RNAi-mediated COPS3 gene silencing inhibits metastasis of osteogenic sarcoma cells

Targeting the COP9 signalosome for cancer therapy

The COP9 signalosome (CSN) is a highly conserved protein complex composed of 8 subunits (CSN1 to CSN8). The individual subunits of the CSN play essential roles in cell proliferation, tumorigenesis, cell cycle regulation, DNA damage repair, angiogenesis, and microenvironmental homeostasis. The CSN complex has an intrinsic metalloprotease that removes the ubiquitin-like activator NEDD8 from cullin-RING ligases (CRLs). Binding of neddylated CRLs to CSN is sensed by CSN4 and communicated to CSN5 with the assistance of CSN6, thus leading to the activation of deneddylase. Therefore, CSN is a crucial regulator at the intersection between neddylation and ubiquitination in cancer progression. Here, we summarize current understanding of the roles of individual CSN subunits in cancer progression. Furthermore, we explain how the CSN affects tumorigenesis through regulating transcription factors and the cell cycle. Finally, we discuss individual CSN subunits as potential therapeutic targets to provide new directions and strategies for cancer therapy.

Knockdown of COPS3 inhibits the progress of prostate cancer through reducing phosphorylated p38 MAPK expression and impairs the epithelial-mesenchymal transition process

BACKGROUND

The amplification of gene COPS3 is closely related to the development of osteosarcoma and hepatocellular carcinoma. However, the effects of COPS3 on prostate cancer (PCa) are poorly understood.

METHODS

In this study, the protein expression of COPS3 in PCa tissues, adjacent normal tissues, and bone metastasis tissues of PCa was analyzed by immunohistochemistry. Furthermore, cell proliferation, colony formation, migration, and invasion assay were performed in 22rv1 and PC-3 cells after knocking down COPS3 by small interfering RNAs. Furthermore, we performed western blot analysis to explore the potential mechanisms underlying it.

RESULTS

This study found that the overall survival of the COPS3 high-expression group was significantly shorter than the low-expression group. This study discovered that the protein expression of COPS3 in PCa tissues was higher than that in the matched nontumor prostate tissues. In addition, tissues from bone metastasis of PCa had a high percentage of overexpressing COPS3. After knockdown of the COPS3 gene in 22rv1 and PC3 cells, two classic human PCa cell lines which had a high level of COPS3, the abilities of migration, invasion, and proliferation were inhibited. Finally, protein levels of phosphorylated P38 mitogen-activated protein kinase (MAPK) and N-cadherin were significantly decreased after knocking down the expression of COPS3, and the protein levels of E-cadherin were significantly increased.

CONCLUSIONS

In conclusion, COPS3 may be closely related to the progress of PCa. Knockdown of COPS3 inhibited the progress of PCa through reducing the levels of phosphorylated P38 MAPK and impaired the epithelial-mesenchymal transition process.

Inhibition of neddylation induces mitotic defects and alters MKLP1 accumulation at the midbody during cytokinesis

The cullin-RING E3 ubiquitin ligases (CRLs) play crucial roles in modulating the stability of proteins in the cell and are, in turn, regulated by post-translational modification by the ubiquitin-like (Ubl) protein NEDD8. This process, termed neddylation, is reversible through the action of the COP9 signalosome (CSN); a multi-subunit metalloprotease conserved among eukaryotes that plays direct or indirect roles in DNA repair, cell signaling and cell cycle regulation in part through modulating the activity of the CRLs. Previously, inhibition of CRL neddylation by MLN4924, a small molecule inhibitor of the NEDD8-activating enzyme 1 (NAE1), was shown to induce interphase cell cycle arrest and cell death. Using fixed and living cell microscopy, we re-evaluated the cell cycle effects of inhibition of neddylation by MLN4924 in both asynchronous and mitotic cell populations. Consistent with previous studies, treatment of asynchronous cells with MLN4924 increased CDT1 expression levels, induced G2 arrest and increased nuclear size. However, in synchronized cells treated in mitosis, mitotic defects were observed including lagging chromosomes and binucleated daughter cells. Consistent with neddylation and deneddylation playing a role in cytokinesis, NEDD8, as well as subunits of the CSN, could be localized at the midbody and cleavage furrow. Finally, treatment of mitotic cells with MLN4924 induced the premature accumulation of MKLP1 at the cleavage furrow, a key regulator of cytokinesis, which was concomitant with increased abscission delay and failure. Thus, these studies uncover an uncharacterized mitotic effect of MLN4924 on MKLP1 accumulation at the midbody and support a role for neddylation during cytokinesis.

