Circulating Bmi-1 mRNA as a possible prognostic factor for advanced breast cancer patients

Discovery and Characterization of a Novel Cereblon-Recruiting PRC1 Bridged PROTAC Degrader

Bridged PROTAC is a novel protein complex degrader strategy that exploits the target protein's binding partner to degrade undruggable proteins by inducing proximity to an E3 ubiquitin ligase. In this study, we discovered for the first time that cereblon (CRBN) can be employed for the bridged PROTAC approach and report the first-in-class CRBN-recruiting and EED-binding polycomb repressive complex 1 (PRC1) degrader, compound 1 (MS181). We show that 1 induces preferential degradation of PRC1 components, BMI1 and RING1B, in an EED-, CRBN-, and ubiquitin-proteosome system (UPS)-dependent manner. Compound 1 also has superior antiproliferative activity in multiple metastatic cancer cell lines over EED-binding PRC2 degraders and can be efficacious in VHL-defective cancer cells. Altogether, compound 1 is a valuable chemical biology tool to study the role of PRC1 in cancer. Importantly, we show that CRBN can be utilized to develop bridged PROTACs, expanding the bridged PROTAC technology for degrading undruggable proteins.

Exploring the Role of Circulating Cell-Free RNA in the Development of Colorectal Cancer

Circulating tumor RNA (ctRNA) has recently emerged as a novel and attractive liquid biomarker. CtRNA is capable of providing important information about the expression of a variety of target genes noninvasively, without the need for biopsies, through the use of circulating RNA sequencing. The overexpression of cancer-specific transcripts increases the tumor-derived RNA signal, which overcomes limitations due to low quantities of circulating tumor DNA (ctDNA). The purpose of this work is to present an up-to-date review of current knowledge regarding ctRNAs and their status as biomarkers to address the diagnosis, prognosis, prediction, and drug resistance of colorectal cancer. The final section of the article discusses the practical aspects involved in analyzing plasma ctRNA, including storage and isolation, detection technologies, and their limitations in clinical applications.

Targeted Degradation of PRC1 Components, BMI1 and RING1B, via a Novel Protein Complex Degrader Strategy

Polycomb repressive complex 1 (PRC1) is an essential epigenetic regulator that mainly controls histone H2A Lys119 mono-ubiquitination (H2AK119ub). B cell-specific Moloney murine leukemia virus Integration site 1 (BMI1) and really interesting new gene 1B (RING1B) are PRC1 core components and play critical roles in the development of various cancers. However, therapeutic agents targeting PRC1 are very limited. In this study, MS147, the first degrader of PRC1 core components, BMI1 and RING1B, is discovered via a novel protein complex degradation strategy that utilizes the target protein's interacting partner protein (embryonic ectoderm development (EED)). MS147, which comprises an EED small-molecule binder linked to a ligand of the E3 ligase von Hippel-Lindau (VHL), degrades BMI1/RING1B in an EED-, VHL-, ubiquitination-, and time-dependent manner. MS147 preferentially degrades BMI1/RING1B over polycomb repressive complex 2 (PRC2) core components. Consequently, MS147 effectively reduces H2AK119ub, but not histone H3 Lys27 tri-methylation (H3K27me3), which is catalyzed by PRC2. Furthermore, MS147 effectively inhibits the proliferation of cancer cell lines that are insensitive to PRC2 inhibitors/degraders. Overall, this study provides a novel BMI1/RING1B degrader, which is a useful chemical tool to further investigate the roles of PRC1 in cancer, and a novel protein complex degradation strategy, which can potentially expand the degradable human proteome.

Radiation Response of Human Leukemia/Lymphoma Cells was Improved by 7-Geranyloxycoumarin

Objectives

Adult T-cell leukemia/lymphoma (ATLL) is a blood neoplasm with specific geographic distribution. Although radiotherapy is a palliative treatment that provides long-term local control, single use of radiation leads to complications for patients. To introduce a novel multimodal approach against ATLL, we investigated combinatorial effects of 7-geranyloxycoumarin and radiation in vitro.

Methods

Viability of MT-2 cells was determined by resazurin assay upon administration of 7-geranyloxycoumarin alone and followed by radiation. Then, apoptosis was detected by annexin V and propidium iodide, and the expression of candidate genes was analyzed by qPCR.

Results

Findings revealed significant (P<.0001) improvement in radiation effects upon 7-geranyloxycoumarin pretreatment, most notably when cells were pretreated with 5 µg/ml 7-geranyloxycoumarin for 96 h, exposed to 6 Gy radiation and recovered for 48 h. These results were confirmed by flow cytometry, as the percentage of early and late apoptotic cells was increased after combinatorial treatment. In addition, significant (P< .0001) changes in CD44, c-MYC, cFLIPL, BMI-1, NF-κB (Rel A), and P53 expression was induced by 7-geranyloxycoumarin and radiation.

Conclusions

Current research indicated, for the first time, that combinatorial use of 7-geranyloxycoumarin and ionizing radiation could be considered as an effective therapeutic modality for ATLL.

BMI-1 Expression Heterogeneity in Endometriosis-Related and Non-Endometriotic Ovarian Carcinoma

BMI-1 is a key component of stem cells, which are essential for normal organ development and cell phenotype maintenance. BMI-1 expression is deregulated in cancer, resulting in the alteration of chromatin and gene transcription repression. The cellular signaling pathway that governs BMI-1 action in the ovarian carcinogenesis sequences is incompletely deciphered. In this study, we set out to analyze the immunohistochemical (IHC) BMI-1 expression in two different groups: endometriosis-related ovarian carcinoma (EOC) and non-endometriotic ovarian carcinoma (NEOC), aiming to identify the differences in its tissue profile. Methods: BMI-1 IHC expression has been individually quantified in epithelial and in stromal components by using adapted scores systems. Statistical analysis was performed to analyze the relationship between BMI-1 epithelial and stromal profile in each group and between groups and its correlation with classical clinicopathological characteristics. Results: BMI-1 expression in epithelial tumor cells was mostly low or negative in the EOC group, and predominantly positive in the NEOC group. Moreover, the stromal BMI-1 expression was variable in the EOC group, whereas in the NEOC group, stromal BMI-1 expression was mainly strong. We noted statistically significant differences between the epithelial and stromal BMI-1 profiles in each group and between the two ovarian carcinoma (OC) groups. Conclusions: Our study provides solid evidence for a different BMI-1 expression in EOC and NEOC, corresponding to the differences in their etiopathogeny. The reported differences in the BMI-1 expression of EOC and NEOC need to be further validated in a larger and homogenous cohort of study.

