BMI1, stem cell factor acting as novel serum-biomarker for Caucasian and African-American prostate cancer

Myosin 1C isoform A is a novel candidate diagnostic marker for prostate cancer

Early diagnosis of prostate cancer is a challenging issue due to the lack of specific markers. Therefore, a sensitive diagnostic marker that is expressed or upregulated exclusively in prostate cancer cells would facilitate diagnostic procedures and ensure a better outcome. We evaluated the expression of myosin 1C isoform A in 5 prostate cell lines, 41 prostate cancer cases, and 11 benign hyperplasias. We analyzed the expression of 12 surface molecules on prostate cancer cells by flow cytometry and analyzed whether high or low myosin 1C isoform A expression could be attributed to a distinct phenotype of prostate cancer cells. Median myosin 1C isoform A expression in prostate cancer samples and cancer cell lines was 2 orders of magnitude higher than in benign prostate hyperplasia. Based on isoform A expression, we could also distinguish clinical stage 2 from clinical stage 3. Among cell lines, PC-3 cells with the highest myosin 1C isoform A level had diminished numbers of CD10/CD13-positive cells and increased numbers of CD29 (integrin β1), CD38, CD54 (ICAM1) positive cells. The surface phenotype of clinical samples was similar to prostate cancer cell lines with high isoform A expression and could be described as CD10-/CD13- with heterogeneous expression of other markers. Both for cell lines and cancer specimens we observed the strong correlation of high myosin 1C isoform A mRNA expression and elevated levels of CD29 and CD54, suggesting a more adhesive phenotype for cells with high isoform A expression. Compared to normal tissue, prostate cancer samples had also reduced numbers of CD24- and CD38-positive cells. Our data suggest that a high level of myosin 1C isoform A is a specific marker both for prostate cancer cells and prostate cancer cell lines. High expression of isoform A is associated with less activated (CD24/CD38 low) and more adhesive (CD29/CD54 high) surface phenotype compared to benign prostate tissue.

Restoration of BMI1 levels after the administration of early harvest extra virgin olive oil as a therapeutic strategy against Alzheimer's disease

Even though Alzheimer's disease (AD) is the most common cause of dementia, the mechanisms governing the establishment and progression of the disease remain largely unknown. Here, we investigated the implication of the neuroprotective protein BMI1 (B lymphoma Mo-MLV insertion region 1 homolog) in AD and the possibility to reverse the onset of the disease through the administration of extra virgin olive oil (EVOO) in Mild Cognitive Impairment (MCI) patients. For this purpose, we utilized a wide bank of MCI patient samples to examine the potential effects of EVOO. We found that while EVOO treatment increases BMI1 levels, p53 levels drop in MCI patient serum after EVOO treatment for 12 months. Additionally, AD-related biomarkers (p-tau, Aβ1-42 and Aβ1-42/Aβ-40 ratio) return to normal levels after administration of EVOO in MCI patients for 12 months. Moreover, we show that upon EVOO administration, BMI1-upregulation correlates with reduction of oxidative stress and inflammatory responses. In conclusion, we provide clinical trial evidence to confirm that restoration of BMI1 activity through EVOO administration in MCI patients constitutes a potential therapeutic approach against neurodegeneration leading to AD.

Senescence Induced by BMI1 Inhibition Is a Therapeutic Vulnerability in H3K27M-Mutant DIPG

Diffuse intrinsic pontine glioma (DIPG) is an incurable brain tumor of childhood characterized by histone mutations at lysine 27, which results in epigenomic dysregulation. There has been a failure to develop effective treatment for this tumor. Using a combined RNAi and chemical screen targeting epigenomic regulators, we identify the polycomb repressive complex 1 (PRC1) component BMI1 as a critical factor for DIPG tumor maintenance in vivo. BMI1 chromatin occupancy is enriched at genes associated with differentiation and tumor suppressors in DIPG cells. Inhibition of BMI1 decreases cell self-renewal and attenuates tumor growth due to induction of senescence. Prolonged BMI1 inhibition induces a senescence-associated secretory phenotype, which promotes tumor recurrence. Clearance of senescent cells using BH3 protein mimetics co-operates with BMI1 inhibition to enhance tumor cell killing in vivo.

