Inhibition of mitogen-activated kinase signaling sensitizes HeLa cells to Fas receptor-mediated apoptosis

Machine learning approaches reveal methylation signatures associated with pediatric acute myeloid leukemia recurrence

Acute myeloid leukemia (AML) is a severe hematological malignancy characterized by high recurrence rates, especially in pediatric patients, highlighting the need for reliable prognostic markers. This study proposes methylation signatures associated with AML recurrence using computational methods. DNA methylation data from 696 newly diagnosed and 194 relapsed pediatric AML patients were analyzed. Feature selection algorithms, including Boruta, least absolute shrinkage and selection operator, light gradient boosting machine, and Monte Carlo feature selection, were employed to screen and rank methylation sites strongly correlated with AML recurrence. Incremental Feature Selection was performed to evaluate these results, and optimal subsets were identified using Decision Tree and Random Forest methods. Several important methylation features, such as modifications in SLC45A4, S100PBP, TSPAN9, PTPRG, ERBB4, and PRKCZ, emerged from the intersection of all feature selection algorithms. Functional enrichment analysis indicated these genes participate in biological processes, including calcium-mediated signaling and regulation of binding. These findings are consistent with existing literature, suggesting that identified methylation features likely contribute to AML progression through alterations in gene expression levels. Therefore, this study provides a valuable reference for enhancing recurrence risk prediction models in AML and clarifying disease pathogenesis, as well as offering broader insights into mechanisms underlying other major diseases.

FAS mediates apoptosis, inflammation, and treatment of pathogen infection

The FAS cell surface death receptor, a member of the tumor necrosis factor receptor family, activates both apoptotic and non-apoptotic signaling upon interaction with its ligand FASL. It is critical in cell migration, invasion, immune responses, and carcinogenesis. Pathogen infection can influence host cells' behavior by modulating the FAS/FASL pathway, thereby influencing disease progression. Understanding the role of FAS signaling in the context of pathogen interactions is therefore crucial. This review examines FAS-mediated apoptotic and non-apoptotic signaling pathways, with particular emphasis on the mechanisms of apoptosis and inflammation induced by bacterial and viral infections. Additionally, it highlights therapeutic strategies, including drug, cytokine, antibody, and FASL recombinant protein therapies, providing new directions for treating pathogenic infections and cancers, as well as insights into developing novel therapeutic approaches.

Mitochondrial immune regulation and anti-tumor immunotherapy strategies targeting mitochondria

Cancer cells adapt to increasing energy and biosynthetic demands by reprogramming their metabolic pathways. Mitochondria are important organelles for the metabolic reprogramming of tumor cells. In addition to supplying energy, they play crucial roles in the survival, immune evasion, tumor progression, and treatment resistance of the hypoxic tumor microenvironment (TME) in cancer cells. With the development of the life sciences, scientists have gained an in-depth understanding of immunity, metabolism, and cancer, and numerous studies have emphasized that mitochondria are essential for tumor immune escape and the regulation of immune cell metabolism and activation. Moreover, recent evidence suggests that targeting the mitochondria-related pathway with anticancer drugs can initiate the killing of cancer cells by increasing the ability of cancer cells to be recognized by immune cells, tumor antigen presentation ability, and the anti-tumor function of immune cells. This review discusses the effects of mitochondrial morphology and function on the phenotype and function of immune cells under normal and TME conditions, the effects of mitochondrial changes in tumors and microenvironments on tumor immune escape and immune cell function, and finally focuses on the recent research progress and future challenges of novel anti-tumor immunotherapy strategies targeting mitochondria.

Mitochondria dysfunction in CD8+ T cells as an important contributing factor for cancer development and a potential target for cancer treatment: a review

CD8+ T cells play a central role in anti-tumor immunity. Naïve CD8+ T cells are active upon tumor antigen stimulation, and then differentiate into functional cells and migrate towards the tumor sites. Activated CD8+ T cells can directly destroy tumor cells by releasing perforin and granzymes and inducing apoptosis mediated by the death ligand/death receptor. They also secrete cytokines to regulate the immune system against tumor cells. Mitochondria are the central hub of metabolism and signaling, required for polarization, and migration of CD8+ T cells. Many studies have demonstrated that mitochondrial dysfunction impairs the anti-tumor activity of CD8+ T cells through various pathways. Mitochondrial energy metabolism maladjustment will cause a cellular energy crisis in CD8+ T cells. Abnormally high levels of mitochondrial reactive oxygen species will damage the integrity and architecture of biofilms of CD8+ T cells. Disordered mitochondrial dynamics will affect the mitochondrial number and localization within cells, further affecting the function of CD8+ T cells. Increased mitochondria-mediated intrinsic apoptosis will decrease the lifespan and quantity of CD8+ T cells. Excessively low mitochondrial membrane potential will cause the release of cytochrome c and apoptosis of CD8+ T cells, while excessively high will exacerbate oxidative stress. Dysregulation of mitochondrial Ca2+ signaling will affect various physiological pathways in CD8+ T cells. To some extent, mitochondrial abnormality in CD8+ T cells contributes to cancer development. So far, targeting mitochondrial energy metabolism, mitochondrial dynamics, mitochondria-mediated cell apoptosis, and other mitochondrial physiological processes to rebuild the anti-tumor function of CD8+ T cells has proved effective in some cancer models. Thus, mitochondria in CD8+ T cells may be a potential and powerful target for cancer treatment in the future.

Neuroprotective role of insulin-like growth factor 1 in auditory and other nervous systems

Insulin-like growth factor 1 (IGF1) exerts an influence on almost every organ system in the body and plays an important role in growth, development, and metabolism. In the nervous system, IGF1 acts by promoting the development and growth of neurons and glial cells, differentiation of Schwann cells and their migration to axons, neurite outgrowth, and neuronal survival. The lack of IGF1 is associated with several pathological conditions, including severe prenatal growth retardation, postnatal growth failure, microcephaly, mental retardation, and bilateral sensorineural hearing loss. In addition to its physiological effects, based on the findings of in vivo and in vitro experiments and clinical trials, IGF1 is considered to play a potential role in the treatment of various types of neuronal damage. In this review, we discuss the potential use of IGF1 as a therapeutic molecule in the nervous system: (1) auditory system, including hair cells, cochlear ribbon synapses, auditory nerve, and central nervous systems, and (2) other peripheral nervous systems, especially the olfactory system and facial nerve. The role of IGF1 in the progression of age-related sensory deficits, especially hearing loss and olfactory dysfunction, is also discussed. Recent studies on IGF1 demonstrated that exogenous IGF1 can be applied in many fields, thus supporting the continued evaluation of IGF1 as a potential therapeutic molecule. Additional scientific investigations should be conducted to further supplement recent findings.

