Expression of BMI-1 and Mel-18 in breast tissue--a diagnostic marker in patients with breast cancer

BMI-1 promotes breast cancer proliferation and metastasis through different mechanisms in different subtypes

Breast cancer is among the most common malignant cancers in women. B-cell-specific Moloney murine leukemia virus integration site 1 (BMI-1) is a transcriptional repressor that has been shown to be involved in tumorigenesis, the cell cycle, and stem cell maintenance. In our study, increased expression of BMI-1 was found in both human triple negative breast cancer and luminal A-type breast cancer tissues compared with adjacent tissues. We also found that knockdown of BMI-1 significantly suppressed cell proliferation and migration in vitro and in vivo. Further mechanistic research demonstrated that BMI-1 directly bound to the promoter region of CDKN2D/BRCA1 and inhibited its transcription in MCF-7/MDA-MB-231. More importantly, we discovered that knockdown of CDKN2D/BRCA1 could promote cell proliferation and migration after repression by PTC-209. Our results reveal that BMI-1 transcriptionally suppressed BRCA1 in TNBC cell lines whereas, in luminal A cell lines, CDKN2D was the target gene. This provides a reference for the precise treatment of different types of breast cancer in clinical practice.

Integrative Biological Network Analysis to Identify Shared Genes in Metabolic Disorders

Identification of common molecular mechanisms in interrelated diseases is essential for better prognoses and targeted therapies. However, complexity of metabolic pathways makes it difficult to discover common disease genes underlying metabolic disorders; and it requires more sophisticated bioinformatics models that combine different types of biological data and computational methods. Accordingly, we built an integrative network analysis model to identify shared disease genes in metabolic syndrome (MS), type 2 diabetes (T2D), and coronary artery disease (CAD). We constructed weighted gene co-expression networks by combining gene expression, protein-protein interaction, and gene ontology data from multiple sources. For 90 different configurations of disease networks, we detected the significant modules by using MCL, SPICi, and Linkcomm graph clustering algorithms. We also performed a comparative evaluation on disease modules to determine the best method providing the highest biological validity. By overlapping the disease modules, we identified 22 shared genes for MS-CAD and T2D-CAD. Moreover, 19 out of these genes were directly or indirectly associated with relevant diseases in the previous medical studies. This study does not only demonstrate the performance of different biological data sources and computational methods in disease-gene discovery, but also offers potential insights into common genetic mechanisms of the metabolic disorders.

Role of MEL-18 Amplification in Anti-HER2 Therapy of Breast Cancer

BACKGROUND

Resistance to HER2-targeted therapy with trastuzumab still remains a major challenge in HER2-amplified tumors. Here we investigated the potential role of MEL-18, a polycomb group gene, as a novel prognostic marker for trastuzumab resistance in HER2-positive (HER2+) breast cancer.

METHODS

The genetic alteration of MEL-18 and its clinical relevance were examined in multiple breast cancer cohorts including METABRIC (n = 1,980), TCGA (n = 825), and our clinical specimens (n = 213, trastuzumab-treated HER2+ cases). MEL-18 amplification was validated by fluorescence in situ hybridization (FISH) analysis. The MEL-18 effect on trastuzumab response was confirmed by in vitro cell viability assays and an in vivo xenograft experiment (n = 7 per group). Gene expression microarray and receptor tyrosine kinase array were performed to identify the trastuzumab resistance mechanism by MEL-18 loss. All statistical tests were two-sided.

RESULTS

MEL-18 was exclusively amplified in approximately 30-50% of HER2+ breast tumors and was associated with a favorable clinical outcome (disease-free survival: P = .02 in HER2+ cases, METABRIC; P = .04 in patients receiving trastuzumab). In MEL-18-amplified HER2+ breast cancer, MEL-18 depletion induced trastuzumab resistance by increasing ADAM sheddase-mediated ErbB ligand production and receptor heterodimerization. MEL-18 epigenetically silenced ADAM10/17 expression in cooperation with polycomb-repressive complex (PRC) 1 and PRC2. Combination treatment with an ADAM10/17 inhibitor and trastuzumab could overcome MEL-18 loss-mediated trastuzumab resistance in vivo (BT474/shMEL-18 xenograft: trastuzumab, mean [SD] tumor volume = 406.1 [50.1] mm3, vs trastuzumab + GW280264 30 mg/kg, mean [SD] tumor volume = 68.4 [15.6] mm3, P < .001). Consistently, trastuzumab-treated patients harboring concomitant MEL-18 amplification and low ADAM17 expression showed prolonged relapse-free survival (P = .02 in our cohort, n = 213).

