proliferation and DNA Repair

Emerging evidence indicates the deubiquitinase USP22 regulates transcriptional activation and modification of target substrates to promote pro-oncogenic phenotypes. Here, in vivo characterization of tumor-associated USP22 upregulation and unbiased interrogation of USP22-regulated functions in vitro demonstrated critical roles for USP22 in prostate cancer. Specifically, clinical datasets validated that USP22 expression is elevated in prostate cancer, and a novel murine model demonstrated a hyperproliferative phenotype with prostate-specific USP22 overexpression. Accordingly, upon overexpression or depletion of USP22, enrichment of cell-cycle and DNA repair pathways was observed in the USP22-sensitive transcriptome and ubiquitylome using prostate cancer models of clinical relevance. Depletion of USP22 sensitized cells to genotoxic insult, and the role of USP22 in response to genotoxic insult was further confirmed using mouse adult fibroblasts from the novel murine model of USP22 expression. As it was hypothesized that USP22 deubiquitylates target substrates to promote protumorigenic phenotypes, analysis of the USP22-sensitive ubiquitylome identified the nucleotide excision repair protein, XPC, as a critical mediator of the USP22-mediated response to genotoxic insult. Thus, XPC undergoes deubiquitylation as a result of USP22 function and promotes USP22-mediated survival to DNA damage. Combined, these findings reveal unexpected functions of USP22 as a driver of protumorigenic phenotypes and have significant implications for the role of USP22 in therapeutic outcomes. SIGNIFICANCE: The studies herein present a novel mouse model of tumor-associated USP22 overexpression and implicate USP22 in modulation of cellular survival and DNA repair, in part through regulation of XPC.

Cyclin D degradation by E3 ligases in cancer progression and treatment

D cyclins include three isoforms: D1, D2, and D3. D cyclins heterodimerize with cyclin-dependent kinase 4/6 (CDK4/6) to form kinase complexes that can phosphorylate and inactivate Rb. Inactivation of Rb triggers the activation of E2F transcription factors, which in turn regulate the expression of genes whose products drive cell cycle progression. Because D-type cyclins function as mitogenic sensors that link growth factor signaling directly with G₁ phase progression, it is not surprising that D cyclin accumulation is dysregulated in a variety of human tumors. Elevated expression of D cyclins results from gene amplification, increased gene transcription and protein translation, decreased microRNA levels, and inefficiency or loss of ubiquitylation-mediated protein degradation. This review focuses on the clinicopathological importance of D cyclins, how dysregulation of Ubiquitin-Proteasome System (UPS) contributes to the overexpression of D cyclins, and the therapeutic potential through targeting D cyclin-related machinery in human tumors.

Deubiquitination in prostate cancer progression: role of USP22

Prostate cancer (PCa) is the leading cause of cancer death in men. With more therapeutic modalities available, the overall survival in PCa has increased significantly in recent years. Patients with relapses after advanced secondgeneration anti-androgen therapy however, often show poor disease prognosis. This group of patients often die from cancer-related complicacies. Multiple approaches have been taken to understand disease recurrence and to correlate the gene expression profile. In one such study, an 11-gene signature was identified to be associated with PCa recurrence and poor survival. Amongst them, a specific deubiquitinase called ubiquitin-specific peptidase 22 (USP22) was selectively and progressively overexpressed with PCa progression. Subsequently, it was shown to regulate androgen receptors and Myc, the two most important regulators of PCa progression. Furthermore, USP22 has been shown to be associated with the development of therapy resistant PCa. Inhibiting USP22 was also found to be therapeutically advantageous, especially in clinically challenging and advanced PCa. This review provides an update of USP22 related functions and challenges associated with PCa research and explains why targeting this axis is beneficial for PCa relapse cases.

