Independent prognostic value of the basal-like phenotype of breast cancer and associations with EGFR and candidate stem cell marker BMI-1

Stathmin expression associates with vascular and immune responses in aggressive breast cancer subgroups

Studies indicate that stathmin expression associates with PI3K activation in breast cancer, suggesting stathmin as a marker for targetable patient subgroups. Here we assessed stathmin in relation to tumour proliferation, vascular and immune responses, BRCA1 germline status, basal-like differentiation, clinico-pathologic features, and survival. Immunohistochemical staining was performed on breast cancers from two series (cohort 1, n = 187; cohort 2, n = 198), and mass spectrometry data from 24 cases and 12 breast cancer cell lines was examined for proteomic profiles. Open databases were also explored (TCGA, METABRIC, Oslo2 Landscape cohort, Cancer Cell Line Encyclopedia). High stathmin expression associated with tumour proliferation, p53 status, basal-like differentiation, BRCA1 genotype, and high-grade histology. These patterns were confirmed using mRNA data. Stathmin mRNA further associated with tumour angiogenesis, immune responses and reduced survival. By logistic regression, stathmin protein independently predicted a BRCA1 genotype (OR 10.0, p = 0.015) among ER negative tumours. Cell line analysis (Connectivity Map) implied PI3K inhibition in tumours with high stathmin. Altogether, our findings indicate that stathmin might be involved in the regulation of tumour angiogenesis and immune responses in breast cancer, in addition to tumour proliferation. Cell data point to potential effects of PI3K inhibition in tumours with high stathmin expression.

Prognostic Significance of ALDH1, Bmi1, and OCT4 Expression in Oral Epithelial Dysplasia and Oral Squamous Cell Carcinoma

BACKGROUND

Increasing evidence suggests the involvement of cancer stem cells (CSCs) in both oral epithelial dysplasia (OED) and oral squamous cell carcinoma (OSCC). Among the various CSC markers, aldehyde dehydrogenase (ALDH) 1, B cell-specific Moloney murine leukaemia virus integration site 1 (Bmi1), and octamer-binding protein 4 (OCT4) have been noted to increase in OSCC. The aim of the study was to analyze ALDH1, Bmi1, and OCT4 expression in OED and OSCC with clinicopathologic correlation and survival analysis.

METHODS

A total of 40 cases each of OED and OSCC were retrieved from departmental archives. Expression of ALDH1, Bmi1, and OCT4 was analyzed using immunohistochemistry and was correlated with clinicopathological parameters. A follow-up ranging from 6 to 52 months was considered for Kaplan-Meier survival analysis. The log-rank test was performed to analyze significant difference in survival rates.

RESULTS

The expression levels of ALDH1, Bmi1, and OCT4 increased significantly from OED through OSCC (P < .05). The expression of ALDH1 and OCT4 showed a significant correlation with lymph node metastasis. Positive cases of ALDH1 showed a significantly reduced survival rate compared to cases showing negative expression. Kaplan-Meier survival analysis showed a significant reduction of survival rate (P = .00) in patients showing a positive expression for all the 3 markers.

CONCLUSION

ALDH1 and OCT4 could be used as individual prognostic markers for assessing prognosis. ALDH1, Bmi1, and OCT4 could be used as a collective panel of markers to enable surgeons in predicting the prognosis of patients and thereby carry out prompt follow-up for such cases.

Hsp90α Mediates BMI1 Expression in Breast Cancer Stem/Progenitor Cells through Facilitating Nuclear Translocation of c-Myc and EZH2

Heat shock protein 90 (Hsp90) is a molecular chaperone that facilitates the correct folding and functionality of its client protein. Numerous Hsp90-client proteins are involved in cancer development. Thus, Hsp90 inhibitors have potential applications as anti-cancer drugs. We previously discovered that Hsp90α expression increased in breast cancer stem cells (BCSCs), which can initiate tumorigenesis and metastasis and resist treatment. In the present study, we further demonstrated that 17-dimethylaminoethylamino-17-demethoxygeldanamycin (17-DMAG), an inhibitor of Hsp90, could suppress the self-renewal of BCSCs by downregulating B lymphoma Mo-MLV insertion region 1 homolog (BMI1), a polycomb family member with oncogenic activity in breast cancer. Through immunoprecipitation analysis, we found that BMI1 did not interact with Hsp90α and that the downregulation of BMI1 by 17-DMAG was mediated by the inhibition of c-Myc and enhancement of zeste homolog 2 (EZH2) expression. The transcriptional and BMI1 promoter-binding activities of c-Myc in BCSCs were inhibited by 17-DMAG treatment. The overexpression of EZH2 attenuated the inhibitory effect of 17-DMAG on BMI1 and c-Myc expression. Furthermore, Hsp90α could be co-immunoprecipitated with c-Myc and EZH2 and bind to the BMI1 promoter. Treatment with 17-DMAG decreased the nuclear expression of EZH2 and c-Myc but not that of Hsp90α. In conclusion, our data suggested that Hsp90α could positively regulate the self-renewal of BCSCs by facilitating the nuclear translocation of c-Myc and EZH2 to maintain BMI1 expression.

