Gene Summary

Gene:PRC1; protein regulator of cytokinesis 1
Aliases: ASE1
Summary:This gene encodes a protein that is involved in cytokinesis. The protein is present at high levels during the S and G2/M phases of mitosis but its levels drop dramatically when the cell exits mitosis and enters the G1 phase. It is located in the nucleus during interphase, becomes associated with mitotic spindles in a highly dynamic manner during mitosis, and localizes to the cell mid-body during cytokinesis. This protein has been shown to be a substrate of several cyclin-dependent kinases (CDKs). It is necessary for polarizing parallel microtubules and concentrating the factors responsible for contractile ring assembly. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Jun 2012]
Databases:VEGA, OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:protein regulator of cytokinesis 1
Source:NCBIAccessed: 11 March, 2017


What does this gene/protein do?
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Cancer Overview

Research Indicators

Publications Per Year (1992-2017)
Graph generated 11 March 2017 using data from PubMed using criteria.

Literature Analysis

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Tag cloud generated 11 March, 2017 using data from PubMed, MeSH and CancerIndex

Specific Cancers (6)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: PRC1 (cancer-related)

Tong H, Wang J, Chen H, et al.
Transcriptomic analysis of gene expression profiles of stomach carcinoma reveal abnormal expression of mitotic components.
Life Sci. 2017; 170:41-49 [PubMed] Related Publications
AIMS: In order to explore the etiology of gastric cancer on global gene expression level, we developed advanced bioinformatic analysis to investigate the variations of global gene expression and the interactions among them.
MAIN METHODS: We downloaded the dataset GSE63288 from Gene Expression Omnibus (GEO) database which included 22 human gastric cancer and 22 healthy control samples. We identified the differential expression genes, and explored the Gene ontology (GO) and pathways of the differentially expressed genes. Furthermore, integrative interaction network and co-expression network were employed to identify the key genes which may contribute to gastric cancer progression.
KEY FINDINGS: The results indicated that 5 kinases including BUB1, TTK protein kinase, Citron Rho-interacting kinase (CIT), ZAK and NEK2 were upregulated in gastric cancer. Interestingly, BUB1, TTK, CIT and NEK2 have shown high expression similarities and bound with each other, and participated in multiple phases of mitosis. Moreover, a subnet of co-expression genes e.g. KIF14, PRC1, CENPF and CENPI was also involved in mitosis which was functionally coupled with the kinases above. By validation assays, the results indicated that CIT, PRC1, TTK and KIF14 were significantly upregulated in gastric cancer.
SIGNIFICANCE: These evidences have suggested that aberrant expression of these genes may drive gastric cancer including progression, invasion and metastasis. Although the causal relationships between gastric cancer and the genes are still lacking, it was reasonable to take them as biomarkers for diagnosis of gastric cancer.

Patel N, Garikapati KR, Ramaiah MJ, et al.
miR-15a/miR-16 induces mitochondrial dependent apoptosis in breast cancer cells by suppressing oncogene BMI1.
Life Sci. 2016; 164:60-70 [PubMed] Related Publications
AIMS: miRNAs are small non-coding RNA molecules that regulate post-transcriptional gene expression. Here we have made an endeavor to search whether any miRNAs are involved in the regulation of BMI1 in breast cancer that leads to mitochondrial dependent apoptotic cell death.
MAIN METHODS: Renilla luciferase reporter assay was performed to detect the ectopically expressed miRNAs that regulate the expression of 3' UTR of BMI1. MTT assay was performed to check the cytotoxicity level. Western blotting and qRT-PCR were performed to check the expression of BMI1, pro-apoptotic, anti-apoptotic proteins and mRNA expression levels respectively. JC-1 staining, Caspase-3, Caspase-6/9 assay and mitochondrial cytosolic fractionation were performed to monitor mitochondrial dependent apoptosis. Wound healing assay was performed to investigate migration. All experiments were performed upon miR-15a and miR-16 overexpression in MCF-7, MDAMB-231 breast cancer cells.
KEY FINDINGS: In MCF-7, MDAMB-231 breast cancer cells luciferase reporter assay confirmed the significant reduction of reporter activity upon co-transfection of 3' UTR of BMI1 along with miR-15a and miR-16. miR-15a and miR-16 significantly down-regulated BMI1 protein and mRNA expression levels as well as anti-apoptotic protein BCL2 and up-regulated pro-apoptotic proteins. Ectopic expression of miR-15a, miR-16, increased mitochondrial ROS resulting in impaired mitochondrial membrane potential, followed by cytochrome-C release into the cytosol that activated Caspase-3 and Caspase-6/9 leading to intrinsic apoptosis. Additionally, it also inhibits migration.
SIGNIFICANCE: Our results suggest that overexpression of miR-15a and miR-16 mediates down-regulation of BMI1, and leads to mitochondrial mediated apoptosis.

Brynychova V, Ehrlichova M, Hlavac V, et al.
Genetic and functional analyses do not explain the association of high PRC1 expression with poor survival of breast carcinoma patients.
Biomed Pharmacother. 2016; 83:857-864 [PubMed] Related Publications
Microtubules are vitally important for eukaryotic cell division. Therefore, we evaluated the relevance of mitotic kinesin KIF14, protein-regulating cytokinesis 1 (PRC1), and citron kinase (CIT) for the prognosis of breast carcinoma patients. Transcript levels were assessed by quantitative real-time PCR in tissues from two independent groups of breast carcinoma patients and compared with clinical data. Tissue PRC1 protein levels were estimated using immunoblotting, and the PRC1 tagged haplotype was analyzed in genomic DNA. A functional study was performed in MDA-MB-231 cells in vitro. KIF14, PRC1, and CIT transcripts were overexpressed in tumors compared with control tissues. Tumors without expression of hormonal receptors or high-grade tumors expressed significantly higher KIF14 and PRC1 levels than hormonally-positive or low-grade tumors. Patients with high intra-tumoral PRC1 levels had significantly worse disease-free survival than patients with low levels. PRC1 rs10520699 and rs11852999 polymorphisms were associated with PRC1 transcript levels, but not with patientś survival. Paclitaxel-induced PRC1 expression, but PRC1 knockdown did not modify the paclitaxel cytotoxicity in vitro. PRC1 overexpression predicts poor disease-free survival of patients with breast carcinomas. Genetic variability of PRC1 and the protein interaction with paclitaxel cytotoxicity do not explain this association.

