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Bcl-2 family proteins regulate apoptosis in animals. This protein family includes several homologous proteins and a collection of other proteins lacking sequence similarity except for a Bcl-2 homology (BH)3 motif. Thus, membership in the Bcl-2 family requires only one of the four BH motifs. On this basis, a growing number of diverse BH3-only proteins are being reported. Although compelling cell biological and biophysical evidence validates many BH3-only proteins, claims of significant BH3 sequence similarity are often unfounded. Computational and phylogenetic analyses suggest that only some BH3 motifs arose by divergent evolution from a common ancestor (homology), whereas others arose by convergent evolution or random coincidence (homoplasy), challenging current assumptions about which proteins constitute the extended Bcl-2 family., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Most cells express a variety of both anti-apoptotic and pro-apoptotic Bcl-2 proteins and the interaction within this family dictates whether a cell survives or dies. The dysregulation of the anti-anti-apoptotic Bcl-2 family members is one of the defining features of cancer cells in comparison to normal cells, and significantly contributes to the resistance of cancer cells to current treatment modalities. This anti-apoptotic subfamily of proteins is now a major target in the development of new methods to improve treatment outcomes for cancer patients. Several drugs directed at inhibiting Bcl-2 and related anti-apoptotic proteins have been developed with some showing considerable promise in the clinic. This Review presents the current knowledge of the role of the anti-apoptotic Bcl-2 family in cancer cells, as well as current and future perspectives on targeting this subfamily of proteins for therapeutic intervention in human malignancies. This article is part of a Special Issue entitled "Apoptosis: Four Decades Later".

Bcl-2 family proteins have long been implicated in the pathology of chronic lymphocytic leukaemia (CLL). Indeed, a number of these proteins have been shown to have prognostic importance in this disease. The precise ways in which these proteins impact upon CLL and the ways in which they are regulated remain incompletely resolved. However, significant advances have been recently made in our understanding of how these proteins are controlled by genetic, epigenetic and microenvironmental cues. Furthermore, major progress has been made in trying to target these proteins therapeutically. Here we review the current knowledge about this family of apoptosis-regulating proteins and how they impact upon drug resistance and disease progression. We also summarise evolution in the development of Bcl-2 family inhibitors for the treatment of CLL and other cancers., (Copyright 2010 Elsevier Ltd. All rights reserved.)

A critical regulator of the apoptotic machinery is the Bcl-2 family proteins whose over expression confers a protective effect on malignant cells against death signals of apoptosis. Cancer cells that are resistant to various anti-cancer drugs and treatment regimen are found to over express these Bcl-2 proteins such as Bcl-2, Bcl-X(L), Mcl-1, Bcl-w, and A1/Bfl1. In recent years there has been an exponential growth in the identification as well as synthesis of non-peptidic cell permeable small-molecule inhibitors (SMIs) of protein-protein interaction. The focus of this article is on inhibitors of anti-apoptotic protein Bcl-2. This review summarizes an up to date knowledge of the available SMIs, their mode of action as well as their current status in preclinical as well as clinical development., ((c) 2008 Wiley-Liss, Inc.)

Apoptosis regulators play one of the most critical roles in tumorigenesis, and an imbalance between cell proliferation and apoptosis may contribute to tumor progression. HRK was itself originally identified as a proapoptotic gene induced by diminished levels of cytokine in hematopoietic cells and cultured neurons and repressed by the expression of death-repressor proteins. A few analyses of HRK protein expression in primary central nervous system lymphomas have been performed, and little is known about the epigenetic or post-transcriptional mechanisms that may participate in HRK inactivation. Here we show the data on the 5'-CpG methylation status, loss of heterozygosity on 12q13.1 and its association with HRK expression in human malignancies, including prostate cancers, astrocytic tumors and primary central nervous system lymphomas. Aberrant methylation of CpG islands within the promoter is an epigenetic event largely responsible for the silencing of the HRK gene and subsequent low apoptotic counts in our series of malignancies. Inactivation of HRK apparently occurs in a substantial proportion of all tumor phenotypes and, as a potential proapoptotic gene, HRK may contribute to the development and progression of many human cancers.