Anti-S100A4 Antibody Therapy Is Efficient in Treating Aggressive Prostate Cancer and Reversing Immunosuppression: Serum and Biopsy S100A4 as a Clinical Predictor

S100A4 oncoprotein plays a critical role during prostate cancer progression and induces immunosuppression in host tissues. We hypothesized that S100A4-regulated oncogenic activity in immunosuppressed prostate tumors promotes growth of neoplastic cells, which are likely to become aggressive. In the current study, we investigated whether biopsy-S100A4 gene alteration independently predicts the outcome of disease in patients and circulatory-S100A4 is druggable target for treating immunosuppressive prostate cancer. Aided by DECIPHER-genomic test, we show biopsy-S100A4 overexpression as predictive of (i) poor ADT response and (ii) high risk of mortality in 228 radical prostatectomy-treated patients. Furthermore, analysis of tumor genome data of more than 1,000 patients with prostate cancer (PRAD/SU2C/FHCRC studies) validated the association of S100A4-alteration to poor survival and metastasis. We show that increased serum-S100A4 levels are associated to the prostate cancer progression in patients. The prerequisite for metastasis is the escape of tumor cells via vascular system. We show that extracellular-S100A4 protein as a growth factor induces vascular transmigration of prostate cancer cells and bone demineralization thus forms an ideal target for therapies for treating prostate cancer. By employing surface plasmon resonance and isothermal titration calorimetry, we show that mab6B12 antibody interacts with and neutralizes S100A4 protein. When tested for therapeutic efficacy, the mab6B12 therapy reduced the (i) osteoblastic demineralization of bone-derived MSCs, (ii) S100A4-target (NFκB/MMP9/VEGF) levels in prostate cancer cells, and (iii) tumor growth in a TRAMPC2 syngeneic mouse model. The immuno-profile analysis showed that mAb6B12-therapy (i) shifted Th1/Th2 balance (increased Stat4⁺/T-bet⁺ and decreased GATA2⁺/CD68⁺/CD45⁺/CD206⁺ cells); (ii) modulated cytokine levels in CD4⁺ T cells; and (iii) decreased levels of IL5/6/12/13, sTNFR1, and serum-RANTES. We suggest that S100A4-antibody therapy has clinical applicability in treating immunosuppressive prostate cancer in patients.

B lymphoma Moloney murine leukemia virus insertion region 1: An oncogenic mediator in prostate cancer

B lymphoma Moloney murine leukemia virus insertion region 1 (BMI1), a core member of polycomb repressive complex 1 (PRC1), has been intensely investigated in the field of cancer epigenetics for decades. Widely known as a critical regulator in cellular physiology, BMI1 is essential in self-renewal and differentiation in different lineages of stem cells. BMI1 also plays a significant role in cancer etiology for its involvement in pathological progress such as epithelial–mesenchymal transition (EMT) and cancer stem cell maintenance, propagation, and differentiation. Importantly, overexpression of BMI1 is predictive for drug resistance, tumor recurrence, and eventual therapy failure of various cancer subtypes, which renders the pharmacological targeting at BMI1 as a novel and promising therapeutic approach. The study on prostate cancer, a prevalent hormone-related cancer among men, has promoted enormous research advancements in cancer genetics and epigenetics. This review summarizes the role of BMI1 as an oncogenic and epigenetic regulator in tumor initiation, progression, and relapse of prostate cancer.

CUL4B regulates cancer stem-like traits of prostate cancer cells by targeting BMI1 via miR200b/c

BACKGROUND

Cancer stem-like traits contribute to prostate cancer (PCa) progression and metastasis. Cullin 4B (CUL4B) is a member of the ubiquitin E3 ligase family and overexpressed in several solid malignancies including PCa. CUL4B has been suggested to be an oncogene through epigenetic repression of tumor suppressors. However, the link between CUL4B expression and cancer stem-like phenotype remains unclear.

