648

BMI1

The polycomb group protein B lymphoma Mo-MLV insertion region 1 homolog (Bmi-1) is dysregulated in various cancers, and its upregulation strongly correlates with an invasive phenotype and poor prognosis in patients with nasopharyngeal carcinomas. However, the underlying mechanism of Bmi-1-mediated invasiveness remains unknown. In the current study, we found that upregulation of Bmi-1 induced epithelial-mesenchymal transition (EMT) and enhanced the motility and invasiveness of human nasopharyngeal epithelial cells, whereas silencing endogenous Bmi-1 expression reversed EMT and reduced motility. Furthermore, upregulation of Bmi-1 led to the stabilization of Snail, a transcriptional repressor associated with EMT, via modulation of PI3K/Akt/GSK-3beta signaling. Chromatin immunoprecipitation assays revealed that Bmi-1 transcriptionally downregulated expression of the tumor suppressor PTEN in tumor cells through direct association with the PTEN locus. This in vitro analysis was consistent with the statistical inverse correlation detected between Bmi-1 and PTEN expression in a cohort of human nasopharyngeal carcinoma biopsies. Moreover, ablation of PTEN expression partially rescued the migratory/invasive phenotype of Bmi-1-silenced cells, indicating that PTEN might be a major mediator of Bmi-1-induced EMT. Our results provide functional and mechanistic links between the oncoprotein Bmi-1 and the tumor suppressor PTEN in the development and progression of cancer.

BACKGROUND: epithelial-mesenchymal transition (EMT) is the key process driving cancer metastasis. Oncogene/self renewal factor BMI-1 has been shown to induce EMT in cancer cells. Recent studies have implied that noncoding microRNAs (miRNAs) act as crucial modulators for EMT. The aims of this study was to determine the roles of BMI-1 in inducing EMT of endometrial cancer (EC) cells and the possible role of miRNA in controlling BMI-1 expression. METHODS AND RESULTS: We evaluated the expression of BMI-1 gene in a panel of EC cell lines, and detected a strong association with invasive capability. Stable silencing of BMI-1 in invasive mesenchymal-type EC cells up-regulated the epithelial marker E-cadherin, down-regulated mesenchymal marker Vimentin, and significantly reduced cell invasion in vitro. Furthermore, we discovered that the expression of BMI-1 was suppressed by miR-194 via direct binding to the BMI-1 3'-untranslated region 3'-UTR). Ectopic expression of miR-194 in EC cells induced a mesenchymal to epithelial transition (MET) by restoring E-cadherin, reducing Vimentin expression, and inhibiting cell invasion in vitro. Moreover, BMI-1 knockdown inhibited in vitro EC cell proliferation and clone growth, correlated with either increased p16 expression or decreased expression of stem cell and chemoresistance markers (SOX-2, KLF4 and MRP-1). CONCLUSION: These findings demonstrate the novel mechanism for BMI-1 in contributing to EC cell invasion and that repression of BMI-1 by miR-194 could have a therapeutic potential to suppress EC metastasis.

cancer metastasis is the major cause of cancer-related death despite significant improvements in multimodal cancer therapy. epithelial-mesenchymal transition (EMT), a major mechanism of cancer metastasis, is a process that generates cells with stem cell-like properties (cancer stemness). cancer stemness is a concept that describes a minor population of cells (cancer stem cells) residing within a tumour that are able to self-renew and are resistant to conventional therapy. The mechanisms delineating the generation of cancer stemness and its connection to cancer metastasis remain largely unknown. Twist1 is an EMT regulator and increased Twist1 expression, which has prognostic significance in various human cancers, has been widely reported. Bmi1 is a critical component of polycomb repressive complex (PRC) 1, which maintains self-renewal and stemness. Bmi1 is frequently overexpressed in different types of human cancers and can induce drug resistance (Table 2). Recent studies have shown that Twist1 directly activates Bmi1 expression and that these two molecules function together to mediate cancer stemness and EMT. These results present a unique mechanism of EMT-induced cancer metastasis and stemness. Further investigation of the mechanisms of EMT-mediated cancer metastasis and stemness will contribute to the management and treatment of metastatic cancers.CI - (c) 2011 The Authors. Clinical and Experimental Pharmacology and Physiology (c) 2011 Blackwell Publishing Asia Pty Ltd.

