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

Clinicopathological insights and prognostic implications of DEK in association with apoptosis-regulating factors in ovarian cancer

PURPOSE

Ovarian cancer is one of the most common gynecologic malignancies of the present era. Dysregulation of apoptosis is considered as one of the most important factors for malignant transformation. DEK is a ubiquitous protein, and its downregulation induces apoptosis by altering BCL-2, BAX, and CASPASE-3 expressions. This study illuminates the cumulative clinical usefulness of DEK and related apoptotic proteins.

METHODS

A total of 119 patients were enrolled during 2021-2023. Demographic and clinicopathological data were recorded at presentation, and the follow-up was done till August 2024. Tissue samples were analyzed using immunohistochemistry and real-time PCR. A paired t test assessed gene expression between normal and malignant tissues of different treatment strategies. The crosstab was performed to find the association of DEK, BCL-2, BAX, and CASPASE-3 with clinicopathological features. Pearson's correlation was used to predict the association of DEK with other apoptotic factors. Survival and hazard risk were evaluated using log-rank and Cox regression.

RESULTS

The mean age of OC patients was 47.61 ± 12.5 years, presented with advanced stage (90.7%) and grade (85.3%). Most of them were post-menopausal (68.08%) and had unhygienic (76.5%) regular menstrual cycles (89.1%), and also experienced early pregnancy (61.8%). Some of these factors are related to a hazard risk (HR > 1). DEK and apoptotic proteins were upregulated in OC than in normal (p ≤ 0.01). DEK was positively correlated with BCL-2, BAX, and CASPASE-3, at both mRNA and protein levels, and only BAX showed significance in both (p ≤ 0.05). All the selected genes are independent risk factors for survival of OC (HR > 1), but only DEK and CASPASE-3 were significantly associated with poor survival (p ≤ 0.05).

CONCLUSIONS

Dysregulation of DEK, CASPASE-3, and BAX/BCL-2 is associated with poor overall survival. Further, this study highlights the correlation between DEK and key apoptotic regulators, emphasizing the critical role of DEK in OC prognosis.

Proteomic analysis reveals stage-specific reprogramed metabolism for the primary breast cancer cell lines MGSO-3 and MACL-1

Breast cancer is the most prevalent cancer in women worldwide. Its molecular subtypes are based on the presence/absence of estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2). MACL-1 and MGSO-3 are cell lines derived from primary tumor sites of patients diagnosed with luminal A subtype carcinoma (ER+ / PR+ / HER2-) and ductal carcinoma in situ (ER- / PR- / HER2+), respectively. However, these cell lines lost the expression of these markers over cell culturing, and both have triple-negative phenotypes (ER- / PR- / HER2-), which has the poorest prognosis. Here, we sought to study the proteome signature of MGSO-3 and MACL-1, comparing them with the epithelial cell line MCF-10A and the well-established metastatic-derived breast cancer cell line MDA-MB-231. Our results showed that proteins associated with the tricarboxylic acid cycle (TCA) and oxidative phosphorylation (OXPHOS) were upregulated in MGSO-3 and MACL-1 cells. These cell lines also showed upregulation of pro-apoptotic proteins when compared with MDA-MB-231. The molecular differences highlighted in this study may clarify the molecular basis behind cancer cells functioning and may reveal novel signatures across the breast cancer cell models. This article is protected by copyright. All rights reserved.

Effect of amygdalin on MCF-7, MDA-MB-231 and T-47D breast cancer cells in the in vitro study

Introduction

Amygdalin is a chemical compound found in the seeds of many edible plants. Different studies using cancer cell cultures in vitro indicate its potential anti-cancer activity. Various types of cancer cells showed different responses to different doses of amygdalin. This may suggest many in vitro models of the activity of this compound. The aim of the study was to evaluate the effect of amygdalin on MCF-7, MDA-MB-231, and T-47D breast cancer cells and on HFF-1 normal dermal fibroblasts (control cell culture) in vitro. Cell proliferation, viability, and the changes in mRNA transcript levels of basic proteins (BAX, caspase 3 and BCL-2) involved in apoptosis were analyzed.

Materials and Methods

MCF-7, MDA-MB-231, T-47D, and HFF-1 cell lines were purchased from the ATCC. Amygdalin derived from apricot kernels was purchased from Sigma-Aldrich. CVDE, WST-1, and LDH assays were used to evaluate the effects of amygdalin on cell proliferation and viability. Molecular evaluation of gene transcription levels was performed using the RT-qPCR technique.

