Paradoxical regulation of Bcl-2 family proteins by 17beta-oestradiol in human breast cancer cells MCF-7

Estrogen-dependent activation of NCOA3 couples with p300 and NF-κB to mediate antiapoptotic genes in ER-positive breast cancer cells

Circumvention of apoptosis by the elevation of antiapoptotic proteins is an important cause of carcinogenesis. The induction of antiapoptotic genes, including B-cell CLL/lymphoma 2 (BCL2), BCL2 related protein A1 (BCL2A1), BCL2 like 1 (BCL2L1), BCL2L2, and myeloid cell leukemia 1 (MCL1), has been observed in multiple cancers, including breast cancer. However, the underlying mechanisms of their overexpression are still being investigated. Here, we revealed that BCL2, BCL2A1, BCL2L2, and MCL1 but not BCL2L1 were overexpressed in estrogen receptor (ER)-positive breast cancer cells and clinical biopsies. Stimulation with estrogen in ER-positive cell lines resulted in a dose-dependent increase in BCL2, BCL2A1, BCL2L2, and MCL1 mRNA levels. Molecular investigation revealed that nuclear factor kappa B (NF-κB) recruited histone acetyltransferase p300 and nuclear receptor coactivator 3 (NCOA3) to form a transcriptional complex. This complex docked the promoters of BCL2, BCL2A1, BCL2L2, and MCL1 and activated their expression. Interestingly, estrogen exposure dose-dependently activated NCOA3. Depletion of the NCOA3-p300-NF-κB components or blockage of NCOA3 function with inhibitors (gossypol and bufalin) in ER-positive cells suppressed BCL2, BCL2A1, BCL2L2, and MCL1 expression, while also decreasing cell viability, colony formation, cell invasion, and tumor growth. Collectively, our results demonstrate an upstream signaling that activates four antiapoptotic genes in ER-positive breast cancer cells. Importantly, our results also imply that targeting NCOA3 or blocking the assembly of the NCOA3-p300-NF-κB complex may be promising therapeutic strategies for treating ER-positive breast cancer.

Circulating Exosomal microRNAs as Predictive Biomarkers of Neoadjuvant Chemotherapy Response in Breast Cancer

Background: Neoadjuvant chemotherapy (NACT) is an increasingly used approach for treatment of breast cancer. The pathological complete response (pCR) is considered a good predictor of disease-specific survival. This study investigated whether circulating exosomal microRNAs could predict pCR in breast cancer patients treated with NACT. Method: Plasma samples of 20 breast cancer patients treated with NACT were collected prior to and after the first cycle. RNA sequencing was used to determine microRNA profiling. The Cancer Genome Atlas (TCGA) was used to explore the expression patterns and survivability of the candidate miRNAs, and their potential targets based on the expression levels and copy number variation (CNV) data. Results: Three miRNAs before that NACT (miR-30b, miR-328 and miR-423) predicted pCR in all of the analyzed samples. Upregulation of miR-127 correlated with pCR in triple-negative breast cancer (TNBC). After the first NACT dose, pCR was predicted by exo-miR-141, while miR-34a, exo-miR182, and exo-miR-183 predicted non-pCR. A significant correlation between the candidate miRNAs and the overall survival, subtype, and metastasis in breast cancer, suggesting their potential role as predictive biomarkers of pCR. Conclusions: If the miRNAs identified in this study are validated in a large cohort of patients, they might serve as predictive non-invasive liquid biopsy biomarkers for monitoring pCR to NACT in breast cancer.

Regulation of Bcl-2 Family Proteins in Estrogen Receptor-Positive Breast Cancer and Their Implications in Endocrine Therapy

Estrogen receptor (ER)-positive breast cancer accounts for around two-thirds of breast cancer occurrences, with endocrine therapy serving as first-line therapy in most cases. Targeting estrogen signaling pathways, which play a central role in regulating ER+ breast cell proliferation and survival, has proven to improve patient outcomes. However, despite the undeniable advantages of endocrine therapy, a subset of breast cancer patients develop acquired or intrinsic resistance to ER-targeting agents, limiting their efficacy. The activation of downstream ER signaling pathways upregulates pro-survival mechanisms that have been shown to influence the response of cells to endocrine therapy. The Bcl-2 family proteins play a central role in cell death regulation and have been shown to contribute to endocrine therapy resistance, supporting the survival of breast cancer cells and enhancing cell death evasion. Due to the overexpression of anti-apoptotic Bcl-2 proteins in ER-positive breast cancer, the role of these proteins as potential targets in hormone-responsive breast cancer is growing in interest. In particular, recent advances in the development of BH3 mimetics have enabled their evaluation in preclinical studies with ER+ breast cancer models, and BH3 mimetics have entered early ER+ breast cancer clinical trials. This review summarizes the molecular mechanisms underlying the regulation of Bcl-2 family proteins in ER+ breast cancer. Furthermore, an overview of recent advances in research regarding the efficacy of BH3 mimetics in ER+ breast cancer has been provided.

Prognostic value of circulating Bcl-2 and anti-p53 antibodies in patients with breast cancer: A long term follow-up (17.5 years)

BACKGROUND

Apoptosis inhibition is a major tumorigenic factor. Bcl-2 dysregulation and TP53 mutation status, which may correlate with autoantibody generation, contribute to impaired apoptosis.

OBJECTIVE

This study aimed to investigate the prognostic value of circulating Bcl-2 and anti-p53 antibodies (p53Abs) in a 17.5-year follow-up of breast cancer patients. We also analyzed the correlations of Bcl-2 and p53Abs with various clinicopathological parameters in order to assess their impact on tumor aggressiveness.

METHODS

Serum Bcl-2 and p53Abs levels were analyzed by the enzyme-linked immunosorbent assay (ELISA) in 82 patients with invasive breast cancer and twenty individuals without malignancy.

RESULTS

Serum Bcl-2 and p53Abs levels in breast cancer patients were significantly higher than those in controls. Patients with high levels of Bcl-2 (cut-off 200 U/ml) had a poorer prognosis (17.5-year survival) than those with lower Bcl-2 values. In combined analysis the subgroup of patients with elevated p53Abs (cut-off 15 U/ml) and elevated Bcl-2 (cut-offs 124 U/ml and 200 U/ml) had the worse prognosis in 17.5-year survival. In correlation analysis p53Abs and Bcl-2 were associated with unfavorable clinicopathological parameters.

CONCLUSIONS

Our results suggest that breast cancer patients with high serum levels of p53Abs and Bcl-2 present an especially unfavorable group in a long follow-up.

Coexpression of Smac/DIABLO and Estrogen Receptor in breast cancer

BACKGROUND

Smac/DIABLO is a proapoptotic protein deregulated in breast cancer, with a controversial role as a tumor marker, possibly due to a lack of correlative mRNA and protein analyses.

OBJECTIVE

To investigate the association of Smac/DIABLO gene and protein levels with clinical variables in breast cancer patients.

METHODS

Smac/DIABLO mRNA expression was analyzed by qPCR in 57 frozen tissues, whereas protein levels were assessed by immunohistochemistry in 82 paraffin-embedded tissues. Survivin mRNA levels were also measured. In vitro assays were performed to investigate possible regulators of Smac/DIABLO.

RESULTS

Higher levels of Smac/DIABLO mRNA and protein were found in estrogen receptor (ER)-positive samples (p= 0.0054 and p= 0.0043, respectively) in comparison to ER-negative tumors. A negligible positive association was found between Smac/DIABLO and survivin expression. In vitro assays showed that Smac/DIABLO is not regulated by ER and, conversely, it does not participate in ER expression modulation.

CONCLUSIONS

mRNA and protein levels of Smac/DIABLO were increased in ER-positive breast tumors in comparison with ER-negative samples, although the mechanism of this regulation is still unknown. Public databases showed a possible clinical relevance for this association.

Combined p53 and Bcl2 Immunophenotypes in Prognosis of Vietnamese Invasive Breast Carcinoma: A Single Institutional Retrospective Analysis

Background:

Aberrant of p53 and Bcl2 genes cause changes in the quantity and quality of their proteins and contribute to the pathogenesis of some cancer types including breast cancer. Expression of p53 and Bcl2 were associated to adverse clinical outcomes in breast cancer.

Purpose:

To predict the survival outcomes of invasive breast cancer in Vietnam, using immunohistochemical expression of p53, Bcl2 proteins.

Methods:

The current study was conducted on 526 breast cancer patients who had surgical operations, but had not received neo-adjuvant chemotherapy, from 2011 to 2014. The clinicopathological characteristics were recorded. Immunohistochemical staining was performed on p53, Bcl2 markers. Expression of p53 and Bcl2 were paired into different immunophenotypes for analysis with clinicopathological characteristics and survival. All breast cancer patients’ survival were analyzed by using Kaplan-Meier and Log-Rank models.

