The polycomb group proteins, BMI-1 and EZH2, are tumour-associated antigens

NEAT1 promotes the progression of prostate cancer by targeting the miR-582-5p/EZH2 regulatory axis

In several forms of malignant tumors, nuclear enriched abundant transcript 1 (NEAT1), a lncRNA, has been identified to play an important role. NEAT1's regulation patterns in prostate cancer (PCa) are, however, mainly unknown. This study was aimed to evaluate and study the roles and regulatory mechanisms of NEAT1 in PCa. NEAT1, miR-582-5p, and enhancer of zeste homolog 2 (EZH2) expression were detected by qRT-PCR. The PCa cells' invasive, migrative, and proliferative activities in vitro were assessed using transwell migration and invasion, wound-healing, cloning creation, and CCK-8 assays. In the present study, impaired proliferative, migrative, and invasive capacities were observed in the NEAT1-deficient PCa (PC3 and LNCaP) cells. Further mechanistic studies found that NEAT1 performs its function through sponging miR-582-5p. Furthermore, EZH2 was confirmed to be the downstream target gene of miRNA-582-5p. The impaired progression caused by NEAT1 deficiency in PCa cells was significantly restored by the inhibition of miR-582-5p, while these effects were largely abolished by the deletion of EZH2. Finally, the xenograft nude mouse model showed that knocking down the expression of NEAT1 suppressed the growth of PCa. In conclusion, NEAT1 promotes the progression of PCa by controlling the miR-582-5p and miR-582-5p-mediated EZH2.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10616-023-00612-z.

Polycomb repressor complex: Its function in human cancer and therapeutic target strategy

The Polycomb Repressor Complex (PRC) plays a pivotal role in gene regulation during development and disease, with dysregulation contributing significantly to various human cancers. The intricate interplay between PRC and cellular signaling pathways sheds light on cancer complexity. PRC presents promising therapeutic opportunities, with inhibitors undergoing rigorous evaluation in preclinical and clinical studies. In this review, we emphasize the critical role of PRC complex in gene regulation, particularly PcG proteins mediated chromatin compaction through phase separation. We also highlight the pathological implications of PRC complex dysregulation in various tumors, elucidating underlying mechanisms driving cancer progression. The burgeoning field of therapeutic strategies targeting PRC complexes, notably EZH2 inhibitors, has advanced significantly. However, we explore the need for combination therapies to enhance PRC targeted treatments efficacy, providing a glimpse into the future of cancer therapeutics.

Dual role of microRNA-1297 in the suppression and progression of human malignancies

MicroRNAs (miRNAs) are endogenous, non-coding, single-stranded and tiny RNAs that modulate several biological functions, more importantly, the pathophysiology of numerous human cancers. They are bound with target mRNAs and thereby regulate gene expression at post-transcriptional levels. MiRNAs can either trigger cancer progression as an oncogene or alleviate it as a tumor suppressor. Abnormal expression of microRNA-1297 (miR-1297) has been noticed in several human cancers suggesting a distinct role for the miRNA in tumorigenesis. More specifically, it is both up-regulated and down-regulated in various cancers suggesting that it can act as both tumor suppressor and oncogene. This review systematically highlights the different roles of miR-1297 in the pathophysiology of human cancers, explains the mechanisms underlying miR-1297-mediated tumorigenesis, and discusses its potential prognostic, diagnostic, and therapeutic importance.

The Role of Polycomb Group Protein BMI1 in DNA Repair and Genomic Stability

The polycomb group (PcG) proteins are a class of transcriptional repressors that mediate gene silencing through histone post-translational modifications. They are involved in the maintenance of stem cell self-renewal and proliferation, processes that are often dysregulated in cancer. Apart from their canonical functions in epigenetic gene silencing, several studies have uncovered a function for PcG proteins in DNA damage signaling and repair. In particular, members of the poly-comb group complexes (PRC) 1 and 2 have been shown to recruit to sites of DNA damage and mediate DNA double-strand break repair. Here, we review current understanding of the PRCs and their roles in cancer development. We then focus on the PRC1 member BMI1, discussing the current state of knowledge of its role in DNA repair and genome integrity, and outline how it can be targeted pharmacologically.

