[Show abstract][Hide abstract] ABSTRACT: Background
Transcription factor Sp1 is multifaceted, with the ability to function as an oncogene or a tumor suppressor, depending on the cellular context. We previously reported that Sp1 is required for the transcriptional activation of the key oncogenes in nasopharyngeal carcinoma (NPC), including B-lymphoma mouse Moloney leukemia virus insertion region 1 (Bmi1) and centromere protein H (CENPH), but the role of Sp1 and its underlying mechanisms in NPC remained largely unexplored. The objective of this study was to investigate the cellular function of Sp1 and to verify the clinical significance of Sp1 as a potential therapeutic target in NPC.Methods
The levels of Sp1 in the normal primary nasopharyngeal epithelial cells (NPECs) and NPC cell lines were analyzed by Quantitative Real-time RT-PCR (qRT-PCR) and Western blot. The location and expression of Sp1 in the NPC tissues were detected by immunohistochemistry staining (IHC). The effect of Sp1 knockdown on the cell proliferation, clonogenicity, anchorage-independent growth and the stem-cell like phenotype in NPC cells were evaluated by MTT, flow cytometry, clonogenicity analysis and sphere formation assay.ResultsThe mRNA and protein levels of Sp1 were elevated in NPC cell lines than in the normal primary NPECs. Higher expression of Sp1 was found in NPC tissues with advanced clinical stage (P¿=¿0.00036). Either inhibition of Sp1 activity by mithramycin A, the FDA-approved chemotherapeutic anticancer drug or Sp1 silencing by two distinct siRNA against Sp1 suppressed the growth of NPC cells. Mechanism analysis revealed that Sp1 silencing may suppress cell proliferation, clonogenicity, anchorage-independent growth and the stem-cell like phenotype through inducing the expression of p27 and p21, and impairing the expressions of the critical stem cell transcription factors (SCTFs), including Bmi1, c-Myc and KLF4 in NPC cells.Conclusions
Sp1 was enriched in advanced NPC tissues and silencing of Sp1 significantly inhibited cell proliferation, clonogenicity, anchorage-independent growth and the stem-cell like phenotype of NPC cells, suggesting Sp1 may serve as an appealing drug target for NPC.
Journal of Translational Medicine 08/2014; 12(1):222. · 3.99 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Longikaurein A is a natural ent-kaurene diterpenoid isolated from Isodon genus. The ent-kaurene diterpenoids isolated from medicinal plants have been shown to have anti-disease effects. The present study was designed to examine the anti-tumour effects of longikaurin A (LK-A) in nasopharyngeal carcinoma in vitro and in vivo.
Apoptosis and cell cycle arrest were determined by flow cytometry analysis of the cells treated with Longikaurein A. The proteins of apoptosis signaling pathway were detected by western blotting analysis. Finally, we examined whether LK-A exhibits anti-tumour activity in xenograft models.
Longikaurin A inhibited the cell growth by inducing apoptosis and cell cycle arrest. At low concentrations, longikaurin A induced S phase arrest and at higher concentrations, longikaurin A induced caspase-dependent apoptosis by regulating apoptotic molecules. Finally, longikaurin A significantly inhibited the tumour growth of CNE2 xenografts in vivo and showed no obvious effect on the body weights of the mice.
Our results suggest that Longikaurin A exhibited anti-tumour activity in nasopharyngeal carcinoma in vitro and in vivo.
