NCAPG is transcriptionally regulated by CBX3 and activates the Wnt/ß-catenin signaling pathway to promote proliferation and the cell cycle and inhibit apoptosis in colorectal cancer.

Background: Colorectal cancer (CRC) is highly heterogeneous at the genetic and molecular level and a major contributor to cancer-death worldwide. Non-structural maintenance of chromosomes (SMC) condensin I complex subunit G (NCAPG) is a subunit of condensin I and has been shown to be associated with the prognosis of cancers. This study investigated the functional role of NCAPG in CRC and its mechanism. Methods: Messenger RNA (mRNA) and protein expressions of NCAPG and chromobox protein homolog 3 (CBX3) were determined by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot. The proliferation, cycle, and apoptosis of HCT116 cells were analyzed by Cell Counting Kit-8 (CCK-8), flow cytometry, and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay. RT-qPCR and western blot were used to determine the transfection efficacy of short hairpin (sh)-NCAPG and sh-CBX3. Western blot was used to explore cycle-, apoptosis-, and Wnt/ß-catenin signaling-related proteins, and the activity of NCAPG promoter was evaluated using a luciferase report assay. The expressions of cleaved caspase9 and cleaved caspase3 were assessed by colorimetric caspase activity assay. Results: The results showed that NCAPG expression was elevated in CRC cells. After transfection with sh-NCAPG, NCAPG expression was reduced. It was also discovered that NCAPG knockdown suppressed proliferation and the cell cycle but induced apoptosis in HCT116 cells. The Human Transcription Factor Database (HumanTFDB; http://bioinfo.life.hust.edu.cn/HumanTFDB#!/) predicted the binding sites of CBX3 and NCAPG promoters. Meanwhile, the Encyclopedia of RNA Interactomes (ENCORI) database (https://starbase.sysu.edu.cn/) revealed that CBX3 was positively correlated with NCAPG. Our results showed that NCAPG was transcriptionally regulated by CBX3. Additionally, Wnt/ß-catenin signaling was discovered to be activated by CBX3 overexpression. Further experiments showed that NCAPG transcriptionally regulated by CBX3 activated Wnt/ß-catenin signaling to regulate the proliferation, cell cycle, and apoptosis of HCT116 cells. Conclusions: Collectively, the results of our study indicated that NCAPG was transcriptionally regulated by CBX3 and activated the Wnt/ß-catenin signaling pathway to facilitate the progression of CRC.

LINC01006 regulates the proliferation, migration and invasion of hepatocellular carcinoma cells through regulating miR-433-3p/CBX3 axis.

INTRODUCTION AND OBJECTIVES: LINC01006 has been verified to be correlated with several cancer types, whereas its biological function in hepatocellular carcinoma (HCC) is still elusive. This study aimed to elucidate the specific regulatory mechanism of LINC01006 in the tumorigenesis of HCC. MATERIALS AND METHODS: The expression of LINC01006, miR-433-3p and CBX3 in HCC tissues and cells was assessed by qRT-PCR or Western blot. MTT, wound-healing, and transwell assays were used to evaluate the effects of LINC01006 on cell viability, migration, and invasion in vitro. A mouse xenograft model was established for in vivo assays. The relations among LINC01006, miR-433-3p, and CBX3 were analyzed by MS2-RNA immunoprecipitation (RIP) and Dual-luciferase reporter (DLR) assays. RESULTS: The expression of LINC01006 was up-regulated in HCC tissues and cells. LINC01006 knockdown inhibited the viability, wound healing rate, and invasive cell number of HeP3B and SK-HeP-1 cells, and decreased the tumor volume and weight in a mouse xenograft model. MiR-433-3p was a target of LINC01006, and LINC01006 overexpression inhibited the viability, wound healing rate, and invasive cell number of HeP3B and SK-HeP-1 cells. In addition, CBX3 was a target of miR-433-3p, which was negatively regulated by miR-433-3p. CBX3 overexpression and miR-433-3p inhibition reversed the inhibiting effects of LINC01006 knockdown on the viability, migration, and invasion of HeP3B cells. CONCLUSIONS: Silencing of LINC01006 inhibited the viability, migration, and invasion of HCC cells through regulating miR-433-3p/CBX3 axis.

microRNA-377 acts as a suppressor in esophageal squamous cell carcinoma through CBX3-dependent P53/P21 pathway.

