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

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

Background

Polycomb Group (PcG) proteins are epigenetic silencers involved in maintaining cellular identity, and their deregulation can result in cancer. Expression of Mel-18 and Bmi-1 has been studied in tumor tissue, but not in adjacent non-cancerous breast epithelium. Our study compares the expression of the two genes in normal breast epithelium of cancer patients and relates it to the level of expression in the corresponding tumors as well as in breast epithelium of healthy women.

Methods

A total of 79 tumors, of which 71 malignant tumors of the breast, 6 fibroadenomas, and 2 DCIS were studied and compared to the reduction mammoplastic specimens of 11 healthy women. In addition there was available adjacent cancer free tissue for 23 of the malignant tumors. The tissue samples were stored in RNAlater, RNA was isolated to create expression microarray profile. These two genes were then studied more closely first on mRNA transcription level by microarrays (Agilent 44 K) and quantitative RT-PCR (TaqMan) and then on protein expression level using immunohistochemistry.

Results

Bmi-1 mRNA is significantly up-regulated in adjacent normal breast tissue in breast cancer patients compared to normal breast tissue from noncancerous patients. Conversely, mRNA transcription level of Mel-18 is lower in normal breast from patients operated for breast cancer compared to breast tissue from mammoplasty. When protein expression of these two genes was evaluated, we observed that most of the epithelial cells were positive for Bmi-1 in both groups of tissue samples, although the expression intensity was stronger in normal tissue from cancer patients compared to mammoplasty tissue samples. Protein expression of Mel-18 showed inversely stronger intensity in tissue samples from mammoplasty compared to normal breast tissue from patients operated for breast cancer.

Conclusion

Bmi-1 mRNA level is consistently increased and Mel-18 mRNA level is consistently decreased in adjacent normal breast tissue of cancer patients as compared to normal breast tissue in women having had reduction mammoplasties. Bmi-1/Mel-18 ratio can be potentially used as a tool for stratifying women at risk of developing malignancy.

RNA diagnostics: real-time RT-PCR strategies and promising novel target RNAs

Ribonucleic acid (RNA) is a multifunctional type of molecule, playing critical roles in protein biosynthesis and regulation. In recent years, suppression of protein translation by so-called microRNAs came into the focus of research, especially because deregulation of this process has been shown to play a role in malignant transformation. Furthermore, RNA molecules circulating in the blood have been revealed as a novel class of markers for diagnosis of cancers. Moreover, genetic information of some pathogens is stored as RNA, allowing their sensitive detection using nucleic acid amplification techniques. In this article, the principle of detecting different RNA types by real-time reverse-transcription polymerase chain reaction applications is described. Furthermore, the emerging use of microRNA and circulating RNA profiles complementing the broad spectrum of RNA diagnosis is discussed.

Bmi-1 Regulates Snail Expression and Promotes Metastasis Ability in Head and Neck Squamous Cancer-Derived ALDH1 Positive Cells

Recent studies suggest that ALDH1 is a putative marker for HNSCC-derived cancer stem cells. However, the regulation mechanisms that maintain the stemness and metastatic capability of HNSCC-ALDH1(+) cells remain unclear. Initially, HNSCC-ALDH1(+) cells from HNSCC patient showed cancer stemness properties, and high expression of Bmi1 and Snail. Functionally, tumorigenic properties of HNSCC-ALDH1(+) cells could be downregulated by knockdown of Bmi-1. Overexpression of Bmi-1 altered in expression property ALDH1(-) cells to that of ALDH1(+) cells. Furthermore, knockdown of Bmi-1 enhanced the radiosensitivity of radiation-treated HNSCC-ALDH1(+) cells. Moreover, overexpression of Bmi-1 in HNSCC-ALDH1(-) cells increased tumor volume and number of pulmonary metastatic lesions by xenotransplant assay. Importantly, knock-down of Bmi1 in HNSCC-ALDH1(+) cells significantly decreased distant metastases in the lungs. Clinically, coexpression of Bmi-1/Snail/ALDH1 predicted the worst prognosis in HNSCC patients. Collectively, our data suggested that Bmi-1 plays a key role in regulating Snail expression and cancer stemness properties of HNSCC-ALDH1(+) cells.