Shahi MH, Farheen S, Mariyath MP, Castresana JS
Potential role of Shh-Gli1-BMI1 signaling pathway nexus in glioma chemoresistance.
Tumour Biol. 2016; 37(11):15107-15114 [PubMed] Related Publications
Chemoresistance is a common hurdle for the proper treatment of gliomas. The role of Shh-Gli1 signaling in glioma progression has been reported. However, its role in glioma chemoresistance has not been well studied yet. In this work, we found that Shh-Gli1 signaling regulates the expression of one stem cell marker, BMI1 (B cell-specific Moloney murine leukemia virus), in glioma. Interestingly, we also demonstrated high expression of MRP1 (multi-drug resistance protein 1) in glioma. MRP1 expression was decreased by BMI1 siRNA and Shh-Gli1 cell signaling specific inhibitor GANT61 in our experiments. GANT61 very efficiently inhibited cell colony growth in glioma cell lines, compared to temozolomide. Moreover, a synergic effect of GANT61 and temozolomide drastically decreased the LD50 of temozolomide in the cell colony experiments. Therefore, our results suggest that there is a potential nexus of Shh-Gli1-BMI1 cell signaling to regulate MRP1 and to promote chemoresistance in glioma. Henceforth, our study opens the possibility of facing new targets, Gli1 and BMI1, for the effective treatment of glioma suppression of chemoresistance with adjuvant therapy of GANT61 and temozolomide.

Zhang Z, Bu X, Chen H, et al.
Bmi-1 promotes the invasion and migration of colon cancer stem cells through the downregulation of E-cadherin.
Int J Mol Med. 2016; 38(4):1199-207 [PubMed] Free Access to Full Article Related Publications
Metastasis and recurrence are the challenges of cancer therapy. Recently, mounting evidence has suggested that cancer stem cells (CSCs) and epithelial-mesenchymal transition (EMT) are critical factors in tumor metastasis and recurrence. The oncogene, Bmi-1, promotes the development of hematologic malignancies and many solid tumors. The aim of the present study was to elucidate the mechanisms through which Bmi-1 promotes the invasion and migration of colon CSCs (CCSCs) using the HCT116 colon cancer cell line. Sphere formation medium and magnetic‑activated cell sorting were used to enrich and screen the CCSCs. CD133 and CD44 were regarded as markers of CCSCs and they were found to be co-expressed in the HCT116 colon cancer cell line. Colony formation assay, cell proliferation assay and viability assay using the Cell Counting Kit-8, and transplantation assay using nude mice injected with CCSCs were used to examine the CCSCs. The CD133+CD44+ HCT116 cells exhibited greater cloning efficiency, an enhanced proliferative ability, increased cell viability and stronger tumorigenicity; these cells were used as the CCSCs for subsequent experiments. In addition, the invasive and migratory abilities of the CD133+CD44+ HCT116 cells were markedly decreased when Bmi-1 was silenced by small interfering RNA (siRNA). The results of RT-qPCR and western blot analysis suggested that Bmi-1 had a negative effect on E-cadherin expression. On the whole, our findings suggest that Bmi-1 promotes the invasion and migration of CCSCs through the downregulation of E-cadherin, possibly by inducing EMT. Our findings thus indicate that Bmi-1 may be a novel therapeutic target for the treatment of colon cancer.

Piunti A, Shilatifard A
Epigenetic balance of gene expression by Polycomb and COMPASS families.
Science. 2016; 352(6290):aad9780 [PubMed] Related Publications
Epigenetic regulation of gene expression in metazoans is central for establishing cellular diversity, and its deregulation can result in pathological conditions. Although transcription factors are essential for implementing gene expression programs, they do not function in isolation and require the recruitment of various chromatin-modifying and -remodeling machineries. A classic example of developmental chromatin regulation is the balanced activities of the Polycomb group (PcG) proteins within the PRC1 and PRC2 complexes, and the Trithorax group (TrxG) proteins within the COMPASS family, which are highly mutated in a large number of human diseases. In this review, we will discuss the latest findings regarding the properties of the PcG and COMPASS families and the insight they provide into the epigenetic control of transcription under physiological and pathological settings.

Kaufhold S, Garbán H, Bonavida B
Yin Yang 1 is associated with cancer stem cell transcription factors (SOX2, OCT4, BMI1) and clinical implication.
J Exp Clin Cancer Res. 2016; 35:84 [PubMed] Free Access to Full Article Related Publications
The transcription factor Yin Yang 1 (YY1) is frequently overexpressed in cancerous tissues compared to normal tissues and has regulatory roles in cell proliferation, cell viability, epithelial-mesenchymal transition, metastasis and drug/immune resistance. YY1 shares many properties with cancer stem cells (CSCs) that drive tumorigenesis, metastasis and drug resistance and are regulated by overexpression of certain transcription factors, including SOX2, OCT4 (POU5F1), BMI1 and NANOG. Based on these similarities, it was expected that YY1 expression would be associated with SOX2, OCT4, BMI1, and NANOG's expressions and activities. Data mining from the proteomic tissue-based datasets from the Human Protein Atlas were used for protein expression patterns of YY1 and the four CSC markers in 17 types of cancer, including both solid and hematological malignancies. A close association was revealed between the frequency of expressions of YY1 and SOX2 as well as SOX2 and OCT4 in all cancers analyzed. Two types of dynamics were identified based on the nature of their association, namely, inverse or direct, between YY1 and SOX2. These two dynamics define distinctive patterns of BMI1 and OCT4 expressions. The relationship between YY1 and SOX2 expressions as well as the expressions of BMI1 and OCT4 resulted in the classification of four groups of cancers with distinct molecular signatures: (1) Prostate, lung, cervical, endometrial, ovarian and glioma cancers (YY1(lo)SOX2(hi)BMI1(hi)OCT4(hi)) (2) Skin, testis and breast cancers (YY1(hi)SOX2(lo)BMI1(hi)OCT4(hi)) (3) Liver, stomach, renal, pancreatic and urothelial cancers (YY1(lo)SOX2(lo)BMI1(hi)OCT4(hi)) and (4) Colorectal cancer, lymphoma and melanoma (YY1(hi)SOX2(hi)BMI1(lo)OCT4(hi)). A regulatory loop is proposed consisting of the cross-talk between the NF-kB/PI3K/AKT pathways and the downstream inter-regulation of target gene products YY1, OCT4, SOX2 and BMI1.