Results:

The presence of p53 protein was detected in 44.1%. Positive p53, and p53+Bcl2- immunophenotype were significantly associated with poorer prognostic features. In contrast, the positive Bcl2 protein accounted on 57.6%, and combination of p53-Bcl2+ were strong correlated with better clinicopathological parameters. Bcl2 positivity was observed in higher than the negative Bcl2 in the five-year OS (Overall survival) proportion (91.2 vs 79.4%, respectively) (p < 0.05). Multivariate analysis revealed that the expression of p53, Bcl2 or combinations of these 2 proteins was no longer remained as an independent prognostic variable.

Conclusion:

The Bcl2 positivity had a distinct OS and DFS (Disease free survival). The expression of p53 and Bcl2 are inversely correlated to clinical outcomes in breast cancer.

Bcl-2 expression and prognostic significance in feline invasive mammary carcinomas: a retrospective observational study

BACKGROUND

Cats spontaneously develop invasive mammary carcinomas with high clinical aggressiveness, and are considered relevant animal models for human breast cancer. Bcl-2 is an anti-apoptotic pro-survival protein, whose expression is associated with a favorable outcome in human breast cancer. The aim of our study was to determine the frequency of Bcl-2 expression in feline invasive mammary carcinomas (FMCs), its relationship with other clinicopathologic variables, and its prognostic value. This retrospective study included 180 FMCs, diagnosed in female cats treated by surgery only, with a 2-year follow-up post-mastectomy. Bcl-2, ER, PR, Ki-67, HER2, and CK5/6 expression were determined by automated immunohistochemistry. A receiver-operating-characteristic curve was used to set the threshold for Bcl-2 positivity.

RESULTS

The cohort comprises 32% (57/180) luminal FMCs defined by ER and/or PR positivity, and 68% (123/180) triple-negative FMCs (negative for ER, PR, and HER2). Bcl-2 expression was considered as positive when at least 65% of tumor cells were immunohistochemically stained. Thirty-one out of 180 FMCs (17%) were Bcl-2-positive. There was no significant association between Bcl-2 expression, and the tumor size, nodal stage, histological grade, or ER, PR, Ki-67, HER2, and CK5/6 expression. By multivariate survival analysis (Cox proportional-hazards regression), Bcl-2 positivity in FMCs was associated with longer disease-free interval (p = 0.005, HR = 0.38), overall survival (p = 0.028, HR = 0.61), and cancer-specific survival (p = 0.019, HR = 0.54) independently of other powerful prognostic factors such as pathologic tumor size, pathologic nodal stage, and distant metastasis. The positive prognostic value of Bcl-2 was confirmed in both luminal FMCs, of which 9/57 (16%) were Bcl-2-positive, and in basal-like triple-negative (ER-, PR-, HER2-, CK5/6+) FMCs, of which 14/76 (18%) were Bcl-2-positive.

CONCLUSIONS

Compared to human breast cancer, Bcl-2 positivity in feline invasive mammary carcinomas is also associated with better outcome, but is less common, and not associated with ER, PR, and HER2 expression. Cats with spontaneous Bcl-2-positive FMCs could be useful in preclinical trials evaluating anti-Bcl-2 strategies for chemoresistant luminal or triple-negative breast cancers.

Potential clinically useful prognostic biomarkers in triple-negative breast cancer: preliminary results of a retrospective analysis

Background

Triple-negative breast cancer (TNBC) has a poor prognosis, even in its early stages. In the absence of postoperative targeted treatments, intensive adjuvant chemotherapy regimens are proposed. For those favorable histologies, such as apocrine and adenoid cystic carcinoma, which frequently belong to TNBC, aggressive treatments are unnecessary.

Patients and methods

We retrospectively analyzed 631 cases of breast cancer, primary operated curatively, and followed up at our institution for at least 36 months to identify the bio-markers assessable by immunohistochemistry, to be proposed as prognostic score for tailoring adjuvant treatment to TNBC patients.

Results

The triple-negative phenotype was found in 85 patients (13.5%). Over a mean followup of 55.7 months, relapses occurred in 106 patients (16.8%), of which 18 (2.8%) were TNBC. Recurrence was directly correlated with Ki67 and cytokeratin 5/6 (CK5/6) immunoreactivity in all breast cancer patients (P=0.005), but only marginally with CK5/6 and epithelial cadherin (E-cad) expression in TNBC patients (P=0.07). Mean event-free survival (EFS) in TNBC patients was 85.52 months compared with 100.4 months in non-TNBC patients (P=0.228). The EFS of CK5/6-negative triple-negative patients was 68.84 months compared with 98.84 months in those who were CK5/6 positive (HR =5.08; P=0.038). EFS differed among patients identified as double-positive for E-cad and CK5/6 (83.87 months), those expressing E-cad or CK5/6 (64.23 months), and those negative for both biomarkers (39.64 months).

Conclusion

These preliminary results suggest that CK5/6 and E-cad are possible core biomarkers for a cost-effective prognostic evaluation of primary operable TNBC patients.

Bcl-2 antigen expression in luminal A and triple-negative breast cancer

Biomarkers for the prognosis of breast cancer have been routinely used in clinical practice, including the expression of hormone receptors, Ki-67 and HER-2. More recently, Bcl-2 has been recognized as an important prognostic factor in breast cancer, although controversies persist with respect to the significance of its expression. The aim of the present study was to evaluate Bcl-2 antigen expression in luminal A and triple-negative breast cancer. Sixty women with invasive ductal carcinoma were included in the study and divided into two groups: Group A (luminal A) and Group B (triple-negative), with 30 cases in each group. Immunohistochemistry was performed on tissue sections to evaluate Bcl-2 antigen expression. Fisher's exact test was used to compare the proportions of cases with cells expressing Bcl-2 between the two subtype cancer groups, with statistical significance being established at p < 0.05. The number of cases with cells expressing Bcl-2 in Groups A and B was 26 (86.7%) and 12 (40.0%), respectively (p < 0.0003). In the present study, the expression of the anti-apoptotic protein Bcl-2 was greater in luminal A breast cancer tissue samples compared to triple-negative breast cancer.

Alterations in estrogen signalling pathways upon acquisition of anthracycline resistance in breast tumor cells

Intrinsic or acquired drug resistance is a major impediment to the successful treatment of women with breast cancer using chemotherapy. We have observed that MCF-7 breast tumor cells selected for resistance to doxorubicin or epirubicin (MCF-7_DOX2 and MCF-7_EPI cells, respectively) exhibited increased expression of several members of the aldo-keto reductase (AKR) gene family (in particular AKR1C3 and AKR1B10) relative to control MCF-7_CC cells selected by propagation in the absence of drug. Normal cellular roles for the AKRs include the promotion of estrogen (E2) synthesis from estrone (E1) and the hydroxylation and detoxification of exogenous xenobiotics such as anthracycline chemotherapy drugs. While hydroxylation of anthracyclines strongly attenuates their cytotoxicity, it is unclear whether the enhanced AKR expression in the above anthracycline-resistant cells promotes E2 synthesis and/or alterations in E2 signalling pathways and whether such changes contribute to enhanced survival and anthracycline resistance. To determine the role of AKRs and E2 pathways in doxorubicin resistance, we examined changes in the expression of E2-related genes and proteins upon acquisition of doxorubicin resistance. We also assessed the effects of AKR overexpression or downregulation or the effects of activators or inhibitors of E2-dependent pathways on previously acquired resistance to doxorubicin. In this study we observed that the enhanced AKR expression upon acquisition of anthracycline resistance was, in fact, associated with enhanced E2 production. However, the expression of estrogen receptor α (ERα) was reduced by 2- to 5-fold at the gene transcript level and 2- to 20-fold at the protein level upon acquisition of anthracycline resistance. This was accompanied by an even stronger reduction in ERα phosphorylation and activity, including highly suppressed expression of two proteins under E2-dependent control (Bcl-2 and cyclin D1). The diminished Bcl-2 and cyclin D1 expression would be expected to reduce the growth rate of the cells, a hypothesis which was confirmed in subsequent cell proliferation experiments. AKR1C3 or AKR1B10 overexpression alone had no effect on doxorubicin sensitivity in MCF-7_CC cells, while siRNA-mediated knockdown of AKR1C3 and/or AKR1B10 expression had no significant effect on sensitivity to doxorubicin in MCF-7_DOX2 or MCF-7_EPI cells. This suggested that enhanced or reduced AKR expression/activity is insufficient to confer anthracycline resistance or sensitivity to breast tumor cells, respectively. Rather, it would appear that AKR overexpression acts in concert with other proteins to confer anthracycline resistance, including reduced E2-dependent expression of both an important apoptosis inhibitor (Bcl-2) and a key protein associated with activation of cell cycle-dependent kinases (cyclin D1).

