Down-regulation of BMI-1 cooperates with artemisinin on growth inhibition of nasopharyngeal carcinoma cells

The Crucial Roles of Bmi-1 in Cancer: Implications in Pathogenesis, Metastasis, Drug Resistance, and Targeted Therapies

B-cell-specific Moloney murine leukemia virus integration region 1 (Bmi-1, also known as RNF51 or PCGF4) is one of the important members of the PcG gene family, and is involved in regulating cell proliferation, differentiation and senescence, and maintaining the self-renewal of stem cells. Many studies in recent years have emphasized the role of Bmi-1 in the occurrence and development of tumors. In fact, Bmi-1 has multiple functions in cancer biology and is closely related to many classical molecules, including Akt, c-MYC, Pten, etc. This review summarizes the regulatory mechanisms of Bmi-1 in multiple pathways, and the interaction of Bmi-1 with noncoding RNAs. In particular, we focus on the pathological processes of Bmi-1 in cancer, and explore the clinical relevance of Bmi-1 in cancer biomarkers and prognosis, as well as its implications for chemoresistance and radioresistance. In conclusion, we summarize the role of Bmi-1 in tumor progression, reveal the pathophysiological process and molecular mechanism of Bmi-1 in tumors, and provide useful information for tumor diagnosis, treatment, and prognosis.

Artemisinins in Combating Viral Infections Like SARS-CoV-2, Inflammation and Cancers and Options to Meet Increased Global Demand

Artemisinin is a natural bioactive sesquiterpene lactone containing an unusual endoperoxide 1, 2, 4-trioxane ring. It is derived from the herbal medicinal plant Artemisia annua and is best known for its use in treatment of malaria. However, recent studies also indicate the potential for artemisinin and related compounds, commonly referred to as artemisinins, in combating viral infections, inflammation and certain cancers. Moreover, the different potential modes of action of artemisinins make these compounds also potentially relevant to the challenges the world faces in the COVID-19 pandemic. Initial studies indicate positive effects of artemisinin or Artemisia spp. extracts to combat SARS-CoV-2 infection or COVID-19 related symptoms and WHO-supervised clinical studies on the potential of artemisinins to combat COVID-19 are now in progress. However, implementing multiple potential new uses of artemisinins will require effective solutions to boost production, either by enhancing synthesis in A. annua itself or through biotechnological engineering in alternative biosynthesis platforms. Because of this renewed interest in artemisinin and its derivatives, here we review its modes of action, its potential application in different diseases including COVID-19, its biosynthesis and future options to boost production.

Screening study of cancer-related cellular signals from microbial natural products

To identify bioactive natural products from various natural resources, such as plants and microorganisms, we investigated programs to screen for compounds that affect several cancer-related cellular signaling pathways, such as BMI1, TRAIL, and Wnt. This review summarizes the results of our recent studies, particularly those involving natural products isolated from microbial resources, such as actinomycetes, obtained from soil samples collected primarily around Chiba, Japan.

Artemisinins as a novel anti-cancer therapy: Targeting a global cancer pandemic through drug repurposing

Artemisinins are a unique class of antimalarial drugs with significant potential for drug repurposing for a wide range of diseases including cancer. Cancer is a leading cause of death globally and the majority of cancer related deaths occur in Low and Middle Income Countries (LMICs) where conventional treatment options are often limited by financial cost. Drug repurposing can significantly shorten new therapeutic discovery pathways, ensuring greater accessibility and affordability globally. Artemisinins have an excellent safety and tolerability profile as well as being affordable for deployment in Low and Middle Class Income Countries at around USD1 per daily dose. Robust, well designed clinical trials of artemisinin drug repurposing are indicated for a variety of different cancers and treatment settings.

Combination Therapies of Artemisinin and its Derivatives as a Viable Approach for Future Cancer Treatment

BACKGROUND

Many anticancer drugs have been developed for clinical usage till now, but the major problem is the development of drug-resistance over a period of time in the treatment of cancer. Anticancer drugs produce huge adverse effects, ultimately leading to death of the patient. Researchers have been focusing on the development of novel molecules with higher efficacy and lower toxicity; the anti-malarial drug artemisinin and its derivatives have exhibited cytotoxic effects.

METHODS

We have done extensive literature search for artemisinin for its new role as anti-cancer agent for future treatment. Last two decades papers were referred for deep understanding to strengthen its role.

RESULT

Literature shows changes at 9, 10 position in the artemisinin structure produces anticancer activity. Artemisinin shows anticancer activity in leukemia, hepatocellular carcinoma, colorectal and breast cancer cell lines. Artemisinin and its derivatives have been studied as combination therapy with several synthetic compounds, RNA interfaces, recombinant proteins and antibodies etc., for synergizing the effect of these drugs. They produce an anticancer effect by causing cell cycle arrest, regulating signaling in apoptosis, angiogenesis and cytotoxicity activity on the steroid receptors. Many novel formulations of artemisinin are being developed in the form of carbon nanotubes, polymer-coated drug particles, etc., for delivering artemisinin, since it has poor water/ oil solubility and is chemically unstable.

CONCLUSION

We have summarize the combination therapies of artemisinin and its derivatives with other anticancer drugs and also focussed on recent developments of different drug delivery systems in the last 10 years. Various reports and clinical trials of artemisinin type drugs indicated selective cytotoxicity along with minimal toxicity thus projecting them as promising anti-cancer agents in future cancer therapies.

