The role of the bcl-2/ced-9 gene family in cancer and general implications of defects in cell death control for tumourigenesis and resistance to chemotherapy

Over Fifty Years of Life, Death, and Cannibalism: A Historical Recollection of Apoptosis and Autophagy

Research in biomedical sciences has changed dramatically over the past fifty years. There is no doubt that the discovery of apoptosis and autophagy as two highly synchronized and regulated mechanisms in cellular homeostasis are among the most important discoveries in these decades. Along with the advancement in molecular biology, identifying the genetic players in apoptosis and autophagy has shed light on our understanding of their function in physiological and pathological conditions. In this review, we first describe the history of key discoveries in apoptosis with a molecular insight and continue with apoptosis pathways and their regulation. We touch upon the role of apoptosis in human health and its malfunction in several diseases. We discuss the path to the morphological and molecular discovery of autophagy. Moreover, we dive deep into the precise regulation of autophagy and recent findings from basic research to clinical applications of autophagy modulation in human health and illnesses and the available therapies for many diseases caused by impaired autophagy. We conclude with the exciting crosstalk between apoptosis and autophagy, from the early discoveries to recent findings.

B Cell Lymphoma 2: A Potential Therapeutic Target for Cancer Therapy

Defects in the apoptosis mechanism stimulate cancer cell growth and survival. B cell lymphoma 2 (Bcl-2) is an anti-apoptotic molecule that plays a central role in apoptosis. Bcl-2 is the founding constituent of the Bcl-2 protein family of apoptosis controllers, the primary apoptosis regulators linked with cancer. Bcl-2 has been identified as being over-expressed in several cancers. Bcl-2 is induced by protein kinases and several signaling molecules which stimulate cancer development. Identifying the important function played by Bcl-2 in cancer progression and development, and treatment made it a target related to therapy for multiple cancers. Among the various strategies that have been proposed to block Bcl-2, BH3-mimetics have appeared as a novel group of compounds thanks to their favorable effects on many cancers within several clinical settings. Because of the fundamental function of Bcl-2 in the regulation of apoptosis, the Bcl-2 protein is a potent target for the development of novel anti-tumor treatments. Bcl-2 inhibitors have been used against several cancers and provide a pre-clinical platform for testing novel therapeutic drugs. Clinical trials of multiple investigational agents targeting Bcl-2 are ongoing. This review discusses the role of Bcl-2 in cancer development; it could be exploited as a potential target for developing novel therapeutic strategies to combat various types of cancers. We further highlight the therapeutic activity of Bcl-2 inhibitors and their implications for the therapeutic management of cancer.

A small-molecule ARTS mimetic promotes apoptosis through degradation of both XIAP and Bcl-2

Many human cancers over-express B cell lymphoma 2 (Bcl-2) or X-linked inhibitor of apoptosis (IAP) proteins to evade cell death. The pro-apoptotic ARTS (Sept4_i2) protein binds directly to both Bcl-2 and XIAP and promotes apoptosis by stimulating their degradation via the ubiquitin-proteasome system (UPS). Here we describe a small molecule, A4, that mimics the function of ARTS. Microscale thermophoresis assays showed that A4 binds XIAP, but not cellular inhibitor of apoptosis protein 1 (cIAP1). A4 binds to a distinct ARTS binding pocket in the XIAP-BIR3 (baculoviral IAP repeat 3) domain. Like ARTS, A4 stimulated poly-ubiquitylation and UPS-mediated degradation of XIAP and Bcl-2, but not cIAP1, resulting in caspase-9 and -3 activation and apoptosis. In addition, over-expression of XIAP rescued HeLa cells from A4-induced apoptosis, consistent with the idea that A4 kills by antagonizing XIAP. On the other hand, treatment with the SMAC-mimetic Birinapant induced secretion of tumour necrosis factor-α (TNFα) and killed ~50% of SKOV-3 cells, and addition of A4 to Birinapant-treated cells significantly reduced secretion of TNFα and blocked Birinapant-induced apoptosis. This suggests that A4 acts by specifically targeting XIAP. The effect of A4 was selective as peripheral blood mononuclear cells and normal human breast epithelial cells were unaffected. Furthermore, proteome analysis revealed that cancer cell lines with high levels of XIAP were particularly sensitive to the killing effect of A4. These results provide proof of concept that the ARTS binding site in XIAP is "druggable". A4 represents a novel class of dual-targeting compounds stimulating apoptosis by UPS-mediated degradation of important anti-apoptotic oncogenes.

MiR-147 inhibits cyclic mechanical stretch-induced apoptosis in L6 myoblasts via ameliorating endoplasmic reticulum stress by targeting BRMS1

Functional orthopedic treatment is effective for the correction of malformation. Studies demonstrated myoblasts undergo proliferation and apoptosis on certain stretch conditions. MicroRNAs (miRNAs) function in RNA silencing and post-transcriptional regulation of gene expression, and participate in various biological processes, including proliferation and apoptosis. One hypothesis suggested that miRNA was involved into the procedure via suppressing its target genes then triggered endoplasmic reticulum stress-induced apoptosis. Therefore, miRNAs play important roles in the regulation of the proliferation and apoptosis of myoblasts. In our study, the miR-147 has been explored. A cyclic mechanical stretch model was established to observe the features of rat L6 myoblasts. The detection of mRNA and protein levels was performed by qRT-PCR and western blot. L6 cell proliferation/apoptosis was checked by CCK-8 assay, DNA fragmentation assay, and caspase-3 activity assay. MiRNA transfections were performed as per the manufacturer's suggestions: (1) cyclic mechanical stretch induced apoptosis of L6 myoblasts and inhibition of miR-147; (2) miR-147 attenuated cyclic mechanical stretch-induced apoptosis of L6 myoblasts; (3) miR-147 attenuated cyclic mechanical stretch-induced L6 myoblast endoplasmic reticulum stress; (4) BRMS1 was a direct target of miR-147 in L6 myoblasts; (5) miR-147/BRMS1 axis participated in the regulation of cyclic mechanical stress on L6 myoblasts. MiR-147 attenuates endoplasmic reticulum stress by targeting BRMS1 to inhibit cyclic mechanical stretch-induced apoptosis of L6 myoblasts.

Antitumor effects of Xi Huang pills on MDA‑MB‑231 cells in vitro and in vivo

The management of patients with triple-negative breast cancer is challenging due to the lack of effective therapeutic options, aggressive behavior and relatively poor prognosis. Xi Huang pills (XHP) are a well-known traditional Chinese medicine that demonstrate anticancer activities. The aim of the present study was to investigate the antitumor effects of XHP on MDA-MB-231 cells in vitro and in vivo, and its potential underlying molecular mechanisms. In the present study, an MTT assay was used to evaluate the antiproliferative activity of XHP on MDA-MB-231 cells. In order to investigate the effects further, cell cycle distribution, apoptosis and mitochondrial membrane potential assays were performed, as well as western blot analyses. In addition, a tumor xenograft model was employed to investigate the effects of XHP in vivo. The results of the MTT assay demonstrated that the viability of MDA-MB-231 cells was markedly inhibited by XHP in a dose- and time-dependent manner. The inhibitory effect of XHP on the viability of MDA-MB-231 cells was greater when compared with MCF-10A cells. An increase in apoptosis and loss of mitochondrial membrane potential was observed following 4, 8 and 12 mg/ml XHP treatment of MDA-MB-231 cells. The protein expression levels of cleaved caspase-3 were increased by 1.62-, 2.13- and 2.19-fold, respectively, when compared with the untreated controls, whereas no effects on the expression of B-cell lymphoma 2 (Bcl-2) or Bcl-2-associated X protein (Bax) were observed. The results of the cell cycle distribution assay analysis demonstrated that XHP treatment arrested cells at the G₂/M phase. In addition, XHP treatment decreased the expression of cyclin A and increased the expression of p21^Cip1. In vivo experiments revealed that XHP inhibited the growth of MDA-MB-231 xenograft tumors without body weight loss, and demonstrated similar effects on the protein expression levels of cleaved caspase 3, cyclin A and p21^Cip1 as observed in vitro. In conclusion, the viability of MDA-MB-231 cells was inhibited by XHP in a dose-dependent, time-dependent and cell-selective manner in vitro, and the potential underlying mechanisms may involve apoptosis and cell cycle arrest at the G₂/M phase. XHP may induce apoptosis in MDA-MB-231 cells via the intrinsic pathway, which does not involve the Bcl-2/Bax ratio. G₂/M phase arrest may have been due to the integrated action of decreased cyclin A expression and increased p21^Cip1 expression. In addition, XHP inhibited the growth of xenograft tumors in the absence of body weight loss in vivo.

