Binding of USP4 to cortactin enhances cell migration in HCT116 human colon cancer cells

Ubiquitin-specific protease 4 (USP4) is highly overexpressed in colon cancer and acts as a potent protooncogenic protein by deubiquitinating β-catenin. However, its prominent roles in tumor formation and migration in cancer cells are not fully understood by its deubiquitinating enzyme (DUB) activity on β-catenin. Thus, we investigated an additional role of USP4 in cancer. In this study, we identified cortactin (CTTN), an actin-binding protein involved in the regulation of cytoskeleton dynamics and a potential prognostic marker for cancers, as a new cellular interacting partner of USP4 from proximal labeling of HCT116 cells. Additionally, the role of USP4 in CTTN activation and promotion of cell dynamics and migration was investigated in HCT116 cells. We confirmed that interacting of USP4 with CTTN increased cell movement. This finding was supported by the fact that USP4 overexpression in HCT116 cells with reduced expression of CTTN was insufficient to promote cell migration. Additionally, we observed that USP4 overexpression led to a significant increase in CTTN phosphorylation, which is a requisite mechanism for cell migration, by regulating Src/focal adhesion kinase (FAK) binding to CTTN and its activation. Our results suggest that USP4 plays a dual role in cancer progression, including stabilization of β-catenin as a DUB and interaction with CTTN to promote cell dynamics by inducing CTTN phosphorylation. Therefore, this study demonstrates that USP4 is important for cancer progression and is a good target for treating or preventing cancer.

Ubiquitin-Specific Protease 21 Promotes Colorectal Cancer Metastasis by Acting as a Fra-1 Deubiquitinase

Fos-related-antigen-1 (Fra-1), a member of the activator protein-1 (AP-1) transcription factor superfamily, has an essential role in cancer progress and metastasis and Fra-1 is considered a therapeutic target in metastatic cancer including metastatic colorectal cancer (mCRC). However, its regulation at protein level has not yet been clearly elucidated. We found that ubiquitin-specific protease 21 (USP21) increases Fra-1 stability by deubiquitinating Fra-1 and enhances the expression of Fra-1 target genes in colon cancer cells. We also showed that USP21 controlled Fra-1-dependent migration and invasion activities. The oncogenic property of USP21 was confirmed by a significant reduction in liver metastasis when USP21-knockdown cancer cells were injected intrasplenically into mice. Consistently, clinicopathological analysis of colorectal cancer patients revealed a correlation of USP21 expression with high-grade carcinoma and life span. These results demonstrate that USP21 enhances Fra-1 stability and AP-1 target gene expression by deubiquitinating Fra-1. Therefore, USP21 is considered an attractive therapeutic target in mCRC with high Fra-1 expression.

A Selective Inhibitor of Ubiquitin-Specific Protease 4 Suppresses Colorectal Cancer Progression by Regulating β-Catenin Signaling

BACKGROUND/AIMS

Dysregulation of deubiquitinating enzymes (DUBs), which regulate the stability of key proteins, has been implicated in many human diseases, including cancers. Thus, DUBs can be considered as potential therapeutic targets for many diseases. Among them, USP4 has been proposed as a promising target for colon cancer drugs since USP4 controls the stability of β-catenin, a key factor in the Wnt signaling involved in the tumorigenesis of colorectal cancer. However, developing potential DUB inhibitors has been hindered because many DUBs harbor similar active site structures and show broad substrate specificities.

METHODS

By performing in vitro deubiquitinating activity assays using a chemical library, we identified several potential DUB inhibitors. Among them, only neutral red (NR) showed selective inhibitory activity on USP4 in a cell-based assay system. In colon cancer cells, NR affected the protein stability of β-catenin, as shown by immunoblotting, and it affected the target gene expression of β-catenin, as shown by quantitative real-time PCR. NR's potential as an anticancer drug was further estimated by colony formation and cell migration assays and by using a mouse xenograft model.

RESULTS

We identified NR as an uncompetitive inhibitor of USP4 and validated its effects in colorectal cancer. NR-treated cells showed decreased β-catenin stability and reduced expression of β-catenin target genes. Additionally, treating colon cancer cells with NR significantly reduced colony formation and cell migration, and injecting NR into a mouse xenograft model reduced the tumor volume.

CONCLUSION

The current results suggest that NR could be developed as an anticancer drug targeting USP4, and they support the possibility of developing specific DUB inhibitors as therapeutic agents.