EZH2 Expression in Intestinal Neuroendocrine Tumors

Neuroendocrine tumors (NETs) arise from the cells present throughout the diffuse endocrine system. These neoplasms were previously regarded as rare, but in fact are increasing in incidence (3.65/100 000 individuals/y). Enhancer of zeste homolog 2 (EZH2) plays a crucial role in cell cycle regulation, and it was reported to be overexpressed in several tumors. The aim of the study was to investigate EZH2 expression, also related with proliferation rate, and p53 expression in NETs of the intestine encompassing a group of tumors primary to the stomach, appendix, small intestine, and colon. The specimens from 33 patients with neuroendrocrine tumors were investigated by immunohistochemistry for EZH2, p53, and Ki-67. Only 10 of 33 (30.3%) cases showed high EZH2 expression. High EZH2 levels significantly associated with elevated proliferation rates (P=0.0012) and with elevated percentage of positive cells for p53 (P=0.011). Our results suggest an association between p53 and the EZH2 pathway in NETs. EZH2 could represent a potential target antigen in cancer immunotherapy.

JMJD1A promotes tumorigenesis and forms a feedback loop with EZH2/let-7c in NSCLC cells

Lung cancer is the most common cause of cancer-related deaths worldwide, and non-small cell lung cancer (NSCLC) accounts for 80 to 85 % of all lung cancer. Although the standard treatment regimen has been established, long-term survival for NSCLC patients is still generally poor. The histone demethylase Jumonji domain containing 1A (JMJD1A) has been proposed as an oncogene in several types of human cancer, but its clinical significance and functional roles in NSCLC remain largely unclear. In the present study, JMJD1A was frequently upregulated in NSCLC compared with para-carcinoma tissues. JMJD1A knockdown significantly inhibited NSCLC cell growth, migration, and invasion in vitro and tumorigenesis in vivo. Further experiments demonstrated that JMJD1A knockdown could decrease the expression of EZH2, which has been shown to play a crucial role in the carcinogenesis of NSCLC and, in turn, increase the expression of anti-tumor microRNA let-7c. Also, let-7c directly targeted the 3'-untranslated regions of JMJD1A and EZH2. Taken together, JMJD1A could promote NSCLC tumorigenesis. JMJD1A/EZH2/let-7c constituted a feedback loop and might represent a promising therapeutic target for NSCLC.

MicroRNA-1297 regulates hepatocellular carcinoma cell proliferation and apoptosis by targeting EZH2

In this study, we suggested the level of miR-1297 was downreguled in the human hepatocellular carcinoma compared to the normal cells. We demonstrate ectopic expression of miR-1297 could significantly suppress hepatocellular carcinoma cells proliferation and enhance the cell apoptosis. In vitro reporter assay suggested EZH2 is a direct target gene of miR-1297. Furthermore, knockdown of EZH2 have the same effect with miR-1297 overeexpression in hepatocellular carcinoma cells. These findings provide evidence that miR-1297 plays a key role in inhibition of the hepatocellular carcinoma cells proliferation, and enhancing cell apoptosis through targeting EZH2, and strongly suggest that ex ogenous miR-1297 may have therapeutic value in treating hepatocellular carcinoma.

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.

Inhibition of EZH2 reverses chemotherapeutic drug TMZ chemosensitivity in glioblastoma

Glioblastoma remains among the most devastating cancers with a median survival of less than 15 months and virtually no survival beyond five years. Currently, the treatment of glioma includes surgery, radiation therapy, chemotherapy, and comprehensive treatment. Intrinsic or acquired resistance to TMZ, is one of the greatest obstacles in successful GB treatment, and is thought to be influenced by a variety of mechanisms. The EZH2 gene, which is expressed in various solid tumors, can regulate gene transcription and promote the generation and progression of tumors. Our aim was to investigate the relationship between EZH2 and multidrug-resistance of human glioblastoma cells. In this study, we established TMZ-resistant U251 and U87 clones (U251/TMZ and U87/TMZ cells), which expressed high level of EZH2. Using RNA interference, we demonstrated that the downregulation of Ezh2 expression in U251/TMZ and U87/TMZ cells resulted in apoptosis and a cell cycle arrest in the G1/S phase. Furthermore, the reduced expression of Ezh2 altered the MDR, MRP and BCRP mRNA and protein levels. These findings suggest that EZH2 plays an important part in the development of multidrug resistance and may represent a novel therapeutic target for multidrug-resistant glioblastoma.