Rheumatoid arthritis (RA) is a debilitating disease, resulting in the destruction of bone and cartilage, and in the permanent disfigurement of joints. Although the precise cause of RA is currently unresolved, it has become clear that the damaging effects are a result of the toxic milieu caused by an influx of inflammatory cells and the resulting heightened proinflammatory state within the joint. As the amount of literature suggesting that this preponderance of cells is a result of decreased local apoptosis in the joint continues to increase, in this review, we describe how Bcl-2 family pro-apoptotic BH3-only proteins, particularly Bim and Bid, could act to protect against the development of the disease. We also suggest a role for BH3-mimetic drugs as potential therapeutics in the treatment of RA.

The Bcl-2 family of proteins controls the mitochondrial pathway to apoptosis. It consists of pro-survival and pro-apoptotic members, and their interactions decide whether apoptogenic factor confined to the mitochondrial intermembrane space can leak to the cytosol. Despite the intense efforts to understand the molecular mechanisms that lead to the permeabilization of the mitochondrial membrane, this particular issue remains a matter of intense controversy. It is well accepted that pro-apoptotic Bax and Bak are directly responsible for the damage to the mitochondria, but pro-survival family members prevent them from doing so. It is also accepted that stress signals activate selected Bcl-2 homology (BH)3-only proteins. But do these BH3-only proteins bind and activate Bax and Bak directly, or do they inhibit the pro-survival family members?

Defects in the apoptotic signaling cascades contribute to the poor therapeutic response of malignant gliomas. As glioblastomas are characterized by high expression levels of anti-apoptotic Bcl-2 family proteins, we studied the effects of the novel Bcl-2 inhibitor, ABT-737, on malignant glioma cells. ABT-737 treatment released the pro-apoptotic Bax protein from its binding partner Bcl-2 and potently induced apoptotic cell death in glioblastoma cells in vitro and in vivo. The local administration of ABT-737 prolonged the survival in an intracranial glioma xenograft model. Downregulation of Mcl-1 and overexpression of Bcl-2 sensitized the cells to ABT-737-mediated apoptosis. Moreover, ABT-737 potentiated the cytotoxicity of the chemotherapeutic drugs vincristine and etoposide, and of the death ligand TRAIL. As glioma stem cells may play a crucial role for the tumor progression and the resistance to treatment in glioblastomas, we investigated the effects of ABT-737 on the subpopulation of glioma cells exhibiting stem cell characteristics. Inhibition of proliferation and induction of apoptosis by ABT-737 were less efficient in glioma stem cells than in non-stem cell-like glioma cells. As the resistance of glioma stem cells was associated with high Mcl-1 expression levels, ABT-737 treatment combined with downregulation of Mcl-1 could represent a promising novel approach in glioblastoma treatment.

T lymphocyte development and function are tightly regulated by the intrinsic death pathway through members of the Bcl-2 family. Genetic studies have demonstrated that the Bcl-2 family member Mcl-1 is an important anti-apoptotic protein in the development of multiple cell types including T lymphocytes. However, the expression pattern and anti-apoptotic roles of Mcl-1 in T lymphocytes at different developmental stages remain to be fully determined. In this study, we examined the expression pattern of Mcl-1 in different populations of T cells at the single-cell level and found that Mcl-1 protein is constitutively expressed in all T cell populations and up-regulated upon TCR stimulation. We then investigated the role of Mcl-1 in the survival of these different populations by conditionally deleting Mcl-1 at various T cell stages. Our results show that Mcl-1 is required for the survival of double-negative and single-positive thymocytes as well as naive and activated T cells. Furthermore, we demonstrate that Mcl-1 functions together with Bcl-xL to promote double-positive thymocyte survival. Thus, Mcl-1 is a critical anti-apoptotic factor for the survival of T cells at multiple stages in vivo.