METHODS

Western blot analysis, sphere formation, and colony formation assays were used to examine the effect of CUL4B on cancer stem-like traits in PCa cells. Mechanically, bioinformatic analysis was utilized to evaluate whether BMI1 was a target of CUL4B. Moreover, real-time polymerase chain reaction, chromatin immunoprecipitation, and luciferase reporter assays were performed to identify microRNAs regulated by CUL4B. Finally, Western blot assay was used to validate the regulation of CUL4B, miR200b, and miR200c (miR200b/c) on the stem-like characteristics of PCa cells.

RESULTS

CUL4B promotes PCa pluripotency-associated markers expression, sphere formation, and anchorage-independent growth ability in vitro. Mechanically, CUL4B upregulates BMI1 expression via epigenetically repressing miR200b/c expression. In addition, miR200b/c could partially reverse CUL4B-induced BMI1 and pluripotency-associated marker expression.

CONCLUSIONS

Our study revealed that CUL4B regulates cancer stem-like traits of prostate cancer cells by targeting BMI1 via miR200b/c, which might give novel insight into how CUL4B promotes PCa progression through regulating cancer stem-like traits.

Prognostic and Clinic-Pathological Significances of SCF and COX-2 Expression in Inflammatory and Malignant Prostatic Lesions

The initiation of prostatic malignancy has been linked to chronic inflammation. Stem cell factor (SCF) is an inflammatory cytokine that is specific to the c-KIT receptor which is type III receptor tyrosine kinase (RTK). Cyclooxygenases (COXs) are the main enzymes which are responsible for prostaglandins production from arachidonic acid. COX2 is an enzyme which is produced under different pathological conditions. The aim of our study; is to investigate the clinicopathological and the prognostic significance of SCF and COX-2 expression in prostatic adenocarcinoma (PC), chronic prostatitis and nodular prostatic hyperplasia (NPH) in a trial to clarify the role of inflammation as a risk factor for prostatic carcinogenesis and cancer progression. SCF and COX-2 tissue protein expression were evaluated in 50 cases of PC, 20 cases of chronic prostatitis and 10 cases of NPH using immunohistochemistry, patients were followed up for 5 years. The relationship between their levels of expressions, clinicopathological, and prognostic criteria were studied. SCF expression in PC was positively correlated with advanced patient age (p = <0.001), high level of PSA (p = 0.010), higher Gleason score (p = 0.011). COX-2 expression in PC was positively correlated with advanced patient age (p = <0.001), high level of PSA (p = 0.016), advanced D'Amico risk group (p = 0.038). High levels of expression of both SCF& COX-2 are associated with higher incidence of tumor relapse, worse disease overall survival and free survival (p < 0.001). SCF and COX-2 are associated with PC progression and associated with poor prognosis in PC patients.

BMI1 Drives Metastasis of Prostate Cancer in Caucasian and African-American Men and Is A Potential Therapeutic Target: Hypothesis Tested in Race-specific Models

PURPOSE

Metastasis is the major cause of mortality in prostate cancer patients. Factors such as genetic makeup and race play critical role in the outcome of therapies. This study was conducted to investigate the relevance of BMI1 in metastatic prostate cancer disease in Caucasian and African-Americans.

EXPERIMENTAL DESIGN

We employed race-specific prostate cancer models, clinical specimens, clinical data mining, gene-microarray, transcription-reporter assay, chromatin-immunoprecipitation (ChIP), IHC, transgenic-(tgfl/fl) zebrafish, and mouse metastasis models.

RESULTS

BMI1 expression was observed to be elevated in metastatic tumors (lymph nodes, lungs, bones, liver) of Caucasian and African-American prostate cancer patients. The comparative analysis of stage III/IV tumors showed an increased BMI1 expression in African-Americans than Caucasians. TCGA and NIH/GEO clinical data corroborated to our findings. We show that BMI1 expression (i) positively correlates to metastatic (MYC, VEGF, cyclin D1) and (ii) negative correlates to tumor suppressor (INKF4A/p16, PTEN) levels in tumors. The correlation was prominent in African-American tumors. We show that BMI1 regulates the transcriptional activation of MYC, VEGF, INKF4A/p16, and PTEN. We show the effect of pharmacological inhibition of BMI1 on the metastatic genome and invasiveness of tumor cells. Next, we show the anti-metastatic efficacy of BMI1-inhibitor in transgenic zebrafish and mouse metastasis models. Docetaxel as monotherapy has poor outcome on the growth of metastatic tumors. BMI1 inhibitor as an adjuvant improved the taxane therapy in race-based in vitro and in vivo models.