Molecular Insights into the MAPK Cascade during Viral Infection: Potential Crosstalk between HCQ and HCQ Analogues

The mitogen-activated protein kinase (MAPK) pathway links the cell-surface receptors to the transcription machinery, transducing the extracellular signals into several outputs, which may also adapt the host defense mechanism to viral attacks. The Severe Acute Respiratory Syndrome CoronaVirus 2 (SARS-CoV-2) that causes the COrona VIrus Disease 2019 (COVID-19) has infected upwards of nearly 70 million people and worldwide has claimed more than 1,600,000 deaths. So far, there continues to be no specific treatment for this novel coronavirus-induced disease. In the search to control the global COVID-19 pandemic, some eastern and developing countries have approved a variety of treatments with controversial efficacy, among which is the use of the antimalarial hydroxychloroquine (HCQ). Interestingly, prior data had indicated that the HCQ/CQ could influence the MAPK cascade. The main aim of this review is to address molecular mechanisms, beyond drugs, that can be helpful against viral infection for this and future pandemics. We will highlight (1) the contribution of the MAPK cascade in viral infection and (2) the possible use of MAPK inhibitors in curbing viral infections, alone or in combination with HCQ and quinoline analogues. We are convinced that understanding the molecular patterns of viral infections will be critical for new therapeutical approaches to control this and other severe diseases.

hsa-microRNA-411-5p regulates proliferation, migration and invasion by targeting the hyaluronan mediated motility receptor in ovarian cancer

The mortality rate of ovarian cancer is the highest out of all gynecological malignancies worldwide. Therefore, it is important to understand the mechanisms of ovarian cancer, identify new biomarkers and develop targeted drugs. The role and molecular mechanisms of hsa-microRNA (miR)-411-5p in ovarian cancer have not been fully elucidated. The present study investigated the ovarian cancer cell lines OVCAR-8 and SKOV3. After transfection with miRNA mimics, cell proliferation was monitored by a proliferation assay. Furthermore, cell migration was measured by a cell wound healing assay and cell invasion was measured by Matrigel invasion assays. A miRNA luciferase reporter assay was used to analyze the relationship between miRNAs and the target gene HMMR, which was then further evaluated by gene differential analysis. In the current study, hsa-mir-411-5p was identified as a miRNA regulator of the hyaluronan mediated motility receptor, which negatively regulated the activity of ERK1/2 and ultimately inhibited ovarian cancer cell proliferation and motility. Although hsa-mir-411-5p may have different roles in other types of cancer, the present study suggested that miR-411-5p functions as a negative tumor regulator in ovarian cancer cells, displaying the potential of miR-411-5p as a biomarker for ovarian cancer.

Transcriptomics Analysis of Circular RNAs Differentially Expressed in Apoptotic HeLa Cells

Apoptosis is a form of regulated cell death that plays a critical role in survival and developmental homeostasis. There are numerous reports on regulation of apoptosis by protein-coding genes as well as small non-coding RNAs, such as microRNAs. However, there is no comprehensive investigation of circular RNAs (circRNA) that are differentially expressed under apoptotic conditions. We have performed a transcriptomics study in which we first triggered apoptosis in HeLa cells through treatment with four different agents, namely cisplatin, doxorubicin, TNF-α and anti-Fas mAb. Total RNAs isolated from control as well as treated cells were treated with RNAse R to eliminate the linear RNAs. The remaining RNAs were then subjected to deep-sequencing to identify differentially expressed circRNAs. Interestingly, some of the dys-regulated circRNAs were found to originate from protein-coding genes well-documented to regulate apoptosis. A number of candidate circRNAs were validated with qPCR with or without RNAse R treatment as well. We then took advantage of bioinformatics tools to investigate the coding potential of differentially expressed RNAs. Additionally, we examined the candidate circRNAs for the putative miRNA-binding sites and their putative target mRNAs. Our analyses point to a potential for circRNA-mediated sponging of miRNAs known to regulate apoptosis. In conclusion, this is the first transcriptomics study that provides a complete circRNA profile of apoptotic cells that might shed light onto the potential role of circRNAs in apoptosis.

Netrin 1 mediates protective effects exerted by insulin-like growth factor 1 on cochlear hair cells

Sensorineural hearing loss (SNHL) is mainly caused by the damage of cochlear hair cells (HCs). As HCs and supporting cells (SCs) do not proliferate in postnatal mammals, the loss of HCs and SCs is irreversible, emphasizing the importance of preserving their numbers to prevent SNHL. It is known that insulin-like growth factor 1 (IGF1) is instrumental in the treatment of SNHL. Our previous study indicates that IGF1 protects HCs against aminoglycoside by activating IGF1 receptor and its two major downstream pathways, PI3K/AKT and MEK/ERK, in SCs, which results in the upregulation of the expression of the Netrin1-encoding gene (Ntn1). However, the mechanisms underlying IGF1-induced protection of HCs via SC activation as well as the role of NTN1 in this process have not been elucidated. Here, we demonstrated that NTN1, similar to IGF1, promoted HC survival. NTN1 blocking antibody attenuated IGF1-induced HC protection from aminoglycoside, indicating that NTN1 is the effector molecule of IGF1 signaling during HC protection. In situ hybridization demonstrated that IGF1 potently induced Ntn1 expression in SCs. NTN1 receptors were abundantly expressed in the cochlea; among them, UNC5B mediated IGF1 protective effects on HCs, as NTN1 binding to UNC5B inhibited HC apoptosis. These results provide new insights into the mechanisms underlying IGF1 protection of cochlear HCs, suggesting a possibility of using NTN1 as a new treatment for SNHL.

Control of Mitochondrial Dynamics by Fas-induced Caspase-8 Activation in Hippocampal Neurons

Cells undergo apoptosis mainly via two pathways-the mitochondrial pathway and the cytosolic pathway. It has been well documented that activation of the mitochondrial pathway promotes mitochondrial fragmentation and inhibition of mitochondrial fragmentation partly represses cell death. However, the mitochondrial events following activation of the cytosolic pathway are less understood. In this study, we treated Fas-activating antibody and found mitochondrial fragmentation without cell death in hippocampal primary neurons and HT-22 cell lines. Fas antibody treatment, in fact, promoted rapid activation of caspase-8, while executioner caspase-3 activation was not observed. Furthermore, blockage of caspase-8 efficiently prevented Fas antibody-induced mitochondrial fragmentation. These results suggest that the cytosolic pathway induced by death receptor activation promotes caspase-8-dependent mitochondrial fission.

NK Cells Preferentially Target Tumor Cells with a Cancer Stem Cell Phenotype

Increasing evidence supports the hypothesis that cancer stem cells (CSCs) are resistant to antiproliferative therapies, able to repopulate tumor bulk, and seed metastasis. NK cells are able to target stem cells as shown by their ability to reject allogeneic hematopoietic stem cells but not solid tissue grafts. Using multiple preclinical models, including NK coculture (autologous and allogeneic) with multiple human cancer cell lines and dissociated primary cancer specimens and NK transfer in NSG mice harboring orthotopic pancreatic cancer xenografts, we assessed CSC viability, CSC frequency, expression of death receptor ligands, and tumor burden. We demonstrate that activated NK cells are capable of preferentially killing CSCs identified by multiple CSC markers (CD24(+)/CD44(+), CD133(+), and aldehyde dehydrogenase(bright)) from a wide variety of human cancer cell lines in vitro and dissociated primary cancer specimens ex vivo. We observed comparable effector function of allogeneic and autologous NK cells. We also observed preferential upregulation of NK activation ligands MICA/B, Fas, and DR5 on CSCs. Blocking studies further implicated an NKG2D-dependent mechanism for NK killing of CSCs. Treatment of orthotopic human pancreatic cancer tumor-bearing NSG mice with activated NK cells led to significant reductions in both intratumoral CSCs and tumor burden. Taken together, these data from multiple preclinical models, including a strong reliance on primary human cancer specimens, provide compelling preclinical evidence that activated NK cells preferentially target cancer cells with a CSC phenotype, highlighting the translational potential of NK immunotherapy as part of a combined modality approach for refractory solid malignancies.