Apoptosis, Chemoresistance, and Breast Cancer: Insights From the MCF-7 Cell Model System

The MCF-7 cell line was derived from a patient with metastatic breast cancer in 1970. Since then it has become a prominent model system for the study of estrogen receptor-positive breast cancer. With this model as a focus, this review summarizes important studies addressing tumor necrosis factor-α as a prototypical apoptosis-inducing cytokine in MCF-7 cells. Both survival and death receptor signaling pathways are discussed in terms of their role in chemotherapy-induced apoptosis as well as in chemoresistance. Novel therapeutic approaches to the treatment of breast cancer are proposed utilizing knowledge of these signaling pathways as targets. Specifically, ceramide metabolism is proposed as a novel target for chemosensitivity, perhaps combined with selective inhibitors of Bcl-2 or PI3K/Akt/nuclear factor-κB. Suggested areas of future research include translational studies manipulating candidate survival and death signaling pathways.

BCL2 as a Subtype-Specific Prognostic Marker for Breast Cancer

PURPOSE

B-cell lymphoma 2 (BCL2) is an antiapoptosis protein and an important clinical breast cancer prognostic marker. As the role of BCL2 is dependent on the estrogen receptor (ER) status, this effect might differ according to molecular subtypes. The aim of this study was to evaluate the relationship between the prognostic outcomes and BCL2 expression among the molecular subtypes.

METHODS

We retrieved the data of 1,356 patients who were newly diagnosed with malignant breast cancer between November 2006 and November 2011. Immunohistochemistry was used to measure ER, progesterone receptor, human epidermal growth factor receptor 2 (HER2), Ki-67, and BCL2 expression. We classified breast cancer into five molecular subtypes based on the 13th St. Gallen International Expert Consensus, including luminal A, luminal B (HER2-negative), luminal B (HER2-positive), HER2-overexpression, and triple-negative subtypes. We analyzed the clinicopathological features and assessed the correlation between BCL2 expression and clinical outcomes, such as relapse-free survival (RFS) and disease-specific survival (DSS) according to the five molecular subtypes.

RESULTS

A total of 605 cases of breast cancer (53.8%) showed BCL2 expression. BCL2-positive expression was associated with young age (<50 years, p=0.036), lower histological grade (p<0.001), low Ki-67 level (<14%, p<0.001), hormone receptor positivity (p<0.001), HER2 negativity (p<0.001), luminal breast cancer (p<0.001), and low recurrence rate (p=0.016). BCL2-positive expression was also associated with favorable 5-year RFS (p=0.008, 91.4%) and DSS (p=0.036, 95.6%) in all the patients. BCL2-positive expression in luminal A breast cancer resulted in significantly favorable 5-year RFS and DSS (p=0.023 and p=0.041, respectively). However, BCL2 expression was not associated with the prognosis in the other subtypes.

CONCLUSION

The prognostic role of BCL2 expression in breast cancer is subtype-specific. BCL2 expression differs according to the molecular subtype and is a good prognostic marker for only luminal A breast cancer.

Coadministrating luteolin minimizes the side effects of the aromatase inhibitor letrozole

Aromatase inhibitors (AIs) have been used as adjuvant therapeutic agents for breast cancer. Their adverse side effect on blood lipid is well documented. Some natural compounds have been shown to be potential AIs. In the present study, we compared the efficacy of the flavonoid luteolin to the clinically approved AI letrozole (Femara; Novartis Pharmaceuticals, East Hanover, NJ) in a cell and a mouse model. In the in vitro experimental results for aromatase inhibition, the Ki values of luteolin and letrozole were estimated to be 2.44 µM and 0.41 nM, respectively. Both letrozole and luteolin appeared to be competitive inhibitors. Subsequently, an animal model was used for the comparison. Aromatase-expressing MCF-7 cells were transplanted into ovariectomized athymic mice. Luteolin was given by mouth at 5, 20, and 50 mg/kg, whereas letrozole was administered by intravenous injection. Similar to letrozole, luteolin administration reduced plasma estrogen concentrations and suppressed the xenograft proliferation. The regulation of cell cycle and apoptotic proteins-such as a decrease in the expression of Bcl-xL, cyclin-A/D1/E, CDK2/4, and increase in that of Bax-was about the same in both treatments. The most significant disparity was on blood lipids. In contrast to letrozole, luteolin increased fasting plasma high-density lipoprotein concentrations and produced a desirable blood lipid profile. These results suggested that the flavonoid could be a coadjuvant therapeutic agent without impairing the action of AIs.

Significance of immunohistochemistry in breast cancer

The biological characteristics of the tumour are used to estimate prognosis and select appropriate systemic therapy for patients with (breast) cancer. The advent of molecular technology has incorporated new biomarkers along with immunohistochemical and serum biomarkers. Immunohistochemical markers are often used to guide treatment decisions, to classify breast cancer into subtypes that are biologically distinct and behave differently, and both as prognostic and predictive factors. Steroid hormone receptors, markers of tumour proliferation, and factors involved in angiogenesis and apoptosis are of scientific interest. In this review we will provide information on the immunohistochemical markers used in the management of breast cancer patients using available data from the literature. We consider the utility of established immunohistochemical markers, and discuss the challenges involved in integrating novel molecular markers into clinical practice.

Significance of immunohistochemistry in breast cancer

The biological characteristics of the tumour are used to estimate prognosis and select appropriate systemic therapy for patients with (breast) cancer. The advent of molecular technology has incorporated new biomarkers along with immunohistochemical and serum biomarkers. Immunohistochemical markers are often used to guide treatment decisions, to classify breast cancer into subtypes that are biologically distinct and behave differently, and both as prognostic and predictive factors. Steroid hormone receptors, markers of tumour proliferation, and factors involved in angiogenesis and apoptosis are of scientific interest. In this review we will provide information on the immunohistochemical markers used in the management of breast cancer patients using available data from the literature. We consider the utility of established immunohistochemical markers, and discuss the challenges involved in integrating novel molecular markers into clinical practice.

A BCL2 promoter polymorphism rs2279115 is not associated with BCL2 protein expression or patient survival in breast cancer patients

The B-cell CLL/lymphoma 2 (BCL2) gene family encodes pro- and anti-apoptotic proteins that are critical regulators of programmed cell death. Higher levels of BCL2 expression in breast tumours have been shown to be an independent prognostic factor for improved survival from breast cancer. The promoter single nucleotide polymorphism (SNP) rs2279115 has been associated with both BCL2 expression and patient survival. The aim of this study was to attempt to replicate these observations in a cohort of 1015 UK women with breast cancer, and to compare genotype frequencies in cases and controls. In this study, 1015 breast cancer cases and 1034 control subjects were genotyped for the rs2279115 SNP by 5’ nuclease PCR. Paraffin embedded tumour tissue for 342 case subjects was assembled into tissue microarrays, and the level of expression of BCL2 was established by immunohistochemistry. Kaplan Meier survival curves and Cox Proportional Hazards models were used to examine the effect of genotype on patient survival. The effect of SNP genotype on tumour BCL2 protein levels and breast cancer susceptibility was assessed by logistic regression. In this study higher BCL2 expression was significantly associated with improved survival from breast cancer (p = 0.015), in keeping with previous reports. The SNP rs2279115 was not found to be associated with tumour expression of BCL2, (p = 0.77), and neither was it associated with case/control status (p = 0.25). There was no significant association between the SNP and overall survival (p = 0.75). In conclusion, we found that higher tumour BCL2 expression is associated with improved survival from breast cancer, in keeping with previous studies. However, in contrast to a previous report, the promoter SNP rs2279115 was not associated with BCL2 expression or overall survival from breast cancer.

The citrus flavonone hesperetin inhibits growth of aromatase-expressing MCF-7 tumor in ovariectomized athymic mice

Aromatase is responsible for the rate-determining reaction in estrogen synthesis and is a prime target for treating estrogen-receptor-positive breast cancer. Previous in vitro study has demonstrated that apigenin (APG), naringenin (NGN) and hesperetin (HSP) are three of the most potent natural aromatase inhibitors. Because the enzyme inhibition could potentially block breast cancer development, we employed an established postmenopausal breast cancer model to examine the chemopreventive effect of these flavonoids in vivo. Athymic mice were ovariectomized and transplanted with aromatase-overexpressing MCF-7 cells. Dietary administration of HSP at 1000 ppm and 5000 ppm significantly deterred the xenograft growth, while a null effect was observed in mice treated with APG or NGN. Further study illustrated that plasma estrogen in HSP-treated mice was reduced. Messenger RNA expression of the estrogen-responsive gene pS2 was also decreased in the tumors of mice treated with 1000 and 5000 ppm HSP. On the other hand, western analysis indicated that cyclin D1, CDK4 and Bcl-x(L) were reduced in the tumors. This study suggested that HSP could be a potential chemopreventive agent against breast carcinogenesis through aromatase inhibition.

