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

The Endogenous Expression of BMI1 in Adult Human Eyes

BMI1, also known as B lymphoma Mo-MLV insertion region 1, is a protein in the Polycomb group that is implicated in various cellular processes, including stem cell self-renewal and the regulation of cellular senescence. BMI1 plays a role in the regulation of retinal progenitor cells and the renewal of adult neuronal cells. However, the presence, location, and quantification of BMI1 in the adult human eye have never previously been reported. In this study, we collected 45 frozen globes from eye banks, and ocular tissues were dissected. Protein was quantified by utilizing a custom electrochemiluminescence (ECL) assay developed to quantify the BMI1 protein. BMI1 was found in all ocular tissues at the following levels: the retina (1483.6 ± 191.7 pg/mL) and the RPE (296.4 ± 78.1 pg/mL). BMI1 expression was noted ubiquitously in the GCL (ganglion cell layer), the INL (inner nuclear layer), the ONL (outer nuclear layer), and the RPE (retinal pigment epithelium) via immunofluorescence, with higher levels in the inner than in the outer retinal layers and the RPE. These data confirm that BMI1 is expressed in the human retina. Further studies will illuminate the role that BMI1 plays in ocular cells. BMI1 levels are lower in aged retinas, possibly reflecting changes in retinal somatic and stem cell maintenance and disease susceptibility.

Polycomb Repressor Complex 1 (PRC1) in ovarian cancer: A scoping literature review

High grade serous carcinoma (HGSC) is the most common and the deadliest histologic subtype of epithelial ovarian cancer. HGSC is a therapeutic challenge, as it recurs in 80 % of patients diagnosed, often as chemoresistant disease. The mechanism of this chemoresistance is not fully elucidated, but it is partly attributed to the ability of HGSC to maintain a stem-like phenotype that enables development of resistance to current therapies. Polycomb Repressor Complexes 1 and 2 (PRC1/2) have been implicated in the maintenance of the stem cell compartment through silencing tumor suppressor genes and regulating stem cells. These complexes are comprised of multiple polycomb group (PcG) proteins that play a role in normal development, and when deregulated contribute to the development of cancer [2]. Proteins included in PRC1 include B lymphoma mouse Moloney leukemia virus insertion region (BMI1), RING1, and chromobox (CBX) proteins. We aimed to review each of the protein components of PRC1 and their mechanistic relationships to promoting chemoresistant recurrences and propagation of ovarian cancer. Where possible, we reviewed therapeutic investigations of these proteins. We utilized a scoping literature review through Covidence to identify 42 articles meeting criteria for inclusion. The authors identified four relevant articles and the Yale MeSH Analysis Grid Generator was used to establish additional keywords and heading terms. A medical librarian used these terms and articles to draft an initial search strategy within each of the following databases: MEDLINE, Embase, Cochrane Library, and Web of Science Core Collection, yielding 439 articles based on title and abstract. Abstracts were independently reviewed by the authors, identifying 77 articles for full text review, of which 35 were ultimately excluded, leaving 42 articles for full review. Our review identified the currently known mechanisms of the subunits of PRC1 that contribute to HGSC development, recurrence, and chemoresistance. By compiling a comprehensive review of available scientific knowledge, we support and direct further investigation into PRC1 that can affect meaningful advances in the treatment of HGSC.

An Overview of Ovarian Cancer: The Role of Cancer Stem Cells in Chemoresistance and a Precision Medicine Approach Targeting the Wnt Pathway with the Antagonist sFRP4