Results

Amygdalin causes a dose-dependent decrease in proliferation and metabolic activity of MCF-7, MDA-MB-231, and T-47D cells in the in vitro cultures. In all cell cultures amygdalin affects the mRNA levels of pro-apoptotic BAX and caspase 3 proteins and anti-apoptotic BCL-2 protein.

Conclusions

Amygdalin anti-cancer activity may be selective in relation to different cell types. It seems that examined breast cancer cells are more sensitive to amygdalin than normal cells.

Zinc oxide nanoparticles enhance expression of maspin in human breast cancer cells

Toxic and apoptotic impacts of zinc oxide nanoparticle (ZNP) on different cancer cells have been reported. Maspin (a mammary serine protease inhibitor) as a tumor suppressor gene can inhibit tumor growth and metastasis. The expression of maspin is modulated by p53, Bcl-2 family genes, and estrogen receptor α (ER-α). This study aimed to assess the ZNP effects on maspin expression in MCF-7 cells (a breast cancer cell). Experimental groups (ZNP5, ZNP10, and ZNP20) received 5, 10, and 20 μM/mL ZNP for 48 h, respectively. 17-β-estradiol (E2) was used to evaluate the role of ER-α in the anticancer impact of ZNP. Cell viability, Annexin V, migration assay, gene expression, and western blotting methods were applied to evaluate ZNP effects on the MCF-7 cells. ZNP at the concentrations of 10 and 20 μM/mL could significantly decrease the viability and migration rate, and significantly increase apoptosis percentage in the MCF-7 cells. ZNP significantly enhanced mRNA expression and protein level of maspin in MCF-7 cells in a concentration-dependent way. ZNP concentration-dependently elevated mRNA expression and protein level of p53 and Bax while reduced the expression of Bcl-2 and ER-α. E2 promoted cancer cell growth by enhancing survival and migration rates. E2 treatment reduced mRNA expression and protein level of maspin and p53, and elevated Bcl-2 expression. ZNP considerably changed these events induced by E2 in the MCF-7 cells. It is concluded that the maspin overexpression is one of the toxic mechanisms of the ZNP on the ER-α-positive breast cancer cells, and can suppress the migration of these cells.

Cellular demolition: Proteins as molecular players of programmed cell death

Apoptosis, a well-characterized and regulated cell death programme in eukaryotes plays a fundamental role in developing or later-life periods to dispose of unwanted cells to maintain typical tissue architecture, homeostasis in a spatiotemporal manner. This silent cellular death occurs without affecting any neighboring cells/tissue and avoids triggering of immunological response. Furthermore, diminished forms of apoptosis result in cancer and autoimmune diseases, whereas unregulated apoptosis may also lead to the development of a myriad of neurodegenerative diseases. Unraveling the mechanistic events in depth will provide new insights into understanding physiological control of apoptosis, pathological consequences of abnormal apoptosis and development of novel therapeutics for diseases. Here we provide a brief overview of molecular players of programmed cell death with discussion on the role of caspases, modifications, ubiquitylation in apoptosis, removal of the apoptotic body and its relevance to diseases.

BCL2L12: a multiply spliced gene with independent prognostic significance in breast cancer

Background

Alternative splicing is a key process in carcinogenesis and, from a clinical aspect, holds great promises, as alternatively spliced variants have emerged as an untapped source of diagnostic and prognostic markers. Our aim was to assess the prognostic value of three recently recognized splice variants of the apoptosis-related gene, BCL2L12, in breast cancer (BC).

Methods

Total RNA was extracted from breast samples (150 BC and 80 tumor-adjacent normal tissues) and, following cDNA synthesis, a variant-specific qPCR was performed for the expressional quantification of BCL2L12 v.1, v.2 and v.4 transcript variants. Extensive statistical analysis, including bootstrap resampling and internal validation, was conducted in order to evaluate the associations of v.1, v.2 and v.4 expression with patients’ clinopathological and survival data.