Stemness-Related Markers in Cancer

Cancer stem cells (CSCs), with their self-renewal ability and multilineage differentiation potential, are a critical subpopulation of tumor cells that can drive tumor initiation, growth, and resistance to therapy. Like embryonic and adult stem cells, CSCs express markers that are not expressed in normal somatic cells and are thus thought to contribute towards a 'stemness' phenotype. This review summarizes the current knowledge of stemness-related markers in human cancers, with a particular focus on important transcription factors, protein surface markers and signaling pathways.

Strong Expression of Hypoxia-Inducible Factor-1α (HIF-1α) Is Associated with Axl Expression and Features of Aggressive Tumors in African Breast Cancer

PURPOSE

Inhibition of hypoxia-inducible factor (HIF) and Axl receptor tyrosine kinase is being evaluated for targeted therapy in solid tumors. Both HIF-1α and Axl influence tumor growth and metastatic potential, and they have been linked to treatment failure in many cancers. However, there is a lack of reports on HIF-1α expression in African breast cancer, which has a poor prognosis, and novel treatment targets must therefore be established. Here, we aimed to evaluate HIF-1α in relation to Axl expression, angiogenesis markers, and other tumor characteristics in a series of African breast cancer.

METHODS

Using immunohistochemistry, we examined 261 invasive breast cancers on tissue microarrays for HIF-1α and Axl as well as several other markers, and a subset of 185 cases had information on VEGF (vascular endothelial growth factor) expression, microvessel density (MVD), proliferating microvessel density (pMVD) and vascular proliferation index (VPI) for important comparisons.

RESULTS

Strong HIF-1α expression was associated with increased Axl (p = 0.007), VEGF (p<0.0005), and p53 (p = 0.032) expression, as well as high tumor cell proliferation by Ki-67 (p = 0.006), and high tumor grade (p = 0.003). Tumors with strong HIF-1α expression had significantly higher MVD (p = 0.019) and higher pMVD (p = 0.027) than tumors with weak expression.

CONCLUSIONS

High HIF-1α expression is significantly associated with Axl and VEGF expression, and with markers of poor prognosis in this series of breast cancer, suggesting HIF-1α and Axl as potential therapeutic targets in African breast cancer.

SHP2 acts both upstream and downstream of multiple receptor tyrosine kinases to promote basal-like and triple-negative breast cancer

INTRODUCTION

Dysregulated receptor tyrosine kinase (RTK) signaling is a common occurrence in basal-like and triple-negative breast cancer (BTBC). As a result, RTK-targeting therapies have been initiated but proved difficult, mainly owing to the multiplicity of dysregulated RTKs. Hence, targeting master regulators of RTK signaling might alleviate this obstacle. Before that, however, defining the mechanism of such molecules is required. In this report, we show that the Src homology phosphotyrosyl phosphatase 2 (SHP2) is a master regulator of RTK expression and signaling in BTBC.

METHODS

Xenograft tumor growth studies were used to determine the effect of SHP2 inhibition on tumorigenesis and/or metastasis. Cell proliferation rate, anchorage-independent growth, mammosphere formation, and ALDEFLUOR assays were used to compare the relative functional importance of SHP2 and the epidermal growth factor receptor (EGFR) in BTBC cells. Immunohistochemistry and immunofluorescence analyses were used to determine the state of SHP2 and EGFR coexpression in BTBC. Analysis of mitogenic and cell survival signaling was performed to show SHP2's role in signaling by multiple RTKs.