Objectives: Epstein-Barr virus (EBV) transforms B-cells into immortalized lymphoblastoid cells (LCLs) by triggering signaling pathways that lead to activation of multiple transcription factors and anti-apoptotic proteins, including NF-kappaB and Bcl-2, respectively. Since proteasome inhibition suppresses NF-kappaB activity, we sought to determine whether the proteasome inhibitor, bortezomib, alone or in combination with Bcl-2 inhibition, has potential as a therapeutic strategy in EBV-driven B-cell neoplasms., Methods: We evaluated the effects of bortezomib in LCLs in vitro, in the presence and absence of the small molecular inhibitor of Bcl-2, HA14-1, on proliferation, apoptosis, caspase activation, and expression of Bcl-2 family members, and in vivo in the severe combined immunodeficiency (SCID) model of EBV+ lymphoproliferative disease., Results: Bortezomib inhibited proliferation, stimulated apoptosis, and activated caspases-3 and -9 in a dose-dependent manner in LCLs. In vivo, bortezomib completely abrogated development of EBV+ lymphoproliferative disease in LCL-bearing SCID mice. When HA14-1 was added to bortezomib in vitro, we observed a synergistic anti-proliferative effect and enhancement of apoptosis and caspase activation, including activation of caspase-8, in LCLs. These events were associated with modulation of expression of Bcl-2 family members towards a pro-apoptotic profile with translocation of cytochrome C from mitochondria to cytoplasm., Conclusions: These studies demonstrated that bortezomib mediates anti-tumor effects in EBV-associated lymphoproliferations both in vitro and in vivo, and that its anti-proliferative and apoptotic effects are synergistically enhanced in the presence of a Bcl-2 inhibitor. These findings support further investigation of bortezomib in EBV+ lymphoproliferative diseases, and suggest that bortezomib in combination with Bcl-2 antagonists represents a potential therapeutic strategy for EBV-driven B-cell neoplasms.

Physiological cell turnover is under the control of a sharp and dynamic balance of different homeostatic mechanisms such as the equilibrium between cell proliferation and cell death. These mechanisms play an important role in maintaining normal tissue function and architecture. It is well known that apoptosis is the prevalent mode of physiological cell loss in most tissues. Steroid hormones like glucocorticoids have been identified as key signals controlling cell turnover by modulating programmed cell death in a tissue- and cell-specific manner. In this sense, several reports have demonstrated that glucocorticoids are able to induce apoptosis in cells of the hematopoietic system such as monocytes, macrophages, and T lymphocytes. In contrast, they protect against apoptotic signals evoked by cytokines, cAMP, tumor suppressors, in glandular cells such as the mammary gland epithelia, endometrium, hepatocytes, ovarian follicular cells, and fibroblasts. Although several studies have provided significant information on hormone-dependent apoptosis in an specific tissue, a clearly defined pathway that mediates cell death in response to glucocorticoids in different cell types is still misunderstood. The scope of this review is held to those mechanisms by which glucocorticoids control apoptosis, emphasizing tissue-specific expression of genes that are involved in the apoptotic pathway.

Human cancers have multiple alterations in cell signaling pathways that promote resistance to cytotoxic therapy such as X rays. Parthenolide is a sesquiterpene lactone that has been shown to inhibit several pro-survival cell signaling pathways, induce apoptosis, and enhance chemotherapy-induced cell killing. We investigated whether parthenolide would enhance X-ray-induced cell killing in radiation resistant, NF-kappaB-activated CGL1 cells. Treatment with 5 microM parthenolide for 48 to 72 h inhibited constitutive NF-kappaB binding and cell growth, reduced plating efficiency, and induced apoptosis through stabilization of p53 (TP53), induction of the pro-apoptosis protein BAX, and phosphorylation of BID. Parthenolide also enhanced radiation-induced cell killing, increasing the X-ray sensitivity of CGL1 cells by a dose modification factor of 1.6. Flow cytometry revealed that parthenolide reduced the percentage of X-ray-resistant S-phase cells due to induction of p21 waf1/cip1 (CDKN1A) and the onset of G1/S and G2/M blocks, but depletion of radioresistant S-phase cells does not explain the observed X-ray sensitization. Further studies demonstrated that the enhancement of X-ray-induced cell killing by parthenolide is due to inhibition of split-dose repair.

Mitochondria play a central role not only in energy generation but also for apoptosis. A key step in mitochondrial apoptosis is the release of mitochondrial proteins, most importantly cytochrome c. This release is orchestrated by the pro- and anti-apoptotic members of the Bcl-2 protein family. The functions of these Bcl-2 family members are clear in terms of order and of principle: the pro-apoptotic BH3-only protein group contains the triggers, which cause the activation of the effectors Bax and Bak, while the anti-apoptotic Bcl-2-like proteins prevent this activation. However, the molecular details are still insufficiently clear and the proposed models have certain gaps and are partly contradictory. We have recently presented evidence that targeting to mitochondria of at least one BH3-only protein is essential for its pro-apoptotic functions. Here we discuss how this mechanism might fit into and expand existing models and speculate about the potential implications of this finding.