Ovarian cancer is one of the most prevalent gynecological cancers, having a relatively high fatality rate with a low five-year chance of survival when detected in late stages. The early detection, treatment and prevention of metastasis is pertinent and a pressing research priority as many patients are diagnosed only in stage three of ovarian cancer. Despite surgical interventions, targeted immunotherapy and adjuvant chemotherapy, relapses are significantly higher than other cancers, suggesting the dire need to identify the root cause of metastasis and relapse and present more precise therapeutic options. In this review, we first describe types of ovarian cancers, the existing markers and treatment modalities. As ovarian cancer is driven and sustained by an elusive and highly chemoresistant population of cancer stem cells (CSCs), their role and the associated signature markers are exhaustively discussed. Non-invasive diagnostic markers, which can be identified early in the disease using circulating tumor cells (CTCs), are also described. The mechanism of the self-renewal, chemoresistance and metastasis of ovarian CSCs is regulated by the Wnt signaling pathway. Thus, its role in ovarian cancer in promoting stemness and metastasis is delineated. Based on our findings, we propose a novel strategy of Wnt inhibition using a well-known Wnt antagonist, secreted frizzled related protein 4 (sFRP4), wherein short micropeptides derived from the whole protein can be used as powerful inhibitors. The latest approaches to early diagnosis and novel treatment strategies emphasized in this review will help design precision medicine approaches for an effective capture and destruction of highly aggressive ovarian cancer.

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

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

Resveratrol Contrasts LPA-Induced Ovarian Cancer Cell Migration and Platinum Resistance by Rescuing Hedgehog-Mediated Autophagy

Background: Ovarian cancer progression and invasiveness are promoted by a range of soluble factors released by cancer cells and stromal cells within the tumor microenvironment. Our previous studies demonstrated that resveratrol (RV), a nutraceutical and caloric restriction mimetic with tumor-suppressive properties, counteracts cancer cell motility induced by stromal IL-6 by upregulating autophagy. Lysophosphatidic acid (LPA), a bioactive phospholipid that shows elevated levels in the tumor microenvironment and the ascites of ovarian cancers, stimulates the growth and tissue invasion of cancer cells. Whether LPA elicits these effects by inhibiting autophagy and through which pathway and whether RV can counteract the same remain obscure. Aims: To investigate the molecular pathways involved in LPA-induced ovarian cancer malignancy, particularly focusing on the role of autophagy, and the ability of RV to counteract LPA activity. Results: LPA stimulated while RV inhibited ovarian cancer cell migration. Transcriptomic and bioinformatic analyses showed an opposite regulation by LPA and RV of genes linked to epithelial-to-mesenchymal transition (EMT) and autophagy with involvement of the PI3K-AKT, JAK-STAT and Hedgehog (Hh) pathways. LPA upregulated the Hh and EMT members GLI1, BMI-1, SNAIL-1 and TWIST1 and inhibited autophagy, while RV did the opposite. Similar to the inhibitors of the Hh pathway, RV inhibited LPA-induced cancer cell migration and 3D growth of ovarian cancer cells. BMI-1 silencing prevented LPA-induced EMT, restored autophagy and hampered cell migration, resembling the effects of RV. TCGA data analyses indicated that patients with low expression of Hh/EMT-related genes together with active autophagy flux tended to have a better prognosis and this correlates with a more effective response to platinum therapy. In in vitro 3D spheroids, LPA upregulated BMI-1, downregulated autophagy and inhibited platinum toxicity while RV and Hh inhibitors restored autophagy and favored BAX-mediated cell death in response to platinum. Conclusions: By inhibiting the Hh pathway and restoration of autophagy, RV counteracts LPA-induced malignancy, supporting its inclusion in the therapy of ovarian cancer for limiting metastasis and chemoresistance.

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.

ALDH1A1-related stemness in high-grade serous ovarian cancer is a negative prognostic indicator but potentially targetable by EGFR/mTOR-PI3K/aurora kinase inhibitors