A High Ki67/BCL2 Index Could Predict Lower Disease-Free and Overall Survival in Intestinal-Type Gastric Cancer

BACKGROUND

The heterogeneity of gastric cancer makes the identification of potential prognostic indicators particularly important. The Ki67 and BCL2 proteins are known prognostic markers for different types of cancer. Ki67 is associated with cell proliferation, whereas BCL2 has antiproliferative roles. A combined marker based on these opposite functions might provide improved prognostic information in gastric cancer.

METHOD

Ki67 and BCL2 expression was assessed in 276 gastric adenocarcinoma tissue microarrays. A Ki67/BCL2 index based on the relative expression of each protein was divided into low- and high-risk groups using receiver operating characteristic curves.

RESULTS

A high Ki67/BCL2 index significantly correlated with advanced stage, recurrence, intestinal type, high histologic grade, and lymphatic and perineural invasion (all p < 0.05). Univariate and multivariate analyses revealed a significant relationship between disease-free or overall survival and the Ki67/BCL2 index in intestinal-type gastric cancer (all p < 0.05).

CONCLUSIONS

A combined marker using Ki67 and BCL2 could be a useful indicator for predicting survival in patients with intestinal-type gastric cancer.

Multiple effects of Xihuang pill aqueous extract on the Hs578T triple-negative breast cancer cell line

The management of triple-negative breast cancer (TNBC) is challenging due to the aggressive behavior, lack of therapeutic options and relatively poor prognosis. Xihuang pill (XHP) is a well-known Traditional Chinese Medicine with anticancer activity. The aim of the present study was to investigate whether the aqueous extract of XHP (AEXHP) has anti-proliferative activity against the Hs578T TNBC cell line, and to elucidate its molecular mechanisms of action. First, an MTT assay was used to evaluate the anti-proliferative activity of AEXHP on the Hs578T cell line; furthermore, the cell cycle distribution, mitochondrial membrane potential and apoptotic rate were determined by flow cytometry, and western blot analysis was used to assess the expression of apoptosis and cell cycle regulatory proteins to investigate the mechanisms of action. The results revealed that the cell viability was significantly inhibited by AEXHP in a dose- and time-dependent manner. Apoptosis and mitochondrial membrane potential loss were detected, and after treatment with 4, 8 and 12 mg/ml AEXHP for 24 h, cleaved caspase-3 was 1.70-, 1.81- and 1.84-fold of that of the control, while procaspase-3, procaspase-8, cleaved caspase-8, B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax) and the Bcl-2/Bax ratio were not significantly affected. Cell cycle analysis revealed that treatment with AEXHP led to S-phase arrest of Hs578T cells. Furthermore, AEXHP treatment resulted in decreased expression of cyclin A and cyclin dependent kinase 2 (CDK2), and increased expression of cyclin E and p21^Cip1, as compared to the control group. In conclusion, the viability of Hs578T cells was significantly inhibited by AEXHP in a dose- and time-dependent manner, the likely mechanisms of which being induction of apoptosis, probably via the intrinsic, Bcl-2-independent pathway, and cell cycle arrest in S phase due to decreased expression of cyclin A and CDK2, and increased expression of cyclin E and p21^Cip1.

Diverse mechanisms evolved by DNA viruses to inhibit early host defenses

In mammalian cells, early defenses against infection by pathogens are mounted through a complex network of signaling pathways shepherded by immune-modulatory pattern-recognition receptors. As obligate parasites, the survival of viruses is dependent on the evolutionary acquisition of mechanisms that tactfully dismantle and subvert the cellular intrinsic and innate immune responses. Here, we review the diverse mechanisms by which viruses that accommodate DNA genomes are able to circumvent activation of cellular immunity. We start by discussing viral manipulation of host defense protein levels by either transcriptional regulation or protein degradation. We next review viral strategies used to repurpose or inhibit these cellular immune factors by molecular hijacking or by regulating their post-translational modification status. Additionally, we explore the infection-induced temporal modulation of apoptosis to facilitate viral replication and spread. Lastly, the co-evolution of viruses with their hosts is highlighted by the acquisition of elegant mechanisms for suppressing host defenses via viral mimicry of host factors. In closing, we present a perspective on how characterizing these viral evasion tactics both broadens the understanding of virus-host interactions and reveals essential functions of the immune system at the molecular level. This knowledge is critical in understanding the sources of viral pathogenesis, as well as for the design of antiviral therapeutics and autoimmunity treatments.

SP6616 as a new Kv2.1 channel inhibitor efficiently promotes β-cell survival involving both PKC/Erk1/2 and CaM/PI3K/Akt signaling pathways

Kv2.1 as a voltage-gated potassium (Kv) channel subunit has a pivotal role in the regulation of glucose-stimulated insulin secretion (GSIS) and pancreatic β-cell apoptosis, and is believed to be a promising target for anti-diabetic drug discovery, although the mechanism underlying the Kv2.1-mediated β-cell apoptosis is obscure. Here, the small molecular compound, ethyl 5-(3-ethoxy-4-methoxyphenyl)-2-(4-hydroxy-3-methoxybenzylidene)-7-methyl-3-oxo-2,3-dihydro-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate (SP6616) was discovered to be a new Kv2.1 inhibitor. It was effective in both promoting GSIS and protecting β cells from apoptosis. Evaluation of SP6616 on either high-fat diet combined with streptozocin-induced type 2 diabetic mice or db/db mice further verified its efficacy in the amelioration of β-cell dysfunction and glucose homeostasis. SP6616 treatment efficiently increased serum insulin level, restored β-cell mass, decreased fasting blood glucose and glycated hemoglobin levels, and improved oral glucose tolerance. Mechanism study indicated that the promotion of SP6616 on β-cell survival was tightly linked to its regulation against both protein kinases C (PKC)/extracellular-regulated protein kinases 1/2 (Erk1/2) and calmodulin(CaM)/phosphatidylinositol 3-kinase(PI3K)/serine/threonine-specific protein kinase (Akt) signaling pathways. To our knowledge, this may be the first report on the underlying pathway responsible for the Kv2.1-mediated β-cell protection. In addition, our study has also highlighted the potential of SP6616 in the treatment of type 2 diabetes.

IL17 Promotes Mammary Tumor Progression by Changing the Behavior of Tumor Cells and Eliciting Tumorigenic Neutrophils Recruitment

The aggressiveness of invasive ductal carcinoma (IDC) of the breast is associated with increased IL17 levels. Studying the role of IL17 in invasive breast tumor pathogenesis, we found that metastatic primary tumor-infiltrating T lymphocytes produced elevated levels of IL17, whereas IL17 neutralization inhibited tumor growth and prevented the migration of neutrophils and tumor cells to secondary disease sites. Tumorigenic neutrophils promote disease progression, producing CXCL1, MMP9, VEGF, and TNFα, and their depletion suppressed tumor growth. IL17A also induced IL6 and CCL20 production in metastatic tumor cells, favoring the recruitment and differentiation of Th17. In addition, IL17A changed the gene-expression profile and the behavior of nonmetastatic tumor cells, causing tumor growth in vivo, confirming the protumor role of IL17. Furthermore, high IL17 expression was associated with lower disease-free survival and worse prognosis in IDC patients. Thus, IL17 blockade represents an attractive approach for the control of invasive breast tumors.

Anti-proliferative of physcion 8-O-β-glucopyranoside isolated from Rumex japonicus Houtt. on A549 cell lines via inducing apoptosis and cell cycle arrest

Background

Lung cancers are leading causes of cancer death, and Rumex japonicus has been traditionally used in folk medicine as anti-microorganic, anti-inflammatory and anti-tumor agents. This study was designed to investigate the anti-proliferative activity of physcion 8-O-β-glucopyranoside (PG) isolated from Rumex japonicus Houtt. on A549 cell lines.

Methods

In our present study, PG was isolated and identified from the ethanol extracts of R. japonicus. MTT method was used to evaluate the anti-proliferative activity of PG on A549 cell lines, and cell cycle distribution assay, apoptosis assay, and western blot analysis in vitro were used to explore the possible mechanisms.

Results

From the results of our present study, cell viability was obviously inhibited by PG, in a dose- and time-dependent manner. Our results also suggested that the anti-proliferative effect of PG was related to cell cycle arrest at the G2/M phase through repression of cdc2 and Cyclin B1 protein expression. In addition, the results of apoptosis assay and western blot analysis indicated that the anti-proliferative activity could be related to apoptosis via up-regulating the expressions of Bax, caspase-3 and caspase-7, and down-regulating the expressions of Bcl-2.