RESULTS

Inhibition of SHP2 in BTBC cells suppresses their tumorigenic and metastatic properties. Because EGFR is the most commonly dysregulated RTK in BTBC, we first tested the effect of SHP2 inhibition on EGFR signaling and found that SHP2 is important not only for mediation of the Ras/extracellular signal-regulated kinase and the phosphatidyl inositol 3-kinase/Akt signaling pathways but also for the expression of the receptor itself. The existence of a tight association between SHP2 and EGFR expression in tumors and cell lines further suggested the importance of SHP2 in EGFR expression. Comparison of relative biological significance showed the superiority of SHP2 inhibition over that of EGFR, suggesting the existence of additional RTKs regulated by SHP2. Indeed, we found that the expression as well as the signaling efficiency of c-Met and fibroblast growth factor receptor 1, two other RTKs known to be dysregulated in BTBC, are SHP2-dependent. To our knowledge, this is the first demonstration of SHP2 acting both upstream and downstream of RTKs to promote signaling.

CONCLUSIONS

SHP2 upregulates the expression and signaling of multiple RTKs to promote BTBC. These findings provide a mechanistic explanation for the superiority of SHP2 inhibition in BTBC.

Prognostic role of high Bmi-1 expression in Asian and Caucasian patients with solid tumors: a meta-analysis

Recently, many studies have shown that the B-cell-specific moloney leukemia virus insertion site 1 (Bmi-1) exhibits altered expression in various cancers and may serve as prognostic biomarkers. We performed a meta-analysis to evaluate the prognostic role of Bmi-1 expression in solid cancers. Studies were recruited by searching PubMed, Embase and the Cochrane Library. Thirty-nine articles including 40 studies were involved in this meta-analysis. Our results indicated that the Bmi-1 showed the opposite prognostic effect in Asian and Caucasian populations. High Bmi-1 expression as a negative predictor for overall survival (OS) in Asian patients (HR=1.96, 95% CI 1.62-2.36), but a positive predictor in Caucasian populations (HR=0.77, 95% CI 0.63-0.93). Furthermore, we took a further subgroup analysis based on tumor type in these two populations, respectively. In Asian cases, high expression of Bmi-1 was associated with poor OS in oesophageal carcinoma (HR=1.93, 95% CI 1.52-2.46), gastric cancer (HR=1.50, 95% CI 1.22-1.85), lung cancer (HR=1.73, 95% CI 1.05-2.85), cervical cancer (HR=2.80, 95% CI 2.26-3.47) and colorectal cancer (HR=3.36, 95% CI 2.19-5.15), rather than in breast cancer and HCC. In Caucasian populations, high expression of Bmi-1 was associated with better OS in breast cancer (HR=0.70, 95% CI 0.51-0.97), but it showed no significance in oesophageal carcinoma. In conclusion, high Bmi-1 expression was significantly associated with poor survival in Asian patients with oesophageal carcinoma, gastric cancer, lung cancer, colorectal cancer and cervical carcinoma, whereas high level of Bmi-1 can predict better prognosis in Caucasian patients with breast cancer.

Pulmonary neuroendocrine tumors: study of 90 cases focusing on clinicopathological characteristics, immunophenotype, preoperative biopsy, and frozen section diagnoses

BACKGROUND AND OBJECTIVES

Pulmonary neuroendocrine tumors have a prognostic spectrum including typical carcinoid (TC), atypical carcinoid (AC), small cell carcinoma (SCLC), and large cell neuroendocrine carcinoma (LCNEC). We conducted a retrospective study to compare their clinicopathological characteristics, immunophenotype, preoperative biopsy and frozen section diagnoses, and prognosis.

METHODS

Ninety cases of surgically treated pulmonary neuroendocrine tumors were studied. Immunohistochemical studies were performed using antibodies to chromogranin A, synaptophysin, and CD56. The preoperative biopsy and frozen section diagnoses were reviewed.

RESULTS

The 5-year survival rates for TC, AC, SCLC, and LCNEC were 96.6%, 66.7%, 42.4%, and 38.0%, respectively. T stage and pleural status correlated with outcome of SCLC and LCNEC, but N-stage and overall TNM stage did not. In preoperative biopsy, accurate diagnosis was achieved in 5 of 11 TC, 2 of 4 AC, 6 of 15 SCLC, and 0 of 5 LCNEC cases. Using frozen sections, accurate diagnosis was achieved in 8 of 12 TC, 2 of 11 SCLC, and 0 of 11 LCNEC cases.