Yi C, Li BB, Zhou CX
Bmi-1 expression predicts prognosis in salivary adenoid cystic carcinoma and correlates with epithelial-mesenchymal transition-related factors.
Ann Diagn Pathol. 2016; 22:38-44 [PubMed] Related Publications
Salivary adenoid cystic carcinoma (AdCC) is known for its high propensity to invade and metastasize. Bmi-1 acts as an oncogene by controlling cell cycle and self-renewal of adult stem cells, and its overexpression correlates with metastasis and poor prognosis in several cancers. Epithelial-mesenchymal transition (EMT) plays a central role in cancer metastasis. A key step in EMT is the down-regulation of E-cadherin that can be repressed by the transcriptional factors, such as Snail and Slug. In the present study, we investigated Bmi-1, Snail, Slug, and E-cadherin expression by immunohistochemistry in 102 patients with AdCC and analyzed statistically whether their expression correlated with clinicopathologic factors and prognosis. Reverse transcription-polymerase chain reaction was also performed in 22 tumor tissues and the adjacent noncancerous tissues to confirm Bmi-1 status in AdCCs. Our data demonstrated significant associations between the tumor metastasis and the expression of Bmi-1, Snail, Slug, and E-cadherin. Furthermore, a high level of Bmi-1 was not only correlated with the overexpression of Snail and Slug but also indicated an unfavorable metastasis-free survival and served as a high-risk marker for AdCC. In addition, Bmi-1 messenger RNA level was found much higher in AdCC tissues than in the adjacent noncancerous salivary gland tissues. Our results suggest that Bmi-1 may play a crucial role in AdCC progression by interaction with EMT-related markers and predict poor survival.

Lu C, Jain SU, Hoelper D, et al.
Histone H3K36 mutations promote sarcomagenesis through altered histone methylation landscape.
Science. 2016; 352(6287):844-9 [PubMed] Free Access to Full Article Related Publications
Several types of pediatric cancers reportedly contain high-frequency missense mutations in histone H3, yet the underlying oncogenic mechanism remains poorly characterized. Here we report that the H3 lysine 36-to-methionine (H3K36M) mutation impairs the differentiation of mesenchymal progenitor cells and generates undifferentiated sarcoma in vivo. H3K36M mutant nucleosomes inhibit the enzymatic activities of several H3K36 methyltransferases. Depleting H3K36 methyltransferases, or expressing an H3K36I mutant that similarly inhibits H3K36 methylation, is sufficient to phenocopy the H3K36M mutation. After the loss of H3K36 methylation, a genome-wide gain in H3K27 methylation leads to a redistribution of polycomb repressive complex 1 and de-repression of its target genes known to block mesenchymal differentiation. Our findings are mirrored in human undifferentiated sarcomas in which novel K36M/I mutations in H3.1 are identified.

Bo C, Li N, Li X, et al.
Long noncoding RNA uc.338 promotes cell proliferation through association with BMI1 in hepatocellular carcinoma.
Hum Cell. 2016; 29(4):141-7 [PubMed] Related Publications
Hepatocellular carcinoma (HCC) is one of the most common human cancers all over the world. Increasing evidences have demonstrated that long noncoding RNAs (lncRNAs) play important roles in malignant transformation, tumor growth and metastasis in HCC. Among lncRNAs, ultraconserved RNAs (ucRNAs) containing an ultraconserved region have been report to contribute to human cancers. lncRNA ultraconserved element 338 (uc.338) was first found to be upregulated in HCC and promote cell growth. However, the exact mechanism by which uc.338 modulates cell growth remains unclear. In the present study, we demonstrated that uc.338 promotes HCC cell proliferation and induces cell cycle progression. RNA-immunoprecipitation and RNA pull-down assays showed that uc.338 associated with BMI1. We found that uc.338 promotes HCC cell proliferation and induces cell cycle progression through association with BMI1. uc.338 also modulated the transcription of CDKN1A. The oncogenic activity of uc.338 is partially due to its repression of p21. uc.338 may be a potential target for HCC therapy.

Jo S, Lee YL, Kim S, et al.
PCGF2 negatively regulates arsenic trioxide-induced PML-RARA protein degradation via UBE2I inhibition in NB4 cells.
Biochim Biophys Acta. 2016; 1863(7 Pt A):1499-509 [PubMed] Related Publications
Arsenic trioxide (ATO) is a therapeutic agent for acute promyelocytic leukemia (APL) which induces PML-RARA protein degradation via enhanced UBE2I-mediated sumoylation. PCGF2, a Polycomb group protein, has been suggested as an anti-SUMO E3 protein by inhibiting the sumoylation of UBE2I substrates, HSF2 and RANGAP1, via direct interaction. Thus, we hypothesized that PCGF2 might play a role in ATO-induced PML-RARA degradation by interacting with UBE2I. PCGF2 protein was down-regulated upon ATO treatment in human APL cell line, NB4. Knockdown of PCGF2 in NB4 cells, in the absence of ATO treatment, was sufficient to induce sumoylation-, ubiquitylation- and PML nuclear body-mediated degradation of PML-RARA protein. Moreover, overexpression of PCGF2 protected ATO-mediated degradation of ectopic and endogenous PML-RARA in 293T and NB4 cells, respectively. In 293T cells, UBE2I-mediated PML-RARA degradation was reduced upon PCGF2 co-expression. In addition, UBE2I-mediated sumoylation of PML-RARA was reduced upon PCGF2 co-expression and PCGF2-UBE2I interaction was confirmed by co-immunoprecipitation. Likewise, endogenous PCGF2-UBE2I interaction was detected by co-immunoprecipitation and immunofluorescence assays in NB4 cells. Intriguingly, upon ATO-treatment, such interaction was disrupted and UBE2I was co-immunoprecipitated or co-localized with its SUMO substrate, PML-RARA. Taken together, our results suggested a novel role of PCGF2 in ATO-mediated degradation of PML-RARA that PCGF2 might act as a negative regulator of UBE2I via direct interaction.

Kenny C, Bausenwein S, Lazaro A, et al.
Mutually exclusive BCOR internal tandem duplications and YWHAE-NUTM2 fusions in clear cell sarcoma of kidney: not the full story.
J Pathol. 2016; 238(5):617-20 [PubMed] Related Publications
Internal tandem duplication within the BCOR gene sequence that encodes the PUFD domain, important in the formation of the non-canonical or variant polycomb repressor complex 1 (v-PRC1), was very recently described in 100% of 20 clear cell sarcomas of kidney (CCSKs). None of those 20 cases bore the YWHAE-NUTM2 transcript, previously described by us in CCSK, and which constitutes the only other recurrent genetic aberration observed in CCSK, prompting consideration that these mutations might be mutually exclusive in CCSK. We analysed a cohort of 159 CCSKs and can now not only confirm that there is indeed mutual exclusivity of these BCOR and YWHAE mutations, but also show that a substantial proportion (in this series 11.8%) of CCSKs bear neither mutation when tested by these assays, raising the possibility of distinct aetiologies for subsets of CCSK. Clinical differences observed between the subsets support this notion. As CCSK may show poor chemo-responsiveness, and current treatment protocols mandate the use of doxorubicin with its associated side-effects, advances in understanding the disease biology with a view to more targeted and personalized treatment is a pressing need.