Conclusions

In conclusion, the PG has significant anti-proliferative activity on A549 cell lines, and the possible mechanism was related to cell cycle arrest at the G2/M phase, and apoptosis via the regulations of Bax, Bcl-2, and caspase-3 and caspase-7.

Anti-tumor effects of atractylenolide I isolated from Atractylodes macrocephala in human lung carcinoma cell lines

Atractylenolide I (ATL-1) is the major sesquiterpenoid of Atractylodes macrocephala. This study was designed to investigate whether ATL-1 induced apoptosis in A549 and HCC827 cells in vitro and in vivo. In our results, ATL-1 significantly decreased the percentage of in vitro viability, in a dose-dependent manner. In addition, DAPI staining and flow cytometry tests demonstrated the induction of apoptosis by ATL-I. Western blot analysis indicated that the protein levels of caspase-3, caspase-9 and Bax were increased in A549 and HCC827 cells after ATL-I exposure; to the contrary, the expressions of Bcl-2, Bcl-XL were decreased after treatment with ATL-1. In the in vivo study, ATL-I effectively suppressed tumor growth (A549) in transplanted tumor nude mice with up-regulation of caspase-3, caspase-9, and Bax and down-regulation of Bcl-2 and Bcl-XL. In conclusion, our results demonstrated that ATL-I has significant antitumor activity in lung carcinoma cells, and the possible mechanism of action may be related to apoptosis induced by ATL-I via a mitochondria-mediated apoptosis pathway.

Simultaneous positivity for anti-DNA, anti-nucleosome and anti-histone antibodies is a marker for more severe lupus nephritis

OBJECTIVE

The purpose of this study is to examine autoantibody profile of systemic lupus erythematosus (SLE) patients with lupus nephritis (LN) and to establish the correlation between the antibody reactivity and disease activity of LN.

METHODS

Autoantibodies and serological parameters were measured and analyzed in 589 SLE patients. The associations of the co-positivity of anti-dsDNA, -nucleosome and -histone antibodies (3-pos) with clinical, serological and outcome parameters were analyzed.

RESULTS

At the study entry, the prevalence for anti-dsDNA (61.52 % vs. 34.11 %, P < 0.0001), anti-nucleosome (56.09 % vs. 37.21 %, P = 0.0002) and anti-histone (49.35 % vs. 33.33 %, P = 0.0013) antibodies in patients with LN were significantly higher than that in patients without LN. Patients with 3-pos had a higher proportion of proliferative renal lesions (class III + IV). The incidence of a poor renal outcome (7.14 % vs. 2.52 %, P = 0.0174) in LN patients with 3-pos was significantly higher than those without 3-pos. Moreover, the rate of remission (73.63 % vs. 82.37 %, P = 0.0245) was significantly reduced and recurrence increased (58.90 % vs. 23.44 %, P < 0.0001) in 3-pos patients as compared to that in non 3-pos within the LN group.

CONCLUSION

Our data indicate a strong association between the 3-pos and renal disease activities, especially proliferative glomerulonephritis. The ability of 3-pos to predict renal flares may lead to major additional benefits in the follow-up of these patients.

Substantial susceptibility of chronic lymphocytic leukemia to BCL2 inhibition: results of a phase I study of navitoclax in patients with relapsed or refractory disease

PURPOSE

BCL2 overexpression is a hallmark of chronic lymphocytic leukemia (CLL). The novel BH3 mimetic navitoclax (ABT-263) specifically inhibits BCL2 and related proteins BCL-x(l) and BCL-w, potently inducing apoptosis of CLL cells in vitro. A phase I trial in patients with CLL was conducted to evaluate the safety, pharmacokinetics, and biologic activity of oral navitoclax.

PATIENTS AND METHODS

Twenty-nine patients with relapsed or refractory CLL received daily navitoclax for 14 days (10, 110, 200, or 250 mg/d; n = 15) or 21 days (125, 200, 250, or 300 mg/d; n = 14) of each 21-day cycle. Dose escalation decisions were informed by continual reassessment methodology.

RESULTS

Lymphocytosis was reduced by more than 50% in 19 of 21 patients with baseline lymphocytosis. Among 26 patients treated with navitoclax ≥ 110 mg/d, nine (35%) achieved a partial response and seven maintained stable disease for more than 6 months. Median treatment duration was 7 months (range, 1 to ≥ 29 months). Median progression-free survival was 25 months. Activity was observed in patients with fludarabine-refractory disease, bulky adenopathy, and del(17p) CLL. Thrombocytopenia due to BCL-x(l) inhibition was the major dose-limiting toxicity and was dose-related. Low MCL1 expression and high BIM:MCL1 or BIM:BCL2 ratios in leukemic cells correlated with response. We determined that the navitoclax dose of 250 mg/d in a continuous dosing schedule was optimal for phase II studies.

CONCLUSION

BCL2 is a valid therapeutic target in CLL, and its inhibition by navitoclax warrants further evaluation as monotherapy and in combination in this disease.

Odontoblast-targeted Bcl-2 overexpression impairs dentin formation

Apoptosis has been described extensively in tooth development, which is under tight control of multiple apoptosis regulators, including anti-apoptotic protein Bcl-2. However, it is totally unclear how Bcl-2 is related to odontogenesis, especially dentinogenesis. Using a transgenic mouse Col2.3Bcl-2 in which human Bcl-2 was overexpressed in odontoblasts, the effect of Bcl-2 on dentinogenesis was investigated. Overexpression of Bcl-2 was detected by immunohistochemistry and Western blot. Odontoblast apoptosis was evaluated by TUNEL and Western blot detection of cleaved caspase-3. Odontoblast differentiation was assessed by real-time PCR detection of dentin matrix expression. Dentin mineralization was evaluated by micro-CT in vivo, and alizarin red S staining and calcium content analysis in vitro. Bcl-2 was found to be overexpressed in odontoblasts and prevent their apoptosis. Odontoblast differentiation and mineralization was inhibited by Bcl-2, as evidenced by lower expressions of DMP-1, OC, and DSPP, and decreased odontoblast mineralization in vitro, as well as decreased dentin thickness and mineral density in vivo when compared to the wild-type animals. Inhibition of odontoblast differentiation by Bcl-2 occurs, at least partially, via a suppression of MEK-ERK1/2 signaling pathway. In conclusion, Bcl-2 overexpression prevents odontoblast apoptosis and impairs dentin formation, partially via an inhibition of odontoblast differentiation. This study revealed some novel functions of Bcl-2 in dentinogenesis in addition to its anti-apoptotic effect, which shed some light on the genetic complexity of tooth development.

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.

Development of a pharmacodynamic screening model with Entamoeba histolytica

Human amoebiasis caused by Entamoeba histolytica is widely distributed in the tropics and subtropics, but also occurring in neighbouring parts of the temperate zones. Invasive amoebiasis causes dysentery and, by haematogenous spread, also extra-intestinal hepatic, pulmonary or cerebral abscesses, not rarely fatal conditions. The available anti-amoebic drugs have shortcomings regarding tolerability and efficacy. To facilitate the screening of candidate material, an in vitro system has been developed that permits the determination of specific anti-amoebic activity. PYE medium, supplemented with bovine serum, proved to be suitable for the maintenance of the stock cultures of Entamoeba histolytica strain HM1:1MSS. For sensitivity testing, Waymouth medium and cultivation under aerobic conditions were most reliable. After adapting the system to the use of 96-well (8 x 12) tissue culture plates, sensitivity tests were carried out with metronidazole, dehydroemetine and dihydroartemisinin as active control drugs, and seven extracts from Stemona tuberosa, Aglaia edulis, Aglaia elaeagnoidea and Aglaia odorata. Stem bark extract from Aglaia elaeagnoidea was the most active material with an IC(99) of 496 ng/ml and a slope S of 1.1325, followed by leaf extract from Stemona tuberosa with an IC(99) of 638 ng/ml and a slope S of 1.5648. All seven extracts showed full activity at concentrations <4000 ng/ml and qualified for further investigation.

The orphan adapter protein SLY1 as a novel anti-apoptotic protein required for thymocyte development

Background

SH3 containing Lymphocyte Protein (SLY1) is a putative adapter protein exclusively expressed in lymphocytes which is involved in antigen receptor induced activation. We previously have generated SLY1^Δ/Δ mice harbouring a partial deletion in the N-terminal region of SLY1 which revealed profound immunological defects in T and B cell functions.