Suppression of the Ubiquitin Pathway by Small Molecule Binding to Ubiquitin Enhances Doxorubicin Sensitivity of the Cancer Cells

Development of inhibitors for ubiquitin pathway has been suggested as a promising strategy to treat several types of cancers, which has been showcased by recent success of a series of novel anticancer drugs based on inhibition of ubiquitin pathways. Although the druggability of enzymes in ubiquitin pathways has been demonstrated, ubiquitin itself, the main agent of the pathway, has not been targeted. Whereas conventional enzyme inhibitors are used to silence the ubiquitination or reverse it, they cannot disrupt the binding activity of ubiquitin. Herein, we report that the scaffolds of sulfonated aryl diazo compounds, particularly Congo red, could disrupt the binding activity of ubiquitin, resulting in the activity equivalent to inhibition of ubiquitination. NMR mapping assay demonstrated that the chemical directly binds to the recognition site for ubiquitin processing enzymes on the surface of ubiquitin, and thereby blocks the binding of ubiquitin to its cognate receptors. As a proof of concept for the druggability of the ubiquitin molecule, we demonstrated that Congo red acted as an intracellular inhibitor of ubiquitin recognition and binding, which led to inhibition of ubiquitination, and thereby, could be used as a sensitizer for conventional anticancer drugs, doxorubicin.

Ubiquitin-specific protease 4 (USP4) suppresses myoblast differentiation by down regulating MyoD activity in a catalytic-independent manner

For myotube formation, proliferation and differentiation of myoblasts must be tightly regulated by various myogenic regulatory factors (MRFs) such as MyoD, myogenic factor 5 (Myf5), myogenin, and muscle-specific regulatory factor 4 (MRF4). However, it is not clear how the expression or activity of these MRFs is controlled during myogenesis. In this study, we identified ubiquitin-specific protease 4 (USP4), one of deubiquitinating enzymes, as a suppressor of MRFs by demonstrating that a knockdown of USP4 enhances myogenesis by controlling MyoD and the level of myogenesis marker proteins in C2C12 cells. However, it was revealed that the effect of USP4 on myogenesis is independent of its deubiquitinase activity because the catalytic-site mutant has the same inhibitory effects as the wild-type USP4 on myogenesis. We observed that the activity and protein levels of both HDAC1 and HDAC4 are decreased when myoblast differentiation is promoted by the USP4 knockdown. We also found that the role of USP4 in muscle differentiation is correlated with two major signaling pathways in myogenesis, AKT and the p38 mitogen-activated protein kinase pathways. According to these results, we propose that USP4 is a key player in myogenic differentiation; it controls myogenic regulatory factors in a catalytic-independent manner.

Ubiquitin-specific protease 4 controls metastatic potential through β-catenin stabilization in brain metastatic lung adenocarcinoma

Brain metastasis is the most common type of intracranial cancer and is the main cause of cancer-associated mortality. Brain metastasis mainly originates from lung cancer. Using a previously established in vitro brain metastatic model, we found that brain metastatic PC14PE6/LvBr4 cells exhibited higher expression of β-catenin and increased migratory activity than parental PC14PE6 cells. Knockdown of β-catenin dramatically suppressed the motility and invasiveness of PC14PE6/LvBr4 cells, indicating β-catenin is involved in controlling metastatic potential. Since β-catenin protein was increased without a significant change in its mRNA levels, the mechanism underlying increased β-catenin stability was investigated. We found that ubiquitin-specific protease 4 (USP4), recently identified as a β-catenin-specific deubiquitinylating enzyme, was highly expressed in PC14PE6/LvBr4 cells and involved in the increased stability of β-catenin protein. Similar to β-catenin knockdown, USP4-silenced PC14PE6/LvBr4 cells showed decreased migratory and invasive abilities. Moreover, knockdown of both USP4 and β-catenin inhibited clonogenicity and induced mesenchymal-epithelial transition by downregulating ZEB1 in PC14PE6/LvBr4 cells. Using bioluminescence imaging, we found that knockdown of USP4 suppressed brain metastasis in vivo and significantly increased overall survival and brain metastasis-free survival. Taken together, our results indicate that USP4 is a promising therapeutic target for brain metastasis in patients with lung adenocarcinoma.

Ubiquitin specific protease 4 positively regulates the WNT/β-catenin signaling in colorectal cancer

β-catenin is a key signal transducer in the canonical WNT pathway and is negatively regulated by ubiquitin-dependent proteolysis. Through screening of various deubiquitinating enzymes (DUBs), we identified ubiquitin specific protease 4 (USP4) as a candidate for β-catenin-specific DUB. The effects of USP4 overexpression or knockdown suggested that USP4 positively controls the stability of β-catenin and enhances β-catenin-regulated transcription. Domain mapping results revealed that the C-terminal catalytic domain is responsible for β-catenin binding and nuclear transport. Examination of colon cancer tissues from patients revealed a correlation between elevated expression levels of USP4 and β-catenin. Consistent with this correlation, USP4 knockdown in HCT116, a colon cancer cell line, reduced invasion and migration activity. These observations indicate that USP4 acts as a positive regulator of the WNT/β-catenin pathway by deubiquitination and facilitates nuclear localization of β-catenin. Therefore, we propose that USP4 is a potential target for anti-cancer therapeutics.