Potential applications of artemisinins in ocular diseases

Artemisinin, also named qinghaosu, is a family of sesquiterpene trioxane lactone originally derived from the sweet wormwood plant (Artemisia annua), which is a traditional Chinese herb that has been universally used as anti-malarial agents for many years. Evidence has accumulated during the past few years which demonstrated the protective effects of artemisinin and its derivatives (artemisinins) in several other diseases beyond malaria, including cancers, autoimmune disorders, inflammatory diseases, viral and other parasite-related infections. Recently, this long-considered anti-malarial agent has been proved to possess anti-oxidant, anti-inflammatory, anti-apoptotic and anti-excitotoxic properties, which make it a potential treatment option for the ocular environment. In this review, we first described the overview of artemisinins, highlighting the activity of artemisinins to other diseases beyond malaria and the mechanisms of these actions. We then emphasized the main points of published results of using artemisinins in targeting ocular disorders, including uveitis, retinoblastoma, retinal neurodegenerative diseases and ocular neovascularization. To conclude, we believe that artemisinins could also be used as a promising therapeutic drug for ocular diseases, especially retinal vascular diseases in the near future.

Aberrantly elevated Bmi1 promotes cervical cancer tumorigenicity and tumor sphere formation via enhanced transcriptional regulation of Sox2 genes

The exact molecular mechanisms underlying cervical tumorigenesis are poorly understood. Polycomb complex protein Bmi1 (Bmi1) is involved in the malignant transformation and biological aggressiveness of several human carcinomas. Therefore, the present study assessed the expression of Bmi1 protein in human cervical cancer tissues and examined the mechanisms involved in cervical carcinogenesis. The expression of Bmi1 protein was examined by immunohistochemistry in cervical carcinoma tissues (n=71), high-grade squamous intraepithelial lesions (n=41) and normal cervical tissues (n=47). Expression of Bmi1 protein gradually increased across samples from the normal cervix (1/47; 2.12%), high-grade squamous intraepithelial lesions (5/42; 16.13%) and cervical carcinomas (31/71; 43.66%; P<0.05). Additionally, Bmi1 protein expression was associated with tumor histopathological grade. The effects of Bmi1 silencing and overexpression on tumor sphere formation and the tumorigenicity of cervical cancer cells were investigated. Overexpression of Bmi1 resulted in significantly attenuated tumor formation and tumor sphere formation. Consistently, Bmi1 silencing significantly inhibited tumor formation and tumor sphere formation. Furthermore, Bmi1 upregulated the expression of Sox2, and the dual-luciferase reporter assay and chromatin immunoprecipitation showed that Bmi1 transactivated Sox2 by binding to the two E-box motifs in the Sox2 promoter. In conclusion, aberrantly elevated Bmi1 promotes cervical cancer tumorigenicity and tumor sphere formation via enhanced transcriptional regulation of Sox2 genes as a potential oncogenic factor that participates in the carcinogenesis of cervical carcinomas.

More insights into the pharmacological effects of artemisinin

Artemisinin is one of the most widely prescribed drugs against malaria and has recently received increased attention because of its other potential biological effects. The aim of this review is to summarize recent discoveries of the pharmaceutical effects of artemisinin in basic science along with its mechanistic action, as well as the intriguing results of recent clinical studies, with a focus on its antitumor activity. Scientific evidence indicates that artemisinin exerts its biological activity by generating reactive oxygen species that damage the DNA, mitochondrial depolarization, and cell death. In the present article review, scientific evidence suggests that artemisinin is a potential therapeutic agent for various diseases. Thus, this review is expected to encourage interested scientists to conduct further preclinical and clinical studies to evaluate these biological activities.

O-GlcNAcylation modulates Bmi-1 protein stability and potential oncogenic function in prostate cancer

The Polycomb group transcriptional repressor Bmi-1 often overexpressed and participated in stem cells self-renewal and tumorigenesis initiating of prostate cancer. In this progression, Bmi-1 protein was regulated by transcription and post-translational modifications (PTMs). Nobly, the underlying PTMs regulation of Bmi-1 is poorly known. Here we use co-immunoprecipitation show that in C4-2 cell line, Bmi-1 directly interacted with OGT which is the only known enzyme catalyzed the O-GlcNAcylation in human. Furthermore, we identified that Ser255 is the site for Bmi-1 O-GlcNAcylation, and O-GlcNAcylation promoted Bmi-1 protein stability and its oncogenic activity. Finally, microarray analysis has characterized potential oncogenes associated pathway subject to repression via the OGT-Bmi-1 axis. Taken together, these results indicate that OGT-mediated O-GlcNAcylation at Ser255 stabilizes Bmi-1 and hence inhibits the TP53, PTEN and CDKN1A/CDKN2A pathway. The study not only uncovers a novel functional PTMs of Bmi-1 but also reveals a unique oncogenic role of O-GlcNAcylation in prostate cancer.