CONCLUSION

MEL-18 serves to prevent ligand-dependent ErbB heterodimerization and trastuzumab resistance, suggesting MEL-18 amplification as a novel biomarker for HER2+ breast cancer.

Co-inhibition of BMI1 and Mel18 enhances chemosensitivity of esophageal squamous cell carcinoma in vitro and in vivo

Esophageal squamous cell carcinoma (ESCC) accounts for almost 90% of esophageal cancer cases and is the sixth most common cause of cancer-associated mortality worldwide. Cisplatin is the standard therapeutic reagent for ESCC; however, chemoresistance frequently occurs after a few weeks, which leads to ESCC recurrence. Aberrant expression of B lymphoma Mo-MLV insertion region 1 homolog (BMI1) has been reported to activate multiple growth-regulatory pathways, induce antiapoptotic abilities in numerous types of cancer cells and promote chemoresistance. However, to the best of our knowledge, the role of BMI1 in cisplatin-resistant ESCC, and the interaction between BMI1 and its homologue melanoma nuclear protein 18 (Mel18) remain unknown. The present study identified that knockdown of BMI1 promoted cytotoxic effects of cisplatin, and co-inhibition of Mel18 and BMI1 enhanced cisplatin-induced apoptosis and cytotoxicity. Inhibition of BMI1 and Mel18 also suppressed the expression of c-Myc. Furthermore, this combined inhibition sensitized esophageal xenograft tumors to cisplatin to a greater extent compared with BMI1 inhibition alone. In summary, the current study demonstrated that inhibition of BMI1 and Mel18 could increase the sensitivity of esophageal cancer cells to cisplatin via inhibition of c-Myc. Therefore, combined targeting of BMI1 and Mel18 may serve as a promising therapeutic strategy for sensitizing ESCC to chemotherapy.

Mel-18 negatively regulates stem cell-like properties through downregulation of miR-21 in gastric cancer

Mel-18, a polycomb group protein, has been reported to act as a tumor suppressor and be down-regulated in several human cancers including gastric cancer. It was also found that Mel-18 negatively regulates self-renewal of hematopoietic stem cells and breast cancer stem cells (CSCs). This study aimed to clarify its role in gastric CSCs and explore the mechanisms. We found that low-expression of Mel-18 was correlated with poor prognosis and negatively correlated with overexpression of stem cell markers Oct4, Sox2, and Gli1 in 101 gastric cancer tissues. Mel-18 was down-regulated in cultured spheroid cells, which possess CSCs, and overexpression of Mel-18 inhibits cells sphere-forming ability and tumor growth in vivo. Besides, Mel-18 was lower-expressed in ovary metastatic lesions compared with that in primary lesions of gastric cancer, and Mel-18 overexpression inhibited the migration ability of gastric cancer cells. Interestingly, overexpression of Mel-18 resulted in down-regulation of miR-21 in gastric cancer cells and the expression of Mel-18 was negatively correlated with the expression of miR-21 in gastric cancer tissues. Furthermore, miR-21 overexpression partially restored sphere-forming ability, migration potential and chemo-resistance in Mel-18 overexpressing gastric cancer cells. These results suggests Mel-18 negatively regulates stem cell-like properties through downregulation of miR-21 in gastric cancer cells.

Comprehensive analysis of normal adjacent to tumor transcriptomes

Histologically normal tissue adjacent to the tumor (NAT) is commonly used as a control in cancer studies. However, little is known about the transcriptomic profile of NAT, how it is influenced by the tumor, and how the profile compares with non-tumor-bearing tissues. Here, we integrate data from the Genotype-Tissue Expression project and The Cancer Genome Atlas to comprehensively analyze the transcriptomes of healthy, NAT, and tumor tissues in 6506 samples across eight tissues and corresponding tumor types. Our analysis shows that NAT presents a unique intermediate state between healthy and tumor. Differential gene expression and protein–protein interaction analyses reveal altered pathways shared among NATs across tissue types. We characterize a set of 18 genes that are specifically activated in NATs. By applying pathway and tissue composition analyses, we suggest a pan-cancer mechanism of pro-inflammatory signals from the tumor stimulates an inflammatory response in the adjacent endothelium.

Normal tissue adjacent to the tumour (NAT) is often used as a control in cancer studies. Here, the authors analyse across cancer types the transcriptomes of healthy, NAT, and tumour tissues, and find that NAT presents a unique state, potentially due to inflammatory response of the NAT to the tumour tissue.