Results

In this study, T cell development in SLY1^-/- and SLY1^Δ/Δ mice was analysed ex vivo and upon cultivation with the bone marrow stromal cell line OP9. SLY1-deficient thymocytes were compromised in inducing nutrient receptor expression and ribosomal protein S6 phosphorylation, indicating a defect in mTOR complex activation. Furthermore, SLY1 was identified as a novel anti-apoptotic protein required for developmental progression of T cell precursors to the CD4⁺CD8⁺ double-positive stage by protecting from premature programmed cell death initiation in developing CD4^-CD8^- double-negative thymocytes. In addition, SLY1 phosphorylation was differentially regulated upon Notch ligand-mediated stimulation and expression of the preTCR.

Conclusion

Thus, our results suggest a non-redundant role for SLY1 in integrating signals from both receptors in early T cell progenitors in the thymus.

Bcl-2 family proteins as regulators of oxidative stress

The Bcl-2 family of proteins includes pro- and anti-apoptotic factors acting at mitochondrial and microsomal membranes. An impressive body of published studies, using genetic and physical reconstitution experiments in model organisms and cell lines, supports a view of Bcl-2 proteins as the critical arbiters of apoptotic cell death decisions in most circumstances (excepting CD95 death receptor signaling in Type I cells). Evasion of apoptosis is one of the hallmarks of cancer [Hanahan D, Weinberg RA. The hallmarks of cancer. Cell 2000;100:57-70], relevant to tumorigenesis as well as resistance to cytotoxic drugs, and deregulation of Bcl-2 proteins is observed in many cancers [Manion MK, Hockenbery DM. Targeting BCL-2-related proteins in cancer therapy. Cancer Biol Ther. 2003;2:S105-14; Olejniczak ET, Van Sant C, Anderson MG, Wang G, Tahir SK, Sauter G, et al. Integrative genomic analysis of small-cell lung carcinoma reveals correlates of sensitivity to bcl-2 antagonists and uncovers novel chromosomal gains. Mol Cancer Res. 2007;5:331-9]. The rekindled interest in aerobic glycolysis as a cancer trait raises interesting questions as to how metabolic changes in cancer cells are integrated with other essential alterations in cancer, e.g. promotion of angiogenesis and unbridled growth signals. Apoptosis induced by multiple different signals involves loss of mitochondrial homeostasis, in particular, outer mitochondrial membrane integrity, releasing cytochrome c and other proteins from the intermembrane space. This integrative process, controlled by Bcl-2 family proteins, is also influenced by the metabolic state of the cell. In this review, we consider the role of reactive oxygen species, a metabolic by-product, in the mitochondrial pathway of apoptosis, and the relationships between Bcl-2 functions and oxidative stress.

Bcl-2 family proteins as regulators of oxidative stress

The Bcl-2 family of proteins includes pro- and anti-apoptotic factors acting at mitochondrial and microsomal membranes. An impressive body of published studies, using genetic and physical reconstitution experiments in model organisms and cell lines, supports a view of Bcl-2 proteins as the critical arbiters of apoptotic cell death decisions in most circumstances (excepting CD95 death receptor signaling in Type I cells). Evasion of apoptosis is one of the hallmarks of cancer [Hanahan D, Weinberg RA. The hallmarks of cancer. Cell 2000;100:57-70], relevant to tumorigenesis as well as resistance to cytotoxic drugs, and deregulation of Bcl-2 proteins is observed in many cancers [Manion MK, Hockenbery DM. Targeting BCL-2-related proteins in cancer therapy. Cancer Biol Ther. 2003;2:S105-14; Olejniczak ET, Van Sant C, Anderson MG, Wang G, Tahir SK, Sauter G, et al. Integrative genomic analysis of small-cell lung carcinoma reveals correlates of sensitivity to bcl-2 antagonists and uncovers novel chromosomal gains. Mol Cancer Res. 2007;5:331-9]. The rekindled interest in aerobic glycolysis as a cancer trait raises interesting questions as to how metabolic changes in cancer cells are integrated with other essential alterations in cancer, e.g. promotion of angiogenesis and unbridled growth signals. Apoptosis induced by multiple different signals involves loss of mitochondrial homeostasis, in particular, outer mitochondrial membrane integrity, releasing cytochrome c and other proteins from the intermembrane space. This integrative process, controlled by Bcl-2 family proteins, is also influenced by the metabolic state of the cell. In this review, we consider the role of reactive oxygen species, a metabolic by-product, in the mitochondrial pathway of apoptosis, and the relationships between Bcl-2 functions and oxidative stress.

The clinical significance of splice variants and subcellular localisation of survivin in non-small cell lung cancers

Survivin is a member of the inhibitor of apoptosis protein family. Survivin has splice variants with different biological functions associated with tumorigenesis. We investigated 134 non-small cell lung cancers (NSCLCs) to study the clinical significance of wild-type survivin, survivin-2B, and survivin-deltaEx3. Real-time PCR analyses were performed for their gene expressions. The subcellular localisation of survivin proteins was evaluated by immunohistochemistry. The Ki-67 proliferation index and the apoptotic index were also evaluated. The survivin-deltaEx3 gene expression was significantly higher in stage II–III than in stage I (P=0.0174), and significantly correlated with the nuclear pan-survivin expression (P<0.0001). The Ki-67 index was significantly higher in wild-type survivin-positive tumours (P<0.0001), survivin-deltaEx3-positive tumours (P<0.0001), and tumours with positive expression of the nuclear pan-survivin (P=0.0047). In contrast, the apoptotic index was significantly lower only in wild-type survivin-positive tumours (P<0.0001). Thus, the wild-type survivin gene expression was associated with apoptotic inhibition and tumour proliferation. Furthermore, the survivin-deltaEx3 gene expression was strongly associated with tumour proliferation, especially in advanced stage NSCLCs. In contrast, the survivin-2B gene expression did not correlate with tumour proliferation or tumour apoptosis.

Development of a pharmacodynamic screening model with Crithidia fasciculata

The genus Crithidia is a member of the family Trypanosomatidae and is related to the genera Leishmania and Trypanosoma with which it shares a variety of biochemical mechanisms, such as polyamine synthesis and methionin salvage. In consequence, a screening system for antiparasitic candidate material has been developed with Crithidia fasciculata, a parasite naturally occurring in insects and amphibians, but devoid of pathogenicity for humans. Initially a variety of culture media were evaluated of which TPS was best suited for the maintenance of stock cultures, and E-medium - a newly developed formula - for sensitivity testing. Optimal growth of C. fasciculata was observed under microaerophilic conditions. A system for sensitivity testing was developed and applied to the investigation of extracts from higher tropical plants of the genera Stemona and Aglaia for anticrithidial activity. Extracts with significant anti-crithidial activity were scheduled for chromatographic fractionation and the subsequent isolation, purification and structural identification of individual compounds for further sensitivity testing. Encouraging results were obtained with extracts from Aglaia odorata leaves, A. elaeagnoidea stem bark and A. edulis leaves, with EC(90) values of 1213 ng/ml, 1606 ng/ml, and 1462 ng/ml, respectively.

High Smac/DIABLO expression is associated with early local recurrence of cervical cancer

Background

In a recent pilot report, we showed that Smac/DIABLO mRNA is expressed de novo in a subset of cervical cancer patients. We have now expanded this study and analyzed Smac/DIABLO expression in the primary lesions in 109 cervical cancer patients.

Methods

We used immunohistochemistry of formalin-fixed, paraffin-embedded tissue sections to analyze Smac/DIABLO expression in the 109 primary lesions. Seventy-eight samples corresponded to epidermoid cervical cancer and 31 to cervical adenocarcinoma. The median follow up was 46.86 months (range 10–186).

Results

Smac/DIABLO was expressed in more adenocarcinoma samples than squamous tumours (71% vs 50%; p = 0.037). Among the pathological variables, a positive correlation was found between Smac/DIABLO immunoreactivity and microvascular density, a marker for angiogenesis (p = 0.04). Most importantly, Smac/DIABLO immunoreactivity was associated with a higher rate of local recurrence in squamous cell carcinoma (p = 0.002, log rank test). No association was found between Smac/DIABLO and survival rates.

Conclusion

Smac/DIABLO expression is a potential marker for local recurrence in cervical squamous cell carcinoma patients.