Chen SJ, Chen YT, Zeng LJ, et al.
Bmi1 combines with oncogenic KRAS to induce malignant transformation of human pancreatic duct cells in vitro.
Tumour Biol. 2016; 37(8):11299-309 [PubMed] Related Publications
It is critical to understand the pathogenesis of preinvasive stages of pancreatic duct adenocarcinoma (PDAC) for developing novel potential diagnostic and therapeutic targets. The polycomb group family member B-lymphoma Moloney murine leukemia virus insertion region-1 (Bmi1) is overexpressed and involved in cancer progression in PDAC; however, its role in the multistep malignant transformation of human pancreatic duct cells has not been directly demonstrated. In this study, we stably expressed Bmi1 in a model of telomerase-immortalized human pancreatic duct-derived cells (HPNE) and showed that Bmi1 promoted HPNE cell proliferation, migration, and invasion but not malignant transformation. We then used mutant KRASG12D as a second oncogene to transform HPNE cells and showed that it further enhanced Bmi1-induced malignant potential. More importantly, coexpression of KRASG12D and Bmi1 caused anchorage-independent growth transformation in vitro but still failed to produce tumors in nude mice. Finally, we found that mutant KRASG12D induced HPNE-Bmi1 cells to undergo partial epithelial-mesenchymal transition (EMT) likely via upregulation of snail. Knockdown of KRASG12D significantly reduced the expression of snail and vimentin at both the messenger RNA (mRNA) and protein level and further impaired the anchorage-independent growth capability of invasive cells. In summary, our findings demonstrate that coexpression of Bmi1 and KRASG12D could lead to transformation of HPNE cells in vitro and suggest potential new targets for diagnosis and treatment of PDAC.

Taran K, Wysocka A, Sitkiewicz A, et al.
Evaluation of potential prognostic value of Bmi-1 gene product and selected markers of proliferation (Ki-67) and apoptosis (p53) in the neuroblastoma group of tumors.
Postepy Hig Med Dosw (Online). 2016; 70:110-6 [PubMed] Related Publications
INTRODUCTION: Cancer in children is a very important issue in pediatrics. The least satisfactory treatment outcome occurs among patients with clinically advanced neuroblastomas. Despite much research, the biology of this tumor still remains unclear, and new prognostic factors are sought. The Bmi-1 gene product is a currently highly investigated protein which belongs to the Polycomb group (PcG) and has been identified as a regulator of primary neural crest cells. It is believed that Bmi‑1 and N-myc act together and are both involved in the pathogenesis of neuroblastoma. The aim of the study was to assess the potential prognostic value of Bmi-1 protein and its relations with mechanisms of proliferation and apoptosis in the neuroblastoma group of tumors.
MATERIAL/METHODS: 29 formalin-fixed and paraffin-embedded neuroblastoma tissue sections were examined using mouse monoclonal antibodies anti-Bmi-1, anti-p53 and anti-Ki-67 according to the manufacturer's instructions.
RESULTS: There were found statistically significant correlations between Bmi-1 expression and tumor histology and age of patients.
CONCLUSIONS: Bmi-1 seems to be a promising marker in the neuroblastoma group of tumors whose expression correlates with widely accepted prognostic parameters. The pattern of BMI-1 expression may indicate that the examined protein is also involved in maturation processes in tumor tissue.

Yang XX, Ma M, Sang MX, et al.
Radiosensitization of esophageal carcinoma cells by knockdown of RNF2 expression.
Int J Oncol. 2016; 48(5):1985-96 [PubMed] Related Publications
Radiotherapy has been widely used for the treatment of cancer patients, especially for esophageal cancer patients. Ring finger protein 2 (RNF2) plays an important role in promoting the growth of cancer cells after exposure to irradiation. The present study aims to characterize the proliferative effects of RNF2 on cancer cells, and its mechanisms on the growth of esophageal cancer cells. We demonstrate that expression of RNF2 was markedly upregulated in esophageal cancer cell lines and surgically resected cancer specimens. In addition, RNF2 expression level is positively correlated with the presence of tumor size, lymph node metastases and negatively correlated with patient survival rates, suggesting that it plays an important role in the progression of esophageal cancer. Furthermore, the expression of RNF2 at both mRNA and protein levels in esophageal cancer ECA109 and TE13 cells was detected by real-time PCR and western blot assay after shRNA targeting RNF2. Co-immunoprecipitation (Co-IP) assay and western blot analysis were employed to detect the interaction between RNF2 and r-H2AX, H2AK119ub, and the expression of proteins associated with cell cycle and apoptosis, respectively. We used flow cytometry assay to analyze cell cycle and apoptosis of transfected cells, and further examined cellular growth in vitro and in vivo. shRNA targeting RNF2 gene and protein downregulated RNF2 expression after transfection for 24 h. The proliferation of tumor cells in RNF2-shRNA group was suppressed after radiotherapy. In addition, the interaction of RNF2, H2AK119ub, r-H2AX was increased after exposure to IR, followed by increasing apoptosis rates and inducing the arrest at G0/G1 phase after irradiation and shRNA targeting RNF2. Expression of the short-hairpin RNA is also correlated with the upregulation of p16 and Bax, and the downregulation of cyclin D2, cyclin-dependent kinase (CDK)-4, H2AX and Bcl-2. RNF2 gene knockdown induces radiosensitivity of esophageal cancer cells in vitro and significantly inhibits the growth of tumor cells. The mechanisms include inducing the cell cycle arrest at G0/G1 phase and promoting apoptosis.