Background: Bcl2 is an important prognostic parameter in human breast cancer. However, the evaluation of Bcl2 expression by immunohistochemistry is carried out using arbitrary scoring criteria. In the present study, we evaluated the clinical relevance of a novel, semiquantitative classification of the Bcl2 immunostaining based on both the distribution and the intensity of the staining reaction., Patients and Methods: The proposed classification was first validated in 69 breast cancer specimens by comparing the Bcl2 immunostaining with the Bcl2 messenger RNA (mRNA) levels evaluated by real-time RT-PCR. Since a highly significant association was found between protein and mRNA for Bcl2, the immunohistochemical scoring system was applied to 442 patients with infiltrating ductal carcinomas of the breast with long-term follow-up (median observation time 106 months)., Results: In the entire series, the Bcl2 variable was an independent predictor of clinical outcome, and its prognostic independence was maintained when lymph node-negative and -positive patients were considered separately. In this regard, of particular interest was the observation of a subgroup of node-negative breast cancer patients with a negative Bcl2 immunostaining, who had a very high probability of relapse or death (respectively about five and seven times greater than patients with a positive Bcl2 immunostaining). Moreover, the Bcl2 variable retained prognostic significance also in subgroups of patients treated with either adjuvant endocrine therapy or chemotherapy., Conclusions: Our results demonstrated that in breast cancer, Bcl2 protein expression parallels its mRNA level, and it has a highly significant and independent prognostic relevance.

Ginseng, refering to the roots of the species of the genus Panax ginseng, has been widely used in traditional oriental medicine for its wide spectrum of medicinal effects, such as anti-inflammatory, anti-tumorigenic, adaptogenic, and anti-aging activities. Many of its medicinal effects are attributed to the triterpene glycosides known as ginsenosides. In this study, we report a novel anti-apoptotic activity of 20(S)-ginsenoside Rg3 ((20S)Rg3) and its underlying molecular mechanism in human endothelial cells (ECs). ECs undergo apoptosis associated with increased LEHDase (caspase-9) and DEVDase (caspase-3) activity and DNA fragmentation after 24h of serum deprivation. These apoptotic markers were suppressed by the addition of (20S)Rg3. (20S)Rg3 increased the expression of Bax and conversely decreased Bcl-2. (20S)Rg3 potently induced a rapid and sustained Akt activation and Bad phosphorylation, resulting in the inhibition of mitochondrial cytochrome c release. These anti-apoptotic activities of (20S)Rg3 were significantly abrogated in cells expressing dominant negative Akt. Taken together, our results suggest that (20S)Rg3 prevents EC apoptosis via Akt-dependent inhibition of the mitochondrial apoptotic signaling pathway. The novel property of (20S)Rg3 may be valuable for developing new pharmaceutical means that will control unwanted endothelial cell death at the site of vascular injury.

The discovery of B-cell lymphoma-2 (BCL-2) over 20 years ago revealed a new paradigm in cancer biology: the development and persistence of cancer can be driven by molecular roadblocks along the natural pathway to cell death. The subsequent identification of an expansive family of BCL-2 proteins provoked an intensive investigation of the interplay among these critical regulators of cell death. What emerged was a compelling tale of guardians and executioners, each participating in a molecular choreography that dictates cell fate. Ten years into the BCL-2 era, structural details defined how certain BCL-2 family proteins interact, and molecular targeting of the BCL-2 family has since become a pharmacological quest. Although many facets of BCL-2 family death signaling remain a mechanistic mystery, small molecules and peptides that effectively target BCL-2 are eliminating the roadblock to cell death, raising hopes for a medical breakthrough in cancer and other diseases of deregulated apoptosis.

Individual BCL2 family members couple apoptosis regulation and cell cycle control in unique ways. Antiapoptotic BCL2 and BCL-x(L) are antiproliferative by facilitating G0. BAX is proapoptotic and accelerates S-phase progression. The dual functions in apoptosis and cell cycle are coordinately regulated by the multi-domain BCL2 family members (MCL-1) and suggest that survival is maintained at the expense of proliferation. The role of BH3-only molecules in cell cycle is more variable. BAD antagonizes both the cell cycle and antiapoptotic functions of BCL2 and BCL-x(L) through BH3 binding. BID has biochemically separable functions in apoptosis and S-phase checkpoint, determined by post-translational modification. p53-induced PUMA is known only to have apoptotic function. Inhibition of apoptosis is oncogenic, whereas promotion of cell cycle arrest is tumor suppressive. Paradoxically, selected BCL2 family members can be both oncogenic and tumor suppressive. Which of the dual functions predominates is lineage specific and context dependent.