Application of insulin-like growth factor-1 in the treatment of inner ear disorders

Sensorineural hearing loss (SNHL) is considered an intractable disease, given that hair and supporting cells (HCs and SCs) of the postnatal mammalian cochlea are unable to regenerate. However, with progress in regenerative medicine in the 21st century, several innovative approaches for achieving regeneration of inner ear HCs and SCs have become available. These methods include stem cell transplantation, overexpression of specific genes, and treatment with growth factors. Insulin-like growth factor-1 (IGF-1) is one of the growth factors that are involved in the development of the inner ear. Treatment with IGF-1 maintains HC numbers in the postnatal mammalian cochlea after various types of HC injuries, with activation of two major pathways downstream of IGF-1 signaling. In the aminoglycoside-treated neonatal mouse cochlear explant culture, promotion of the cell-cycle in SCs as well as inhibition of HC apoptosis was observed in the IGF-1-treated group. Activation of downstream molecules was observed in SCs and, in turn, SCs contribute to the maintenance of HC numbers. Using comprehensive analysis of the gene expression, the candidate effector molecules of the IGF-1 signaling pathway in the protection of HCs were identified as Netrin1 and Gap43. Based on these studies, a clinical trial has sought to investigate the effects of IGF-1 on SNHL. Sudden SNHL (SSHL) that was refractory to systemic steroids was treated with IGF-1 in a gelatin hydrogel and the outcome was compared with a historical control of hyperbaric oxygen therapy. The proportion of patients showing hearing improvement was significantly higher in the IGF-1-treatment group at 24 weeks after treatment than in the control group. A randomized clinical trial is ongoing to compare the effect of IGF-1 treatment with that of intra-tympanic steroids for SSHL that is refractory to systemic steroids.

Reversing multidrug resistance in hepatocellular carcinoma cells by inhibiting extracellular signal-regulated kinase/mitogen-activated protein kinase signaling pathway activity

The aim of the present study was to evaluate whether downregulation of extracellular signal-regulated kinase 1/2 (ERK1/2) is involved in conventional reversal methods and whether the inhibitors of the ERK signaling pathway reverse multidrug resistance (MDR) in hepatocellular carcinoma (HCC) cells. The sensitivities of SMMC7721 and BEL7402, and the MDR SMMC7721/Adriamycin (ADM) and BEL7402/ADM HCC cell lines to ADM were evaluated by CellTiter-Glo^® luminescent cell viability assay through calculating the half maximal inhibitory concentration (IC₅₀) of ADM. In addition, the expression levels of ERK1/2 and phosphorylated (p)ERK1/2 were determined by western blot analysis subsequent to treatment of the cells with PD98059, an MEK inhibitor, or sorafenib, a multikinase inhibitor. The results revealed that the ADM IC₅₀ for the SMMC7721/ADM cells was 16.44 times higher than that of the SMMC7721 cells (P<0.05), and the ADM IC₅₀ for the BEL7402/ADM cells was 20.34 times higher than that of the BEL7402 cells (P<0.05). Following treatment with PD98059 or sorafenib, the expression levels of pERK1/2 in the MDR cells decreased in a dose-dependent manner. Subsequent to treatment with 5 μM PD98059, the ADM IC₅₀ values for the SMMC7721/ADM and BEL7402/ADM cells were reduced to 0.8±0.056 and 1.583±0.284 μg/ml, respectively. Following treatment with 2.5 μM sorafenib, the ADM IC₅₀ values for the SMMC7721/ADM and BEL7402/ADM cells were reduced to 0.264±0.049 and 1.099±0.135 μg/ml, respectively. Subsequent to incubation with 4 μg/ml cyclosporine A (CsA), a classic MDR reversal agent, the ADM IC₅₀ values in the SMMC7721/ADM and BEL7402/ADM cells were reduced to 0.349±0.023 and 0.427±0.039 μg/ml, respectively. CsA treatment also increased the expression levels of pERK1/2 without affecting the total ERK1/2 levels. Therefore, the inhibition of ERK signaling pathway activity may be an important method to reverse the MDR of HCC cells, but is not unique.

A characterization of four B16 murine melanoma cell sublines molecular fingerprint and proliferation behavior

Background

One of the most popular and versatile model of murine melanoma is by inoculating B16 cells in the syngeneic C57BL6J mouse strain. A characterization of different B16 modified cell sub-lines will be of real practical interest. For this aim, modern analytical tools like surface enhanced Raman spectroscopy/scattering (SERS) and MTT were employed to characterize both chemical composition and proliferation behavior of the selected cells.

Methods

High quality SERS signal was recorded from each of the four types of B16 cell sub-lines: B164A5, B16GMCSF, B16FLT3, B16F10, in order to observe the differences between a parent cell line (B164A5) and other derived B16 cell sub-lines. Cells were incubated with silver nanoparticles of 50–100 nm diameter and the nanoparticles uptake inside the cells cytoplasm was proved by transmission electron microscopy (TEM) investigations. In order to characterize proliferation, growth curves of the four B16 cell lines, using different cell numbers and FCS concentration were obtained employing the MTT proliferation assay. For correlations doubling time were calculated.

Results

SERS bands allowed the identification inside the cells of the main bio-molecular components such as: proteins, nucleic acids, and lipids. An "on and off" SERS effect was constantly present, which may be explained in terms of the employed laser power, as well as the possible different orientations of the adsorbed species in the cells in respect to the Ag nanoparticles. MTT results showed that among the four tested cell sub-lines B16 F10 is the most proliferative and B164A5 has the lower growth capacity. Regarding B16FLT3 cells and B16GMCSF cells, they present proliferation ability in between with slight slower potency for B16GMCSF cells.

Conclusion

Molecular fingerprint and proliferation behavior of four B16 melanoma cell sub-lines were elucidated by associating SERS investigations with MTT proliferation assay.

Constitutive activity of Erk1/2 and NF-κB protects human endometrial stromal cells from death receptor-mediated apoptosis

Apoptosis in the human endometrium plays an essential role for endometrial receptivity and early implantation. A dysbalance of pro- and anti-apoptotic events in the secretory endometrium seems to be involved in implantation disorders and consecutive pregnancy complications. However, little is known about the mechanisms regulating apoptosis-sensitivity in the human endometrium. Therefore this study was performed to identify molecular mechanisms underlying the resistance toward apoptosis in human endometrial stromal cells (ESCs). Human ESCs were isolated from hysterectomy specimens and used as undifferentiated cells or after decidualization in vitro. Cells were incubated with an activating anti-Fas antibody, tumor-necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), TNF-α and inhibitors of protein- and RNA-syntheses, a caspase-inhibitor and inhibitors of extracellular signal regulated kinase (Erk)1/2, nuclear factor (NF)-κB and Akt. Apoptosis was measured by flow cytometric detection of hypodiploid nuclei. Caspase-activity was detected by luminescencent assays. Several pro- and anti-apoptotic molecules and the activation of Erk1/2, NF-κB and Akt were analyzed by in-cell Western assays or flow cytometry. Inhibition of protein- and RNA-syntheses differentially sensitized human ESCs for death receptor-mediated apoptosis in a caspase-dependent manner, based on the up-regulation of the death receptors Fas and TRAIL-R2. The constitutive activity of Erk1/2 and NF-κB could be identified as a reason for the apoptosis-resistance of human ESCs. These results suggest the pro-survival signaling pathways Erk1/2 and NF-κB as key regulators of the sensitivity of human ESCs for death receptor-mediated apoptosis. The modulation of these pathways might play an important role in the physiology of implantation.