The double dealing of cyclin D1

The cell cycle is tightly regulated by cyclins and their catalytic moieties, the cyclin-dependent kinases (CDKs). Cyclin D1, in association with CDK4/6, acts as a mitogenic sensor and integrates extracellular mitogenic signals and cell cycle progression. When deregulated (overexpressed, accumulated, inappropriately located), cyclin D1 becomes an oncogene and is recognized as a driver of solid tumors and hemopathies. Recent studies on the oncogenic roles of cyclin D1 reported non-canonical functions dependent on the partners of cyclin D1 and its location within tumor cells or tissues. Support for these new functions was provided by various mouse models of oncogenesis. Finally, proteomic and transcriptomic data identified complex cyclin D1 networks. This review focuses on these aspects of cyclin D1 pathophysiology, which may be crucial for targeted therapy.Abbreviations: aa, amino acid; AR, androgen receptor; ATM, ataxia telangectasia mutant; ATR, ATM and Rad3-related; CDK, cyclin-dependent kinase; ChREBP, carbohydrate response element binding protein; CIP, CDK-interacting protein; CHK1/2, checkpoint kinase 1/2; CKI, CDK inhibitor; DDR, DNA damage response; DMP1, cyclin D-binding myb-like protein; DSB, double-strand DNA break; DNA-PK, DNA-dependent protein kinase; ER, estrogen receptor; FASN, fatty acid synthase; GSK3β, glycogen synthase-3β; HAT, histone acetyltransferase; HDAC, histone deacetylase; HK2, hexokinase 2; HNF4α, and hepatocyte nuclear factor 4α; HR, homologous recombination; IR, ionizing radiation; KIP, kinase inhibitory protein; MCL, mantle cell lymphoma; NHEJ, non-homologous end-joining; PCAF, p300/CREB binding-associated protein; PGC1α, PPARγ co-activator 1α; PEST, proline-glutamic acid-serine-threonine, PK, pyruvate kinase; PPAR, peroxisome proliferator-activated receptor; RB1, retinoblastoma protein; ROS, reactive oxygen species; SRC, steroid receptor coactivator; STAT, signal transducer and activator of transcription; TGFβ, transforming growth factor β; UPS, ubiquitin-proteasome system; USP22, ubiquitin-specific peptidase 22; XPO1 (or CRM1) exportin 1.

Ubiquitin-specific protease 22 is critical to in vivo angiogenesis, growth and metastasis of non-small cell lung cancer

BACKGROUND

Loss of monoubiquitination of histone H2B (H2Bub1) was found to be associated with poor differentiation, cancer stemness, and enhanced malignancy of non-small cell lung cancer (NSCLC). Herein, we investigated the biological significance and therapeutic implications of ubiquitin-specific protease 22 (USP22), an H2Bub1 deubiquitinase, in non-small cell lung cancer (NSCLC).

METHODS

USP22 expression and its clinical relevance were assessed in NSCLC patients. The effects of USP22 knockout on sensitivity to cisplatin and irradiation, and growth, metastasis of NSCLC xenografts, and survival of cancer-bearing mice were investigated. The underlying mechanisms of targeting USP22 were explored.

RESULTS

Overexpression of USP22 was observed in 49.0% (99/202) of NSCLC tissues; higher USP22 immunostaining was found to be associated with enhanced angiogenesis and recurrence of NSCLC. Notably, USP22 knockout dramatically suppressed in vitro proliferation, colony formation; and angiogenesis, growth, metastasis of A549 and H1299 in mouse xenograft model, and significantly prolonged survival of metastatic cancer-bearing mice. Furthermore, USP22 knockout significantly impaired non-homologous DNA damage repair capacity, enhanced cisplatin and irradiation-induced apoptosis in these cells. In terms of underlying mechanisms, RNA sequencing and gene ontology enrichment analysis demonstrated that USP22 knockout significantly suppressed angiogenesis, proliferation, EMT, RAS, c-Myc pathways, concurrently enhanced oxidative phosphorylation and tight junction pathways in A549 and H1299 NSCLC cells. Immunoblot analysis confirmed that USP22 knockout upregulated E-cadherin, p16; reduced ALDH1A3, Cyclin E1, c-Myc, and attenuated activation of AKT and ERK pathways in these cells.

