Bcl-2 slows in vitro breast cancer growth despite its antiapoptotic effect

The Analysis of bcl-2 in Association with p53 and Ki-67 in Triple Negative Breast Cancer and Other Molecular Subtypes in Ghana

BACKGROUND

Little is known about the role of apoptosis in the tumorigenesis and prognosis of breast cancer in Ghana. Chemotherapeutic drug efficacy partially relates to apoptosis induction, rendering it a vital target in cancer therapy with unique biomarker opportunities that have not been exploited. Aberrations in this pathway are central to tumorigenesis, tumor progression, overall tumor growth, and regression during treatment therapies. Antiapoptotic bcl-2 (gene) and p53 are known to play roles in apoptosis while Ki-67 is a proliferative marker. The aim of our study is to determine the association of bcl-2 (protein) with p53 and Ki-67 in 203 consecutive breast cancer cases over a 10-year period.

METHOD

A retrospective cross-sectional study on archival FFPE tissue blocks over a 9-year period with abstraction of clinicopathologic data. Two hundred and three consecutive and suitable FFPE blocks were selected for tissue microarray (TMA) construction, and IHC (bcl-2 (protein), Ki-67, p53, cyclin D, pan cytokeratins A and E, ER, PR, and HER2/neu) was done. Expressions of bcl-2 (protein), p53, and Ki-67 were related to histological grade, lymphovascular invasion, and molecular subtypes. SPSS version 23 was used to analyze results.

RESULTS

Most of our cases were in the fifth decade of life (31%); invasive carcinoma of no special type (NST) was predominant (87%); histological grade III (38%) was the highest; and Luminal A (19.8%), Luminal B (9.9%), HER2 (16%), and TNBC (54.3%) constituted the molecular classes. bcl-2 expression was found in 38% of the cases. Our cases also showed mutation in p53 (36.7%) and ki-67 expression (62.5%). bcl-2 (protein) and p53 significantly correlated with Luminal B and TNBC (p < 0.01). Ki-67 also correlated significantly with Luminal A and B and HER2 overexpression (p < 0.01). Premenopausal age (40-49) and histological grade inversely correlated with bcl-2 (protein) expression. p53 statistically correlated with Ki-67 (p < 0.05).

CONCLUSION

Our results show high expression of bcl-2 (protein) suggesting an important role of apoptosis in Ghanaian breast cancer cases. bcl-2 (protein), p53, and Ki-67 expressions emerged interdependently from this research and can thus be manipulated in prediction and prognosis of breast cancers in our setting.

Ligand activated progesterone receptor B drives autophagy-senescence transition through a Beclin-1/Bcl-2 dependent mechanism in human breast cancer cells

Loss of progesterone-receptors (PR) expression is associated with breast cancer progression. Herein we provide evidence that OHPg/PR-B through Beclin-1 evoke autophagy-senescence transition, in breast cancer cells. Specifically, OHPg increases Beclin-1 expression through a transcriptional mechanism due to the occupancy of Beclin-1 promoter by PR-B, together with the transcriptional coactivator SRC-2. This complex binds at a canonical half progesterone responsive element, which is fundamental for OHPg effects, as shown by site-directed mutagenesis. Beside, OHPg via non-genomic action rapidly activates JNK, which phosphorylates Bcl-2, producing the functional release from Beclin-1 interaction. This is not linked to an efficient autophagic flux, since p62 levels, marker of degradation via lysosomes, were not reduced after sustained OHPg stimulus. Instead, the cell cycle inhibitor p27 was induced, together with an irreversible G1 arrest, hallmark of cellular senescence. Specifically the increase of senescence-associated β-galactosidase activity was blocked by Bcl-2 siRNA but also by Beclin-1 siRNA. Collectively these findings support the importance of PR-B expression in breast cancer cells, thus targeting PR-B may be a useful strategy to provide additional approaches to existing therapies for breast cancer patients.

Expression of Beclin 1 and Bcl-2 in pancreatic neoplasms and its effect on pancreatic ductal adenocarcinoma prognosis

Aberrant expression of Beclin 1 and B-cell lymphoma-2 (Bcl-2) has been identified in a variety of human tumors; however, little information is available for pancreatic neoplasms. The present study analyzed the expression of Beclin 1 and Bcl-2 in pancreatic ductal adenocarcinoma (PDAC) and solid pseudopapillary neoplasm (SPN) of the pancreas, and evaluated their prognostic significance for PDAC. The present study included 117 PDAC, 43 SPN and 32 chronic pancreatitis (CP) cases. Levels of Beclin 1 and Bcl-2 expression were evaluated semiquantitatively by immunohistochemistry, and their correlation with the survival of patients with PDAC was determined. Beclin 1 was upregulated in 74 (63.2%) PDAC, 26 (60.5%) SPN, and 14 (43.8%) CP cases. Bcl-2 was upregulated in 38 (32.5%) PDAC, 11 (25.6%) SPN and 24 (75.0%) CP cases. High Beclin 1 and low Bcl-2 expression was significantly correlated with poor differentiation and distant metastasis in PDAC, and associated with the presence of nuclear pleomorphism in SPN and with advanced Tumor-Node-Metastasis stage in PDAC. Beclin 1 and Bcl-2 levels were inversely correlated in PDAC, whereas they were positively correlated in SPN. Low Beclin 1 and high Bcl-2 expression was associated with improved disease-free survival and overall survival (OS). However, the association of Beclin 1 with survival was not significant in the Cox analysis, whereas Bcl-2 expression was significantly correlated with OS in the multivariate analysis. In conclusion, Beclin 1 upregulation exacerbated the progression and aggressiveness of pancreatic neoplasms, and Bcl-2 downregulated expression was an independently poor prognostic factor for PDAC.

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.

Reasons for cancer metastasis: A holistic perspective

Over several years, scientists investigating cancer have focused their efforts on elucidating the mechanisms underlying cancer metastasis, with the aim of finding a way to inhibit this process. These mechanisms, however, only explain the process of cancer metastasis, but do not explain why cancer would metastasize in the first place. Cancer metastasizes due to several factors, namely attack by the immune system, lack of oxygen and necessary nutrients, large amounts of lactic acid produced by glycolysis and increased cell death. Therefore, the majority of the presently available treatments for cancer also bear the potential to induce metastasis. Thus, it is crucial in medical practice to minimize the risk of cancer metastasis during a time when there are no effective means to inhibit this process.

Bcl-2 is a highly significant prognostic marker of hormone-receptor-positive, human epidermal growth factor receptor-2-negative breast cancer

B-cell lymphoma-2 (Bcl-2) is one of the most important anti-apoptotic genes. Although Bcl-2 promotes tumor cell survival in vitro, previous studies have shown conflicting results regarding the association between Bcl-2 and breast cancer survival. The aim of this study was to assess the prognostic significance of Bcl-2 according to the molecular tumor subtype in primary invasive breast cancer patients. The relationship between immunohistochemical Bcl-2 expression and overall survival was analyzed in 2399 primary invasive breast cancer patients treated by curative surgery. Patients were classified into four subtypes based on hormone receptor (HR) and human epidermal growth factor receptor-2 (HER2) status: HR+/HER2-, HR+/HER2+, HR-/HER2+, and HR-/HER2-. A total of 1304 patients (54.4 %) had Bcl-2 positive (+) tumors by immunohistochemistry. Bcl-2 (+) tumors were significantly associated with a younger age (<50 years), early stage, lower grade, positive expression of HR, and negative expression of HER2. In the HR+/HER2- group, patients with Bcl-2 (+) tumors showed a significantly better prognosis (p < 0.001). In contrast, there was no significant prognostic effect of Bcl-2 expression in other subtypes. In multivariate analysis, Bcl-2 positivity remained an independent, favorable prognostic factor in the HR+/HER2- subtype (hazard ratio, 0.609; 95 % confidence interval, 0.424-0.874; p < 0.007). The prognostic significance of Bcl-2 expression differed according to the molecular subtype of breast cancer. The expression of Bcl-2 was an independent, favorable prognostic factor in breast cancer patients with the HR+/HER2- subtype.