Bolomsky A, Schlangen K, Schreiner W, et al.
Targeting of BMI-1 with PTC-209 shows potent anti-myeloma activity and impairs the tumour microenvironment.
J Hematol Oncol. 2016; 9:17 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: The polycomb complex protein BMI-1 (BMI-1) is a putative oncogene reported to be overexpressed in multiple myeloma (MM). Silencing of BMI-1 was shown to impair the growth and survival of MM cells. However, therapeutic agents specifically targeting BMI-1 were not available so far. Here, we investigated PTC-209, a novel small molecule inhibitor of BMI-1, for its activity in MM.
METHODS: BMI-1 expression was analysed in human MM cell lines and primary MM cells by using publically available gene expression profiling (GEP) data. The anti-MM activity of PTC-209 was investigated by viability testing, cell cycle analysis, annexin V and 7-AAD staining, quantification of cleaved poly(ADP-ribose) polymerase (PARP), JC-1 as well as colony formation assays. Deregulation of central myeloma growth and survival genes was studied by quantitative PCR and flow cytometry, respectively. In addition, the impact of PTC-209 on in vitro osteoclast, osteoblast and tube formation was analysed.
RESULTS: We confirmed overexpression of BMI-1 in MM patients by using publically available GEP datasets. Of note, BMI-1 expression was further increased at relapse which translated into significantly shorter overall survival in relapsed/refractory patients treated with bortezomib or dexamethasone. Treatment with PTC-209 significantly decreased viable cell numbers in human MM cell lines, induced a G1 cell cycle arrest, promoted apoptosis and demonstrated synergistic activity with pomalidomide and carfilzomib. The anti-MM activity of PTC-209 was accompanied by a significant decrease of cyclin D1 (CCND1) and v-myc avian myelocytomatosis viral oncogene homolog (MYC) expression as well as upregulation of cyclin-dependent kinase inhibitor 1A (CDKN1A) and cyclin-dependent kinase inhibitor 1B (CDKN1B). We also observed upregulation of NOXA (up to 3.6 ± 1.2-fold induction, P = 0.009) and subsequent downregulation of myeloid cell leukemia 1 (MCL-1) protein levels, which likely mediates the apoptotic effects of PTC-209. Importantly, the anti-MM activity was upheld in the presence of stromal support or myeloma growth factors insulin-like growth factor 1 (IGF-1) and interleukin 6 (IL-6). In the MM microenvironment, PTC-209 impaired tube formation, impaired osteoclast development and decreased osteoblast formation in a dose-dependent manner (P < 0.01 at 1 μM, respectively). The latter might be attributed to an induction of DKK1 and was reversed by concurrent anti-DKK1 antibody treatment.
CONCLUSIONS: We confirmed overexpression of BMI-1 in MM highlighting its role as an attractive drug target and reveal therapeutic targeting of BMI-1 by PTC-209 as a promising novel therapeutic intervention for MM.

Sang Y, Tang J, Li S, et al.
LncRNA PANDAR regulates the G1/S transition of breast cancer cells by suppressing p16(INK4A) expression.
Sci Rep. 2016; 6:22366 [PubMed] Free Access to Full Article Related Publications
It has been reported that lncRNA PANDAR (promoter of CDKN1A antisense DNA damage-activated RNA) is induced as a result of DNA damage, and it regulates the reparation of DNA damage. In this study, we investigated the role of lncRNA PANDAR in the progression of breast cancer and found that PANDAR was up-regulated in breast cancer tissues and cell lines. The knockdown of PANDAR suppresses G1/S transition of breast cancer cells. We demonstrated mechanistically that the regulation of G1/S transition by PANDAR was partly due to the transcriptional modulation of p16(INK4A). Moreover, we showed that PANDAR impacted p16(INK4A) expression by regulating the recruitment Bmi1 to p16(INK4A) promoter. To our knowledge, this is the first study which showed the functional roles and mechanisms of PANDAR in regulating the progression of breast cancer. The PANDAR/Bmi1/p16(INK4A) axis could serve as novel targets for breast cancer therapy.

Wu WR, Sun H, Zhang R, et al.
Methylation-associated silencing of miR-200b facilitates human hepatocellular carcinoma progression by directly targeting BMI1.
Oncotarget. 2016; 7(14):18684-93 [PubMed] Free Access to Full Article Related Publications
This study aims to investigate the biological function of microRNA-200b and BMI1, predicted target of microRNA-200b in human hepatocellular carcinoma (HCC). MicroRNA-200b and BMI1 expression in HCC tissues were evaluated by qPCR. A luciferase reporter assay was used to validate BMI1 as a direct target of microRNA-200b. The effect of microRNA-200b on HCC progression was studied in vitro and in vivo. Methylation specific PCR (MSP) and bisulfite sequencing PCR (BSP) were used to detect the methylation status of the microRNA-200b promoter. Significant downregulation of microRNA-200b was observed in 83.3% of HCC tissues. By contrast, BMI1 was significantly overexpressed in 66.7% of HCC tissues. The results of the luciferase assay confirmed BMI1 as a direct target gene of microRNA-200b. Forced expression of microRNA-200b in HCC cells dramatically repressed proliferation, colony formation, cell cycle progression, and invasion. Moreover, microRNA-200b synergized with 5-fluorouracil to induce apoptosis in vitro and suppressed tumorigenicity in vivo. In addition, MSP analysis and BSP revealed that CpG sites in the promoter region of microRNA-200b were extensively methylated in HCC, with concomitant downregulation of microRNA-200b expression. Furthermore, microRNA-200b was activated in HCC cells after treatment with 5-azacytidine, whereas BMI1 expression was clearly downregulated. Our results indicate that microRNA-200b is partially silenced by DNA hypermethylation and that it can repress tumor progression by directly targeting BMI1 in HCC.

Luo HW, Chen QB, Wan YP, et al.
Protein regulator of cytokinesis 1 overexpression predicts biochemical recurrence in men with prostate cancer.
Biomed Pharmacother. 2016; 78:116-20 [PubMed] Related Publications
BACKGROUND: Protein regulator of cytokinesis 1 (PRC1) has been reported to be implicated into the completion of cytokinesis and is dys-regulated in a cancer-specific manner. However, it roles in human prostate cancer (PCa) remain unclear. In the current study, we aimed to investigate the expression pattern of PRC1 and its clinical significance in this malignancy.
MATERIALS AND METHODS: PRC1 protein expression in human PCa and non-cancerous prostate tissues was detected by immunohistochemistry, which was validated by microarray-based Taylor data at mRNA level. Then, the associations of PRC1 expression with clinicopathological features and clinical outcome of PCa patients were statistically analyzed.
RESULTS: PRC1 expression in PCa tissues, at both mRNA and protein levels, were significantly higher than those in non-cancerous prostate tissues. In addition, the PCa patients with PRC1 overexpression more frequently had high Gleason score, advanced pathological stage, positive metastasis, short overall survival time and positive PSA failure than those with low Gleason score, early pathological stage, negative metastasis, long overall survival time and negative PSA failure (all P<0.05). Moreover, PRC1 expression was identified as an unfavorable prognostic factor of biochemical recurrence-free survival in PCa patients (P<0.001).
CONCLUSION: These findings suggest that the aberrant expression of PRC1 may predict biochemical recurrence in men with PCa highlighting its potential as a prognostic marker of this malignancy.