Prognostic significance of Bcl-2 in invasive mammary carcinomas: a comparative clinicopathologic study between "triple-negative" and non-"triple-negative" tumors

Bcl-2 is a tumorigenic protein that is expressed in 25% to 50% of breast cancers. Although its expression has been widely accepted as a favorable prognostic marker, its protective mechanism of action remains unclear. "Triple-negative" tumors are an aggressive subgroup known to carry a poor prognosis. Studies documenting prognostic significance of Bcl-2 expression in triple-negative in comparison to non-triple-negative breast cancers are limited. Bcl-2 expression was correlated with tumor size, grade, histologic type, lymphovascular invasion, lymph node status, patients' overall survival, estrogen receptor, progesterone receptor, Her-2, p53, and epidermal growth factor receptor in 124 triple-negative and 458 non-triple-negative tumors. There were significant differences between triple-negative and non-triple-negative tumors in their relationship to Bcl-2 expression (81% versus 29%, respectively) and tumor aggression. As previously reported, in non-triple-negative tumors, Bcl-2 positivity correlated with less aggressive tumors (94% of grade I tumors were Bcl-2+ versus 62% of grade III tumors, P < .011) and overall survival (P = .008). However, the opposite was true in patients with triple-negative tumors, where Bcl-2 positivity was associated with poorer survival (P = .64). In triple-negative tumors, Bcl-2 positivity was not associated with any of the aforementioned parameters except for a lower incidence of lymph node metastasis. Moreover, by Cox regression analysis of all variables, in patients with triple-negative tumors, lymphovascular invasion (P = .009) and Bcl-2 expression (P = .028) were predictors of poor survival. In conclusion, there are major clinicopathologic differences between breast cancer phenotypes. Our results establish the value of using Bcl-2 in prognostic stratification of patients and its potential therapeutic implications in selecting patients for treatment.

ERα and ERβ expression in correlation with Ki-67, Bcl-2 and Bak in primary tumors and lymph node metastases of breast cancer: The effect of pre-operative chemotherapy

This study aimed to assess the pre-operative chemotherapy impact on the relationship between estrogen receptor (ER) expression and markers of proliferation and apoptosis in primary and metastatic breast cancer. Immunohistochemical examinations were conducted on surgically removed ductal invasive breast cancers and their lymph node metastases in 135 patients. A total of 64 patients from this group underwent pre-operative chemotherapy and in 71 cases the surgery was performed without primary chemotherapy. A negative correlation between ERα and Ki-67 was found in primary tumors and lymph node metastases. A positive correlation was observed between ERα and Bcl-2. A positive correlation was also noted between ERβ and Bak, suggesting that the two ERs were involved in the regulation of proteins responsible for the control of the apoptotic process. Assessment of the expression of the proteins conducted separately in primary tumors and lymph node metastases did not reveal a significant effect of pre-operative chemotherapy on the correlations of ERs with Ki-67, Bcl-2 and Bak. However, the analysis of the correlations between the receptor expression in primary tumors and Ki-67, Bcl-2 and Bak in lymph node metastases showed a statistically significant impact of pre-operative chemotherapy on the correlations of ERα and Bcl-2 with ERβ and Bak, confirming involvement of the two ERs in the regulation of apoptosis during breast carcinogenesis.

BCL2 in breast cancer: a favourable prognostic marker across molecular subtypes and independent of adjuvant therapy received

BACKGROUND

Breast cancer is heterogeneous and the existing prognostic classifiers are limited in accuracy, leading to unnecessary treatment of numerous women. B-cell lymphoma 2 (BCL2), an antiapoptotic protein, has been proposed as a prognostic marker, but this effect is considered to relate to oestrogen receptor (ER) status. This study aimed to test the clinical validity of BCL2 as an independent prognostic marker.

METHODS

Five studies of 11 212 women with early-stage breast cancer were analysed. Individual patient data included tumour size, grade, lymph node status, endocrine therapy, chemotherapy and mortality. BCL2, ER, progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) levels were determined in all tumours. A Cox model incorporating the time-dependent effects of each variable was used to explore the prognostic significance of BCL2.

RESULTS

In univariate analysis, ER, PR and BCL2 positivity was associated with improved survival and HER2 positivity with inferior survival. For ER and PR this effect was time dependent, whereas for BCL2 and HER2 the effect persisted over time. In multivariate analysis, BCL2 positivity retained independent prognostic significance (hazard ratio (HR) 0.76, 95% confidence interval (CI) 0.66-0.88, P<0.001). BCL2 was a powerful prognostic marker in ER- (HR 0.63, 95% CI 0.54-0.74, P<0.001) and ER+ disease (HR 0.56, 95% CI 0.48-0.65, P<0.001), and in HER2- (HR 0.55, 95% CI 0.49-0.61, P<0.001) and HER2+ disease (HR 0.70, 95% CI 0.57-0.85, P<0.001), irrespective of the type of adjuvant therapy received. Addition of BCL2 to the Adjuvant! Online prognostic model, for a subset of cases with a 10-year follow-up, improved the survival prediction (P=0.0039).

CONCLUSIONS

BCL2 is an independent indicator of favourable prognosis for all types of early-stage breast cancer. This study establishes the rationale for introduction of BCL2 immunohistochemistry to improve prognostic stratification. Further work is now needed to ascertain the exact way to apply BCL2 testing for risk stratification and to standardise BCL2 immunohistochemistry for this application.

Correlation of GREB1 mRNA with protein expression in breast cancer: validation of a novel GREB1 monoclonal antibody

Studies of gene regulated by estrogen in breast cancer 1 (GREB1) have focused on mRNA levels with limited evidence about GREB1 protein expression in normal and breast cancer cells. A monoclonal antibody that recognizes GREB1 protein in breast tissues could be applied to correlate protein expression with established mRNA expression data. A hybridoma expressing a murine monoclonal antibody targeting a 119 amino acid peptide specific to human GREB1 was generated. The novel monoclonal GREB1 antibody (GREB1ab) was validated for use in Western blotting as well as immunohistochemical (IHC) applications. GREB1ab detects a 216 kDa protein corresponding to GREB1 in estrogen receptor alpha (ERalpha+) breast cancer cells as well as ERalpha- breast cancer cells transduced with a GREB1 expression vector. GREB1ab specificity was verified using an ERalpha antagonist to prevent GREB1 induction as well as a silencing siRNA targeting GREB1 mRNA. GREB1ab was further validated for detection of GREB1 by IHC in breast cancer cell lines and breast tissue microarrays (TMA). ERalpha+ cell lines were observed to express GREB1 while ERalpha- cell lines did not express detectable levels of the protein. Using breast cancer tissue whole sections, IHC with the GREB1ab identified protein expression in ERalpha+ breast cancer tissue as well as normal breast tissue, with little GREB1 expression in ERalpha- breast cancer tissue. Furthermore, these data indicate that GREB1 mRNA expression correlates well with protein expression. The novel monoclonal GREB1ab is specific for GREB1 protein. This antibody will serve as a tool for investigations focused on the expression, distribution, and function of GREB1 in normal breast and breast cancer tissues.

The soy isoflavone genistein induces estrogen synthesis in an extragonadal pathway

Genistein is a phytoestrogen isolated from soyabean, and is a potential nutraceutical gearing for women suffering from perimenopausal symptoms. Because of its differential binding affinity to estrogen receptor (ER) isoforms, genistein is described as a selective estrogen receptor modulator (SERM). The ligand-receptor interaction is established, but the potential confounding factors have not been fully addressed. Alteration in estrogen metabolism is an important issue when determining the downstream effect of ER. Aromatase or CYP19 catalyzes the rate-limiting reaction of estrogen synthesis, and is highly expressed in the ovary. This organ is the source of estrogen in females. After menopause the ovaries cease to produce the hormone, and localized estrogen synthesis in extragonadal tissues could become physiologically significant. In the present study, effect of genistein on CYP19 regulation was investigated in the hepatic cells HepG2. The phytoestrogen induced aromatase activity in the cells. Increased mRNA expression with concurrent elevation in the usage of promoters I.3/II was also demonstrated. Luciferase reporter gene assays verified the transcriptional control dictated by the specific promoters under genistein treatment. Several protein kinases were examined, and PKC?, P38, ERK-1/2 appeared to be activated. Subsequent inhibition and expression experiments demonstrated the involvement of these kinases. The transcriptional factor CREB was ultimately activated in the gene regulation. The present study illustrated an extragonadal pathway by which genistein might increase estrogen synthesis.

