Bromodomain-containing Protein 7 Expression Research Articles

TRIM28 promotes tumor growth and metastasis in breast cancer by targeting the BRD7 protein for ubiquitination and degradation.

Bromodomain-containing protein 7 (BRD7) is downregulated and functions as a tumor suppressor in many types of cancers including breast cancer, and the dysregulation of BRD7 expression is closely related to the development and progression of breast cancer. Whereas little attention has been focused on the regulation of BRD7 protein levels in breast cancer, which needs to be further elucidated. The protein stability of BRD7 in breast cancer cells and BRD7 protein level in breast cancer tissues was examined by Western Blotting. The potential E3 ubiquitin ligase proteins that interact with the BRD7 was screened by coimmunoprecipitation combined with mass spectrometry analysis in MDA-MB-231 cells. We proved the interaction between BRD7 and tripartite motif containing 28 (TRIM28) through Co-Immunoprecipitation (Co-IP) and immunofluorescence assays. Co-IP and ubiquitination assay were used to explore the specific binding domain between BRD7 and TRIM28 and the ubiquitination site of BRD7. The effects of TRIM28 on the BRD7 protein stability and ubiquitination level was investigated by qPCR, Western Blot and Co-IP assay. CCK-8 and clone formation assays were carried out to assess the effect of TRIM28 on proliferation ability of breast cancer ells. Transwell assay and wound healing assay were used to investigate the effect of TRIM28 on breast cancer cell invasion and migration. Flow cytometry was used to detect the effect of TRIM28 on cell cycle and apoptosis of breast cancer cells. In addition, we confirmed effect of TRIM28 on tumor growth and metastasis by xenograft and metastatic mouse models. We designed some recovery assays to explore the role of recovery BRD7 in TRIM28-mediated promotion of malignant progression of breast cancer in vivo and in vitro. Finally, the clinical significance of TRIM28 and BRD7 was proved by immunohistochemistry. In this study, we demonstrated that BRD7 was an unstable protein and might be regulated by ubiquitination in breast cancer; furthermore, we found that the Coiled-Coil region of TRIM28 could directly bind to N-terminal of BRD7, and TRIM28 mediates BRD7 ubiquitination and degradation dependent on K21 by acting as a potential E3 ubiquitin ligase. Moreover, TRIM28 promoted cell proliferation, migration, invasion, xenograft tumor growth and metastasis, thus playing an oncogenic role in breast cancer. Furthermore, the restoration of BRD7 expression in breast cancer significantly reversed the promotional effects of TRIM28 on malignant progression both in vitro and in vivo. In addition, TRIM28 was highly expressed in the biopsy tissues of breast cancer, and its expression was negatively correlated with BRD7 expression and positively correlated with TNM stage and poor prognosis of BC patients. Our findings provide a novel mechanism by which TRIM28 significantly facilitates BRD7 ubiquitination and degradation, thus promoting breast cancer malignant progression. Targeting the TRIM28/BRD7 axis might be a novel potential strategy for the clinical diagnosis and treatment of breast cancer.

Identification of BRD7 by whole-exome sequencing as a predictor for intermediate-stage hepatocellular carcinoma in patients undergoing TACE.

In the present study, we aimed to identify potential predictors of intermediate-stage hepatocellular carcinoma (HCC) using whole-exome sequencing (WES) in patients undergoing transarterial chemoembolization (TACE). In A total of 51 patients, newly diagnosed with intermediate-stage HCC between January 2013 and December 2020, were enrolled. Prior to treatment, histological samples were collected for western blotting and immunohistochemistry. The predictive roles of clinical indicators and genes in patient prognosis were analyzed using univariate and multivariate analyses. Finally, the correlation between imaging features and gene signatures was examined. Using WES, we identified that bromodomain-containing protein 7 (BRD7) was significantly mutated in patients with different TACE responses. No significant difference in BRD7 expression was observed between patients with and without BRD7 mutations. HCC tumors exhibited higher BRD7 than normal liver tissues. Multivariate analysis revealed that alpha-fetoprotein (AFP), BRD7 expression, and BRD7 mutations were independent risk factors for progression-free survival (PFS). In addition, Child-Pugh class, BRD7 expression, and BRD7 mutations were independent risk factors for overall survival (OS). Patients with wild-type BRD7 and high BRD7 expression had worse PFS and OS, whereas those with mutated BRD7 and low BRD7 expression exhibited the best PFS and OS. The Kruskal-Wallis test revealed that wash-in enhancement on computed tomography might be an independent risk factor for high BRD7 expression. BRD7 expression may be an independent risk factor for prognosis in patients with HCC undergoing TACE. Imaging features such as wash-in enhancement are closely related to BRD7 expression.