Poor chemotherapy response remains a major treatment challenge for high-grade serous ovarian cancer (HGSC). Cancer stem cells are the major contributors to relapse and treatment failure as they can survive conventional therapy. Our objectives were to characterise stemness features in primary patient-derived cell lines, correlate stemness markers with clinical outcome and test the response of our cells to both conventional and exploratory drugs. Tissue and ascites samples, treatment-naive and/or after neoadjuvant chemotherapy, were prospectively collected. Primary cancer cells, cultured under conditions favouring either adherent or spheroid growth, were tested for stemness markers; the same markers were analysed in tissue and correlated with chemotherapy response and survival. Drug sensitivity and resistance testing was performed with 306 oncology compounds. Spheroid growth condition HGSC cells showed increased stemness marker expression (including aldehyde dehydrogenase isoform I; ALDH1A1) as compared with adherent growth condition cells, and increased resistance to platinum and taxane. A set of eight stemness markers separated treatment-naive tumours into two clusters and identified a distinct subgroup of HGSC with enriched stemness features. Expression of ALDH1A1, but not most other stemness markers, was increased after neoadjuvant chemotherapy and its expression in treatment-naive tumours correlated with chemoresistance and reduced survival. In drug sensitivity and resistance testing, five compounds, including two PI3K-mTOR inhibitors, demonstrated significant activity in both cell culture conditions. Thirteen compounds, including EGFR, PI3K-mTOR and aurora kinase inhibitors, were more toxic to spheroid cells than adherent cells. Our results identify stemness markers in HGSC that are associated with a decreased response to conventional chemotherapy and reduced survival if expressed by treatment-naive tumours. EGFR, mTOR-PI3K and aurora kinase inhibitors are candidates for targeting this cell population. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Integrin α7 correlates with worse clinical features and prognosis, and its knockdown inhibits cell proliferation and stemness in tongue squamous cell carcinoma

The present study aimed to evaluate the correlation of integrin α7 (ITGA7) with clinicopathological characteristics and overall survival (OS) in patients with tongue squamous cell carcinoma (TSCC), and to investigate the effect of ITGA7 knockdown on proliferation, apoptosis and stemness of TSCC cells in vitro. ITGA7 expression was measured in tumor tissues and paired adjacent normal tissues from 60 patients with TSCC using immunohistochemistry. ITGA7 expression in human TSCC cell lines and normal oral keratinocytes was measured using quantitative PCR and western blotting. Lentiviruses carrying short hairpin (sh) RNA targeting ITGA7 were used to knockdown its expression in CAL-27 and HSC-4 cells, and then proliferation, apoptosis and stemness were measured. In addition, CAL-27 and HSC-4 cancer stem cells (CSCs) were constructed and their ITGA7 expression was measured. The results demonstrated that ITGA7 was upregulated in the tumor tissues compared with the paired adjacent tissues, and its high expression was correlated with worse pathological grade, N stage, TNM stage and OS. In vitro, ITGA7 expression levels were demonstrated to be increased in the TSCC CAL-27, SCC-9, HSC-4 and SCC-25 cell lines compared to the normal HOK cell line. In CAL-27 and HSC-4 cells, ITGA7 knockdown inhibited cell proliferation, promoted apoptosis, increased CD24 expression, decreased CD44 and CD133 expression, reduced drug resistance to cisplatin and attenuated sphere formation efficiency. Finally, ITGA7 expression levels were greatly elevated in CAL-27 and HSC-4 CSCs compared with parental CAL-27 and HSC-4 cells. In conclusion, ITGA7 knockdown inhibited tumor cell proliferation and stemness in TSCC cells. These findings indicated that ITGA7 might serve as a potential marker for CSCs and may correlate with worse clinical features and prognosis in TSCC.

Integrin α7 is overexpressed and correlates with higher pathological grade, increased T stage, advanced TNM stage as well as worse survival in clear cell renal cell carcinoma patients: A retrospective study

OBJECTIVE

This study aimed to explore the association of integrin α7 with clinicopathological characteristics and overall survival (OS) in clear cell renal cell carcinoma (ccRCC) patients.

METHODS

179 ccRCC patients who underwent nephrectomy were included in this retrospective study. Tumor tissue and paired adjacent tissue specimens of patients were obtained. Immunohistochemistry assay was performed to detect integrin α7 expression. OS was calculated with the median follow-up duration of 91.0 months (range: 3.0-116.0 months).

RESULTS

Integrin α7 was highly expressed in tumor tissue compared to paired adjacent tissue (P < .001), and tumor integrin α7 high expression was correlated with higher pathological grade (P = .004), increased T stage (P = .017), and advanced TNM stage (P = .033). Kaplan-Meier curve showed that patients with integrin α7 high expression (mean OS = 69.8, 95%CI: 60.5-79.1 months) presented with worse OS compared to patients with integrin α7 low expression (mean OS = 101.8, 95%CI: 96.0-107.7 months; P < .001). Multivariate Cox's regression analysis further disclosed that tumor integrin α7 high expression independently predicted poor OS (P < .001).