Results

All examined BCL2L12 variants were significantly upregulated in BC specimens compared to their non-cancerous counterpart (v.1, p<0.001; v.2, p=0.009; v.4, p=0.004). Increased BCL2L12 v.4 mRNA expression was associated with markers of unfavorable prognosis namely, advanced tumor grade (p=0.002), ER- (p=0.015)/PR- (p<0.001) negativity, Ki-67-positivity (p=0.007) and high NPI (Nottingham prognostic index) score (p=0.033). Moreover, v.4 was significantly overexpressed in women with triple negative BC (TNBC) and HER2-positive tumors compared to those harboring luminal tumors (p<0.001). Survival analysis disclosed that BCL2L12 v.2 overexpression, as a continuous variable ([HR]=0.45, 95% CI=0.17–0.82, p=0.010), is a strong and independent marker of favorable prognosis for BC patients. Interestingly, v.2 retains its prognostic value in patients with Grade II/III ([HR]=0.21, 95% CI=0.05–0.57, p=0.006) or HER2-positive/TNBC tumors ([HR]=0.25, 95% CI=0.05–0.74, p=0.042).

Conclusions

BCL2L12 v.1, v.2, v.4 are aberrantly expressed in BC. Their expressional analysis by cost-effective molecular methods could provide a novel molecular tool for BC management.

ERα activity depends on interaction and target site corecruitment with phosphorylated CREB1

The two transcription factors estrogen receptor α (ERα) and cyclic adenosine monophosphate (cAMP)-responsive element binding protein 1 (CREB1) mediate different signals, bind different response elements, and control different transcriptional programs. And yet, results obtained with transfected reporter genes suggested that their activities may intersect. We demonstrate here that CREB1 stimulates and is necessary for ERα activity on a transfected reporter gene and several endogenous targets both in response to its cognate ligand estrogen and to ligand-independent activation by cAMP. The stimulatory activity of CREB1 requires its DNA binding and activation by phosphorylation, and affects the chromatin recruitment of ERα. CREB1 and ERα are biochemically associated and share hundreds to thousands of chromatin binding sites upon stimulation by estrogen and cAMP, respectively. These shared regulatory activities may underlie the anti-apoptotic effects of estrogen and cAMP signaling in ERα-positive breast cancer cells. Moreover, high levels of CREB1 are associated with good prognosis in ERα-positive breast cancer patients, which may be because of its ability to promote ERα functions, thereby maintaining it as a successful therapeutic target.

Rare somatic mutation of pro-apoptotic BAX and BAK genes in common human cancers

Aims and background

BAX and BAK are both pro-apoptotic Bcl-2 proteins and are essential for the pathway of intrinsic apoptosis. Apoptosis in cancer cells is frequently inactivated by somatic mutations. The aim of the study was to see whether somatic mutations of BAX and BAK genes are characteristics of common human cancers.

Methods

We analyzed somatic mutation of BAX and BAK genes in 47 gastric, 47 colorectal, 47 breast, 47 lung and 47 prostate carcinomas, and 47 acute leukemias by a polymerase chain reaction and single-strand conformation polymorphism assay.

Results

We identified BAX gene mutations in one colon (2.1%) and three gastric (6.4%) cancers. All of the mutations were frameshift mutations in the G8 repeat sequences and were detected in cancers with high microsatellite instability (36.4%). There was no evidence of BAX mutation in the other cancers, nor was somatic mutation of the BAK gene detected in the cancers.

Conclusions

Our data indicate that somatic mutation of BAX and BAK genes are rare in the common cancers (besides the cancers with high microsatellite instability) and suggest that neither BAX nor BAK mutation may causally be implicated in their tumorigenesis.

High Bak Expression Is Associated with a Favorable Prognosis in Breast Cancer and Sensitizes Breast Cancer Cells to Paclitaxel

Breast cancer has become the leading cause of cancer-related death among women. A large number of patients become resistant to drug chemotherapy. Paclitaxel (Taxol) is an effective chemotherapeutic agent used to treat cancer patients. Taxol has been widely used in human malignancies including breast cancer because it can stabilize microtubules resulting in cell death by causing an arrest during the G2/M phase of the cell cycle. Pro-apoptotic Bcl-2 antagonist killer 1 (Bak) plays an important role in Taxol-induced apoptosis in breast cancer. In our present study, we investigated the expression of the Bak protein and clinicopathological correlations in a large sample of breast cancer tissues by immunohistochemistry. We found that the percentage of high scores of Bak expression in breast cancer was significantly lower than that of the non-cancerous breast control tissue. In addition, lower Bak expression was positively associated with the clinical TNM stage of breast cancer with a significant decrease in overall survival compared with those with higher Bak expression especially in the Luminal and HER2 subtypes. Importantly, higher Bak expression predicted a favorable clinical outcome in the cases treated with Taxol indicated by a higher overall survival than that of patients with lower Bak expression especially in Luminal and HER2 subtypes. Furthermore, these results were confirmed in vitro since overexpression of Bak sensitized breast cancer cells to Taxol by inhibiting proliferation and promoting apoptosis; in contrast, downregulation of Bak through siRNA transfection inhibited Taxol induced-apoptosis. Therefore, our results demonstrate that Bak acts as a sensitive biomarker and favorable prognostic factor for Taxol treatment in breast cancer. The restoration of Bak expression would be therapeutically beneficial for Taxol resistant breast cancer patients.