Cigarette smoke affects apoptosis in rat tongue mucosa: role of bcl-2 gene family

While it has been clearly demonstrated that smoking is the most significant exogenous factor involved in oral carcinogenesis, little is known about the global molecular and cellular changes that occur prior to the appearance of clinically detectable symptoms. Thus, the aim of this study was to investigate the expressivity of bcl-2, bax and PCNA in the rat tongue mucosa exposed to cigarette smoke by means of immunohistochemistry. A total of twelve male Wistar rats were distributed into 2 groups: negative control and experimental group exposed to cigarette smoke during 75 days. After experimental period, no histopathological changes in the tongue mucosa were detected in the negative control and the experimental group. On the other hand, an overexpression of bcl-2 was detected (p < 0.01) throughout all layers of the epithelium, whereas bax did not show significant differences (p > 0.05). Also, the labeling index for bcl-2 and bax showed an increase 75 days after cigarette exposure (p < 0.01). PCNA-labeling index did not show remarkable changes between groups. Taken together, our results show that bcl-2 is overexpressed in the rat tongue keratinocytes after cigarette smoke exposure.

Molecular interactions of human immunodeficiency virus type 1 with primary human oral keratinocytes

Infection of the oral mucosa of human immunodeficiency virus type 1 (HIV-1)-infected individuals remains an under-evaluated and somewhat enigmatic process. Nonetheless, it is of profound importance in the ongoing AIDS pandemic, based on its potential as a site of person-to-person transmission of the virus as well as a location of HIV-1 pathogenesis and potential reservoir of disease in the setting of virally suppressive highly active antiretroviral therapy. We utilized molecular and virological techniques to analyze HIV-1 infection of primary human mucosal cells and also evaluated the proapoptotic potential of selected HIV-1 proteins in primary isolated human oral keratinocytes. Primary isolated human oral keratinocytes were plated on 0.4 microM polyethylenetetraphthalate cell culture inserts to form an in vitro oral mucosal layer. The strength of this layer in forming a barrier was determined by measuring trans-epithelial electrical current passage across the monolayer. The oral keratinocyte monolayers had trans-epithelial electrical resistance of approximately 176 to 208 omega. For viral infectivity assays, the macrophage-tropic (R5) HIV-1 strains, YU-2 and ADA, and T-cell-line-tropic (X4), NL4-3 virions, incubated with or without deoxynucleoside triphosphates (dNTPs) and/or the polyamines spermine and spermidine, were used to infect oral keratinocytes. Of importance, polyamines and dNTPs have been shown to enhance natural endogenous reverse transcription (NERT), a step essential for early lentiviral infection, and are abundantly present in human semen. The infectivities of HIV-1 strains YU-2, ADA, and NL4-3 for these primary keratinocytes were dramatically increased by the addition of physiological concentrations of dNTPs, spermine, and spermidine. Binding and viral internalization assay studies showed no differences in these oral mucosal cells, with or without NERT-altering agents. It was also observed that the recombinant, cell-free HIV-1 proteins Nef, Tat, and gp120 (R5) induced apoptosis in primary oral keratinocytes compared with the results seen with nontreated cells or cells treated with glutathione S-transferase protein as a control under similar conditions. Microarray analyses suggested that HIV-1 gp120 and Tat induce apoptosis in primary human oral keratinocytes via the Fas/FasL apoptotic pathway, whereas induction of apoptosis by Nef occurs through both Fas/FasL and mitochondrial apoptotic pathways. Thus, these findings suggest molecular mechanisms by which semen in particular, as well as other bodily fluids such as cervicovaginal secretions, could increase oral transmission of HIV-1 via increasing infectivity in confluent and low-replicating oral keratinocytes. As well, the induction of apoptosis in human oral keratinocytes with relevant HIV-1-specific proteins suggests another potential complementary mechanism by which the oral mucosa barrier may be disrupted during HIV-1 infection in vivo.

Expression of Siva-1 protein or its putative amphipathic helical region enhances cisplatin-induced apoptosis in breast cancer cells: effect of elevated levels of BCL-2

cis-Diaminedichloroplatinum (II) (cisplatin) is routinely used to treat various types of cancers; however, a significant number develop resistance. One of the underlying factors that contribute to cisplatin resistance is the elevated level of BCL-2 and/or BCL-XL, which promotes cell survival. A potential method of overcoming such resistance is to use a potentiator that is capable of neutralizing the antiapoptotic effects of BCL-2/BCL-XL, such as Siva-1. We previously cloned the proapoptotic protein Siva-1 and showed a possible role for it in both extrinsic and intrinsic apoptosis. Using an adenovirus-based expression system, we now show that Siva-1 can synergize with cisplatin in inducing apoptosis in MCF7 and MDA-MB-231 breast cancer cells. In an anchorage-independent clonogenicity assay, MCF7/caspase-3 cells stably expressing Siva-1, but not the control cells, showed a dramatic decrease in the number of colonies formed on one-time cisplatin treatment. Further, we show that the unique putative amphipathic helical region (SAH) in Siva-1 (amino acid residues 36-55) is necessary and sufficient for the observed enhancement in cisplatin-induced apoptosis by Siva-1. Although cisplatin treatment results in significant elevation in the expression of Fas ligand and intracellular p21 levels, expression of Siva-1 has no additional benefit. Instead, the enhancement in apoptosis seems to be due to activation of intrinsic pathway that involves caspase-9 activation. Moreover, Siva-1 augments cisplatin-mediated cell death in MCF7 cells stably expressing BCL-2. We therefore propose that Siva-1 or its SAH region can be used as a potentiator of cisplatin-based chemotherapy.

Ultraviolet-induced transformation of keratinocytes: possible involvement of long interspersed element-1 reverse transcriptase

The normal human keratinocyte cell line, HaCaT, was transformed using multiple doses of ultraviolet (UV)A+B (UVA, 150-200 mJ/cm(2) and UVB, 15-20 mJ/cm(2) x 6). Malignant transformation was confirmed by upregulation of Cyclin D1 (mRNA) and formation of colonies on soft agar. To identify the genes involved in this transformation process, we have done rapid amplification of polymorphic DNA using RNA from unexposed and multiple-exposed cells. Six percent PAGE showed several differentially regulated genes in exposed cells compared with unexposed cells. Total 19 genes were identified, cloned and sequenced. Three of these 19 cloned genes showed 99% homology at both DNA and protein levels to a stretch of 540 bp (180 aa) of long interspersed element (LINE)-1 reverse transcriptase (RT) open reading frame (ORF-2). Colonies from soft agar showed upregulation of this gene compared with non-colonized (lawn on soft agar) cells as detected by RT-PCR. This data implicates LINE-1 RT (ORF-2) in UV-induced malignancy and can possibly be used as a marker for the diagnosis of UV-induced skin cancer.

Mcl-1 is a novel therapeutic target for human sarcoma: synergistic inhibition of human sarcoma xenotransplants by a combination of mcl-1 antisense oligonucleotides with low-dose cyclophosphamide

PURPOSE

Little is known about the role that Mcl-1, an antiapoptotic Bcl-2 family member, plays in solid tumor biology and susceptibility to anticancer therapy. We observed that the Mcl-1 protein is widely expressed in human sarcoma cell lines of different histological origin (n = 7). Because the expression of antiapoptotic Bcl-2 family proteins can significantly contribute to the chemoresistance of human malignancies, we used an antisense strategy to address this issue in sarcoma.

EXPERIMENTAL DESIGN

SCID mice (n = 6/group) received s.c. injections of SW872 liposarcoma cells. After development of palpable tumors, mice were treated by s.c.-implanted miniosmotic pumps prefilled with saline or antisense or universal control oligonucleotides (20 mg/kg/day for 2 weeks). On days 2, 6, and 10, mice were treated with low-dose cyclophosphamide (35 mg/kg i.p) or saline control. During the experiments, tumor weight was assessed twice weekly by caliper measurements. On day 14, animals were sacrificed. Tumors were weighed and fixed in formalin for immunohistochemistry and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling analysis.

RESULTS

Mcl-1 antisense oligonucleotides specifically reduced Mcl-1 protein expression but produced no reduction in tumor weight compared with saline-treated control animals. Cyclophosphamide monotreatment caused only modest tumor weight reduction compared with saline control. However, use of Mcl-1 antisense oligonucleotides combined with cyclophosphamide clearly enhanced tumor cell apoptosis and significantly reduced tumor weight by more than two-thirds compared with respective control treatments.

CONCLUSION

A combination of Mcl-1 antisense oligonucleotides with low-dose cyclophosphamide provides a synergistic antitumor effect and might qualify as a promising strategy to overcome chemoresistance in human sarcoma.