EMT (epithelial-mesenchymal transition), a major mechanism of cancer metastasis, is a process that generates cells with stem-like properties. These stem-like cells in tumours are described as cancer stem cells. The link between EMT and cancer stemness is well documented without detailed mechanistic proof. Bmi1 belongs to the PRC1 (polycomb repressive complex 1) maintaining self-renewal and stemness together with EZH2 (enhancer of zeste homologue 2), which is a component of PRC2. Bmi1 is frequently overexpressed in different types of human cancers. Recent demonstration of an EMT regulator, Twist1, directly regulating the expression of Bmi1 provides a mechanistic explanation of the relationship between EMT and cancer stemness. The functional interdependence between Twist1 and Bmi1 provides a fresh insight into the common mechanism mediating EMT and cancer stemness. This observation is also confirmed using head and neck cancer patient samples. These results provide a critical mechanism of Twist1-induced EMT and cancer stemness in cancer cells through chromatin remodelling. The role of hypoxia and microRNAs in regulating EMT and cancer stemness is also discussed.CI - (c) The Authors Journal compilation (c) 2011 Biochemical SocietyFAU - Wu, Kou-Juey

PURPOSES: To investigate whether miR-15a inhibits cell proliferation and epithelial-mesenchymal transition (EMT) in pancreatic ductal adenocarcinoma (PDAC) via the down-regulation of B cell-specific moloney murine leukemia virus insertion site 1 (Bmi-1) expression. METHODS AND RESULTS: miR-15a and Bmi-1 expressions in normal pancreatic tissue and PDAC tissue were measured. The relationship between miR-15a and Bmi-1 expression was analyzed. We found that miR-15a suppressed the expression of Bmi-1 and PDAC cell proliferation; E-cadherin expression was visibly up-regulated after silencing Bmi-1 by transfecting miR-15a into PDAC cell line. CONCLUSION: miR-15a inhibits cell proliferation and EMT in PDAC via the down-regulation of Bmi-1 expression.CI - Copyright (c) 2013 Elsevier Ireland Ltd. All rights reserved.

BACKGROUND: Intraductal papillary mucinous neoplasm (IPMN) is a well-established entity among pancreatic neoplasms that ranges from low-grade dysplasia to invasive carcinoma. epithelial-mesenchymal transition (EMT) contributes to tumor progression in various cancers. Moreover, Notch signaling is one of the important upstream effectors of EMT promotion. Currently, it is unclear whether EMT causes pathological progression of IPMN. AIM: We evaluated the expression of EMT-promoting transcription factors Twist and B cell-specific Moloney murine leukemia virus insertion site 1 (Bmi1) in IPMN. METHODS: Patients who underwent resections at our institute and its affiliated hospital were enrolled in this study (n = 35). Protein expression of EMT markers Twist, Bmi1, Jagged1, and E-cadherin in resected specimens was investigated by immunohistochemistry. expression of these proteins was compared with the clinicopathological factors and patient survival. RESULTS: Positive expression of Twist and Bmi1 was observed in 40.0% and 42.9% of IPMNs, respectively. Twist and Bmi1 expression was significantly higher in IPMNs with high-grade dysplasia (P < 0.05) and invasive carcinoma (P < 0.05) than that in IPMNs with low-grade dysplasia. High expression of Twist was correlated with Jagged1 expression and inversely correlated with expression of E-cadherin (P = 0.06 and P < 0.05, respectively). In survival analyses, the recurrence rate was significantly higher in the group that showed simultaneous high expression of Twist and Bmi1 (P < 0.05). CONCLUSIONS: expression of Twist and Bmi1 is associated with aggressiveness and poor prognoses of IPMN through EMT promotion that might be induced by Notch signaling.CI - (c) 2014 Journal of Gastroenterology and Hepatology Foundation and Wiley Publishing Asia Pty Ltd.

Breast cancer is a highly invasive and metastatic disease. Recent studies report that breast cancer cells that have undergo epithelial-to-mesenchymal transition (EMT) obtain malignant characteristic, however, the molecular mechanism underlying this transition are poorly understood. Here, we found that over-expression associated with the process of breast cancer and that high B-cell-specific moloney murine leukemia virus insertion site 1 (Bmi-1) levels predict shorter survival of breast cancer patients. We demonstrate that Bmi-1 regulates EMT and the migration of breast cancer cells. RNA interference-mediated knockdown Bmi-1 expression restored E-cadherin expression and cell-cell junction formation in breast cancer cells, suppressing cell migration and invasion. In contrast, the over-expression of Bmi-1 decreased the expression of the epithelial mark (E-cadherin) but increased the mesenchymal makers (N-cadherin and vimentin) in breast cancer cells.