CONCLUSIONS

BMI1, a major driver of metastasis, represents a promising therapeutic target for treating advanced prostate cancer in patients (including those belonging to high-risk group).

Proteomic characterization of paired non-malignant and malignant African-American prostate epithelial cell lines distinguishes them by structural proteins

Background

While many factors may contribute to the higher prostate cancer incidence and mortality experienced by African-American men compared to their counterparts, the contribution of tumor biology is underexplored due to inadequate availability of African-American patient-derived cell lines and specimens. Here, we characterize the proteomes of non-malignant RC-77 N/E and malignant RC-77 T/E prostate epithelial cell lines previously established from prostate specimens from the same African-American patient with early stage primary prostate cancer.

Methods

In this comparative proteomic analysis of RC-77 N/E and RC-77 T/E cells, differentially expressed proteins were identified and analyzed for overrepresentation of PANTHER protein classes, Gene Ontology annotations, and pathways. The enrichment of gene sets and pathway significance were assessed using Gene Set Enrichment Analysis and Signaling Pathway Impact Analysis, respectively. The gene and protein expression data of age- and stage-matched prostate cancer specimens from The Cancer Genome Atlas were analyzed.

Results

Structural and cytoskeletal proteins were differentially expressed and statistically overrepresented between RC-77 N/E and RC-77 T/E cells. Beta-catenin, alpha-actinin-1, and filamin-A were upregulated in the tumorigenic RC-77 T/E cells, while integrin beta-1, integrin alpha-6, caveolin-1, laminin subunit gamma-2, and CD44 antigen were downregulated. The increased protein level of beta-catenin and the reduction of caveolin-1 protein level in the tumorigenic RC-77 T/E cells mirrored the upregulation of beta-catenin mRNA and downregulation of caveolin-1 mRNA in African-American prostate cancer specimens compared to non-malignant controls. After subtracting race-specific non-malignant RNA expression, beta-catenin and caveolin-1 mRNA expression levels were higher in African-American prostate cancer specimens than in Caucasian-American specimens. The “ECM-Receptor Interaction” and “Cell Adhesion Molecules”, and the “Tight Junction” and “Adherens Junction” pathways contained proteins are associated with RC-77 N/E and RC-77 T/E cells, respectively.

Conclusions

Our results suggest RC-77 T/E and RC-77 N/E cell lines can be distinguished by differentially expressed structural and cytoskeletal proteins, which appeared in several pathways across multiple analyses. Our results indicate that the expression of beta-catenin and caveolin-1 may be prostate cancer- and race-specific. Although the RC-77 cell model may not be representative of all African-American prostate cancer due to tumor heterogeneity, it is a unique resource for studying prostate cancer initiation and progression.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-017-3462-7) contains supplementary material, which is available to authorized users.

Immunoseroproteomic Profiling in African American Men with Prostate Cancer: Evidence for an Autoantibody Response to Glycolysis and Plasminogen-Associated Proteins

African American (AA) men suffer from a disproportionately high incidence and mortality of prostate cancer (PCa) compared with other racial/ethnic groups. Despite these disparities, African American men are underrepresented in clinical trials and in studies on PCa biology and biomarker discovery. We used immunoseroproteomics to profile antitumor autoantibody responses in AA and European American (EA) men with PCa, and explored differences in these responses. This minimally invasive approach detects autoantibodies to tumor-associated antigens that could serve as clinical biomarkers and immunotherapeutic agents. Sera from AA and EA men with PCa were probed by immunoblotting against PC3 cell proteins, with AA sera showing stronger immunoreactivity. Mass spectrometry analysis of immunoreactive protein spots revealed that several AA sera contained autoantibodies to a number of proteins associated with both the glycolysis and plasminogen pathways, particularly to alpha-enolase (ENO1). The proteomic data is deposited in ProteomeXchange with identifier PXD003968. Analysis of sera from 340 racially diverse men by enzyme-linked immunosorbent assays (ELISA) showed higher frequency of anti-ENO1 autoantibodies in PCa sera compared with control sera. We observed differences between AA-PCa and EA-PCa patients in their immunoreactivity against ENO1. Although EA-PCa sera reacted with higher frequency against purified ENO1 in ELISA and recognized by immunoblotting the endogenous cellular ENO1 across a panel of prostate cell lines, AA-PCa sera reacted weakly against this protein by ELISA but recognized it by immunoblotting preferentially in metastatic cell lines. These race-related differences in immunoreactivity to ENO1 could not be accounted by differential autoantibody recognition of phosphoepitopes within this antigen. Proteomic analysis revealed differences in the posttranslational modification profiles of ENO1 variants differentially recognized by AA-PCa and EA-PCa sera. These intriguing results suggest the possibility of race-related differences in the antitumor autoantibody response in PCa, and have implications for defining novel biological determinants of PCa health disparities.