Evaluation of Bax and Bak gene mutations and expression in breast cancer

Genetic analyses have provided evidence to suggest that Bax and Bak are the essential genes for apoptosis in mammalians cells. This study aimed to search for biomarkers in breast cancer to be used as prognostic markers for the disease. The Bak and Bax genes expressions were analyzed in 23 breast cancer patients by RT-PCR technique. SSCP technique was used to detect the mobility of the abnormal fragment in Bak exon 4. PCR for Bax promoter was digested with Tau 1 restriction enzyme to identify a single polymorphism G(-248)A. The expression of Bak gene is related to several clinical factors of breast cancer. The analysis of Bax RNA showed 4 isoforms of Bax with different distributions in the normal and tumor tissues. These isoforms were Bax α, d, δ, and ζ. Exon 4 had a normal pattern in all cases of breast cancer. There was a statistically significant difference in the frequency distribution of the G(-248)A genotypes in the breast cancer tissues with grade 3+high, T2 stage, lobular +other, and PR −ve subgroups. In this study, Bak expression seems to lead to development of breast cancer and affects the disease progression. Also, Bax d and Bax δ could be used as risk factor and biomarker for breast cancer with the distribution of G284A.

Peptides and peptide mimics as modulators of apoptotic pathways

Programmed cell death is an important and stringently controlled process. Aberrancies in its control mechanisms can lead to disease; overactive apoptosis can cause neurodegenerative disorders, whereas deficient apoptotic activity can lead to cancer. Therefore, controlling apoptotic pathways with peptides is showing increasing promise as a strategy in drug development.Programmed cell death or apoptosis is a noninvasive and strictly regulated cellular process required for organism development and tissue homeostasis. Deficiencies in apoptotic pathways are the source of many diseases such as cancer, neurodegenerative and autoimmune diseases, and disorders related to an inappropriate loss of cells such as heart failure, stroke, and liver injury. Validation of the various points of intervention as targets for drug development has been the subject of a vast number of studies. Peptides are essential tools for drug discovery, as well as preclinical and pharmaceutical drug development.

ABT-737 induces expression of the death receptor 5 and sensitizes human cancer cells to TRAIL-induced apoptosis

Because Bcl-2 family members inhibit the ability of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) to induce apoptosis, we investigated whether ABT-737, a small molecule Bcl-2 inhibitor, enhances TRAIL killing. We demonstrate that a combination of ABT-737 and TRAIL induced significant cell death in multiple cancer types, including renal, prostate, and lung cancers, although each agent individually had little activity in these tumor cells. All of these cell lines expressed the Mcl-1 protein that is known to block the activity of ABT-737 and TRAIL but did not block the synergy between these agents. However, Bax-deficient cell lines, including DU145 and HCT116 cells and those cell lines expressing low levels of TRAIL receptor, were resistant to apoptosis induced by these agents. To understand how ABT-737 functions to markedly increase TRAIL sensitivity, the levels of specific death-inducing signaling complex components were evaluated. Treatment with ABT-737 did not change the levels of c-FLIP, FADD, and caspase-8 but up-regulated the levels of the TRAIL receptor DR5. DR5 up-regulation induced by ABT-737 treatment occurred through a transcriptional mechanism, and mutagenesis studies demonstrated that the NF-kappaB site found in the DR5 promoter was essential for the ability of ABT-737 to increase the levels of this mRNA. Using luciferase reporter plasmids, ABT-737 was shown to stimulate NF-kappaB activity. Together, these results demonstrate that the ability of ABT-737 and TRAIL to induce apoptosis is mediated through activation of both the extrinsic and intrinsic pathways. Combinations of ABT-737 and TRAIL can be exploited therapeutically where antiapoptotic Bcl-2 family members drive tumor cell resistance to current anticancer therapies.