REST is up-regulated by epidermal growth factor in HeLa cells and inhibits apoptosis by influencing histone H3 acetylation

REST (repressor element 1-silencing transcription factor) is a transcription factor that recruits histone deacetylases to silence gene transcription. REST appears to play a paradoxical role in cancer cells: it exhibits tumor suppressor activity or promotes tumorigenesis, depending upon the setting. The extracellular signaling molecules that control REST gene expression in cancer cells remain poorly understood. In this study, we report that REST expression in HeLa cells is elevated in cells exposed to epidermal growth factor or serum, whereas the rate of cell apoptosis is low. Apoptosis induced by serum withdrawal is significantly increased in HeLa cells treated with an antisense phosphorothioate oligodeoxynucleotide (AS ODN) capable of down-regulating REST expression, whereas in HeLa cells transfected with a REST expressing plasmid, REST overexpression reduces the marked apoptosis caused, in absence of serum, by exposure to an anti-Fas receptor antibody imitating the Fas ligand activity plus PD 98059, a blocker of extracellular signal-regulated kinase 1/2 activation. REST knockdown also reduces mRNA levels of the antiapoptotic protein Bcl-X(L) whereas in HeLa cells overexpressing REST, the reduction of Bcl-X(L) mRNA caused by the anti-Fas receptor antibody plus PD 98059 is significantly decreased. Finally, we report that acetylation of histone H3 is increased in HeLa cells exposed to AS ODN or anti-Fas receptor antibody, whereas it is reduced in cells transfected with the REST expressing plasmid. Our findings indicate that REST is a novel gene regulated by EGF in HeLa cells that potentially contributes to the modulation of apoptosis via epigenetic mechanisms.

SBDS-deficiency results in deregulation of reactive oxygen species leading to increased cell death and decreased cell growth

BACKGROUND

Shwachman-Diamond syndrome (SDS) is characterized by reduced hematopoietic and exocrine pancreatic cell numbers and a marked propensity for leukemia. Most patients have mutations in the SBDS gene. We previously reported that SBDS-deficient cells overexpress Fas, undergo accelerated spontaneous and Fas-mediated apoptosis and grow slowly. However the mechanism of how SBDS regulates apoptosis remains unknown. Several studies have shown that reactive oxygen species (ROS) regulate cell growth and spontaneous and Fas-mediated cell death. Therefore, we hypothesized that SBDS-deficiency disrupts ROS regulation and subsequently increases sensitivity to Fas stimulation and reduced cell growth.

PROCEDURE

SBDS was knocked down in HeLa cervical cancer cells and TF-1 myeloid cells using short hairpin RNA. ROS levels were evaluated by oxidation of 2',7'-dichlorodihydrofluorescein diacetate. Apoptosis and cell growth were evaluated with and without antioxidants by annexin V/propidium iodide and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays, respectively.

RESULTS

We found that shRNA mediated SBDS-knockdown resulted in a significant increase in ROS levels compared to control cells. Fas stimulation further increased ROS levels in the SBDS-knockdown HeLa cells more than in the controls. Importantly, balancing ROS levels by antioxidants rescued SBDS-deficient cells from spontaneous and Fas-mediated apoptosis and reduced cell growth.

CONCLUSIONS

ROS levels are increased in SBDS-deficient cells, which leads to increased apoptosis and decreased cell growth. Increased baseline and Fas-mediated ROS levels in SBDS-deficient cells can enhance the sensitivity to Fas stimulation. By balancing ROS levels, antioxidants can improve cell growth and survival in SBDS-deficient cells.

Increased expression but not sensitivity to Fas/CD95 in glioblastoma cells depleted of mitochondrial DNA

Mitochondria and Fas (CD95) play a role in tumorigenicity and apoptosis. In the present study, the functional relationship of mitochondria to Fas in mediating apoptosis was investigated. Glioblastoma cells (DBTRGO5MG, U87) were depleted of mitochondrial DNA (mtDNA) by treatment with ethidium bromide (Rho(-) cells). Compared to Rho(+) cells, Rho(-) cells showed enhanced expression of Fas at the cell surface. Indeed, when Rho(+) cells were treated with mitochondrial respiratory chain complex inhibitors, Fas cell surface expression was noted to increase in a similar fashion to the depletion of mtDNA in both cell lines. However, when cells were evaluated for sensitivity to apoptosis using Fas-engagement, there was no difference between the Rho(+) and Rho(-) cells in either cell line. By contrast, sensitivity to the cytotoxic agent cis-diammine-dichloroplatinum (cisplatin) was markedly increased in the Rho(-) cells, which expressed higher levels of cell surface Fas. Expression of Fas is increased with the depletion of mtDNA and respiratory complex inhibitors. However, this increase in expression does not necessarily translate to an increase in sensitivity to Fas-engagement, although there is an increase in the sensitivity of depleted cells to cytotoxic agents such as cisplatin.

Silencing of Nuclear Mitotic Apparatus protein (NuMA) accelerates the apoptotic disintegration of the nucleus

One main feature of apoptosis is the sequential degradation of the nuclear structure, including the fragmentation of chromatin and caspase-mediated cleavage of various nuclear proteins. Among these proteins is the Nuclear Mitotic Apparatus protein (NuMA) which plays a specific role in the organization of the mitotic spindle. The exact function of NuMA in the interphase nucleus is unknown, but a number of reports have suggested that it may play a role in chromatin organization and/or gene expression. Here we show that upon cleavage in apoptotic cells, the N-terminal cleavage fragment of NuMA is solubilized while the C-terminal fragment remains associated with the condensed chromatin. Using pancaspase inhibitor z-VAD-fmk and caspase-3 deficient MCF-7 cells, we further show that the solubilization is dependent on caspase-mediated cleavage of NuMA. Finally, the silencing of NuMA by RNAi accelerated nuclear breakdown in apoptotic MCF-7 cells. These results suggest that NuMA may provide structural support in the interphase nucleus by contributing to the organization of chromatin.

MEK inhibition suppresses cell invasion and migration in ovarian cancers with activation of ERK1/2

The extracellular-regulated kinase (ERK) signaling pathway plays an important role in regulating the malignant potential of a cancer cell. However, the effect of ERK signaling on cancer metastasis is not clearly understood. In the present study, we examined the status of ERK activation in 88 ovarian carcinomas in order to clarify the clinicopathological and prognostic significance of phosphorylated ERK1/2 (p-ERK1/2). p-ERK1/2 expression was identified in 37 (42%) of 88 ovarian carcinomas. There was no significant correlation between p-ERK1/2 expression and any of the clinicopathological factors tested. No significant correlation between p-ERK1/2 expression and overall survival was found in patients with ovarian carcinoma treated with platinum and taxane chemotherapy (P=0.426). Next, to clarify the role of ERK1/2 activation in ovarian cancers, we inactivated ERK1/2 in ovarian cancer cells using the MEK inhibitor, CI-1040, which prevents ERK1/2 activation. Based on simulated wound healing and invasion chamber assays, we found that the motility and invasion of ES2 and MPSC1 cells with p-ERK1/2 were significantly reduced (P<0.01) after treatment with CI-1040. By contrast, CI-1040 did not have any effect on KF28 cells, which were negative for p-ERK1/2. Twist was down-regulated simultaneously with p-ERK1/2 following treatment of ES2 and MPSC1 cells with CI-1040. Immunohistochemistry of ovarian carcinoma tissue revealed that the increased expression of p-ERK1/2 significantly correlated with Twist expression (P<0.01). The findings in this study provide new insight into the biological role of ERK signaling in ovarian carcinomas. Additionally, our observations have an important therapeutic implication for patients with ovarian cancers that express p-ERK1/2 as these patients may potentially benefit from CI-1040 therapy.