Circulating RNA biomarkers in diffuse large B-cell lymphoma: a systematic review

Diffuse large B-cell lymphoma (DLBCL) is the most common histological subtype of non-Hodgkin's lymphomas (NHL). DLBCL is an aggressive malignancy that displays a great heterogeneity in terms of morphology, genetics and biological behavior. While a sustained complete remission is obtained in the majority of patients with standard immunochemotherapy, patients with refractory of relapsed disease after first-line treatment have a poor prognosis. This patient group represents an important unmet need in lymphoma treatment. In recent years, improved understanding of the underlying molecular pathogenesis had led to new classification and prognostication tools, including the development of cell-free biomarkers in liquid biopsies. Although the majority of studies have focused on the use of cell-free fragments of DNA (cfDNA), there has been an increased interest in circulating-free coding and non-coding RNA, including messenger RNA (mRNA), microRNA (miRNA), long non-coding RNA (lncRNA) and circular RNA (circRNA), as well as RNA encapsulated in extracellular vesicles or tumor-educated platelets (TEPs). We performed a systematic search in PubMed to identify articles that evaluated circulating RNA as diagnostic, subtype, treatment response or prognostic biomarkers in a human DLBCL population. A total of 35 articles met the inclusion criteria. The aim of this systematic review is to present the current understanding of circulating RNA molecules as biomarker in DLBCL and to discuss their future potential.

Nuclear Factor Erythroid-Derived 2-Like 2-Induced Reductive Stress Favors Self-Renewal of Breast Cancer Stem-Like Cells via the FoxO3a-Bmi-1 Axis

Aims: A subpopulation of cancer cells, termed cancer stem cells (CSCs), has stemness properties, such as self-renewal and differentiation, which drive cancer recurrence and tumor resistance. CSCs possess enhanced protection capabilities to maintain reduced intracellular levels of reactive oxygen species (ROS) compared with nonstem-like cancer cells. This study investigated whether reductive stress could regulate self-renewal activity in breast CSCs. Results: We found that manifestation of stemness in breast cancer stem-like cells was associated with an elevated production of reduced glutathione (GSH) maintained by upregulation of glutamate cysteine ligase catalytic subunit (GCLC) and consequently, lowered ROS levels. This was accompanied by upregulation of phospho-AMP-activated protein kinase, FoxO3a, and Bmi-1. Notably, expression of nuclear factor erythroid-derived 2-like 2 (Nrf2) protein was substantially increased in cells undergoing sphere formation. We noticed that expression of Bmi-1 was inhibited after introduction of Nrf2 short interfering RNA into MCF-7 mammosphere cells. Silencing of Nrf2 expression suppressed the xenograft growth of subcutaneously or orthotopically injected human breast cancer cells. Innovation: Association between Nrf2 and self-renewal signaling in CSCs has been reported, but the underlying molecular mechanism remains largely unresolved. This study demonstrates the Nrf2-mediated signaling pathway in maintenance of reductive stress in breast CSCs. Conclusion: Nrf2 overactivation in breast CSCs upregulates GCLC expression and consequently enhances GSH biosynthesis with concurrent reduction in intracellular ROS accumulation, thereby provoking the reductive stress. The consequent upregulation of nuclear FoxO3a and its binding to the promoter of the gene encoding Bmi-1 account for the self-renewal activity of breast cancer stem-like cells and their growth in a xenograft mouse model.

Circulating RNA in blood plasma as diagnostic tool for clinical oncology

One of the key challenges facing today’s oncology is the discovery of early predictors of malignant neoplasms in patients’ biological samples. Liquid biopsy is a noninvasive diagnostic technique based on the detection and isolation of tumor cells, tumor-derived nucleic acid and exosomes circulating in the blood plasma of cancer patients. There is a plethora of research studies of circulating tumor DNA in patients with MN. The active proliferation of tumor cells occurs in the backdrop of altered gene expression. The presence of tissue-specific transcripts in the circulating RNA fraction suggests that levels of circulating RNA reflect the development of the primary tumor. We think that cell-free RNA circulating in the blood plasma is a promising molecular biomarker for early cancer detection.

BMI‑1 promotes invasion and metastasis in endometrial adenocarcinoma and is a poor prognostic factor

Endometrial adenocarcinoma is one of the most common types of gynecological malignancies and its incidence and mortality rates are increasing. Due to tumor recurrence and metastasis, the overall five-year survival rate of patients with endometrial adenocarcinoma is shortened. The aim of the present was to investigate the role of the polycomb group protein B-lymphoma Mo-MLV insertion region 1 (BMI-1) in the invasion, metastasis and the epithelial-mesenchymal transition (EMT) of endometrial adenocarcinoma cells, as well its effects on the prognosis of patients with endometrial adenocarcinoma. Immunohistochemistry was used to examine the expression profile of BMI-1 in normal and endometrial adenocarcinoma tissues. Western blotting was used to examine the expression levels of BMI-1 and EMT markers. Kaplan-Meier plots and a Cox proportional hazards model were used to assess the overall survival. MTT cell viability assays were used to detect the proliferation of endometrial cancer cells. Transwell assays were used to examine cell migration and invasion. Small interfering RNA was used to downregulate BMI-1 expression levels, to study its effect on EMT. Immunohistochemical and clinicopathological analyses showed that BMI-1 expression was increased in endometrial adenocarcinoma tissue compared with the normal endometrial tissue (P<0.05). The increased expression levels of BMI-1 were closely associated with stage, myometrial invasion and lymph node metastasis (P<0.05). Kaplan-Meier plots and a Cox proportional hazards model showed that increased BMI-1 expression was associated with a less favorable prognosis [P=0.040, hazards ratio (HR)=1.596] and was associated with late-stage adenocarcinoma (P=0.006, HR=1.670). Myometrial invasion (P=0.006, HR=1.509) and lymph node metastasis (P=0.004, HR=1.703) were determined to predict a less favorable prognosis. Downregulation of BMI-1 reduced migration and invasion in endometrial cancer cells in vivo. It was also found that downregulation of BMI-1 increased the expression levels of the epithelial markers E-cadherin and keratin, and decreased the expression levels of the mesenchymal markers N-cadherin, vimentin and the downstream transcription factor, Slug. In conclusion, BMI-1 expression was correlated with tumor invasion and metastasis, contributing to deep myometrial invasion and lymph node metastasis, and was a poor prognostic factor for endometrial adenocarcinoma.

Evaluation of the expression of Bmi-1 stem cell marker in sinonasal melanomas and its correlation with the expression of cell cycle proteins

Background

Sinonasal melanomas (SNM) are aggressive neoplasms, which present distinct clinicopathological and molecular aspects when compared to cutaneous melanomas (CM). B-cell-specific moloney murine leukemia virus integration site-1 (Bmi-1) is a stem cell marker involved in the regulation of the cell cycle and has been found to be expressed in 70% of CM and 100% of benign nevi. Regarding the cell cycle, Bmi-1 is known to be an upstream repressor of p16, which is a tumor suppressor encoded by the INK4a/Arf locus. Considering this, the aim of this study is to evaluate the immunohistochemical expression of Bmi-1 in a series of SNM and its correlation with the expression of cell cycle proteins (p16 and Ki-67, a nuclear antigen of proliferating cells).

Methods

In 16 cases of SNM, nuclear expression of Bmi-1 and nuclear and cytoplasmic of p16 was classified as: absent, low (> 5 to < 50% of cells) and high (≥50%). Ki-67 proliferation index was represented by the ratio positive cells/ total cells.

Results

Histologically, all cases presented varying amount of necrosis and 75% contained undifferentiated cells. Bmi-1 was detected in 6 cases (37.5%) with high level of expression in 2; p16 expression was seen in 10 cases (62.5%) with high level in 7. The frequency of p16 expression did not differ significantly between tumors with or without Bmi-1 expression. Ki-67 index ranged from 8 to 22%. Neither Bmi-1 nor p16 expression showed correlation with Ki-67 index. Bmi-1 negative tumors presented more extensive necrosis (71.4%); no association between Bmi-1 expression and undifferentiated phenotype was observed.