Upregulation of BRD7 protects podocytes against high glucose-induced apoptosis by enhancing Nrf2 in a GSK-3β-dependent manner

Bromodomain-containing protein 7 (BRD7) is linked to a variety of pathophysiological conditions. However, it is still unclear whether BRD7 is connected with diabetic nephropathy. This research explored the relevance of BRD7 in diabetic nephropathy using high glucose (HG)-stimulated podocytes in vitro. BRD7 expression in podocytes was decreased after HG stimulation. Podocytes with forced BRD7 expression were protected from HG-induced apoptosis, oxidative stress and inflammation. Further data revealed that forced expression of BRD7 led to enhanced nuclear factor erythroid-2-related factor 2 (Nrf2) activation in HG-stimulated podocytes, associated with the upregulation of glycogen synthase kinase-3β (GSK-3β) phosphorylation. Reactivation of GSK-3β diminished BRD7-elicited Nrf2 activation. In addition, restraining of Nrf2 diminished the BRD7 overexpression-induced beneficial effects on HG-induced podocyte damage. Taken together, these data document that BRD7 defends against HG-induced podocyte damage by enhancing Nrf2 via regulation of GSK-3β. Our work indicates that the BRD7/GSK-3β/Nrf2 axis may play a key role in mediating podocyte injury in diabetic nephropathy.

Bromodomain-containing protein 7 contributes to myocardial infarction-induced myocardial injury through activating Wnt/β-catenin signaling.

Myocardial infarction (MI) is one of the most common cardiovascular diseases, inducing severe myocardial injury and leading to high mortality. Bromodomain-containing protein 7 (BRD7), a member of bromodomain-containing protein family, is involved in multiple cellular processes, such as cell cycle, transcriptional regulation, and chromatin remodeling, but the functions of BRD7 in regulating MI-associated myocardial injury are still obscure. In this work, we investigated the effect of BRD7 on MI-induced myocardial injury in vitro and in vivo. The MI model was established by ligating the left anterior descending coronary artery (LAD) of rats which were then injected with BRD7 short hairpin RNA (shRNA). The rat H9C2 cardiomyocytes were treated with hypoxia and injected with BRD7 shRNA. The expression of BRD7 in MI rat model, and hypoxia-treated H9C2 cells was detected by quantitative polymerase chain reaction (qPCR), western blot, and immunohistochemical staining. The effect of BRD7 was analyzed using western blot, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, echocardiography, and flow cytometry analysis. The expressions of Wnt/β-catenin signaling relative proteins were determined by western blot. Significantly, BRD7 was highly expressed in MI patients, MI rat models, and hypoxia treated rat H9C2 cardiomyocytes. Echocardiography analysis demonstrated that the left ventricular ejection fraction (LVEF) and left ventricular fraction shortening (LVFS) were repressed in the MI rats relative to sham group rats, while the silencing of BRD7 rescued the dysfunction in the model. We also found that BRD7 silencing reduced cardiomyocyte apoptosis in both MI rats and H9C2 cells under the treatment of hypoxia. BRD7 silencing inhibited the activation of Wnt/β-catenin signaling in H9C2 cells under the treatment of hypoxia. Moreover, Wnt agonist BML294 reversed the anti-apoptosis effect of BRD7 silencing in hypoxia-induced H9C2 cells. Collectively, we concluded that BRD7 contributed to MI-induced myocardial injury through activating Wnt/β-catenin signaling. Targeting BRD7 may become a promising therapeutic strategy for the treatment of MI-induced myocardial injury.