Silencing BMI1 radiosensitizes human breast cancer cells by inducing DNA damage and autophagy

Overexpression of BMI1 in human cancer cells, a member of the polycomb group of repressive complexes, correlates with advanced stage of disease, aggressive clinico-pathological behavior, poor prognosis, and resistance to radiation and chemotherapy. Studies have shown that experimental reduction of BMI1 protein level in tumor cells results in inhibition of cell proliferation, induction of apoptosis and/or senescence, and increased susceptibility to cytotoxic agents and radiation therapy. Although a role for BMI1 in cancer progression and its importance as a molecular target for cancer therapy has been established, information on the impact of silencing BMI1 in triple-negative breast cancer (TNBC) and its consequence on radiotherapy have not been well studied. Therefore, in the present study we investigated the potential therapeutic benefit of radiation therapy in BMI1-silenced breast cancer cells and studied the mechanism(s) of radiosensitization. Human MDA-MB-231 and SUM159PT breast cancer cells that were either stably transfected with a lentiviral vector expressing BMI1 shRNA (shBMI1) or control shRNA (shControl) or transient transfection with a BMI1-specific siRNA were used. Silencing of BMI1 resulted in marked reduction in BMI1 both at the mRNA and protein level that was accompanied by a significant reduction in cell migration compared to control cells. Further, BMI1 knockdown produced a marked enhancement of DNA damage as evidenced by Comet Assay and γH2AX foci, resulting in a dose-dependent radiosensitization effect. Molecular studies revealed modulation of protein expression that is associated with the DNA damage response (DDR) and autophagy pathways. Our results demonstrate that BMI1 is an important therapeutic target in breast cancer and suppression of BMI1 produces radiation sensitivity. Further, combining BMI1-targeted therapeutics with radiation might benefit patients diagnosed with TNBC.

MicroRNA-194 represses glioma cell epithelial‑to‑mesenchymal transition by targeting Bmi1

MicroRNA-194 (miR-194) is frequently dysregulated in many types of cancer. However, the function of miR-194 in glioma remains unknown. In the present study, we aimed to investigate the biological functions of miR-194 in glioma and the potential molecular mechanism of miR-194 involved in glioma progression. We found that miR-194 expression was significantly reduced in glioma specimens and cell lines, as detected by real-time quantitative polymerase chain reaction (RT-qPCR) analysis. The overexpression of miR-194 inhibited while the suppression of miR-194 promoted cell migration, invasion and epithelial mesenchymal transition (EMT) in glioma cells. Bioinformatics analysis showed that the B cell-specific moloney murine leukemia virus insertion site 1 (Bmi1) was a direct target of miR-194, which was validated by dual-luciferase reporter assay, RT-qPCR and western blot analysis. The restoration of Bmi1 expression significantly abrogated the suppressive effect of miR-194 on glioma cell EMT. Taken together, the present study suggests that miR-194 inhibits glioma cell EMT by targeting Bmi1 providing novel insights into understanding the pathogenesis of glioma. The restoration of miR-194 may be a potential therapeutic strategy for glioma treatment.

Sonic Hedgehog Signaling in Thyroid Cancer

Thyroid cancer is the most common malignancy of the endocrine system. The initiation of thyroid cancer is often triggered by a genetic mutation in the phosphortidylinositol-3 kinase (PI3K) or mitogen-activated protein kinase (MAPK) pathway, such as RAS and BRAF, or by the rearrangement of growth factor receptor tyrosine kinase genes such as RET/PTC. The sonic hedgehog (Shh) pathway is evolutionarily conserved and plays an important role in the embryonic development of normal tissues and organs. Gene mutations in the Shh pathway are involved in basal cell carcinomas (BCC). Activation of the Shh pathway due to overexpression of the genes encoding the components of this pathway stimulates the growth and spread of a wide range of cancer types. The Shh pathway also plays an important role in cancer stem cell (CSC) self-renewal. GDC-0449 and LDE-225, two inhibitors of this pathway, have been approved for treating BCC and are being tested as a single agent or in combination with other drugs for treating various other cancers. Here, we review the recent findings on activation of the Shh pathway in thyroid cancer and its role in maintaining thyroid CSC self-renewal. We also summarize the recent developments on crosstalk of the Shh pathway with the MAPK and PI3K oncogenic pathways, and its implications for combination therapy.

Expression of B cell-specific Moloney murine leukemia virus integration site 1 in vulvar squamous cell carcinoma and its effect on the biological behavior of A-431 cells

The aim of the present study was to investigate the expression of B cell-specific Moloney murine leukemia virus integration site 1 (BMI-1) in vulvar squamous cell carcinoma (VSCC) and vulvar intraepithelial neoplasia (VIN). Furthermore, the present study investigated the effects of BMI-1 expression on the biological behavior of A-431 human epidermoid carcinoma cells. BMI-1 expression in human VSCC and VIN tissues was detected using immunohistochemistry. Subsequently, BMI-1 expression was silenced in A-431 cells using small interfering RNA (siRNA), and BMI-1 expression was detected using reverse transcription-quantitative polymerase chain reaction and western blotting. The effects of BMI-1 silencing on cell proliferation, apoptosis and invasive ability were determined using an MTT assay, Annexin V-fluorescein isothiocyanate/propidium iodide double-labeling experiment and Transwell assay, respectively. The expression rate of BMI-1 in normal vulvar, VIN and VSCC tissues was 0.0, 25.0 and 68.0% respectively, demonstrating an increasing trend in the severity of the disease. BMI-1 overexpression was found not to correlate with age, pathological stage, lymph node metastasis or degree of differentiation (P>0.05). BMI-1 siRNA transfection effectively inhibited BMI-1 messenger RNA and protein expression in A-431 cells. The mean rate of apoptosis promotion and proliferation inhibition in the most effectively silenced group were 20.19 and 46.82%, respectively, which was significantly higher than that of the cells in the blank and control siRNA groups (P<0.05). The number of invading cells was decreased in the most effectively silenced group compared with that of the blank and control siRNA groups. Abnormal expression of BMI-1 was also detected in VIN and VSCC tissues, and targeting of BMI-1 with siRNA was able to successfully silence BMI-1 expression in A-431 cells. Silencing of BMI-1 promoted apoptosis and inhibited the invasive abilities of A-431 cells in vitro.