In vitro and in vivo inhibition of glucocorticoid-induced osteoporosis by the hexane extract of Poncirus trifoliata

This study was performed to discover a novel herbal therapeutic for effective glucocorticoid-induced osteoporosis (GIO) treatment and further to clarify its molecular mechanism of action. Ethanol or methanol extracts of 68 edible Korean native plants were screened to find effective natural plant sources for the treatment of GIO, and Poncirus trifoliata (L.) (Rutaceae, PT) was selected as a final candidate because of its high inhibitory activity plus its novelty. The hexane extract of PT (PT-H) inhibited apoptotic cell death in dexamethasone-induced osteoblastic cell lines, C3H10T1/2 and MC3T3-E1. In vivo mouse results indicated that PT-H not only had an inhibitory effect on the bone loss caused by glucocorticoid, but also promoted bone formation. The molecular mechanisms behind the effect of PT-H on GIO were further clarified by screening of differentially expressed genes (DEGs) between dexamethasone (Dex)-induced osteoblastic cells with or without PT-H treatment. Finally, it was found that the expression level of AnxA6 in Dex-induced osteoblastic cells and prednisolone (PD)-treated GIO-model mice was significantly decreased by PT-H treatment. These findings suggest that PT-H has a strong in vitro and in vivo inhibitory effect on GIO, and decreased expression of AnxA6 may play a key role in this inhibition.

Poncirin promotes osteoblast differentiation but inhibits adipocyte differentiation in mesenchymal stem cells

Poncirin, flavanone glycoside, isolated from the fruit of Poncirus trifoliata, has anti-bacterial and anti-inflammatory activities. In this study, the effects of poncirin on the differentiation of mesenchymal stem cells were investigated. The C3H10T1/2 mesenchymal stem cells and primary bone marrow mesenchymal stem cells were studied. In the C3H10T1/2 cells, poncirin prevented adipocyte differentiation, as demonstrated by inhibition of cytoplasm lipid droplet accumulation and peroxisome proliferator-activating receptor-γ (PPAR-γ) and CCAAT-enhancer-binding protein-β (C/EBP-β) mRNA expression. By contrast, poncirin enhanced the expression of the key osteogenic transcription factors, runt-related transcription factor 2 (Runx2) and transcriptional coactivator with PDZ-binding motif (TAZ). Poncirin also enhanced expression of the osteogenic marker genes including alkaline phosphatase (ALP) and osteocalcin (OC). Poncirin increased mineral nodule formation in primary bone marrow mesenchymal stem cells. These results suggest that poncirin prevents adipogenesis and enhances osteoblast differentiation in mesenchymal stem cells.

Glucocorticoid induces apoptosis of osteoblast cells through the activation of glycogen synthase kinase 3beta

Glucocorticoids (GCs), which play an important role in the normal regulation of bone remodeling, are widely used as anti-inflammatory and chemotherapeutic agents. However, continued exposure to GCs results in osteoporosis, which is partially due to apoptosis of osteoblasts and osteocytes. To understand the mechanism of how GCs induce cell death in osteoblasts, we examined apoptotic effects of dexamethasone (Dex), GC, on MC3T3-E1 osteoblast cells. Results revealed that Dex-induced apoptosis was inhibited by a GC receptor antagonist, mifepristone, and a general caspase inhibitor, Z-VAD-fmk, indicating that Dex induces apoptosis of MC3T3-E1 cells through the pathways involved in GC receptor and caspase. Glycogen synthase kinase 3beta (GSK3beta) is known to participate in apoptosis signaling in MC3T3-E1 cells. Dex activated both GSK3beta and p38-mitogen-activated protein kinase (MAPK). The inhibition of GSK3beta by inhibitor (LiCl) or small interference RNA (siRNA) decreased apoptosis. In contrast, the inhibition of p38-MAPK by inhibitor (SB203580) or siRNA did not decrease, but increase apoptosis. These results suggest that Dex-mediated apoptosis of osteoblasts is facilitated by GSK3beta, but prevented by p38-MAPK.