Terephthalamide derivatives as mimetics of the helical region of Bak peptide target Bcl-xL protein

A group of novel Bcl-xL/Bak antagonists, based on a terephthalamide scaffold, were designed to mimic the alpha-helical region of the Bak peptide. Good in vitro inhibition potencies in disrupting the Bak/Bcl-xL complex have been observed (terephthalamide 4, K(i)=0.78+/-0.07 microM).

Metastasis-associated protein 1 deregulation causes inappropriate mammary gland development and tumorigenesis

Emerging data suggest that metastasis-associated protein 1 (MTA1) represses ligand-dependent transactivation functions of estrogen receptor-alpha in cultured breast cancer cells and that MTA1 is upregulated in human breast tumors. However, the role of MTA1 in tumorigenesis in a physiologically relevant animal system remains unknown. To reveal the role of MTA1 in mammary gland development, transgenic mice expressing MTA1 under the control of the mouse mammary tumor virus promoter long terminal repeat were generated. Unexpectedly, we found that mammary glands of these virgin transgenic mice exhibited extensive side branching and precocious differentiation because of increased proliferation of ductal and alveolar epithelial cells. Mammary glands of virgin transgenic mice resemble those from wild-type mice in mid-pregnancy and inappropriately express beta-casein, cyclin D1 and beta-catenin protein. Increased ductal growth was also observed in the glands of ovariectomized female mice, as well as of transgenic male mice. MTA1 dysregulation in mammary epithelium and cancer cells triggered downregulation of the progesterone receptor-B isoform and upregulation of the progesterone receptor-A isoform, resulting in an imbalance in the native ratio of progesterone receptor A and B isoforms. MTA1 transgene also increased the expression of progesterone receptor-A target genes Bcl-XL (Bcl2l1) and cyclin D1 in mammary gland of virgin mice, and, subsequently, produced a delayed involution. Remarkably, 30% of MTA1 transgenic females developed focal hyperplastic nodules, and about 7% exhibited mammary tumors within 18 months. These studies establish, for the first time, a potential role of MTA1 in mammary gland development and tumorigenesis. The underlying mechanism involves the upregulation of progesterone receptor A and its targets, Bcl-XL and cyclin D1.

AIM inhibits apoptosis of T cells and NKT cells in Corynebacterium-induced granuloma formation in mice

Apoptosis inhibitor expressed by macrophages (AIM) inhibits apoptosis of CD4(+)CD8(+) (CD4/CD8) double-positive thymocytes, and supports the viability of these cells on the thymic selection. However, pleiotropic functions of AIM have been suggested. In this study, heat-killed Corynebacterium parvum (C. parvum) was injected into mice carrying the homozygous mutation (AIM(-/-)) and wild-type (AIM(+/+)) mice, to investigate the role of AIM in the formation of hepatic granulomas. In AIM(-/-) mice, the size and the number of hepatic granulomas were larger, and the resorption of granulomas was more delayed than in AIM(+/+) mice. The production of interleukin-12 was more prominent in AIM(-/-) mice than in AIM(+/+) mice. In the liver of AIM(+/+) mice, expression of AIM messenger ribonucleic acid (mRNA) increased after C. parvum injection. In situ hybridization demonstrated that AIM mRNA was expressed in Kupffer cells and exudate macrophages in the liver, especially in granulomas. Larger numbers of T cells and natural killer T (NKT) cells underwent apoptosis in the granulomas of AIM(-/-) mice, suggesting that AIM prevents apoptosis of NKT cells and T cells in C. parvum-induced inflammation. Recombinant AIM (rAIM) protein significantly inhibited apoptosis of NKT cells and T cells obtained from C. parvum-stimulated livers in vitro. These results indicate that AIM functions to induce resistance to apoptosis within NKT cells and T cells, and supports the host defense in granulomatous inflammation.

Targeting apoptosis in neurological disease using the herpes simplex virus

Herpes Simplex Viruses type 1 (HSV-1) and 2 (HSV-2) cause central nervous system (CNS) disease ranging from benign aseptic meningitis to fatal encephalitis. In adults, CNS infection with HSV-2 is most often associated with aseptic meningitis while HSV-1 frequently produces severe, focal encephalitis associated with high mortality and morbidity. Recent studies suggested that the distinct neurological outcome of CNS infection with the two viruses may be due to their distinct modulation of apoptotic cell death: HSV-1 triggers neuronal apoptosis, while HSV-2 is neuroprotective. Apoptosis also occurs in the etiology of neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease and Down's syndrome, and determines the loss of specific neuronal populations and the decline in cognitive functions. Notwithstanding, the therapy of these disorders may rely on the use of replication-defective HSV-1 vectors to deliver anti-apoptotic transgenes to the CNS. However, the recent discovery of a neuroprotective activity innate to the HSV-2 genome (the ICP10 PK gene) suggests that: i) ICP10 PK may constitute a novel therapeutic approach by targeting both the apoptotic cell death and the cognitive decline, and ii) HSV-2 may be more suitable than HSV-1 as a vector for targeting neuronal disease.

Dysregulation of apoptosis genes in hematopoietic malignancies

Ever since the discovery of Bcl-2 and the elucidation of its role in apoptosis, tremendous interest has arisen in prospects for triggering suicide of malignant cells by exploiting knowledge emerging from apoptosis research. In this review, we summarize information about the multiple genetic lesions which have been identified in apoptosis-regulatory genes of hematopoietic and lymphoid neoplasms. Emerging data about the structural and biochemical details of apoptosis proteins and their upstream regulators have reveal novel strategies for therapeutic intervention, some of which are under interrogation in clinical trials currently.

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.

The role of apoptosis in regulating hematopoiesis and hematopoietic stem cells

Apoptosis, or the ability of cells to die in an orderly and highly regulated manner, is essential for normal development and homeostasis of multicellular organisms. Diseases in which deregulation of this process is implicated include autoimmune diseases, cancer and Alzheimer's disease. The importance of apoptosis for the development and function of lymphoid cells has been extensively investigated. Less clear is the role apoptosis plays in regulating early progenitor and stem cell compartments. This question is being investigated using a transgenic mouse model, H2K-BCL-2, in which all hematopoietic cells have an increased resistance to apoptosis. The same transgenic model is also being used to address the question whether protection against apoptosis can increase system-wide resistance to lethal challenges such as irradiation and chemotherapeutic agents.

Solution structure of the antiapoptotic protein bcl-2

The structures of two isoforms of Bcl-2 that differ by two amino acids have been determined by NMR spectroscopy. Because wild-type Bcl-2 behaved poorly in solution, the structures were determined by using Bcl-2/Bcl-x(L) chimeras in which part of the putative unstructured loop of Bcl-2 was replaced with a shortened loop from Bcl-x(L). These chimeric proteins have a low pI compared with the wild-type protein and are soluble. The structures of the two Bcl-2 isoforms consist of 6 alpha-helices with a hydrophobic groove on the surface similar to that observed for the homologous protein, Bcl-x(L). Comparison of the Bcl-2 structures to that of Bcl-x(L) shows that although the overall fold is the same, there are differences in the structural topology and electrostatic potential of the binding groove. Although the structures of the two isoforms of Bcl-2 are virtually identical, differences were observed in the ability of the proteins to bind to a 25-residue peptide from the proapoptotic Bad protein and a 16-residue peptide from the proapoptotic Bak protein. These results suggest that there are subtle differences in the hydrophobic binding groove in Bcl-2 that may translate into differences in antiapoptotic activity for the two isoforms.

Apoptosis signaling

Apoptosis, a physiological process for killing cells, is critical for the normal development and function of multicellular organisms. Abnormalities in cell death control can contribute to a variety of diseases, including cancer, autoimmunity, and degenerative disorders. Signaling for apoptosis occurs through multiple independent pathways that are initiated either from triggering events within the cell or from outside the cell, for instance, by ligation of death receptors. All apoptosis signaling pathways converge on a common machinery of cell destruction that is activated by a family of cysteine proteases (caspases) that cleave proteins at aspartate residues. Dismantling and removal of doomed cells is accomplished by proteolysis of vital cellular constituents, DNA degradation, and phagocytosis by neighboring cells. This article reviews current knowledge of apoptosis signaling, lists several pressing questions, and presents a novel model to explain the biochemical and functional interactions between components of the cell death regulatory machinery.