Bromodomain-containing protein 7 regulates matrix metabolism and apoptosis in human nucleus pulposus cells through the BRD7-PI3K-YAP1 signaling axis

Intervertebral disc degeneration (IDD) results from dysregulated metabolism of the extracellular matrix of the nucleus pulposus (NP) and involves the participation of inflammatory factors such as TNF-α. Bromodomain-containing protein 7 (BRD7) shows considerable potential for anti-inflammatory applications. Herein, we investigated the role of BRD7 in IDD. The immunohistochemistry results demonstrated decreased BRD7 expression in severely degenerated human NP tissues compared to those showing mild degeneration. Lentiviruses and adenoviruses were used to knock down or overexpress BRD7 and YAP1, respectively. Our results revealed that BRD7 knockdown promoted matrix degradation and suppressed PI3K and YAP1 expression, while BRD7 overexpression alleviated matrix degradation and promoted YAP1 and PI3K expression. In addition, PI3K inhibition augmented matrix degradation, enhanced apoptosis, and reduced YAP1 expression, whereas YAP1 overexpression promoted matrix synthesis, suppressed apoptosis and promoted PI3K expression. Besides, BRD7 overexpression reversed the reductions in sulfated glycosaminoglycan levels induced by TNF-α, but this effect was blocked by PI3K or YAP1 inhibitors. Moreover, YAP1 and PI3K were shown to interact through coimmunoprecipitation analysis. In summary, our results demonstrate that BRD7 can regulate matrix metabolism and apoptosis in human NP cells through the BRD7-PI3K-YAP1 signaling axis. This study might provide new insights into the prevention and treatment of IDD.

BRD7 inhibits tumor progression by positively regulating the p53 pathway in hepatocellular carcinoma.

Background: Bromodomain-containing protein 7 (BRD7) is identified as a transcriptional regulator and plays an important role in the development and progression of various tumors. Our previous study demonstrated that BRD7 acts as a potential tumor suppressor in hepatocellular carcinoma (HCC). However, the specific molecular mechanism underlying the BRD7-mediated inhibition of HCC progression remains poorly understood.Methods: We performed ChIP-seq analysis to investigate the gene network mediated by BRD7. Immunohistochemical analysis was performed to analyze potential associations between the p53 and BRD7 expression and the effect of their overexpression on disease pathogenesis and outcome. In addition, we performed biological function experiments to determine the effect of BRD7 and p53 on these functions that are central to tumorigenesis. Finally, we employed a BALB/c model for execution of xenograft transplants to examine the effect of either overexpressing or under-expressing BRD7 and p53 on tumor growth in mice injected with cells.Results: Our results suggested that BRD7 regulates the p53 pathway. Specifically, BRD7 was demonstrated to upregulate the transcription level of p53 by directly binding to the upstream regulatory region of the p53 transcriptional initiation site, thereby enhancing its promoter activity. Moreover, immunohistochemical analysis showed that wild-type p53 (WTp53) expression is positively associated with BRD7 expression and survival of patients with HCC. Additionally,changes of p53 expression could affect the tumor suppressive role of BRD7 on HCC cell proliferation, migration/invasion, cell-cycle, and tumor growth in vitro and in vivo. Furthermore, changes of BRD7 expression in HCC cells significantly altered the expression of p53 signal-related molecules such as p21, Bax, Bcl2, and cyclin D1, indicating that BRD7 may positively regulate activation of the p53 pathway.Conclusions: Collectively, our results indicated that BRD7 exerts anti-tumor effects in HCC through transcriptionally activating p53 pathway. These critical roles of BRD7may provide some promising diagnostic and therapeutic targets for HCC.