Abbreviations: CSN, COP9 Signalosome; MKLP1, mitotic kinesin-like protein 1; NEDD8, Neural precursor cell Expressed, Developmentally Down-regulated 8.

The CSN3 subunit of the COP9 signalosome interacts with the HD region of Sos1 regulating stability of this GEF protein

Sos1 is an universal, widely expressed Ras guanine nucleotide-exchange factor (RasGEF) in eukaryotic cells. Its N-terminal HD motif is known to be involved in allosteric regulation of Sos1 GEF activity through intramolecular interaction with the neighboring PH domain. Here, we searched for other cellular proteins also able to interact productively with the Sos1 HD domain. Using a yeast two-hybrid system, we identified the interaction between the Sos1 HD region and CSN3, the third component of the COP9 signalosome, a conserved, multi-subunit protein complex that functions in the ubiquitin–proteasome pathway to control degradation of many cellular proteins. The interaction of CSN3 with the HD of Sos1 was confirmed in vitro by GST pull-down assays using truncated mutants and reproduced in vivo by co-immunoprecipitation with the endogenous, full-length cellular Sos1 protein. In vitro kinase assays showed that PKD, a COP9 signalosome-associated-kinase, is able to phosphorylate Sos1. The intracellular levels of Sos1 protein were clearly diminished following CSN3 or PKD knockdown. A sizable fraction of the endogenous Sos1 protein was found ubiquitinated in different mammalian cell types. A significant reduction of RasGTP formation upon growth factor stimulation was also observed in CSN3-silenced as compared with control cells. Our data suggest that the interaction of Sos1 with the COP9 signalosome and PKD plays a significant role in maintenance of cellular Sos1 protein stability and homeostasis under physiological conditions and raises the possibility of considering the CSN/PKD complex as a potential target for design of novel therapeutic drugs.

Integrated analysis of microfibrillar-associated proteins reveals MFAP4 as a novel biomarker in human cancers

Aim: The potential functions and underlying mechanism of microfibrillar-associated proteins (MFAPs) are explored in human cancers. Materials & methods: Here, we examined the expression profiles, prognostic values, epigenetic and genetic alterations of MFAPs in human cancers from public omics repository. Results: Among MFAPs family, MFAP4 was frequently downregulated in the most human cancers and high mRNA expression of MFAP4 significantly correlated with better overall survival in breast cancer. DNA hypermethylation in the promoter of MFAP4 decreased its mRNA expression. MFAP4 strongly associated with pathway in impairment and alteration of the elastic fibers. Conclusion: This integrated analysis provides new insights into MFAPs in human cancers and indicates that MFAP4 could be used as novel biomarker for developing therapies against human cancers.

Novel oncogene COPS3 interacts with Beclin1 and Raf-1 to regulate metastasis of osteosarcoma through autophagy

Background

Expression of COP9 signalosome subunit 3 (COPS3), an oncogene overexpressed in osteosarcoma, has been demonstrated to be significantly correlated with tumor metastasis. However, the underlying mechanism by which COPS3 promotes metastasis of osteosarcoma and its role in autophagy remain unknown.

Methods

The expression of COPS3 was detected in primary osteosarcoma tissues and matching lung metastasis tissues by immunohistochemistry (IHC). The effect of COPS3 on the metastasis of osteosarcoma cells was investigated by transwell, wound healing assays and animal studies. Indicated proteins was analyzed by western blotting when COPS3 was knockdown or overexpressed. The COPS3 Interacting protein was determined by immunoprecipitation assay. The relationship between COPS3 and autophagy was detected by western blotting and immunofluorescence.

Results

We found that knockdown of COPS3 significantly reduced the lung metastasis of osteosarcoma cells in a mouse model, coinciding with downregulation of mitogen-activated protein kinase (MEK) and extracellular signal-regulated kinase (ERK) signaling. The silencing of COPS3 also inhibited the epithelial–mesenchymal transition (EMT) through the 90 kDa ribosomal S6 kinases (RSK), a family of signal transduction proteins downstream of MEK/ERK. Reciprocal immunoprecipitation assays revealed that COPS3 directly interacts with Raf-1, an upstream regulator of MEK/ERK. Surprisingly, Beclin1, an important autophagic protein, appeared in the COPS3-immunoprecipitates, along with the autophagic markers LC3-I and LC3-II. Loss of COPS3 completely inhibited H₂O₂-induced autophagic flux and reduced Beclin1 expression. Additionally, autophagy inhibitor or silencing of Beclin1 both decreased cell metastasis.

Conclusions

Taken together, these data reveal a novel function of COPS3 in the regulation of autophagy and highlight the relationship between autophagy and metastasis in osteosarcoma cells.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0791-6) contains supplementary material, which is available to authorized users.