BACKGROUND: MicroRNA-200c (miR-200c) is one of the short noncoding RNAs that play crucial roles in tumorigenesis and tumor progression. It also acts as considerable modulator in the process of epithelial-to-mesenchymal transition (EMT), a cell development regulating process that affects tumor development and metastasis. However, the role of miR-200c in bladder cancer cells and its mechanism has not been well studied. The purpose of this study was to determine the potential role of miR-200c in regulating EMT and how it contributed to bladder cancer cells in invasion, migration and proliferation. METHODS: Real-time reverse transcription-PCR was used to identify and validate the differential expression of MiR-200c involved in EMT in 4 bladder cancer cell lines and clinical specimens. A list of potential miR-200 direct targets was identified through the TargetScan database. The precursor of miR-200c was over-expressed in UMUC-3 and T24 cells using a lentivirus construct, respectively. Protein expression and signaling pathway modulation were validated through Western blot analysis and confocal microscopy, whereas BMI-1 and E2F3, direct target of miR-200c, were validated by using the wild-type and mutant 3'-untranslated region BMI-1/E2F3 luciferase reporters. RESULTS: We demonstrate that MiR-200c is down-regulated in bladder cancer specimens compared with adjacent ones in the same patient. Luciferase assays showed that the direct down-regulation of BMI-1 and E2F3 were miR-200c-dependent because mutations in the two putative miR-200c-binding sites have rescued the inhibitory effect. Over-expression of miR-200c in bladder cancer cells resulted in significantly decreased the capacities of cell invasion, migration and proliferation. miR-200c over-expression resulted in conspicuous down-regulation of BMI-1 and E2F3 expression and in a concomitant increase in E-cadherin levels. CONCLUSIONS: miR-200c appears to control the EMT process through BMI-1 in bladder cancer cells, and it inhibits their proliferation through down-regulating E2F3. The targets of miR-200c include BMI-1 and E2F3, which are a novel regulator of EMT and a regulator of proliferation, respectively.

In human breast cancer, estrogen receptor-alpha (ERalpha) suppresses epithelial-mesenchymal transition (EMT) and stemness, two crucial parameters for tumor metastasis; however, the underlying mechanism by which ERalpha regulates these two processes remains largely unknown. Bmi1, the polycomb group protein B lymphoma Mo-MLV insertion region 1 homolog, regulates EMT transition, maintains the self-renewal capacity of stem cells, and is frequently overexpressed in human cancers. In the present study, ERalpha upregulated the expression of the epithelial marker, E-cadherin, in breast cancer cells through the transcriptional down-regulation of Bmi1. Furthermore, ERalpha overexpression suppressed the migration, invasion, and EMT of breast cancer cells. Notably, overexpression of ERalpha significantly decreased the CD44high/CD24low cell population and inhibited the capacity for mammosphere formation in ERalpha-negative breast cancer cells. In addition, overexpression of Bmi1 attenuated the ERalpha-mediated suppression of EMT and cell stemness. Immunohistochemistry revealed an inverse association of ERalpha and Bmi1 expression in human breast cancer tissue. Taken together, our findings suggest that ERalpha inhibits EMT and stemness through the downregulation of Bmi1.

epithelial-mesenchymal transition (EMT) is a crucial event required for the invasion and progression of carcinogenesis, inducing stem-like properties in epithelial cells. In the present study, the expression of BMI1, which controls self-renewal in stem cells, as well as that of ZEB1, a transcription factor that regulates EMT, was evaluated for its role in EMT and the carcinogenic processes of tongue squamous cell carcinoma (TSCC). Collagen invasion assays using two TSCC cells and 64 tongue specimens (32 carcinomas and 32 dysplasias) were employed and analyzed in the present study. We assessed the protein and mRNA expression levels of BMI1, ZEB1, vimentin and E-cadherin in the two cell lines and tumor tissues. The protein and mRNA expression of BMI1 and ZEB1 occurred at the invasion of TSCC. The elevated levels of BMI1 and ZEB1 were accompanied by the downregulation of E-cadherin and upregulation of vimentin at the invasive front, indicative of EMT in vitro and in vivo. The results showed that BMI1 and ZEB1 are important factors in association with the promotion of EMT and invasion of TSCC.