Ring1B promotes hepatic stem/progenitor cell expansion through simultaneous suppression of Cdkn1a and Cdkn2a in mice

Polycomb-group (PcG) proteins play crucial roles in self-renewal of stem cells by suppressing a host of genes through histone modifications. Identification of the downstream genes of PcG proteins is essential for elucidation of the molecular mechanisms of stem cell self-renewal. However, little is known about the PcG target genes in tissue stem cells. We found that the PcG protein, Ring1B, which regulates expression of various genes through monoubiquitination of histone H2AK119, is essential for expansion of hepatic stem/progenitor cells. In mouse embryos with a conditional knockout of Ring1B, we found that the lack of Ring1B inhibited proliferation and differentiation of hepatic stem/progenitor cells and thereby inhibited hepatic organogenesis. These events were characterized by derepression of cyclin-dependent kinase inhibitors (CDKIs) Cdkn1a and Cdkn2a, known negative regulators of cell proliferation. We conducted clonal culture experiments with hepatic stem/progenitor cells to investigate the individual genetic functions of Ring1B, Cdkn1a, and Cdkn2a. The data showed that the cell-cycle inhibition caused by Ring1B depletion was reversed when Cdkn1a and Cdkn2a were suppressed simultaneously, but not when they were suppressed individually.

CONCLUSION

Our results show that expansion of hepatic stem/progenitor cells requires Ring1B-mediated epigenetic silencing of Cdkn1a and Cdkn2a, demonstrating that Ring1B simultaneously regulates multiple CDKIs in tissue stem/progenitor cells.

A potential antitumor ellagitannin, davidiin, inhibited hepatocellular tumor growth by targeting EZH2

Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide and is the third most common cause of cancer-related deaths. Currently available treatment options for HCC patients are scarce resulting in an urgent need to develop a novel effective cure. Polygonum capitatum is a medicinal herb which has been used to treat inflammatory diseases in Miao nationality of China. We recently isolated a pure compound davidiin from P. capitatum extract. Four HCC cell lines were treated with davidiin. Cell viability was recorded by MTT assay. siRNAs targeting enhancer of zeste homolog 2 (EZH2) were applied to modulate the expression of EZH2. Established xenograft mice models of HCC were applied to evaluate the in vivo anticancer activity of davidiin. We investigated the anticancer activity and the underlying mechanism of davidiin. The compound inhibited HCC cell growth and also suppressed tumor growth in xenografted HCC mouse. Such inhibition was facilitated by specifically downregulation on EZH2. The compound possesses anticancer activity both in vitro and in vivo which warrants further clinical investigation as a potential anti-HCC agent.

RNAi-mediated EZH2 depletion decreases MDR1 expression and sensitizes multidrug-resistant hepatocellular carcinoma cells to chemotherapy

The histone-lysine N-methyltransferase, enhancer of zeste homologue 2 (EZH2), functions as a transcriptional repressor and plays an important role in the development of various types of cancer. In this study, we observed the increased EZH2 expression in the Bel/FU multidrug-resistant hepatocellular carcinoma (HCC) cell line. The RNA interference (RNAi)-mediated depletion of EZH2 expression in the Bel/FU cells led to decreased multidrug resistance protein 1 (MDR1) expression, which resulted in increased apoptosis and sustained G1/S phase arrest. Moreover, siRNA targeting EZH2 sensitized Bel/FU cells to 5-fluorouracil treatment. These findings suggest that EZH2 plays a role in the development of multidrug resistance and may represent a novel therapeutic target for multidrug-resistant HCC.

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.

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.