Bax is upregulated by p53 signal pathway in the SPE B-induced apoptosis

We identify integrin α(v)β(3) and Fas as receptors for the streptococcal pyrogenic exotoxin B (SPE B), and G308S (SPE B mutant, glycine at residue 308 is changed to serine), which interacts with Fas only, in our previous study. Here, we explore the signal pathways that regulate proapoptotic protein expression after SPE B stimulation. We find that both SPE B and G308S can stimulate the serine phosphorylation of p53, and p53 phosphorylation is inhibited by the anti-Fas antibody but not by anti-α(V)β(3) antibody. p38 inhibitor and siRNA decrease the activation and translocation of p53 into the nucleus, which executes its transcription activity. These results indicate that after SPE B treatment, p53 is activated and p38 is the upstream of p53. p38 siRNA also decreases the binding of p53 to the bax promoter and interferes with the association of p53 and STAT1. p53, p38, and STAT1 siRNAs downregulate SPE B-induced Bax expression. This shows that SPE B activates the bax promoter via p38/p53 signal pathways through the Fas receptor, and that STAT1 acts as a coactivator of p53. In addition, p38 and p53 siRNAs inhibit SPE B-induced apoptosis. This is consistent with the findings that SPE B upregulates Bax expression through p38/p53 signal pathways that enhance cell apoptosis.

Procaspase 8 and Bax are up-regulated by distinct pathways in Streptococcal pyrogenic exotoxin B-induced apoptosis

We have previously identified integrin alpha(v)beta(3) and Fas as receptors for the streptococcal pyrogenic exotoxin B (SPE B), and G308S, a mutant of SPE B that binds to Fas only. In the current study we found that after binding to alpha(v)beta(3), SPE B stimulated the tyrosine phosphorylation of JAK2 and STAT1. STAT1 tyrosine phosphorylation was inhibited by a JAK2 inhibitor, AG490, short interfering RNA (siRNA) silencing of JAK2, and anti-alpha(V)beta(3) antibody. AG490 also decreased the binding of tyrosine-phosphorylated STAT1 to the procaspase 8 promoter, decreasing procaspase 8 expression, suggesting that SPE B up-regulates procaspase 8 expression via the JAK2/STAT1 pathway. Alternatively, both SPE B and G308S increased STAT1 phosphorylation at serine 727, which was inhibited by anti-Fas antibody, a p38 inhibitor, SB203580, and siRNA silencing of p38. In addition, SPE B and G308S increased binding of serine-phosphorylated STAT1 to the Bax promoter and Bax expression, which was decreased by SB203580. SPE B and G308S-stimulated Bax expression was also inhibited by anti-Fas antibody. These findings suggest that Fas mediate SPE B-induced Bax expression through p38. Silencing of JAK2 or p38 by siRNA blocked procaspase 8 expression, whereas only p38 siRNA decreased Bax expression. Furthermore, JAK2 inhibition and p38 inhibition reduced SPE B-induced apoptosis, but only p38 inhibition blocked G308S-induced apoptosis.

Effect of cocaine on Fas-associated protein with death domain in the rat brain: individual differences in a model of differential vulnerability to drug abuse

This study was designed to (1) assess the effects of cocaine on Fas-associated protein with death domain (FADD) system and its role in the activation of apoptotic vs nonapoptotic events and (2) ascertain whether animals selectively bred for their differential propensity to drug-seeking show differences in FADD levels or response to cocaine. Acute cocaine, through D(2) dopamine receptors, induced a dose-response increase in FADD protein in the cortex, with opposite effects over pFADD (Ser191/194), and no induction of apoptotic cell death (poly-(ADP-ribose) polymerase cleavage). FADD was increased by cocaine in cytosol (approximately 142%), membranes (approximately 23%) and nucleus (approximately 54%). The modulation of the FADD system showed tolerance of the acute effect over time, as well as a compensatory response on withdrawal that mirrored the acute effect--ie a transient FADD decrease on day 3 of withdrawal, both at mRNA and protein levels. In a second experiment, possible FADD differences were investigated in rats selectively bred for differential responsiveness to novelty, propensity for drug-seeking and cocaine sensitization. High-responders (HR), who were more prone to drug abuse, exhibited higher FADD and lower pFADD levels than low-responder (LR) rats. However, HR and LR rats showed similar rates of cocaine-induced apoptosis, and exhibited a parallel impact of cocaine over FADD within each phenotype. Thus, FADD is a signaling protein modulated by cocaine, regulating apoptosis/proliferative mechanisms in relation to its FADD/pFADD content. Interestingly, animals selectively bred for differential propensity to substance abuse show basal differences in the expression of this protein, suggesting FADD may also be a molecular correlate for the HR/LR phenotype.

SBDS-deficiency results in specific hypersensitivity to Fas stimulation and accumulation of Fas at the plasma membrane

Shwachman-Diamond syndrome (SDS) is an inherited disorder characterized by reduced cellularity in the bone marrow and exocrine pancreas. Most patients have mutations in the SBDS gene, whose functions are unknown. We previously showed that cells deficient in the SBDS protein are characterized by accelerated apoptosis and Fas hypersensitivity, suggesting that the protein might play an important role in Fas-mediated apoptosis. To study the mechanism of Fas hypersensitivity, we compared shRNA-mediated SBDS-knockdown HeLa cells and SDS marrow CD34+ cells for their sensitivity to several groups of apoptosis inducers. Marked hypersensitivity was noticed in response to Fas stimulation, but not to tumor necrosis factor-alpha, DNA-damaging agents, transcription inhibition or protein synthesis inhibition. To identify the Fas signaling factors that cause hypersensitivity, we analyzed the expression of the pathway's proteins. We found that Fas accumulated at the plasma membrane in SBDS-knockdown cells with corresponding expression of Fas transcript 1, the main Fas transcript which contains both the transmembrane domain and the death domain. However, the total levels of Fas protein and mRNA were comparable to controls, and Fas internalization occurred normally. Expression of FADD, caspase-8 and -3 were not elevated and the pathway inhibitors: ERK, c-FLIP and XIAP were not decreased. These results suggest that SBDS loss results in abnormal accumulation of Fas at the plasma membrane, where it sensitizes the cells to stimulation by Fas ligand.

Identification of malignancy factors by analyzing cystic tumors of the pancreas

AIM

The diversity in the aggressiveness of cystic tumors of the pancreas - ranging from the usually benign serous cystadenoma to lesions of variable degrees of malignancy - was utilized for the identification of molecular factors that are involved in the occurrence of malignancy.

METHODS

We analyzed the transcript profiles of different cystic tumor types. The results were confirmed at the protein level by immunohistochemistry. Also, functional studies with siRNA silencing were performed.

RESULTS

Expression variations at the RNA and protein level were identified that are closely correlated with the degree of malignancy. Besides, all tumors could be classified effectively by this means. Many of the identified factors had not previously been known to be associated with malignant cystic lesions. siRNA silencing of the gene with the most prominent variation - the anti-apoptotic factor FASTK (Fas-activated serine/threonine kinase) - revealed a regulative effect on several genes known to be relevant to the development of tumors.

CONCLUSION

By a molecular analysis of rare types of pancreatic cancer, which are less frequent in terms of disease, variations could be identified that could be critical for the regulation of malignancy and thus relevant to the treatment of also the majority of pancreatic tumors.