Expression and Clinicopathological Significance of Mel-18 and Bmi-1 in Esophageal Squamous Cell Carcinoma

The Polycomb group genes are a general class of regulators that are responsible for maintaining homeotic gene expression throughout cell division. Polycomb group expression plays an important role in oncogenesis of several types of human cancer. Melanoma nuclear protein 18 and B-cell-specific Moloney leukemia virus insert site 1 are key Polycomb group proteins. Studies have shown that melanoma nuclear protein 18 is a potential tumor suppression, and B-cell-specific Moloney leukemia virus insert site 1 is overexpressed in several human malignancies. However, the roles of melanoma nuclear protein 18 and B-cell-specific Moloney leukemia virus insert site 1 in esophageal squamous cell carcinoma are still unclear. In this study, we analyzed the expression levels of melanoma nuclear protein 18 and B-cell-specific Moloney leukemia virus insert site 1 in 89 esophageal cancer tissues and paired normal mucosal tissues using immunohistochemistry, Western blotting, and quantitative real-time polymerase chain reaction analyses. We found that the expression of melanoma nuclear protein 18 in the carcinoma tissues was significantly lower than that in the noncancerous mucosal tissues (P < .05), and B-cell-specific Moloney leukemia virus insert site 1 expression in the carcinoma tissues was significantly higher than that in the noncancerous mucosal tissues (P < .05). In addition, the expression of melanoma nuclear protein 18 was correlated with clinical stage, depth of invasion, and lymph node metastasis (P < .05) but was not correlated with gender, age, degree of differentiation, or disease-free survival (P > .05). B-cell-specific Moloney leukemia virus insert site 1 expression was strongly correlated with the degree of differentiation, clinical stage, and lymph node metastasis (P <.05) but was not correlated with the gender, age, depth of invasion or disease-free survival (P > .05). Moreover, there was a negative correlation between melanoma nuclear protein 18 and B-cell-specific Moloney leukemia virus insert site 1 expressions in esophageal squamous cell carcinoma (P < .05). Our study suggests that melanoma nuclear protein 18 and B-cell-specific Moloney leukemia virus insert site 1 may play a crucial role in esophageal squamous cell carcinoma. Melanoma nuclear protein 18 or B-cell-specific Moloney leukemia virus insert site 1 may be a potential biomarker for diagnosis and prognosis of esophageal squamous cell carcinoma.

Control of stress signaling in stem cells: crossroads of stem cells and cancer

Tumorigenesis is a relatively rare event in the human body considering the enormous number of cells composing our body and the frequent occurrence of genetic mutations in each cell. Nevertheless, the cells that happen to meet the minimum requirements can be transformed when stressed by a variety of oncogenic stimulations, then progress to form tumors. The vigorous competition between oncogenic signaling and tumor-suppressor defense is a critical determinant of cellular fate, which can be either tumorigenic transformation or cellular senescence/apoptosis depending on "who wins the battle." Recently, a number of cancers have been reported to originate from stem cells, whose self-renewing properties are normally reduced by innate tumor suppressors. Therefore, exploring the innate mechanism by which stem cells modulate tumor suppressors to maintain their "stemness" may provide valuable clues to characterize the distinctive oncogenic susceptibility of stem cells. This review is focused on the recent advances in the field of tumorigenesis of stem cells and on the associated molecular mechanisms.

The evolutionary landscape of PRC1 core components in green lineage

The origin and evolution of plant PRC1 core components. Polycomb repressive complex1 (PRC1) plays critical roles in epigenetic silencing of homeotic genes and determination of cell fate. Animal PRC1 has been well investigated for a long time, whereas plant PRC1 was just confirmed in recent years. It is enigmatic whether PRC1 core components in plants share a common ancestor with those in animals. We evaluated the origin of plant PRC1 RING-finger proteins (RING1 and BMI1) through comparing with the homologs in some representative unikonts and using BMI1- and RING1-like proteins as reciprocal outgroup, finding both PRC1 RING-finger proteins have the earliest origin in mosses, similar to LHP1. Additionally, the gene structure, copy number, and domain organization were analyzed to deeply understand the evolutionary history of plant PRC1 complex. In conclusion, PRC1 RING-finger proteins have independent origins in plants and animals, but convergent evolution might attribute to the conservation of PRC1 complex in plants and animals. Plant LHP1 as the homolog of non-PRC1 protein HP1 was recruited to fulfill the role of Pc counterpart. Gene duplication followed by functional divergence makes a great contribution to evolutionary progress of PRC1 in green plants.