CONCLUSIONS

LCNEC was the most difficult to diagnose using either preoperative biopsy or frozen sections. T stage and pleural status can predict outcome of SCLC and LCNEC.

High expression of CHRNA1 is associated with reduced survival in early stage lung adenocarcinoma after complete resection

BACKGROUND

Non-small cell lung cancer (NSCLC) is the leading cause of cancer deaths around the world, and a high recurrence rate after complete resection is an important issue reducing the cure rate and survival of patients with early stage NSCLC. Several pathologic biomarkers are associated with recurrence in early stage lung cancer after complete resection.

METHODS

We evaluated the expression and prognostic value of the α1 subunit of the nicotinic acetylcholine receptor (CHRNA1) as well as other pathologic features of tumor tissues resected from patients with stage I adenocarcinoma of the lung.

RESULTS

A high ratio (173/185) of CHRNA1 expression (93.5 %) was found in stage I lung adenocarcinoma. In the multivariate survival analysis, tumor necrosis, angiolymphatic invasion, perineural invasion, and CHRNA1 expression were independent poor prognostic factors for both recurrence-free and overall survival (OS). Patients expressing CHRNA1 had worse median recurrence-free survival (60.6 vs. 77.9 months, P = 0.03) and OS (65.1 vs. 77.9 months, P = 0.04) compared with CHRNA1-negative patients.

CONCLUSIONS

CHRNA1 expression could be directly tested from the tumor after complete resection. In early stage NSCLC, it could be a useful prognostic factor for recurrence and survival.

Nuclear BMI-1 expression in laryngeal carcinoma correlates with lymph node pathological status

BACKGROUND

The main cause of treatment failure and death in laryngeal squamous cell carcinoma is metastasis to the regional lymph nodes. The current clinical staging criteria fail to differentiate patients with occult metastasis from patients without metastasis. Identifying molecular markers of the disease might improve our understanding of the molecular mechanisms underlying the pathogenesis and development of laryngeal carcinoma and may help improve clinical staging and treatment.

METHODS

Sixty-four previously untreated patients who underwent surgical excision of laryngeal squamous cell carcinoma with neck dissection were included in this study. The expression of B cell-specific Moloney murine leukemia virus integration site 1 (BMI-1) was examined immunohistochemically on formalin-fixed paraffin-embedded primary tissue specimens.

RESULTS

Nuclear expression of BMI-1 (nBMI-1) was detected in 32 of the 64 tumors (50%), cytoplasmic expression of BMI-1 (cBMI-1) was detected in 22 (34.4%), and 10 tumors (15.6%) showed no BMI-1 immunoreactivity. High nBMI-1 expression levels (≥ 10) were detected in 28 of the 32 (87.5%) nBMI-1-positive patients. Multivariate analysis including age at diagnosis, grade, tumor location, TNM status, and nBMI-1 expression showed that a high nBMI-1 expression level was an independent prognostic factor for lymph node metastasis.

CONCLUSION

The expression of BMI-1 in patients with laryngeal carcinoma seems to correlate with lymph node metastasis.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Microvessel proliferation by co-expression of endothelial nestin and Ki-67 is associated with a basal-like phenotype and aggressive features in breast cancer

BACKGROUND

To quantify tumour angiogenesis, microvessel density (MVD) has been widely used. We here present a novel angiogenesis marker, microvessel proliferation (MVP), based on dual immunohistochemical staining of nestin and Ki-67. Immature endothelial cells express nestin, and when co-expressed with the proliferation marker Ki-67, the number of proliferating immature blood vessels can be measured.

MATERIALS AND METHODS

Microvessel proliferation was evaluated in 178 breast cancer samples and estimated by vascular proliferation index (VPI), the ratio between the number of vessels containing proliferating endothelial cells and the total number of immature vessels.

RESULTS

High VPI was strongly associated with several markers of aggressive breast cancer, such as negative oestrogen receptor (ER) status (p = 0.003), high tumour cell proliferation by Ki-67 (p = 0.004), high p53 expression (p = 0.001), and five profiles for the basal-like phenotype (odds ratios (OR); range 3.4-6.3). Also, high VPI was significantly associated with interval detected breast cancer compared with screening detected lesions (p < 0.0005), and adverse outcome in univariate and multivariate survival analysis (p = 0.034 and p = 0.022, respectively).