CD73 participates in cellular multiresistance program and protects against TRAIL-induced apoptosis

The molecular mechanisms underlying the multiresistant phenotype of leukemic and other cancer cells are incompletely understood. We used expression arrays to reveal differences in the gene expression profiles of an apoptosis-resistant T cell leukemia clone (A4) and normally apoptosis-sensitive parental Jurkat cells. CD73 (ecto-5'-nucleotidase) was the most up-regulated gene in the resistant A4 cell clone. A4 cells displayed CD73 surface expression and significant ecto-5'-nucleotidase activity. The role of CD73 was confirmed by transfection of wild-type CD73 into native Jurkat cells, which led to specific resistance against TRAIL-induced apoptosis, but not other types of apoptosis. The protective role of CD73 was further confirmed by small interfering RNA-mediated down-regulation of CD73, restoring TRAIL sensitivity. CD73-mediated resistance was independent of enzymatic activity of CD73, but was reliant on the anchoring of the protein to the membrane via GPI. We suggest that the inhibition of TRAIL signaling works through interaction of CD73 with death receptor 5, as CD73 and death receptor 5 could be coimmunoprecipitated and were shown to be colocalized in the plasma membrane by confocal microscopy. We propose that CD73 is a component of multiresistance machinery, the transcription of which is activated under selective pressure of the immune system.

Molecular mechanisms contributing to glutamine-mediated intestinal cell survival

Glutamine, the most abundant amino acid in the bloodstream, is the preferred fuel source for enterocytes and plays a vital role in the maintenance of mucosal growth. The molecular mechanisms regulating the effects of glutamine on intestinal cell growth and survival are poorly understood. Here, we show that addition of glutamine (1 mmol/l) enhanced rat intestinal epithelial (RIE)-1 cell growth; conversely, glutamine deprivation increased apoptosis as noted by increased DNA fragmentation and caspase-3 activity. To delineate signaling pathways involved in the effects of glutamine on intestinal cells, we assessed activation of extracellular signal-related kinase (ERK), protein kinase D (PKD), and phosphatidylinositol 3-kinase (PI3K)/Akt, which are important pathways in cell growth and survival. Addition of glutamine activated ERK and PKD in RIE-1 cells after a period of glutamine starvation; inhibition of ERK, but not PKD, increased cell apoptosis. Conversely, glutamine starvation alone increased phosphorylated Akt; inhibition of Akt enhanced RIE-1 cell DNA fragmentation. The role of ERK was further delineated using RIE-1 cells stably transfected with an inducible Ras. Apoptosis was significantly increased following ERK inhibition, despite Ras activation. Taken together, these results identify a critical role for the ERK signaling pathways in glutamine-mediated intestinal homeostasis. Furthermore, activation of PI3K/Akt during periods of glutamine deprivation likely occurs as a protective mechanism to limit apoptosis associated with cellular stress. Importantly, our findings provide novel mechanistic insights into the antiapoptotic effects of glutamine in the intestine.

A crucial role of plasma membrane-associated sialidase in the survival of human cancer cells

Human plasma membrane-associated sialidase (NEU3), a key enzyme for ganglioside degradation, is markedly upregulated in human cancers, leading to apoptosis suppression. To define molecular mechanisms and the possible target for NEU3, its encoding gene was silenced by small interference RNA (siRNA) or overexpressed in human cells. NEU3 siRNA-induced apoptosis with no special stimuli in HeLa cells, accompanied with decreased Bcl-xL and increased mda7 and GM3 synthase mRNA levels, whereas overexpression resulted in the opposite. Carcinoma HT-29 and MCF-7 cells appeared to be similarly affected, but normal cell lines demonstrated no significant changes. NEU3 siRNA was found to inhibit and NEU3 overexpression to stimulate Ras activation with consequent influence on extracellular signal-regulated kinases and Akt. Ras activation by NEU3 was abrogated by PP2 (src inhibitor) or AG1478 (epidermal growth factor receptor (EGFR) inhibitor), and NEU3 actually enhanced EGF-stimulated tyrosine-phosphorylation of EGFR, suggesting that the upstream targets might be tyrosine kinases including src and EGFR, and the subsequent stimulation of Ras cascade leads to the inhibition of cell apoptosis. Glycolipid changes observed seemed to be one of the causes of the cell effects. NEU3 may thus be an essential gene for cancer cell survival and siRNAs targeting this protein could have utility for gene-based therapy of human cancers.

Down-regulation of sialidase NEU4 may contribute to invasive properties of human colon cancers

In mammalian cells, four types of sialidase have been described and found to behave in different ways during carcinogenesis. We previously demonstrated that a human sialidase associated with plasma membranes (NEU3) is up-regulated in human colon cancer and is involved in suppression of apoptosis. Here we document altered expression of another human sialidase, the recently identified NEU4, and evidence of its influence on the malignant phenotype in colon cancers. Human colon mucosa was relatively rich in NEU4, which has been observed to possess short and long isoforms, but hardly contained the latter form. In clear contrast to the NEU3 case, the levels of mRNA for this sialidase were found by quantitative RT-PCR to be markedly decreased in colon cancers. In cultured human colon cancer cells, the enzyme was up-regulated in the early stage of apoptosis induced by either the death ligand TRAIL or serum-depletion, and transfection of NEU4 resulted in acceleration of apoptosis and in decreased invasion and motility. The siRNA-mediated NEU4 targeting, on the other hand, caused a significant inhibition of apoptosis and promotion of invasion and motility. Lectin blot analyses revealed that desialylated forms of nearly 100 kDa glycoproteins were prominently increased with PNA in NEU4 transfectants, whereas only slight changes in glycolipids were detected as assessed by thin layer chromatography. These results suggest that NEU4 plays important roles for maintenance of normal mucosa mostly through desialylation of glycoproteins and that down-regulation may contribute to invasive properties of colon cancers.

Effects of opiate drugs on Fas-associated protein with death domain (FADD) and effector caspases in the rat brain: regulation by the ERK1/2 MAP kinase pathway

This study was designed to assess the effects of opiate treatment on the expression of Fas-associated protein with death domain (FADD) in the rat brain. FADD is involved in the transmission of Fas-death signals that have been suggested to contribute to the development of opiate tolerance and addiction. Acute treatments with high doses of sufentanil and morphine (mu-agonists), SNC-80 (delta-agonist), and U50488H (kappa-agonist) induced significant decreases (30-60%) in FADD immunodensity in the cerebral cortex, through specific opioid receptor mechanisms (effects antagonized by naloxone, naltrindole, or nor-binaltorphimine). The cannabinoid CB1 receptor agonist WIN 55,212-2 did not alter FADD content in the brain. Chronic (5 days) morphine (10-100 mg/kg), SNC-80 (10 mg/kg), or U50488H (10 mg/kg) was associated with the induction of tachyphylaxis to the acute effects. In morphine- and SNC-80-tolerant rats, antagonist-precipitated (2 h) or spontaneous withdrawal (24-48 h) induced a new and sustained inhibition of FADD (13-50%). None of these treatments altered the densities of caspases 8/3 (including the active cleaved forms) in the brain. Pretreatment of rats with SL 327 (a selective MEK1/2 inhibitor that blocks ERK activation) fully prevented the reduction of FADD content induced by SNC-80 in the cerebral cortex (43%) and corpus striatum (29%), demonstrating the direct involvement of ERK1/2 signaling in the regulation of FADD by the opiate agonist. The results indicate that mu- and delta-opioid receptors have a prominent role in the modulation of FADD (opposite to that of Fas) shortly after initiating treatment. Opiate drugs (and specifically the delta-agonists) could promote survival signals in the brain through inhibition of FADD, which in turn is dependent on the activation of the antiapoptotic ERK1/2 signaling pathway.

