Variation of bcl-2 expression in breast ducts and lobules in relation to plasma progesterone levels: overexpression and absence of variation in fibroadenomas

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.

Evidence for a stem cell hierarchy in the adult human breast

Cellular pathways that contribute to adult human mammary gland architecture and lineages have not been previously described. In this study, we identify a candidate stem cell niche in ducts and zones containing progenitor cells in lobules. Putative stem cells residing in ducts were essentially quiescent, whereas the progenitor cells in the lobules were more likely to be actively dividing. Cells from ducts and lobules collected under the microscope were functionally characterized by colony formation on tissue culture plastic, mammosphere formation in suspension culture, and morphogenesis in laminin-rich extracellular matrix gels. Staining for the lineage markers keratins K14 and K19 further revealed multipotent cells in the stem cell zone and three lineage-restricted cell types outside this zone. Multiparameter cell sorting and functional characterization with reference to anatomical sites in situ confirmed this pattern. The proposal that the four cell types are indeed constituents of an as of yet undescribed stem cell hierarchy was assessed in long-term cultures in which senescence was bypassed. These findings identify an adult human breast ductal stem cell activity and its earliest descendants.

Benign breast diseases

Benign breast diseases have always been neglected in comparison to cancer, despite the fact that there are many more patients with such diseases than patients presenting to a breast clinic for cancer. Like normal breast tissues, benign breast diseases are under a complex system of controls by both systemic hormonal and local factors. In this review, we attempt to present an overview of the latest knowledge concerning the epidemiology, classification, clinical presentation, management, and physiopathology of these disorders.

Assessment of the proliferative, apoptotic and cellular renovation indices of the human mammary epithelium during the follicular and luteal phases of the menstrual cycle

Introduction

During the menstrual cycle, the mammary gland goes through sequential waves of proliferation and apoptosis. In mammary epithelial cells, hormonal and non-hormonal factors regulate apoptosis. To determine the cyclical effects of gonadal steroids on breast homeostasis, we evaluated the apoptotic index (AI) determined by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining in human mammary epithelial cells during the spontaneous menstrual cycle and correlated it with cellular proliferation as determined by the expression of Ki-67 during the same period.

Methods

Normal breast tissue samples were obtained from 42 randomly selected patients in the proliferative (n = 21) and luteal (n = 21) phases. Menstrual cycle phase characterization was based on the date of the last and subsequent menses, and on progesterone serum levels obtained at the time of biopsy.

Results

The proliferation index (PI), defined as the number of Ki-67-positive nuclei per 1,000 epithelial cells, was significantly larger in the luteal phase (30.46) than in the follicular phase (13.45; P = 0.0033). The AI was defined as the number of TUNEL-positive cells per 1,000 epithelial cells. The average AI values in both phases of the menstrual cycle were not statistically significant (P = 0.21). However, the cell renewal index (CRI = PI/AI) was significantly higher in the luteal phase (P = 0.033). A significant cyclical variation of PI, AI and CRI was observed. PI and AI peaks occurred on about the 24th day of the menstrual cycle, whereas the CRI reached higher values on the 28th day.

Conclusions

We conclude that proliferative activity is dependent mainly on hormonal fluctuations, whereas apoptotic activity is probably regulated by hormonal and non-hormonal factors.

Cyclin E overexpression enhances cytokine-mediated apoptosis in MCF7 breast cancer cells

Cyclin E, the regulatory component of the cyclin E/cyclin-dependent kinase (CDK) complex, is required for proliferation and overexpression of this cyclin is associated with many types of human tumors. To elucidate the mechanism by which cyclin E overexpression promotes tumorigenesis, cyclin E was overexpressed in two breast cancer lines: MCF7 and T47D. Cells overexpressing cyclin E display a marked decrease in the expression of Bcl-2, an antiapoptotic protein, and increased levels of the proapoptotic proteins Bad and Bax. The levels of Bcl-X(L) and Mcl-1 remain unchanged. Since the homeostasis of pro- and antiapoptotic proteins was altered, we asked if cyclin E overexpression modifies responses to cytokines. MCF7 cyclin E overexpressing cells have an enhanced sensitivity to Fas, TRAIL, and TNF-alpha-induced apoptosis. T47D cells overexpressing cyclin E have a significant increase in TNF-alpha and TRAIL-induced apoptosis. In conclusion, our results provide a link between expression of cyclin E, deregulation of Bcl-2, and an altered response to cytokine-mediated apoptosis.