Conclusions

In our SNM series, low immunohistochemical expression of Bmi-1 was a common phenomenon favoring the hypothesis that mucosal melanoma possibly presents molecular pathways different from the cutaneous counterpart. In SNM, Bmi-1 and p16 expression levels did not correlate with each other or with the cell proliferative index.

FUN14 domain-containing 1 promotes breast cancer proliferation and migration by activating calcium-NFATC1-BMI1 axis

BACKGROUND

FUN14 domain-containing 1 (FUNDC1), as a novel member of mitochondria-associated endoplasmic reticulum (ER) membranes associates with mitochondrial division and mitophagy. However, the expression profile and functional roles of FUNDC1 remain largely unclear in human cancer biology, including breast cancer (BC).

METHODS

Immunohistochemistry and western blot analysis were used to determine the expression of FUNDC1 and BMI1 polycomb ring finger oncogene (BMI1). CCK8, cell counting and transwell assays were used to analyze cell proliferation, migration and invasion, respectively. Luciferase reporter and chromatin immunoprecipitation (ChIP) assays were used to detect the transcriptional regulation of Nuclear factor of activated T-cells, cytoplasmic 1 (NFATC1). The prognostic merit of NFATC1 expression was assessed by Kaplan-Meier assay.

FINDINGS

Immunohistochemistry revealed strong immunostaining for FUNDC1 in cytoplasmic and nuclear membrane distribution in BC tissues as compared with normal breast epithelium. Kaplan-Meier survival analysis showed worse outcome for BC patients with high FUNDC1 expression. In vitro assay of gain- and loss-of-function of FUNDC1 suggested that FUNDC1 could stimulate BC cell proliferation, migration and invasion. Furthermore, elevated FUNDC1 level promoted Ca²⁺ cytosol influx from ER and extracellular, as well as NFATC1 nuclear translocation and activity. Nuclear NFATC1 bound to the BMI1 gene promoter and transcriptionally upregulated its expression. Notably, BMI1 overexpression could rescue the loss of function of FUNDC1. Co-expression of FUNDC1 and BMI1 in BC patients predicted worse prognosis than without either expression.

INTERPRETATION

FUNDC1 might promote BC progression by activating the Ca²⁺-NFATC1-BMI1 axis. This pathway may be promising for developing multiple targets for BC therapy.

Liquid Biopsy beyond Circulating Tumor Cells and Cell-Free DNA

Liquid biopsy represents the analysis of tumor-derived material in the blood and other body fluids of cancer patients. This portrays a minimally invasive detection tool for molecular biomarkers. Liquid biopsy has emerged as a complementary or alternative method to surgical biopsy. This non-invasive detection tool overcomes the recurrent problems in the clinical assessment of tumors that stem from the lack of accessibility to the tumor tissue and its clonal heterogeneity. Moreover, body fluid-derived components have shown to reflect the genetic profile of both primary and metastatic lesions and provide a real-time monitoring of tumor dynamics, representing a great promise for personalized medicine. This review will highlight the latest breakthroughs and the current applications of several tumor-derived biomarkers that can be found in body fluids. The authors will focus on tumor-derived exosomes, tumor-educated platelets, and circulating tumor miRNAs and mRNAs, and how these can be used for tumor detection.

The circulating transcriptome as a source of cancer liquid biopsy biomarkers

Non-invasive biomarkers or liquid biopsies have the potential to revolutionise cancer patient management as repeated sampling allows real-time monitoring of disease progression and response to treatment. This allows for earlier intervention and dynamic treatment management; both cornerstones of personalised medicine. The circulating transcriptome represents a rich source of potential cancer biomarkers that includes many classes of RNA, both coding and non-coding, that are only now beginning to be explored. In particular the increasing power and availability of RNAseq techniques have pushed studies beyond circulating miRNAs, to other classes of RNA including mRNA, snRNA, snoRNA, piRNA, YRNA, lncRNA and circRNA. In this review we focus on the emerging potential for these different classes of RNA as cancer biomarkers, and in particular the barriers and limitations that remain to be overcome if these molecules are to become part of routine clinical practice.

Association of Elevated Peripheral Blood Micronucleus Frequency and Bmi-1 mRNA Expression with Metastasis in Iranian Breast Cancer Patients

Background:

In order to find cytogenetic and molecular metastasis biomarkers detectable in peripheral blood the spontaneous genomic instability expressed as micronuclei and Bmi-1 expression in peripheral blood of breast cancer (BC) patients were studied in different stages of the disease compared with unaffected first-degree relatives (FDRs) and normal control.

Methods:

The Cytokinesis Block Micronuclei Cytome (CBMN cyt) and nested real-time Reverse Transcription-Polymerase Chain Reaction (RT-PCR) assays, were respectively used to measure genomic instability and Bmi-1 gene expression in 160 Iranian individuals comprised of BC patients in different stages of the disease, unaffected FDRs and normal control groups.

Result:

The frequency of micronuclei and Bmi-1 expression were dramatically higher in distant metastasis compared with non-metastatic BC. In spite of micronucleus frequency with no association with lymph node (LN) involvement and hormone receptor status, the Bmi-1 expression level was higher in LN positive and triple negative patients.

Conclusion:

Our results indicate that increased genomic instability expressed as micronuclei and higher Bmi-1 expression in peripheral blood are associated with metastasis in breast cancer. Therefore implementation of micronucleus assay and Bmi-1 expression analysis in blood as possible cytogenetic and molecular biomarkers in clinical level may potentially enhance the quality of management of patients with breast cancer.

Liquid Biopsy Biomarkers in Bladder Cancer: A Current Need for Patient Diagnosis and Monitoring

Bladder Cancer (BC) represents a clinical and social challenge due to its high incidence and recurrence rates, as well as the limited advances in effective disease management. Currently, a combination of cytology and cystoscopy is the routinely used methodology for diagnosis, prognosis and disease surveillance. However, both the poor sensitivity of cytology tests as well as the high invasiveness and big variation in tumour stage and grade interpretation using cystoscopy, emphasizes the urgent need for improvements in BC clinical guidance. Liquid biopsy represents a new non-invasive approach that has been extensively studied over the last decade and holds great promise. Even though its clinical use is still compromised, multiple studies have recently focused on the potential application of biomarkers in liquid biopsies for BC, including circulating tumour cells and DNA, RNAs, proteins and peptides, metabolites and extracellular vesicles. In this review, we summarize the present knowledge on the different types of biomarkers, their potential use in liquid biopsy and clinical applications in BC.