MTA1--a stress response protein: a master regulator of gene expression and cancer cell behavior

Gene mutation's role in initiating carcinogenesis has been controversial, but it is consensually accepted that both carcinogenesis and cancer metastasis are gene-regulated processes. MTA1, a metastasis-associated protein, has been extensively researched, especially regarding its role in cancer metastasis. In this review, I try to elucidate MTA1's role in both carcinogenesis and metastasis from a different angle. I propose that MTA1 is a stress response protein that is upregulated in various stress-related situations such as heat shock, hypoxia, and ironic radiation. Cancer cells are mostly living in a stressful environment of hypoxia, lack of nutrition, and immune reaction attacks. To cope with all these stresses, MTA1 expression is upregulated, plays a role of master regulator of gene expression, and helps cancer cells to survive and migrate out of their original dwelling.

Resistance to apoptosis should not be taken as a hallmark of cancer

In the research community, resistance to apoptosis is often considered a hallmark of cancer. However, pathologists who diagnose cancer via microscope often see the opposite. Indeed, increased apoptosis and mitosis are usually observed simultaneously in cancerous lesions. Studies have shown that increased apoptosis is associated with cancer aggressiveness and poor clinical outcome. Furthermore, overexpression of Bcl-2, an antiapoptotic protein, is linked with better survival of cancer patients. Conversely, Bax, CD95, Caspase-3, and other apoptosis-inducing proteins have been found to promote carcinogenesis. This notion of the role of apoptosis in cancer is not new; cancer cells were found to be short-lived 88 years ago. Given these observations, resistance to apoptosis should not be considered a hallmark of cancer.

Molecular interactions of Bcl-2 and Bcl-xL with mortalin: identification and functional characterization

Bcl-2 family of proteins consists of both pro-apoptotic and anti-apoptotic members that control cellular apoptosis. They predominantly reside in the mitochondria and control the release of apoptotic factors from the mitochondria to the cytosol by regulating its membrane potential and opening the PT (permeability transition) pore. Here we report bioinformatics and biochemical evidence to demonstrate the interaction between Bcl-2 and Bcl-xL with a stress chaperone, mortalin. We demonstrate that such interaction results in the abrogation of mortalin-p53 interaction leading to nuclear translocation and transcriptional reactivation of p53 function that results in an induction of senescence in cancer cells.

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.

Enhanced radiosensitivity and chemosensitivity of breast cancer cells by 2-deoxy-d-glucose in combination therapy

Breast cancer is the most common malignancy, and it is also the major cause of cancer-related deaths of women worldwide. Breast cancer treatment involves surgery, chemotherapy, radiation therapy, or combination therapy, and novel strategies are needed to boost the oncologic outcome. The non-metabolizable glucose analogue, 2-deoxy-D-glucose (2-DG) which inhibits glucose synthesis and adenosine triphosphate production, is one of the important discoveries involving the disturbances that can be caused to the process of the metabolism. The glucose analogue, 2-DG, is known as a tumor sensitizer to irradiation (IR) and chemotherapy, which help improve the treatment rates. It enhances the cytotoxicity via oxidative stress, which is more redundant in tumor cells than in normal ones. This article provides a brief summary on studies related to 2-DG chemo-/radio-sensitization effects by combination therapy of 2-DG/IR or 2-DG/doxorubicin.

Heterogeneity of Bcl-2 expression in metastatic breast carcinoma

Bcl-2 is an antiapoptotic protein that promotes cell survival, but also may block proliferation. In breast cancer, bcl-2 expression correlates with favorable prognosis and estrogen receptor (ER) positivity. However, experimental data have paradoxically suggested that bcl-2 promotes chemoresistance and metastasis. A direct and comprehensive comparison of bcl-2 expression between primary breast carcinomas and paired distant metastases has not been performed. We completed rapid autopsies on 17 patients with archived primary tumors and metastatic breast carcinoma, and created single-patient tissue microarrays containing each patient's primary tumor and matched metastases. Expression of bcl-2, ER, progesterone receptor, and HER-2 in primary tumors and matched metastases were compared by immunohistochemistry. All 11 ER-positive cases showed bcl-2 labeling in the primary tumor, whereas only 3 of 6 ER-negative cases did (P=0.029). In 10 cases, bcl-2 labeling in metastases was similar to that of the primary, although 3 cases showed significant variation among metastases. In six other cases, bcl-2 labeling was lost or significantly diminished in metastases. Five of the latter cases were Luminal A (ER-positive, HER-2-negative) primaries, three of which lost hormone receptors in metastases. Only 1 of 17 cases showed an increase in bcl-2 labeling in metastases compared with the paired primary tumor. In conclusion, bcl-2 is infrequently upregulated in metastatic breast carcinoma. Instead, downregulation of bcl-2 expression may occur in the setting of hormone therapy resistance. Our findings call into question the potential utility of anti-bcl-2 therapy in metastatic breast cancer.

Impact of BCL2 and p53 on postmastectomy radiotherapy response in high-risk breast cancer. A subgroup analysis of DBCG82 b&c

PURPOSE

To examine p53 and BCL2 expression in high-risk breast cancer patients randomized to postmastectomy radiotherapy (PMRT).

PATIENTS AND METHODS

The present analysis included 1 000 of 3 083 high-risk breast cancer patients randomly assigned to PMRT in the DBCG82 b&c studies. Tissue microarray sections were stained with immunohistochemistry for p53 and BCL2. Median potential follow-up was 17 years. Clinical endpoints were locoregional recurrence (LRR), distant metastases (DM), overall mortality, and overall survival (OS). Statistical analyses included Kappa statistics, chi(2) or exact tests, Kaplan-Meier probability plots, Log-rank test, and Cox univariate and multivariate regression analyses.

RESULTS

p53 accumulation was not significantly associated with increased overall mortality, DM or LRR probability in univariate or multivariate Cox regression analyses. Kaplan-Meier probability plots showed reduced OS and improved DM and LRR probabilities after PMRT within subgroups of both p53 negative and p53 positive patients. Negative BCL2 expression was significantly associated with increased overall mortality, DM and LRR probability in multivariate Cox regression analyses. Kaplan-Meier probability plots showed a significantly improved overall survival after PMRT for the BCL2 positive subgroup, whereas practically no survival improvement was seen after PMRT for the BCL2 negative subgroup. In multivariate analysis of OS, however, no significant interaction was found between BCL2 and randomization status. Significant reductions in LRR probability after PMRT were recorded within both the BCL2 positive and BCL2 negative subgroups.