Cell proliferation, apoptosis, and expression of Bcl-2 and Bax in non-lactating human breast epithelium in relation to the menstrual cycle and reproductive history

Cell proliferation, apoptosis, and the expression of Bcl-2 and Bax were investigated in breast tissue of healthy premenopausal women in order to study the effect of the menstrual cycle and reproductive history on the cell turnover in the non-lactating mammary gland epithelium. Immunohistochemistry was used to detect the proliferation-associated antigen Ki-67, as well as Bcl-2 and Bax. Apoptotic cells were identified by enzymatic labelling of fragmentized DNA (TUNEL-technique) and morphologic analysis. Consistent with published data, the proliferative activity and the frequency of apoptotic events as detected by morphologic analysis was higher in the luteal than in the follicular phase of the menstrual cycle. Parity, lactation, and age correlated with lower proliferative activity, whereas the frequency of apoptosis was not significantly influenced by the reproductive history. Staining patterns for Bax and Bcl-2 showed characteristic changes due to the menstrual cycle with a maximum of immunoreactivity for Bcl-2 in the follicular phase and for Bax in the luteal phase. However, there was no statistically significant association between Bcl-2/Bax immunoreactivity and menstrual cycle or reproductive parameters. We conclude that other molecular pathways than the Bax/Bcl-2 antagonism may additionally be involved in the regulation of apoptotic cell death in the breast epithelium. Knowledge of the entire complexity of apoptosis regulation is necessary to understand the observed effects of parity and lactation on mammary epithelial biology, and possibly to be able to influence pathological processes caused by an imbalance between cell renewal and elimination.

The effect of antisense Bcl-2 oligonucleotides on Bcl-2 protein expression and apoptosis in human bladder transitional cell carcinoma

PURPOSE

Bcl-2 is an important determinant of transitional cell carcinoma of the bladder recurrence and progression as well as a factor in patient response to chemotherapy or radiotherapy. We determined Bcl-2 down-regulation after antisense oligonucleotide therapy and synergism with mitomycin C in transitional cell carcinoma of the bladder.

MATERIALS AND METHODS

Bcl-2 protein was quantified using flow cytometry and immunohistochemistry in 4 bladder cancer cell lines, in bladder washings from 6 patients with carcinoma in situ and in 16 patient tumor samples. The synergistic effects of antisense oligonucleotides G3139 and 2009, and mitomycin C were investigated in 4 cell lines, while 2009 down-regulation was examined in 20 tumor explants in an ex vivo model.

RESULTS

Bcl-2 protein expression was found in all 4 cell lines and in 5 of the 6 cell populations derived from patients with carcinoma in situ. Of the 16 tumors 7 were classified positive by frozen section immunohistochemistry and quantitative flow cytometry. G3139 and 2009 down-regulated Bcl-2 protein expression in all 4 cell lines and 2009 down-regulated Bcl-2 protein expression in half of the Bcl-2 positive tumor specimens. There was only evidence in 1 cell line, T24/83, that Bcl-2 protein expression down-regulation enhanced mitomycin C induced apoptotic cell death.

CONCLUSIONS

Bcl-2 was expressed in a significant proportion of bladder tumors and in carcinoma in situ. Therefore, antisense oligonucleotides represent a viable strategy for Bcl-2 protein down-regulation. However, it may not always translate into an increased level of mitomycin C induced apoptosis in transitional cell carcinoma of the bladder.

Analysis of SYT-SSX fusion transcripts and bcl-2 expression and phosphorylation status in synovial sarcoma