CONCLUSION

Microvessel proliferation is a novel marker of ongoing angiogenesis and was associated with aggressive tumour features, basal-like phenotypes, interval presentation, and prognosis in this series of breast cancer.

Overexpression of Cell Cycle Progression Inhibitor Geminin is Associated with Tumor Stem-Like Phenotype of Triple-Negative Breast Cancer

PURPOSE

Triple-negative breast cancer, has a significant clinical relevance being associated with a shorter median time to relapse and death and does not respond to endocrine therapy or other available targeted agents. For this reason, identifying the molecular pathways associated with increased aggressiveness, for example the presence of stem cell populations within the tumor and alteration of genes associated with cell cycle regulation represents an important objective in the clinical research into this neoplasm.

METHODS

To investigate the role of cell cycle progression inhibitor Geminin in triple-negative breast cancers and its potential correlation with stem-like phenotype of this neoplasm, we used tissue microarray technology to build a specific triple-negative breast cancer tissue micro-array. Geminin and cancer stem cell marker CD133 expression was further investigated at the mRNA level for selected breast tumor samples through realtime polymerase chain reaction quantification.

RESULTS

Our results showed that CD133 expression was significantly associated to high Geminin expression (p=0.017), a strong association between Ki-67 and tumor grade (p=0.020) and an inverse association between Geminin expression and lymphonode metastases (p=0.058), and a trend of statistically significance between Geminin marker expression and survival of triple-negative breast cancer patients (p=0.076).

CONCLUSION

The strong association between the expression of CD133 and Geminin could be useful in molecular stratification of breast tumors and in particular of triple-negative breast cancers.

Expression of BMI1 and p16 in laryngeal squamous cell carcinoma

BACKGROUND

The clinical evolution of laryngeal squamous cell carcinoma (SCC) is undetectable with the current staging criteria. To more completely understand the biology of laryngeal SCC, we assessed the expression of the proteins B-cell-specific Moloney murine leukemia virus integration site 1 (BMI1) and p16.

METHODS

We assessed immunohistochemically the expression of BMI1 and p16 in 25 laryngeal SCCs at different stages.

RESULTS

High BMI1 expression was detected in 11.7% of glottic tumors and in 50% of supraglottic tumors. No significant differences were observed in the patients' clinical data after they were stratified by the tumor expression of p16. The expression of nuclear BMI1 in the absence of p16 immunoreactivity correlated significantly with the pN status of the primary tumors.

CONCLUSION

Nuclear BMI1 expression in the absence of p16 expression seems to characterize a subset of patients with a high risk of developing lymph node metastasis.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Overexpression of T-LAK cell-originated protein kinase predicts poor prognosis in patients with stage I lung adenocarcinoma

Tumor recurrence is the most common cause of disease failure after surgical resection in early-stage lung adenocarcinoma. Identification of clinically relevant prognostic markers could help to predict patients with high risk of disease recurrence. A meta-analysis of available lung adenocarcinoma microarray datasets revealed that T-LAK cell-originated protein kinase (TOPK), a serine/threonine protein kinase, is overexpressed in lung cancer. Using stable cell lines with overexpression or knockdown of TOPK, we have shown that TOPK can promote cell migration, invasion, and clonogenic activity in lung cancer cells, suggesting its crucial role in lung tumorigenesis. To evaluate the prognostic value of TOPK expression in resected stage I lung adenocarcinoma, a retrospective analysis of 203 patients diagnosed with pathological stage I lung adenocarcinoma was carried out to examine the expression of TOPK by immunohistochemistry (IHC). The prognostic significance of TOPK overexpression was examined. Overexpression of TOPK (IHC score >3) was detected in 67.0% of patients, and these patients were more frequently characterized with disease recurrence and angiolymphatic invasion. Using multivariate analysis, patient age (>65 years old; P = 0.002) and TOPK overexpression (IHC score >3; P < 0.001) significantly predicted a shortened overall survival. Moreover, TOPK overexpression (IHC score >3; P = 0.005) also significantly predicted a reduced time to recurrence in the patients. Our results indicate that overexpression of TOPK could predetermine the metastatic capability of tumors and could serve as a significant prognostic predictor of shortened overall survival and time to recurrence.