Epigenetic factors in cancer development: polycomb group proteins

The role of chromatin-modifying factors in cancer biology emerged exponentially in the last 10 years, and increased attention has been focused on Polycomb group (PcG) proteins and their enzymatic activities. PcG proteins are repressive chromatin modifiers required for proliferation and development. The frequent deregulation of PcG activities in human tumors has direct oncogenic effects and results, essential for cancer cell proliferation. Here we will review the recent findings regarding PcG proteins in prospective tumor development, focusing on the molecular mechanisms that deregulate PcG expression in different tumors, at the downstream pathways to PcG expression (that contribute to cancer development) and at the mechanisms that regulate PcG recruitment to specific targets. Finally, we will speculate on the benefit of PcG inhibition for cancer treatment, reviewing potential pharmacological strategies.

p53-paralog DNp73 oncogene is repressed by IFNα/STAT2 through the recruitment of the Ezh2 polycomb group transcriptional repressor

The DNp73 proteins act as trans-repressors of p53 and p73-dependent transcription and exert both anti-apoptotic activity and pro-proliferative activity. DNp73s are frequently up-regulated in a variety of human cancers, including human hepatocellular carcinomas (HCCs). Increased levels of DNp73 proteins confer to HCC cells resistance to apoptosis and, irrespective to p53 status, a chemoresistant phenotype. Here, we show that interferon (IFN)α down-regulates DNp73 expression in primary human hepatocytes (PHHs) and HCC cell lines. IFNα has been used as pro-apoptotic agent in the treatment of malignancies and there is increasing evidence of IFNα effectiveness in HCC treatment and prevention of recurrence. The precise mechanisms by which class I IFNs exert their anti-proliferative and anti-tumor activity remain unclear. IFNα binding to its receptor activates multiple intracellular signaling cascades regulating the transcription of numerous direct target genes through the recruitment of a complex comprising of STAT1, STAT2 and IFN regulatory factor (IRF)9 to their promoters. We found that, in response to IFNα, the P2p73 promoter undergoes substantial chromatin remodeling. Histone deacetylases (HDACs) replace histone acetyl transferases. STAT2 is recruited onto the endogenous P2p73 promoter together with the polycomb group protein Ezh2, leading to increased H3K27 methylation and transcriptional repression. The reduction of DNp73 levels by IFNα is paralleled by an increased susceptibility to IFNα-triggered apoptosis of Huh7 hepatoma cells. Our results show, for the first time, that IFN-stimulated gene factor 3 recruitment may serve both in activating and repressing gene expression and identify the down-regulation of DNp73 as an additional mechanism to counteract the chemoresistance of liver cancer cells.

Specific recognition and inhibition of Ewing tumour growth by antigen-specific allo-restricted cytotoxic T cells

Background:

The development of a successful immunotherapy is hampered by an ineffective T-cell repertoire against tumour antigens and the inability of the patient's immune system to overcome tolerance-inducing mechanisms. Here, we test the specific recognition and lytical potential of allo-restricted CD8⁺ T cells against Ewing tumour (ET) associated antigens Enhancer of Zeste, Drosophila Homolog 2 (EZH2), and Chondromodulin-I (CHM1) identified through previous microarray analysis.

Methods:

Following repetitive CHM1³¹⁹ (VIMPCSWWV) and EZH2⁶⁶⁶ (YMCSFLFNL) peptide-driven stimulations with HLA-A^*0201⁺ dendritic cells (DC), allo-restricted HLA-A^*0201⁻ CD8⁺ T cells were stained with HLA-A^*0201/peptide multimers, sorted and expanded by limiting dilution.

Results:

Expanded T cells specifically recognised peptide-pulsed target cells or antigen-transfected cells in the context of HLA-A^*0201 and killed HLA-A^*0201⁺ ET lines expressing the antigen while HLA-A^*0201^– ET lines were not affected. Furthermore, adoptively transferred T cells caused significant ET growth delay in Rag2^−/−γ_C^−/− mice. Within this context, we identified the CHM1³¹⁹ peptide as a new candidate target antigen for ET immunotherapy.