Overexpression of COPS3 promotes clear cell renal cell carcinoma progression via regulation of Phospho-AKT(Thr308), Cyclin D1 and Caspase-3

The third subunit of the COP9 signalosome (COPS3) is associated with cell proliferation and tumorigenesis process in cancer. The present study showed that the expression level of COPS3 was upregulated in malignant cell lines and COPS3 overexpression was related with clinical stage, T stage, historical grade. Kaplan-Meier survival curves showed that COPS3 may function as a prognostic factor for overall survival. CCK-8 and colony formation assays revealed that knockdown of COPS3 in ACHN and 786-O significantly impacted proliferation in vitro. In addition, flow cytometry showed that inhibition of COPS3 induced G0/G1 arrest and promoted apoptosis. COPS3 may promote kidney cancer progression by altering Phospho-AKT(Thr308), Cyclin D1 and Caspase-3 expression. Collectively, Our findings suggest that COPS3 may be a new potential target of ccRCC.

Knockdown of COPS3 Inhibits Lung Cancer Tumor Growth in Nude Mice by Blocking Cell Cycle Progression

COPS3 encodes the third subunit of the COP9 signalosome and its aberrant expression is associated with many RITE ("Region of Increased Tumor Expression") genes in lung cancer tissues. To elucidate the specific role of COPS3 in lung cancer, we examined its expression in lung cancer tissues by immunohistochemical staining. We found that COPS3 was overexpressed in most of the lung cancer samples examined, particularly in small cell carcinoma and squamous cell carcinoma. The expression of COPS3 protein was positively correlated with the level of Ki-67 cell proliferation index (p=0.001) and negatively related to the degree of tumor differentiation (p=0.012). In a xenograft tumor model in nude mice, shRNA-knockdown of COPS3 significantly reduced tumor growth. In lung adenocarcinoma A549 cells, shRNA-knockdown of COPS3 induced cell cycle arrest at G0/G1 phase by upregulating the cell cycle regulator protein P21 and downregulating cyclin B1 and CDK4. These data suggest that COPS3 may promote tumor growth by regulating cell-cycle associated proteins.

The up-regulation of cysteine-rich protein 61 induced by transforming growth factor beta enhances osteosarcoma cell migration

Overexpressed cysteine-rich protein 61 (Cyr61) is believed to enhance osteosarcoma (OS) cell metastasis, but the mechanism of Cyr61 overexpression in OS is not clear so far. In this study 33 OS samples were analyzed by immunostaining and focused on two parts: the correlation between overexpression of Cyr61 and OS metastasis; the mechanism of regulating Cyr61 expression in OS. Twenty-five out of 33 cases (75.76 %) with metastasis showed high expression of Cyr61. Furthermore, Cyr61 expression in Saos-2 cells was reduced by siRNA, and lower expression of Cyr61 in Saos-2 cell resulted in a cell migration deficiency and had no effect on cell proliferation. Particularly, Cyr61 expression was significantly increased in Saos-2 cells in response to different dosages of transforming growth factor beta (TGF-β), indicating that the expression of Cyr61 is TGF-β dependent. A transwell assay showed that Saos-2 cells stimulated with TGF-β had a greater capacity for migration than the control cells. The p38 MAPK-specific inhibitor SB203580 was able to reduce Cyr61 expression and inhibit the migration of Saos-2 cells stimulated with TGF-β. These results obtained provide new evidence that overexpressed Cyr61 plays a key role in the metastasis of OS cells and Cyr61 is a potential target downstream of TGF-β/p38 MAPK to regulate cell migration.

Silencing of the COPS3 gene by siRNA reduces proliferation of lung cancer cells most likely via induction of cell cycle arrest and apoptosis

The COPS3 gene has stimulating effect on cell proliferation and progression of osteosarcomas and related cells. However, the features of COPS3 and its potential application as a therapeutic target in other cancers has not yet been studied. In this study, therefore, the effect of COPS3 silencing via COPS3 siRNA on lung cancer cell proliferation was examined. Expression levels of COPS3 gene in COPS3 siRNA infected cells and control siRNA infected cells were compared with real time PCR and Western blot analysis. Cell proliferation levels were comprehensively analyzed by MTT, BrdU incorporationy, and colony formation assays. For mechanistic assessment the effects of COPS3 silencing on cell cycle and apoptosis were analyzed using flow cytometry. Results showed that successful silencing of the COPS3 gene at both translational and transcriptional levels significantly reduced the proliferation and colony formation by lung cancer cells (p<0.01). Flow cytometry showed cell cycle arrest in the G0/G1 phase after COPS3 silencing, and more importantly, apoptosis was induced as a result of COPS3 knockdown, which negatively affected cell survival. Therefore, these results provide another piece of important evidence that the COPS3 gene expressed in lung cancer cells may play a critical role in stimulating proliferation. Down-regulation of COPS3 could significantly inhibit lung cancer cell growth, which was most likely mediated via induction of cell cycle arrest in G0/G1 phase and apoptosis.