CONCLUSION

p53 was not associated with survival after radiotherapy in high-risk breast cancer, but BCL2 might be.

High expression of maspin is associated with early tumor relapse in breast cancer

Maspin is a serine protease inhibitor with tumor suppressor activity. Maspin can suppress tumor growth and metastasis in vivo and tumor cell motility and invasion in vitro. Maspin also modulates apoptosis of tumor cells, possibly by modulating the expression of the B-cell lymphoma-2 family member. p53 regulates the expression of the tumor suppressor gene maspin. Breast cancer is known for its propensity to recur even after decades. The biology behind this phenomenon of tumor dormancy is poorly understood. This study was conducted to clarify the role of maspin and B-cell lymphoma-2 in early and late recurring breast cancer. The expression of maspin, B-cell lymphoma-2, p53, and estrogen receptor was studied by immunohistochemistry in 73 primary breast cancers and in their metastatic relapses detected within 2 years, or 5 or 10 years after primary surgery. The cytoplasmic expression of maspin was significantly higher in the primary tumors of the early metastasizing breast cancers (first tumor relapse within 2 years) and also in their metastases compared to late metastasizing cancers. An opposite activity was observed in the expression of B-cell lymphoma-2. The level of B-cell lymphoma-2 staining was lower in the early relapsing cancers and significantly lower in their metastases, compared to tumors which metastasized 5 or 10 years after primary surgery. High cytoplasmic expression of maspin and low expression of B-cell lymphoma-2 in primary breast cancer predict early tumor relapse.

Microarray and pathway analysis reveals decreased CDC25A and increased CDC42 associated with slow growth of BCL2 overexpressing immortalized breast cell line

Bcl-2 is an anti-apoptotic protein that is frequently overexpressed in cancer cells but its role in carcinogenesis is not clear. We are interested in how Bcl-2 expression affects non-cancerous breast cells and its role in the cell cycle. We prepared an MCF10A breast epithelial cell line that stably overexpressed Bcl-2. We analyzed the cells by flow cytometry after synchronization, and used cDNA microarrays with quantitative reverse-transcription PCR (qRT-PCR) to determine differences in gene expression. The microarray data was subjected to two pathway analysis tools, parametric analysis of gene set enrichment (PAGE) and ingenuity pathway analysis (IPA), and western analysis was carried out to determine the correlation between mRNA and protein levels. The MCF10A/Bcl-2 cells exhibited a slow-growth phenotype compared to control MCF10A/Neo cells that we attributed to a slowing of the G(1)-S cell cycle transition. A total of 363 genes were differentially expressed by at least two-fold, 307 upregulated and 56 downregulated. PAGE identified 22 significantly changed gene sets. The highest ranked network of genes identified by IPA contained 24 genes. Genes that were chosen for further analysis were confirmed by qRT-PCR, however, the western analysis did not always confirm differential expression of the proteins. Downregulation of the phosphatase CDC25A could solely be responsible for the slow growth phenotype in MCF10A/Bcl-2 cells. Increased levels of GTPase Cdc42 could be adding to this effect. PAGE and IPA are valuable tools for microarray analysis, but protein expression results do not always follow mRNA expression results.

Expression patterns and prognostic value of Bag-1 and Bcl-2 in breast cancer

Introduction

Bcl-2 antanogene-1 (Bag-1) binds the anti-apoptotic mediator Bcl-2, and enhances its activity. Bcl-2 and Bag-1 are associated with chemotherapy resistance in cancer cells. Drugs that target Bcl-2 are currently in clinical development. The purpose of the present study was to examine expression patterns of Bag-1 in a large cohort of breast tumors and to assess the association with Bcl-2, estrogen receptor, progesterone receptor and Her2/neu, and other clinical/pathological variables.

Methods

Tissue microarrays containing primary specimens from 638 patients with 10-year follow-up were employed, and the expression of Bag-1, Bcl-2, estrogen receptor, progesterone receptor and Her2/neu was assessed using our automated quantitative analysis method. We used cytokeratin to define pixels as breast cancer (tumor mask) within the array spot, and we measured biomarker expression within the mask using Cy5 conjugated antibodies.

Results

High Bcl-2 expression was associated with improved survival in the entire cohort and in the node-positive subset (P = 0.008 and P = 0.002, respectively). High Bag-1 expression was associated with improved survival in the node-positive subset (P = 0.006). On multivariable analysis, neither Bcl-2 nor Bag-1 retained their independence as prognostic markers. Strong associations were found between Bag-1, Bcl-2, estrogen receptor and progesterone receptor.

Conclusion

Bag-1 and Bcl-2 expression in breast tumors is associated with improved outcome and steroid receptor positivity. Evaluation of Bcl-2 and Bag-1 expression in breast cancer may identify a subset of patients with a favorable prognosis, who might not benefit from chemotherapy or who might benefit from Bcl-2 targeting agents in addition to antihormonal therapy.

The correlations between HPV16 infection and expressions of c-erbB-2 and bcl-2 in breast carcinoma

Breast carcinoma (BC) is a prevalent malignant tumour occurring in women. Many studies have indicated the role of human papilloma virus type 16 (HPV16) in the pathogenesis of BC; however, the correlations of HPV16 infection with the clinicopathologic features of BC and the expressions of c-erbB-2 and bcl-2 have not yet been elucidated. In this study, HPV16 was detected by amplifying the HPV16 E6 gene by the polymerase chain reaction method, and the expressions of c-erbB-2 and bcl-2 in 40 BCs and 20 normal breast tissue samples, obtained from Shaanxi Province, were examined using the streptavidin-peroxidase method with monoclonal antibodies specific to c-erbB-2 and bcl-2. The infection rate of HPV16 E6 and the positive expression rate of c-erbB-2 were significantly higher in the BCs than in the normal tissues (HPV16 E6: 60% vs. 5%; c-erbB-2: 42.5% vs. 5%, P < 0.05). However, the positive expression rate of bcl-2 was significantly lower in the BCs than in the normal tissues (67.5% vs. 95%, P < 0.05). The infection rate of HPV16 did not correlate with any of the pathological features observed (P > 0.05). HPV16 infection correlated with bcl-2 expression (P = 0.015) but not with c-erbB-2 expression (P = 0.747) in the BCs. Interestingly, HPV16 infection correlated with bcl-2 expression in grade I BCs (P = 0.018) but not in grade II-III BCs (P = 0.633). Our data suggest that HPV16 infection is correlated with bcl-2 expression in BCs.