CONCLUSION

Integrin α7 is upregulated and correlates with higher pathological grade, increased T stage, and advanced TNM stage, meanwhile it also acts as a valuable prognostic factor for worse survival in ccRCC patients.

Ubiquitin-specific protease 22 promotes the proliferation, migration and invasion of glioma cells

Ubiquitin-specific protease 22 (USP22), as one of the 11 death-from-cancer signature genes, presented high expression in a variety of tumors. Previous studies showed that USP22 played a significant role in cell-cycle, oncogenesis, clinicopathology and survival. Our studies have presented USP22 was over-expressed in glioma tissue and the patients with high expression of USP22 had a poor survival than that with low expression of USP22. However, the concrete effect of USP22 on biological behavior in glioma cells has been rarely reported. The study aimed to clear the effect of USP22 on cell proliferation, migration and invasion in glioma. Using siRNA, USP22 was knocked down in U251 and U87 glioma cells and successful transfection effect was validated. Cell proliferation, migration and invasion were observed by the methods of EdU, Wound healing and Transwell assay, separately. At the same time, the expression of MMP2 was detected by Gelatin zymography after transfecting siRNAs. After the knockdown of USP22 by siRNA, the abilities of glioma cell proliferation, migration and invasion were decreased, accompanying, the expression of MMP2 was also decreased. We drew a conclusion that USP22 could increase the abilities of proliferation, migration and invasion of glioma cells, and promote the growth and development of glioma.

BMI1 Deficiency Results in Female Infertility by Activating p16/p19 Signaling and Increasing Oxidative Stress

The polycomb repressor B lymphoma Mo-MLV insertion region 1 (BMI1) is a core composition of polycomb repressive complex 1 (PRC1) and contributes to diverse fundamental cellular processes including cell senescence, apoptosis and proliferation. To investigate the role and mechanism of BMI1 in maintaining normal female reproductive function, we compared the differences in reproductive phenotypes between Bmi1-deficient and wild-type female mice. The Bmi1-deficient female mice were then supplemented with N-acetylcysteine in their drinking water to explore whether antioxidant supplementation could improve reproductive dysfunction caused by BMI1 deficiency. The results revealed that Bmi1 deletion resulted in complete infertility in female mice, estrous cycle disorder, and follicular developmental disorders. The reactive oxygen species levels in the ovarian tissue were increased; the ability of antioxidant enzymes was downregulated; the expression levels of p19 and p53 proteins were significantly upregulated. We also found that oocytes derived from Bmi1-deficient mice could not develop into embryos by in vitro fertilization and in vitro culture of embryos. Furthermore, supplementation with the antioxidant NAC not only improved the reproductive defects caused by Bmi1 deletion, but also largely rescued the ability of Bmi1-deficient oocytes to develop into embryos in vitro. These results indicated that cells lacking Bmi1 resulted in female infertility by activating the p16/p19 signaling pathway, increasing oxidative stress and DNA damage, inhibiting granulosa cell proliferation, and inducing granulosa cell apoptosis. Thus, BMI1 may be a novel potential target for the clinical treatment of female infertility.

Effect of Bmi-1-mediated NF-κB signaling pathway on the stem-like properties of CD133+ human liver cancer cells

OBJECTIVE

To investigate the impact of Bmi-1-mediated NF-κB pathway on the biological characteristics of CD133+ liver cancer stem cells (LCSCs).

METHODS

Flow cytometry was used to isolate CD133+ LCSC cells from Huh7, Hep3B, SK-hep1, and PLC/PRF-5 cells. CD133+ Huh7 cells were divided into Control, Blank, Bmi-1 siRNA, JSH-23 (NF-κB pathway inhibitor), and Bmi-1 + JSH-23 groups. The properties of CD133+ Huh7 cells were detected by the colony-formation and sphere-forming assays. Besides, Transwell assay was applied for the measurement of cell invasion and migration, immunofluorescence staining for the detection of NF-κB p65 nuclear translocation, and qRT-PCR and Western blotting for the determination of SOX2, NANOG, OCT4, Bmi-1, and NF-κB p65 expression.