BMI1 and PTEN are key determinants of breast cancer therapy: A plausible therapeutic target in breast cancer

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

Downregulation of Bmi1 in breast cancer stem cells suppresses tumor growth and proliferation

Targeting cancer stem cells during initial treatment is important to reduce incidence of recurrent disease. Bmi1 has been associated with cancer stem cell self-renewal and aggressive disease. The purpose of this study was to determine the effects of downregulation of Bmi1 in breast cancer stem cells in order to target and eliminate the stem cell population in the tumor mass. Bmi1 was downregulated using two approaches in the mouse breast cancer stem cell line FMMC 419II—a small molecule inhibitor (PTC 209) and stable transfection with a Bmi1 shRNA plasmid. The functional effect of Bmi1 downregulation was tested in vitro and in vivo. Each approach led to decreased Bmi1 expression that correlated with an inhibition of cancer stem cell properties in vitro including cell cycle arrest and reduced mammosphere forming potential, and a decrease in tumor mass in vivo after either intra-tumoral or systemic nanoparticle-targeted delivery of anti-Bmi1. These results show that inhibiting Bmi1 expression in breast cancer stem cells could be important for the complete elimination of tumor and potentially preventing disease relapse.

High BMI1 mRNA expression in peripheral whole blood is associated with favorable prognosis in advanced non-small cell lung cancer patients

Polycomb group member protein BMI1 is involved in maintaining cell identity, proliferation, differentiation and human oncogenesis. In the present study, we determined BMI1 mRNA expression in whole blood and evaluated the impact of the expression level on the treatment response and survival of 96 advanced NSCLC patients treated with first-line platinum-based chemotherapy. We also determined BMI1 mRNA expression in primary tumors from 22 operable NSCLC patients treated with radical surgery. We found that compared with control subjects, BMI1 mRNA expression in whole blood of advanced NSCLC patients was decreased (P<0.001). Similarly, we observed decreased BMI1 mRNA expression in primary tumors compared to normal lungs from operable NSCLC patients (P=0.001). We found high BMI1 mRNA expression in blood was associated with longer progression-free survival (PFS) (P=0.049) and overall survival (OS) (P=0.012) in advanced NSCLC patients treated with first-line platinum-based chemotherapy. However, no association between the BMI1 mRNA level and response to chemotherapy was found (P=0.21). Multivariate Cox proportional hazards regression analysis showed elevated BMI1 mRNA level in whole blood was an independent prognostic factor for longer PFS (P=0.012) and OS (P<0.001). In conclusion, BMI1 mRNA expression in whole blood might represent a new biomarker for the diagnosis and prognosis of NSCLC.

Reduction of gastric cancer proliferation and invasion by miR-15a mediated suppression of Bmi-1 translation

B-cell specific moloney leukemia virus insertion site 1 (Bmi-1) gene plays important roles in gastric cancer, but the epigenetic regulatory mechanism by microRNA (miRNA) and the functional significance of Bmi-1 inhibition in gastric cancer remains elusive. In this study, we systematically investigated the functional roles of miRNA mediated Bmi-1 suppression in gastric cancer. Our results show that the expression of miR-15a is significantly reduced in gastric cancer and the protein expression levels of Bmi-1 are inversely correlated with miR-15a (P = 0.034) in gastric cancer patient samples. Functional studies revealed that ectopic expression of miR-15a decreased Bmi-1 in gastric cancer cell lines with reduced proliferation and tumor invasion. High levels of Bmi-1 in gastric cancer patients are significantly associated with better overall survival (P = 0.024) based on the Kaplan-Meier survival analysis.

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.

Polycomb group expression signatures in the malignant progression of gliomas

Polycomb group (PcG) proteins form at least two key complexes, namely polycomb repressive complex 1 and polycomb repressive complex 2. These complexes are involved in the progression of various cancers. Systematic research has not been conducted on the aberrant expression of PcG members in gliomas. Using the Chinese Glioma Genome Atlas data set, PcG expression patterns between normal brain tissues and glioma samples were analyzed, and a PcG-based classifier was then developed using BRB Cox regression and risk-score model. These results were validated in an independent GSE16011 set. A total of six PcGs [chromobox protein homolog (CBX) 6, CBX7, PHD finger protein 1, enhancer of zeste homolog 2 (EZH2), DNA (cytosine-5-)-methyltransferase 3β (DNMT3B) and polyhomeotic-like protein 2] were identified to be associated with glioma grade. Survival analysis then revealed a five-PcG gene signature one protective gene (enhancer of zeste homolog 1) and four risky genes (EZH2, PHD finger protein 19, DNMT3A and DNMT3B), which may identify patients with high risk of poor prognosis of glioma. Multivariate Cox analysis indicated that the five-PcG signature was an independent prognostic biomarker. These findings indicated that a novel prognostic classifier, five-PcG signature, served as an independent prognostic marker for patients with glioma.

Circulating biomarkers to monitor cancer progression and treatment

Tumor heterogeneity is a major challenge and the root cause of resistance to treatment. Still, the standard diagnostic approach relies on the analysis of a single tumor sample from a local or metastatic site that is obtained at a given time point. Due to intratumoral heterogeneity and selection of subpopulations in diverse lesions this will provide only a limited characterization of the makeup of the disease. On the other hand, recent developments of nucleic acid sequence analysis allows to use minimally invasive serial blood samples to assess the mutational status and altered gene expression patterns for real time monitoring in individual patients. Here, we focus on cell-free circulating tumor-specific mutant DNA and RNA (including mRNA and non-coding RNA), as well as current limitations and challenges associated with circulating nucleic acids biomarkers.

High-throughput sequencing of human plasma RNA by using thermostable group II intron reverse transcriptases

Next-generation RNA-sequencing (RNA-seq) has revolutionized transcriptome profiling, gene expression analysis, and RNA-based diagnostics. Here, we developed a new RNA-seq method that exploits thermostable group II intron reverse transcriptases (TGIRTs) and used it to profile human plasma RNAs. TGIRTs have higher thermostability, processivity, and fidelity than conventional reverse transcriptases, plus a novel template-switching activity that can efficiently attach RNA-seq adapters to target RNA sequences without RNA ligation. The new TGIRT-seq method enabled construction of RNA-seq libraries from <1 ng of plasma RNA in <5 h. TGIRT-seq of RNA in 1-mL plasma samples from a healthy individual revealed RNA fragments mapping to a diverse population of protein-coding gene and long ncRNAs, which are enriched in intron and antisense sequences, as well as nearly all known classes of small ncRNAs, some of which have never before been seen in plasma. Surprisingly, many of the small ncRNA species were present as full-length transcripts, suggesting that they are protected from plasma RNases in ribonucleoprotein (RNP) complexes and/or exosomes. This TGIRT-seq method is readily adaptable for profiling of whole-cell, exosomal, and miRNAs, and for related procedures, such as HITS-CLIP and ribosome profiling.

The circulating transcriptome as a source of non-invasive cancer biomarkers: concepts and controversies of non-coding and coding RNA in body fluids

The gold standard for cancer diagnosis remains the histological examination of affected tissue, obtained either by surgical excision, or radiologically guided biopsy. Such procedures however are expensive, not without risk to the patient, and require consistent evaluation by expert pathologists. Consequently, the search for non-invasive tools for the diagnosis and management of cancer has led to great interest in the field of circulating nucleic acids in plasma and serum. An additional benefit of blood-based testing is the ability to carry out screening and repeat sampling on patients undergoing therapy, or monitoring disease progression allowing for the development of a personalized approach to cancer patient management. Despite having been discovered over 60 years ago, the clear clinical potential of circulating nucleic acids, with the notable exception of prenatal diagnostic testing, has yet to translate into the clinic. The recent discovery of non-coding (nc) RNA (in particular micro(mi)RNAs) in the blood has provided fresh impetuous for the field. In this review, we discuss the potential of the circulating transcriptome (coding and ncRNA), as novel cancer biomarkers, the controversy surrounding their origin and biology, and most importantly the hurdles that remain to be overcome if they are really to become part of future clinical practice.