HSP90 inhibits apoptosis and promotes growth by regulating HIF-1α abundance in hepatocellular carcinoma

Heat shock protein (HSP)90 functions as a general oncogene by targeting several well-known oncoproteins for ubiquination and proteasomal degradation. However, the clinical significance of HSP90, as well as the mechanisms responsible for the tumor-promoting effects of HSP90 in hepatocellular carcinoma (HCC) remain unclear. In this study, HSP90 and hypoxia-inducible factor (HIF)-1α expression in 60 samples of HCC tissues and matched normal tumor-adjacent tissue were assessed using immunohistochemistry (IHC) or western blot analysis. Flow cytometry, BrdU cell proliferation assay, caspase-3/7 activity assay and MTT assay were used to detect the apoptosis and proliferation of the HCC cells. The regulatory effect of HSP90 on HIF-1α in the HCC cells was confirmed by immunofluorescence staining, western blot analysis and RT-qPCR. The interaction between HIF-1α and HSP90 was analyzed by co-immunoprecipitation. A subcutaneous tumor xenograft model in nude mice was established and TUNEL assay was performed to evaluate cancer cell apoptosis and growth in vivo. We found that HSP90 expression was higher in the HCC tissues than in the normal tissues and that a high HSP90 expression correlated with poor clinicopathological characteristics, including venous infiltration, an advanced TNM stage and high pathological grading. Furthermore, we confirmed that patients with a negative expression of HSP90 had an improved 3-year survival, and that HSP90 was an independent factor for predicting the prognosis of patients with HCC. We demonstrated that HSP90 promoted HCC by inhibiting apoptosis and promoting cancer cell growth. Pearson's correlation coefficient analysis indicated that HSP90 expression positively correlated with HIF-1α protein expression in the HCC tissues. Furthermore, we found that HSP90 regulated HIF-1α protein abundance by inhibiting the ubiquitination and proteasomal degradation of HIF-1α in HCC cells. Additionally, the upregulation of HIF-1α expression partially abrogated HSP90 siRNA-induced HCC cell growth arrest and apoptosis in vitro and in vivo. These results indicate that HSP90 may be used as a prognostic marker and that HIF-1α may be one of the potential therapeutic targets of HSP90 in HCC.

MEL-18 loss mediates estrogen receptor-α downregulation and hormone independence

The polycomb protein MEL-18 has been proposed as a tumor suppressor in breast cancer; however, its functional relevance to the hormonal regulation of breast cancer remains unknown. Here, we demonstrated that MEL-18 loss contributes to the hormone-independent phenotype of breast cancer by modulating hormone receptor expression. In multiple breast cancer cohorts, MEL-18 was markedly downregulated in triple-negative breast cancer (TNBC). MEL-18 expression positively correlated with the expression of luminal markers, including estrogen receptor-α (ER-α, encoded by ESR1). MEL-18 loss was also associated with poor response to antihormonal therapy in ER-α-positive breast cancer. Furthermore, whereas MEL-18 loss in luminal breast cancer cells resulted in the downregulation of expression and activity of ER-α and the progesterone receptor (PR), MEL-18 overexpression restored ER-α expression in TNBC. Consistently, in vivo xenograft experiments demonstrated that MEL-18 loss induces estrogen-independent growth and tamoxifen resistance in luminal breast cancer, and that MEL-18 overexpression confers tamoxifen sensitivity in TNBC. MEL-18 suppressed SUMOylation of the ESR1 transactivators p53 and SP1, thereby driving ESR1 transcription. MEL-18 facilitated the deSUMOylation process by inhibiting BMI-1/RING1B-mediated ubiquitin-proteasomal degradation of SUMO1/sentrin-specific protease 1 (SENP1). These findings demonstrate that MEL-18 is a SUMO-dependent regulator of hormone receptors and suggest MEL-18 expression as a marker for determining the antihormonal therapy response in patients with breast cancer.