RESULTS

CD133+ Huh-7 cells were chosen as the experiment subjects after flow cytometry. Compared with CD133- Huh-7 cells, the expression of CD133, OCT4, SOX2, NANOG, Bmi-1, and NF-κB p65, the nuclear translocation of NF-κB p65, the number of cell colonies and Sphere formation, as well as the abilities of invasion and migration were observed to be increased in CD133+ Huh-7 cells, which was inhibited after treated with Bmi-1 siRNA or JSH-23, meanwhile, the cell cycle was arrested at the G0/G1 and S phases with apparently enhanced cell apoptosis. Importantly, no significant differences in the biological characteristics of CD133 + Huh-7 cells were found between the Blank group and Bmi-1 + JSH-23 group.

CONCLUSION

Down-regulating Bmi-1 may inhibit the biological properties of CD133+ LCSC by blocking NF-κB signaling pathway, which lays a scientific foundation for the clinical treatment of liver cancer.

Role of BMI1 in epithelial ovarian cancer: investigated via the CRISPR/Cas9 system and RNA sequencing

Background

B-cell-specific Moloney murine leukemia virus integration site 1 (BMI1) might be an appropriate biomarker in the management of epithelial ovarian cancer (EOC). However, the biological role of BMI1 and its relevant molecular mechanism needs further elaboration. Clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 system is an excellent genome-editing tool and is scarcely used in EOC studies.

Methods

We first applied CRISPR/Cas9 technique to silence BMI1 in EOC cells; thereafter we accomplished various in vivo and in vitro experiments to detect biological behaviors of ovarian cancer cells, including MTT, flow cytometry, Transwell, real-time polymerase chain reaction and western blotting assays, etc.; eventually, we used RNA sequencing to reveal the underlying molecular traits driven by BMI1 in EOC.

Results

We successfully shut off the expression of BMI1 in EOC cells using CRISPR/Cas9 system, providing an ideal cellular model for investigations of target gene. Silencing BMI1 could reduce cell growth and metastasis, promote cell apoptosis, and enhance the platinum sensitivity of EOC cells. BMI1 might alter extracellular matrix structure and angiogenesis of tumor cells through regulating Focal adhesion and PI3K/AKT pathways.

Conclusion

BMI1 is a potential biomarker in EOC management, especially for tumor progression and chemo-resistance. Molecular traits, including BMI1 and core genes in Focal adhesion and PI3K/AKT pathways, might be alternatives as therapeutic targets for EOC.

Electronic supplementary material

The online version of this article (10.1186/s13048-018-0406-z) contains supplementary material, which is available to authorized users.

Decreased expression of ALDH5A1 predicts prognosis in patients with ovarian cancer

Aldehyde dehydrogenase 5 family, member A1 (ALDH5A1) belongs to the superfamily of aldehyde dehydrogenases (ALDHs). However, the prognostic value of ALDH5A1 in ovarian cancer remains unclear. The aim of this study was to explore the relationship between ALDH5A1 and the prognosis of patients with ovarian cancer (OC). We compared the expression of ALDH5A1 in OC to that innormal controls, using GSE40595 profiling data. Tissue microarray analysis was conducted for192 OC patients, 14 adjacent normal ovary tissues, and 2 normal ovary tissues. Using the "Kaplan-Meier plotter" (KM plotter) database, updated gene expression data and survival information of a total of 1583 OC patients were used to evaluate the prognostic value of ALDH5A1 in OC patients. We found that ALDH5A1 mRNA expression was downregulated in OC patients compared with that innormal tissues. In survival analyses, we found that ALDH5A1 was positively linked to prognosis in patients with OC, particularly in those with serous ovarian cancer (SOC). In addition, high Ctranscription activity of ALDH5A1 was correlated with better overall survival in SOC patients expressing mutatedTP53, but not in those expressing wild-type TP53. In pathological grades II/III, a high mRNA level of ALDH5A1 was associated with improved overall survival. The positive association between ALDH5A1 and prognosis was found not only in early stages(I and II), but also in advanced stages (III and IV) of SOC patients. results indicate that ALDH5A1 is an excellent predictive factor of OC and may play crucial roles in OC progression.