Role of mitochondria in tamoxifen-induced rapid death of MCF-7 breast cancer cells

Tamoxifen (Tam) is widely used in chemotherapy of estrogen receptor-positive breast cancer. It inhibits proliferation and induces apoptosis of breast cancer cells by estrogen receptor-dependent modulation of gene expression, but recent reports have shown that Tam (especially at pharmacological concentrations) has also rapid nongenomic effects. Here we studied the mechanisms by which Tam exerts rapid effects on breast cancer cell viability. In serum-free medium 5-7 microM Tam induced death of MCF-7 and MDA-MB-231 cells in a time-dependent manner in less than 60 min. This was associated with release of mitochondrial cytochrome c, a decrease of mitochondrial membrane potential and an increase in production of reactive oxygen species (ROS). This suggests that disruption of mitochondrial function has a primary role in the acute death response of the cells. Accordingly, bongkrekic acid, an inhibitor of mitochondrial permeability transition, was able to protect MCF-7 cells against Tam. Rapid cell death induction by Tam was not associated with immediate activation of caspase-9 or cleavage of poly (ADP-ribose) polymerase. It was not blocked by the caspase inhibitor z-Val-Ala-Asp-fluoromethylketone either. Diphenylene ionodium (DPI), an inhibitor of NADPH oxidase, was able to prevent Tam-induced cell death but not cytochrome c release, which suggests that ROS act distal to cytochrome c. The pure antiestrogen ICI 182780 (1 microM) could partly oppose the effect of Tam in estrogen receptor positive MCF-7 cells, but not in estrogen receptor negative MDA-MB-231 cells. Pre-culturing MCF-7 cells in the absence of 17beta-estradiol (E(2)) or in the presence of a low Tam concentration (1 microM) made the cells even more susceptible to rapid death induction by 5 or 7 microM Tam. This effect was associated with decreased levels of the anti-apoptotic proteins Bcl-X(L) and Bcl-2. In conclusion, our results demonstrate induction of a rapid mitochondrial cell death program in breast cancer cells at pharmacological concentrations of Tam, which are achievable in tumor tissue of Tam-treated breast cancer patients. These mechanisms may contribute to the ability of Tam therapy to induce death of breast cancer cells.

The ERBB4/HER4 intracellular domain 4ICD is a BH3-only protein promoting apoptosis of breast cancer cells

ERBB4/HER4 (referred to here as ERBB4) is a unique member of the epidermal growth factor receptor (EGFR) family of receptor tyrosine kinases. In contrast to the other three members of the EGFR family (i.e., EGFR, ERBB2/HER2/NEU, and ERBB3), which are associated with aggressive forms of human cancers, ERBB4 expression seems to be selectively lost in tumors with aggressive phenotypes. Consistent with this observation, we show that ERBB4 induces apoptosis when reintroduced into breast cancer cell lines or when endogenous ERBB4 is activated by a ligand. We further show that ligand activation and subsequent proteolytic processing of endogenous ERBB4 results in mitochondrial accumulation of the ERBB4 intracellular domain (4ICD) and cytochrome c efflux, the essential and committed step of mitochondrial regulated apoptosis. Our results indicate that 4ICD is functionally similar to BH3-only proteins, proapoptotic members of the BCL-2 family required for initiation of mitochondrial dysfunction through activation of the proapoptotic multi-BH domain proteins BAX/BAK. Similar to other BH3-only proteins, 4ICD cell-killing activity requires an intact BH3 domain and 4ICD interaction with the antiapoptotic protein BCL-2, suppressed 4ICD-induced apoptosis. Unique among BH3-only proteins, however, is the essential requirement of BAK but not BAX to transmit the 4ICD apoptotic signal. Clinically, cytosolic but not membrane ERBB4/4ICD expression in primary human breast tumors was associated with tumor apoptosis, providing a mechanistic explanation for the loss of ERBB4 expression during tumor progression. Thus, we propose that ligand-induced mitochondrial accumulation of 4ICD represents a unique mechanism of action for transmembrane receptors, directly coupling a cell surface signal to the tumor cell mitochondrial apoptotic pathway.