Ma M, Zhao L, Sun G, et al.
Mda-7/IL-24 enhances sensitivity of B cell lymphoma to chemotherapy drugs.
Oncol Rep. 2016; 35(5):3122-30 [PubMed] Related Publications
Interleukin-24 (IL-24) is a cytokine encoded by a tumor suppressor gene of the IL-10 family, also known as the melanoma differentiation associated gene-7 (Mda-7) and first discovered in human melanoma cells. Mda-7/IL-24 has been shown to inhibit the proliferation of various human tumor cell lines, but its effect on the sensitivity of B cell lymphoma to chemotherapy agents is not yet clear. The present study investigated the effects of Mda-7/IL-24 overexpression on the sensitivity of human B cell lymphoma cells to chemotherapy, as well as its mechanism of action. The sensitivity of stable Mda-7/IL-24 overexpressing Raji and Daudi cells to cis-diamminedichloroplatinum (CDDP), epirubicin and vinblastine (VCR) were assessed by the MTS method, and the IC50 value calculated. Cell apoptosis and the intracellular accumulation of Rhodamine-123 were assayed by flow cytometry. The expression of multidrug resistance gene 1 (MDR1), B-cell-specific Moloney murine leukemia virus insertion site 1 (BMI1), topoisomerase II (Topo II) and multidrug resistance-related protein 1 (MRP1) mRNA and protein were analyzed by reverse transcription quantitative polymerase chain reaction (RT-qPCR) and western blotting, respectively. In addition, western blot analysis was also used to investigate the effect of Mda-7/IL-24 on activity of GTP-RhoA-ERK signaling pathway in Raji and Daudi cells. Growth inhibition and apoptosis rates of Mda-7/IL-24 overexpressing Raji and Daudi cells were higher than those of non-transfected cells and cells transfected with vector alone when treated with CDDP, epirubicin and VCR. The IC50 values of CDDP, epirubicin and VCR were lower for Mda-7/IL-24-overexpressing Raji and Daudi cells than for non-transfected cells and cells transfected with empty vector. Intracellular accumulation of Rhodamine-123 and the expression of Topo II were higher, while the levels of MDR1, BMI and MRP1 mRNA and protein were lower, in Mda-7/IL-24 overexpressing Raji and Daudi cells. Furthermore, the activities of GTP-RhoA-ERK signaling pathway in Raji and Daudi cells were suppressed. These results indicated that Mda-7/IL-24 enhanced the sensitivity of B lymphoma cells to chemotherapy agents by altering the expression of multidrug-resistance genes via downregulating GTP-RhoA-ERK signaling pathway, suggesting that treatment of B cell lymphomas with Mda-7/IL-24 could avoid MDR.

Clermont PL, Crea F, Chiang YT, et al.
Identification of the epigenetic reader CBX2 as a potential drug target in advanced prostate cancer.
Clin Epigenetics. 2016; 8:16 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: While localized prostate cancer (PCa) can be effectively cured, metastatic disease inevitably progresses to a lethal state called castration-resistant prostate cancer (CRPC). Emerging evidence suggests that aberrant epigenetic repression by the polycomb group (PcG) complexes fuels PCa progression, providing novel therapeutic opportunities.
RESULTS: In the search for potential epigenetic drivers of CRPC, we analyzed the molecular profile of PcG members in patient-derived xenografts and clinical samples. Overall, our results identify the PcG protein and methyl-lysine reader CBX2 as a potential therapeutic target in advanced PCa. We report that CBX2 was recurrently up-regulated in metastatic CRPC and that elevated CBX2 expression was correlated with poor clinical outcome in PCa cohorts. Furthermore, CBX2 depletion abrogated cell viability and induced caspase 3-mediated apoptosis in metastatic PCa cell lines. Mechanistically explaining this phenotype, microarray analysis in CBX2-depleted cells revealed that CBX2 controls the expression of many key regulators of cell proliferation and metastasis.
CONCLUSIONS: Taken together, this study provides the first evidence that CBX2 inhibition induces cancer cell death, positioning CBX2 as an attractive drug target in lethal CRPC.

Li XD, Chen SL, Dong P, et al.
Overexpression of RNF2 Is an Independent Predictor of Outcome in Patients with Urothelial Carcinoma of the Bladder Undergoing Radical Cystectomy.
Sci Rep. 2016; 6:20894 [PubMed] Free Access to Full Article Related Publications
RNF2 (ring finger protein 2) is frequently overexpressed in several types of human cancer, but the status of RNF2 amplification and expression in urothelial carcinoma of the bladder (UCB) and its clinical/prognostic significance is unclear. In this study, immunohistochemical analysis and fluorescence in situ hybridization (FISH) were used to examine the expression and amplification of RNF2 in 184 UCB patients after radical cystectomy. Overexpression of RNF2 was observed in 44.0% of UCBs and was found to significantly associate with shortened overall and cancer-specific survival (P < 0.001). In different subsets of UCBs, RNF2 overexpression was also identified as a prognostic indicator in patients with pT1, pT2, pN(-), and/or negative surgical margins (P < 0.05). Importantly, RNF2 overexpression together with pT status and surgical margin status provided significant independent prognostic parameters in multivariate analysis (P < 0.01). FISH results showed amplification of RNF2 in 8/79 (10.1%) of informative UCB cases. Additionally, RNF2 overexpression was significantly associated with RNF2 gene amplification (P = 0.004) and cell proliferation (P = 0.003). These findings suggested that overexpression of RNF2, as examined by immunohistochemical analysis, might serve as a novel prognostic biomarker and potential therapeutic target for UCB patients who undergo radical cystectomy.