Induction of apoptosis in tumour cells, either by direct activation of the death receptor pathway using agonistic antibodies or recombinant ligands, or direct triggering of the Bcl-2-regulated intrinsic apoptosis pathway by small molecule drugs, carries high hopes to overcome the shortcomings of current anticancer therapies. The latter therapy concept builds on a more detailed understanding of how Bcl-2-like molecules maintain mitochondrial integrity and how BH3-only proteins and Bax/Bak-like molecules can undermine it. Means to unleash the apoptotic potential of BH3-only proteins in tumour cells, or bypass the need for BH3-only proteins by blocking possible interactions of Bcl-2-like prosurvival molecules with Bax and/or Bak allowing their direct activation, constitute interesting options for the design of novel anticancer therapies.

Apoptosis is a phenomenon fundamental to higher eukaryotes and essential to mechanisms controlling tissue homeostasis. Bcl-2 family proteins tightly control this cell death program by regulating the permeabilization of the mitochondrial outer membrane and, hence, the release of cytochrome c and other proapoptotic factors. Mitochondrial apoptosis-induced channel (MAC) is the mitochondrial apoptosis-induced channel and is responsible for cytochrome c release early in apoptosis. MAC activity is detected by patch clamping mitochondria at the time of cytochrome c release. The Bcl-2 family proteins regulate apoptosis by controlling the formation of MAC. Depending on cell type and apoptotic inducer, Bax and/or Bak are structural component(s) of MAC. Overexpression of the antiapoptotic protein Bcl-2 eliminates MAC activity. The focus of this review is a biophysical characterization of MAC activity and its regulation by Bcl-2 family proteins, and ends with some discussion of therapeutic targets.

Recent data have revealed an unexpected role of Bcl-2 in modulating the steady-state levels and agonist-dependent fluxes of Ca(2+) ions. Direct monitoring of endoplasmic reticulum (ER) Ca(2+) concentration with recombinant probes reveals a lower state of filling in Bcl-2-overexpressing cells and a higher leak rate from the organelle. The broader set of indirect data using cytosolic probes reveals a more complex scenario, as in many cases no difference was detected in the Ca(2+) content of the intracellular pools. At the same time, Ca(2+) signals have been shown to affect important checkpoints of the apoptotic process, such as mitochondria, thus tuning the sensitivity of cells to various challenges. In this contribution, we will review (i) the data on the effect of Bcl-2 on [Ca(2+)](er), (ii) the functional significance of the Ca(2+)-signalling alteration and (iii) the current insight into the possible mechanisms of this effect.

Bcl-2-family proteins are central regulators of cell life and death. At least three major classes of Bcl-2-family proteins have been delineated, including proapoptotic proteins that contain several conserved regions of sequence similarity (termed 'multidomain'). In mammals, the multidomain proteins (MDPs) of the Bcl-2 family include Bax, Bak, and Bok. The founding member of the MDP group of Bcl-2-family proteins was discovered by Stanley Korsmeyer and co-workers, initiating an exciting area of cell death research. The status of current knowledge about the mechanisms and functions of MDPs is reviewed here, and some areas for future research are outlined. Therapeutic opportunities emerging from a growing understanding of MDPs with respect to their three-dimensional structures, biochemical actions, and roles in disease raise hopes that the foundation of basic research laid by Korsmeyer and others will eventually be translated into clinical benefits, leaving a legacy that benefits the world for many decades.

WT1 is a zinc finger transcriptional regulatory protein that has been implicated in both normal development and in the generation of a variety of malignancies. Alternative splicing of the WT1 mRNA results in the expression of four major protein isoforms. There is increasing evidence that one of the functions of WT1 is the regulation of apoptosis, but there are conflicting reports about whether WT1 is pro- or anti-apoptotic. Careful review of the literature suggests that these apparent contradictions probably reflect cell lineage and isoform-specific differences in WT1 function. Expression of WT1 prevents programmed cell death in some cell types but promotes it in others, and different WT1 isoforms exert distinct effects as well. Investigation into the mechanisms by which WT1 regulates apoptosis has revealed that several bcl-2 family members are either direct or indirect WT1 target genes, including bcl-2 itself, the pro-apoptotic family members Bak and Bax, and the anti-apoptotic family member Bfl-1/A1. The specific bcl-2 family members regulated by WT1 expression vary by cell type and by isoform. Thus, a complete understanding of the role of WT1 in apoptosis will have to account for lineage- and isoform-specific effects of WT1 at both the cellular and molecular levels.