The BRD7-P53-SLC25A28 axis regulates ferroptosis in hepatic stellate cells

Ferroptosis is a recently discovered form of programmed cell death, but its regulatory mechanisms are not fully understood. In the current study, we reported that the BRD7-P53-SLC25A28 axis played a crucial role in regulating ferroptosis in hepatic stellate cells (HSCs). Upon exposure to ferroptosis inducers, bromodomain-containing protein 7 (BRD7) protein expression was remarkably increased through the inhibition of the ubiquitin-proteasome pathway. CRISPR/Cas9-mediated BRD7 knockout conferred resistance to HSC ferroptosis, whereas specific BRD7 plasmid-mediated BRD7 overexpression facilitated HSC ferroptosis. Interestingly, the elevated BRD7 expression exhibited to promote p53 mitochondrial translocation via direct binding with p53 N-terminal transactivation domain (TAD), which may be the underlying mechanisms for BRD7-enhanced HSC ferroptosis. Site-directed mutations of serine 392 completely blocked the binding of BRD7 to p53, and, in turn, prevented p53 mitochondrial translocation and HSC ferroptosis. Importantly, mitochondrial p53 interacted with solute carrier family 25 member 28 (SLC25A28) to form complex and enhanced the activity of SLC25A28, which could lead to the abnormal accumulation of redox-active iron and hyperfunction of electron transfer chain (ETC). SLC25A28 knockdown impaired BRD7-or p53-mediated ferroptotic events. In mice, erastin treatment ameliorated pathological damage of liver fibrosis through inducing HSC ferroptosis. HSC-specific blockade of BRD7-P53-SLC25A28 axis could abrogate erastin-induced HSC ferroptosis. Of note, we analyzed the effect of sorafenib on HSC ferroptosis in advanced fibrotic patients with hepatocellular carcinoma receiving sorafenib monotherapy. Attractively, BRD7 upregulation, p53 mitochondrial translocation, combination of SLC25A28 and p53, and ferroptosis induction occurred in primary human HSCs. Overall, these findings reveal novel signal transduction and regulatory mechanism of ferroptosis, and also suggest BRD7-P53-SLC25A28 axis as potential targets for liver fibrosis.

Expression and subcellular localization of the bromodomain-containing protein 7 is a prognostic biomarker in breast cancer

Bromodomain-containing protein 7 (BRD7) is a member of the bromodomain-containing protein family. Previous studies suggest that BRD7 is predominantly localized in the nucleus, wherein it functions as a transcriptional regulator. Several lines of evidence imply a tumour suppressor function for BRD7. However, the importance of BRD7 in the pathogenesis of breast cancer is not well understood. We have investigated the expression, CpG island methylation and subcellular localization of BRD7 in breast cancer cell lines and clinical cases and thereby assessed its prognostic significance by correlating with clinical-pathological features and time-dependent clinical outcomes. We show that nuclear exclusion of BRD7 occurs commonly in breast cancer and is strongly associated with cases expressing wild-type p53. Moreover, clinical outcomes are significantly less favourable in cases with nuclear exclusion or loss of expression than those in which there is nuclear expression of BRD7. Methylation of the CpG island of BRD7 increases in breast cancer relative to normal breast tissue, but there is not an obvious correlation between methylation and reduced expression or between methylation and clinical outcomes. Overall, our results suggest that nuclear exclusion, rather than transcriptional silencing, is a common mechanism by which the tumour suppressor function of wild-type p53 is inhibited in breast cancer, and show that BRD7 is a promising candidate biomarker in breast cancer.

Poly(ADP-ribosyl)ation of BRD7 by PARP1 confers resistance to DNA-damaging chemotherapeutic agents.

The bromodomain-containing protein 7 (BRD7) is a tumour suppressor protein with critical roles in cell cycle transition and transcriptional regulation. Whether BRD7 is regulated by post-translational modifications remains poorly understood. Here, we find that chemotherapy-induced DNA damage leads to the rapid degradation of BRD7 in various cancer cell lines. PARP-1 binds and poly(ADP)ribosylates BRD7, which enhances its ubiquitination and degradation through the PAR-binding E3 ubiquitin ligase RNF146. Moreover, the PARP1 inhibitor Olaparib significantly enhances the sensitivity of BRD7-positive cancer cells to chemotherapeutic drugs, while it has little effect on cells with low BRD7 expression. Taken together, our findings show that PARP1 induces the degradation of BRD7 resulting in cancer cell resistance to DNA-damaging agents. BRD7 might thus serve as potential biomarker in clinical trial for the prediction of synergistic effects between chemotherapeutic drugs and PARP inhibitors.