Fas/FasL signaling allows extracelluar-signal regulated kinase to regulate cytochrome c release in oridonin-induced apoptotic U937 cells

Previously, we found that human histocytic lymphoma U937 cells possessed high susceptibility to oridonin-induced cell death, but the molecular mechanisms in response to oridonin remain unclear. In this study, U937 cells showed susceptible to apoptosis induced by 27 microM oridonin and an agonistic anti-Fas IgM mAb (CH-11) (500 ng/ml) as a Fas-sensitized positive control. Caspase 8 inhibitor z-IETD, but neither caspase 1 inhibitor Ac-YVAD nor caspase 10 inhibitor z-AEVD, effectively blocked oridonin-induced cell death as well as DNA fragmentation. Western blot analysis showed the up-regulated expression of Fas, FasL, and FADD, and down-regulated expression of procaspase 8, suggesting that Fas/FasL pathway was activated in oridonin-induced cell apoptosis. Further, stimulation of U937 cells with oridonin and CH11 resulted in significant ERK MAPK activation. However, inhibition of ERK by PD98059 reversed oridonin-induced cell death as well as the activation of caspase 8, indicating that ERK-mediated control occured upstream of caspase 8. Simultaneously, ERK activation accounted for the release of cytochrome c, but failed to influence decreased Bcl-2 expression induced by oridonin. Taken together, these results suggest that Fas/FasL signaling pathway-mediated ERK activation sensitized U937 cells to mitochondrial pathway-mediated apoptosis induced by oridonin.

Involvement of protein kinase B and mitogen-activated protein kinases in experimental normothermic liver ischaemia-reperfusion injury

BACKGROUND

This study evaluated the role of protein kinase B (PKB), phosphatidylinositol 3-kinase (PI3-K), Bcl-2-associated death protein (BAD) and mitogen-activated protein kinases (MAPKs) in normothermic ischaemia-reperfusion (IR)-induced apoptosis in rat liver.

METHODS

Rats were divided into two groups that received either phosphate-buffered saline (control) or the caspase inhibitor Z-Asp-2,6-dichorobenzoyloxymethylketone (Z-Asp-cmk), injected intravenously 2 min before the induction of 120 min of normothermic liver ischaemia. Liver apoptosis was assessed by the terminal deoxyribonucleotidyltransferase-mediated dUTP nick end labelling (TUNEL) method. PI3-K, PKB, BAD and MAPK activities were measured in ischaemic and non-ischaemic lobes at various times after reperfusion.

RESULTS

The number of TUNEL-positive cells was significantly decreased after pretreatment with Z-Asp-cmk. In controls, PI3-K and PKB activities and BAD phosphorylation were inhibited in ischaemic liver lobes. The MAPKs (extracellular signal-regulated kinases, c-Jun N-terminal kinase and p38) showed different patterns of activation during IR. PKB activity was not modified by pretreatment with Z-Asp-cmk.

CONCLUSION

Induction of apoptosis during IR liver injury might be triggered by inactivation of the antiapoptotic PI3-K-PKB pathway and activation of the proapoptotic MAPKs.

Activation of mitogen-activated protein kinase is required for migration and invasion of placental site trophoblastic tumor

Placental site trophoblastic tumor (PSTT) is a gestational neoplasm derived from the extravillous (intermediate) trophoblast of the implantation site. PSTT is characterized by a highly invasive phenotype, but the molecular mechanisms are poorly understood. In this report, we demonstrate that PSTTs expressed the activated (phosphorylated) form of mitogen-activated protein kinase (MAPK) in 84% of cases, whereas the normal extravillous trophoblastic cells did not. To characterize the role of MAPK activation in PSTT, we established the first PSTT cell culture, IST-2, from a surgically resected PSTT. IST-2 cells expressed HLA-G and Mel-CAM but not E-cadherin, an immunophenotype characteristic of PSTT. IST-2 cells were highly motile and invasive in culture as compared to choriocarcinoma JEG-3 cells and normal extravillous trophoblastic cells. Based on wound assay, time-lapse videomicroscopy for cell tracking, and invasion chamber assays, we found that the motility and invasion of IST-2 cells were significantly reduced (P<0.01) after treatment with the MEK inhibitors CI-1040 and PD 59089, which prevent activation of MAPK. In contrast, neither compound had any effect on normal extravillous trophoblastic cells or JEG-3 cells. In conclusion, our findings demonstrate a functional role of MAPK activation in the motility and invasion of PSTT.

FLIP protects against hypoxia/reoxygenation-induced endothelial cell apoptosis by inhibiting Bax activation

Hypoxia/reoxygenation causes cell death, yet the underlying regulatory mechanisms remain partially understood. Recent studies demonstrate that hypoxia/reoxygenation can activate death receptor and mitochondria-dependent apoptotic pathways, involving Bid and Bax mitochondrial translocation and cytochrome c release. Using mouse lung endothelial cells (MLEC), we examined the role of FLIP, an inhibitor of caspase 8, in hypoxia/reoxygenation-induced cell death. FLIP protected MLEC against hypoxia/reoxygenation by blocking both caspase 8/Bid and Bax/mitochondrial apoptotic pathways. FLIP inhibited Bax activation in wild-type and Bid(-/-) MLEC, indicating independence from the caspase 8/Bid pathway. FLIP also inhibited the expression and activation of protein kinase C (PKC) (alpha, zeta) during hypoxia/reoxygenation and promoted an association of inactive forms of PKC with Bax. Surprisingly, FLIP expression also inhibited death-inducing signal complex (DISC) formation in the plasma membrane and promoted the accumulation of the DISC in the Golgi apparatus. FLIP expression also upregulated Bcl-X(L), an antiapoptotic protein. In conclusion, FLIP decreased DISC formation in the plasma membrane by blocking its translocation from the Golgi apparatus and inhibited Bax activation through a novel PKC-dependent mechanism. The inhibitory effects of FLIP on Bax activation and plasma membrane DISC formation may play significant roles in protecting endothelial cells from the lethal effects of hypoxia/reoxygenation.

Ex vivo study of MAPK profiles correlated with parameters of apoptosis during cervical carcinogenesis

Cervical cancer is a leading cause of death in developing countries and is the second highest occurring cancer in women all over the world. The progression of cancer is a multistep process affecting aspects of cellular function such as proliferation, differentiation and apoptosis. Mitogen activated protein kinases (MAPKs), which include p38-MAPK, c-Jun NH(2)-terminal kinase (JNK) and extracellular signal-regulated kinases (ERKs) are closely associated with cell proliferation and apoptosis and the balance between them could determine a cell's fate. Despite the expanding research effort in vitro, little is known about MAPK activation in clinical specimens of cervical cancer. Therefore, the aim of this ex vivo study was to correlate the phosphorylation status (activity) of MAPKs (p38-MAPK, JNK and ERK), as well as poly (ADP-ribose) polymerase (PARP) and caspase-3 (two cellular markers of apoptosis), during the different stages of cervical carcinogenesis, to observe whether correlations between MAPK activities and apoptosis during the disease process exist. Decreased p38-MAPK phosphorylation was found in the carcinoma (Ca) group) compared to the normal tissues, as well when the low grade squamous intraepithelial lesion--LSIL) group and high grade squamous intraepithelial lesion--HSIL) group were compared with the Ca group. Interestingly, a significant decrease in ERK44 phosphorylation was observed in Ca when compared to LSIL and HSIL. There was also a significant decrease in JNK phosphorylation in Ca when compared with normal tissue and HSIL. As expected, caspase-3 activation and PARP cleavage was significantly lower in Ca when compared with normal tissue. Our results present the first evidence of in vivo involvement of MAPKs in cervical cancer and indicate a possible correlation between MAPK activities and apoptosis in the disease process.