Dietary administration of the licorice flavonoid isoliquiritigenin deters the growth of MCF-7 cells overexpressing aromatase

Licorice is the sweet-tasting rhizomes of a bean plant and is quite commonly used in Western countries for culinary purposes, while it is a medicinal herb in China. Many flavonoids have been isolated from licorice, and their pharmacological properties may be applicable in preventive medicine. Overexposure to estrogen has been implicated in the etiology of breast cancer, and cytochrome P450 (CYP) 19 enzyme, or aromatase, catalyzes the rate-limiting reaction. Phytocompounds that are able to inhibit this enzyme may potentially suppress breast cancer development. In the present study the licorice flavonoid isoliquiritigenin (ILN) was shown to be an aromatase inhibitor in recombinant protein and MCF-7 cells stably transfected with CYP19 (MCF-7aro). ILN displayed a K(i) value of around 3 muM, and it also blocked the MCF-7aro cell growth pertaining to the enzyme activity in vitro. Subsequently, the compound administered in diet was given to ovariectomized athymic mice transplanted with MCF-7aro cells. This mouse model is widely accepted for studying postmenopausal breast cancer. The phytochemical significantly deterred the xenograft growth without affecting the body weight. Subsequently, the flavonoid's effect on CYP19 transcriptional control in vitro was also investigated. At the mRNA level, ILN could also suppress the expression in wild-type MCF-7 cells. Reporter gene assay and real-time PCR verified that the transactivity of CYP19 driven by promoters I.3 and II was suppressed in these cells. Deactivation of C/EBP could be the underlying molecular mechanism. Our study demonstrated that ILN was an inhibitor of aromatase and a potential chemopreventive agent against breast cancer.

A candidate molecular signature associated with tamoxifen failure in primary breast cancer

Introduction

Few markers are available that can predict response to tamoxifen treatment in estrogen receptor (ER)-positive breast cancers. Identification of such markers would be clinically useful. We attempted to identify molecular markers associated with tamoxifen failure in breast cancer.

Methods

Eighteen initially ER-positive patients treated with tamoxifen requiring salvage surgery (tamoxifen failure [TF] patients) were compared with 17 patients who were disease free 5 years after surgery plus tamoxifen adjuvant therapy (control patients). cDNA microarray, real-time quantitative PCR, and immunohistochemistry on tissue microarrays were used to generate and confirm a gene signature associated with tamoxifen failure. An independent series of 33 breast tumor samples from patients who relapsed (n = 14) or did not relapse (n = 19) under tamoxifen treatment from a different geographic location was subsequently used to explore the gene expression signature identified.

Results

Using a screening set of 18 tumor samples (from eight control patients and 10 TF patients), a 47-gene signature discriminating between TF and control samples was identified using cDNA arrays. In addition to ESR1/ERα, the top-ranked genes selected by statistical cross-analyses were MET, FOS, SNCG, IGFBP4, and BCL2, which were subsequently validated in a larger set of tumor samples (from 17 control patients and 18 TF patients). Confirmation at the protein level by tissue microarray immunohistochemistry was observed for ER-α, γ-synuclein, and insulin-like growth factor binding protein 4 proteins in the 35 original samples. In an independent series of breast tumor samples (19 nonrelapsing and 14 relapsing), reduced expression of ESR1/ERα, IGFBP4, SNCG, BCL2, and FOS was observed in the relapsing group and was associated with a shorter overall survival. Low mRNA expression levels of ESR1/ERα, BCL2, and FOS were also associated with a shorter relapse-free survival (RFS). Using a Cox multivariate regression analysis, we identified BCL2 and FOS as independent prognostic markers associated with RFS. Finally, the BCL2/FOS signature was demonstrated to have more accurate prognostic value for RFS than ESR1/ERα alone (likelihood ratio test).

Conclusions

We identified molecular markers including a BCL2/FOS signature associated with tamoxifen failure; these markers may have clinical potential in the management of ER-positive breast cancer.

Enhanced micronucleus formation and modulation of BCL-2:BAX in MCF-7 cells after exposure to binary mixtures

BACKGROUND

Within mixtures, interactions between different xenobiotics may occur to give rise to additive, synergistic, inhibitory and/or stimulatory effects in target cells. The role that xenobiotics individually or in mixtures, and at environmental concentrations, play in the etiology of common human diseases often remains obscure.

METHODS

In the presence or absence of lindane, chromosomal aberrations were detected in MCF-7 cells after 24-hr treatment with benzo[a]pyrene (B[a]P) or 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) using the cytokinesis-block micronucleus assay. Micronuclei were scored in 1,000 binucleate cells/treatment. We investigated intracellular responses using quantitative gene expression analyses of cyclin-dependent kinase inhibitor 1A [CDKN1A (P21(WAF1/CIP1))], B-cell leukemia/lymphoma 2 (BCL-2), BCL-2-associated X (BAX), and isoforms of cytochrome P450 (CYP), CYP1A1, CYP1A2, and CYP1B1. Immunocytochemical analyses of p53, p21(Waf1/Cip1), Bcl-2 and Bax protein expression in MCF-7 cells were also carried out.

RESULTS

After exposure to binary mixtures of B[a]P plus lindane or PhIP plus lindane, a 10-fold increase in micronucleus formation resulted; these test agents individually induced 2- to 5-fold increases. Lindane increased the ratio of Bcl-2:Bax, as did 17beta-estradiol (E(2)). Although treatment with B[a]P alone was found to elevate expression of P21(WAF1/CIP1)and CYP isoenzymes, it reduced the ratio of BCL-2:BAX mRNA transcripts. Treatment with a binary mixture of 10(-8) M B[a]P plus 10(-12) M lindane or 10(-10) M E(2) reversed B[a]P-induced reductions in the ratio of Bcl-2- to Bax-positive cells. In contrast, treatments with PhIP (known to possess hormonelike properties) plus lindane or E(2) resulted in profound reductions in Bcl-2:Bax ratio.

CONCLUSIONS

Our results suggest that low-dose treatments (i.e., close to environmental levels) may increase DNA damage while influencing survival in exposed cells and that these effects may depend on the endocrine activity of test agents.

The red clover (Trifolium pratense) isoflavone biochanin A inhibits aromatase activity and expression

Biochanin A is an isoflavone isolated from red clover (Trifolium pratense), and is a commercially available nutraceutical for women suffering from postmenopausal symptoms. Isoflavones resemble the structure of oestrogen, and display agonistic and antagonistic interactions with the oestrogen receptor. Overexposure of oestrogen is a major contributing factor in the development of breast cancer, and cytochrome P450 (CYP) 19 enzyme, or aromatase, catalyses the reaction converting androgen to oestrogen. In the present study the effect of biochanin A on the gene regulation and enzyme activity of aromatase was investigated. By assaying MCF-7 cells stably transfected with CYP19, biochanin A inhibited aromatase activity and hampered cell growth attributing to the enzyme activity. In addition, 25 microm-biochanin A significantly reduced CYP19 mRNA abundance in the oestrogen receptor-negative breast cancer cells SK-BR-3. The transcriptional control of the CYP19 gene is exon-specific, and promoter regions I.3 and II have been shown to be responsible for CYP19 expression in SK-BR-3 cells. Luciferase reporter gene assays also revealed that biochanin A could repress the transcriptional control dictated by the promoter regulation. Interestingly, genistein did not inhibit aromatase but it might down regulate promoter I.3 and II transactivation. Since genistein is a major metabolite of biochanin A, it might contribute to biochanin A's suppressive effect on CYP19 expression. The present study illustrated that biochanin A inhibited CYP19 activity and gene expression.

Tamoxifen-induced rapid death of MCF-7 breast cancer cells is mediated via extracellularly signal-regulated kinase signaling and can be abrogated by estrogen

Tamoxifen (Tam) is widely used in chemotherapy of breast cancer. It inhibits proliferation and induces apoptosis of breast cancer cells by estrogen receptor (ER)-dependent modulation of gene expression. In addition, recent reports have shown that Tam also has nongenomic effects. We previously reported induction of a rapid mitochondrial death program in breast cancer cells at pharmacological concentrations of Tam. Here we studied the upstream signaling events leading to mitochondrial disruption by Tam. We observed that 5 mum Tam rapidly induced sustained activation of ERK1/2 in ER-positive breast cancer cell lines (MCF-7 and T47D) and that PD98059 (inhibitor of ERK activation) was able to protect MCF-7 cells against Tam-induced death. These data suggest that activation of ERK has a primary role in the acute death response of the cells. In addition, inhibition of epidermal growth factor receptor (EGFR) opposed both Tam-induced ERK1/2 phosphorylation and cell death, which suggests that EGFR-associated mechanisms are involved in Tam-induced death. ERK1/2 phosphorylation was associated with a prolonged nuclear localization of ERK1/2 as determined by fluorescence microscopy with ERK2-green fluorescent protein construct. 17beta-Estradiol was shown to exert a different kind of temporal pattern of ERK nuclear localization in comparison with Tam. Moreover, 17beta-estradiol was found to oppose the rapid effects of Tam in MCF-7 and T47D cells but not in MDA-MB-231 cells, which implies a role for estrogen receptors in the protective effect of estrogen. The pure antiestrogen ICI182780 could not, however, prevent Tam-induced ERK1/2 phosphorylation, suggesting that the Tam-induced rapid cell death is primarily ER-independent or mediated by ICI182780 insensitive nongenomic mechanisms.