Targeting self-renewal pathways in cancer stem cells: clinical implications for cancer therapy

Extensive cancer research in the past few decades has identified the existence of a rare subpopulation of stem cells in the grove of cancer cells. These cells are known as the cancer stem cells marked by the presence of surface biomarkers, multi-drug resistance pumps and deregulated self-renewal pathways (SRPs). They have a crucial role in provoking cancer cells leading to tumorigenesis and its progressive metastasis. Cancer stem cells (CSCs) are much alike to normal stem cells in their self-renewal mechanisms. However, deregulations in the SRPs are seen in CSCs, making them resistant to conventional chemotherapeutic agents resulting in the tumor recurrence. Current treatment strategies in cancer fail to detect and differentiate the CSCs from their non-tumorigenic progenies owing to absence of specific biomarkers. Now, it has become imperative to understand complex functional biology of CSCs, especially the signaling pathways to design improved treatment strategies to target them. It is hopeful that the SRPs in CSCs offer a promising target to alter their survival strategies and impede their tumorigenic potential. However, there are many perils associated with the direct targeting method by conventional therapeutic agents such as off targets, poor bioavailability and poor cellular distribution. Recent evidences have shown an increased use of small molecule antagonists directly to target these SRPs may lead to severe side-effects. An alternative to solve these issues could be an appropriate nanoformulation. Nanoformulations of these molecules could provide an added advantage for the selective targeting of the pathways especially Hedgehog, Wnt, Notch and B-cell-specific moloney murine leukemia virus integration site 1 in the CSCs while sparing the normal stem cells. Hence, to achieve this goal a complete understanding of the molecular pathways corroborate with the use of holistic nanosystem (nanomaterial inhibition molecule) could possibly be an encouraging direction for future cancer therapy.

Effect of shRNA-Mediated Gene Silencing of Bmi-1 Expression on Chemosensitivity of CD44+ Nasopharyngeal Carcinoma Cancer Stem-Like Cells

In this study, we investigate the effect of short hairpin RNA-mediated gene silencing of Bmi-1 expression on chemosensitivity of CD44(+) nasopharyngeal carcinoma cancer stem-like cells. The sequence-specific short hairpin RNA lentivirus targeting at human Bmi-1 was synthesized and used to infect CD44(+) nasopharyngeal cells that were sorted by flow cytometry. We also employed flow cytometry to detect transfection efficiency. Real-time polymerase chain reaction was used to detect Bmi-1 and its downstream repressor genes p16(INK4a) and p14(ARF) messenger RNA, while each protein expression level of Bmi-1, p16(INK4a), p14(ARF), and p53 was confirmed by Western blotting protocol. Tumor spheroid assay was used to evaluate the self-renewal capacity. 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay and colony formation assay were applied to detect proliferation capacity and colony-forming capacity under different concentrations of chemotherapeutic drugs 5-fluorouracil or cisplatin. Transwell cell migration and invasion assay were employed to observe migration and invasion capacity after cells were exposed to cisplatin for 24 hours. The constructed short hairpin RNA lentivirus targeting Bmi-1 gene successfully infected into the CD44(+) nasopharyngeal carcinoma cells and effectively inhibited the Bmi-1 messenger RNA and protein expression level, while the expression level of Bim-1 target genes, p16(INK4a), p14(ARF), and p53 was significantly increased (P < .05). Notably, the proliferation, colony formation, migration, and invasion capabilities of the sequence-specific short hairpin RNA lentivirus-infected CD44(+) nasopharyngeal carcinoma cells reduced significantly under chemotherapeutic treatments (P < .05). Our results indicated that Bmi-1 may play an important role in the chemosensitivity of CD44(+) nasopharyngeal carcinoma cancer stem-like cells. Bmi-1 may be a potential new target for the treatment of nasopharyngeal carcinoma displaying chemotherapy resistance.

Polycomb Group (PcG) Proteins and Human Cancers: Multifaceted Functions and Therapeutic Implications

Polycomb group (PcG) proteins are transcriptional repressors that regulate several crucial developmental and physiological processes in the cell. More recently, they have been found to play important roles in human carcinogenesis and cancer development and progression. The deregulation and dysfunction of PcG proteins often lead to blocking or inappropriate activation of developmental pathways, enhancing cellular proliferation, inhibiting apoptosis, and increasing the cancer stem cell population. Genetic and molecular investigations of PcG proteins have long been focused on their PcG functions. However, PcG proteins have recently been shown to exert non-classical-Pc-functions, contributing to the regulation of diverse cellular functions. We and others have demonstrated that PcG proteins regulate the expression and function of several oncogenes and tumor suppressor genes in a PcG-independent manner, and PcG proteins are associated with the survival of patients with cancer. In this review, we summarize the recent advances in the research on PcG proteins, including both the Pc-repressive and non-classical-Pc-functions. We specifically focus on the mechanisms by which PcG proteins play roles in cancer initiation, development, and progression. Finally, we discuss the potential value of PcG proteins as molecular biomarkers for the diagnosis and prognosis of cancer, and as molecular targets for cancer therapy.