Bmi-1 induces radioresistance in MCF-7 mammary carcinoma cells

Bmi-1, a member of the polycomb family, it is involved in self renewal of stem cells and functions as an oncogene in many malignant human cancer types. Recent studies have demonstrated that Bmi-1 is a predictive factor for poor patient prognosis. However, the underlying mechanisms of radioresistance mediated by Bmi-1 are poorly understood. In this study, the dose-survival relationship was analyzed using a clonogenic survival assay and combined radiation treatment with Bmi-1 overexpression or silencing. DNA double-strand break (DSB) and repair was assessed by immunofluorescence staining of γH2AX foci. In addition, mitochondrial membrane potential was detected between Bmi-1 knockdown and control MCF-7 cells after irradiation. Apoptosis and cell cycle were evaluated by flow cytometry. We found that exposure of MCF-7 cells overexpressing Bmi-1 to ionizing radiation resulted in dramatically enhanced survival relative to control cells, whereas cells with silenced Bmi-1 showed markedly reduced survival. Bmi-1 inhibition significantly increased DSBs and decreased DSB repair. Furthermore, Bmi-1 knockdown induced loss of mitochondrial membrane potential and enhanced apoptosis by up-regulating p53, p21, Bax expression and down-regulating p-AKT and Bcl-2 expression. These results indicate that Bmi-1 may play an important role in radiosensitivity, and the suppression of its expression might be a potential therapeutic target for breast cancer.

SiRNA-mediated silencing of the Bmi-1gene inhibits cell invasion and metastasis in human hepatocellular carcinoma cell line MHCC97-H

AIM: To investigate the effect of small interference RNA (siRNA)-mediated silencing of the Bmi-1gene on cell invasion and metastasis in human hepatocellular carcinoma cell line MHCC97-H.

METHODS: Chemically synthesized siRNA duplex targeting the Bmi-1 gene (Bmi-1-siRNA) was transiently transfected into MHCC97-H cells, which have high metastatic potential, using Lipofectamine 2000. Transfection efficiency was evaluated by flow cytometry (FCM). Bmi-1 mRNA and protein expression was detected by real-time RT-PCR and Western blot, respectively. The effect of Bmi-1 knockdown on cell invasion and migration was analyzed by Transwell chamber assays.

RESULTS: The transfection efficiency achieved using Bmi-1-siRNA was 91%. Compared to the blank group and control siRNA group, transfection with Bmi-1-siRNA effectively down-regulated the expression of Bmi-1mRNA (F = 56.199, P < 0.05) and protein. Bmi-1-siRNA-transfected MHCC97-H cells had lower levels of invasion and migration capacity than cells in the blank group and control-siRNA group (F = 186.66, 12.746, both P < 0.05).

CONCLUSION: SiRNA-mediated silencing of the Bmi-1 gene could significantly inhibit cell invasion and metastasis in human hepatocellular carcinoma cell line MHCC97-H.

P-cadherin expression as a prognostic biomarker in a 3992 case tissue microarray series of breast cancer

P-cadherin is a calcium-dependent cell-cell adhesion glycoprotein. P-cadherin expression is restricted to the myoepithelial cells in normal breast tissue, and aberrant staining has also been described in invasive tumors. Several small studies have reported P-cadherin as a marker of poor outcome in breast cancer patients but its prognostic significance in relation to other variables has not been established in a large series of breast cancers. A tissue microarray was constructed from 3992 cases of invasive breast carcinoma, and P-cadherin expression was evaluated using immunohistochemistry. Median follow-up was 12.5 years. The immunohistochemistry-based definitions of cancer subtypes were luminal (ER+ or PR+/HER2-), luminal/HER2+ (ER+ or PR+/HER2+), HER2+ (ER-/PR-/HER2+), and basal (ER-/PR-/HER2-/CK5/6+ or EGFR+). Clinical covariate and biomarker associations were assessed using contingency tables, and Pearson's χ(2) or Fisher's exact test. Survival associations were assessed using Kaplan-Meier plots, logrank and Breslow tests, and Cox proportional hazards regression analysis. P-cadherin was expressed in 34.8% (1290/3710, 50% cut point) of cases. P-cadherin staining was strongly associated with HER2+ and basal carcinoma subtypes (P<0.0005). P-cadherin-positive patients showed significantly poorer short-term (0-10 years) overall survival, disease-specific survival, distant relapse-free interval, and locoregional relapse-free interval in univariable models (P<0.05). In multivariable Cox models containing standard clinical covariates and cancer subtypes, P-cadherin did not show independent prognostic value. P-cadherin expression was positively associated with histological grade, chemotherapy, Ki-67, EGFR, CK5/6, p53, YB-1, and HER2 expression (P<0.002), and negatively associated with age at diagnosis, ER, PR, and Bcl-2 expression (P<0.0005). This study shows the value of P-cadherin as a marker of poor prognosis. The large sample size of this series clarifies contradictory findings of many smaller studies. P-cadherin positivity is associated with high-grade tumor subtypes and well-established markers of poor prognosis, and may represent a promising antibody therapeutic target.