Immunohistochemical expression and prognostic relevance of Bmi-1, a stem cell factor, in epithelial ovarian cancer

Ovarian cancer is the fourth most common cause of cancer-related death in women. Bmi-1 is a stem cell factor implicated in many human malignancies with poor outcome. Few published reports on the expression of Bmi-1 in epithelial ovarian cancer were either experimental or performed on cell lines. This study evaluates the immunohistochemical expression of Bmi-1 protein in epithelial ovarian cancer tissue specimens and its relevance to the clinicopathologic prognostic variables and patient survival. Forty cases of epithelial ovarian cancer were selected according to the availability of paraffin-embedded tissue and the clinicopathologic and survival data. Immunohistochemistry was performed for anti-Bmi-1 antibody. Low and high Bmi-1 expression groups were compared with age, tumor stage, laterality, grade, histology, and patient survival. Bmi-1 expression was detected in 72.5% of cases, of which 42.5% had high expression. High Bmi-1 expression strongly associated with advanced International Federation of Gynecology and Obstetrics stages (P = .007), bilaterality (P = .01), and higher Gynecologic Oncology Group grades (P = .031) and carcinomas of serous histology (P = .027). It had no association with patient age. Bmi-1 expression displayed a significant inverse association with patient overall and mean survival (P = .006, P < .001). These observations suggested correlation between increased Bmi-1 expression and clinical progression in ovarian epithelial cancer.

Individual and combined effects of DNA methylation and copy number alterations on miRNA expression in breast tumors

Background

The global effect of copy number and epigenetic alterations on miRNA expression in cancer is poorly understood. In the present study, we integrate genome-wide DNA methylation, copy number and miRNA expression and identify genetic mechanisms underlying miRNA dysregulation in breast cancer.

Results

We identify 70 miRNAs whose expression was associated with alterations in copy number or methylation, or both. Among these, five miRNA families are represented. Interestingly, the members of these families are encoded on different chromosomes and are complementarily altered by gain or hypomethylation across the patients. In an independent breast cancer cohort of 123 patients, 41 of the 70 miRNAs were confirmed with respect to aberration pattern and association to expression. In vitro functional experiments were performed in breast cancer cell lines with miRNA mimics to evaluate the phenotype of the replicated miRNAs. let-7e-3p, which in tumors is found associated with hypermethylation, is shown to induce apoptosis and reduce cell viability, and low let-7e-3p expression is associated with poorer prognosis. The overexpression of three other miRNAs associated with copy number gain, miR-21-3p, miR-148b-3p and miR-151a-5p, increases proliferation of breast cancer cell lines. In addition, miR-151a-5p enhances the levels of phosphorylated AKT protein.

Conclusions

Our data provide novel evidence of the mechanisms behind miRNA dysregulation in breast cancer. The study contributes to the understanding of how methylation and copy number alterations influence miRNA expression, emphasizing miRNA functionality through redundant encoding, and suggests novel miRNAs important in breast cancer.

In aggressive variants of non-Hodgkin lymphomas, Ezh2 is strongly expressed and polycomb repressive complex PRC1.4 dominates over PRC1.2

Polycomb group (PcG) proteins are important for the regulation of hematopoiesis by regulating chromatin compaction and silencing genes related to differentiation and cell cycle. Overexpression of enhancer of zeste homologue 2 (Ezh2) and Bmi-1/PCGF4 has been implicated in solid organ cancers, while Mel-18/PCGF2 has been reported as a tumor suppressor. Detailed expression profiles of PcG proteins and their diagnostic significance in malignant lymphomas are still unknown. In this study, we analyzed the expression levels of Ezh2, Bmi-1, Mel-18, and Ki67 in 197 Hodgkin's and non-Hodgkin's lymphoma patient samples and in lymphoma cell lines using immunohistochemistry, fluorescent immunocytochemistry, and Western blotting. Immunohistochemical staining showed that Ezh2 expression was significantly increased in aggressive compared to indolent subtypes of B cell neoplasms (P = 0.000-0.030), while no significant differences in Bmi-1 expression were found between these subtypes. Compared to the normal counterpart, T cell lymphomas showed significant overexpression of Bmi-1 (P = 0.011) and Ezh2 (P = 0.000). The Ki67 labeling index showed a positive correlation with Ezh2 expression in B cell lymphomas (correlation coefficient (Co) = 0.983, P = 0.000) and T/NK cell lymphomas (Co = 0.629, P = 0.000). Fluorescent immunohistochemical staining showed coexpression of Ezh2 and Ki67 in the same tumor cells, indicating that Ezh2 expression correlates with cell proliferation. Both B and T/NK cell neoplasms showed low expression of Mel-18 and high expression of both Bmi-1 and Ezh2. In conclusion, in aggressive lymphoma variants, Ezh2 is strongly expressed and polycomb repressive complex PRC1.4 dominates over PRC1.2. Coexpression of Bmi-1 and Ezh2 is a characteristic of aggressive lymphomas. Ezh2 correlates with the proliferation and aggressive nature of non-Hodgkin's lymphomas.