Bromodomain‑containing protein7 sensitizes breast cancer cells to paclitaxel by activating Bcl2‑antagonist/killer protein.

Our previous study demonstrated that bromodomain-containing protein 7 (BRD7) inhibits cell proliferation and tumor growth, restoring the expression of B-cell lymphoma 2 antagonist/killer (Bak) sensitized breast cancer cells to paclitaxel. However, the association between BRD7 and paclitaxel sensitization, as well as BRD7 and Bak in breast cancer remains unknown. In the present study, immunochemical staining was performed to measure the expression of BRD7 and Bak in breast cancer tissues. Cell Counting Kit-8 assay, flow cytometry and tumor xenograft procedures were performed to evaluate the biological role of BRD7 and Bak in breast cancer cells. Western blotting, reverse transcription-quantitative polymerase chain reaction, chromatin immunoprecipitation and luciferase reporter assays were also performed. BRD7 was positively correlated with Bak levels in breast cancer tissues, and the survival rate of patients with low Bak and BRD7 expression was significantly lower than that of patients with high Bak and BRD7 expression. In addition, BRD7 activated Bak promoter activity and induced Bak expression in an indirect manner. Furthermore, ectopic expression of BRD7 inhibited cell proliferation, tumor growth and sensitized cancer cells to paclitaxel, while knockdown of Bak abolished BRD7-mediated inhibitory effects on cell proliferation and paclitaxel sensitization in breast cancer cells whether in vitro and in vivo. The results demonstrated that BRD7 inhibits cell proliferation and sensitizes breast cancer cells to paclitaxel by activating Bak; they also provide promising targets for the diagnosis and treatment of breast cancer.

Clinical significance of bromodomain-containing protein 7 and its association with tumor progression in prostate cancer.

Prostate cancer (PCa) is a common malignancy in males. The current study assessed the clinical significance of bromodomain-containing protein 7 (BRD7) and its association with PCa tumor progression. Serum and tissue expression levels of BRD7 were analyzed by reverse transcription-quantitative polymerase chain reaction. Receiver operating characteristic (ROC) analysis was used to evaluate the diagnostic value of BRD7. Kaplan-Meier survival analysis and Cox regression analysis were performed to assess the prognostic performance of BRD7. The association of BRD7 with cell behavior was investigated by transfection with a pcDNA3.1-BRD7 vector. The results revealed that serum and tissue BRD7 expression levels were significantly decreased in PCa samples compared with normal controls (P<0.001). BRD7 expression was significantly associated with the pathological stage (P=0.037), lymph node metastasis (P=0.009) and TNM stage (P=0.010). An area under the ROC curve of 0.864 was obtained, with a sensitivity and specificity of 77.0 and 83.3%, respectively. Low BRD7 expression was significantly associated with a shorter survival time in both overall survival analysis (P=0.003) and cancer-specific survival analysis (P=0.029). Furthermore, BRD7 appeared to serve as an independent prognostic factor for PCa. The proliferation, migration and invasion of PCa cells were suppressed by BRD7 overexpression. In summary, downregulation of BRD7 in PCa may be involved in tumor progression and serve as an effective diagnostic and prognostic biomarker.

Abstract 2647: Bromodomain-containing protein 7 (BRD7) is a candidate tumor suppressor in breast carcinoma and prognostic biomarker