Detection of cell-free RNA in children with neuroblastoma and comparison with that of whole blood cell RNA

BACKGROUND

Since there is no validated assay to monitor disease in children with neuroblastoma (NB), we tested whether NB specific cell-free RNA could be detected in their plasma samples. Moreover, with the aim of reducing patients' discomfort, we compared this assay to a recently standardized procedure that uses a larger amount of whole blood.

PROCEDURES

Using conditions that excluded RNA recovery from contaminating tumor cells, the total amount of cell-free RNA present in healthy children and patients with NB was quantified. Expression of tyrosine hydroxylase (TH) was assayed by quantitative RT-PCR.

RESULTS

In patients with NB the amount of cell-free RNA was higher than in healthy children. However, it was less and more degraded than in healthy adults. The median amount of cell-free RNA that was reverse transcribed, measured through the use of standard curves for reference genes, was 0.03 (range 0-30) pg of input RNA, that is, always less than 1/10,000 of that reverse transcribed from total RNA extracted from whole cells. Despite the presence of disease and the positive results obtained with RNA extracted from peripheral blood cells, few cell-free RNA samples tested positive by the TH assay. Similar results were obtained also with TH primers specifically designed to amplify 50 bp RNA fragments.

CONCLUSION

These findings suggest that for monitoring disease status detection of cell-free tumor-specific RNAs in patients with NB is not a reliable alternative to whole cell RNA.

Relevance of circulating tumor cells, extracellular nucleic acids, and exosomes in breast cancer

Early detection of cancer is vital to improved overall survival rates. At present, evidence is accumulating for the clinical value of detecting occult tumor cells in peripheral blood, plasma, and serum specimens from cancer patients. Both molecular and cellular approaches, which differ in sensitivity and specificity, have been used for such means. Circulating tumor cells and extracellular nucleic acids have been detected within blood, plasma, and sera of cancer patients. As the presence of malignant tumors are clinically determined and/or confirmed upon biopsy procurement-which in itself may have detrimental effects in terms of stimulating cancer progression/metastases-minimally invasive methods would be highly advantageous to the diagnosis and prognosis of breast cancer and the subsequent tailoring of targeted treatments for individuals, if reliable panels of biomarkers suitable for such an approach exist. Herein, we review the current advances made in the detection of such circulating tumor cells and nucleic acids, with particular emphasis on extracellular nucleic acids, specifically extracellular mRNAs and discuss their clinical relevance.

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.

Expression of aldehyde dehydrogenase 1 (ALDH1) is associated with basal-like markers and features of aggressive tumours in African breast cancer

BACKGROUND

Putative breast cancer stem cells might express surface markers such as aldehyde dehydrogenase 1 (ALDH1) and BMI-1 proteins. The aim of this study was to explore the expression of these proteins in breast cancers from an African population and their associations with the basal-like phenotype (BLP) and other molecular characteristics.

METHODS

We analysed 192 paraffin-embedded breast carcinoma samples by tissue microarrays and immunohistochemical methods.

RESULTS

In total, 88 tumours (48%) expressed ALDH1, whereas 46 (25%) expressed BMI-1 protein. Expression of ALDH1 was associated with high histological grade (P<0.0005), high mitotic count (P<0.0005), high nuclear grade (P<0.0005), oestrogen receptor (ER) negativity (P<0.0005), progesterone receptor (PR) negativity (P=0.009), p53 expression (P=0.034), cytokeratin 5/6 positivity (P=0.008), epidermal growth factor receptor (EGFR) expression (P=0.015) and the BLP (P<0.0005), whereas it was inversely associated with BMI-1 staining (P=0.009). On the other hand, BMI-1 expression was associated with low histological grade (P=0.004) and ER positivity (P=0.001).

CONCLUSION

There was a high prevalence of ALDH1 expression among breast carcinomas and associations with basal markers and features of aggressive tumours. Studies are required to elucidate the importance of these findings for improved understanding of breast cancer biology.