Conclusion:

These results clearly identify the ET-derived antigens, EZH2⁶⁶⁶ and CHM1³¹⁹, as suitable targets for protective allo-restricted human CD8⁺ T-cell responses against non-immunogenic ET and may benefit new therapeutic strategies in ET patients treated with allogeneic stem cell transplantation.

Improved outcome following allogeneic stem cell transplantation in chronic myeloid leukemia is associated with higher expression of BMI-1 and immune responses to BMI-1 protein

BMI-1 and EZH2 are polycomb group (PcG) proteins which maintain self-renewal of stem cells, and are overexpressed in leukemia. To investigate the potential of PcG proteins as leukemia-associated antigens, and targets for graft-versus-leukemia (GVL) effects, we studied cells from 86 chronic myeloid leukemia (CML) patients and 25 HLA-A*0201⁺ sibling donors collected prior to allogeneic stem cell transplantation (SCT). Although BMI-1 overexpression in CD34⁺ cells of CML patients treated with pharmacotherapy is associated with poor prognosis, we found, conversely, that in CML patients treated with SCT, a higher expression of BMI-1, and correspondingly lower expression of its target for repression, CDKN2A, is associated with improved leukemia-free survival. Cytotoxic T lymphocyte (CTL) responses to BMI-1 peptide were detected in 5 of 25 (20%) donors, and 8 of 19 (42%) HLA-A*0201⁺ CML patients. BMI-1 generated more total and high avidity immune responses, and was more immunogenic than EZH2. PcG-specific CTLs had memory phenotype, were readily expanded in short-term cultures, and were detected post-SCT in recipients of PcG-specific CTL-positive donors. A higher BMI-1 expression in CML CD34⁺ progenitors was associated with native BMI-1 immune responses. These immune responses to PcG proteins may target leukemia stem cells and have relevance for disease control by GVL.

Immune response against tumor antigens expressed on human cancer stem-like cells/tumor-initiating cells

Cancer stem-like cells (CSCs)/tumor-initiating cells (TICs) are a small population of cancer cells that have the properties of tumor-initiating ability, self-renewal and differentiation. These properties suggest that CSCs/TICs are essential for tumor maintenance, recurrence and distant metastasis. Thus, elimination of CSCs/TICs is essential to cure malignant diseases. However, there are several studies reporting that CSCs/TICs are more resistant to standard cancer therapies, including chemotherapy and radiotherapy, than non-CSC/TIC populations. How then, can we eliminate CSCs/TICs? Immunotherapy might be the possible answer. In recent analysis, innate immunity (natural killer cells and gammadeltaT cells) and also adaptive immunity (cytotoxic T lymphocyte-based cellular immunity and antibody-based humoral immunity) can recognize CSCs/TICs in vitro efficiently. Furthermore, CSC/TIC-specific monoclonal antibody therapies are also efficient in vivo. In this article, we describe the potency, possibilities and problems of CSC/TIC-targeting immunotherapy.

Histone lysine methylation and demethylation pathways in cancer

The genetic changes leading to the development of human cancer are accompanied by alterations in the structure and modification status of chromatin, which represent powerful regulatory mechanisms for gene expression and genome stability. These epigenetic alterations have sparked interest into deciphering the regulatory pathways and function of post-translational modifications of histones during the initiation and progression of cancer. In this review we describe and summarize the current knowledge of several histone lysine methyltransferase and demethylase pathways relevant to cancer. Mechanistic insight into histone modifications will pave the way for the development and therapeutic application of "epidrugs" in cancer.

RNAi targeting EZH2 inhibits tumor growth and liver metastasis of pancreatic cancer in vivo

The function of EZH2 in tumorigenesis and liver metastasis of pancreatic cancer has never been elucidated in vivo. EZH2 was overexpressed in pancreatic carcinomas and its overexpression was associated with tumor differentiation and pT status. Suppression of EZH2 caused a significant growth inhibition of pancreatic cancer cells in vitro and markedly diminished their tumorigenicity in vivo. Knock-down of EZH2 inhibited liver metastasis of pancreatic cancer in vivo. EZH2 has a crucial role in tumor growth and liver metastasis of pancreatic cancer.