DNA-damage response network at the crossroads of cell-cycle checkpoints, cellular senescence and apoptosis

Tissue homeostasis requires a carefully-orchestrated balance between cell proliferation, cellular senescence and cell death. Cells proliferate through a cell cycle that is tightly regulated by cyclin-dependent kinase activities. Cellular senescence is a safeguard program limiting the proliferative competence of cells in living organisms. Apoptosis eliminates unwanted cells by the coordinated activity of gene products that regulate and effect cell death. The intimate link between the cell cycle, cellular senescence, apoptosis regulation, cancer development and tumor responses to cancer treatment has become eminently apparent. Extensive research on tumor suppressor genes, oncogenes, the cell cycle and apoptosis regulatory genes has revealed how the DNA damage-sensing and -signaling pathways, referred to as the DNA-damage response network, are tied to cell proliferation, cell-cycle arrest, cellular senescence and apoptosis. DNA-damage responses are complex, involving "sensor" proteins that sense the damage, and transmit signals to "transducer" proteins, which, in turn, convey the signals to numerous "effector" proteins implicated in specific cellular pathways, including DNA repair mechanisms, cell-cycle checkpoints, cellular senescence and apoptosis. The Bcl-2 family of proteins stands among the most crucial regulators of apoptosis and performs vital functions in deciding whether a cell will live or die after cancer chemotherapy and irradiation. In addition, several studies have now revealed that members of the Bcl-2 family also interface with the cell cycle, DNA repair/recombination and cellular senescence, effects that are generally distinct from their function in apoptosis. In this review, we report progress in understanding the molecular networks that regulate cell-cycle checkpoints, cellular senescence and apoptosis after DNA damage, and discuss the influence of some Bcl-2 family members on cell-cycle checkpoint regulation.

Analyses of Bcl-2, Survivin, and CD44v6 expressions and human papillomavirus infection in cervical carcinomas

Infection with human papillomaviruses (HPV), and suppression of apoptosis and cell adhesion are putative aetiological factors to cervical carcinogenesis. However, controversial results have been reported with respect to their relationships with cervical carcinomas. Here we analysed papillomavirus infection, apoptotic index (AI), expressions of the anti-apoptotic proteins Bcl-2 and Survivin, and expression of the cell-adhesion protein CD44 in cervical tissue samples from individuals with and without cervical carcinomas. Although both HPV16 and HPV18 are reportedly important aetiological factors, we found that cervical carcinomas were highly associated with HPV16 but not HPV18 infection. Immunohistochemistry showed that the percentages of cells expressing Bcl-2, Survivin, and CD44v6 were greatly increased in samples of cervical carcinomas. Furthermore, the expression rates of Survivin and CD44v6 increased whereas that of Bcl-2 declined as cervical cancers developed into more advanced clinical or histopathological stages. Surprisingly, there was little difference in AI between control and cervical cancer samples. These observations provide further evidence that HPV infection, apoptosis and cell adhesion abnormalities are related to cervical cancers. They also suggest that Bcl-2, Survivin and CD44v6 expressions, and HPV16 infection could be useful indices in screening of cervical carcinomas.

Inhibiting the apoptosis pathway using MDM2 in mammalian cell cultures

The ability to regulate apoptosis in mammalian cell cultures represents one approach to developing more economical and efficient processes. Genetic modification of cells using anti-apoptotic genes is one method that may be used to improve cellular performance. This study investigates a method to inhibit upstream apoptosis pathways through the overexpression of MDM2, an E3 ubiquitin ligase for p53. Both 293 and CHO cells expressing MDM2 were examined under both batch and spent media conditions. For batch cultures, MDM2 overexpression increased viable cell densities and viabilities over control cells with the largest enhancements observed in CHO cells. When CHO cells were passaged without medium exchange, cells expressing MDM2 reached a viable cell density that was nearly double the control and survived for an extra day in culture. When exposed to spent media initially, both 293-MDM2 and CHO-MDM2 cells continued to grow for 2 days while the control cells stopped growing after the first day. DNA analysis using flow cytometry confirmed that while CHO controls were found to be undergoing DNA fragmentation, CHO-MDM2 cells exhibit DNA degradation at a much slower rate. When compared to Bcl-2-expressing cells, MDM2 expression showed greater protection against apoptosis in passaged culture, spent medium, and following transient p53 overexpression. However, expression of the RING sequence of MDM2 responsible for E3 ligase activity without the other components of the protein was found to be toxic to 293 cells in culture. These results suggest that the overexpression of heterologous MDM2 represents a promising method to delay apoptosis in mammalian cell cultures.

Lymph node status as a guide to selection of available prognostic markers in breast cancer: the clinical practice of the future?

Prognosticators evaluating survival in breast cancer vary in significance in respect to lymph node status. Studies have shown e.g. that HER2/neu immunohistochemistry or HER2/neu gene amplification analysis do perform well as prognosticators in lymph node positive (LN +) patients but are less valuable in lymph node negative (LN -) patients. We collected data from different studies and tried to evaluate the relative significance of different prognosticators in LN+/LN- patient groups. In LN+ patients HER2/neu and E-cadherin immunohistochemistry were the statistically most significant prognosticators followed by proliferation associated features (mitotic counts by SMI (standardised mitotic index) or MAI (mitotic activity index), or S-phase fraction). Bcl-2 immunohistochemistry was also significant but p53 and cystatin A had no significance as prognosticators. In LN- patients proliferation associated prognosticators (SMI, MAI, Ki-67 index, PCNA immunohistochemistry, S-phase fraction) are especially valuable and also Cathepsin D, cystatin A, and p53 are significant, but HER2/neu or bcl-2, or E-cadherin less significant or without significance. We find that in studies evaluating single prognosticators one should distinguish between prognosticators suitable for LN+ and LN- patients. This will allow the choice of best prognosticators in evaluating the prospects of the patient. The distinction between LN+ and LN- patients in this respect may also be of special value in therapeutic decisions.

Bcl-2 is a prognostic marker in breast cancer independently of the Nottingham Prognostic Index

PURPOSE

Prognostication of breast cancer using clinicopathologic variables, although useful, remains imperfect. Many reports suggest that gene expression profiling can refine the current approach. Alternatively, it has been shown that panels of proteins assessed by immunohistochemistry might also be useful in this regard. We evaluate the prognostic potential of a panel of markers by immunohistochemistry in a large case series to establish if either a single marker or a panel could improve the prognostic power of the Nottingham Prognostic Index (NPI). We validated the results in an independent series.

EXPERIMENTAL DESIGN AND RESULTS

The expression of 13 biomarkers was evaluated in 930 breast cancers on a tissue microarray. Eight markers [estrogen receptor (ER), progesterone receptor (PR), Bcl-2, cyclin E, p53, MIB-1, cytokeratin 5/6, and HER2] showed a significant association with survival at 10 years on univariate analysis. On multivariate analysis that included these eight markers and the NPI, only the NPI [hazard ratio (HR), 1.35; 95% confidence interval (95% CI), 1.16-1.56; P = 0.0005], ER (HR, 0.59; 95% CI, 0.39-0.88; P = 0.011), and Bcl-2 (HR, 0.68; 95% CI, 0.46-0.99; P = 0.055) were significant. In a subsequent multivariate analysis that included the NPI, ER, and Bcl-2, only Bcl-2 (HR, 0.62; 95% CI, 0.44-0.87; P = 0.006) remained independent of NPI (HR, 1.50; 95% CI, 1.16-1.56; P = 0.004). In addition, Bcl-2, used as a single marker, was more powerful than the use of a panel of markers. Based on these results, an independent series was used to validate the prognostic significance of Bcl-2. ER and PR were also evaluated in this validation series. Bcl-2 (HR, 0.83; 95% CI, 0.71-0.96; P = 0.018) retained prognostic significance independent of the NPI (HR, 2.04; 95% CI, 1.67-2.51; P < 0.001) with an effect that was maximal in the first 5 years.