In vitro models of cancer stem cells and clinical applications

Cancer cells, stem cells and cancer stem cells have for a long time played a significant role in the biomedical sciences. Though cancer therapy is more effective than it was a few years ago, the truth is that still none of the current non-surgical treatments can cure cancer effectively. The reason could be due to the subpopulation called “cancer stem cells” (CSCs), being defined as those cells within a tumour that have properties of stem cells: self-renewal and the ability for differentiation into multiple cell types that occur in tumours.

The phenomenon of CSCs is based on their resistance to many of the current cancer therapies, which results in tumour relapse. Although further investigation regarding CSCs is still needed, there is already evidence that these cells may play an important role in the prognosis of cancer, progression and therapeutic strategy. Therefore, long-term patient survival may depend on the elimination of CSCs. Consequently, isolation of pure CSC populations or reprogramming of cancer cells into CSCs, from cancer cell lines or primary tumours, would be a useful tool to gain an in-depth knowledge about heterogeneity and plasticity of CSC phenotypes and therefore carcinogenesis. Herein, we will discuss current CSC models, methods used to characterize CSCs, candidate markers, characteristic signalling pathways and clinical applications of CSCs. Some examples of CSC-specific treatments that are currently in early clinical phases will also be presented in this review.

Role of epithelial mesenchymal transition in prostate tumorigenesis

Globally, the cancer associated deaths are generally attributed to the spread of cancerous cells or their features to the nearby or distant secondary organs by a process known as metastasis. Among other factors, the metastatic dissemination of cancer cells is attributed to the reactivation of an evolutionary conserved developmental program known as epithelial to mesenchymal transition (EMT). During EMT, fully differentiated epithelial cells undergo a series of dramatic changes in their morphology, along with loss of cell to cell contact and matrix remodeling into less differentiated and invasive mesenchymal cells. Many studies provide evidence for the existence of EMT like states in prostate cancer (PCa) and suggest its possible involvement in PCa progression and metastasis. At the same time, the lack of conclusive evidence regarding the presence of full EMT in human PCa samples has somewhat dampened the interest in the field. However, ongoing EMT research provides new perspectives and unveils the enormous potential of this field in tailoring new therapeutic regimens for PCa management. This review summarizes the role of many transcription factors and other molecules that drive EMT during prostate tumorigenesis.

IDH1R¹³²H decreases the proliferation of U87 glioma cells through upregulation of microRNA-128a

Mutations in isocitrate dehydrogenase 1 (IDH1) are found in >70% of secondary glioblastomas and lower-grade gliomas (grades II–III). Among the numerous phenotypic differences between IDH1 mutant and wild-type glioma patients, the most salient is an improved survival rate for patients with a mutation. MicroRNAs (miRNAs) are a class of small, non-coding, single-stranded RNAs that can negatively regulate gene expression at the post-transcriptional level, predominantly by binding to the 3′-untranslated region of their target mRNAs. The dysregulated expression of several miRNAs has been reported to modulate glioma progression; however, it is unclear whether mutations in IDH1 regulate glioma cell proliferation through miRNA dysregulation. In the present study, stable overexpression of IDH1^WT or IDH1^R132H was established in the U87 glioma cell line. It was found that IDH1^R132H decreased cell proliferation of U87 glioma cells by inducing the expression of the miRNA miR-128a. This process was dependent on the transcription factor hypoxia inducible factor-1α (HIF-1α), which binds to a hypoxia response element in the promoter of miR-128a. Furthermore, miR-128a negatively regulated the expression of B-cell-specific Moloney murine leukemia virus integration site 1 protein (Bmi-1), which is involved in suppressing cell proliferation. These findings suggest that the IDH1^R132H-HIF-1α-miR-128a-Bmi-1 pathway is involved in glioma cell proliferation.