BMI1, a new target of CK2α

BACKGROUND

The polycomb group protein, BMI1 plays important roles in chromatin modification, stem cell function, DNA damage repair and mitochondrial bioenergetics. Such diverse cellular functions of BMI1 could be, in part, due to post-translational modifications, especially phosphorylation. To date, AKT has been reported as a kinase that by site specific phosphorylation of BMI1 modulates its oncogenic functions.

METHODS

Immunoprecipitation in conjunction with kinase assay and mass spectrometry was used to determine association with and site specific phosphorylation of BMI1 by CK2α. Functional implications of the BMI1/CK2α axis was examined in cancer cells utilizing siRNA and exogenous gene expression followed by biochemical and phenotypic studies. Correlations between expression of CK2α and BMI1 were determined from cell lines and formalin fixed paraffin embedded tissues representing the normal fallopian tube epithelium and high grade serous ovarian cancer samples.

RESULTS

Here we report that CK2α, a nuclear serine threonine kinase, phosphorylates BMI1 at Serine 110 as determined by in-vitro/ex-vivo kinase assay and mass spectrometry. In ovarian cancer cell lines, expression of CK2α correlated with the phospho-species, as well as basal BMI1 levels. Preventing phosphorylation of BMI1 at Serine 110 significantly decreased half-life and stability of the protein. Additionally, re-expression of the phosphorylatable but not non-phosphorylatable BMI1 rescued clonal growth in endogenous BMI1 silenced cancer cells leading us to speculate that CK2α-mediated phosphorylation stabilizes BMI1 and promotes its oncogenic function. Clinically, compared to normal fallopian tube epithelial tissues, the expression of both BMI1 and CK2α were significantly higher in tumor tissues obtained from high-grade serous ovarian cancer patients. Among tumor samples, the expression of BMI1 and CK2α positively correlated (Spearman coefficient = 0.62, P = 0.0021) with each other.

CONCLUSION

Taken together, our findings establish an important regulatory role of CK2α on BMI1 phosphorylation and stability and implicate the CK2α/BMI1 axis in ovarian cancer.

Mitochondrial BMI1 maintains bioenergetic homeostasis in cells

The polycomb complex proto-oncogene BMI1 [B lymphoma Mo-MLV insertion region 1 homolog (mouse)] is essential for self-renewal of normal and cancer stem cells. BMI1-null mice show severe defects in growth, development, and survival. Although BMI1 is known to exert its effect in the nucleus via repression of 2 potent cell-cycle regulators that are encoded by the Ink4a/Arf locus, deletion of this locus only partially rescues BMI1-null phenotypes, which is indicative of alternate mechanisms of action of BMI1. Here, we show that an extranuclear pool of BMI1 localizes to inner mitochondrial membrane and directly regulates mitochondrial RNA (mtRNA) homeostasis and bioenergetics. These mitochondrial functions of BMI1 are independent of its previously described nuclear functions because a nuclear localization-defective mutant BMI1 rescued several bioenergetic defects that we observed in BMI1-depleted cells, for example, mitochondrial respiration, cytochrome c oxidase activity, and ATP production. Mechanistically, BMI1 coprecipitated with polynucleotide phosphorylase, a ribonuclease that is responsible for decay of mtRNA transcripts. Loss of BMI1 enhanced ribonuclease activity of polynucleotide phosphorylase and reduced mtRNA stability. These findings not only establish a novel extranuclear role of BMI1 in the regulation of mitochondrial bioenergetics, but also provide new mechanistic insights into the role of this proto-oncogene in stem cell differentiation, neuronal aging, and cancer.-Banerjee Mustafi, S., Aznar, N., Dwivedi, S. K. D., Chakraborty, P. K., Basak, R., Mukherjee, P., Ghosh, P., Bhattacharya, R. Mitochondrial BMI1 maintains bioenergetic homeostasis in cells.