CONCLUSION

Bcl-2 is an independent predictor of breast cancer outcome and seems to be useful as a prognostic adjunct to the NPI, particularly in the first 5 years after diagnosis.

Molecular biology of breast cancer

Although Breast Cancer (BC) has been considered for many years as a single entity with a common management and treatment, it is actually a extremely heterogeneous disease which includes at least 4 or 5 very different subtypes. The first step in the recognition of the heterogeneity of BC was the demonstration of the presence of functional hormonal receptors (HR) in nearly two thirds of breast cancer specimens. This finding, which established a first classification of BC in two clear subtypes (HR-positive and HR-negative) was followed by the demonstration of many other differential features. The her2/neu gene alteration, present in nearly 20% of BC tumors, is probably the most relevant of them, but certainly not the only one. The development of new technologies and, in particular, the use of complementary DNA (cDNA) microarrays will allow us now the simultaneous analysis of thousands of genes and the establishment of new, more refined BC subtypes based on gene expression profiles/genetic fingerprints. This review discusses the practical applications of molecular analysis of BC, which can be classified in four categories: 1. Establishment of a new molecular taxonomy of breast cancer. 2. Definition of prognostic factors/prognostic indexes based on molecular/genetic peculiarities. 3. Prediction of response to diverse antitumoral treatments. 4. Identification of molecular targets that allows the development of new tailored antitumor treatments.

Bag-1 and Bcl-2 gene transfer in malignant glioma: modulation of cell cycle regulation and apoptosis

Bag-1 is a heat shock 70 kDa (Hsp70)-binding protein that can collaborate with Bcl-2 in suppressing apoptosis under some conditions. Here, we report that 11 of 12 human glioma cell lines express Bag-1 protein in vitro. Moreover, 15 of 19 human glioblastomas expressed Bag-1 as assessed by immunohistochemistry in primary tumor specimens. To examine the biological effects of Bag-1 in glioma cells, we expressed Bag-1 or Bcl-2 transgenes in 2 human malignant glioma cell lines, LN-18 and LN-229. Bag-1 significantly slowed glioma cell growth and reduced clonogenicity of both cell lines in vitro. Coexpressed Bcl-2 abrogated these effects of Bag-1. Intracranial LN-229 glioma xenografts implanted into nude mice revealed a substantial growth advantage afforded by Bcl-2. Bag-1 had no such effect, either in the absence or presence of Bcl-2. Upon serum starvation in vitro, Bcl-2 prevented cell death whereas Bag-1 did not. Both Bcl-2 and Bag-1 slowed proliferation of serum-starved cells when expressed alone. Importantly, coexpression of Bcl-2 and Bag-1 provided a distinct growth advantage under conditions of serum starvation that is probably the result of (i) the death-preventing activity of Bcl-2 and (ii) the property of Bag-1 to overcome a Bcl-2-mediated enhancement of exit from the cell cycle. In contrast to these Bcl-2/Bag-1 interactions observed under serum starvation conditions, Bag-1 did not further enhance the strong protection from staurosporine-, CD95 (Fas/Apo1) ligand-, Apo2 ligand (TRAIL)- or chemotherapeutic drug-induced apoptosis afforded by Bcl-2. Taken together, these results indicate a role for Bag-1/Bcl-2 interactions in providing a survival advantage to cancer cells in a deprived microenvironment that may be characteristic of ischemic/hypoxic tumors such as human glioblastoma multiforme, and suggest that Bcl-2/Bag-1 interactions also modulate cell proliferation.

Pluronic block copolymers alter apoptotic signal transduction of doxorubicin in drug-resistant cancer cells

Pluronic block copolymer P85 (P85) sensitizes multidrug resistant (MDR) cancer cells resulting in the increase of cytotoxic activity of antineoplastic agents. This effect is attributed to the inhibition of the most clinically relevant drug efflux transporter, P-glycoprotein (Pgp), through the combined ATP depletion and inhibition of Pgp ATPase activity. The present study elucidates effects of an anticancer agent, doxorubicin (Dox), formulated with P85 on drug-induced apoptosis in MDR cancer cells. Early and late stages of apoptosis were detected by Annexin V and TUNEL methods, respectively. In parallel experiments, the expression of genes related to apoptosis, BCL2, BCLXL, BAX, P53, APAF1, Caspase 3, and Caspase 9, was determined by RT-PCR. The obtained data suggest that Dox/P85 formulation induces apoptosis in the resistant cancer cells more efficiently than free Dox. The treatment of the cells with Dox alone simultaneously activated a proapoptotic signal and an antiapoptotic cellular defense. Therefore, the apoptosis induction by Dox was substantially limited. In contrast, the treatment of the cells with Dox/P85 formulation significantly enhanced the proapoptotic activity of the drug and prevented the activation of the antiapoptotic cellular defense. This is likely to result in the stronger cytotoxic response of the resistant cells to the Dox/P85 formulation compared to the free drug.

Magnetic resonance imaging and biological markers in pituitary adenomas with invasion of the cavernous sinus space

The preoperative diagnosis of cavernous sinus invasion remains difficult and controversial, and there are currently no reliable histological or molecular markers that predict pituitary tumour behaviour and response to treatment. We evaluated 45 patients with pituitary adenoma. The results have shown that the sensitivity of MRI for indicating cavernous sinus invasion in this prospective study was 60%, specificity 85%, positive predictive value 83.33%, negative predictive value 62.96%. Forty-five specimens of pituitary adenomas were analyzed for expression of F8, VEGF, Ki-67, c-myc, bcl-2, nm23 and MMP-9 immunoreactivity using immunoperoxidase staining. MVD was assessed using F8-related antigen. The results have shown that MVD of invasive pituitary adenomas was significantly higher than that of noninvasive (P < 0.001). There was an association between the invasion of pituitary adenomas and Ki-67 LI (P = 0.039) or the expression of VEGF (P < 0.001) and MMP-9 (P < 0.001). But c-myc LI and bcl-2 expression have no association with invasiveness of pituitary adenomas (P = 0.061 vs. P = 0.201). On the other hand, there is an inverse relationship between nm23 expression and tumor invasion (P < 0.001). In conclusion, parasellar extension of pituitary adenomas through the medial wall of the cavernous sinus diagnosed at surgery, can be determined by radiology with sensitive gadolinium-enhanced MRI. Although our study has shown that MVD and the expression of VEGF, Ki-67, nm23 and MMP-9 have associations with invasiveness of pituitary adenomas, they are lack of specificity. These markers can only provide some useful informations on the therapeutic strategy of pituitary adenomas.

Radioresistance in carcinoma of the breast

Radiotherapy plays an important role in the management of breast cancer. Whilst its role in achieving local control following surgery in patients with early stage cancer is well established, there is still unclear evidence to explain the factors governing radioresistance in patients who develop recurrences both in the breast and axilla. Radiotherapy induces damage to the DNA. Various cell cycle damage check points and DNA damage repair pathways have been demonstrated. Ataxia telangiectasia mutant (ATM) kinase, which is a member of phosphatidylinositol-3 kinase (PI-3K) family appears to play a central role in DNA damage check point pathways. Over-expression of Insulin like growth factor-I receptor (IGF-IR), Human Epidermal Growth factor receptors (HERS), Vascular Endothelial growth factor (VEGF) on the cell surface and increased concentration of Epidermal Growth factor in the extracellular fluid have been associated with radioresistance. Specific genes such as p53, BRCA, Bcl-2 and chromosomal characteristics like telomere lengths have also been identified as playing significant roles in radiation responsiveness of a cell. This article reviews the current data on general principles of radiotherapy, the cellular mechanisms that operate in response to radiation damage and various molecular markers, intranuclear and extranuclear which have been demonstrated to influence radiation sensitivity in breast cancer cells.