ROBO1, a tumor suppressor and critical molecular barrier for localized tumor cells to acquire invasive phenotype: study in African-American and Caucasian prostate cancer models

High-risk populations exhibit early transformation of localized prostate cancer (CaP) disease to metastasis which results in the mortality of such patients. The paucity of knowledge about the molecular mechanism involved in acquiring of metastatic behavior by primary tumor cells and non-availability of reliable phenotype-discriminating biomarkers are stumbling blocks in the management of CaP disease. Here, we determine the role and translational relevance of ROBO1 (an organogenesis-associated gene) in human CaP. Employing CaP-progression models and prostatic tissues of Caucasian and African-American patients, we show that ROBO1 expression is localized to cell-membrane and significantly lost in primary and metastatic tumors. While Caucasians exhibited similar ROBO1 levels in primary and metastatic phenotype, a significant difference was observed between tumor phenotypes in African-Americans. Epigenetic assays identified promoter methylation of ROBO1 specific to African-American metastatic CaP cells. Using African-American CaP models for further studies, we show that ROBO1 negatively regulates motility and invasiveness of primary CaP cells, and its loss causes these cells to acquire invasive trait. To understand the underlying mechanism, we employed ROBO1-expressing/ROBO1-C2C3-mutant constructs, immunoprecipitation, confocal-microscopy and luciferase-reporter techniques. We show that ROBO1 through its interaction with DOCK1 (at SH3-SH2-domain) controls the Rac-activation. However, loss of ROBO1 results in Rac1-activation which in turn causes E-Cadherin/β-catenin cytoskeleton destabilization and induction of cell migration. We suggest that ROBO1 is a predictive biomarker that has potential to discriminate among CaP types, and could be exploited as a molecular target to inhibit the progression of disease as well as treat metastasis in high-risk populations such as African-Americans.

Prognostic value of polycomb proteins EZH2, BMI1 and SUZ12 and histone modification H3K27me3 in colorectal cancer

Numerous changes in epigenetic mechanisms have been described in various types of tumors. In search for new biomarkers, we investigated the expression of Polycomb-group (PcG) proteins EZH2, BMI1 and SUZ12 and associated histone modification H3K27me3 in colorectal cancer. Nuclear expression of PcG proteins and histone modification H3K27me3 were immunohistochemically (IHC) stained on a tissue microarray (TMA), including 247 tumor tissues and 47 normal tissues, and scored using the semi-automated Ariol system. Tumor tissues showed higher expression of EZH2 (p = 0.05) and H3K27me3 (p<0.001) as compared to their normal counterparts. Combined marker trend analyses indicated that an increase in the number of markers showing high expression was associated with better prognosis. High expression of all four markers in the combined marker analyses was correlated with the best patient survival and the longest recurrence-free survival, with overall survival (p = 0.01, HR 0.42(0.21-0.84)), disease-free survival (p = 0.007, HR 0.23(0.08-0.67) and local recurrence-free survival (p = 0.02, HR 0.30(0.11-0.84)). In conclusion, we found that expression of PcG proteins and H3K27me3 showed prognostic value in our study cohort. Better stratification of patients was obtained by combining the expression data of the investigated biomarkers as compared to the individual markers, underlining the importance of investigating multiple markers simultaneously.