High peritumoral Bmi-1 expression is an independent prognosticator of poor prognosis in renal cell carcinoma

B lymphoma Mo-MLV insertion region 1 homolog (Bmi-1) is a transcriptional repressor, which plays important roles in the development of cancers, but the function of Bmi-1 in kidney tumorigenesis and its prognostic values remain unclear. This study aims to investigate prognostic values of the intratumoral and peritumoral expression of Bmi-1 in patients with renal cell carcinoma. Expression of Bmi-1 was assessed by immunohistochemistry in specimens containing paired tumor and peritumoral renal tissue from 241 patients who had undergone curative nephrectomy at Zhongshan Hospital from 2005 to 2007. The association of Bmi-1 expression with clinical and pathological parameters and outcomes was investigated. Specific expression of Bmi-1 was found both in peritumoral and intratumoral tissues. High expression of Bmi-1 in peritumoral but not intratumoral is significantly associated with poor overall survival (OS) (P < 0.001) and relapse-free survival (RFS) (P = 0.003). Furthermore, Bmi-1 expression was identified as an independent prognostic factor for OS, and combination of peritumoral Bmi-1 and tumor node metastasis (TNM) stage had a better power to predict the patients' death and disease recurrence. High peritumoral Bmi-1 expression can serve as an independent prognostic biomarker and could be a novel therapeutic target for renal cell carcinoma (RCC).

Bmi-1: At the crossroads of physiological and pathological biology

Bmi-1 is a member of the Polycomb repressor complex 1 that mediates gene silencing by regulating chromatin structure and is indispensable for self-renewal of both normal and cancer stem cells. Despite three decades of research that have elucidated the transcriptional regulation, post-translational modifications and functions of Bmi-1 in regulating the DNA damage response, cellular bioenergetics, and pathologies, the entire potential of a protein with such varied functions remains to be realized. This review attempts to synthesize the current knowledge on Bmi-1 with an emphasis on its role in both normal physiology and cancer. Additionally, since cancer stem cells are emerging as a new paradigm for therapy resistance, the role of Bmi-1 in this perspective is also highlighted. The wide spectrum of malignancies that implicate Bmi-1 as a signature for stemness and oncogenesis also make it a suitable candidate for therapy. Nonetheless, new approaches are vitally needed to further characterize physiological roles of Bmi-1 with the long-term goal of using Bmi-1 as a prognostic marker and a therapeutic target.

EZH2 is associated with malignant behavior in pancreatic IPMN via p27Kip1 downregulation

BACKGROUND

The epigenetic mechanism of tumorigenesis in pancreatic intraductal papillary mucinous neoplasm (IPMN) remains largely unknown. The aim of this study is to examine the role of enhancer of zeste homologue 2 (EZH2) alteration in pancreatic IPMN progression.

METHODS

Fifty-four surgically resected pancreatic IPMN specimens, including a total of 181 lesions (normal duct in 48, adenoma in 50, borderline atypia in 53, carcinoma in situ (CIS) in 19, and invasive carcinoma in 11) were analyzed by immunohistochemical staining (EZH2, Ki-67, p27Kip1). Using paraffin embedded sections, total RNA was successfully extracted from 20 IPMN lesions (borderline IPMN in 9, CIS in 6, invasive carcinoma in 5) and 7 pancreatic normal ducts, and then levels of EZH2 and p27Kip1 mRNA were analyzed by real time PCR.

RESULTS

In immunohistochemical analysis, cell proliferative activity revealed by Ki-67 positive nuclei was increased during IPMN progression (normal duct<adenoma<borderline atypia<CIS ≈ invasive carcinoma). EZH2 expression displayed a similar pattern (normal duct<adenoma<borderline atypia<CIS ≈ invasive carcinoma) with cell proliferative activity. EZH2 expression in malignant (CIS and invasive carcinoma) IPMNs was significantly higher than that in adenoma and borderline-atypia IPMNs. EZH2 expression level in IPMN lesions was positively correlated with the Ki-67 positive nuclear ratio (p<0.0001). EZH2-positive cells in malignant IPMN did not express p27Kip1. EZH2 mRNA expressions in malignant lesions were significantly higher than those in benign lesions (p<0.0001). In contrast, p27Kip1 mRNA in malignant lesions was significantly decreased compared to those in benign lesion (p<0.05), and there was an inverse correlation between EZH2 and p27Kip1 mRNA levels (p = 0.0109).

CONCLUSION

EZH2 is associated with the accelerated cell proliferation and malignant step in pancreatic IPMN via the downregulation of p27Kip1.