RNAi-mediated silencing of the Bmi-1 gene causes growth inhibition and enhances doxorubicin-induced apoptosis in MCF-7 cells

The oncogene Bmi-1 is a member of the Polycomb group gene family. Its expression is found to be greatly increased in a number of malignant tumors including breast cancer. This could suggest Bmi-1 as a potent therapeutic target. In this study, RNAi was introduced to down-regulate the expression of Bmi-1 in a highly malignant breast adenocarcinoma cell line, MCF-7. A thorough study of the biological behavior and chemosensitivity changes of the MCF-7 cells was carried out in context to the therapeutic potential of Bmi-1. The results obtained indicated that siRNA targeting of Bmi-1 could lead to an efficient and specific inhibition of endogenous Bmi-1 activity. The mRNA and protein expression of Bmi-1 were determined by RT-PCR and Western blot, respectively. Furthermore, silencing of Bmi-1 resulted in a drastic inhibition of the growth of MCF-7 cells as well as G₁ /S phase transition. The number of target cells was found to increase in phase G ₀ /G ₁ and decrease in the S phase, but no increase in the basal level of apoptosis was noticed. On the other hand, a reduction in the expression of cyclin D1 and an increase in the expression of p21 were also noticed. Silencing of Bmi-1 made the MCF-7 cells more sensitive to the chemotherapeutic agent doxorubicin and induced a significantly higher percentage of apoptotic cells. Here, we report on a study regarding the RNAi-mediated silencing of the Bmi-1 gene in breast cancer.

Circulating tumor cells (CTCs): detection methods and their clinical relevance in breast cancer

The enumeration of circulating tumor cells has long been regarded as an attractive diagnostic tool, as circulating tumor cells are thought to reflect aggressiveness of the tumor and may assist in therapeutic decisions in patients with solid malignancies. However, implementation of this assay into clinical routine has been cumbersome, as a validated test was not available until recently. Circulating tumor cells are rare events which can be detected specifically only by using a combination of surface and intracellular markers, and only recently a number of technical advances have made their reliable detection possible. Most of these new techniques rely on a combination of an enrichment and a detection step. This review addresses the assays that have been described so far in the literature, including the enrichment and detection steps and the markers used in these assays. We have focused on breast cancer as most clinical studies on CTC detection so far have been done in these patients.

Expression of Bmi-1 is a prognostic marker in bladder cancer

Background

The molecular mechanisms of the development and progression of bladder cancer are poorly understood. The objective of this study was to analyze the expression of Bmi-1 protein and its clinical significance in human bladder cancer.

Methods

We examined the expression of Bmi-1 mRNA and Bmi-1 protein by RT-PCR and Western blot, respectively in 14 paired bladder cancers and the adjacent normal tissues. The expression of Bmi-1 protein in 137 specimens of bladder cancer and 30 specimens of adjacent normal bladder tissue was determined by immunohistochemistry. Statistical analyses were applied to test the relationship between expression of Bmi-1, and clinicopathologic features and prognosis.

Results

Expression of Bmi-1 mRNA and protein was higher in bladder cancers than in the adjacent normal tissues in 14 paired samples (P < 0.01). By immunohistochemical examination, five of 30 adjacent normal bladder specimens (16.7%) versus 75 of 137 bladder cancers (54.3%) showed Bmi-1 protein expression (P < 0.05). Bmi-1 protein expression was intense in 20.6%, 54.3%, and 78.8% of tumors of histopathological stages G1, G2, and G3, respectively (P < 0.05). Expression of Bmi-1 protein was greater in invasive bladder cancers than in superficial bladder cancers (81.5% versus 32.5%, P < 0.05). In invasive bladder cancers, the expression of Bmi-1 protein in progression-free cancers was similar to that of cancers that have progressed (80.0% versus 82.4%, P > 0.5). In superficial bladder cancers, the expression of Bmi-1 protein in recurrent cases was higher than in recurrence-free cases (62.5% versus 13.7%, P < 0.05). Bmi-1 expression was positively correlated with tumor classification and TNM stage (P < 0.05), but not with tumor number (P > 0.05). Five-year survival in the group with higher Bmi-1 expression was 50.8%, while it was 78.5% in the group with lower Bmi-1 expression (P < 0.05). Patients with higher Bmi-1 expression had shorter survival time, whereas patients with lower Bmi-1 expression had longer survival time (P < 0.05).

Conclusion

Expression of Bmi-1 was greater in bladder cancers than in the adjacent normal tissues. The examination of Bmi-1 protein expression is potentially valuable in prognostic evaluation of bladder cancer.