Abstract Background Breast cancer (BC) is a multifactorial disorder in which multiple genetic and epigenetic factors changes drive tumor initiation and progression. Bromodomain-containing protein 7 (BRD7) is a member of the bromodomain-containing protein family mainly localized in the nuclear compartment of the cell. BRD7 is a transcriptional co-activator for p53 modulating histone acetylation, p53 acetylation and promoter activity in p53 target genes. Previous studies show that BRD7 is down-regulated in a number of cancer types and this may correlate with clinical outcomes. However, the potential involvement of changes in BRD7 and prognostic importance in BC are poorly understood. Purpose of the study We have investigated the expression, CpG island methylation and sub-cellular localization of BRD7 in BC cell lines and clinical cases and thereby assessed its prognostic significance by correlating with clinicopathologic features and time-dependent clinical outcomes. Materials and methods BRD7 expression was analysed by qRT-PCR and IHC in 13 BC cancer cell lines. Expression was also assessed by IHC in 50 cases of primary breast cancer and 14 paired metastatic lesions. CpG island methylation was determined quantitatively by pyrosequencing. BC cases were divided for nuclear and non-nuclear BRD7 antigen localization and then stratified for high and low BRD7 expression. The effects of BRD7 expression and BC clinical characteristics data on OS and PFS were evaluated using univariate and multivariate Cox regression analyses. Results BRD7 was expressed at levels similar to normal breast epithelium and the CpG island unmethylated in all 13 cell lines. Methylation analysis was successful in 42 FFPE BC samples collected, with 26,2% of them methylated (11/42). IHC analysis on primary tissues revealed that BDR7 is mainly localized in the nucleus (34/50: 68%). Patients with BRD7 nuclear localization (N=34) showed smaller tumors (p=0.012), a longer OS (p=0.002) and a lower relapse rate (p=0.03). Moreover, nuclear BRD7 expression is associated with wild-type TP53 (p=0.04) and unmethylated BRD7 (p=0.04), compared to the non-nuclear cases (N=16). No difference was seen in nodal status, grading, clinical stage, histological type, ER, PR, HER2 and Ki-67 expression. Patients (N=12) showing both nuclear localization and high BRD7 expression presented the smallest tumors (10/12 = 83%) and both a longer OS (p=0,005) and PFS (p=0,001). Among the 4/14 patients with nuclear localization in their primary tumors, 3 (75%) presented a diffuse or negative BRD7 in the paired metastasis. Conclusion BRD7 is a strong candidate for breast cancer tumor suppressor and prognostic biomarker. Citation Format: Cristiana Lo Nigro, Daniela Vivenza, Ornella Garrone, Rodolfo Brizio, Fiamma Mantovani, Giannino Del Sal, Marco Carlo Merlano, Tim Crook. Bromodomain-containing protein 7 (BRD7) is a candidate tumor suppressor in breast carcinoma and prognostic biomarker [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2647.

BRD7 mediates hyperglycaemia-induced myocardial apoptosis via endoplasmic reticulum stress signalling pathway.

Bromodomain‐containing protein 7 (BRD7) is a tumour suppressor that is known to regulate many pathological processes including cell growth, apoptosis and cell cycle. Endoplasmic reticulum (ER) stress‐induced apoptosis plays a key role in diabetic cardiomyopathy (DCM). However, the molecular mechanism of hyperglycaemia‐induced myocardial apoptosis is still unclear. We intended to determine the role of BRD7 in high glucose (HG)‐induced apoptosis of cardiomyocytes. In vivo, we established a type 1 diabetic rat model by injecting a high‐dose streptozotocin (STZ), and lentivirus‐mediated short hairpin RNA (shRNA) was used to inhibit BRD7 expression. Rats with DCM exhibited severe myocardial remodelling, fibrosis, left ventricular dysfunction and myocardial apoptosis. The expression of BRD7 was up‐regulated in the heart of diabetic rats, and inhibition of BRD7 had beneficial effects against diabetes‐induced heart damage. In vitro, H9c2 cardiomyoblasts was used to investigate the mechanism of BRD7 in HG‐induced apoptosis. Treating H9c2 cardiomyoblasts with HG elevated the level of BRD7 via activation of extracellular signal‐regulated kinase 1/2 (ERK1/2) and increased ER stress‐induced apoptosis by detecting spliced/active X‐box binding protein 1 (XBP‐1s) and C/EBP homologous protein (CHOP). Furthermore, down‐regulation of BRD7 attenuated HG‐induced expression of CHOP via inhibiting nuclear translocation of XBP‐1s without affecting the total expression of XBP‐1s. In conclusion, inhibition of BRD7 appeared to protect against hyperglycaemia‐induced cardiomyocyte apoptosis by inhibiting ER stress signalling pathway.