Neurons exclusively express N-Bak, a BH3 domain-only Bak isoform that promotes neuronal apoptosis

Bak is generally recognized as a multidomain, pro-apoptotic member of the Bcl-2 family. Bak and Bax are functionally redundant in non-neuronal cells and represent a mitochondrial convergence point for cell death signaling pathways. This functional redundancy, however, may not exist in neurons in which the single deletion of Bax is sufficient to confer protection against a variety of cytotoxic insults. In the present study, we demonstrate that postnatal cortical and cerebellar granule neurons exclusively express an alternatively spliced, BH3 domain-only form of Bak (N-Bak), whereas astrocytes express only the full-length, multidomain form. Overexpression of N-Bak promotes Bax translocation in HeLa cells and induces neuronal cell death in cortical, hippocampal, and cerebellar granule neurons in a Bax-dependent manner. N-Bak interacts with Bcl-XL but not BAX, suggesting an indirect mechanism for promoting Bax translocation to the mitochondria. N-Bak message and protein levels are elevated in cortical neurons in response to DNA damage, and subsequent induction of neuronal death is significantly delayed by expressing a full-length Bak antisense plasmid. These results demonstrate that postnatal neurons solely express a BH3 domain-only form of Bak, which contributes to DNA damage-induced neuronal apoptosis. The absence of full-length Bak expression explains the near exclusive requirement for Bax in neuronal apoptosis.

Estrogen and growth factor signaling pathway: basic approaches for clinical application

Estrogen and its receptor play important roles in genesis and malignant progression of estrogen-dependent cancers, together with various growth factors. Functional cross-talk between estrogen-signaling and growth factor-mediated signaling pathways has been reported. Firstly, we show an example of the cross-talk that may alter the effect of antagonist on the breast and endometrial cancer cell growth. Our observations suggest that the constitutively activated MAP kinase-signaling pathway in endometrial cancer cells might enhance the transcriptional activity of ERalpha via phosphorylation of AF-1 domain. This mechanism may cause the growth stimulative effect of tamoxifen on the endometrium. Secondly, we show our recent study for comprehensive understanding of estrogen-signaling pathway using cDNA microarray. According to the results of the expression profiling of estrogen-responsive genes in ER-positive breast cancer cells using large-scale cDNA microarray, the custom-made cDNA microarray, on which only estrogen-responsive genes were loaded, was produced. Using this microarray consisting of the narrowed gene subset, we analyzed estrogen responsiveness of various cell lines and effect of estrogen antagonists. Aim of this study is not only to address the molecular mechanisms of estrogen-dependent growth of breast cancer, but also to develop the new diagnostic tools for responsiveness to hormone therapy of primary breast cancer patients. Finally, in order to understand the local tumor biology including stroma-cancer interaction, we recently developed the new analytical system using ERE-GFP introduced into breast cancer cells. Several observations indicated that these reporter cells were useful for assessment of stimulative effects of stroma cells adjacent to breast cancer on the estrogen-signaling pathway. These studies may provide not only new clues for elucidation of the molecular mechanisms of estrogen-dependent growth of breast cancer, but also assessment of anti-estrogen responses of individual breast cancer for patient-tailored hormone therapy.

Estrogen receptor (ER) beta1 and ERbetacx/beta2 inhibit ERalpha function differently in breast cancer cell line MCF7

Estrogen receptor (ER) alpha plays an important role in the proliferation and progression of breast cancer. In order to explore the function of wild-type ERbeta (ERbeta1) and its variant form, ERbetacx/beta2, stable transformants of ERalpha-positive breast cancer MCF7 cells with ERbeta1 or ERbetacx/beta2 expression vector were established. Constitutive expression of ERbeta1 or ERbetacx/beta2 reduced the S phase population of the cell cycle in dish culture and the number of colonies in an anchorage-independent assay. DNA-protein complexes of ERE with nuclear extracts from ERbeta1 transformants were observed in the electrophoretic mobility shift assay, while no complex was observed for ERbetacx/beta2 transformants. Reporter gene assay using estrogen-responsive element (ERE)-luciferase showed less responsiveness to estrogen in these transformants compared with parental cells. Endogenous mRNA expression of two known estrogen-responsive genes, cathepsin D and IGFBP4, was weakly induced by estrogen in ERbeta1 and ERbetacx/beta2 transformants compared with parental cells. A comprehensive gene expression analysis using our custom-made cDNA microarray showed that MCF7 and ERbeta1 transformants had a similar gene expression profile, whereas ERbetacx/beta2 showed a distinct profile from others. These results indicate that ERbeta1 and ERbetacx/beta2 inhibit ERalpha function differently in MCF7 cells.