Cancer stem cell markers in common cancers - therapeutic implications

Rapid advances in the cancer stem cell (CSC) field have provided cause for optimism for the development of more reliable cancer therapies in the future. Strategies aimed at efficient targeting of CSCs are becoming important for monitoring the progress of cancer therapy and for evaluating new therapeutic approaches. Here, we characterize and compare the specific markers that have been found to be present on stem cells, cancer cells and CSCs in selected tissues (colon, breast, liver, pancreas and prostate). We then discuss future directions of this intriguing new research field in the context of new diagnostic and therapeutic opportunities.

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.

Detection, clinical relevance and specific biological properties of disseminating tumour cells

Most cancer deaths are caused by haematogenous metastatic spread and subsequent growth of tumour cells at distant organs. Disseminating tumour cells present in the peripheral blood and bone marrow can now be detected and characterized at the single-cell level. These cells are highly relevant to the study of the biology of early metastatic spread and provide a diagnostic source in patients with overt metastases. Here we review the evidence that disseminating tumour cells have a variety of uses for understanding tumour biology and improving cancer treatment.

Prognostic value of Bmi-1 oncoprotein expression in NSCLC patients: a tissue microarray study

PURPOSE

Bmi-1 is a Polycomb group member which participates in many physiological processes as well as in a wide spectrum of cancers. The aim of this study was to investigate Bmi-1 expression in non-small cell lung cancer (NSCLC) in respect to clinicopathological features and therapeutic outcomes.

METHODS

Immunohistochemical staining for Bmi-1 was performed on tissue microarrays (TMAs) constructed from 179 formalin-fixed and paraffin-embedded NSCLC samples (106 squamous, 58 adeno-, and 15 large cell carcinomas). Data were subject to statistical analysis by SPSS.

RESULTS

Overall evaluation of all tumor cases showed that 20 (11.43%) were negative, 37 (21.14%) showed weak, 65 (37.14%) moderate and 57 (32.57%) strong nuclear positivity for Bmi-1. Statistical analysis of our data revealed that the expression of Bmi-1 was significantly higher in stage III (P = 10(-6)) and stage IV (P = 10(-5)) tumors compared to stages I and II tumors. The administration of adjuvant chemotherapy significantly increased DFS at stage I and II patients who did not express Bmi-1 when compared to their Bmi-1 positive counterparts (P = 0.05).

CONCLUSIONS

Our results suggest that Bmi-1 is significantly associated with progression of NSCLC and might serve as a prognostic marker of adverse disease outcome.

Expression of Bmi-1 protein in tumor tissues is associated with favorable prognosis in breast cancer patients

PURPOSE

Abnormal expression of the cell cycle regulatory protein Bmi-1 has been studied in breast cancer, but the clinical relevance has not been fully elucidated. We studied the expression of Bmi-1 protein in breast cancer patients to define its clinical significance in breast cancer.

EXPERIMENTAL DESIGN

Tissue microarrays were performed to evaluate the expression of Bmi-1 by immunohistochemistry in tumor tissues from 960 patients with stage I-III breast cancer. We assessed the relationship between the expression of Bmi-1 and pathologic prognostic indices as well as clinical long-term follow up outcome.

RESULTS

Bmi-1 was expressed in 53.2% of breast cancer patients by immunohistochemistry, and the expression of Bmi-1 was significantly correlated with favorable prognostic indices at diagnosis. In univariate analysis, patients with Bmi-1 expression showed favorable relapse-free survival (88.6+/-2.7% vs. 72.3+/-4.3%, P=0.041) and favorable overall survival (93.5+/-2.2% vs. 82.6+/-3.5%, P<0.001) than patients without Bmi-1 expression. According to multivariate analyses, Bmi-1 expression was identified as independent prognostic factor for overall survival with a statistical significance (hazard ratio of Bmi-1 (-) patients compared to Bmi-1 (+) patients, 1.744; 95% CI, 1.013-3.003; P=0.045). This correlation of Bmi-1 expression with favorable overall survival was maintained in patients underwent uniform chemotherapy, regardless of undergoing adjuvant chemotherapy. In a subset analysis according to ER status, Bmi-1 expression associated with favorable overall survival only in ER-positive patients.

CONCLUSIONS

Bmi-1 expression assessed with Immunohistochemistry may be associated with favorable overall survival in breast cancer patients, especially in patients with ER-positive breast cancer.