Programmed cell death or apoptosis is central to many physiological processes and pathological conditions such as organogenesis, tissue homeostasis, cancer, and neurodegenerative diseases. Bcl-2 family proteins tightly control this cell death program by regulating the permeabilization of the mitochondrial outer membrane and, hence, the release of cytochrome c and other pro-apoptotic factors. Control of the formation of the mitochondrial apoptosis-induced channel, or MAC, is central to the regulation of apoptosis by Bcl-2 family proteins. MAC is detected early in apoptosis by patch clamping the mitochondrial outer membrane. The focus of this review is on the regulation of MAC activity by Bcl-2 family proteins. The role of MAC as the putative cytochrome c release channel during early apoptosis and insights concerning its molecular composition are also discussed.

Irreversible perturbations in the homeostasis of the endoplasmic reticulum (ER) are thought to lead to apoptosis and cell loss in a number of important human diseases, including Alzheimer disease, Parkinson disease, and type 2 diabetes. However, the exact mechanisms that lead from ER stress to cell death remain incompletely understood. Recent work has shown that the BCL-2 family of proteins plays a central role in regulating this form of cell death, both locally at the ER and from a distance at the mitochondrial membrane.

Poly(ADP-ribose) polymerase plays an important role in cell survival and death. Our previous histological and ultrastructural studies showed that PARP inhibitor 3-aminobenzamide (3-AB) protected neurons against death after ischemia. In this study we investigated the effect of 3-AB on the localization and expression of apoptosis inducing factor (AIF) and on two proteins from Bcl-2 family: Bcl-2 and Bax in hippocampal area CA1, on the 4th day after 3 min of forebrain ischemia in gerbils. Our results indicated that after ischemia AIF is preferentially translocated from the mitochondria to the cytoplasm and to the nucleus. Intravenous administration of 3-AB (30 mg/kg b.w.) prevents AIF translocation to the nucleus. AIF was mainly seen in the structurally unchanged mitochondria and Golgi complex. Moreover, after 3-AB administration overexpression of Bcl-2 protein was observed in mitochondrial membranes, rough endoplasmatic reticulum, Golgi complex, nuclear envelopes, and also in cytoplasm and in nucleus. These data suggest that inhibition of PARP activity may have a beneficial effect on hippocampal neurons through overexpression of Bcl-2 protein and suppression of AIF translocation to the nucleus.

Proteins in the Bcl-2 family are central regulators of programmed cell death, and members that inhibit apoptosis, such as Bcl-X(L) and Bcl-2, are overexpressed in many cancers and contribute to tumour initiation, progression and resistance to therapy. Bcl-X(L) expression correlates with chemo-resistance of tumour cell lines, and reductions in Bcl-2 increase sensitivity to anticancer drugs and enhance in vivo survival. The development of inhibitors of these proteins as potential anti-cancer therapeutics has been previously explored, but obtaining potent small-molecule inhibitors has proved difficult owing to the necessity of targeting a protein-protein interaction. Here, using nuclear magnetic resonance (NMR)-based screening, parallel synthesis and structure-based design, we have discovered ABT-737, a small-molecule inhibitor of the anti-apoptotic proteins Bcl-2, Bcl-X(L) and Bcl-w, with an affinity two to three orders of magnitude more potent than previously reported compounds. Mechanistic studies reveal that ABT-737 does not directly initiate the apoptotic process, but enhances the effects of death signals, displaying synergistic cytotoxicity with chemotherapeutics and radiation. ABT-737 exhibits single-agent-mechanism-based killing of cells from lymphoma and small-cell lung carcinoma lines, as well as primary patient-derived cells, and in animal models, ABT-737 improves survival, causes regression of established tumours, and produces cures in a high percentage of the mice.