CONCLUSIONS

Our findings suggest USP22 plays critical roles in the malignancy and progression of NSCLC and provide rationales for targeting USP22, which induces broad anti-cancer activities, as a novel therapeutic strategy for NSCLC patient.

USP22 Interacts with PALB2 and Promotes Chemotherapy Resistance via Homologous Recombination of DNA Double-Strand Breaks

Homologous recombination (HR) is a highly conserved pathway that can facilitate the repair of DNA double-strand breaks (DSB). Several Deubiquitinases (DUB) have been implicated as key players in DNA damage repair (DDR) through HR. Here, we report USP22, a DUB that is highly overexpressed in multiple cancer types, is necessary for HR through a direct interaction with PALB2 through its C-terminal WD40 domain. This interaction stimulates USP22 catalytic activity in vitro. Furthermore, we show USP22 is necessary for BRCA2, PALB2, and Rad51 recruitment to DSBs and this is, in part, through USP22 stabilizing BRCA2 and PALB2 levels. Taken together, our results describe a role for USP22 in DNA repair. IMPLICATIONS: This research provides new and exciting mechanistic insights into how USP22 overexpression promotes chemoresistance in lung cancer. We believe this study, and others, will help aid in developing targeted drugs toward USP22 and known binding partners for lung cancer treatment.

Emerging role of ubiquitin-specific protease 14 in oncogenesis and development of tumor: Therapeutic implication

Ubiquitin (Ub) is a small protein that can be attached to substrate proteins to direct their degradation via the proteasome. Deubiquitinating enzymes (DUBs) reverse this process by removing ubiquitin from its substrate protein. Over the past few decades, ubiquitin-specific protease 14 (USP14), a member of the DUBs, has emerged as an important player in various types of cancers. In this article, we review and summarize biological function of USP14 in tumorigenesis and multiple signaling pathways. To determine its role in cancer, we analyzed USP14 gene expression across a panel of tumors, and discussed that it could serve as a novel bio-marker in several types of cancer. And recent contributions indicated that USP14 has been shown to act as a tumor-promoting gene via the AKT, NF-κB, MAPK pathways etc. Besides, drugs targeting USP14 have shown potential anti-tumor effect and clinical significance. We focus on recent studies that explore the link between USP14 and cancer, and further discuss USP14 as a novel target for cancer therapy.

Recent advances with cyclin-dependent kinase inhibitors: therapeutic agents for breast cancer and their role in immuno-oncology

Introduction: Collaborative interactions between several diverse biological processes govern the onset and progression of breast cancer. These processes include alterations in cellular metabolism, anti-tumor immune responses, DNA damage repair, proliferation, anti-apoptotic signals, autophagy, epithelial-mesenchymal transition, components of the non-coding genome or onco-mIRs, cancer stem cells and cellular invasiveness. The last two decades have revealed that each of these processes are also directly regulated by a component of the cell cycle apparatus, cyclin D1. Area covered: The current review is provided to update recent developments in the clinical application of cyclin/CDK inhibitors to breast cancer with a focus on the anti-tumor immune response. Expert opinion: The cyclin D1 gene encodes the regulatory subunit of a proline-directed serine-threonine kinase that phosphorylates several substrates. CDKs possess phosphorylation site selectivity, with the phosphate-acceptor residue preceding a proline. Several important proteins are substrates including all three retinoblastoma proteins, NRF1, GCN5, and FOXM1. Over 280 cyclin D3/CDK6 substrates have b\een identified. Given the diversity of substrates for cyclin/CDKs, and the altered thresholds for substrate phosphorylation that occurs during the cell cycle, it is exciting that small molecular inhibitors targeting cyclin D/CDK activity have encouraging results in specific tumors.