Synovial sarcomas (SS) are characterized by a chromosomal translocation t(X;18)(p11.2;q11.2) which usually fuses the SYT gene from chromosome 18 to SSX1 or SSX2 genes on chromosome X. Also, a variant SYT-SSX4 fusion gene has recently been shown in a single SS case. In addition to these cytogenetic changes, bcl-2 expression, as assessed by immunohistochemistry, has been reported to be an almost general constitutive alteration of SS. In the present work, we analyze a series of 36 SS surgical samples (from 34 patients) by RT-PCR for the presence of the SYT-SSX1 or the SYT-SSX2 fusion transcript. The analysis was extended to SYT-SSX4 on SYT-SSX1-negative and SYT-SSX2-negative cases only. Our results showed a significant correlation between the SYT-SSX2 fusion and the monophasic SS histologic subtype. SYT-SSX1 fusion transcripts were present in both monophasic and biphasic tumors. The SYT-SSX4 fusion type was detected in a single monophasic SS. In the same series of SS cases, we also confirmed and extended the previously reported constitutive expression of bcl-2 protein, by using both immunohistochemical and western blot analysis. Moreover, we demonstrated that the BCL-2 gene is not rearranged or amplified at genomic level, indicating that the high levels of bcl-2 expression observed in SS might result from transcriptional activation of the gene and/or protein stabilization. Finally, we show that bcl-2 is not phosphorylated in tumors from patients who had been preoperatively treated with radio/chemotherapy, in tumors from untreated patients, or in an SS cell line (CME-1) after in vitro treatment with cytotoxic concentrations of DNA-damaging agents or taxanes. These data indicate that SS cells are unable to activate an apoptosis pathway involving bcl-2 phosphorylation/inactivation and may provide a possible explanation for the limited effectiveness of conventional pharmacological treatments of this tumor type.

Hormone-dependent nuclear localization of the tyrosine kinase iyk in the normal human breast epithelium and loss of expression during carcinogenesis

iyk, a member of the frk family of non-receptor tyrosine kinases, was originally isolated from normal mouse mammary glands and is characterized by a nuclear localizing signal within the SH2 domain. We have investigated the expression and subcellular localization of iyk in the normal human breast and in malignant breast diseases. Immuno-histochemical analyses revealed that in normal tissue iyk localizes to both cytoplasmic and nuclear compartments of breast epithelial cells. The subcellular distribution was dependent on the hormonal state, being mostly cytoplasmic during the follicular, proliferative phase of the menstrual cycle, whereas frequent nuclear staining was observed in the resting stages during the luteal phase and, most prominently, after menopause. Strikingly, invasive carcinomas, irrespective of tumor type or hormonal status of the patient, exhibited almost complete loss of iyk expression in both the cytoplasm and the nucleus. In contrast, in situ breast carcinomas from post-menopausal patients showed a clear reduction of the nuclear iyk localization while retaining cytoplasmic staining. Our results indicate that iyk expression is gradually lost during carcinogenesis; thus, iyk may be classified as a tumor-suppressor gene.

Apoptosis in the estrous and menstrual cycles

In the absence of pregnancy, the adult mammary gland is subjected to cyclic fluctuations of hormonal stimulation that constitute the estrous and menstrual cycles. The mammary epithelium responds to these systemic hormonal changes by regional proliferation, differentiation and cell death by apoptosis. The fact that the mammary epithelial response involves only a minor subset of the epithelial cells implies a delicate local control of epithelial cell fate resulting in either cell death or survival. Evidence gleaned from descriptive data suggests that the apoptosis-related genes of the Bcl-2 gene family, tissue remodeling genes, protein tyrosine kinases and master genes of the homeotic gene cluster may be involved in determining epithelial cell fate during the estrous cycle.

In vivo patterns of Bcl-2 family protein expression in breast carcinomas in relation to apoptosis

The expression of the pro-apoptotic proteins (Bax, Bak) and anti-apoptotic proteins (Bcl-2, Bcl-X, Mcl-1) was studied by immunohistochemistry in 110 invasive ductal breast carcinomas. The results were correlated with tumour grade, expression of oestrogen receptor (ER) and p53 protein, and the apoptotic index by combined morphology, immunohistochemistry, and a terminal UTP nick end labelling (TUNEL) procedure. Overall, Bcl-2, Bcl-X, Mcl-1, Bax, Bak, ER, and p53 were detected in 62, 75, 68, 75, 60, 68 and 26 per cent of the cases respectively, but at different levels in each case. A high apoptotic index was correlated with high tumour grade (p<0.001), overexpression of p53 (p<0.001), Bak expression (p<0.001), and low expression of Bcl-2 (p<0.001) and ER (p<0.001). No correlation was found between the apoptotic index and Bax, Bcl-X, and Mcl-1 immunostaining results. The expression of Bcl-2 and Bcl-X was correlated to that of ER. Overall, the results of this study strongly suggest that Bcl-2 and Bak expression is critical in regulating apoptosis in breast carcinomas.