Intrinsic and extrinsic pathways signaling during HIV-1 mediated cell death

Infection with human immunodeficiency virus (HIV) is characterized by the gradual depletion of CD4+ T lymphocytes. The incorporation of the concept of apoptosis as a rationale to explain progressive T cell depletion has led to growing research in this field during the last 10 years. In parallel, the biochemical pathways implicated in programmed cell death have been extensively studied. Thus, the influence of mitochondrial control in the two major apoptotic pathways-the extrinsic and intrinsic pathways-is now well admitted. In this review, we summarized our current knowledge of the different pathways involved in the death of T cells in the course of HIV infection.

Nonredundant role of Bax and Bak in Bid-mediated apoptosis

Animal models suggest that Bax and Bak play an essential role in the implementation of apoptosis and as a result can hinder tumorigenesis. We analyzed the expression of these proteins in 50 human glioblastoma multiforme (GBM) tumors. We found that all the tumors expressed Bak, while three did not express Bax. In vitro, Bax-deficient GBM (BdGBM) exhibited an important resistance to various apoptogenic stimuli (e.g., UV, staurosporine, and doxorubicin) compared to the Bax-expressing GBM (BeGBM). Using an antisense strategy, we generated Bak(-) BeGBM and Bak(-) BdGBM, which enabled us to show that the remaining sensitivity of the BdGBM to apoptosis was due to the overexpression of Bak. Bax/Bak single or double deficiency had no influence on either the clonogenicity or the growth of tumors in Swiss nude mice. Of note, Bak(-) BeGBM cells were resistant to apoptosis induced by caspase 8 (C8) but not to that induced by granzyme B (GrB). Cells lacking both Bax and Bak (i.e., Bak(-) BdGBM) were completely resistant to all stimuli including the microinjection of C8 and GrB. We show that GrB-cleaved Bid and C8-cleaved Bid differ in size and utilize preferentially Bax and Bak, respectively, to promote cytochrome c release from mitochondria. Our results suggest that Bax deficiency is compensated by an increase of the expression of Bak in GBM and show, for the first time in human cancer, that the double Bax and Bak deficiency severely impairs the apoptotic program.

Paradoxical role of apoptosis in tumor progression

Tumors frequently acquire resistance to apoptosis that is expected to contribute to malignant phenotype and reduce sensitivity to treatment. In fact, inactivation of p53 tumor suppressor gene resulting in suppression of apoptosis serves as a negative prognostic marker. Surprisingly, expression of a strong anti-apoptotic protein Bcl-2, another mechanism to avoid apoptosis, was found to be associated with a favorable prognosis. This paradoxical anti-progressor function of Bcl-2 has been explained in literature based on the negative effect of Bcl-2 on cell proliferation. Here, by analyzing accumulated experimental and clinical data, we provide evidence supporting another hypothesis that defines apoptosis as an accelerator of tumor progression. The mechanism of anti-progressor function of Bcl-2 is based on creation of tumors that maintain control of genomic stability by eliminating selective advantages for the cells that acquire resistance to apoptosis through loss of p53. Thus, inhibition of apoptosis does not lead to loss of genomic stability and creates tumor environment that no longer supports further tumor progression and inhibitors of apoptosis can be considered as factors suppressing tumor progression.

Estrogen receptor-mediated effects of tamoxifen on human endometrial cancer cells

Tamoxifen is an estrogen receptor (ER)-antagonist that is widely used for the treatment of breast cancer, although it increases the risk of endometrial cancer. The mechanism mediating the stimulatory effect of tamoxifen on endometrial cancer is presently unknown. In this study we examined the effects of tamoxifen on Ishikawa 3H-12 endometrial cancer cells and MCF-7 breast cancer cells. Ishikawa cell growth was stimulated by 4-hydroxytamoxifen and accompanied by increased transcriptional activity of the endogenous ER. These stimulatory effects did not occur in MCF-7 cells. The relative transcriptional activity of the activation function (AF) 1 domain of ERalpha compared with that of the AF2 domain was 4-fold higher in Ishikawa cells than in MCF-7 cells. Mitogen-activated protein (MAP) kinase, which stimulates the transcriptional activity of AF1, was constitutively activated in Ishikawa cells, but not in MCF-7 cells. These observations suggest that the constitutively activated MAP kinase-signaling pathway in Ishikawa cells enhances the transcriptional activity of ERalpha via the AF1 domain. This ERalpha activation pathway may be involved in the stimulatory effect of tamoxifen on the development and/or progression of endometrial cancer.