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).

Direct serum assay for cell-free bmi-1 mRNA and its potential diagnostic and prognostic value for colorectal cancer

PURPOSE

Cell-free Bmi-1 mRNA is stably detectable in the serum/plasma and is associated with the development and progression of some tumors. Previous methods detecting extracellular Bmi-1 mRNA with RNA extraction are inefficient. This study developed a novel reverse transcription quantitative PCR (RT-qPCR) approach directly applied in serum (RT-qPCR-D) to quantify Bmi-1 mRNA, and assessed its diagnostic and prognostic potential in colorectal cancer.

EXPERIMENTAL DESIGN

The feasibility of the RT-qPCR-D method was first analyzed in 50 serum samples. Then, using the RT-qPCR-D method, Bmi-1 mRNA expression was validated in serum from an independent cohort of patients with 87 normal colonoscopy, 76 hyperplastic polyp, 82 inflammatory bowel disease, 68 adenoma, and 158 colorectal cancer. Receiver operating characteristic (ROC) curves and Cox analyses were used to evaluate its diagnosis and prognosis value, respectively.

RESULTS

In a pilot study, levels of Bmi-1 mRNA were increased in colorectal cancer serum samples detected by RT-qPCR-D and significantly associated with results obtained by RT-qPCR. In a validation cohort, serum Bmi-1 mRNA levels were significantly elevated in the colorectal cancer group and the adenoma group when compared with other groups. The area under ROC curve distinguishing colorectal cancer from benign colorectal diseases was 0.888, with 72.2% sensitivity and 94.9% specificity, which was superior to carcinoembryogenic antigen. Bmi-1 mRNA levels were significantly associated with survival. Cox analysis indicated Bmi-1 mRNA was an independent prognostic factor for overall survival.

CONCLUSIONS

Detection of cell-free Bmi-1 mRNA in serum by RT-qPCR-D is a simple and noninvasive approach and may be used for colorectal cancer diagnosis and prognosis.

MiR-203 inhibits melanoma invasive and proliferative abilities by targeting the polycomb group gene BMI1

Metastasis is the major problem in malignant melanoma, posing a therapeutic challenge to clinicians. The investigation of the underlying mechanism driving this progress remains a large unmet need. In this study, we revealed a miR-203-BMI1 axis that regulated melanoma metastasis. We found significantly deregulation of miR-203 and up-regulation of BMI1 in melanoma, particularly in metastatic melanoma. An inverse correlation between the levels of miR-203 and BMI1 was further observed in melanoma tissues and cell lines. We also identified BMI1 as a downstream target gene of miR-203, which bound to the 3'UTR of BMI1. Overexpression of miR-203 was associated with decreased BMI1 expression and impaired cell invasion and tumor sphere formation activities. Re-expression of BMI1 markedly rescued miR-203-mediated suppression of these events. Taken together, our results demonstrated that miR-203 regulated melanoma invasive and proliferative abilities in part by targeting BMI1, providing new insights into potential mechanisms of melanoma metastasis.

Bmi1 regulates self-renewal and epithelial to mesenchymal transition in breast cancer cells through Nanog

Background

The Bmi1 polycomb ring finger oncogene, a transcriptional repressor belonging to the Polycomb group of proteins plays an important role in the regulation of stem cell self-renewal and is elevated in several cancers. In the current study, we have explored the role of Bmi1 in regulating the stemness and drug resistance of breast cancer cells.

Methods

Using real time PCR and immunohistochemistry primary breast tissues were analyzed. Retro- and lentiviruses were utilized to overexpress and knockdown Bmi1, RT-PCR and Western blot was performed to evaluate mRNA and protein expression. Stemness properties were analyzed by flow cytometry and sphere-formation and tumor formation was determined by mouse xenograft experiments. Dual luciferase assay was employed to assess promoter activity and MTT assay was used to analyze drug response.

Results

We found Bmi1 overexpression in 64% of grade III invasive ductal breast adenocarcinomas compared to normal breast tissues. Bmi1 overexpression in immortalized and transformed breast epithelial cells increased their sphere-forming efficiency, induced epithelial to mesenchymal transition (EMT) with an increase in the expression of stemness-related genes. Knockdown of Bmi1 in tumorigenic breast cells induced epithelial morphology, reduced expression of stemness-related genes, decreased the IC₅₀ values of doxorubicin and abrogated tumor-formation. Bmi1-high tumors showed elevated Nanog expression whereas the tumors with lower Bmi1 showed reduced Nanog levels. Overexpression of Bmi1 increased Nanog levels whereas knockdown of Bmi1 reduced its expression. Dual luciferase promoter-reporter assay revealed Bmi1 positively regulated the Nanog and NFκB promoter activity. RT-PCR analysis showed that Bmi1 overexpression activated the NFκB pathway whereas Bmi1 knockdown reduced the expression of NFκB target genes, suggesting that Bmi1 might regulate Nanog expression through the NFκB pathway.

Conclusions

Our study showed that Bmi1 is overexpressed in several high-grade, invasive ductal breast adenocarcinomas, thus supporting its role as a prognostic marker. While Bmi1 overexpression increased self-renewal and promoted EMT, its knockdown reversed EMT, reduced stemness, and rendered cells drug sensitive, thus highlighting a crucial role for Bmi1 in regulating the stemness and drug response of breast cancer cells. Bmi1 may control self-renewal through the regulation of Nanog expression via the NFκB pathway.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-785) contains supplementary material, which is available to authorized users.

Ethyl acetate extract from Jiedu Xiaozheng Yin inhibits the proliferation of human hepatocellular carcinoma cells by suppressing polycomb gene product Bmi1 and Wnt/β-catenin signaling

Jiedu Xiaozheng Yin (JXY) is a Chinese herbal decoction used to treat hepatocellular carcinoma (HCC). Previous studies have demonstrated that JXY can inhibit HCC cell proliferation via induction of G0/G1 phase arrest. In this study, we investigated whether the inhibitory effect of JXY on HCC cells is associated with the inhibition of the Wnt/β‑catenin pathway and the polycomb gene product Bmi1. Ethyl acetate extract from JXY (EE-JXY) was prepared. Methyl thiazolyl tetrazolium (MTT) and colony formation assays were used to measure cell proliferation. Immunofluorescence was used to analyze the expression and location of β-catenin and Bmi1. Immunohistochemistry was used to examine the expression of proliferating cell nuclear antigen (PCNA), c-myc and cyclin D1. β-catenin, Bmi1, c-myc, cyclin D1 and p16INK4A mRNA levels were detected by RT-PCR. The results demonstrated that EE-JXY inhibited the expression of PCNA, c-myc, cyclin D1 and Bmi1, and upregulated the expression of p16INK4A. We also found that EE-JXY could facilitate β-catenin translocation from the cytoplasm and nuclei to the cytomembrane. Finally, suppression of cell proliferation and expression of Bmi1 and Wnt/β-catenin by EE-JXY was confirmed in a mouse xenograft model of HCC. Thus, EE-JXY can inhibit the proliferation of HCC partially via suppression of the Bmi1 and Wnt/β-catenin signaling pathways.