B-cell-specific Moloney murine leukemia virus integration site 1: potential stratification factor and therapeutic target for epithelial ovarian cancer

Epithelial ovarian cancer, a vexing challenge for clinical management, still lacks biomarkers for early diagnosis, precise stratification, and prognostic evaluation of patients. B-cell-specific Moloney murine leukemia virus integration site 1 (BMI1), a member of the polycomb group of proteins, engages in diverse cellular processes, including proliferation, differentiation, senescence, and stem cell renewal. In addition, BMI1, as a cancer stem-cell marker, participates in tumorigenesis through various pathways. Rewardingly, recent studies have also revealed a relationship between BMI1 expression and the clinical grade/stage, therapy response, and survival outcome in a majority of human malignancies, including epithelial ovarian cancer. Therefore, BMI1 might serve as a potential stratification factor and treatment target for epithelial ovarian cancer, pending evidence from further investigations.

TWIST1 and BMI1 in Cancer Metastasis and Chemoresistance

Purpose Increasing evidences revealed that cancer cells with the characteristics of epithelial-mesenchymal transition (EMT) or cancer stem cells (CSC) have high ability of progression, invasion, metastasis and chemoresistance. TWIST1 and BMI1 are crucial transcription factors required for EMT and CSC. Both TWIST1 and BMI1 are up-regulated in various cancers and have a positive correlation with poor prognosis. Although recent results showed that the two molecules function in promoting cancer metastasis and chemoresistance respectively, the correlation of TWIST1 and BMI1 is not well understood. Methods In this review, we summarize recent advance in cancer research focus on TWIST1 and BMI1 in cancer metastasis and chemoresistance, and emphasize the possible link between EMT and CSC. Results Further investigation of TWIST1 and BMI1 cooperately promote CSC proliferation due to EMT-associated effect will help to understand the mechanism of tumor cells metastasis and chemoresistance. Conclusions TWIST1 and BMI1 in cancer cells will be effective targets for treating chemoresistant metastatic lesions.

Polycomb Repressor Complex 1 Member, BMI1 Contributes to Urothelial Tumorigenesis through p16-Independent Mechanisms

Urothelial carcinoma (UC) causes significant morbidity and remains the most expensive cancer to treat because of the need for repeated resections and lifelong monitoring for patients with non-muscle-invasive bladder cancer (NMIBC). Novel therapeutics and stratification approaches are needed to improve the outlook for both NMIBC and muscle-invasive bladder cancer. We investigated the expression and effects of B Lymphoma Mo-MLV Insertion Region 1 (BMI1) in UC. BMI1 was found to be overexpressed in most UC cell lines and primary tumors by quantitative real-time polymerase chain reaction and immunohistochemistry. In contrast to some previous reports, no association with tumor stage or grade was observed in two independent tumor panels. Furthermore, upregulation of BMI1 was detected in premalignant bladder lesions, suggesting a role early in tumorigenesis. BMI1 is not located within a common region of genomic amplification in UC. The CDKN2A locus (which encodes the p16 tumor suppressor gene) is a transcriptional target of BMI1 in some cellular contexts. In UC cell lines and primary tissues, no correlation between BMI1 and p16 expression was observed. Retroviral-mediated overexpression of BMI1 immortalized normal human urothelial cells (NHUC) in vitro and was associated with induction of telomerase activity, bypass of senescence, and repression of differentiation. The effects of BMI1 on gene expression were identified by expression microarray analysis of NHUC-BMI1. Metacore analysis of the gene expression profile implicated downstream effects of BMI1 on α4/β1 integrin-mediated adhesion, cytoskeleton remodeling, and CREB1-mediated transcription.

The role of the polycomb repressive complex pathway in T and NK cell lymphoma: biological and prognostic implications