Journal of Translational Medicine 08/2013; 11(1):200. · 3.99 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Bmi1, a member of the polycomb group, is elevated and involved in the pathogenesis of various aggressive cancers, including nasopharyngeal carcinoma (NPC). To date, the mechanisms underlying the high expression of Bmi1 in NPC remain obscure. To gain new insights into the transcriptional regulation of BMI1, we cloned and characterized the promoter region of BMI1. Luciferase reporter assays demonstrated that the region from -783 to +375 exhibited significant promoter activity. Using a series of 5' and 3' deletion promoter constructs in luciferase reporter assays, the regions +167/+232 and -536/-134 were found to be sufficient for full promoter activity. Transcriptional activity of the BMI1 promoter was dependent on the Sp1 binding sites cluster (+181/+214) as well as the E-box elements (-181) and was abolished after mutation of the two cis-elements. Electrophoretic mobility shift assays and chromatin immunoprecipitation assays demonstrated that Sp1 bound to the region from +181 to +214 within the BMI1 promoter. In addition, gain- and loss-of-function analyses revealed that Sp1 augmented Bmi1 expression. Further investigations using immunohistochemistry and qRT-PCR disclosed a significant positive correlation between the expression of Sp1 and Bmi1 in NPEC/NPC cells and NPC tissue specimens. In addition, Myc, the known transcription factor for BMI1 in neuroblastomas, also activated the transcription of BMI1 through binding to the E-box element (-181) within its promoter, and showed a positive correlation with the mRNA level of BMI1 in NPC. In conclusion, these findings provide valuable mechanistic insights into the role of Sp1 and c-Myc on BMI1 transcription in NPC, suggesting that targeting Sp1 or c-Myc may be a potential therapeutic strategy for NPC. This article is protected by copyright. All rights reserved.
[Show abstract][Hide abstract] ABSTRACT: Background: The aim of this study is to explore the expression of beclin 1, an autophagy gene, in bladder cancer and to evaluate its clinical and prognostic significance in patients with bladder cancer. Methods: Beclin 1 expression was examined at mRNA and protein levels by real-time quantitative polymerase chain reaction (RT-PCR), Western blotting, and immunohistochemistry in bladder cancer tissues and adjacent normal bladder tissues. The relationship between the expression of beclin 1 and clinicopathological characteristics and prognosis was statistically analyzed. Results: mRNA level, protein expression and immunoreactivity of beclin 1 were decreased in bladder cancer tissues compared with adjacent normal tissues. Downregulation of beclin 1 was more frequent in tumors with higher histological grades (the expression of beclin 1 was reduced by 49.0% in G1 and G2, and by 71.8% in G3, p=0.010), and was also reduced by 69.5% in the muscle invasive type and by 51.1% in the non-muscle invasive type (p=0.04). Reduced beclin 1 expression was positively associated with higher histological grade and more advanced clinical stage (p<0.05). Kaplan-Meier survival analysis revealed that patients exhibiting lower beclin 1 expression experienced a shorter survival than those with higher expression (p=0.006). Cox proportional hazards regression analysis showed that beclin 1 protein is an independent predictor of survival (p=0.005). Conclusion: Beclin 1 has an influence on the progression of bladder cancer and might serve as a potential prognostic factor for patients with bladder cancer.
The International journal of biological markers 11/2012; · 1.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The overexpression of centromere protein H (CENPH), one of the fundamental components of the human active kinetochore, has been shown to be closely associated with human cancers. However, the mechanism of its transcriptional regulation has not been reported. The aim of the present study was to investigate the regulatory elements for the transcriptional regulation of CENPH in nasopharyngeal carcinoma cells. To characterize the CENPH promoter and identify regulatory elements, we cloned 1015 bp (-975/+40 bp) of the 5'-flanking region of the CENPH gene from immortalized normal nasopharyngeal epithelial cells (Bmi-1/NPEC). Functional analysis established a minimal region (-140/-87 bp) involved in the regulation of human CENPH promoter activity. Through site-directed mutagenesis, a transactivation assay, chromatin immunoprecipitation, and electrophoretic mobility shift assay, we found that the Sp1/Sp3 transcription factors could bind to the CENPH promoter in vitro and in vivo, and that they regulated CENPH promoter activation in human nasopharyngeal carcinoma cells. Furthermore, Sp1 and Sp3 were highly expressed in nasopharyngeal carcinoma cells. Knockdown of Sp1 and Sp3 by small interfering RNA or inhibition of Sp1 and Sp3 activity by mithramycin A decreased CENPH mRNA expression, whereas the exogenous expression of Sp1 and Sp3 upregulated CENPH mRNA expression. Taken together, our results indicate that Sp1 and Sp3 bind to the CENPH minimal promoter and function as a regulator of the transcription of CENPH in human nasopharyngeal carcinomas.