LINC01355 suppresses breast cancer growth through FOXO3-mediated transcriptional repression of CCND1

Previously, several protein-coding tumor suppressors localized at 1p36 have been reported. In the present work, we focus on functional long non-coding RNAs (lncRNAs) embedded in this locus. Small interfering RNA was used to identify lncRNA candidates with growth-suppressive activities in breast cancer. The mechanism involved was also explored. LINC01355 were downregulated in breast cancer cells relative to non-malignant breast epithelial cells. Overexpression of LINC01355 significantly inhibited proliferation, colony formation, and tumorigenesis of breast cancer cells. LINC01355 arrested breast cancer cells at the G0/G1 phase by repressing CCND1. Moreover, LINC01355 interacted with and stabilized FOXO3 protein, leading to transcriptional repression of CCND1. Importantly, LINC01355-mediated suppression of breast cancer growth was reversed by knockdown of FOXO3 or overexpression of CCND1. Clinically, LINC01355 was downregulated in breast cancer specimens and correlated with more aggressive features. There was a negative correlation between LINC01355 and CCND1 expression in breast cancer samples. LINC01355 acts as a tumor suppressor in breast cancer, which is ascribed to enhancement of FOXO3-mediated transcriptional repression of CCND1. Re-expression of LINC01355 may provide a potential therapeutic strategy to block breast cancer growth and progression.

The role of ubiquitin-specific peptidases in cancer progression

Protein ubiquitination is an important mechanism for regulating the activity and levels of proteins under physiological conditions. Loss of regulation by protein ubiquitination leads to various diseases, such as cancer. Two types of enzymes, namely, E1/E2/E3 ligases and deubiquitinases, are responsible for controlling protein ubiquitination. The ubiquitin-specific peptidases (USPs) are the main members of the deubiquitinase family. Many studies have addressed the roles of USPs in various diseases. An increasing number of studies have indicated that USPs are critical for cancer progression, and some USPs have been used as targets to develop inhibitors for cancer prevention. Herein we collect and organize most of the recent studies on the roles of USPs in cancer progression and discuss the development of USP inhibitors for cancer therapy in the future.

Targeting glutamine-addiction and overcoming CDK4/6 inhibitor resistance in human esophageal squamous cell carcinoma

The dysregulation of Fbxo4-cyclin D1 axis occurs at high frequency in esophageal squamous cell carcinoma (ESCC), where it promotes ESCC development and progression. However, defining a therapeutic vulnerability that results from this dysregulation has remained elusive. Here we demonstrate that Rb and mTORC1 contribute to Gln-addiction upon the dysregulation of the Fbxo4-cyclin D1 axis, which leads to the reprogramming of cellular metabolism. This reprogramming is characterized by reduced energy production and increased sensitivity of ESCC cells to combined treatment with CB-839 (glutaminase 1 inhibitor) plus metformin/phenformin. Of additional importance, this combined treatment has potent efficacy in ESCC cells with acquired resistance to CDK4/6 inhibitors in vitro and in xenograft tumors. Our findings reveal a molecular basis for cancer therapy through targeting glutaminolysis and mitochondrial respiration in ESCC with dysregulated Fbxo4-cyclin D1 axis as well as cancers resistant to CDK4/6 inhibitors.

USP22 controls multiple signaling pathways that are essential for vasculature formation in the mouse placenta

USP22, a component of the SAGA complex, is overexpressed in highly aggressive cancers, but the normal functions of this deubiquitinase are not well defined. We determined that loss of USP22 in mice results in embryonic lethality due to defects in extra-embryonic placental tissues and failure to establish proper vascular interactions with the maternal circulatory system. These phenotypes arise from abnormal gene expression patterns that reflect defective kinase signaling, including TGFβ and several receptor tyrosine kinase pathways. USP22 deletion in endothelial cells and pericytes that are induced from embryonic stem cells also hinders these signaling cascades, with detrimental effects on cell survival and differentiation as well as on the ability to form vessels. Our findings provide new insights into the functions of USP22 during development that may offer clues to its role in disease states.