Zhang Y, Zhou SY, Yan HZ, et al.
miR-203 inhibits proliferation and self-renewal of leukemia stem cells by targeting survivin and Bmi-1.
Sci Rep. 2016; 6:19995 [PubMed] Free Access to Full Article Related Publications
Drug resistance is one of the leading causes of failed cancer therapy in the treatment of acute myeloid leukemia. Although the mechanisms of resistance are poorly understood, they may be related to the presence of leukemia stem cells (LSCs). Down-regulation of the miR-203 reportedly contributes to oncogenesis and chemo-resistance in multiple cancers. We found that miR-203 expression was down-regulated in CD34 + AML cells as compared with CD34- cells isolated from patients as well as in LSC-enriched (CD34 + CD38-) cell lines KG-1a or MOLM13. Additionally, re-expression of miR-203 led to decreased cell proliferation, self-renewal, and sphere formation in LSCs. Moreover, miR-203 was found to directly target the 3'un-translated regions of survivin and Bmi-1 mRNAs affecting proliferation and self-renewal in LSCs. In this study, we identified a novel miR-203/survivin/Bmi-1 axis involved in the regulation of biological properties of LSCs. This axis may represent a new therapeutic target for acute myeloid leukemia and a potential prognosis/diagnostic marker for LSCs therapy.

Ghalandary M, Behmanesh M, Sadeghizadeh M
Evaluating of suppressor of zeste 12 and chromobox homolog 8 genes expression showed two possible origins for gastric cancer development.
Indian J Cancer. 2015 Jan-Mar; 52(1):27-31 [PubMed] Related Publications
CONTEXT: Changes in genome, made by multiple genetic and epigenetic alterations result to the cancer initiation and progression. Suppressor of zeste 12 (SUZ12) and chromobox homolog 8 (CBX8) proteins are two components of epigenetic regulators that their function in the initiation and progression of cancers are not well-understood.
AIMS: The role of SUZ12 and its target CBX8 is examined.
SETTINGS AND DESIGN: Comparing the expression levels of SUZ12 and CBX8 between 30 gastric tumor and their marginal tissues.
MATERIALS AND METHODS: Quantitative reverse transcription polymerase chain reaction technique was performed.
STATISTICAL ANALYSIS: Statistical comparison was carried out using Statistical Program for Social Sciences software 16.0 (Released 2007, SPSS for Windows. SPSS Inc., Chicago, IL, USA) and (GraphPad Prism version 5 for Windows, GraphPad Software, La Jolla, California USA,
RESULTS: Despite the obvious differences in the expression of these genes in each sample for tumor and its marginal tissue, statistical analysis did not show significant differences in the mean of expression for SUZ12 and CBX8 genes in total. Due to the variation in expression levels, the samples could be divided into two groups for each gene; group 1, in which the genes were overexpressed in tumor and group 2, in which the genes were down regulated in tumor samples.
CONCLUSION: We found that in each group, the difference in the SUZ12 and CBX8 genes expression were significantly divergent between tumors and their marginal tissues. It means that the regulatory mechanisms involved in developing and controlling the process of gastric cancer pathogenesis is more complex than it thought. These results also bring new evidence on the possible double origin for gastric cancer development, bone-marrow-derived cells and tissue stem cells.

Yang F, Lv LZ, Cai QC, Jiang Y
Potential roles of EZH2, Bmi-1 and miR-203 in cell proliferation and invasion in hepatocellular carcinoma cell line Hep3B.
World J Gastroenterol. 2015; 21(47):13268-76 [PubMed] Free Access to Full Article Related Publications
AIM: To investigate the potential roles of enhancer of zeste homolog2 (EZH2), Bmi-1 and miR-203 in cell proliferation and invasion in hepatocellular carcinoma (HCC) cell line Hep3B.
METHODS: A total of 73 patients who underwent surgical resection at Fuzong Clinical Medical College of Fujian Medical University were enrolled in this study. Hep3B cells were cultivated in RPMI 1640 medium supplemented with 10% fetal bovine serum at 37 °C. Vectors that containing cDNA of the EZH2 gene or miR-203 targeted shRNA plasmid were constructed, and then transfected into Hep3B cells. The mRNA expression of miR-203, EZH2, and Bmi-1 was analyzed using quantitative real-time polymerase chain reaction analysis, and the protein levels of EZH2 and Bmi-1 were detected by Western blot analysis. Effect of EZH2 or miR-203 on cell proliferation was observed by methyl thiazolyl tetrazolium assay, and cell apoptosis was assessed using flow cytometry. Besides, effect of EZH2 or miR-203 on tumor cell invasion was detected using Transwell assay.
RESULTS: The mRNA levels of EZH2 and Bmi-1 in HCC tissues and in Hep3B cells were significantly higher compared with those in normal samples (P < 0.01), while miR-203 level was significantly lower in HCC tissues (P < 0.01). Hep3B cells transfected with EZH2-shRNA or miR-203-shRNA showed lower expression levels of EZH2 and Bmi-1 (P < 0.05). Compared with controls, Hep3B cells transfected with EZH2-shRNA had relative slow cell proliferation, indicating that low expression of EZH2 and Bmi-1 and overexpression of miR-203 could inhibit Hep3B cell proliferation (P < 0.05). The average apoptosis rate of Hep3B cells transfected with EZH2-shRNA vector was about 18.631%, while that of Hep3B cells transfected with shRNA vector was about 5.33%, suggesting that EZH2 was down-regulated by transfecting with EZH2-shRNA, and the down-regulated EZH2 contributed to the cell apoptosis. Low expression of EZH2 and Bmi-1 and overexpression of miR-203 could reduce Hep3B cell invasion (P < 0.05).
CONCLUSION: Our study suggests that EZH2 and Bmi-1 are up-regulated while miR-203 is down-regulated in Hep3B cells. MiR-203 may contribute to the metastasis and enhance apoptosis of HCC cells by regulating EZH2 and Bmi-1. Our study may provide a theoretical basis for metastasis of HCC and targeted therapy of HCC.

Sibin MK, Lavanya CH, Bhat DI, et al.
CD133 and BMI1 expressions and its prognostic role in primary glioblastoma.
J Genet. 2015; 94(4):689-96 [PubMed] Related Publications
Glioblastoma is the most common malignant brain tumour, generated by bulk of malignant cancer stem cells, which express various stem cell factors like CD133, BMI1 and nestin. There are several studies which show the importance of CD133 in cancer, but the function and interaction with other major oncogenes and tumour suppressor genes is still not understood. This study aimed to analyse the expression of CD133 mRNA and its correlations with BMI1 protein expression and TP53 mutations in newly diagnosed glioblastoma patients and its role in prognosis. Overexpression of CD133 mRNA and BMI1 protein was found in 47.6 and 76.2% patients respectively and TP53 mutations was seen in 57.1% of patients in our study.There was no correlation among TP53 mutations and expressions of CD133 and BMI1. We found that high level of BMI1 expression was favourable for the patient survival (P=0.0075) and high CD133 mRNA expression was unfavourable for the patient survival (P=0.0226).CD133 mRNA and BMI1 protein expression could independently predict the glioblastoma patient survival in multivariate analysis. In conclusion, the overexpression of these stem cell markers is a common event in glioblastoma progression and could be used as potential prognostic markers.