Polycomb repressive complex 2 (PRC2; formed by EZH2, SUZ12, and EED protein subunits) and PRC1 (BMI1 protein) induce gene silencing through histone modification, primarily H3K27me3, and deregulation of PRC pathways leads to tumorigenesis. In the present study, activation of PRC2, H3K27me3, and BMI1 was investigated by immunohistochemistry in 175 cases of T and natural killer (NK) cell lymphoma. Activation of PRC proteins was analyzed according to c-MYC activation, Epstein-Barr virus (EBV) infection, CD30 activation, and survival. Among all T and NK cell lymphomas, high expression rates of 54.7 % for EZH2, 33.3 % for SUZ12, 85.7 % for EED, 40.5 % for H3K27me3, and 30.9 % for BMI1 were discovered. Activation of PRC2, H3K27me3, and BMI1 showed positive correlations (P < 0.05). Activation of c-MYC was associated with activation of SUZ12 and triple coactivation of all PRC2 protein subunits (EZH2(high)/SUZ12(high)/EED(high)) (P < 0.05). In EBV-positive tumors, activation of EZH2 and H3K27me3 showed greater association (P < 0.05). H3K27me3 and BMI1 showed a negative association in tumors expressing CD30 (P < 0.05). With respect to survival, BMI1 activation was independently associated with poor prognosis in T and NK cell lymphomas (P = 0.002). In conclusion, T and NK cell lymphomas were associated with activation of PRC pathway markers, for which c-MYC activation and EBV infection could be suggested as possible causes. PRC pathway markers may be potential therapeutic targets and prognostic markers in T and NK cell lymphoma.

High Expressions of Lgr5 and ALDH1 in Primary Epithelial Ovarian Cancer Correlate with Advanced Tumor Stage and Grade as well as Poor Prognosis of the Patients

BACKGROUND

The aim of our study was to investigate the clinical role of aldehyde dehydrogenase 1 (ALDH1) and leucine-rich repeat-containing G-protein-coupled receptor 5 (Lgr5) expressions in epithelial ovarian cancer (EOC) and their prognostic significance.

METHODS

One hundred primary EOC samples were obtained for immunohistochemical analysis of ALDH1 and Lgr5 expressions. Correlation analysis was performed between ALDH1 or Lgr5 and clinical factors.

RESULTS

High expression of ALDH1 and Lgr5 was identified in 71 and 55 cases of EOC tissues, respectively. The ALDH1 and Lgr5 expressions in EOC tissues were significantly higher as compared to the normal ovaries and benign ovarian tumors. High expression of ALDH1 and Lgr5 was strongly correlated with advanced International Federation of Gynecology and Obstetrics (FIGO) stages, higher tumor grades, and poor overall survival of the patients.

CONCLUSIONS

Lgr5 and ALDH1 were highly expressed in EOC tissues, and correlated with different FIGO operation-pathological stages and tumor grades, clinical outcome, and with each other. The combined use of ALDH1 and Lgr5 might be useful for the diagnosis and prognosis prediction of EOC patients. © 2015 S. Karger AG, Basel.

Downregulated miR-495 [Corrected] Inhibits the G1-S Phase Transition by Targeting Bmi-1 in Breast Cancer

Bmi-1 (B cell-specific Moloney murine leukemia virus integration site 1) is upregulated in breast cancer and was involved in many malignant progressions of breast cells, including cell proliferation, stem cell pluripotency, and cancer initiation. However, the epigenetic regulatory mechanism of Bmi-1 in breast cancer remains unclear. After analysis of the ArrayExpress dataset GSE45666, we comparatively detected the expression levels of miR-495 in 9 examined breast cancer cell lines, normal breast epithelial cells and 8 pairs of fresh clinical tumor samples. Furthermore, to evaluate the effect of miR-495 on the progression of breast cancer, MCF-7 and MDA-MB-231 were transduced to stably overexpress miR-495. The 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide assay, colony formation assays, 5-Bromo-2-deoxyUridine labeling and immunofluorescence, anchorage-independent growth ability assay, flow cytometry analysis, and luciferase assays were used to test the effect of miR-495 in MCF-7 and MDA-MB-231 cells in vitro. Xenografted tumor model was also used to evaluate the effect of miR-495 in breast cancer. Herein, we found that miR-495, a predicted regulator of Bmi-1, was frequently downregulated in malignant cells and tissues of breast. Upregulation of miR-495 significantly suppressed breast cancer cell proliferation and tumorigenicity via G1-S arrest. Further analysis revealed that miR-495 targeted Bmi-1 through its 3' untranslated region. Moreover, Bmi-1 could neutralize the suppressive effect of miR-495 on cell proliferation and tumorigenicity of breast cancer in vivo. These data suggested that miR-495 could inhibit the G1-S phase transition that leads to proliferation and tumorigenicity inhibition by targeting and suppressing Bmi-1 in breast cancer.

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

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

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

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

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