Polycomb group protein gene silencing, non-coding RNA, stem cells, and cancer

Epigenetic programming is an important facet of biology, controlling gene expression patterns and the choice between developmental pathways. The Polycomb group proteins (PcGs) silence gene expression, allowing cells to both acquire and maintain identity. PcG silencing is important for stemness, X chromosome inactivation (XCI), genomic imprinting, and the abnormally silenced genes in cancers. Stem and cancer cells commonly share gene expression patterns, regulatory mechanisms, and signalling pathways. Many microRNA species have oncogenic or tumor suppressor activity, and disruptions in these networks are common in cancer; however, long non-coding (nc)RNA species are also important. Many of these directly guide PcG deposition and gene silencing at the HOX locus, during XCI, and in examples of genomic imprinting. Since inappropriate HOX expression and loss of genomic imprinting are hallmarks of cancer, disruption of long ncRNA-mediated PcG silencing likely has a role in oncogenesis. Aberrant silencing of coding and non-coding loci is critical for both the genesis and progression of cancers. In addition, PcGs are commonly abnormally overexpressed years prior to cancer pathology, making early PcG targeted therapy an option to reverse tumor formation, someday replacing the blunt instrument of eradication in the cancer therapy arsenal.

Adoptive T-cell immunotherapy of chronic lymphocytic leukaemia

Immunotherapy for B-cell chronic lymphocytic leukaemia (B-CLL) and other haematological malignancies may consist of passive antibody, active immunization or adoptive T-cell transfer. This chapter will focus on T-lymphocyte immunotherapy; an approach supported by earlier observations that the beneficial effects of allogeneic stem cell transplantation depend, in part, on the graft-versus-leukaemia effects mediated by these cells. One promising strategy consists of the genetic manipulation of effector T lymphocytes to express tumour-specific T-cell receptors or chimeric antigen receptors directed against surface antigens on the B-CLL cells. This methodology is now being integrated with the concept that tumour recurrence may be due to the persistence of a reservoir of more primitive and chemoresistant tumour cells, dubbed 'cancer stem cells', with self-renewal capacity. Identification and characterization of these cancer stem cells in B-CLL is crucial for the development of new anti-tumour agents, and for the identification of target antigens for cellular immunotherapy. This chapter will describe how immunotherapy may be directed to a more primitive side population of B-CLL cells.

Association between BMI-1 expression, acute graft-versus-host disease, and outcome following allogeneic stem cell transplantation from HLA-identical siblings in chronic myeloid leukemia

Expression of CD7, ELA-2, PR-3, and the polycomb group gene BMI-1 reflects the intrinsic heterogeneity and predicts prognosis of patients with chronic myeloid leukemia (CML) who were not treated with allogeneic stem cell transplantation (allo-SCT). This study investigated whether expression of these genes determined outcome following allo-SCT in a cohort of 84 patients with chronic-phase (CP) CML. We found that patients expressing BMI-1 at a “high” level before allo-SCT had an improved overall survival (P = .005) related to a reduced transplantation-related mortality. In multivariate analysis, when adjusted for the European Group for Blood and Marrow Transplantation (EBMT)–Gratwohl score and other prog-nostic factors, there was an independent association between BMI-1 expression and grades 2 to 4 acute graft-versus-host disease (relative risk [RR] = 2.85; 95% confidence interval [CI], 1.3-6.4; P = .011), suggesting that BMI-1 measured prior to allo-SCT can serve as a biomarker for predicting outcome in patients with CP-CML receiving allo-SCT, and may thus contribute to better therapeutic decisions.