Potential Predictive Value of Bcl-2 for Response to Tamoxifen in the Adjuvant Setting of Node-Positive Breast Cancer

Approximately 50% of patients with estrogen receptor (ER)-positive breast cancer (BC) and 70%-80% of patients with ER-positive and progesterone receptor (PgR)-positive BC respond to hormonal therapy. Additional predictive markers are needed. A group of 287 patients with ER- and/or PgR-positive tumors was selected from 804 patients previously enrolled in a multicenter phase III trial. Bcl-2 expression was evaluated and correlated with response to adjuvant tamoxifen and survival. Estrogen receptor and PgR were determined by biochemical means and Bcl-2 by immunohistochemistry. With a median follow-up of 76 months (95 relapses and 60 deaths), of the 287 patients with, 187 (65%) had Bcl-2-positive tumors and 78 of these patients received tamoxifen. Of the 100 patients with Bcl-2-negative disease, 51 received tamoxifen and 49 regular follow-up. Using patients treated with tamoxifen as a reference, a univariate analysis of disease-free interval for patients who did not receive tamoxifen showed a hazard ratio (HR) of 1.42 (95% CI, 0.82-2.44; P = 0.21) for patients with Bcl-2-positive disease and a HR of 1.05 (95% CI, 0.55-1.99; P = 0.89) for patients with Bcl-2-negative disease (P = 0.48). After adjusting for number of positive lymph nodes, degree of receptor and PgR positivity, and type of surgery, the HRs were 1.54 (95% CI, 0.87-2.73; P = 0.14) for Bcl-2-positive disease and 1.05 (95% CI, 0.52-2.11; P = 0.88) for Bcl-2-negative disease. Despite its being a retrospective nonrandomized study with a relatively low number of patients, our results suggest that Bcl-2 deserves further evaluation as a predictive factor of sensitivity to tamoxifen.

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.

Growth inhibition by the farnesyltransferase inhibitor FTI-277 involves Bcl-2 expression and defective association with Raf-1 in liver cancer cell lines

Farnesyltransferase inhibitors (FTIs) block the growth of tumor cells in vitro and in vivo with minimal toxicity toward normal cells. In general, inhibition of protein farnesylation results in G0/G1 cell cycle block, G2/M cell cycle arrest, or has no effect on cell cycle progression. One aspect of FTI biology that is poorly understood is the ability of these drugs to induce cancer cell growth arrest at the G2/M phase of cell cycle. In the present study, we investigated the effects of the farnesyltransferase inhibitor FTI-277 on two human liver cancer cell lines, HepG2 and Huh7. Treatment of these cells with FTI-277 inhibited Ras farnesylation in a dose-dependent manner. Both HepG2 and Huh7 cell growth was inhibited by FTI-277 and cells accumulated at the G2/M phase of the cell cycle. In HepG2 and Huh7 cells, FTI-277 induced an up-regulation of the cyclin-dependent kinase inhibitor p27(Kip1) without affecting the cellular levels of p53 and p21(Waf1). This event correlated with reduced activity of the cyclin-dependent kinase 2 and cyclin-dependent kinase 1. Moreover, increased expression of Bcl-2 protein was observed in HepG2 and Huh7 cells treated with FTI-277, and this was coincidental with reduced association between Raf-1 and Bcl-2. Finally, transient transfection of a dominant-negative Ras allele induced Bcl-2 expression and reduced Bcl-2/Raf-1 association demonstrating a requirement for Ras. Taken together, these findings show that increased expression of p27(Kip1) and Bcl-2 is concomitant with altered association between Ras, Raf-1 and Bcl-2 and suggest that this is responsible for the growth-inhibitory properties of FTI-277.

Alterations in adult rat heart after neonatal dexamethasone therapy

Glucocorticoid treatment in preterm babies to prevent chronic lung disease causes myocardial hypertrophy and increased myocardial protein content. Although these changes are thought to be transient, there is evidence that dexamethasone (DEX) induces permanent myocardial abnormalities as well. We investigated whether a therapeutic course of neonatal DEX in rat pups produces anatomic and biochemical alterations in rat hearts during adult life. Twenty-four rat pups were treated with DEX on d 1, 2, and 3 (0.5, 0.3, and 0.1 micro g/g) of life, with doses proportional to those used in preterm babies. Twenty-four control pups were treated with saline. At d 7, wk 8, or wk 45 (n = 8 per group) rats were killed. The anatomic parameters measured were body weight (Bw, in grams), heart (myocardial) weight (Hw, in milligrams), and the Hw:Bw ratio. Myocardial total protein (Prot) and DNA content were determined, and the Prot:DNA ratio was calculated. Histopathology and morphometry were performed on 45-wk-old rat hearts. In DEX-treated rat pups, at d 7, Bw and Hw were lower and the Hw:Bw ratio was increased. DNA content was lower, Prot higher, and Prot:DNA ratio was increased. In 8-wk-old rats Bw, Hw, DNA content, Prot content or Prot:DNA ratio did not differ between groups, but the Prot:DNA ratio still tended to be higher in DEX-treated rats. In 45-wk-old rats Hw and Hw:Bw ratio were significantly lower and Prot:DNA ratio higher in DEX-treated rats. Histopathologic analysis showed larger cardiomyocyte volume, length, and width, indicating hypertrophy, and increased collagen, indicating early degeneration of individual myocytes. In conclusion, neonatal DEX treatment in rat pups causes a permanent decrease in heart weight, as well as hypertrophy and early degeneration of cardiomyocytes during adulthood.

BCL2 antisense reduces prostate cancer cell survival following irradiation

Irradiation of the prostate, delivered as external beam radiation therapy (EBRT), is currently one of the few treatment options for localized prostate cancer. While it is relatively effective, the failure rate still remains unacceptably high with a 5-year biochemical failure rate of 10-40%. Utilizing genetically engineered LNCaP prostate cancer sublines that either overexpress Bcl2 (LNCaP/S22-d) or have down-regulated Bcl2 (LNCaP/AS17-f) we investigated the influence of this antiapoptotic protein on clonogenic survival following radiation. The radiation dose response curves (2-8 Gy) for the sublines differed significantly from the parental LNCaP (LNCaP/S22d: p < 0.001 and LNCaP/AS17-f: p = 0.008). The relative survival of the sublines revealed increased survival in the Bcl2 overexpressing cells, and decreased survival in the Bcl2 down-regulated cells. These data suggest a potentially important therapeutic approach for enhancing radiosensitivity in prostate tumors via antisense oligonucleotide or other drug therapies that down-regulate Bcl2. Strategies such as these likely hold the promise of enhancing the efficacy of EBRT by decreasing tumor cell survival, reducing the incidence of tumor recurrence and improving patient outcome.