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.

Distinctive expression of the polycomb group proteins Bmi1 polycomb ring finger oncogene and enhancer of zeste homolog 2 in nonsmall cell lung cancers and their clinical and clinicopathologic significance

BACKGROUND

The polycomb group genes Bmi1 polycomb ring finger oncogene (Bmi1) and enhancer of zeste homolog 2 (EZH2) function as transcriptional repressors involved in gene silencing and in the malignant transformation and biologic aggressiveness of several human carcinomas. In the current study, the authors evaluated Bmi1 and EZH2 protein expression in specimens of human nonsmall cell lung cancer (NSCLC).

METHODS

The authors conducted an immunohistochemical assessment of 157 surgically resected NSCLCs to evaluate the correlation between Bmi1 and EZH2 expression and various features, including clinical, clinicopathologic, and biologic characteristics.

RESULTS

Normal bronchial epithelia revealed abundant expression of Bmi1 and sporadic expression of EZH2. Patients who had high EZH2 expression in tumor cells had a poorer prognosis than patients who had low EZH2 expression in tumor cells all pathologic stages of NSCLC (P = .001) and in pathologic stage I NSCLC (P = .006). Multivariate analysis revealed that high EZH2 expression was a independent, unfavorable prognostic factor in patients with pathologic stage I disease (P = .048). High EZH2 expression was correlated significantly with nonadenocarcinoma histology (P = .001), moderate and poor differentiation (P = .001), advanced pathologic tumor classification (P = .02), and high Ki-67 and cyclin E labeling indices (P < .001). Bmi1 expression, in contrast, was not a significant prognostic factor and was not correlated with any clinicopathologic factors other than early pathologic tumor classification.

CONCLUSIONS

Bmi1 and EZH2 had characteristic and distinctive expression in NSCLCs. High EZH2 expression was correlated with tumor aggressiveness and may provide a novel prognostic marker for NSCLCs.

Development of 'synthetic lethal' strategies to target BRCA1-deficient breast cancer

Recent clinical trials demonstrating the efficacy of poly(ADP-ribose) polymerase (PARP) inhibitors for the treatment of BRCA1-deficient breast cancer have provided support for the 'synthetic lethal' concept of targeted cancer therapeutics. A new study provides further preclinical validation of this concept by demonstrating that BRCA1-deficient mouse mammary tumor cells are selectively sensitive to an inhibitor of the polycomb gene EZH2. The development of polycomb gene inhibitors may provide a novel approach to selectively exploit the molecular alterations in BRCA1-deficient breast tumors.

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.

Inhibition of tumorigenicity and enhancement of radiochemosensitivity in head and neck squamous cell cancer-derived ALDH1-positive cells by knockdown of Bmi-1

Bmi-1, a member of the Polycomb family of transcriptional repressors, is essential for maintaining the self-renewal abilities of adult stem cells. Bmi-1 has been demonstrated to play a role in tumorigenesis in head and neck squamous cell carcinomas (HNSCCs). A recent study has further suggested that ALDH1 may be considered to be a putative marker for HNSCC-derived cancer stem cells. However, the role that Bmi-1 plays in HNSCC-derived ALDH1-positive cells (HNSCC-ALDH1(+)) has yet to be determined. In this study, we demonstrated that HNSCC-ALDH1(+) cells possess tumor initiating properties, are capable of self-renewal, and express higher levels of Bmi-1 as compared to HNSCC-ALDH1(-) cells. To further explore the functional role of Bmi-1 in HNSCC-ALDH1(+) cells, we used a lentiviral vector expressing shRNA to knock down Bmi-1 expression (sh-Bmi-1) in HNSCC-ALDH1(+) cells. Silencing of Bmi-1 significantly enhanced the sensitivity of HNSCC-ALDH1(+) cells to chemoradiation and increased the degree of chemoradiation-mediated apoptosis that occurred. Importantly, knockdown of Bmi-1 increased the effectiveness of radiotherapy and led to the inhibition of tumor growth in nude mice transplanted with HNSCC-ALDH1(+) cells. Kaplan-Meier survival analysis indicated that the mean survival rate of HNSCC-ALDH1(+) tumor-bearing immunocompromised mice treated with radiotherapy was significantly improved by treatment with sh-Bmi-1 as well. In summary, these results suggest that Bmi-1 is a potential target for increasing the sensitivity of HNSCC cancer stem cells to chemoradiotherapy.