Apoptosis and differentiation of human embryonic stem cells induced by sustained activation of c-Myc

Embryonic stem (ES) cells are self-renewing, pluripotent cell lines, characterized by their potential to differentiate into all cell types. The proto-oncogene product c-Myc has a crucial role in the self-renewal of mouse ES (mES) cells, but its role in human ES (hES) cells is unknown. To investigate c-Myc functions in hES cells, we expressed an inducible c-Myc fused to the hormone-binding domain of the estrogen receptor (c-MycER) protein that is activated by 4-hydroxy-tamoxifen. In contrast to its role in mES cells, activation of c-MycER in hES cells induced apoptosis and differentiation into extraembryonic endoderm and trophectoderm lineages concomitant with reduced expression of the pluripotent markers Oct4 and Nanog. Neither inhibition of caspase activity nor knockdown of p53 by RNA interference impaired the induction of differentiation markers induced by c-Myc activation. In addition, differentiation induced by c-Myc activation was associated with downregulation of alpha6 integrin expression, suggesting an important role for the integrin/extracellular matrix interaction in the regulation of ES cell behavior. None of these effects occurred with deletion of the c-Myc transactivation domain, indicating that c-Myc promotes both apoptosis and differentiation in a transcriptional activity-dependent manner. Together, our results provide new insights into the c-Myc functions regulating hES cell fate.

Role of androgens on MCF-7 breast cancer cell growth and on the inhibitory effect of letrozole

Previous work has shown that androgens inhibit breast cancer cells and tumor growth. On the other hand, androgens can be converted to mitogenic estrogens by aromatase in breast cancer cells. Here, we report that androgens, such as the aromatizable androstenedione and the non-aromatizable 5alpha-dihydrotestosterone, inhibit MCF-7 cell proliferation. This effect is observed only in the absence or at a low concentration of estrogens and is evident in cells with low aromatase activity. Growth of a new aromatase stably transfected MCF-7 cell line (Ac1) was stimulated by conversion of androstenedione into estrogens and was sensitive to aromatase inhibitors. We show that blockade of the androgen receptor (AR) in these cells by the antiandrogen casodex or by the anti-AR small interfering RNA inhibited the antiproliferative effect of dihydrotestosterone and letrozole (aromatase inhibitor). We also show that suppression of the estrogen-induced antiapoptotic protein Bcl-2 may be involved in the antiproliferative effects of androgens and letrozole. These effects can be reversed by casodex. In conclusion, the results suggest that aromatase inhibitors may exert their antiproliferative effect not only by reducing the intracellular production of estrogens but also by unmasking the inhibitory effect of androgens acting via the AR.

The red wine polyphenol resveratrol displays bilevel inhibition on aromatase in breast cancer cells

Estrogen plays a crucial role in the development of breast cancer, and the inhibition of estrogen synthesis has been an important target for the prevention and treatment of this disease. The rate-limiting reaction of the hormone biosynthesis is catalyzed by cytochrome P450 (CYP) 19 enzyme or aromatase. It has been of genuine interest to uncover an aromatase-inhibitory compound from a dietary source. Resveratrol is a polyphenolic compound that can be isolated from grape peel. Because of its structural resemblance to estrogen, resveratrol's agonistic and antagonistic properties on estrogen receptor have been examined and demonstrated. In the present study, the effect of resveratrol on the expression and enzyme activity of aromatase was investigated. By assaying on MCF-7 cells stably transfected with CYP19 (MCF-7aro cells), resveratrol inhibited the aromatase activity with an IC(50) value of 25 microM. Kinetic analysis indicated that both competitive and noncompetitive inhibition might be involved. The administration of 10 nmol/l testosterone-a substrate of aromatase-produced a 50% increase in the MCF-7aro cell number. This cell proliferation specifically induced by testosterone was significantly reduced by 10 microM resveratrol. In addition, 50 microM resveratrol significantly reduced the CYP19-encoding mRNA abundance in SK-BR-3 cells. The transcriptional control of CYP19 gene is tissue specific, and promoter regions I.3 and II have previously been shown to be responsible for CYP19 expression in breast cancer cells. Luciferase reporter gene assays revealed that resveratrol could repress the transcriptional control dictated by the promoter regulation. The present study illustrated that pharmacological dosage of resveratrol inhibited aromatase at both the enzyme and mRNA levels.

Estrogen receptors alfa (ERalpha) and beta (ERbeta) differentially regulate proliferation and apoptosis of the normal murine mammary epithelial cell line HC11

The mitogenic effect of 17beta-estradiol (E2) on the breast is mediated by estrogen receptor alfa (ERalpha), hence ERalpha antagonists are effective in the treatment of breast cancer. The possible use of estrogen receptor beta (ERbeta) as a target in treatment of breast cancer is under investigation. The mouse mammary cell line HC11 expresses both ERs and was used to study the role of the two receptors in proliferation. E2 had no effect on proliferation. The ERalpha-selective agonist 4,4',4''-(4-propyl-(1H)-pyrazole-1,3,5-triyl)trisphenol (PPT) stimulated proliferation. The ERbeta-selective agonist 2,3-bis(4-hydroxy-phenyl)-propionitrile (DPN) inhibited cell growth and induced apoptosis. PPT upregulated while DPN downregulated cyclin D1 and proliferating cell nuclear antigen (PCNA). Upon inhibition of ERalpha expression with RNA interference, E2 caused a decrease in cyclin D1 and PCNA, and increased apoptosis. When ERbeta expression was blocked, E2 induced proliferation and cells gained the capacity to grow in soft agar. In summary, in HC11 mammary epithelial cells, ERalpha drives proliferation in response to E2 while ERbeta is growth inhibitory. The lack of effect of E2 on HC11 cell growth is the result of the combined actions of ERalpha (proliferation) and ERbeta (apoptosis). We suggest that use of ERbeta agonists will be a useful addition in treatment of breast cancer, which, at present, is only aimed at inhibition of ERalpha.

Induction of thyroid papillary carcinoma cell proliferation by estrogen is associated with an altered expression of Bcl-xL

PURPOSE

One of the features of thyroid carcinoma is its predilection for women of reproductive age relative to men. An increased risk has also been documented in women who have used estrogens for gynecologic reasons. The aim of this study was to explore the mechanism by which sex hormones contribute to the development of thyroid carcinoma, which is not well understood at present.

MATERIALS AND METHODS

In this study, we investigated the effects of estradiol and testosterone on cell proliferation in a human thyroid papillary carcinoma cell line (KAT5) by MTT assay. We also studied the expression of estrogen receptors and the levels of anti-apoptotic Bcl-xL protein, pro-apoptotic Bax protein, and messenger RNA in the cells by Western blot and reverse transcriptase polymerase chain reaction analysis.

RESULTS

The results showed that estradiol promotes cell proliferation when compared with cells treated with testosterone and untreated cells, and that the growth-promoting effect of estradiol was attenuated by tamoxifen. The expression of Bcl-xL was markedly increased in a dose-dependent manner, resulting in an elevated ratio of Bcl-xL to Bax.

DISCUSSION

We conclude that estradiol promotes KAT5 cell proliferation and that the underlying mechanism may be associated with up-regulation of Bcl-xL expression. The data provide insight into the molecular mechanism underlying the epidemiologic data that shows a two- to threefold increased prevalence of thyroid carcinoma in women relative to men. From the therapeutic point of view, the finding that estradiol enhances anti-apoptotic signaling pathways may be significant in the search for novel prevention and treatment strategies of thyroid carcinomas.