A role for mitochondrial Bak in apoptotic response to anticancer drugs

In the present study a clonal Jurkat cell line deficient in expression of Bak was used to analyze the role of Bak in cytochrome c release from mitochondria. The Bak-deficient T leukemic cells were resistant to apoptosis induced by UV, staurosporin, VP-16, bleomycin, or cisplatin. In contrast to wild type Jurkat cells, these Bak-deficient cells did not respond to UV or treatment with these anticancer drugs by membranous phosphatidylserine exposure, DNA breaks, activation of caspases, or release of mitochondrial cytochrome c. The block in the apoptotic cascade was in the mitochondrial mechanism for cytochrome c release because purified mitochondria from Bak-deficient cells failed to release cytochrome c or apoptosis-inducing factor in response to recombinant Bax or truncated Bid. The resistance of Bak-deficient cells to VP-16 was reversed by transduction of the Bak gene into these cells. Also, the cytochrome c releasing capability of the Bak-deficient mitochondria was restored by insertion of recombinant Bak protein into purified mitochondria. Following mitochondrial localization, low dose recombinant Bak restored the mitochondrial release of cytochrome c in response to Bax; at increased doses it induced cytochrome c release itself. The function of Bak is independent of Bid and Bax because recombinant Bak induced cytochrome c release from mitochondria purified from Bax(-/-), Bid(-/-), or Bid(-/-) Bax(-/-) mice. Together, our findings suggest that Bak plays a key role in the apoptotic machinery of cytochrome c release and thus in the chemoresistance of human T leukemic cells.

Expression, function, and clinical implications of the estrogen receptor beta in human lung cancers

The higher frequency of human lung adenocarcinoma in females than in males, strongly suggests the involvement of gender dependent factors in the etiology of this disease. This is the first investigation of estrogen receptor (ER) beta in human lung. Immunohistochemical staining revealed ERbeta expression in normal lung and in atypical adenomatous hyperplasia (AAH), considered as a precancerous lesion for adenocarcinomas. Adenocarcinomas showed significantly higher expression of ERbeta than squamous cell carcinomas. On the contrary, ERalpha expression was not detected in all cases. The functional integrity of ERbeta such as the binding ability to estrogen responsive element (ERE) and transcriptional activity was confirmed using a human lung cancer cell line, RERF-LC-OK. Colony formation of this cell was significantly reduced in the presence of pure antiestrogen. We conclude that ERbeta, but not ERalpha, is present in lung tissues with an important physiological function in normal lung. Furthermore, ERbeta may play a role in growth and development of adenocarcinomas.

Cisplatin induces the proapoptotic conformation of Bak in a deltaMEKK1-dependent manner

In a panel of four human melanoma cell lines, equitoxic doses of cisplatin induced the proapoptotic conformation of the Bcl-2 family protein Bak prior to the execution phase of apoptosis. Because cisplatin-induced modulation of the related Bax protein was seen in only one cell line, a degree of specificity in the signal to Bak is indicated. Little is known about upstream regulation of Bak activity. In this study, we examined whether the apoptosis-specific pathway mediated by a kinase fragment of MEKK1 (DeltaMEKK1) is involved in the observed Bak modulation. We report that expression of a kinase-inactive fragment of MEKK1 (dominant negative MEKK [dnMEKK]) efficiently blocked cisplatin-induced modulation of Bak and cytochrome c release and consequently also reduced DEVDase activation and nuclear fragmentation. Accordingly, expression of a kinase-active MEKK1 fragment (dominant positive MEKK) was sufficient to induce modulation of Bak in three cell lines and to induce apoptosis in two of these. dnMEKK did not block cisplatin-induced c-Jun N-terminal kinase (JNK) activation, in agreement with a specifically proapoptotic role for the DeltaMEKK1 pathway. Finally, we show that reduction of Bak expression by antisense Bak reduced cisplatin-induced loss of mitochondrial integrity and caspase cleavage activity in breast cancer cell lines. In summary, we have identified Bak as a cisplatin-regulated component downstream in a proapoptotic, JNK-independent DeltaMEKK1 pathway.