miRNA-128 suppresses prostate cancer by inhibiting BMI-1 to inhibit tumor-initiating cells

microRNA-128 (miR128) is reduced in prostate cancer relative to normal/benign prostate tissues, but causal roles are obscure. Here we show that exogenously introduced miR128 suppresses tumor regeneration in multiple prostate cancer xenograft models. Cancer stem-like cell (CSC)-associated properties were blocked, including holoclone and sphere formation as well as clonogenic survival. Using a miR128 sensor to distinguish cells on the basis of miR128 expression, we found that miR128-lo cells possessed higher clonal, clonogenic, and tumorigenic activities than miR128-hi cells. miR128 targets the stem cell regulatory factors BMI-1, NANOG, and TGFBR1, the expression of which we found to vary inversely with miR128 expression in prostate cancer stem/progenitor cell populations. In particular, we defined BMI-1 as a direct and functionally relevant target of miR128 in prostate cancer cells, where these genes were reciprocally expressed and exhibited opposing biological functions. Our results define a tumor suppressor function for miR128 in prostate cancer by limiting CSC properties mediated by BMI-1 and other central stem cell regulators, with potential implications for prostate cancer gene therapy.

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.

The S100A4 Oncoprotein Promotes Prostate Tumorigenesis in a Transgenic Mouse Model: Regulating NFκB through the RAGE Receptor

S100A4, a calcium-binding protein, is known for its role in the metastatic spread of tumor cells, a late event of cancer disease. This is the first report showing that S100A4 is not merely a metastatic protein but also an oncoprotein that plays a critical role in the development of tumors. We earlier showed that S100A4 expression progressively increases in prostatic tissues with the advancement of prostate cancer (CaP) in TRAMP, an autochthonous mouse model. To study the functional significance of S100A4 in CaP, we generated a heterozygously deleted S100A4 (TRAMP/S100A4(+/-)) genotype by crossing TRAMP with S100A4(-/-) mice. TRAMP/S100A4(+/-) did not show a lethal phenotype, and transgenes were functional. As compared to age-matched TRAMP littermates, TRAMP/S100A4(+/-) mice exhibited 1) an increased tumor latency period (P < 0.001), 2) a 0% incidence of metastasis, and 3) reduced prostatic weights (P < 0.001). We generated S100A4-positive clones from S100A4-negative CaP cells and tested their potential. S100A4-positive tumors grew at a faster rate than S100A4-negative tumors in vitro and in a xenograft mouse model. The S100A4 protein exhibited growth factor-like properties in multimode (intracellular and extracellular) forms. We observed that 1) the growth-promoting effect of S100A4 is due to its activation of NFκB, 2) S100A4-deficient tumors exhibit reduced NFκB activity, 3) S100A4 regulates NFκB through the RAGE receptor, and 4) S100A4 and RAGE co-localize in prostatic tissues of mice. Keeping in view its growth-promoting role, we suggest that S100A4 qualifies as an excellent candidate to be exploited for therapeutic agents to treat CaP in humans.

BMI1 polycomb group protein acts as a master switch for growth and death of tumor cells: regulates TCF4-transcriptional factor-induced BCL2 signaling

For advanced prostate cancer (CaP), the progression of tumors to the state of chemoresistance and paucity of knowledge about the mechanism of chemoresistance are major stumbling blocks in the management of this disease. Here, we provide compelling evidence that BMI1 polycomb group protein and a stem cell factor plays a crucial role in determining the fate of tumors vis-à-vis chemotherapy. We show that progressive increase in the levels of BMI1 occurs during the progression of CaP disease in humans. We show that BMI1-rich tumor cells are non-responsive to chemotherapy whereas BMI1-silenced tumor cells are responsive to therapy. By employing microarray, ChIP, immunoblot and Luciferase reporter assays, we identified a unique mechanism through which BMI1 rescues tumor cells from chemotherapy. We found that BMI1 regulates (i) activity of TCF4 transcriptional factor and (ii) binding of TCF4 to the promoter region of anti-apoptotic BCL2 gene. Notably, an increased TCF4 occupancy on BCL2 gene was observed in prostatic tissues exhibiting high BMI1 levels. Using tumor cells other than CaP, we also showed that regulation of TCF4-mediated BCL2 by BMI1 is universal. It is noteworthy that forced expression of BMI1 was observed to drive normal cells to hyperproliferative mode. We show that targeting BMI1 improves the outcome of docetaxel therapy in animal models bearing chemoresistant prostatic tumors. We suggest that BMI1 could be exploited as a potential molecular target for therapeutics to treat chemoresistant tumors.