Tumor suppressor bromodomain-containing protein 7 cooperates with Smads to promote transforming growth factor-β responses.

Smad proteins are central mediators in the canonical transforming growth factor-β (TGF-β) signaling pathway in mammalian cells. We report here that bromodomain-containing protein 7 (BRD7) functions as a novel transcription coactivator for Smads in TGF-β signaling. BRD7 forms a TGF-β inducible complex with Smad3/4 through its N-terminal Smad-binding domain. BRD7 simultaneously binds to acetylated histones to promote Smad-chromatin association, and associates with histone acetyltransferase p300 to enhance Smad transcriptional activity. Ectopic expression of BRD7, but not its mutants defective in Smad binding, enhances TGF-β transcriptional, tumor suppressing and epithelial-mesenchymal transition (EMT) responses. Conversely, depletion of BRD7 inhibits TGF-β responses. Thus, our study provides compelling evidence for a new function of BRD7 in fine-tuning TGF-β physiological responses.

Bromodomain-containing protein 7 (BRD7) as a potential tumor suppressor in hepatocellular carcinoma.

Bromodomain-containing protein 7 (BRD7) is a subunit of the PBAF complex, which functions as a transcriptional cofactor for the tumor suppressor protein p53. Down-regulation of BRD7 has been demonstrated in multiple types of cancer. This study aimed to investigate BRD7 expression and its tumor suppressive effect in hepatocellular carcinoma (HCC). The expression of BRD7 was examined in clinical specimens of primary HCC and in HCC cell lines through real-time quantitative PCR, western blot and immunohistochemistry. The prognostic value of BRD7 expression and its correlation with the clinicopathological features of HCC patients were statistically analyzed. The effect of BRD7 on the tumorigenicity of HCC was also examined using proliferation and colony-formation assays, cell-cycle assays, migration and cell-invasion assays, and xenograft nude mouse models. BRD7 was down-regulated in tumor tissues and HCC cell lines. BRD7 protein expression was strongly associated with clinical stage and tumor size. Kaplan-Meier survival curves revealed higher survival rates in patients with higher BRD7 expression levels compared to those with lower BRD7 levels. A multivariate analysis indicated that BRD7 expression was an independent prognostic marker. The re-introduction of BRD7 expression significantly inhibited proliferation, colony formation, migration and invasion and led to cell cycle arrest in HCC cells in vitro. Furthermore, experiments in mice suggested that BRD7 overexpression suppresses HCC tumorigenicity in vivo. In conclusions, our data indicated that BRD7 may serve as a tumor suppressor in HCC and may be a novel molecular target for the treatment of HCC.

MicroRNA-410 promotes cell proliferation by targeting BRD7 in non-small cell lung cancer

miR-410 acts as an oncogene or tumor suppressor gene in some malignancies. However, its role in NSCLC is still unknown. In this study, we showed that the expression of miR-410 was up-regulated in both human NSCLC tissues and cells. Overexpression of miR-410 promoted cell proliferation, migration, and invasion of NSCLC. In addition, bromodomain-containing protein 7 (BRD7) was a direct target of miR-410. MiR-410-mediated downregulation of BRD7 led to increase Akt phosphorylation. Inhibition of Akt phosphorylation can rescue the effect of miR-410 on NSCLC cell. The expression of BRD7 was downregulated in NSCLC and was inversely expressed with miR-410 in NSCLC. Our data provided new knowledge regarding the role of miR-410 in the lung cancer progression.

Up-Regulation of MiR-300 Promotes Proliferation and Invasion of Osteosarcoma by Targeting BRD7.

Increasing reports suggest that deregulated microRNAs (miRNAs) might provide novel therapeutic targets for cancers. However, the expression and function of miR-300 in osteosarcoma is still unknown. In our study, we found that the expression of miR-300 was up-regulated in osteosarcoma tissues and cells compared with paired adjacent non-tumor bone tissues and osteoblastic cells using RT-qPCR. The enforced expression of miR-300 could promote cell proliferation, invasion and epithelial-mesenchymal transition (EMT). Moreover, we identified that bromodomain-containing protein 7 (BRD7), a new tumor suppressor gene, was a direct target of miR-300. Ectopic expression of BRD7 could significantly inhibit miR-300-promoted proliferation, invasion and EMT. Therefore, our results identify an important role for miR-300 in osteosarcoma through regulating BRD7 expression.