Ferretti R, Bhutkar A, McNamara MC, Lees JA
BMI1 induces an invasive signature in melanoma that promotes metastasis and chemoresistance.
Genes Dev. 2016; 30(1):18-33 [PubMed] Free Access to Full Article Related Publications
Melanoma can switch between proliferative and invasive states, which have identifying gene expression signatures that correlate with good and poor prognosis, respectively. However, the mechanisms controlling these signatures are poorly understood. In this study, we identify BMI1 as a key determinant of melanoma metastasis by which its overexpression enhanced and its deletion impaired dissemination. Remarkably, in this tumor type, BMI1 had no effect on proliferation or primary tumor growth but enhanced every step of the metastatic cascade. Consistent with the broad spectrum of effects, BMI1 activated widespread gene expression changes, which are characteristic of melanoma progression and also chemoresistance. Accordingly, we showed that up-regulation or down-regulation of BMI1 induced resistance or sensitivity to BRAF inhibitor treatment and that induction of noncanonical Wnt by BMI1 is required for this resistance. Finally, we showed that our BMI1-induced gene signature encompasses all of the hallmarks of the previously described melanoma invasive signature. Moreover, our signature is predictive of poor prognosis in human melanoma and is able to identify primary tumors that are likely to become metastatic. These data yield key insights into melanoma biology and establish BMI1 as a compelling drug target whose inhibition would suppress both metastasis and chemoresistance of melanoma.

Lin X, Ojo D, Wei F, et al.
A Novel Aspect of Tumorigenesis-BMI1 Functions in Regulating DNA Damage Response.
Biomolecules. 2015; 5(4):3396-415 [PubMed] Free Access to Full Article Related Publications
BMI1 plays critical roles in maintaining the self-renewal of hematopoietic, neural, intestinal stem cells, and cancer stem cells (CSCs) for a variety of cancer types. BMI1 promotes cell proliferative life span and epithelial to mesenchymal transition (EMT). Upregulation of BMI1 occurs in multiple cancer types and is associated with poor prognosis. Mechanistically, BMI1 is a subunit of the Polycomb repressive complex 1 (PRC1), and binds the catalytic RING2/RING1b subunit to form a functional E3 ubiquitin ligase. Through mono-ubiquitination of histone H2A at lysine 119 (H2A-K119Ub), BMI1 represses multiple gene loci; among these, the INK4A/ARF locus has been most thoroughly investigated. The locus encodes the p16INK4A and p14/p19ARF tumor suppressors that function in the pRb and p53 pathways, respectively. Its repression contributes to BMI1-derived tumorigenesis. BMI1 also possesses other oncogenic functions, specifically its regulative role in DNA damage response (DDR). In this process, BMI1 ubiquitinates histone H2A and γH2AX, thereby facilitating the repair of double-stranded DNA breaks (DSBs) through stimulating homologous recombination and non-homologous end joining. Additionally, BMI1 compromises DSB-induced checkpoint activation independent of its-associated E3 ubiquitin ligase activity. We review the emerging role of BMI1 in DDR regulation and discuss its impact on BMI1-derived tumorigenesis.

Mayr C, Wagner A, Loeffelberger M, et al.
The BMI1 inhibitor PTC-209 is a potential compound to halt cellular growth in biliary tract cancer cells.
Oncotarget. 2016; 7(1):745-58 [PubMed] Free Access to Full Article Related Publications
BMI1 is a core component of the polycomb repressive complex 1 (PRC1) and is up-regulated in biliary tract cancer (BTC), contributing to aggressive clinical features. In this study we investigated the cytotoxic effects of PTC-209, a recently developed inhibitor of BMI1, in BTC cells. PTC-209 reduced overall viability in BTC cell lines in a dose-dependent fashion (0.04 - 20 µM). Treatment with PTC-209 led to slightly enhanced caspase activity and stop of cell proliferation. Cell cycle analysis revealed that PTC-209 caused cell cycle arrest at the G1/S checkpoint. A comprehensive investigation of expression changes of cell cycle-related genes showed that PTC-209 caused significant down-regulation of cell cycle-promoting genes as well as of genes that contribute to DNA synthesis initiation and DNA repair, respectively. This was accompanied by significantly elevated mRNA levels of cell cycle inhibitors. In addition, PTC-209 reduced sphere formation and, in a cell line-dependent manner, aldehyde dehydrogease-1 positive cells. We conclude that PTC-209 might be a promising drug for future in vitro and in vivo studies in BTC.

Xu X, Liu Y, Su J, et al.
Downregulation of Bmi-1 is associated with suppressed tumorigenesis and induced apoptosis in CD44⁺ nasopharyngeal carcinoma cancer stem-like cells.
Oncol Rep. 2016; 35(2):923-31 [PubMed] Related Publications
Bmi-1 (B-cell-specific Moloney murine leukemia virus insertion site 1) is a member of the Polycomb group gene (PcG) family, which is involved in the proliferation, migration and tumorigenesis of several types of cancer stem cells (CSCs). However, its precise role and mechanism in CD44+ nasopharyngeal carcinoma (NPC) cancer stem-like cells (CSC-LCs) remain poorly understood. In our previous study, we successfully silenced Bmi-1 by short hairpin RNA (shRNA) in CD44+ NPC CSC-LCs and obtained stable Bmi-1 knockdown (KD) cell lines. In the present study, we tested the cell proliferation by CCK-8 assay and apoptosis by flow cytometry. Scratch wound healing assay, together with Transwell migration and invasion assays were used to measure the migration and invasion capacity. We further evaluated the tumorigenicity of CD44+ NPC CSC-LCs transfected with Bmi-1 shRNA in vivo. Based on our results, knockdown of Bmi-1 by shRNA resulted in the inhibition of tumor proliferation, migration and invasion in vitro, followed by cell apoptosis. In addition, our results preliminarily demonstrated that inhibition of Bmi-1 expression by shRNA increased tumor apoptosis through the p16INK4a-p14ARF-p53 pathway. Bmi-1 silencing in CD44+ NPC CSC-LCs also resulted in the failure to develop tumors in vivo. These results provide important insights into the role of Bmi-1 in the occurrence and development of NPC. Based on our findings, regulation of Bmi-1 in CD44+ NPC CSC-LCs may provide a potential molecular target for the therapy of NPC, and targeted silencing of Bmi-1 by shRNA may have clinical future implications in NPC therapy.

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