In aggressive variants of non-Hodgkin lymphomas, Ezh2 is strongly expressed and polycomb repressive complex PRC1.4 dominates over PRC1.2

Polycomb group (PcG) proteins are important for the regulation of hematopoiesis by regulating chromatin compaction and silencing genes related to differentiation and cell cycle. Overexpression of enhancer of zeste homologue 2 (Ezh2) and Bmi-1/PCGF4 has been implicated in solid organ cancers, while Mel-18/PCGF2 has been reported as a tumor suppressor. Detailed expression profiles of PcG proteins and their diagnostic significance in malignant lymphomas are still unknown. In this study, we analyzed the expression levels of Ezh2, Bmi-1, Mel-18, and Ki67 in 197 Hodgkin's and non-Hodgkin's lymphoma patient samples and in lymphoma cell lines using immunohistochemistry, fluorescent immunocytochemistry, and Western blotting. Immunohistochemical staining showed that Ezh2 expression was significantly increased in aggressive compared to indolent subtypes of B cell neoplasms (P = 0.000-0.030), while no significant differences in Bmi-1 expression were found between these subtypes. Compared to the normal counterpart, T cell lymphomas showed significant overexpression of Bmi-1 (P = 0.011) and Ezh2 (P = 0.000). The Ki67 labeling index showed a positive correlation with Ezh2 expression in B cell lymphomas (correlation coefficient (Co) = 0.983, P = 0.000) and T/NK cell lymphomas (Co = 0.629, P = 0.000). Fluorescent immunohistochemical staining showed coexpression of Ezh2 and Ki67 in the same tumor cells, indicating that Ezh2 expression correlates with cell proliferation. Both B and T/NK cell neoplasms showed low expression of Mel-18 and high expression of both Bmi-1 and Ezh2. In conclusion, in aggressive lymphoma variants, Ezh2 is strongly expressed and polycomb repressive complex PRC1.4 dominates over PRC1.2. Coexpression of Bmi-1 and Ezh2 is a characteristic of aggressive lymphomas. Ezh2 correlates with the proliferation and aggressive nature of non-Hodgkin's lymphomas.

The role of maintenance proteins in the preservation of epithelial cell identity during mammary gland remodeling and breast cancer initiation

During normal postnatal mammary gland development and adult remodeling related to the menstrual cycle, pregnancy, and lactation, ovarian hormones and peptide growth factors contribute to the delineation of a definite epithelial cell identity. This identity is maintained during cell replication in a heritable but DNA-independent manner. The preservation of cell identity is fundamental, especially when cells must undergo changes in response to intrinsic and extrinsic signals. The maintenance proteins, which are required for cell identity preservation, act epigenetically by regulating gene expression through DNA methylation, histone modification, and chromatin remodeling. Among the maintenance proteins, the Trithorax (TrxG) and Polycomb (PcG) group proteins are the best characterized. In this review, we summarize the structures and activities of the TrxG and PcG complexes and describe their pivotal roles in nuclear estrogen receptor activity. In addition, we provide evidence that perturbations in these epigenetic regulators are involved in disrupting epithelial cell identity, mammary gland remodeling, and breast cancer initiation.

Knockdown BMI1 expression inhibits proliferation and invasion in human bladder cancer T24 cells

B cell-specific moloney murine leukemia virus integration site 1 (BMI1) is a transcriptional repressor of polycomb repressive complex 1, which is involved in the proliferation, senescence, migration, and tumorigenesis of cancer. Experimental researchers have convincingly linked BMI1 to tumorigenesis. However, there is no study about the issue on the role of BMI1 in the proliferation, apoptosis, and migration of bladder cancer. To address this question, we examined the expression of BMI1 in bladder cancer tissues and used siRNA to knockdown BMI1 expression in bladder cancer T24 cells. Then we tested the cell proliferation by CCK8 assay and soft agar colony formation assay, apoptosis by flow cytometry assay, and cell invasiveness by transwell migration assay. Our results revealed that BMI1 promoted proliferation, migration, invasion, and progression in bladder cancer. Over-expression of BMI1 was correlated with tumor clinic-pathological features. BMI1 siRNA effectively inhibited bladder cancer cell proliferation and migration in vitro, and it promoted bladder cancer invasion, maybe by causing epithelial-to-mesenchymal transition. Our findings suggested that BMI1 may represent a novel diagnostic marker and a therapeutic target for bladder cancer, and deserves further investigation.

Significance of expression of Bmi-1 and Mel-18 in colorectal carcinoma

AIM: To investigate the relationship between the expression of Bmi-1 and Mel-18 and clinicopathological features of colorectal carcinoma.