Recent epidemiological studies have shown that dioxin, a persistent organic pollutant, is related to cognitive and behavioral abnormalities in the offspring of exposed cohort. In order to investigate the possible impact of dioxin in survival gene expression during brain development, we established an animal model of gestational and lactational dioxin-exposed rat offspring. The expressions of dioxin-responsive gene cytochrome P450 1A1 (CYP1A1), apoptotic gene Bax, and anti-apoptotic genes Bcl-2 and Bcl-xL were examined in rat liver and brains using Western blot analysis and RT-PCR. The results showed that treatment of pregnant rats with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) (2 microg/kg body weight through oral delivery) at gestation day 15 resulted in an increase of Bcl-xL in offspring male liver and cerebral cortex, but a decrease in female offspring. In contrast, the expression of Bcl-xL in the cerebellum was decreased in male, but increased in female. Bcl-2, another anti-apoptotic gene, was also downregulated in P0 female liver, cerebral cortex, but was not observed in male. In the 4-month-old offspring, however, the Bcl-2 protein levels in the liver and cerebellum of both male and female pups were higher in the TCDD group as compared with the control group. However, the Bcl-2 level in the cerebral cortex of TCDD-treated groups was higher than the control group only in female but not male offspring at 4 months old. The expression of Bax showed no significant changes upon TCDD exposure at P0 stage, but was significantly reduced in the 4-month-old male cortex. These results indicate that early exposure of dioxin could affect the development of certain brain regions with gender difference, in terms of its differential effect on expressions of Bcl-xL, Bcl-2, and Bax.

Mitochondria are the powerhouse of the cell. Their primary physiological function is to generate ATP through oxidative phosphorylation via the electron transport chain. Reactive oxygen radicals generated from mitochondria have been implicated in acute brain injuries, like stroke and neurodegeneration. Recent studies have shown that mitochondrially formed oxidants are mediators of molecular signaling and have implicated mitochondria-dependent apoptosis involving pro- and antiapoptotic protein binding, the release of cytochrome c and Smac, the activation of downstream caspase-9 and -3, and the fragmentation of DNA. Oxidative stress and the redox state are also implicated in the survival signaling pathway that involves phosphatidylinositol 3-kinase (PI3-K)/Akt and downstream signaling molecular bindings like Bad/Bcl-X(L) and phosphorylated Bad/14-3-3. Genetically modified mice (SOD1, SOD2) or rats that overexpress or are deficient in superoxide dismutase have provided strong evidence in support of the role of mitochondrial dysfunction and oxidative stress as determinants of neuronal death/survival after stroke and neurodegeneration.

The Bcl-2 family of proteins contains both anti and pro-apoptotic members that have been shown to regulate neuronal cell death during development and in many models of acute and chronic neurodegeneration. This family of proteins can be divided into three distinct classes based on structure and function: the anti-apoptotic sub-group; the pro-apoptotic, multi-domain sub-group; and the pro-apoptotic, BH3 domain-only sub-group. Alterations in the expression of Bcl-2 family members occur in several animal and human neurodegenerative diseases including Alzheimer's, Huntington's and Parkinson's diseases and Amyotrophic Lateral Sclerosis. Similar changes are seen in in vivo and in vitro models of acute neurodegeneration, including stroke and traumatic brain injury. Methods to increase the overall expression and/or function of anti-apoptotic Bcl-2 family members, and thus promote neuron survival, have been studied extensively in these models. Most treatment efforts focus on either the targeted delivery via viral vectors of anti-apoptotic members of Bcl-2 family members into the affected brain regions of interest, the generation of direct interactions of small molecule inhibitors with Bcl-2 family members, or the induced expression of Bcl-2 family members secondary to pharmacological manipulation. Although many challenges exist in the design of safe and efficacious Bcl-2 family mimetics for the treatment of neurodegeneration, such strategies offer great promise for preserving neuron viability, and hopefully function, in a variety of human neurological diseases.

One of the most compelling issues to impact on contemporary cardiology is arguably the phenomenon of programmed cell death or apoptosis. Studies in the nematode Caenorhabditis elegans provided the first indication that determinants of cell fate crucial for normal worm development were under genetic influences of the ced-3 and ced-9 genes, which promote or prevent cell death, respectively. Extrapolation of these seminal findings led to the discovery of the mammalian ced-3 and ced-9 homologs, which broadly encompass a family of cellular cysteine proteases known collectively as caspases and the Bcl-2 proteins. In quiescent cells, caspases exist as inactive zymogens that are readily activated by autocatalytic processes or by other caspases following a death signal. The caspase-dependent cleavage of intracellular substrates results in the biochemical dismantling of the cell and morphological features characteristic of apoptosis. Recently, a mitochondrial death pathway for apoptosis has been proposed. Perturbations to mitochondria resulting in the loss of mitochondrial membrane potential, DeltaPsim, permeability transition pore (PTP) opening and the release of pro-apoptotic factors by mitochondria including cytochrome c, second mitochondrial activator of caspases/direct IAP binding protein with low pI (Smac/DIABLO), AIF, and others are considered terminal events in the apoptotic pathway. Bcl-2 and related family members are characterized by their ability to promote or prevent cell death. These proteins exert their pro- or anti-apoptosis function by impinging on components of the cell death pathway that underlie caspase activation, mitochondrial dysfunction or both. The limited regenerative potential of the adult cardiac muscle itself, together with the heightened and exciting possibility of regenerating cardiac muscle with cardiac progenitor cells, acknowledges the need for new strategies to suppress and/or prevent inappropriate cardiac cell death in patients with ischemic heart disease or heart failure patients as a therapeutic means of preserving cardiac pump function after injury.