ShRNA-mediated Bmi-1 silencing sensitizes multiple myeloma cells to bortezomib

The introduction of bortezomib has resulted in a paradigm shift in the treatment of multiple myeloma (MM) and has contributed to the improved survival of patients with MM. Inevitably, resistance to therapy develops, and thus the clinical efficacy of bortezomib is hampered by drug resistance. The oncogene B-cell‑specific Moloney murine leukemia virus insertion site‑1 (Bmi-1) has been implicated in the pathogenesis of various human malignancies. Furthermore, RNA interference (RNAi)‑mediated Bmi-1 silencing has been shown to sensitize tumor cells to chemotherapy and radiation. The role of Bmi-1 in influencing the response to bortezomib therapy has not been investigated to date. In the present study, Bmi-1 was silenced in two MM cell lines (U266 and RPMI8226) using short hairpin RNA (shRNA) targeting Bmi-1 (shBmi-1). A cell counting kit-8 (CCK-8) assay was performed to analyze cell proliferation and evaluate the 50% inhibitory concentration (IC50) values of bortezomib. Cell cycle progression and apoptosis were analyzed by flow cytometry (FCM), and the mRNA and protein expression of associated genes (Bmi-1, p14, p21, Bcl-2 and Bax) was quantified by RT-qPCR and western blot analysis, respectively. The IC50 values significantly decreased in the cells transfected with shBmi-1 (p<0.05). The depletion of Bmi-1 sensitized the MM cells to bortezomib, which increased the G1 phase duration and enhanced bortezomib‑induced apoptosis (p<0.05). The expression of p21 and Bax (apoptosis inducer) was upregulated, whereas that of the anti-apoptotic protein, Bcl-2, was downregulated in the Bmi-1‑silenced cells (p<0.05). The depletion of Bmi-1 enhanced the sensitivity of MM cells to bortezomib by inhibiting cell proliferation and inducing cell cycle arrest and apoptosis. Our data suggest that Bmi-1 may serve as an important novel therapeutic target in MM.

Expression of Bmi-1 and PAI-1 in esophageal squamous cell carcinoma

AIM: To determine the correlation between invasiveness, migration and prognosis in esophageal squamous cell carcinoma (ESCC) and expression of the B-cell-specific Moloney leukemia virus insert site 1 (Bmi-1) and plasminogen activator inhibitor-1 (PAI-1).

METHODS: Eighty previously untreated patients who underwent surgical excision of ESCC were included. The expression of Bmi-1 and PAI-1 was examined immunohistochemically in formalin-fixed paraffin-embedded primary tissue specimens. The relationships between the expression of Bmi-1 and PAI-1, the clinicopathologic features of ESCC, and the survival rate of ESCC patients were also discussed. The correlation between Bmi-1 and PAI-1 protein expression in ESCC was analyzed. The relationship between Bmi-1 and PAI-1 expression and ESCC prognosis was evaluated using a Cox regression model and Kaplan-Meier survival curve analysis.

RESULTS: The rates of positive Bmi-1 and PAI-1 expression in ESCC were higher than those in normal esophageal tissue (P < 0.05). The expression of Bmi-1 and PAI-1 was correlated with depth of invasion and lymph node metastasis (P < 0.05), but not with patient age, tumor size or nationality (P > 0.05). The expression of Bmi-1 was positively correlated with that of PAI-1 (P < 0.05). The 10-year overall survival rate for all patients was 20% (16/80). Univariate Kaplan-Meier survival analysis showed that patients with high expression of esophageal PAI-1 and Bmi-1 had lower survival, however, the difference was not statistically significant. Cox multivariate analysis showed that PAI-1 and Bmi-1 were not independent factors for survival rate, while the depth of tumor invasion and metastasis were independent factors affecting patient survival.

CONCLUSION: The expression of Bmi-1 and PAI-1 plays a role in ESCC progression, and may be used as a prognostic marker in ESCC.

Autophagy-targeted vaccine of LC3-LpqH DNA and its protective immunity in a murine model of tuberculosis

The development of more effective antituberculosis vaccines would contribute to the control of the global problem of infection with Mycobacterium tuberculosis (MTB). Recently, the highlighted importance of autophagy in the host immune response against MTB has attracted the attention of researchers. However, the vaccines targeted at autophagy remain to be developed. In this study, we report on an autophagy-targeted vaccine of 19kDa MTB lipoprotein (LpqH) DNA that harbors another gene coding microtubule-associated protein light chain-3(LC3), which transports LpqH to autophagosomes and displays enhanced protective efficacy against MTB. After the transfection of pCMV-LpqH DNA, a significant increase LC3 II was detected in RAW264.7 cells, which was similar to that observed with treatment with rapamycin, a reagent used to induce autophagy. To target autophagy, the gene coding LC3, as a marked protein of autophagosome, was linked to the lpqH gene to express an LC3-LpqH fused protein. Interestingly, LC3-LpqH fused protein was determined to be transported to an autophagosome, which was demonstrated by the co-localization of GFP-LC3 with LC3-LpqH at autophagosomes. Notably, the mice immunized with LC3-LpqH/Ag85B displayed decreased mycobacterial loads in the lungs and spleen when challenged with virulent MTB by intravenous infection, which was consistent with increased IgG2a in serum and IFN-γ and IL-2 produced by splenocyte. In conclusion, our study demonstrates that an LC3-LpqH DNA vaccine could have autophagy as its target, which contributes to the enhancement of the Th1 immune response and vaccine protective efficacy.