Stem cells play pivotal roles in esophageal squamous cell carcinoma (ESCC) recurrence and metastasis. The self-renewal ability of stem cells was associated with specific microRNAs (miRs). Herein, we identified the effects of miR-377 on ESCC stem cell activities. First, the expression of miR-377 in ESCC and adjacent normal tissues was determined. The relationship between miR-377 and chromobox protein homolog 3 (CBX3) was assessed by a dual-luciferase reporter gene assay. miR-377 was overexpressed or inhibited in ESCC stem cells to explore its role in ESCC. To further investigate the mechanism of miR-377 in ESCC, cells were introduced with short hairpin RNA against CBX3 or pifithrin-α (inhibitor of P53 pathway). Besides, the expression of P21, P53, CD133, CD13, Nanog, sex determining region Y-Box 2 (Sox2), and octamer-binding transcription factor 4 (Oct4), cell sphere formation, colony formation, and proliferation were evaluated respectively. Finally, limiting dilution assay in vivo and tumor xenograft in nude mice were conducted to confirm the roles of miR-377 in vivo. miR-377 was poorly expressed in ESCC. Overexpression of miR-377 could suppress the stem-like trait of ESCC as well as the tumor growth in vivo. miR-377 targeted CBX3 to activate the P53/P21 pathway. Besides, the expression of stem-like markers including CD133, CD13, Oct4, Sox2, and Nanog was decreased, and the abilities of cell sphere formation, colony formation, proliferation, and tumorigenicity were significantly reduced by overexpressing miR-377 or silencing CBX3. The results were reversed after inactivating the P53/P21 pathway. In summary, upregulation of miR-377 inhibits the self-renewal of ESCC stem cells by inhibiting CBX3 expression and promoting activation of the P53/P21 pathway.

PDE4B Induces Epithelial-to-Mesenchymal Transition in Bladder Cancer Cells and Is Transcriptionally Suppressed by CBX7.

Urinary bladder cancer (UBC) is a common malignant tumor with high incidence. Advances in the diagnosis and treatment of this disease demand the identification of novel therapeutic targets. Multiple studies demonstrated that PDE4B level was upregulated in malignancies and high PDE4B expression was correlated with poor outcomes. Herein, we identified that PDE4B was a potential therapeutic target in UBC. We confirmed that PDE4B expression was correlated with aggressive clinicopathological characteristics and unfavorable prognosis. Functional studies demonstrated that ectopic expression of PDE4B promoted UBC cells proliferation, migration and invasion, whereas PDE4B depletion suppressed cancer cell aggressiveness. We also identified CBX7 as a regulator of PDE4B to suppress the expression of PDE4B at the transcription level in a PRC1-dependent manner. Moreover, our results indicated that PDE4B induced epithelial-to-mesenchymal transition (EMT) in UBC cells via ß-catenin pathway, whereas inhibition of PDE4B by its small molecule inhibitor, rolipram, effectively reversed the PDE4B overexpression-induced effects. To sum up, our results indicated that PDE4B acts as an oncogene by promoting UBC cell migration and invasion via ß-catenin/EMT pathway.

Deubiquitinating Enzyme USP29 Regulates the Protein Stability of CBX6 / 中国生物化学与分子生物学报

Polycomb group (PcG) proteins are transcriptional repressors that control cell fate and the development of embryo, and they elicit function mainly in the form of polycomb repressive complex (PRC). Chromobox protein homolog 6 (CBX6) is one of the core protein subunits of PRC1, which plays an important role in gene expression regulation, cell renewal and differentiation, tumorigenesis and development, and stem cell maintenance. In this study, CBX6 was found to be degraded through a ubiquitin-proteasome dependent pathway. Then the gene expression library containing 92 deubiquitinating enzymes (DUB) was used to screen DUB targeting CBX6 and results found that ubiquitin-specific protease 29 (USP29) could obviously stabilize CBX6 protein level and extend its half-life (P < 0.05). Immunoprecipitation experiments found that CBX6 interacted with USP29 through its C-terminal domains; Further studies found that USP29 regulated the protein stability of CBX6 by deubiquitination in an enzymatic-activity dependent manner. Cell proliferation assay also found that USP29 inhibited the proliferation of MCF7 cells (P<0.0001). Taken together, through screening, this study found that USP29 could stabilize CBX6 protein level through deubiquitinating CBX6 and inhibit the cell proliferation of MCF7.

[The expression and significance of chromobox protein homolog 2 in breast cancer].

Objective: To study the relationship between the expression of Chromobox protein homolog (CBX) mRNA and the clinicopathological prognosis of breast cancer, and to investigate the possibility of Chromobox protein homolog 2 as a therapeutic target for breast cancer. Methods: First, we analyzed the mRNA expression of 8 CBX family genes by METABRIC database, and investigated the relationship between the expression of CBX2 mRNA and the clinicopathological parameters of breast cancer. Then we explored its relationship with prognosis. CBX2 siRNA was used to treat breast cancer cell lines with high expression of CBX2(SUM159 and SUM1315). The effects of knockdown of CBX20 on mRNA and protein expression and cell proliferation were observed. Results: According to the analysis of METABRIC database, among the 8 CBX genes, the most obvious increase in mRNA expression was CBX2, and 22.47% (445/1 980) of the patients showed high mRNA expression. The high expression of CBX2 was closely related to tumor histological grade and the molecular type of breast cancer (P<0.001). Compared with the low-expression group of CBX2 mRNA, the proportion of HER2 breast cancer (28.1% vs 7.5%) and Basal-like (44.5% vs 8.5%) in the high-expression group were both higher. Patients with high CBX2 expression had significantly shorter disease-free survival (DFS) and overall survival (OS). The knockdown of CBX2 by siRNA inhibited the proliferation of breast cancer cells. Conclusion: CBX2 is closely related to the prognosis of breast cancer and may be a target for breast cancer treatment.