Plasma Bmi1 mRNA as a potential prognostic biomarker for distant metastasis in colorectal cancer patients

Bmi1 is overexpressed in gastrointestinal cancers, including colorectal cancer (CRC); however, its role as a non-invasive biomarker in CRC has not been established. The aim of this study was to compare the plasma Bmi1 mRNA levels prior to and following curative resection of the primary tumor in CRC patients and to determine their association with the clinicopathological parameters. The plasma Bmi1 mRNA level was measured by quantitative polymerase chain reaction and expressed as cycle threshold value. There was no significant difference between the overall pre- and postoperative plasma Bmi1 mRNA level (31.73±2.63 vs. 31.93±2.88, respectively; P=0.614) in 45 CRC patients. However, when grouped into non-metastatic and metastatic CRC patients, the postoperative Bmi1 transcript level was found to be significantly lower compared to the preoperative level in patients with non-metastatic CRC (32.13±2.677 31.44±2.764, respectively; P=0.041), whereas there was a trend towards a higher postoperative Bmi1 transcript level compared to the preoperative level in the metastatic counterpart (30.85±3.916 vs. 33.27±0.718, respectively; P=0.164). Furthermore, when the patients were categorized into two groups according to their plasma Bmi1 postoperative vs. preoperative level status, we observed that patients without a reduction in the postoperative plasma Bmi1 mRNA levels exhibited a significantly higher rate of distant metastasis following primary resection (P=0.017) and a significantly worse prognosis regarding disease-free survival (P=0.016) when compared to the reduced postoperative plasma Bmi1 level counterparts. In conclusion, plasma Bmi1 mRNA levels may serve as a non-invasive biomarker for monitoring occult metastasis and predicting the development of distant metastasis.

Neuromedin U: a candidate biomarker and therapeutic target to predict and overcome resistance to HER-tyrosine kinase inhibitors

Intrinsic and acquired resistance to HER-targeting drugs occurs in a significant proportion of HER2-overexpressing breast cancers. Thus, there remains a need to identify predictive biomarkers that could improve patient selection and circumvent these types of drug resistance. Here, we report the identification of neuromedin U (NmU) as an extracellular biomarker in cells resistant to HER-targeted drugs. NmU overexpression occurred in cells with acquired or innate resistance to lapatinib, trastuzumab, neratinib, and afatinib, all of which displayed a similar trend upon short-term exposure, suggesting NmU induction may be an early response. An analysis of 3,489 cases of breast cancer showed NmU to be associated with poor patient outcome, particularly those with HER2-overexpressing tumors independent of established prognostic indicators. Ectopic overexpression of NmU in drug-sensitive cells conferred resistance to all HER-targeting drugs, whereas RNAi-mediated attenuation sensitized cells exhibiting acquired or innate drug resistance. Mechanistic investigations suggested that NmU acted through HSP27 as partner protein to stabilize HER2 protein levels. We also obtained evidence of functional NmU receptors on HER2-overexpressing cells, with the addition of exogenous NmU eliciting an elevation in HER2 and EGFR expression along with drug resistance. Finally, we found that NmU seemed to function in cell motility, invasion, and anoikis resistance. In vivo studies revealed that NmU attenuation impaired tumor growth and metastasis. Taken together, our results defined NmU as a candidate drug response biomarker for HER2-overexpressing cancers and as a candidate therapeutic target to limit metastatic progression and improve the efficacy of HER-targeted drugs.

Estrogen receptor α-coupled Bmi1 regulation pathway in breast cancer and its clinical implications

Background

Bmi1 has been identified as an important regulator in breast cancer, but its relationship with other signaling molecules such as ERα and HER2 is undetermined.

Methods

The expression of Bmi1 and its correlation with ERα, PR, Ki-67, HER2, p16^INK4a, cyclin D1 and pRB was evaluated by immunohistochemistry in a collection of 92 cases of breast cancer and statistically analyzed. Stimulation of Bmi1 expression by ERα or 17β-estradiol (E2) was analyzed in cell lines including MCF-7, MDA-MB-231, ERα-restored MDA-MB-231 and ERα-knockdown MCF-7 cells. Luciferase reporter and chromatin immunoprecipitation assays were also performed.

Results

Immunostaining revealed strong correlation of Bmi1 and ERα expression status in breast cancer. Expression of Bmi1 was stimulated by 17β-estradiol in ERα-positive MCF-7 cells but not in ERα-negative MDA-MB-231 cells, while the expression of Bmi1 did not alter expression of ERα. As expected, stimulation of Bmi1 expression could also be achieved in ERα-restored MDA-MB-231 cells, and at the same time depletion of ERα decreased expression of Bmi1. The proximal promoter region of Bmi1 was transcriptionally activated with co-transfection of ERα in luciferase assays, and the interaction of the Bmi1 promoter with ERα was confirmed by chromatin immunoprecipitation. Moreover, in breast cancer tissues activation of the ERα-coupled Bmi1 pathway generally correlated with high levels of cyclin D1, while loss of its activity resulted in aberrant expression of p16^INK4a and a high Ki-67 index, which implied a more aggressive phenotype of breast cancer.

Conclusions

Expression of Bmi1 is influenced by ERα, and the activity of the ERα-coupled Bmi1 signature impacts p16^INK4a and cyclin D1 status and thus correlates with the tumor molecular subtype and biologic behavior. This demonstrates the important role which is played by ERα-coupled Bmi1 in human breast cancer.

Embryonic stem cell-specific signature in cervical cancer

The wide range of invasive and noninvasive lesion phenotypes associated with high-risk human papillomavirus (HR-HPV) infection in cervical cancer (CC) indicates that not only the virus but also specific cervical epithelial cells in the transformation zone (TZ), such as stem cells (SCs), play an important part in the development of cervical neoplasia. In this review, we focused in an expression signature that is specific to embryonic SCs and to poorly differentiated cervical malignant tumors and we hypothesize that this expression signature may play an important role to promote cell growth, survival, colony formation, lack of adhesion, as well as cell invasion and migration in CC.

Epigenetics of melanoma: implications for immune-based therapies

Malignant melanoma is a complex disease that arises and evolves due to a myriad of genetic and epigenetic events. Among these, the interaction between epigenetic alterations (i.e., histone modifications, DNA methylation, mRNA silencing by miRNAs and nucleosome repositioning) has been recently identified as playing an important role in melanoma development and progression by affecting key cellular pathways such as cell cycle regulation, DNA repair, apoptosis, invasion and immune recognition. Differently to genetic lesions, epigenetic changes are potentially pharmacologically reversible by using epigenetic drugs. Along this line, preclinical and clinical findings indicate that these drugs, given alone or in combination therapies, can efficiently modulate the immunophenotype of melanoma cells. The aim of this review is to provide a comprehensive summary of melanoma epigenetics and the current use of epigenetic drugs in the clinical setting.