METHODS: Sixty-eight colorectal cancer samples and matched tumor-adjacent normal tissue samples were collected to detect the expression of Bmi-1 and Mel-18 using immunohistochemistry. The relationship between the abnormal expression of Bmi-1 and Mel-18 and the clinicopathological features of colorectal carcinoma was analyzed.

RESULTS: The positive rate of Bmi-1 expression was significantly higher in colorectal carcinoma than in normal colon tissue (P < 0.05), and expression of Bmi-1 was correlated with the depth of bowel wall invasion, lymph node metastasis and Dukes stage (all P < 0.05). The positive rate of Mel-18 expression was significantly lower in colorectal carcinoma than in normal colon tissue (P < 0.05), and expression of Mel-18 was negatively related to lymph node metastasis and Dukes stage (both P < 0.05). There was a negative correlation between the expression of Bmi-1 and Mel-18 in colorectal carcinoma (r = -0.335, P < 0.05).

CONCLUSION: The expression of Bmi-1 and Mel-18 proteins correlates with the progression, metastasis and prognosis of colorectal cancer. Combined detection of Bmi-1 and Mel-18 protein expression may be helpful to the diagnosis and evaluation of the malignancy of colorectal carcinoma.

Cancer stem cell marker Bmi-1 expression is associated with basal-like phenotype and poor survival in breast cancer

BACKGROUND

The purpose of present study was to examine the expression of cancer stem cell marker Bmi-1 in breast cancer tissue and to evaluate the clinical implication of Bmi-1 expression for these patients.

METHODS

A total of 171 breast cancer patients who received surgical treatment in our hospital were enrolled in this study. Bmi-1 expression in breast cancer tissue was assayed by immunohistochemistry. Statistical analyses were applied to test the relationship between expression of Bmi-1 and clinicopathologic features and patient survival. The relationship between Bmi-1 and the basal-like phenotype of breast cancer also was analyzed in this study.

RESULTS

Positive Bmi-1 expression was detected in 89 of 171 (52%) invasive breast cancers patients. The Bmi-1 status was significantly correlated to histological grade III (p = 0.001) and basal-like phenotype (p < 0.001). The 5 year overall survival of the patients with Bmi-1-positive and -negative cancers were 78 and 91.9%, respectively (p = 0.03). Histological grade (p = 0.046) and Bmi-1 status (p = 0.012) were detected as the independent prognostic factors in the Cox regression test.

CONCLUSIONS

Bmi-1 status is an independent prognostic factor, which also is associated with tumor histological grade and basal-like phenotype. The high proportions of positive Bmi-1 expression in basal-like breast cancer may be related to the high aggressiveness behavior of this subtype of breast cancer.

Characterization of mammary cancer stem cells in the MMTV-PyMT mouse model

Breast cancer stem cells, the root of tumor growth, present challenges to investigate: Primary human breast cancer cells are difficult to establish in culture and inconsistently yield tumors after transplantation into immune-deficient recipient mice. Furthermore, there is limited characterization of mammary cancer stem cells in mice, the ideal model for the study of breast cancer. We herein describe a pre-clinical breast cancer stem cell model, based on the properties of cancer stem cells, derived from transgenic MMTV-PyMT mice. Using a defined set of cell surface markers to identify cancer stem cells by flow cytometry, at least four cell populations were recovered from primary mammary cancers. Only two of the four populations, one epithelial and one mesenchymal, were able to survive and proliferate in vitro. The epithelial population exhibited tumor initiation potential with as few as 10 cells injected into syngeneic immune-competent recipients. Tumors initiated from injected cell lines recapitulated the morphological and physiological components of the primary tumor. To highlight the stemness potential of the putative cancer stem cells, B lymphoma Mo-MLV insertion region 1 homolog (Bmi-1) expression was knocked down via shRNA targeting Bmi-1. Without Bmi-1 expression, putative cancer stem cells could no longer initiate tumors, but tumor initiation was rescued with the introduction of a Bmi-1 overexpression vector in the Bmi-1 knockdown cells. In conclusion, our data show that primary mammary cancers from MMTV-PyMT mice contain putative cancer stem cells that survive in culture and can be used to create a model for study of mammary cancer stem cells.

Cancer stem cell marker Bmi-1 expression is associated with basal-like phenotype and poor survival in breast cancer

BACKGROUND

The purpose of present study was to examine the expression of cancer stem cell marker Bmi-1 in breast cancer tissue and to evaluate the clinical implication of Bmi-1 expression for these patients.