Low BMI-1 expression is associated with an activated BMI-1-driven signature, vascular invasion, and hormone receptor loss in endometrial carcinoma

We studied the expression of polycomb group (PcG) protein BMI-1 in a large population-based patient series of endometrial carcinomas in relation to clinical and molecular phenotype. Also, 57 fresh frozen endometrial carcinomas were studied for the relationship between BMI-1 protein expression, BMI-1 mRNA level, and activation of an 11-gene signature reported to represent a BMI-1-driven pathway. BMI-1 protein expression was significantly weaker in tumours with vascular invasion (P<0.0001), deep myometrial infiltration (P=0.004), and loss of oestrogen receptor (ER) (P<0.0001) and progesterone receptors (PR) (P=0.03). Low BMI-1 protein expression was highly associated with low BMI-1 mRNA expression (P=0.002), and similarly low BMI-1 mRNA expression correlated significantly with vascular invasion, ER and PR loss, and histologic grade 3. In contrast, activation of the reported 11-gene signature, supposed to represent a BMI-1-driven pathway, correlated with low mRNA expression of BMI-1 (P<0.001), hormone receptor loss, presence of vascular invasion, and poor prognosis. We conclude that BMI-1 protein and mRNA expression are significantly correlated and that BMI-1 expression is inversely associated with activation of the 11-gene signature. Loss of BMI-1 seems to be associated with an aggressive phenotype in endometrial carcinomas.

Loss of BMI-1 expression is associated with clinical progress of malignant melanoma

BMI-1 is a member of the Polycomb group of genes (PcGs) and is involved in embryonic gene regulation and maintenance of adult stem cells. It has been suggested that BMI-1 protein is important in cell cycle regulation, since both p16/INK4a and p14/ARF are downstream BMI-1 targets. BMI-1 has been implicated in the development and progression of several malignancies, but its role in melanocytic tumors of the skin is unknown. In the present study, using immunohistochemistry on 178 benign and malignant melanocytic lesions and two different antibodies, BMI-1 expression was reduced in melanomas compared with benign nevi. In established melanomas, loss of BMI-1 expression was associated with features of aggressive tumors, such as increased tumor cell proliferation, presence of necrosis and increased expression of both N-cadherin and beta3-integrin, indicating a more invasive and mesenchymal phenotype. Low BMI-1 expression was associated with low p14 and CDK4 but not with p16 expression. Low levels of BMI-1 expression were also significantly associated with decreased patient survival.

Bmi-1 expression predicts prognosis for patients with gastric carcinoma

BACKGROUND AND OBJECTIVE

The Bmi-1 gene is a transcriptional repressor involved in oncogenesis in various human cancers. Here, we examine Bmi-1 expression in gastric carcinoma (GC) and investigates whether its expression correlates with patient prognosis.

METHODS

Immunohistochemistry was performed using an anti-Bmi-1 antibody on primary tumor samples of 146 cases of GC. The association between Bmi-1 expression and the clinicopathological status and prognosis of GC patients was statistically analyzed. Furthermore, reverse transcription-PCR (RT-PCR) and Western blotting were performed to determine the expression levels of Bmi-1 in an additional 8 GC and the adjacent non-cancerous samples.

RESULTS

Using immunohistochemistry, we found that 99 of 146 paraffin-embedded GC samples expressed Bmi-1 extensively. Statistical analysis showed that Bmi-1 overexpression was highly correlated with tumor size, clinical stage, lymph node metastasis and T classification (P < 0.05), Patients with Bmi-1 expression had shorter overall survival time than those without Bmi-1 expression (P < 0.01). Multivariate analysis indicated that Bmi-1 expression is an independent prognostic factor of GC. RT-PCR and Western blotting showed that Bmi-1 was up-regulated at both the transcriptional and translational levels in the GC tissues compared with the adjacent non-cancerous tissues.

CONCLUSIONS

Bmi-1 may serve as a valuable marker for diagnosis and prognosis of GC.

Epigenetic regulation of normal and malignant hematopoiesis

The molecular processes governing hematopoiesis involve the interplay between lineage-specific transcription factors and a series of epigenetic tags, including DNA methylation and covalent histone tail modifications, such as acetylation, methylation, phosphorylation, SUMOylation and ubiquitylation. These post-translational modifications, which collectively constitute the 'histone code', are capable of affecting chromatin structure and gene transcription and are catalysed by opposing families of enzymes, allowing the developmental potential of hematopoietic stem cells to be dynamically regulated. The essential role of these enzymes in regulating normal blood development is highlighted by the finding that members from all families of chromatin regulators are targets for dysregulation in many hematological malignancies, and that patterns of histone modification are globally affected in cancer as well as the regulatory regions of specific oncogenes and tumor suppressors. The discovery that these epigenetic marks can be reversed by compounds targeting aberrant transcription factor/co-activator/co-repressor interactions and histone-modifying activities, provides the basis for an exciting field in which the epigenome of cancer cells may be manipulated with potential therapeutic benefits.