Aggressive tumor cells can mimic embryonic vasculogenic networks and form vasculogenic mimicry (VM). Preliminary studies demonstrated that hypoxia can promote VM formation; however, the underlying mechanism remains unclear. The present study aimed to investigate the role of the Twist1Bmi1 connection in hypoxiainduced VM formation and the underlying mechanism. In the in vitro experiments, western blot analysis demonstrated that hypoxia upregulated the expression of Twist1, Bmi1, epithelialmesenchymal transition (EMT) markers, stem cell markers and VMassociated markers. The 3D culture assay showed that hypoxia promoted VM formation in hepatocellular carcinoma (HCC) cell lines. Using transfection and in vitro cell experiments, the Twist1Bmi1 connection was confirmed to have an important role in inducing EMT, cell stemness and VM formation. In the in vivo experiments, the murine hypoxia models were established via incomplete femoral artery ligation and the mechanism by which hypoxia promoted Twist1 and Bmi1 expression and led to VM formation was demonstrated by immunohistochemistry staining and endomucin/periodic acid Schiff doublestaining. In conclusion, hypoxia upregulate the expression of Twist1 and Bmi1, and these two proteins have an important role in inducing EMT and cancer cell stemness, which contributed to VM formation.

epithelial-mesenchymal transition (EMT) contributes to the invasion and metastasis of numerous malignant cancers, including melanoma. A significant higher expression of B-lymphoma Moloney murine leukemia virus insertion region-1 (Bmi-1) has been reported in cell lines from metastatic melanoma compared to cell lines from primary melanoma. There are studies that show that knockdown of Bmi-1 could induce E-cadherin expression in melanoma cells. However, the role of Bmi-1 in mediating EMT-like changes in melanoma has not yet been fully studied. In the present study, knockdown of Bmi-1 by shRNA transduction decreased the invasion properties of the cultured human melanoma cells A375 by a Matrigel invasion assay, along with alterations in EMT-related markers E-cadherin, alpha-catenin, vimentin and N-cadherin. The aforementioned altered expression of EMT markers was verified in BALB/c-nude mouse xenografts. Furthermore, to explore the underlying regulatory mechanism of EMT, we detected the significant downregulation of p-Akt/pNF-kappaB/MMP-2 and the upregulation of PTEN in Bmi-1-silenced A375 cells. The present study demonstrated that knockdown of Bmi-1 significantly inhibited the aggressive behavior of melanoma by reversing EMT-like changes via the PTEN/p-Akt/pNF-kappaB/MMP-2 pathway.

miR-128 is expressed in various tumors, but its expression and function in gastric cancer have not been defined. Thus, the goal of this study was to characterize miR-128 in gastric cancer. We found first that miR-128 is down-regulated in gastric cancer cell lines and tissues, and this dysregulation is correlated with DNA methylation and the transcription factor SNAIL. Using prediction tools, western blotting, and luciferase reporter assays, we found that Bmi-1 was the direct target of miR-128. Additionally, overexpression of miR-128 inhibited gastric cancer cell migration, invasion, and proliferation by targeting Bmi-1 in vitro and in vivo. We also documented, with receiver operating characteristic curves and Kaplan-Meier survival analysis, that miR-128 and Bmi-1 may be useful markers for diagnosing and estimating the prognosis of gastric cancer patients. As the epithelial-to-mesenchymal transition is an important mechanism associated with cancer invasion and metastasis, we inferred that miR-128 could regulate this mechanism in gastric cancer. In fact, we found that miR-128 could reverse epithelial-to-mesenchymal transition induced by Bmi-1 via the PI3K/AKT pathway. Because SNAIL also acts as a mesenchymal marker, our findings identified a novel positive feedback loop in which the transcription factor SNAIL curbs the expression of miR-128, and then down-regulated miR-128 promotes the expression of Bmi-1; finally, overexpression of Bmi-1 drives the epithelial-to-mesenchymal transition process via the PI3K/AKT pathway, and the expression of SNAIL is up-regulated.