METHODS

A total of 171 breast cancer patients who received surgical treatment in our hospital were enrolled in this study. Bmi-1 expression in breast cancer tissue was assayed by immunohistochemistry. Statistical analyses were applied to test the relationship between expression of Bmi-1 and clinicopathologic features and patient survival. The relationship between Bmi-1 and the basal-like phenotype of breast cancer also was analyzed in this study.

RESULTS

Positive Bmi-1 expression was detected in 89 of 171 (52%) invasive breast cancers patients. The Bmi-1 status was significantly correlated to histological grade III (p = 0.001) and basal-like phenotype (p < 0.001). The 5 year overall survival of the patients with Bmi-1-positive and -negative cancers were 78 and 91.9%, respectively (p = 0.03). Histological grade (p = 0.046) and Bmi-1 status (p = 0.012) were detected as the independent prognostic factors in the Cox regression test.

CONCLUSIONS

Bmi-1 status is an independent prognostic factor, which also is associated with tumor histological grade and basal-like phenotype. The high proportions of positive Bmi-1 expression in basal-like breast cancer may be related to the high aggressiveness behavior of this subtype of breast cancer.

Cancer stem cell marker Bmi-1 expression is associated with basal-like phenotype and poor survival in breast cancer

BACKGROUND

The purpose of present study was to examine the expression of cancer stem cell marker Bmi-1 in breast cancer tissue and to evaluate the clinical implication of Bmi-1 expression for these patients.

METHODS

A total of 171 breast cancer patients who received surgical treatment in our hospital were enrolled in this study. Bmi-1 expression in breast cancer tissue was assayed by immunohistochemistry. Statistical analyses were applied to test the relationship between expression of Bmi-1 and clinicopathologic features and patient survival. The relationship between Bmi-1 and the basal-like phenotype of breast cancer also was analyzed in this study.

RESULTS

Positive Bmi-1 expression was detected in 89 of 171 (52%) invasive breast cancers patients. The Bmi-1 status was significantly correlated to histological grade III (p = 0.001) and basal-like phenotype (p < 0.001). The 5 year overall survival of the patients with Bmi-1-positive and -negative cancers were 78 and 91.9%, respectively (p = 0.03). Histological grade (p = 0.046) and Bmi-1 status (p = 0.012) were detected as the independent prognostic factors in the Cox regression test.

CONCLUSIONS

Bmi-1 status is an independent prognostic factor, which also is associated with tumor histological grade and basal-like phenotype. The high proportions of positive Bmi-1 expression in basal-like breast cancer may be related to the high aggressiveness behavior of this subtype of breast cancer.

BMI-1 autoantibody as a new potential biomarker for cervical carcinoma

BMI-1 is overexpressed in a variety of cancers, which can elicit an immune response leading to the induction of autoantibodies. However, BMI-1 autoantibody as a biomarker has seldom been studied with the exception of nasopharyngeal carcinoma. Whether BMI-1 autoantibodies can be used as a biomarker for cervical carcinoma is unclear. In this study,BMI-1 proteins were isolated by screening of a T7 phage cDNA library from mixed cervical carcinoma tissues. We analyzed BMI-1 autoantibody levels in serum samples from 67 patients with cervical carcinoma and 65 controls using ELISA and immunoblot. BMI-1 mRNA or protein levels were over-expressed in cervical carcinoma cell lines. Immunoblot results exhibited increased BMI-1 autoantibody levels in patient sera compared to normal sera. Additionally, the results for antibody affinity assay showed that there was no difference between cervical polyps and normal sera of BMI-1 autoantibody levels, but it was significantly greater in patient sera than that in normal controls (patient 0.827±0.043 and normal 0.445±0.023; P<0.001). What's more, the levels of BMI-1 autoantibody increased significantly at stage I (0.672±0.019) compared to normal sera (P<0.001), and levels of BMI-1 autoantibodies were increased gradually during the tumor progression (stage I 0.672±0.019; stage II 0.775 ±0.019; stage III 0.890 ±0.027; stage IV 1.043±0.041), which were significantly correlated with disease progression of cervical cancer (P<0.001). Statistical analyses using logistic regression and receiver operating characteristics (ROC) curves indicated that the BMI-1 autoantibody level can be used as a biomarker for cervical carcinoma (sensitivity 0.78 and specificity 0.76; AUC = 0.922). In conclusion, measuring BMI-1 autoantibody levels of patients with cervical cancer could have clinical prognostic value as well as a non-tissue specific biomarker for neoplasms expressing BMI-1.