Proteomic analysis of EZH2 downstream target proteins in hepatocellular carcinoma

Enhancer of zeste homolog 2 (EZH2) is suggested to be a potential therapeutic target and a diagnostic marker for cancer. Our previous study also showed the critical role of EZH2 in hepatocellular carcinoma (HCC) tumorigenesis. The present study is aimed at revealing the comprehensive downstream pathways of EZH2 by functional proteomic profiling. Lentivirus mediated RNA interference (RNAi) was employed to knockdown EZH2 in HCC cells. The 2-DE was employed to compare the expression profile difference between parental and EZH2-knockdown HCC cells. In total, 28 spots were differentially expressed during EZH2 inhibition. Among all, 18 proteins were identified by PMF with MALDI-TOF MS. Western blotting further validated upregulation of 60S acidic ribosomal protein P0 (L10E), and downregulation of two proteins with EZH2 inhibition: stathmin1 and probable protein disulfide isomerase (PDI) ER-60 precursor (ERp57). Moreover, L10E was downregulated with overexpression of EZH2 in hepatocytes, and L10E reversed the effect of EZH2 on cell proliferation, suggesting it a downstream target of EZH2. The comprehensive and comparative analyses of proteins associated with EZH2 could further our understanding on the downstream signal cascade of EZH2 leading to tumorigenesis.

Increased polycomb-group oncogene Bmi-1 expression correlates with poor prognosis in hepatocellular carcinoma

PURPOSE

Recent studies have identified polycomb-group gene Bmi-1 as oncogene in the generation of mouse pre-cell lymphomas, and overexpression of Bmi-1 has been found in several human tumor with the disease progress and poor prognosis of the cancer patients.

METHODS

In present study, we investigated Bmi-1 expression and its prognostic significance in hepatocellular carcinoma (HCC) by performing immunohistochemical analysis, using a total of 137 HCC clinical tissue samples.

RESULTS

High Bmi-1 expression (Bmi-1 2+ or 3+) was shown in 29.9% cases. The positive immuno-staining of Bmi-1 was not only in well/moderately-differentiated tumor cells, but also in surrounding noncancerous or cirrhotic liver tissue. Bmi-1 expression level did not correlate with any clinicopathological parameters. However, survival analysis showed that the high-Bmi-1 group had a significantly shorter overall survival time than the low-Bmi-1 group (P=0.047). Multivariate analysis after 24 months revealed that Bmi-1 expression was a significant and independent prognostic parameter (P=0.002) for HCC patients.

CONCLUSIONS

Our study indicated that Bmi-1 could be a candidate biomarker for long-term survival in HCC.

Results of donor lymphocyte infusions for relapsed myelodysplastic syndrome after hematopoietic cell transplantation

Allogeneic hematopoietic cell transplantation (HCT) represents a potentially curative approach for patients with myelodysplastic syndromes (MDSs). While a large proportion of HCT recipients become long-term disease-free survivors, recurrence of MDS remains the leading cause of mortality after HCT. The role of donor lymphocyte infusion (DLI) in patients with relapsed MDS after HCT is unclear. We report results among 16 patients treated with DLI for relapsed MDS after HCT at a single institution between March 1993 and February 2004. The cohort contained 10 men and 6 women with a median age of 49 (range, 22-67) years. CR with resolution of cytopenias and prior disease markers occurred in 3 of 14 patients who could be evaluated. Two patients survived without MDS for 68 and 65 months after DLI, respectively, but died with pneumonia. Grades II-IV acute GVHD and chronic GVHD occurred after DLI in 6 (43%) and 5 (36%) patients, respectively. All three responders developed grades III-IV acute GVHD and extensive chronic GVHD after DLI. Our results confirm prior reports that DLI can result in CR in some patients with recurrent MDS after transplant, but long-term survival is infrequent.