Molecular prognostic indicators in breast cancer

Here we review a panel of oncogene products, proteases and markers of proliferation that have shown potential as prognostic indicators in primary breast cancer. The relative merits of specific genetic mutations as well as alterations at the protein level are discussed. Finally an assessment is made of the transfer of knowledge from the laboratory to the bed-side.

Telomerase activity and Bcl-2 expression in human breast cancer

AIMS

Telomerase is a ribonucleoprotein that synthesizes telomeres and plays an important role in cellular immortalization. Bcl-2 gene encodes for a mitochondrial protein thought to prevent apoptosis of normal cells. We previously reported telomerase activity in 74% of human invasive breast cancers and detected a significant association between telomerase activity and prognostic parameters such as nodal status, tumour size and cellular proliferation. We hypothesized that telomerase reactivation in human breast cancer was associated with increased immunohistochemical expression of Bcl-2.

METHODS

Bcl-2 immunohistochemical expression was determined in 25 infiltrating breast carcinomas with known telomerase activity (17 telomerase-positive and 8 telomerase-negative). The percentage of strongly and moderately stained tumour cells for Bcl-2 was determined by a breast pathologist who was blinded to telomerase data. Fisher's exact test was used to examine the association between telomerase activity and Bcl-2 expression.

RESULTS

The median percentage of strongly stained tumour cells was 50% for telomerase-positive tumours (range, 0--100%) and 45% for telomerase-negative tumours (range, 0--100%). Twelve (70%) of 17 telomerase-positive tumours expressed strong or moderate Bcl-2 staining in >50% of tumour cells compared with six (75%) of eight telomerase-negative tumours (P=1.0).

CONCLUSION

Telomerase reactivation seems to be independent of Bcl-2 protein expression in human breast cancer.

Down regulation of bcl2 expression in invasive ductal carcinomas is both estrogen- and progesterone-receptor dependent and associated with poor prognostic factors

In normal breast, Bcl2 is expressed in the non-pregnant and non-involuting mammary epithelium. The exact mechanism and the effect of the down regulation of the Bcl2 expression on breast cancer cells are not clearly defined. We compared down regulation as well as the persistent expression of Bcl2 with ER, PR, p53, and c-erb-B2 overexpression and clinicopathologic variables, and tumor stage in 11 cases of ductal carcinomas in situ (DCIS) and 44 cases of invasive ductal carcinomas (IDC) of Korean women by immunohistochemical studies. Bcl2 down regulation was found in 39% of IDC and in 18% of DCIS cases. In IDC, while persistent Bcl2 expression was displayed in 95% and 78.9% of ER and PR immunoreactive ones and 71.9 % of c-erb-B2 immunonegative ones. Seventeen cases of Bcl2 down regulated IDC had a significant correlation with ER negativity (94.1%), PR negativity, (76.5%), and high nuclear (61.1% is grade III) and histological grade (76% is grade III). However, in DCIS, no significant correlation between the Bcl2 expression and various parameters were obtained, probably due to small sample size. In conclusion, the Bcl2 expression was both ER and PR dependent and down regulation of Bcl2 in IDC was significantly correlated with poor prognostic factors.

Dysplastic changes in prophylactically removed Fallopian tubes of women predisposed to developing ovarian cancer

The aim of this study was to investigate the occurrence of (pre)neoplastic lesions in overtly normal Fallopian tubes from women predisposed to developing ovarian carcinoma. The presence of (pre)neoplastic lesions was scored in histological specimens from 12 women with a genetically determined predisposition for ovarian cancer, of whom seven tested positive for a germline BRCA1 mutation. A control group included 13 women. Immunohistochemistry was used to determine the expression of p21, p27, p53, cyclin A, cyclin D1, bcl-2, Ki67, HER-2/neu, and the oestrogen and progesterone receptors. Loss of heterozygosity (LOH) analysis on the BRCA1 locus was also assessed on dysplastic tissue by PCR studies. Of the 12 women with a predisposition for ovarian cancer, six showed dysplasia, including one case of severe dysplasia. Five harboured hyperplastic lesions and in one woman no histological aberrations were found in the Fallopian tube. No hyperplastic, dysplastic or neoplastic lesions were detected in the Fallopian tubes of control subjects. In the cases studied, morphologically normal tubal epithelium contained a higher proportion of Ki67-expressing cells (p=0.005) and lower fractions of cells expressing p21 (p<0.0001) and p27 (p=0.006) than in the control group. Even higher fractions of proliferating cells were found in dysplastic areas (p=0.07) and accumulation of p53 was observed in the severely dysplastic lesion. Expression patterns of other proteins studied, including the hormone receptors, were similar in cases and controls. One subject, a germline BRCA1 mutation carrier, showed loss of the wild-type BRCA1 allele in the severely dysplastic lesion. In conclusion, the Fallopian tubes of women predisposed to developing ovarian cancer frequently harbour dysplastic changes, accompanied by changes in cell-cycle and apoptosis-related proteins, indicating an increased risk of developing tubal cancer.

Can expression of apoptosis genes, bcl-2 and bax, predict survival and responsiveness to chemotherapy in node-negative breast cancer patients?

BACKGROUND

Although the status of the axillary lymph nodes is widely accepted to be associated with prognosis in breast cancer patients, there is a need for biomarkers to be analyzed as indicators of responsiveness to treatment. The objective of this study was to test the hypothesis that the expression of apoptosis genes, bcl-2 and bax, predicts survival and responsiveness to chemotherapy in node-negative breast cancer patients.

METHODS

One hundred thirty premenopausal women with primary breast carcinoma were studied for the expression of bcl-2 and bax genes. The relationship between the expression of bcl-2 and bax proteins and a series of markers of known prognostic value [such as tumor size, nuclear grade, receptors of the steroid hormones estrogen (ER) and progesterone (PgR)]. The association of these proteins with survival and responsiveness to chemotherapy was also examined.

RESULTS

Sixty (46%) and sixty-four (49%) breast cancer cases were found positive for bcl-2 and bax, respectively, as indicated by immunohistochemistry. A statistically significant association was found between expression of bcl-2 and tumor size (P = 0.001), low grade (grade I) (P = 0.002), positivity of ER (P = 0.001), positivity of PR (P = 0.03), and superior disease-free survival (DFS) (P = 0.04), and superior overall survival (OS) (P = 0.03). In contrast, no similar associations were observed for the bax gene. Overall, there was a trend toward an association between adjuvant chemotherapy and DFS (P = 0.08) and OS (P = 0.07). This trend became statistically significant when the patients were analyzed by individual gene expression. In bax-positive patients, chemotherapy improves 6-year DFS (P = 0.01) and OS (P = 0.03) while similar effects were not observed in the other subgroups of patients.

CONCLUSION

Our results indicated that bcl-2 expression is associated with a number of favorable prognostic factors and better clinical outcome, while bax expression seems to have positive predictive value for responsiveness to chemotherapy in lymph node-negative breast cancer patients.