Identification of novel candidate oncogenes in chromosome region 17p11.2-p12 in human osteosarcoma

Osteosarcoma is the most common primary malignancy of bone. The tumours are characterized by high genomic instability, including the occurrence of multiple regions of amplifications and deletions. Chromosome region 17p11.2–p12 is amplified in about 25% of cases. In previous studies, COPS3 and PMP22 have been identified as candidate oncogenes in this region. Considering the complexity and variation of the amplification profiles for this segment, the involvement of additional causative oncogenes is to be expected. The aim of the present investigation is to identify novel candidate oncogenes in 17p11.2–p12. We selected 26 of in total 85 osteosarcoma samples (31%) with amplification events in 17p11.2–p12, using quantitative PCR for 8 marker genes. These were subjected to high-resolution SNP array analysis and subsequent GISTIC analysis to identify the most significantly amplified regions. Two major amplification peaks were found in the 17p11.2–p12 region. Overexpression as a consequence of gene amplification is a major mechanism for oncogene activation in tumours. Therefore, to identify the causative oncogenes, we next determined expression levels of all genes within the two segments using expression array data that could be generated for 20 of the selected samples. We identified 11 genes that were overexpressed through amplification in at least 50% of cases. Nine of these, c17orf39, RICH2, c17orf45, TOP3A, COPS3, SHMT1, PRPSAP2, PMP22, and RASD1, demonstrated a significant association between copy number and expression level. We conclude that these genes, including COPS3 and PMP22, are candidate oncogenes in 17p11.2–p12 of importance in osteosarcoma tumourigenesis.

Inhibition of Csn3 expression induces growth arrest and apoptosis of hepatocellular carcinoma cells

PURPOSE

Csn3 (or CSN3) encodes the third subunit of an eight-subunit complex, the COP9 signalosome (CSN), which acts as a protein kinase and a deneddylase in mammalian cells. Previous studies have shown that Csn3 is essential for maintenance of cell proliferation in the mouse embryonic epiblast and associated with the tumorigenesis process in osteosarcoma. However, its correlation with hepatocellular carcinoma (HCC) has not been explored yet.

METHODS

The expression of Csn3 in HCC (n = 30), cirrhosis (n = 30), and normal tissues (n = 30) was detected using immunohistochemical analysis. The impacts of lentivirus-mediated inhibition of Csn3 on HCC cells were detected using MTT, BrdU incorporation assay, and flow cytometric analysis. In addition, the colony formation and tumor growth ability in nude mice were detected to define the role of Csn3 in tumorigenesis.

RESULTS

Knockdown of Csn3 expression in HCC cell lines (SMMC-7721 and Hep3B) significantly inhibits the tumor growth both in vitro and in vivo. Further investigation indicates that this growth inhibition effect may be mediated through cell cycle arrest in G0/G1 phase and inductions of pro-apoptotic proteins BIK and Caspase-8. In addition, knockdown of Csn3 expression evidently suppresses tumor growth in a xenograft nude mice model.

CONCLUSION

Collectively, this study demonstrates Csn3 as an oncogene that regulates the tumorigenesis process in HCC cells.

THE COP9 SIGNALOSOME, A NOVEL, ESSENTIAL REGULATOR OF SKELETAL DEVELOPMENT AND TUMORIGENESIS

In recent years, the evolutionarily conserved complex named COP9 signalosome has emerged as an essential and versatile regulator of biological and pathological responses across species. Various components of COP9 signalosome, including CSN5 (also named JAB1), play critical roles in a wide array of developmental process. Using genetically engineered mouse models, our laboratory has recently identified CSN5/JAB1 as an essential regulator of skeletal development, in part through negatively regulating BMP signaling. BMP signaling is important for fracture healing and bone regeneration. BMPs have been used for treating acute fractures and for improving the success of spinal fusions. Therefore, harnessing the CSN5/JAB1-mediated inhibition of BMP signaling might be a novel strategy to improve the efficacy of BMP treatment and to reduce medical costs in the future. Furthermore, the up-regulation of COP9 signalosome has been associated with various cancers, including osteosarcoma. Thus, the COP9 signalosome can also be a valid target for treating osteosarcoma and other tumors.