Mammalian caspases: structure, activation, substrates, and functions during apoptosis

Apoptosis is a genetically programmed, morphologically distinct form of cell death that can be triggered by a variety of physiological and pathological stimuli. Studies performed over the past 10 years have demonstrated that proteases play critical roles in initiation and execution of this process. The caspases, a family of cysteine-dependent aspartate-directed proteases, are prominent among the death proteases. Caspases are synthesized as relatively inactive zymogens that become activated by scaffold-mediated transactivation or by cleavage via upstream proteases in an intracellular cascade. Regulation of caspase activation and activity occurs at several different levels: (a) Zymogen gene transcription is regulated; (b) antiapoptotic members of the Bcl-2 family and other cellular polypeptides block proximity-induced activation of certain procaspases; and (c) certain cellular inhibitor of apoptosis proteins (cIAPs) can bind to and inhibit active caspases. Once activated, caspases cleave a variety of intracellular polypeptides, including major structural elements of the cytoplasm and nucleus, components of the DNA repair machinery, and a number of protein kinases. Collectively, these scissions disrupt survival pathways and disassemble important architectural components of the cell, contributing to the stereotypic morphological and biochemical changes that characterize apoptotic cell death.

Pro-apoptotic apoptosis protease-activating factor 1 (Apaf-1) has a cytoplasmic localization distinct from Bcl-2 or Bcl-x(L)

How Bcl-2 and its pro-survival relatives prevent activation of the caspases that mediate apoptosis is unknown, but they appear to act through the caspase activator apoptosis protease-activating factor 1 (Apaf-1). According to the apoptosome model, the Bcl-2-like proteins preclude Apaf-1 activity by sequestering the protein. To explore Apaf-1 function and to test this model, we generated monoclonal antibodies to Apaf-1 and used them to determine its localization within diverse cells by subcellular fractionation and confocal laser scanning microscopy. Whereas Bcl-2 and Bcl-x(L) were prominent on organelle membranes, endogenous Apaf-1 was cytosolic and did not colocalize with them, even when these pro-survival proteins were overexpressed or after apoptosis was induced. Immunogold electron microscopy confirmed that Apaf-1 was dispersed in the cytoplasm and not on mitochondria or other organelles. After the death stimuli, Bcl-2 and Bcl-x(L) precluded the release of the Apaf-1 cofactor cytochrome c from mitochondria and the formation of larger Apaf-1 complexes, which are steps that presage apoptosis. However, neither Bcl-2 nor Bcl-x(L) could prevent the in vitro activation of Apaf-1 induced by the addition of exogenous cytochrome c. Hence, rather than sequestering Apaf-1 as proposed by the apoptosome model, Bcl-2-like proteins probably regulate Apaf-1 indirectly by controlling upstream events critical for its activation.

Bcl-xS and Bax induce different apoptotic pathways in PC12 cells

Apoptosis is regulated by the action of the Bcl-2 family of proteins, which includes anti- and pro-apoptotic members such as Bcl-xS and Bax. These proteins may differ from each other in structure, mechanism of action and interactions with anti-apoptotic signaling. The mechanism whereby Bax induces cell death has been studied in some cellular systems, but the mechanism of Bcl-xS-induced apoptosis is largely unknown. In this study we investigated and compared the apoptotic effects of Bcl-xS and Bax in the pheochromocytoma cell line, PC12 (a useful model system for studying neuronal apoptosis), and the extent to which they are protected by the survival factor, nerve growth factor (NGF). PC12 cells express endogenous Bcl-xS, Bax and Bcl-xL proteins. Subcellular fractionation revealed that Bax is presented mainly in the cytosolic and the heavy membrane fractions, Bcl-xS is present only in the cytosol, and the anti-apoptotic protein Bcl-xL is located mainly in the heavy membrane fraction. In contrast to the cytosolic localization of endogenous Bcl-xS, the exogenously overexpressed Bcl-xS is localized to the mitochondria. Overexpression of Bcl-xS or Bax induces cell death in the transfected cells. The cell death induced by overexpression of Bcl-xS was inhibited by coexpression of Bcl-xS with Bcl-2 or Bcl-xL, or by treatment with the broad-spectrum caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoro-methylketone (Z-VAD-FMK) or with NGF. The Bcl-2 mutants deltaC22, which lacks the transmembrane domain, and G145A (mI-3) were able to inhibit the death-inducing effect of Bcl-xS. These results therefore suggest that the apoptotic pathway induced by overexpression of Bcl-xS in PC12 cells can be controlled by Bcl-2 and Bcl-xL, is mediated by caspases, and can be inhibited by the NGF signaling pathway. The Bax-induced cell death was inhibited by co-expression of Bax with Bcl-2 or Bcl-xL, but was not inhibited by Z-VAD-FMK, NGF, or the Bcl-2 ml-3 or deltaC22 mutants. These results therefore suggest that Bax induces a caspase-independent cell death pathway which is blocked by Bcl-2 but not by the NGF signaling pathway. They further suggest that Bcl-xS and Bax induce different cell death pathways in PC12 cells.

FADD/MORT1 regulates the pre-TCR checkpoint and can function as a tumour suppressor

Productive rearrangement of the T-cell receptor (TCR) beta gene and signalling through the pre-TCR-CD3 complex are required for survival, proliferation and differentiation of T-cell progenitors (pro-T cells). Here we identify a role for death receptor signalling in early T-cell development using a dominant-negative mutant of the death receptor signal transducer FADD/MORT1 (FADD-DN). In rag-1(-/-) thymocytes, which are defective in antigen receptor gene rearrangement, FADD-DN bypassed the requirement for pre-TCR signalling, promoting pro-T-cell survival and differentiation to the more mature pre-T stage. Surprisingly, differentiation was not accompanied by the proliferation that occurs normally during transition to the pre-T stage. Consistent with a role for FADD/MORT1 in this cell division, FADD-DN rag-1(-/-) pro-T cells failed to proliferate in response to CD3epsilon ligation. Concomitant signalling through the pre-TCR and death receptors appears to trigger pro-T cell survival, proliferation and differentiation, whereas death receptor signalling in thymocytes that lack a pre-TCR induces apoptosis. Later in life all FADD-DN rag-1(-/-) mice developed thymic lymphoma, indicating that FADD/MORT1 can act as a tumour suppressor.

Indanocine, a microtubule-binding indanone and a selective inducer of apoptosis in multidrug-resistant cancer cells

BACKGROUND

Certain antimitotic drugs have antitumor activities that apparently result from interactions with nontubulin components involved in cell growth and/or apoptotic cell death. Indanocine is a synthetic indanone that has been identified by the National Cancer Institute's Developmental Therapeutics Program as having antiproliferative activity. In this study, we characterized the activity of this new antimitotic drug toward malignant cells.

METHODS

We tested antiproliferative activity with an MTT [i.e., 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay, mitochondrial damage and cell cycle perturbations with flow cytometry, caspase-3 activation with fluorometry, alterations of the cytoskeletal components with immunofluorescence, and antimicrotubule activity with a tubulin polymerization assay.

RESULTS/CONCLUSIONS

Indanocine is a cytostatic and cytotoxic indanone that blocks tubulin polymerization but, unlike other antimitotic agents, induces apoptotic cell death in stationary-phase multidrug-resistant cancer cells at concentrations that do not impair the viability of normal nonproliferating cells. Of the seven multidrug-resistant cell lines tested, three (i.e., MCF-7/ADR, MES-SA/DX5, and HL-60/ADR) were more sensitive to growth inhibition by indanocine than were their corresponding parental cells. Confluent multidrug-resistant cells (MCF-7/ADR), but not drug-sensitive cancer cells (MCF-7) or normal peripheral blood lymphocytes, underwent apoptotic cell death 8-24 hours after exposure to indanocine, as measured by sequential changes in mitochondrial membrane potential, caspase activity, and DNA fragmentation. Indanocine interacts with tubulin at the colchicine-binding site, potently inhibits tubulin polymerization in vitro, and disrupts the mitotic apparatus in dividing cells.

IMPLICATIONS

The sensitivity of stationary multidrug-resistant cancer cells to indanocine suggests that indanocine and related indanones be considered as lead compounds for the development of chemotherapeutic strategies for drug-resistant malignancies.