Ubiquitin-specific protease 22 enhances intestinal cell proliferation and tissue regeneration after intestinal ischemia reperfusion injury

BACKGROUND

Intestinal ischemia reperfusion (I/R) injury is a serious but common pathophysiological process of many diseases, resulting in a high mortality rate in clinical practice. Ubiquitin-specific protease 22 (USP22) acts as regulator of cell cycle progression, proliferation, and tumor invasion. Depleted USP22 expression has been reported to contribute to arrested cell cycle and disrupted generation of differentiated cell types in crypts and villi. However, the role of USP22 in intestinal damage recovery has not been investigated. Therefore, elucidation of the underlying mechanism of USP22 in intestinal I/R injury may help to improve the tissue repair and patient prognosis in clinical practice.

AIM

To investigate the role of USP22 in intestinal cell proliferation and regeneration after intestinal I/R injury.

METHODS

An animal model of intestinal I/R injury was generated in male Sprague-Dawley rats by occlusion of the superior mesenteric artery followed by reperfusion. Chiu’s scoring system was used to grade the damage to the intestinal mucosa. An in vitro model was developed by incubating rat intestinal epithelial IEC-6 cells in hypoxia/reoxygenation conditions in order to simulate I/R in vivo. siRNA and overexpression plasmid were used to regulate the expression of USP22. USP22, Cyclin D1, and proliferating cell nuclear antigen (PCNA) expression levels were measured by Western blot analysis and immunohistochemistry staining. Cell survival (viability) and cell cycle were evaluated using the Cell Counting Kit-8 and flow cytometry, respectively.

RESULTS

USP22 expression was positively correlated with the expression levels of PCNA and Cyclin D1 both in vivo and in vitro, which confirmed that USP22 was involved in cell proliferation and intestinal regeneration after intestinal I/R injury. Decreased levels of Cyclin D1 and cell cycle arrest were observed in the USP22 knockdown group (P < 0.05), while opposite results were observed in the USP22 overexpression group (P < 0.05). In addition, increased expression of USP22 was related to improved intestinal pathology or IEC-6 cell viability after I/R or hypoxia/reoxygenation. These results suggested that USP22 may exert a protective effect on intestinal I/R injury by regulating cell proliferation and facilitating tissue regeneration.

CONCLUSION

USP22 is correlated with promoting intestinal cell proliferation and accelerating intestinal tissue regeneration after intestinal I/R injury and may serve as a potential target for therapeutic development for tissue repair during intestinal I/R injury.

Cyclin D1 Stability Is Partly Controlled by O-GlcNAcylation

Cyclin D1 is the regulatory partner of the cyclin-dependent kinases (CDKs) CDK4 or CDK6. Once associated and activated, the cyclin D1/CDK complexes drive the cell cycle entry and G1 phase progression in response to extracellular signals. To ensure their timely and accurate activation during cell cycle progression, cyclin D1 turnover is finely controlled by phosphorylation and ubiquitination. Here we show that the dynamic and reversible O-linked β-N-Acetyl-glucosaminylation (O-GlcNAcylation) regulates also cyclin D1 half-life. High O-GlcNAc levels increase the stability of cyclin D1, while reduction of O-GlcNAcylation strongly decreases it. Moreover, elevation of O-GlcNAc levels through O-GlcNAcase (OGA) inhibition significantly slows down the ubiquitination of cyclin D1. Finally, biochemical and cell imaging experiments in human cancer cells reveal that the O-GlcNAc transferase (OGT) binds to and glycosylates cyclin D1. We conclude that O-GlcNAcylation promotes the stability of cyclin D1 through modulating its ubiquitination.