Bmi-1-shRNA inhibits the proliferation of lung adenocarcinoma cells by blocking the G1/S phase through decreasing cyclin D1 and increasing p21/p27 levels

B lymphoma Mo-MLV insertion region 1 (Bmi-1) is highly expressed in a variety of cancers and has been shown to regulate cell proliferation. The INK4a/ARF tumor suppressor gene locus is one of the major targets of Bmi-1. In the present study, we chose two lung adenocarcinoma cell lines, A549 cells (without INK4a locus) and SPC-A1 cells (with INK4a locus), to investigate if the small hairpin RNA-mediated knockdown of Bmi-1 could inhibit the proliferation of lung adenocarcinoma cells, and to delineate the possible mechanism underlying Bmi-1 modulation of cell proliferation. We also investigated the potential pathway underlying Bmi-1 regulation of lung adenocarcinoma cell proliferation in different genetic backgrounds. To this end, we used shRNA to knockdown Bmi-1 expression in lung adenocarcinoma cells, which led to inhibition of cell growth, colony formation in vitro, and tumorigenesis in vivo. In addition, phosphorylated Akt and cyclin D1 expression were downregulated, p21 and p27 levels were upregulated, and p16 expression remained unchanged in SPC-A1 cells. These data indicate that Bmi-1 might modulate the growth of lung adenocarcinoma cells in an INK4a-p16 independent pathway.

MicroRNA-218 inhibits cell cycle progression and promotes apoptosis in colon cancer by downregulating BMI1 polycomb ring finger oncogene

Deregulated miRNAs participate in colorectal carcinogenesis. In this study, miR-218 was found to be downregulated in human colorectal cancer (CRC) by miRNA profile assay. miR-218 was silenced or downregulated in all five colon cancer cells (Caco2, HT29, SW620, HCT116 and LoVo) relative to normal colon tissues. miR-218 expression was significantly lower in 46 CRC tumor tissues compared with their adjacent normal tissues (P < 0.001). Potential target genes of miR-218 were predicted and BMI1 polycomb ring finger oncogene (BMI-1), a polycomb ring finger oncogene, was identified as one of the potential targets. Upregulation of BMI-1 was detected in CRC tumors compared with adjacent normal tissues (P < 0.001) and in all five colon cancer cell lines. Transfection of miR-218 in colon cancer cell lines (HCT116, HT29) significantly reduced luciferase activity of the wild-type construct of BMI-1 3' untranslated region (3'UTR) (P < 0.001), whereas this effect was not seen in the construct with mutant BMI-1 3'UTR, indicating a direct and specific interaction of miR-218 with BMI-1. Ectopic expression of miR-218 in HCT116 and HT29 cells suppressed BMI-1 mRNA and protein expression. In addition, miR-218 suppressed protein expression of BMI-1 downstream targets of cyclin-dependent kinase 4, a cell cycle regulator, while upregulating protein expression of p53. We further revealed that miR-218 induced apoptosis (P < 0.01), inhibited cell proliferation (P < 0.05) and promoted cell cycle arrest in the G2 phase (P < 0.01). In conclusion, miR-218 plays a pivotal role in CRC development through inhibiting cell proliferation and cycle progression and promoting apoptosis by downregulating BMI-1.

Selective radiosensitization of human cervical cancer cells and normal cells by artemisinin through the abrogation of radiation-induced G2 block

OBJECTIVE

Artemisinin has been shown to inhibit the growth of some human cancer cells. In this study, we investigated the radiosensitizing effects of artemisinin on cervical cancer cells and normal human fibroblast cells and also assessed some possible mechanisms for these effects.

MATERIALS AND METHODS

Two cervical cancer cell lines, HeLa and SiHa cells, and GM0639 normal human fibroblast cell line were treated with various concentrations of artemisinin plus radiation; the cell viability was tested using both 3-(4,5-dimethylthiazolyl-2-y1)-2, 5-diphenyltetrazolium bromide and clonogenic assays. Radiation dose-modifying factors were measured by clonogenic survival assay. Annexin V/propidium iodide assay for the evaluation of apoptosis and cell cycle phase were determined by flow cytometry, and the expression of the cell cycle-associated proteins Wee 1 and cyclin B1 were analyzed by Western blot analysis.

RESULTS

Artemisinin showed higher cytotoxicity in cervical cancer cell lines, especially in SiHa cells, than in the normal cell line. In both clonogenic assay and apoptosis, artemisinin sensitized the HeLa cancer cells to the cytotoxicity of radiation, yielding a dose-modifying factor of 1.24, but not SiHa cancer cells and GM normal cells. At a dose of 110 nmol/L, artemisinin did not change the distribution of cell cycle in 3 tested cell lines, but artemisinin abrogated the radiation-induced G2 blockade. Analyses of G2-checkpoint-related proteins, the activation of Wee 1 and depression of cyclin B1 expression induced by radiation, could be restored to the control level by artemisinin.

CONCLUSIONS

Given the unique cytotoxic profile of artemisinin on cancer cells and normal cells, artemisinin may be a potentially promising radiosensitizer through the regulation of the expression of G2 checkpoint-related proteins like Wee 1 and cyclin B1, and improve therapeutic ratios for the combination of artemisinin and ionizing irradiation in the treatment of patients with cervical cancer.

The differential expression pattern of the BMI-1, SALL4 and ABCA3 genes in myeloid leukemia

Background and methods

In order to characterize the expression pattern of SALL4, BMI-1 and ABCA3 genes in patients with myeloid leukemia and those who achieved complete remission (CR) after chemotherapy. Real-time PCR was used to determine the expression level of these genes in peripheral blood mononuclear cells from 24 patients with AML, eight patients with AML-CR, 13 patients with CML in the chronic phase (CML-CP), 12 patients with CML in blast crisis (CML-BC), 13 patients with CML-CR and 11 healthy individuals (HI).