Histone deacetylase inhibitors modulate the transcription of target genes and represent a new class of anticancer agents. The histone deacetylase inhibitor FR901228 has been reported to show antiproliferative and apoptotic effects in various malignancies including small cell lung cancer (SCLC) in vitro; however, the underlying mechanism is not fully understood. BCL-2 and BCL-XL are antiapoptotic proteins, of which overexpression has been reported to confer resistance to anticancer agents. High levels of BCL-2 and BCL-XL are frequently expressed in SCLC tumors. The present study was designed to clarify the apoptotic pathway of FR901228 in SCLC cells in vitro. FR901228 induced apoptosis in three SCLC cell lines after 24 hours of treatment. FR901228 activated caspase-9 and caspase-3 but not caspase-8, and the caspase-3 inhibitor Z-DEVD-fmk blocked the cytotoxicity of FR901228. FR901228 down-regulated the expression of bcl-2 and bcl-xL mRNA through de novo protein synthesis and suppressed the expression of BCL-2 and BCL-XL proteins. In addition, the combination of bcl-2 antisense oligonucleotides with FR901228 enhanced FR901228-induced caspase-3 activity and cytotoxicity. These findings suggest that FR901228 induces caspase-dependent apoptosis via the mitochondrial pathway rather than the death receptor pathway. Considering the possible contributions of BCL-2 and BCL-XL to multidrug resistance, FR901228 is a promising agent in the treatment of refractory as well as primary SCLC tumors.

This study provides new insights into neuroprotection involving interaction of protein kinase C (PKC) pathway with Bcl-2 family proteins. Using a model of serum deprivation, we investigated the mechanism by which the anti-Parkinson/monoamine oxidase (MAO)-B inhibitor drug, rasagiline, exerts its neuroprotective effect in rat pheochromocytoma PC12 cells. Here, we report that rasagiline (0.1-10 microM) decreased apoptosis via multiple protection mechanisms, including the stimulation of PKC phosphorylation; up-regulation of PKCalpha and PKC mRNAs, induction of Bcl-xL, Bcl-w, and brain-derived neurotrophic factor (BDNF) mRNAs; and down-regulation of Bad and Bax mRNAs. Moreover, rasagiline inhibited the cleavage and activation of procaspase-3 and poly (ADP-ribose) polymerase (PARP), whereas the PKC inhibitor, GF109203X, reversed these actions. Similarly, rasagiline decreased serum-free-induced levels of the important regulator of cell death, Bad, which was also blocked by GF109203X, indicating the involvement of PKC in rasagiline-induced cell survival. Furthermore, these studies have established that PKC- and Bcl-2-dependent neuroprotective activity of rasagiline is dependent on its propargyl moiety, because propargylamine had similar effects with the same potency.

Members of the Bcl-2 family are crucial integrators of survival and death signals in higher eukaryotes. Although recent studies have provided novel and quite unexpected insights into the mechanisms by which these proteins might issue life permits or death sentences in cells, we are still on the way to fully understand their modes of action. This review provides a snapshot on where we are on this journey and how we may exploit our knowledge on this family of proteins to unveil the mysteries of immune regulation.

Caspase recruitment and oligomerization mediated by adaptor proteins constitute a basic mechanism of caspase activation. The complex phenotypes of the caspase knockout mice indicate that multiple mechanisms of caspase activation operate in parallel and that death signal transduction pathways are both cell-type and stimulus specific. The BH3-domain- containing pro-apototic members of Bcl-2 family may be one of the critical links between the initial death signals and the central machinery of apoptosis.