Regulation of BMI1 Polycomb gene expression in histological grades of invasive ductal breast carcinomas and its correlation with hormone receptor status

BMI1 is the first functional mammalian Polycomb group (PcG) proto-oncogene involved in multiple biological processes. Regulation of B cell-specific Moloney murine leukaemia virus integration site 1 (BMI1) expression with increase in histological grades of breast carcinoma in correlation with hormone receptor status was studied in 60 Indian breast cancer patient's formalin-fixed paraffin-embedded tissue blocks. Relative expression of BMI1 was studied using real-time PCR. Immunohistochemistry explained the distribution of hormone receptor markers. Correlation of BMI1 gene expression with oestrogen receptor, progesterone receptor (PR) and human epidermal growth factor receptor 2/neu status was analysed using Hex-protein docking tool. The hormone receptor expression was reduced with increasing grades of breast tumour. BMI1 gene expression was downregulated (real-time polymerase chain reaction analysis). Docking analysis explained the correlation between BMI1 and PR expression. BMI1 gene was co-regulated (down) with PR in the invasive ductal breast carcinoma with relative progression explicating it a diagnostic biomarker for ductal carcinoma of the breast.

Co-expression of Bmi1 and EZH2 as an independent poor prognostic factor in esophageal squamous cell carcinoma

Bmi1 polycomb ring finger oncogene (Bmi1) and the enhancer of zeste homolog 2 (EZH2) are members of polycomb repressive complex (PRC) 1 and PRC2, respectively. PRC1 represses tumor suppressor genes such as p16INK4a and p14ARF in a PRC2-dependent manner. There have been few studies on Bmi1 or EZH2 expression in esophageal squamous cell carcinoma (ESCC). We investigated Bmi1 and EZH2 expression in 164 cases of ESCCs using immunohistochemistry, and evaluated the correlation with clinicopathologic features and their prognostic significance. Bmi1 and EZH2 were more highly expressed in tumor than in adjacent normal tissue (p<0.001). High expression of Bmi1 or EZH2 alone was not correlated with any clinicopathologic parameter and did not influence the prognosis. However, the group with high expression of both Bmi1 and EZH2 showed the poorest prognosis in overall survival (p=0.027) and disease-free survival (p=0.007). Also, it was an independent prognostic factor in overall survival (p=0.047). High expression of both Bmi1 and EZH2, not each alone, is an independent poor prognostic factor in ESCCs, supporting the repression of tumor suppressor gene by Bmi1 in an EZH2-dependent manner. This result suggests that both Bmi1 and EZH2, not each alone, could be potent candidates of new target therapy in ESCCs.

Overexpression of BMI-1 is associated with poor prognosis in cervical cancer

AIM

It has been reported that BMI-1, a gene transcription promoter overexpressed in various human cancers, is associated with poor survival. We investigated whether BMI-1 is a marker for cervical cancer by detecting the expression of BMI-1 in cervical cancer.

METHODS

An immunohistochemistry (IHC) streptavidin-peroxidase technique was used to identify BMI-1 protein expression in 302 cervical cancer specimens. Reverse transcription polymerase chain reaction and Western blot were employed to measure BMI-1 mRNA and protein level. The correlation between BMI-1 expression and clinicopathological factors was analyzed.

RESULTS

Both BMI-1 mRNA and protein expression were evident in cervical carcinoma tissues. An intense positive rate of 55.3% (167/302) was observed by IHC. High BMI-1 expression was correlated with clinical stage, lymph node metastasis, vascular invasion and human papillomavirus (HPV) infection (P < 0.05), but there is insufficient evidence to confirm its value in tumor size, age, estrogen or progesterone receptor (P > 0.05). The BMI-1 protein level was positively correlated with the clinical stages of cervical carcinoma and a high BMI-1 expression was associated with poor prognosis (P < 0.05).

CONCLUSION

The high expression of BMI-1 in cervical cancer is related to tumor progression, lymph node metastasis and HPV infection, suggesting that cervical cancer with excessive BMI-1 expression possesses high metastases potential and that BMI-1 may be a promising biomarker for predicting metastasis in cervical cancer.

Polycomb genes and cancer: time for clinical application?

Polycomb group genes (PcGs) are epigenetic effectors, essential for stem cell self-renewal and pluripotency. Two main Polycomb repressive complexes (PRC1, PRC2) mediate gene silencing through histone post-translational modifications. PcGs have been the focus of investigation in cancer research. Many cancer types show an over-expression of PcGs, predicting poor prognosis, metastasis and chemoresistance. Genetic polymorphisms of EZH2 (a PRC2 component) are significantly associated to lung cancer risk. Recently, 3-Deazaneplanocin A (DZNeP) was identified as an efficient inhibitor of PRC2 activity. DZNeP impairs cancer stem cell self-renewal and tumorigenicity. Despite the well-established role of PcGs in cancer stem cell biology, few studies dissected the clinical significance of these genes. In this paper, we explore PcGs as predictive and prognostic factors in oncology, with particular emphasis on what they can add to current biomarkers. We also propose a model for the rational development of DZNeP-based anticancer regimens and suggest the therapeutic applications of this drug.

Organ-specific markers in circulating tumor cell screening: an early indicator of metastasis-capable malignancy

Circulating tumor cells (CTCs) represent an important biological link in the spread of primary solid tumors to the metastatic disease responsible for most cancer mortality. Their detection in the peripheral blood of patients with many different carcinomas has shown that tumor-cell dissemination can proceed at an early stage of tumor development and their presence is associated with poor clinical outcomes, particularly in metastatic disease. In this article we describe how the increasingly sensitive isolation and detailed molecular characterization of CTCs has greatly improved our understanding of metastatic proliferation. We focus on how CTC detection and knowledge of the molecular architecture of these cells can serve as biomarkers to signal metastasis-capable disseminating cells and predict therapy-specific response. This has marked clinical utility for improved selection of systemic therapies to the individual needs of a cancer patient, real-time monitoring of metastatic disease treatments and the development of new targeted therapies.

Detection of circulating Bmi-1 mRNA in plasma and its potential diagnostic and prognostic value for uterine cervical cancer

Bmi-1 is overexpressed in uterine cervical cancer (UCC) and is found to be associated with adverse clinical characteristics and poor prognosis. However, little information is available on the status of circulating Bmi-1 mRNA in UCC. Because circulating cell-free nucleic acids have emerged as a novel class of markers for cancer detection, our research aims to address this question by detecting the circulating Bmi-1 mRNA and to assess its diagnostic and prognostic potential in UCC. Reverse transcription quantitative real-time PCR method was established to detect the circulating Bmi-1 mRNA in plasma of 109 patients with UCC, 138 patients with cervical intraepithelial neoplasia (CIN) and 80 healthy volunteers, and found that it was significantly increased in UCC compared with CINs and healthy controls (all at p < 0.001). Moreover, its high level was significantly correlated with advanced clinical stage (p < 0.001) and positive lymph nodes metastasis (p = 0.002). The area under the receiver operating characteristic curve (AUC) was 0.881, and the optimal cut-off value was 0.057, providing a sensitivity of 69.7% and a specificity of 95.9%. The AUC for circulating Bmi-1 mRNA showed higher diagnosis capability than that for SCC-Ag (p = 0.035) or CA125 (p < 0.001) currently utilized. Kaplan-Meier analysis demonstrated a correlation between increased circulating Bmi-1 mRNA level and reduced disease-free survival (DFS) (p = 0.001) and overall survival (OS) (p = 0.015). And, Cox analysis indicated that it was an independent prognostic factor for DFS and OS. We conclude that circulating Bmi-1 mRNA may be a potential noninvasive molecular marker for diagnosis and prognosis of UCC.