Opposite effects of estrogen receptors alpha and beta on MCF-7 sensitivity to the cytotoxic action of TNF and p53 activity

We have investigated the effect of estrogen on p53 cellular location and its influence on tumor cell susceptibility to tumor necrosis factor (TNF)-mediated cytotoxic action. For this purpose, we have used the TNF-sensitive human breast adenocarcinoma MCF-7 and its derivative, the TNF-resistant 1001 clone. Our data indicate that although estrogen receptor (ER)alpha is present in both cell lines, estrogen treatment (1x10(-8) M) has an influence only on the MCF-7 cells and protects these cells from the TNF cytotoxicity. This protective effect is associated with translocation of p53 from the nucleus to the cytoplasm in p53 wild-type MCF-7 and not in p53-mutated 1001 cells. The translocation of p53 in MCF-7 cells results in a decrease in its transcriptional activity, as revealed by diminished p21(WAF1/CIP1) induction and an altered ratio of Bax and Bcl-2 proteins. The estrogen-induced effects are reversed by the selective estrogen inhibitor 182, 780 (1x10(-6) M). Interestingly, transient transfection of MCF-7 cells with ERbeta but not ERalpha cDNA encoding plasmid results in retention of p53 in the nucleus, a subsequent potentiation of its transcriptional activity, and in an increased MCF-7 sensitivity to TNF. The estrogen effects on p53 location and transcriptional activity may involve the mdm2 protein since both events were reversed following MCF-7 transfection with plasmid encoding the ARF cDNA. These studies suggest that estrogen-induced MCF-7 cell survival in the presence of TNF requires a transcriptionally active p53 and, more importantly, indicate that introduction of ERbeta can attenuate the estrogen effects on the p53 protein location, its transcriptional activity and also results in a potentiation of cell sensitivity to TNF-mediated cell death.

Estradiol abrogates apoptosis in breast cancer cells through inactivation of BAD: Ras-dependent nongenomic pathways requiring signaling through ERK and Akt

Estrogens such as 17-beta estradiol (E(2)) play a critical role in sporadic breast cancer progression and decrease apoptosis in breast cancer cells. Our studies using estrogen receptor-positive MCF7 cells show that E(2) abrogates apoptosis possibly through phosphorylation/inactivation of the proapoptotic protein BAD, which was rapidly phosphorylated at S112 and S136. Inhibition of BAD protein expression with specific antisense oligonucleotides reduced the effectiveness of tumor necrosis factor-alpha, H(2)O(2), and serum starvation in causing apoptosis. Furthermore, the ability of E(2) to prevent tumor necrosis factor-alpha-induced apoptosis was blocked by overexpression of the BAD S112A/S136A mutant but not the wild-type BAD. BAD S112A/S136A, which lacks phosphorylation sites for p90(RSK1) and Akt, was not phosphorylated in response to E(2) in vitro(.) E(2) treatment rapidly activated phosphatidylinositol 3-kinase (PI-3K)/Akt and p90(RSK1) to an extent similar to insulin-like growth factor-1 treatment. In agreement with p90(RSK1) activation, E(2) also rapidly activated extracellular signal-regulated kinase, and this activity was down-regulated by chemical and biological inhibition of PI-3K suggestive of cross talk between signaling pathways responding to E(2). Dominant negative Ras blocked E(2)-induced BAD phosphorylation and the Raf-activator RasV12T35S induced BAD phosphorylation as well as enhanced E(2)-induced phosphorylation at S112. Chemical inhibition of PI-3K and mitogen-activated protein kinase kinase 1 inhibited E(2)-induced BAD phosphorylation at S112 and S136 and expression of dominant negative Ras-induced apoptosis in proliferating cells. Together, these data demonstrate a new nongenomic mechanism by which E(2) prevents apoptosis.

The Bik BH3-only protein is induced in estrogen-starved and antiestrogen-exposed breast cancer cells and provokes apoptosis

Evidence has been accumulating that some estrogen-dependent human breast cancers require estrogen for not only proliferation but also survival. To obtain insights into the molecular mechanisms of apoptosis of breast cancer cells subjected to estrogen starvation or exposed to antiestrogens, we characterized changes in the gene expression profile of MCF-7/BUS human breast cancer cells and revealed a strong induction of Bik, a member of the BH3-only proapoptotic proteins. The Bik mRNA transcript and protein were strongly induced by estrogen starvation or exposure to fulvestrant, a pure antiestrogen that competes with the natural estrogens for binding to the estrogen receptors. This Bik induction preceded apoptotic cell death, which was blocked by zVAD-fmk, a pancaspase inhibitor. Amounts of the Bcl-2-related proteins, such as Bcl-2, Bcl-XL, or Bax, showed only marginal changes in the presence or absence of estrogens or antiestrogens. Suppression of Bik expression by using the small interfering RNA effectively blocked the fulvestrant-induced breast cancer cell apoptosis. These results indicate that Bik is induced in MCF-7/BUS cells in the absence of estrogen signaling and plays a critical role in the antiestrogen-provoked breast cancer cell apoptosis.

Prognostic significance of p53, bcl-2, and Bax expression in early breast cancer

BACKGROUND

The use of adjuvant chemotherapy in early breast carcinoma is controversial, with most advocating its use in high-risk patients as defined by specific clinicopathologic parameters. Both bcl-2 and p53, which play a role in determining tumor growth by their effects on apoptosis and cell proliferation respectively, may serve to delineate this subset more accurately. The purpose of this study was to determine the prognostic value of bcl-2, Bax, and mutant p53 in stage I breast cancer.

STUDY DESIGN

A total of 75 patients with stage Ic breast carcinoma diagnosed from 1989 to 1992 were identified retrospectively and clinicopathologic parameters such as age, tumor size, estrogen receptor (ER) and progesterone receptor (PR) status, disease-free survival and overall survival obtained. Paraffin-embedded formalin-fixed tissues were immunostained with bcl-2, Bax and p53 monoclonal antibodies using a standard avidin biotin peroxidase reaction. Stained slides were evaluated by two independent pathologists for staining intensity and percentage of cells staining positively. Cox regression was used for multivariate survival analysis using the clinicopathologic parameters and molecular markers. Chi-square tests were used for frequency tables.

RESULTS

Mean patient age was 58 years (range 29 to 79 years) with a median followup of 80 months from time of diagnosis. The most common histopathology was infiltrating ductal carcinoma. Neither bcl-2 nor Bax expression was associated statistically with disease-free or overall survival. Expression of mutant p53 was associated with a significant decrease in both 5-year disease-free survival (70% versus 98%, p </= 0.01 in multivariate analysis) and 5-year overall survival (74% versus 100%, p = 0.03). Expression of bcl-2 was associated with hormone receptor expression and tumor diploid status. Of tumors expressing bcl-2, 36 of 49 (73%) were ER+ (p = 0.017, versus tumors not expressing bcl-2, 6 of 15 [40%]), 22 of 49 (45%) PR+ (p = 0.027 versus tumors not expressing bcl-2, 2 of 15 [13%]) and 28 of 44 (64%) diploid (p = 0.004 versus tumors not expressing bcl-2, 1 of 9 [11%]).

CONCLUSIONS

These results indicate that bcl-2 expression is significantly associated with hormonal receptor status and that p53 is a significant prognostic marker for survival in early breast cancer.

Estradiol reverses TGF-beta1-induced mesangial cell apoptosis by a casein kinase 2-dependent mechanism

BACKGROUND

The slower rate of progression of chronic renal disease in women than in men is explained in part by the ability of estradiol to reverse the stimulatory effect of transforming growth factor-beta1 (TGF-beta1) on collagen IV synthesis at the level of casein kinase 2 activation. Casein kinase 2 also phosphorylates and activates the pro-apoptotic protein, p53. We hypothesized that estradiol would reverse TGF-beta1-induced mesangial cell apoptosis by antagonizing the stimulatory effects of TGF-beta1 on casein kinase 2 activity, thereby preventing p53 activation.

METHODS

The effects of TGF-beta1 on mesangial cell apoptosis, p53 phosphorylation, Bax and Bcl-2 levels, caspase 9 activity, and cleavage of PARP were examined. The abilities of estradiol and a specific inhibitor of CK2 (5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole) (DRB) to modulate the effects of TGF-beta1 on these processes were also examined.

RESULTS

TGF-beta1 (2 ng/mL), which up-regulates CK2 activity, induces apoptosis in murine mesangial cells together with p53 serine389 phosphorylation, up-regulation of Bax, suppression of Bcl-2, destabilization of mitochondrial permeability transition pores, stimulation of caspase 9 activity and activation of PARP. TGF-beta1-induced p53 activation and all the intermediary steps leading to mesangial cell apoptosis were reversed by estradiol (10-9 mol/L) and by DRB, potent inhibitors of CK2 activity, but not by inhibitors of the p38 MAPK, ERK or JNK signaling cascades. In contrast, TGF-beta1 failed to induce apoptosis in p53 knockout mesangial cells.