BRD7, a Tumor Suppressor, Interacts with p85α and Regulates PI3K Activity

Phosphoinositide 3-kinase (PI3K) activity is important for regulating cell growth, survival, and motility. We report here the identification of bromodomain-containing protein 7 (BRD7) as a p85α-interacting protein that negatively regulates PI3K signaling. BRD7 binds to the inter-SH2 (iSH2) domain of p85 through an evolutionarily conserved region located at the C terminus of BRD7. Via this interaction, BRD7 facilitates nuclear translocation of p85α. The BRD7-dependent depletion of p85 from the cytosol impairs formation of p85/p110 complexes in the cytosol, leading to a decrease in p110 proteins and in PI3K pathway signaling. In contrast, silencing of endogenous BRD7 expression by RNAi increases the steady-state level of p110 proteins and enhances Akt phosphorylation after stimulation. These data suggest that BRD7 and p110 compete for the interaction to p85. The unbound p110 protein is unstable, leading to the attenuation of PI3K activity, which suggests how BRD7 could function as a tumor suppressor.

Tumor Suppressive Effects of Bromodomain-Containing Protein 7 (BRD7) in Epithelial Ovarian Carcinoma

Bromodomain-containing protein 7 (BRD7), which is a subunit of SWI/SNF complex, has been recently suggested as a novel tumor suppressor in several cancers. In this study, we investigated the tumor suppressive effect of BRD7 in epithelial ovarian cancer. We analyzed the expression of BRD7 in human ovarian tissues with real-time PCR. To investigate the functional role of BRD7, we transfected ovarian cancer cells (A2780 and SKOV3) with BRD7 plasmid and checked the cell viability, apoptosis, and invasion. The activities of BRD7 in the signaling pathways associated with carcinogenesis were also tested. In addition, we used the orthotopic mouse model for ovarian cancer to evaluate tumor growth-inhibiting effect by administration of BRD7 plasmid. The BRD7 expression was downregulated in the ovarian cancer tissues compared with normal (P < 0.05), high-grade serous cancer exhibited significantly decreased expression of BRD7 compared with low-grade (P < 0.01) serous cancer. Transfection of BRD7 plasmid to A2780 (p53-wild) or SKOV3 (p53-null) ovarian cancer cells showed the tumor suppressive effects assessed by cell viability, apoptosis, and invasion assay and especially significantly decreased tumor weight in orthotopic mouse model (A2780). Moreover, we found that tumor suppressive effects of BRD7 are independent to the presence of p53 activity in ovarian cancer cells. BRD7 negatively regulated β-catenin pathway, resulting in decreased its accumulation in the nucleus. These results suggested that BRD7 acts as a tumor suppressor in epithelial ovarian cancers independently of p53 activity, via negative regulation of β-catenin pathway.

Expression and clinical significance of bromodomain-containing protein 7 in non-small cell lung cancer

背景与目的溴区包含蛋白7（bromodomain-containing protein 7, BRD7）基因属于bromodomain家族成员，该家族的大多数成员与上皮类肿瘤的发生密切相关。本研究旨在探讨BRD7在非小细胞肺癌（non-small cell lung cancer, NSCLC）中的表达及其临床意义。方法采用免疫组化法检测101例NSCLC癌组织及其33例正常肺组织中BRD7的表达情况。结果BRD7在NSCLC组织中的阳性表达率明显高于正常肺组织；BRD7在淋巴结转移组阳性表达率高于无淋巴结转移组；BRD7的阳性表达率随着TNM分期的升高而升高。BRD7的阳性表达与患者年龄、性别、吸烟情况、病理类型、分化程度无关（P>0.05）。结论BRD7在NSCLC中有较高的表达率，除了与淋巴结转移有关外，还与TNM分期有关，提示BRD7可能与肺癌的发生、发展和转移有关。