Prebiopsy localisation of impalpable breast lesions

Prebiopsy localization of impalpable breast lesions (IBL) assures removal of suspicious mammographically detected lesions. Specimen radiograph of the excised specimen is mandatory to confirm complete excision. The aim of this study was to audit our series of percutaneous hookwire localization and to determine the positive biopsy rate of the mammographically detected impalpable breast lesion in our center. Thirty-eight patients with suspicious IBL underwent excision biopsy under mammographic localization in our unit from late February 1998 to May 2003. The excised specimen is immobilized and compressed within the Transpec device. This device incorporates a reference grid visible in the specimen radiograph. Hence, the target lesion marked in the reference grid of the specimen radiograph will allow precise examination and exact localization of the suspicious lesion by the pathologist. The positive biopsy rate for malignant lesion was 26.3%, the majority fall in the range of 40-59 age group. Thirty-two (84.2%) of the patients had clustered micro-calcifications, 4 (10.5%) had impalpable mass lesions and in 2 (5.3%) spiculated lesions were seen on the preoperative mammogram. Mammographic feature of clustered micro-calcification accounts for all the malignant lesions in our series. Utilization of Transpec device has shown to be practical, reliable and cost effective in the management of IBL. Nonetheless, it should be emphasized that optimal specimen radiography and pathological correlation requires close cooperation between radiologist, surgeon and pathologist.

Peptidases affecting recombinant protein production by Streptomyces lividans

The influence of peptidases on human interleukin-3 (rhIL-3) production by a recombinant Streptomyces lividans strain was investigated. The bacterium produced several general peptidases and tripeptidyl peptidases compromising the authenticity of rhIL-3. The level of peptidases depended on growth morphology. Growing S. lividans as compact pellets successfully reduced peptidase activity. Maximum general peptidase activity in pellet culture was delayed after maximum rhIL-3 concentration was achieved. The activity of the tripeptidyl peptidase was product (rhIL-3) associated.

Purification and some properties of a beta-glucosidase from Trichoderma harzianum type C-4

Type C-4 strain of Trichoderma harzianum was isolated as a microorganism with high cellulolytic activity. Beta-glucosidase is involved in the last step of cellulose saccharification by degrading cellobiose to glucose, and plays an important role in the cellulase enzyme system with a synergic action with endoglucanase and cellobiohydrolase for cellulose degradation. Beta-glucosidase from T. harzianum type C-4 was purified to homogeneity through Sephacryl S-300, DEAE-Sephadex A-50, and Mono P column chromatographies. It was a single polypeptide with the molecular mass of 75,000 by SDS-PAGE. The enzyme was very active at pH 5.0 and 45 degrees C. No significant inhibition was observed in the presence of metal ions, thiol reagents, or EDTA. The enzyme was stable in the presence of 5% ox gall and digestive enzymes. p-Nitrophenyl-beta-D-cellobioside worked as a substrate for the enzyme as much as p-nitrophenyl-beta-glucopyranoside. Glucose and gluconolactone showed competitive inhibition with a Ki of 1 mM and 1.8 microM, respectively, while galactose, mannose, and xylose did not inhibit the enzyme significantly.

Characterization of angiotensin II antagonism displayed by SK-1080, a novel nonpeptide AT1-receptor antagonist

The pharmacologic profile of SK-1080, a nonpeptide AT1-selective angiotensin-receptor antagonist, was investigated by receptor-binding studies, functional in vitro assays with rabbit and rat aorta, and in vivo experiments in pithed rats. SK-1080 inhibited the specific binding of [125I]-[Sar1, Ile8]-angiotensin II to human recombinant AT1 receptor with a 12-fold greater potency than losartan [median inhibitory concentration (IC50): 1.01 and 12.3 nM, respectively], but it did not inhibit the binding of [125I]-CGP 42112A to human recombinant AT2 receptor (IC50: >10 microM for both). The Hill coefficient for the competition curve of SK-1080 against AT1 receptor was not significantly different from unity (0.96). Scatchard analysis showed that SK-1080 interacted with human recombinant AT1 receptor in a competitive manner, as with losartan. In functional studies with rat and rabbit aorta, SK-1080 competitively inhibited the contractile response to angiotensin II (pKB values: 9.97 and 9.51, respectively) with 15-25% decrease in the maximal contractile responses, unlike losartan, which showed competitive antagonism without any change in the maximal contractile responses to angiotensin II (pA2 values, 8.02 and 7.59, respectively). In pithed rats, SK-1080 (i.v.) induced a nonparallel right shift in the dose-pressor response curve to angiotensin II (ID50, 0.07 mg/kg) with a dose-dependent reduction in the maximal responses; this antagonistic effect was approximately 25 times more potent than losartan (ID50, 1.74 mg/kg), which showed competitive antagonism. SK-1080 did not alter the responses induced by other agonists such as norepinephrine, KCI, and vasopressin in isolated rabbit aorta and pithed rats. These results suggest that SK-1080 is a highly potent AT1-selective angiotensin II-receptor antagonist with a mode of insurmountable antagonism.