Enzymatic assays for assessing histone deubiquitylation activity

While the post-translational modification of histones by the addition of ubiquitin was discovered decades ago, it has only recently been appreciated that the dynamic regulation of histone ubiquitylation patterns is an important mechanism for controlling a variety of biological processes. The processes include transcription, the recognition and repair of genomic damage and DNA replication, among others. Enzymes that catalyze the addition of ubiquitin to histones, such as the polycomb family, have been well-studied. In contrast, the enzymes that remove ubiquitin from histones are less well understood. The assay strategies described here provide a platform for the thorough in vitro and in vivo analysis of histone deubiquitylation. In some cases, these poorly characterized enzymes are likely to provide new opportunities for therapeutic targeting and a detailed understanding of their biochemical and biological activities is a prerequisite to these clinical advances.

Expression patterns of Bmi-1 and p16 significantly correlate with overall, disease-specific, and recurrence-free survival in oropharyngeal squamous cell carcinoma

BACKGROUND

The objective of this study was to link expression patterns of B-cell-specific Moloney murine leukemia virus integration site 1 (Bmi-1) and p16 to patient outcome (recurrence and survival) in a cohort of 252 patients with oral and oropharyngeal squamous cell cancer (OSCC).

METHODS

Expression levels of Bmi-1 and p16 in samples from 252 patients with OSCC were evaluated immunohistochemically using the tissue microarray method. Staining intensity was determined by calculating an intensity reactivity score (IRS). Staining intensity and the localization of expression within tumor cells (nuclear or cytoplasmic) were correlated with overall, disease-specific, and recurrence-free survival.

RESULTS

The majority of cancers were localized in the oropharynx (61.1%). In univariate analysis, patients who had OSCC and strong Bmi-1 expression (IRS >10) had worse outcomes compared with patients who had low and moderate Bmi-1 expression (P = .008; hazard ratio [HR], 1.82; 95% confidence interval [CI], 1.167-2.838); this correlation was also observed for atypical cytoplasmic Bmi-1 expression (P = .001; HR, 2.164; 95% CI, 1.389-3.371) and for negative p16 expression (P < .001; HR, 0.292; 95% CI, 0.178-0.477). The combination of both markers, as anticipated, had an even stronger correlation with overall survival (P < .001; HR, 8.485; 95% CI, 4.237-16.994). Multivariate analysis demonstrated significant results for patients with oropharyngeal cancers, but not for patients with oral cavity tumors: Tumor classification (P = .011; HR, 1.838; 95%CI, 1.146-2.947) and the combined marker expression patterns (P < .001; HR, 6.254; 95% CI, 2.869-13.635) were correlated with overall survival, disease-specific survival (tumor classification: P = .002; HR, 2.807; 95% CI, 1.477-5.334; combined markers: P = .002; HR, 5.386; 95% CI, 1.850-15.679), and the combined markers also were correlated with recurrence-free survival (P = .001; HR, 8.943; 95% CI, 2.562-31.220).

CONCLUSIONS

Cytoplasmic Bmi-1 expression, an absence of p16 expression, and especially the combination of those 2 predictive markers were correlated negatively with disease-specific and recurrence-free survival in patients with oropharyngeal cancer. Therefore, the current results indicate that these may be applicable as predictive markers in combination with other factors to select patients for more aggressive treatment and follow-up.

Enhancing chemotherapy response with Bmi-1 silencing in ovarian cancer

Undoubtedly ovarian cancer is a vexing, incurable disease for patients with recurrent cancer and therapeutic options are limited. Although the polycomb group gene, Bmi-1 that regulates the self-renewal of normal stem and progenitor cells has been implicated in the pathogenesis of many human malignancies, yet a role for Bmi-1 in influencing chemotherapy response has not been addressed before. Here we demonstrate that silencing Bmi-1 reduces intracellular GSH levels and thereby sensitizes chemoresistant ovarian cancer cells to chemotherapeutics such as cisplatin. By exacerbating ROS production in response to cisplatin, Bmi-1 silencing activates the DNA damage response pathway, caspases and cleaves PARP resulting in the induction apoptosis in ovarian cancer cells. In an in vivo orthotopic mouse model of chemoresistant ovarian cancer, knockdown of Bmi-1 by nanoliposomal delivery significantly inhibits tumor growth. While cisplatin monotherapy was inactive, combination of Bmi-1 silencing along with cisplatin almost completely abrogated ovarian tumor growth. Collectively these findings establish Bmi-1 as an important new target for therapy in chemoresistant ovarian cancer.

Bmi-1 promotes invasion and metastasis, and its elevated expression is correlated with an advanced stage of breast cancer

Background

B-lymphoma Moloney murine leukemia virus insertion region-1 (Bmi-1) acts as an oncogene in various tumors, and its overexpression correlates with a poor outcome in several human cancers. Ectopic expression of Bmi-1 can induce epithelial-mesenchymal transition (EMT) and enhance the motility and invasiveness of human nasopharyngeal epithelial cells (NPECs), whereas silencing endogenous Bmi-1 expression can reverse EMT and reduce the metastatic potential of nasopharyngeal cancer cells (NPCs). Mouse xenograft studies indicate that coexpression of Bmi-1 and H-Ras in breast cancer cells can induce an aggressive and metastatic phenotype with an unusual occurrence of brain metastasis; although, Bmi-1 overexpression did not result in oncogenic transformation of MCF-10A cells. However, the underlying molecular mechanism of Bmi-1-mediated progression and the metastasis of breast cancer are not fully elucidated at this time.

Results

Bmi-1 expression is more pronouncedly increased in primary cancer tissues compared to matched adjacent non-cancerous tissues. High Bmi-1 expression is correlated with advanced clinicopathologic classifications (T, N, and M) and clinical stages. Furthermore, a high level of Bmi-1 indicates an unfavorable overall survival and serves as a high risk marker for breast cancer. In addition, inverse transcriptional expression levels of Bmi-1 and E-cadherin are detected between the primary cancer tissues and the matched adjacent non-cancerous tissues. Higher Bmi-1 levels are found in the cancer tissue, whereas the paired adjacent non-cancer tissue shows higher E-cadherin levels. Overexpression of Bmi-1 increases the motility and invasive properties of immortalized human mammary epithelial cells, which is concurrent with the increased expression of mesenchymal markers, the decreased expression of epithelial markers, the stabilization of Snail and the dysregulation of the Akt/GSK3β pathway. Consistent with these observations, the repression of Bmi-1 in highly metastatic breast cancer cells remarkably reduces cellular motility, invasion and transformation, as well as tumorigenesis and lung metastases in nude mice. In addition, the repression of Bmi-1 reverses the expression of EMT markers and inhibits the Akt/GSK3β/Snail pathway.

Conclusions

This study demonstrates that Bmi-1 promotes the invasion and metastasis of human breast cancer and predicts poor survival.