Results

Overexpression of the BMI-1 gene was found in the AML, CML-CP and CML-BC groups as compared with HI group, while the BMI-1 expression level was lower in patients who achieved CR. In contrast, significantly increased SALL4 expression was only found in AML group, additionally, SALL4 expression was lower in the CML-CP and CML-CR groups compared with the HI group, while the SALL4 expression level in the CML-BC group was higher and significantly greater than that in the CML-CP and CML-CR groups. Moreover, a positive correlation between the expression of SALL4 and BMI-1 genes was found in samples from most groups. There was no significant difference of ABCA3 expression level in AML and CML-BC group in comparison with HI group. Interestingly, the ABCA3 expression level was significantly decreased in the CML-CP, AML-CR and CML-CR in comparison with the HI group. Moreover, the ABCA3 expression level in all of the CR groups was lower than that in their corresponding groups.

Conclusions

These results describe the altered SALL4, ABCA3 and BMI-1 expression pattern in different phases of myeloid leukemia, which may relate to the development and progression to different diseases. SALL4 expression was strongly correlated with BMI-1 in most of the myeloid leukemia patient groups, providing a potential link between SALL4 and BMI-1 in leukemogenesis.

A method for the establishment of a cell line with stable expression of the GFP-LC3 reporter protein

As the function of autophagy becomes evident in a number of diseases, including cancer and infection, it is crucial to construct macrophage cell lines with stable expression of the microtubule-associated protein light chain 3 (GFP-LC3). In this study, a mouse LC3 open-reading frame was amplified by RT-PCR, and cloned into the pEGFP-C1 plasmid for expression of the GFP-LC3 fusion protein. The recombinant plasmid was transfected into RAW264.7 cells using Lipofectamine 2000 reagent and stably transfected clones were selected by G418 screening. Autophagic puncta formation was observed by fluorescense microscopy. Additionally, we found that starvation treatment induced a significant increase in the number of autophagosomes, while wortmannin treatment significantly repressed the formation of autophagosomes. This study indicated that the RAW264.7 cell line stably expressing GFP-LC3 is available for use in a GFP-LC3 puncta formation assay, and may contribute to basic investigations of autophagic function or drug screening targeted at autophagy.

Depletion of Bmi-1 enhances 5-fluorouracil-induced apoptosis and autophagy in hepatocellular carcinoma cells

5-fluorouracil (5-FU) is one of the standard chemoradiotherapy regimens for hepatocellular carcinoma (HCC) treatment. B-cell-specific Moloney murine leukemia virus insertion site 1 (Bmi-1) has been demonstrated to regulate proliferation. Additionally, Bmi-1 overexpression has been identified in HCC cell lines and correlates with the advanced invasive stage of tumor progression and poor prognosis. In this study, we examined the effects of 5-FU treatment on cell growth in HCC cells with or without Bmi-1 depletion. The IC(50) values of 5-FU were significantly decreased to a greater extent in cells with Bmi-1 knockdown. Depletion of Bmi-1 increased sensitivity of the cells to 5-FU and increased apoptosis. Knockdown of endogenous Bmi-1 led to a substantial reduction in the levels of phospho-AKT and Bcl-2 with a concomitant increase in the levels of Bax. Additionally, 5-FU induced the conversion/turnover of microtubule-associated protein 1 light chain 3 (LC3). Knockdown of endogenous Bmi-1 led to an increase in the levels of Beclin-1 and the accumulation of LC3-II. Together, these findings reveal that Bmi-1 depletion enhanced the chemosensitivity of HCC cells by inducing apoptosis and autophagy, which is associated with the PI3K/AKT and Bcl-2/Beclin-1 pathways.

BMI1 as a novel target for drug discovery in cancer

Growing evidence has demonstrated that clonogenic cancer stem (initiating) cells are responsible for tumor regrowth and disease relapse. Bmi-1 plays a critical role in the self-renewal of adult stem cells. The Bmi-1 protein is elevated in many types of cancers, and experimental reduction of Bmi-1 protein levels by small interfering RNA (siRNA) causes apoptosis and/or senescence in tumor cells in vitro and increases susceptibility to cytotoxic agents. The Bmi-1 protein has no known enzymatic activity, but serves as the key regulatory component of the PRC1 complex (polycomb repressive complex-1). This complex influences chromatin structure and regulates transcriptional activity of a number of important loci including the Ink4a locus which encodes the tumor suppressor proteins p16(Ink4a) and p14(Arf) . In this prospective study, we will discuss the implication of BMI1 in cancers, the biology of BMI1, and the regulatory control of BMI1 expression. The target validation and the future prospects of targeting BMI1 in cancer therapy are also discussed.

Antitumor activity of artemisinin and its derivatives: from a well-known antimalarial agent to a potential anticancer drug

Improvement of quality of life and survival of cancer patients will be greatly enhanced by the development of highly effective drugs to selectively kill malignant cells. Artemisinin and its analogs are naturally occurring antimalarials which have shown potent anticancer activity. In primary cancer cultures and cell lines, their antitumor actions were by inhibiting cancer proliferation, metastasis, and angiogenesis. In xenograft models, exposure to artemisinins substantially reduces tumor volume and progression. However, the rationale for the use of artemisinins in anticancer therapy must be addressed by a greater understanding of the underlying mechanisms involved in their cytotoxic effects. The primary targets for artemisinin and the chemical base for its preferential effects on heterologous tumor cells need yet to be elucidated. The aim of this paper is to provide an overview of the recent advances and new development of this class of drugs as potential anticancer agents.