Correlations between chromobox homolog 8 and key factors of epithelial-mesenchymal transition in hepatocellular carcinoma.

Background: Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide, especially in China, with high metastasis and poor prognosis. Recently, as the core component of the polycomb repressive complexes 1 (PRC1), chromobox protein homolog 8 (CBX8) is considered as an oncogene and prognostic marker in HCC. Methods: A tissue microarray of 166 paired HCC and adjacent non-tumor samples were collected to identify the relationship between CBX8 and epithelial mesenchymal transition (EMT) associated proteins by Spearman correlation analysis. Knock-down of CBX8 in HCC cells was conducted to detect the biologic functions of CBX8 in HCC metastasis. Results: We found out that CBX8 was over-expressed in HCC and its expression was closely related to the metastasis of HCC patients. In addition, knock-down of CBX8 was found to inhibit the invasion and migration ability of HCC cells. Moreover, there was a significant relationship between expression of CBX8 and EMT associated proteins both in HCC cells and tumor tissues. Conclusions: Our results indicate that CBX8 promotes metastasis of HCC by inducing EMT process.

Polycomb group expression signatures in the malignant progression of gliomas.

Polycomb group (PcG) proteins form at least two key complexes, namely polycomb repressive complex 1 and polycomb repressive complex 2. These complexes are involved in the progression of various cancers. Systematic research has not been conducted on the aberrant expression of PcG members in gliomas. Using the Chinese Glioma Genome Atlas data set, PcG expression patterns between normal brain tissues and glioma samples were analyzed, and a PcG-based classifier was then developed using BRB Cox regression and risk-score model. These results were validated in an independent GSE16011 set. A total of six PcGs [chromobox protein homolog (CBX) 6, CBX7, PHD finger protein 1, enhancer of zeste homolog 2 (EZH2), DNA (cytosine-5-)-methyltransferase 3ß (DNMT3B) and polyhomeotic-like protein 2] were identified to be associated with glioma grade. Survival analysis then revealed a five-PcG gene signature one protective gene (enhancer of zeste homolog 1) and four risky genes (EZH2, PHD finger protein 19, DNMT3A and DNMT3B), which may identify patients with high risk of poor prognosis of glioma. Multivariate Cox analysis indicated that the five-PcG signature was an independent prognostic biomarker. These findings indicated that a novel prognostic classifier, five-PcG signature, served as an independent prognostic marker for patients with glioma.

Research progress of CBX protein and tumor / 实用肿瘤学杂志

CBX protein(chromoboxin protein homolog)is an important member of PcG(polycombe group proteins)family protein,and PcG protein is an epigenetic regulatory complex that exists in the form of polymeric transcriptional inhibitory complexes PRCs.PcG protein can modify the target gene to transcript chromatin and plays an important role in stem cell differentiation and tumorigenesis and metastasis.The CBX protein family is an important member of the classic PRC1.Recent studies have focused on the different functions of CBX in stem cells,further demonstrating the composition and function of CBX.From more evidence,CBX plays an important role in tumorigenesis and development.This review summarizes the current advances in the study of CBX family members in tumors.

Insulin-Like Growth Factor-1 Modulates Polycomb Cbx8 Expression and Inhibits Colon Cancer Cell Apoptosis.

Colon cancer is one of the leading causes of death in human beings. The pathogenesis of colon cancer is unclear. Recent reports indicate that Chromobox protein homolog 8 (Cbx8) and insulin-like growth factor-1 (IGF1) are associated with the pathogenesis of cancer. This study aims to investigate the role of Cbx8 and IGF1 in facilitating colon cancer cell proliferation. In this study, human colon cancer cell line, HCT116 cells, was cultured using an in vitro study model. The expression of Cbx8 and IGF1R (IGF1 receptor) in HCT116 cells was observed with approaches of real-time RT-PCR, Western blotting, gene silencing, and gene overexpression. The results showed that HCT116 cells express both Cbx8 and IGF1R. Exposure of HCT116 cells to IGF1 increased the expression of Cbx8. Knockdown of Cbx8 induced HCT116 cell apoptosis. Overexpression of Cbx8 induced HCT116 cell proliferation. We conclude that IGF1 can promote the colon cancer cell line, HCT116 cell, proliferation via promoting Cbx8 expression.