CONCLUSIONS

Our data suggest that CK2 mediates the stimulatory effects of TGF-beta1 on mesangial cell apoptosis via a p53-dependent mechanism. The ability of estradiol to reverse TGF-beta1-induced apoptosis may contribute to the protective effects of female gender on the course of chronic renal disease.

17-beta-estradiol alters Jurkat lymphocyte cell cycling and induces apoptosis through suppression of Bcl-2 and cyclin A

In this investigation, the effects and potential mechanisms of female sex steroid action on proliferation, cell cycling, and apoptosis in Jurkat CD4 + T lymphocytes were examined. 17-beta-Estradiol (estrogen) inhibited Jurkat T cell proliferation, stimulated accumulation of cells in S and G2/M phases of the cell cycle, and induced apoptosis over 72 h in a dose-dependent manner. 4-Pregnene-3,20-dione (progesterone) did not induce redistribution of the cells in the cell cycle but did induce cytostasis and slightly increased apoptosis. Simultaneous staining with anti-BrDU and propidium iodide indicated that estrogen-treated Jurkat T cells proceeded through S phase prior to apoptosis. Progesterone halted cell cycle progression; cells did not progress through S phase or incorporate BrDU. Both hormones decreased the percentage of cells in S or G2/M expressing cyclin A protein, but did not affect cyclin D protein expression. Cyclin A mRNA was markedly decreased by estrogen. Bcl-2 protein and mRNA were also reduced in estrogen but not progesterone-treated Jurkat T lymphocytes. This data shows that high concentrations of estrogen or progesterone significantly suppress lymphoproliferation in association with suppression of cyclin A. Additionally, bcl-2 protein levels were suppressed in association with estrogen-induced apoptosis. These findings demonstrate direct, hormone-specific effects on lymphocytes that may provide insight into their role in immunomodulation or the development of autoimmunity.

Apoptosis inhibition mediated by medroxyprogesterone acetate treatment of breast cancer cell lines

Several reports suggested that steroidogenic hormones could be directly involved in the regulation of apoptosis in vitro, but whether this is due to blocking or promoting mechanism of these hormones remains controversial. However, it was shown that progesterone exhibited a protective effect against the apoptotic process during mouse mammary gland involution in vivo. In this study, we analyzed the effect of medroxyprogesterone acetate (MPA) treatment, an agonist of progesterone, on serum starvation induced apoptosis on breast cancer cell lines. Positive and negative progesterone receptor (PgR+ and PgR-) breast cancer cell lines were treated with MPA (10 nM), either in standard culture conditions or in serum-free medium to induce apoptosis. Cell survival, proliferation and apoptosis were simultaneously analyzed with the expression of apoptosis-related genes measured by a real time quantitative RT-PCR. At non cytotoxic doses, MPA protected PgR+ T47-D, MCF-7 and H466-B cell lines against serum depletion-induced apoptosis, while MPA did not protect PgR-MDA-MB-231 cells against serum depletion induced apoptosis. In PgR+ cell lines and in concordance with the protective effect, the pro-apoptotic HRK and BAK1 mRNAs were up-regulated after apoptosis induction, while they were no more induced in condition of protection against apoptosis after MPA treatment. We also observed, specifically in PgR+ cells, an up-regulation of BCLX-L and BCLX-S and a down-regulation of BCL2 mRNAs, which are specific to the MPA response and unrelated to apoptotic process. Involvement of these genes with regard to the MPA-mediated protection against apoptosis is discussed.

Estradiol up-regulates antiapoptotic Bcl-2 messenger ribonucleic acid and protein in tumorigenic ovarian surface epithelium cells

Most epithelial ovarian tumors appear to arise from the ovarian surface epithelium (OSE). Even though it has been suggested that estrogen may be associated with ovarian tumorigenesis, the exact role of estrogen in the regulation of apoptosis in neoplastic OSE cells remains uncertain. Immortalized OSE (IOSE) cell lines were generated from human normal OSE. These cell lines represent early neoplastic (IOSE-29), tumorigenic (IOSE-29EC), and late neoplastic (IOSE-29EC/T4 and IOSE-29EC/T5) transformation stages from human normal OSE. The present studies demonstrated that both mRNAs and proteins of estrogen receptor (ER) alpha and beta were expressed in IOSE cell lines. No difference was observed in normal OSE and IOSE-29 cells, whereas treatment with 17beta-estradiol (E(2); 10(-8)-10(-6) M) resulted in an increased thymidine incorporation and DNA content per culture in IOSE-29EC cells. This effect of E(2) was attenuated with tamoxifen treatment (10(-6) M), the estrogen antagonist, suggesting that the effect of E(2) is mediated through specific ERs. There was no stimulatory effect on thymidine incorporation before day 6, but after 6 days of E(2) treatment, thymidine incorporation was significantly increased. Because the ratio of thymidine incorporation to DNA content per culture did not change, this E(2) effect does not appear to indicate stimulation of proliferation but, rather, inhibition of apoptosis. In addition, treatment with tamoxifen (10(-6) M) induced apoptosis up to 3-fold in IOSE-29EC cells, whereas cotreatment with E(2) (10(-8)-10(-6) M) plus tamoxifen attenuated tamoxifen-induced apoptosis in a dose-dependent manner. Both proapoptotic bax and antiapoptotic bcl-2 at messenger RNA (mRNA) and protein levels were expressed in IOSE cell lines. Interestingly, treatments with E(2) resulted in a significant increase of bcl-2 mRNA and protein levels (2- and 1.7-fold, respectively), whereas no difference was observed in bax mRNA level. Thus, E(2) may enhance survival of IOSE-29EC by up-regulating bcl-2, and antiapoptotic bcl-2 may be a dominant regulator of apoptotic pathway in these cells. In conclusion, the present study indicates that early neoplastic (IOSE-29), tumorigenic (IOSE-29EC), and late neoplastic (IOSE-29EC/T4 and T5) OSE cells expressed both ERalpha and ERbeta at the mRNA and protein levels. In addition, E(2) prevented tamoxifen induced-apoptosis through ERs. The mechanism of E(2) action may be associated with up-regulation of bcl-2 gene at mRNA and protein levels. These results suggest that estrogen may play a role in ovarian tumorigenesis by preventing apoptosis in tumorigenic OSE cells.

Molecular markers for predicting response to tamoxifen in breast cancer patients

Tamoxifen is one of the most effective treatments for breast cancer. Standard practice is to select patients who are likely to respond to this therapy through the evaluation of estrogen receptor (ER) and progesterone receptor (PR) in the primary tumor tissue. Over the past 25 yr that physicians have been using ER determination to guide tamoxifen use, numerous studies have demonstrated that this molecular marker is useful in predicting benefit from tamoxifen. ER has been analyzed for many years using ligand-binding assays. However, current practice involves the use of immunohistochemical-based assays to detect ERalpha Immunohistochemistry (IHC) has several advantages. For example, IHC evaluates tumor cell heterogeneity, can be used to study small samples, is less expensive, and allows direct correlation with multiple histopathological tumor features and other molecular markers. PR, an estrogen-responsive protein, can also be useful in predicting response to tamoxifen in specific clinical situations. In recent years, several other markers of tamoxifen response have been examined, including: pS2 (another estrogen-regulated protein), heat-shock proteins 27 and 70, bcl-2 protein, c-erbB-2 (HER-2/neu) oncoprotein, and mutated p53 tumor suppressor protein. In this article, we present an analysis of the data on these new molecular markers. Overall, from numerous studies, the data indicate that in addition to ERalpha bcl-2 is a potential candidate to help further improve our ability to predict response to tamoxifen. ER and bcl-2 are the most useful molecular markers to better identify breast cancer patients who will respond to tamoxifen and who will have prolonged survival.

Different expression patterns of Bcl-2 family genes in breast cancer by estrogen receptor status with special reference to pro-apoptotic Bak gene

Oncogenic and anti-apoptotic Bcl-2 is expressed much less in estrogen receptor alpha (ERalpha) negative breast cancers, which show more malignant phenotypes, than ERalpha-positive, indicating that some other Bcl-2 family member(s) are involved in the apoptotic balance of the cancer cells. We first analyzed mRNA expression of pro-apoptotic Bak and Bax along with that of anti-apoptotic Bcl-2 and Bcl-xL, using breast cancer specimens of 27 patients. Bak mRNA was expressed much less in ERalpha negative breast cancers, along with reduced expression of Bcl-2. Immunostaining of sections of 108 patients confirmed the observation. Next, stable transformants of MCF-7 cells with sense Bak expression vector showed fewer colonies in soft agar compared with the parental cells, while stable introduction of antisense Bak vector enhanced colony formation at lower estradiol concentrations. The reduction of Bak may play important roles in malignant development of breast cancer to acquire estrogen independency, counteracting the reduced Bcl-2.