To determine whether p16 (INK4a) deletion ameliorated renal tubulointerstitial injury by inhibiting a senescence-associated secretory phenotype (SASP) in Bmi-1-deficient (Bmi-1 (-/-)) mice, renal phenotypes were compared among 5-week-old Bmi-1 and p16 (INK4a) double-knockout, and Bmi-1 (-/-) and wild-type mice. Fifth-passage renal interstitial fibroblasts (RIFs) from the three groups were analyzed for senescence and proliferation. The effect of Bmi-1 deficiency on epithelial-to-mesenchymal transition (EMT) was examined in Bmi-1-knockdown human renal proximal tubular epithelial (HK2) cells, which were treated with concentrated conditioned medium (CM) from the fifth-passage renal interstitial fibroblasts (RIFs) of above three group mice or with exogenous TGF-beta1. Our results demonstrated that p16 (INK4a) deletion largely rescued renal aging phenotypes caused by Bmi-1 deficiency, including impaired renal structure and function, decreased proliferation, increased apoptosis, senescence and SASP, DNA damage, NF-kappaB and TGF-beta1/Smad signal activation, inflammatory cell infiltration, and tubulointerstitial fibrosis and tubular atrophy. P16 (INK4a) deletion also promoted proliferation, reduced senescence and SASP of RIFs and subsequently inhibited EMT of Bmi-1-knockdown HK2 cells. TGF-beta1 further induced the EMT of Bmi-1-knockdown HK2 cells. Thus, p16 (INK4a) positive senescent cells would be a therapeutic target for preventing renal tubulointerstitial injury.

BACKGROUND MicroRNA-200c (miR-200c) is a short non-coding RNA that has a role in tumorigenesis and cancer progression. The aims of this study were to investigate the role of miR-200c in cell migration and epithelial-mesenchymal transition (EMT) in endometrial carcinoma cells in vitro. MATERIAL AND METHODS Potential direct targets of miR-200c were identified through the TargetScan database. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was used study the expression of miR-200c in the endometrial carcinoma cell lines, Ishikawa and JEC, in vitro. Cell migration was studied using transwell assays. expression of the mesenchymal marker, N-cadherin, the epithelial marker, E-cadherin, the transcription factor, Slug, the BMI-1 protein, AKT, and p-AKT were measured using Western blot. Small interfering RNA (siRNA) was used to silence the BMI-1 gene to study the targeting effect. RESULTS Over-expression of miR-200c in Ishikawa and JEC cells resulted in reduced cell migration and proliferation. Western blot showed that overexpression of miR-200c downregulated the expression of the BMI-1 protein, p-AKT, N-cadherin and Slug, and the expression E-cadherin was upregulated; silencing miR-200c reversed these results. Silencing the BMI-1 gene inhibited EMT and suppressed p-AKT in miR-200c-inhibited endometrial carcinoma cells by increasing E-cadherin expression, reducing the expression of N-cadherin and the EMT-associated transcription factor, Slug. CONCLUSIONS In endometrial carcinoma cells in vitro, miR-200c inhibited EMT by targeting the BMI-1 gene through the p-AKT pathway.

BMI-1 (B-lymphoma Mo-MLV insertion region 1) is a key protein partner in polycomb repressive complex 1 (PRC1) that helps in maintaining the integrity of the complex. It is also a key player in ubiquitination of histone H2A which affects gene expression pattern involved in various cellular processes such as cell proliferation, growth, DNA repair, apoptosis and senescence. In many cancers, Overexpression of BMI1correlates with advanced stages of disease, aggressive clinicopathological behavior, poor prognosis resistance to radiation and chemotherapy. BMI1 is emerging as a key player in EMT, chemo-resistance and cancer stemness. Overexpression is observed in various cancer types such as breast, primary hepatocellular carcinoma (HCC), gastric, ovarian, head and neck, pancreatic and lung cancer. Studies have shown that experimental reduction of BMI protein level in tumor cells results in inhibition of cell proliferation, induction of apoptosis and/or senescence, and increases susceptibility to cytotoxic agents and radiation therapy. Thus, inhibition of BMI1 expression particularly in breast cancer stem cells can be used as a potential strategy for the complete elimination of tumor and to prevent disease relapse. On other hand PTEN is known to be an important tumor suppressor next to p53. In many cancers particularly in breast cancer, p53 and PTEN undergo mutations. Studies have indicated the functional and mechanistic link between the BMI-1oncoprotein and tumor suppressor PTEN in the development and progression of cancer. The current review focuses on recent findings of how oncogenicity and chemo-resistance are caused by BMI1. It also highlights the transcriptional regulation between BMI1 and PTEN that dictates the therapeutic outcome in cancers where the functional p53 is absent. Herein, we have clearly demonstrated the regulation of transcription at genomic loci of BMI1 and PTEN in cancerous tissue or cells and the possible epigenetic regulation by histone deacetylase inhibitors (HDACi) at BMI1 and PTEN loci that may provide some clue for the possible therapy against TNBC in near future.CI - Copyright (c) 2018 Elsevier B.V. All rights reserved.