Epstein-Barr virus suppresses a G(2)/M checkpoint activated by genotoxins

Several Epstein-Barr virus (EBV)-negative Burkitt lymphoma-derived cell lines (for example, BL41 and Ramos) are extremely sensitive to genotoxic drugs despite being functionally null for the tumor suppressor p53. They rapidly undergo apoptosis, largely from G(2)/M of the cell cycle. 5-bromo-2'-deoxyuridine labeling experiments showed that although the treated cells can pass through S phase, they are unable to complete cell division, suggesting that a G(2)/M checkpoint is activated. Surprisingly, latent infection of these genotoxin-sensitive cells with EBV protects them from both apoptosis and cell cycle arrest, allowing them to complete the division cycle. However, a comparison with EBV-immortalized B-lymphoblastoid cell lines (which have functional p53) showed that EBV does not block apoptosis per se but rather abrogates the activation of, or signalling from, the checkpoint in G(2)/M. Furthermore, analyses of BL41 and Ramos cells latently infected with P3HR1 mutant virus, which expresses only a subset of the latent viral genes, showed that LMP-1, the main antiapoptotic latent protein encoded by EBV, is not involved in the protection afforded here by viral infection. This conclusion was confirmed by analysis of clones of BL41 stably expressing LMP-1 from a transfected plasmid, which respond like the parental cell line. Although steady-state levels of Bcl-2 and related proteins varied between BL41 lines and clones, they did not change significantly during apoptosis, nor was the level of any of these anti- or proapoptotic proteins predictive of the outcome of treatment. We have demonstrated that a subset of EBV latent gene products can inactivate a cell cycle checkpoint for monitoring the fidelity and timing of cell division and therefore genomic integrity. This is likely to be important in EBV-associated growth transformation of B cells and perhaps tumorigenesis. Furthermore, this study suggests that EBV will be a unique tool for investigating the intimate relationship between cell cycle regulation and apoptosis.

A portrait of the Bcl-2 protein family: life, death, and the whole picture

The Bcl-2 family of proteins are important regulators of cell death. They are comprised of two opposing factions, the proapoptotic versus the antiapoptotic members. Both are required for normal development and cellular homeostasis of the immune system and other tissues. However, in certain circumstances they may participate in the development of disease.

Expression of Bcl-2 and amplification of c-myc are frequent in basaloid squamous cell carcinomas of the esophagus

Basaloid squamous cell carcinoma (BSCC) of the esophagus is a rare, poorly differentiated variant of typical esophageal squamous cell carcinoma (SCC) characterized by high proliferative activity and frequent spontaneous apoptoses. In the present study, we investigated the expression of the apoptosis-suppressing protein Bcl-2 in 23 BSCC of the esophagus and 23 stage-matched typical esophageal SCC by means of immunohistochemistry. In addition, amplification of the apoptosis- and proliferation-inducing gene c-myc was determined by means of differential polymerase chain reaction. Bcl-2 expression was found significantly more often in BSCC than in SCC (86.9% vs. 17.4%, P < 0.0001). Amplification of c-myc was nearly twice as common in BSCC as in SCC (47.8% vs. 26.1%, not significant). Bcl-2 protein expression together with c-myc amplification was detected in 43.5% of the BSCC but in none of the typical SCC (P < 0.0001). Taken together, our findings indicate that the molecular pathogenesis of esophageal BSCC differs from that of typical SCC and frequently involves coactivation of c-myc and Bcl-2.

Transgenic models of lymphoid neoplasia and development of a pan-hematopoietic vector

The pathways to lymphoid neoplasia have been explored in a number of transgenic models. Because B lymphoid malignancies often involve translocation of an oncogene (e.g. myc, bcl-2, cyclin D1) to an immunoglobulin locus, resulting in its deregulated expression, the consequences of oncogene overexpression in lymphocytes can be evaluated with transgenes driven by an immunoglobulin regulatory element, such as an enhancer from the IgH locus. Mice bearing such transgenes have provided insight into the preneoplastic state, including alterations in the control of cellular proliferation, differentiation or apoptosis. They have also allowed studies on oncogene cooperation in vivo and the modulating effect of genetic background. Briefly reviewed here are the models studied in the authors' laboratories. Mice bearing myc and bcl-2 transgenes have received most attention but others studied include abl, ras, cyclin D1 and bmi-1 oncogenes. Also discussed is a new transgenic vector that should facilitate transgenic approaches to non-lymphoid leukemias. The vector bears elements from the promoter region of the vav gene, which is expressed almost exclusively in hematopoietic cells. It has proven capable of driving transgene expression throughout the hematopoietic compartment, including progenitor cells and their precursors. This novel vector should aid studies on many aspects of hematopoiesis, including the modeling of leukemogenesis.

Overexpression of bax associated with mutations in the loop-sheet-helix motif of p53

Recent investigations have revealed that mutations of the loop-sheet-helix motif of p53 is a significant factor for a poor prognosis in patients with non-small-cell lung cancer (NSCLC). To clarify this mechanism, bcl-2 and bax expression were evaluated in relation to mutations of p53. Tumor tissues of 203 patients with NSCLC were analyzed. Immunohistochemistry was performed to evaluate bcl-2 and bax expression, and polymerase chain reaction single-strand conformation polymorphism following direct sequencing was performed to investigate p53 status. A total of 79 carcinomas were bcl-2 positive, 146 carcinomas were bax positive, and 72 carcinomas had missense mutations of p53. There was no difference in bcl-2 expression in relation to p53 status. On the other hand, tumors with structural mutations of p53 had significantly lower expression of bax than those with wild-type p53 (P = 0.0026). In contrast, tumors with mutations of the loop-sheet-helix motif of p53 had significantly higher expression of bax than those with wild-type p53 (P = 0.0236). The frequency of a bcl-2/bax ratio of >/=1 was significantly lower in tumors with mutations of the loop-sheet-helix motif than that in tumors with wild-type p53 (P = 0.0240). The bcl-2/bax ratio status was a significant factor for a prognosis in patients with NSCLC (P = 0.0083). Mutations of the loop-sheet-helix motif of p53 were correlated with overexpression of bax, while other mutations of p53 were correlated with low levels of bax expression. This variation in pattern of bax expression in relation to mutant p53 might reflect the biological behavior of tumors in patients with bcl-2-positive NSCLC.

Bcl-2 family members do not inhibit apoptosis by binding the caspase activator Apaf-1

The Bcl-2 family of proteins regulates apoptosis, the cell death program triggered by activation of certain proteases (caspases). An attractive model for how Bcl-2 and its closest relatives prevent caspase activation is that they bind to and inactivate an adaptor protein required for procaspase processing. That model has been supported by reports that mammalian prosurvival Bcl-2 relatives bind the adaptor Apaf-1, which activates procaspase-9. However, the in vivo association studies reported here with both overexpressed and endogenous Apaf-1 challenge this notion. Apaf-1 could be immunoprecipitated together with procaspase-9, and the Apaf-1 caspase-recruitment domain was necessary and sufficient for their interaction. Apaf-1 did not bind, however, to any of the six known mammalian prosurvival family members (Bcl-2, Bcl-x(L), Bcl-w, A1, Mcl-1, or Boo), or their viral homologs adenovirus E1B 19K and Epstein-Barr virus BHRF-1. Endogenous Apaf-1 also failed to coimmunoprecipitate with endogenous Bcl-2 or Bcl-x(L), or with two proapoptotic relatives (Bax and Bim). Moreover, apoptotic stimuli did not induce Apaf-1 to bind to these family members. Thus, the prosurvival Bcl-2 homologs do not appear to act by sequestering Apaf-1 and probably instead constrain its activity indirectly.

Regulation of caspase activation in apoptosis: implications in pathogenesis and treatment of disease

1. Apoptosis is an essential process to remove excess, unwanted and harmful cells and maintain homeostasis. One of the key steps in apoptosis is activation of a group of proteases termed caspases. 2. Caspases are cysteine proteases that cleave their substrates after an aspartate residue. Approximately one dozen such proteases have been cloned during the past few years. While some caspases are largely responsible for the proteolytic processing of proinflammatory cytokines, such as interleukin (IL)-1 beta, others are directly involved in the execution of apoptosis. 3. Once apoptotic upstream caspases are activated in response to specific apoptotic stimuli, they can activate the downstream or effector class of caspases. Most proteins that are cleaved during apoptosis leading to the characteristic apoptotic morphology are targeted by the downstream caspases. The cleavage of these proteins by caspases can be either an activating or inactivating event for the function of a protein; however, in most cases, it contributes to the apoptotic phenotype of the cell. 4. Because caspase cleavage is the initiating event in most forms of apoptosis, it is a tightly controlled process with many checks and balances. An understanding of the regulation of caspases is providing novel ways for therapeutic intervention to modulate apoptotic behaviour of cells in many diseases that arise due to inappropriate apoptosis. 5. The present article will endeavour to discuss recent advances in our understanding of caspase regulation and will elaborate on how this knowledge is being used in the development of new classes of therapeutic molecules that can be used for the treatment of human ailments.