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.

Clinicopathological significance of B-cell-specific Moloney murine leukemia virus insertion site 1 expression in gastric carcinoma and its precancerous lesion

AIM: To explore the relation between B-cell-specific Moloney murine leukemia virus insertion site 1 (Bmi-1) expression and the clinicopathological features of gastric carcinoma (GC).

METHODS: Immunohistochemistry was used to detect the expression of Bmi-1 and ki-67. Double-labeling staining was used to display the distribution of Bcl-2⁺/ki-67^- cells in 162 cases of GC and its matched normal mucosa and precancerous lesion.

RESULTS: The positive rate of Bmi-1 expression in GC (52.5%) was significantly higher than that in normal gastric mucosa (21.6%, χ² = 33.088, P < 0.05). The Bmi-1 expression in GC was closely related with the Lauren’s and Borrmann’s classification and clinical stage (χ² = 4.400, 6.122 and 11.190, respectively, P < 0.05). The expression of ki-67 was related to the Borrmann’s classification (χ² = 13.380, P < 0.05). Bcl-2 expression was correlated with the Lauren’s classification (χ² = 4.725, P < 0.05), and the Bmi-1 expression both in GC (r_k = 0.157, P < 0.05) and in intestinal metaplasia (r_k = 0.270, P < 0.05).

CONCLUSION: Abnormal Bmi-1 expression in GC may be involved in cell proliferation, apoptosis and cancerization. This marker can objectively indicate the clinicopathological characteristics of GC.

EZH2 and BMI1 inversely correlate with prognosis and TP53 mutation in breast cancer

Introduction

PolycombGroup (PcG) proteins maintain gene repression through histone modifications and have been implicated in stem cell regulation and cancer. EZH2 is part of Polycomb Repressive Complex 2 (PRC2) and trimethylates H3K27. This histone mark recruits the BMI1-containing PRC1 that silences the genes marked by PRC2. Based on their role in stem cells, EZH2 and BMI1 have been predicted to contribute to a poor outcome for cancer patients.

Methods

We have analysed the expression of EZH2 and BMI1 in a well-characterised dataset of 295 human breast cancer samples.

Results

Interestingly, although EZH2 overexpression correlates with a poor prognosis in breast cancer, BMI1 overexpression correlates with a good outcome. Although this may reflect transformation of different cell types, we also observed a functional difference. The PcG-target genes INK4A and ARF are not expressed in tumours with high BMI1, but they are expressed in tumours with EZH2 overexpression. ARF expression results in tumour protein P53 (TP53) activation, and we found a significantly higher proportion of TP53 mutations in tumours with high EZH2. This may explain why tumours with high EZH2 respond poorly to therapy, in contrast to tumours with high BMI1.

Conclusions

Overall, our data highlight that whereas EZH2 and BMI1 may function in a 'linear' pathway in normal development, their overexpression has different functional consequences for breast tumourigenesis.

EGFR/HER2 in breast cancer: a biological approach for molecular diagnosis and therapy

Novel cancer therapies have focused on specific molecular markers present in malignant tumors. The rationale of targeted therapy relies on the knowledge of molecular mechanisms involved in carcinogenesis and their influence in clinical outcome allied to a more specific and less toxic treatment. Activation of EGF receptor and HER2 is an important factor for initiation and progression of malignancies, including breast cancer where the status of HER2 is an essential step in the diagnostic workup; EGFR overexpression has been associated to the so-called basal-like breast carcinomas, which opens a new avenue for diagnosis and therapeutic approach in these tumors. This review will focus on mechanisms of HER2 and EGF receptor upregulation, the targeted therapies that are currently in use for these receptors, possible combined therapies, as well as the approach for molecular diagnosis from the pathologist's point of view.

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.