Overexpression of bcl-2 inhibits sodium butyrate-induced apoptosis in Chinese hamster ovary cells resulting in enhanced humanized antibody production

Sodium butyrate (NaBu) can enhance the expression of genes from some of the mammalian promoters including cytomegalovirus (CMV) and simian virus 40 (SV40), but it can also inhibit cell growth and induce cellular apoptosis. Thus, the beneficial effect of using a higher concentration of NaBu on a foreign protein expression is compromised by its cytotoxic effect on cell growth. To overcome this cytotoxic effect of NaBu, a survival protein, human Bcl-2, was overexpressed in recombinant Chinese hamster ovary (CHO) cells (SH2-0.32), producing a humanized antibody directed against the S surface antigen of hepatitis B virus. When batch cultures of both control cells transfected with bcl-2-deficient plasmid (SH2-0.32-Deltabcl-2) and cells transfected with bcl-2 expression plasmid (14C6-bcl-2) were performed in the absence of NaBu, both cells showed similar profiles of cell viability and antibody production. Compared with the SH2-0.32-Deltabcl-2 culture, under the condition of NaBu addition at the exponential growth phase, overexpression of the bcl-2 gene considerably suppressed the NaBu-induced apoptosis of 14C6-bcl-2 by inhibiting caspase 3 activity and extending culture longevity by >2 days. As a result, the final antibody concentration of 14C6-bcl-2 culture was twofold higher than that of SH2-0.32-Deltabcl-2 culture in the presence of NaBu and threefold higher than that of SH2-0.32-Deltabcl-2 and 14C6-bcl-2 cultures in the absence of NaBu.

Bcl-2 retards cell cycle entry through p27(Kip1), pRB relative p130, and altered E2F regulation

Independent of its antiapoptotic function, Bcl-2 can, through an undetermined mechanism, retard entry into the cell cycle. Cell cycle progression requires the phosphorylation by cyclin-dependent kinases (Cdks) of retinoblastoma protein (pRB) family members to free E2F transcription factors. We have explored whether retarded cycle entry is mediated by the Cdk inhibitor p27 or the pRB family. In quiescent fibroblasts, enforced Bcl-2 expression elevated levels of both p27 and the pRB relative p130. Bcl-2 still slowed G(1) progression in cells deficient in pRB but not in those lacking p27 or p130. Hence, pRB is not required, but both p27 and p130 are essential mediators. The ability of p130 to form repressive complexes with E2F4 is implicated, because the retardation by Bcl-2 was accentuated by coexpressed E2F4. A plausible relevant target of p130/E2F4 is the E2F1 gene, because Bcl-2 expression delayed E2F1 accumulation during G(1) progression and overexpression of E2F1 overrode the Bcl-2 inhibition. Hence, Bcl-2 appears to retard cell cycle entry by increasing p27 and p130 levels and maintaining repressive complexes of p130 with E2F4, perhaps to delay E2F1 expression.

Proliferation, bcl-2 expression and angiogenesis in pituitary adenomas: relationship to tumour behaviour

The prediction of pituitary tumour behaviour, in terms of response to treatment from which can be derived optimal management strategies, is a challenge that has been approached using several different means. Angiogenesis in other tumour types has been shown to be correlated with poor response to treatment and tumour recurrence. The aim of this paper is to assess the role of measurements of cell proliferation and angiogenesis in predicting pituitary tumour behaviour. The proliferative capacity of the tumour was assessed using the Ki-67 labelling index (LI) while bcl-2 expression was used to assess anti-apoptotic pathways. The microvessel density (MVD) was assessed using antibodies to CD31 and factor VIII-related antigen, and with biotinylated ulex europaeus agglutinin I. There was no difference between Ki-67 LI and MVD of functionless tumours that recurred and those that did not, but bcl-2 expression was significantly lower in tumours that subsequently regrew. Macroprolactinomas had significantly higher LI than microprolactinomas and than all other tumours. Cell proliferation and angiogenesis were not related, showing that both processes are under different control mechanisms in pituitary tumours. In contrast there was a positive relationship between markers of angiogenesis and bcl-2 expression in prolactinomas, GH-secreting tumours and non-recurrent functionless tumours with higher levels of bcl-2 expression being found in the more vascular tumours. These findings may suggest that angiogenesis is related to the ability of tumour cells to survive rather than their proliferative activity.

Expression of Bcl-2, but not Bax, correlates with estrogen receptor status and tumor proliferation in invasive breast carcinoma

Bcl-2 and Bax have been demonstrated to be associated with apoptosis in breast carcinoma, and the ratio between Bax and Bcl-2 seems to be an important determinant of cellular sensitivity to induction of apoptosis. However, little information is available on the relationship between Bcl-2, Bax and the proliferative activity of breast carcinoma. The purpose of this study was to investigate the significance of apoptosis-related genes bcl-2 and Bax and their correlation with expression of p53, tumor proliferation defined by MIB-1 expression and estrogen receptor status. Immunohistochemistry was performed to determine Bcl-2, Bax, p53, estrogen receptor (ER) and MIB-1 expression in paraffin-embedded tissues of 177 invasive breast cancers. Expression of the anti-apoptotic protein Bcl-2 was not correlated with the pro-apoptotic Bax. Bcl-2 immunostaining displayed a negative correlation with increasing histologic grade, p53 and MIB-1 (P < 0.0001, P < 0.05 and P < 0.0001, respectively) and a positive correlation with rising ER immunostaining (r = 0.305, P < 0.0001). Conversely, expression of the apoptosis-promoting protein Bax did not correlate with increasing histologic grade, p53, MIB-1 or ER status. Neither Bcl-2 expression nor Bax expression correlated with age, menopausal status, tumor size, histologic type or axillary lymph node status. These results imply that Bcl-2 is associated with good prognostic markers and the regulation of Bax is complex and does not necessarily correlate with mutant p53 status in breast cancers.

Bcl-xL blocks activation of related adhesion focal tyrosine kinase/proline-rich tyrosine kinase 2 and stress-activated protein kinase/c-Jun N-terminal protein kinase in the cellular response to methylmethane sulfonate

The stress-activated protein kinase/c-Jun N-terminal protein kinase (JNK) is induced in response to ionizing radiation and other DNA-damaging agents. Recent studies indicate that activation of JNK is necessary for induction of apoptosis in response to diverse agents. Here we demonstrate that methylmethane sulfonate (MMS)-induced activation of JNK is inhibited by overexpression of the anti-apoptotic protein Bcl-xL, but not by caspase inhibitors CrmA and p35. By contrast, UV-induced JNK activity is insensitive to Bcl-xL. The results demonstrate that treatment with MMS is associated with an increase in tyrosine phosphorylation of related adhesion focal tyrosine kinase (RAFTK)/proline-rich tyrosine kinase 2 (PYK2), an upstream effector of JNK and that this phosphorylation is inhibited by overexpression of Bcl-xL. Furthermore, overexpression of a dominant-negative mutant of RAFTK (RAFTK K-M) inhibits MMS-induced JNK activation. The results indicate that inhibition of RAFTK phosphorylation by MMS in Bcl-xL cells is attributed to an increase in tyrosine phosphatase activity in these cells. Hence, treatment of Bcl-xL cells with sodium vanadate, a tyrosine phosphatase inhibitor, restores MMS-induced activation of RAFTK and JNK. These findings indicate that RAFTK-dependent induction of JNK in response to MMS is sensitive to Bcl-xL, but not to CrmA and p35, by a mechanism that inhibits tyrosine phosphorylation and thereby activation of RAFTK. Taken together, these findings support a novel role for Bcl-xL that is independent of the caspase cascade.