Rapid turnover of c-FLIPshort is determined by its unique C-terminal tail

The caspase-8 inhibitor c-FLIP exists as two splice variants, c-FLIP(L) and c-FLIP(S), with distinct roles in death receptor signaling. The mechanisms determining their turnover have not been established. We found that in differentiating K562 erythroleukemia cells both c-FLIP isoforms were inducibly degraded by the proteasome, but c-FLIP(S) was more prone to ubiquitylation and had a considerably shorter half-life. Analysis of the c-FLIP(S)-specific ubiquitylation revealed two lysines, 192 and 195, C-terminal to the death effector domains, as principal ubiquitin acceptors in c-FLIP(S) but not in c-FLIP(L). Furthermore the c-FLIP(S)-specific tail of 19 amino acids, adjacent to the two target lysines, was demonstrated to be the key element determining the isoform-specific instability of c-FLIP(S). Molecular modeling in combination with site-directed mutagenesis demonstrated that the C-terminal tail is required for correct positioning and subsequent ubiquitylation of the target lysines. Because the antiapoptotic operation of c-FLIP(S) was not affected by the tail deletion, the antiapoptotic activity and ubiquitin-mediated degradation of c-FLIP(S) are functionally and structurally independent processes. The presence of a small destabilizing sequence in c-FLIP(S) constitutes an important determinant of c-FLIP(S)/c-FLIP(L) ratios by allowing differential degradation of c-FLIP isoforms. The conformation-based predisposition of c-FLIP(S) to ubiquitin-mediated degradation introduces a novel concept to the regulation of the death-inducing signaling complex.

CD95 capping is ROCK-dependent and dispensable for apoptosis

Upon engagement, the CD95 receptor is rapidly clustered into cellular 'caps'. This receptor capping is one of the first events to take place following activation and it has been proposed to be important for the initiation of apoptotic signaling. As the biological roles of CD95 capping are still elusive, we explored in detail the role of capping in induction of apoptosis in lymphocytes. CD95 capping was shown to be uncoupled from apoptosis, as apoptosis could occur in the absence of CD95 capping and, vice versa, capping could occur without inducing apoptosis. CD95 capping occurred concomitantly with reorganization of the actin cytoskeleton and aggregation of lipid rafts. While inhibition of actin polymerization and caspase-8 activity had cell type-specific effects on capping in type I and type II cells, the rapid CD95-mediated cellular polarization, as visualized by the orchestrated reorganization of CD95, F-actin and lipid rafts, was shown to be dependent on signaling by Rho kinase (ROCK) in both cell types, however, by distinct activation mechanisms in the respective cell type. CD95 activated RhoA exclusively in the type II cell, whereas ROCK activation was caspase-dependent in the type I cell. Taken together, our results imply that CD95 capping and the subsequent cellular polarization is a ROCK signaling-regulated process that does not correlate with the induction of apoptosis, but is more likely to be involved in the emerging non-apoptotic functions of CD95.

Multicenter phase II study of the oral MEK inhibitor, CI-1040, in patients with advanced non-small-cell lung, breast, colon, and pancreatic cancer

PURPOSE

This multicenter, open-label, phase II study was undertaken to assess the antitumor activity and safety of the oral mitogen-activated extracellular signal regulated kinase kinase (MEK) inhibitor, CI-1040, in breast cancer, colon cancer, non-small-cell lung cancer (NSCLC), and pancreatic cancer.

PATIENTS AND METHODS

Patients with advanced colorectal, NSCLC, breast, or pancreatic cancer received oral CI-1040 continuously at 800 mg bid. All patients had measurable disease at baseline, a performance status of 2 or less, and adequate bone marrow, liver, and renal function. Expression of pERK, pAkt, and Ki-67 was assessed in archived tumor specimens by quantitative immunohistochemistry.

RESULTS

Sixty-seven patients with breast (n = 14), colon (n = 20), NSCLC (n = 18), and pancreatic (n = 15) cancer received a total of 194 courses of treatment (median, 2.0 courses; range, one to 14 courses). No complete or partial responses were observed. Stable disease (SD) lasting a median of 4.4 months (range, 4 to 18 months) was confirmed in eight patients (one breast, two colon, two pancreas, and three NSCLC patients). Treatment was well tolerated, with 81% of patients experiencing toxicities of grade 2 or less severity. Most common toxicities included diarrhea, nausea, asthenia, and rash. A mild association (P < .055) between baseline pERK expression in archived tumor specimens and SD was observed.

CONCLUSION

CI-1040 was generally well tolerated but demonstrated insufficient antitumor activity to warrant further development in the four tumors tested. PD 0325901, a second generation MEK inhibitor, has recently entered clinical development and, with significantly improved pharmacologic and pharmaceutical properties compared with CI-1040, it may better test the therapeutic potential of MEK inhibition in cancer.

p38 MAPK mediates TNF-induced apoptosis in endothelial cells via phosphorylation and downregulation of Bcl-x(L)

The role of p38 mitogen-activated protein kinase (MAPK) in apoptosis is a matter of debate. Here, we investigated the involvement of p38 MAPK in endothelial apoptosis induced by tumor necrosis factor alpha (TNF). We found that activation of p38 MAPK preceded activation of caspase-3, and the early phase of p38 MAPK stimulation did not depend on caspase activity, as shown by pretreatment with the caspase inhibitors z-Val-Ala-Asp(OMe)-fluoromethylketone (zVAD-fmk) and Boc-Asp(OMe)-fluoromethylketone (BAF). The p38 MAPK inhibitor SB203580 significantly attenuated TNF-induced apoptosis in endothelial cells, suggesting that p38 MAPK is essential for apoptotic signaling. Furthermore, we observed a time-dependent increase in active p38 MAPK in the mitochondrial subfraction of cells exposed to TNF. Notably, the level of Bcl-x(L) protein was reduced in cells undergoing TNF-induced apoptosis, and this reduction was prevented by treatment with SB203580. Immunoprecipitation experiments revealed p38 MAPK-dependent serine-threonine phosphorylation of Bcl-x(L) in TNF-treated cells. Exposure to lactacystin prevented both the downregulation of Bcl-x(L) and activation of caspase-3. Taken together, our results suggest that TNF-induced p38 MAPK-mediated phosphorylation of Bcl-x(L) in endothelial cells leads to degradation of Bcl-x(L) in proteasomes and subsequent induction of apoptosis.

Enhanced apoptosis of glioma cell lines is achieved by co-delivering FasL-GFP and TRAIL with a complex Ad5 vector

Brain tumors (BTs) are among the most malignant forms of human cancer. Unfortunately, current treatments are often ineffective and produce severe side effects. Cytotoxic gene therapy is an alternative treatment strategy, with the potential advantages of reduced toxicity to normal brain tissue. Apoptosis-inducing "death ligands" Fas ligand and TNF-related apoptosis-inducing ligand (TRAIL) are genes with substantial cytotoxic activity in susceptible tumor cells. Here, we compared the effectiveness of Ad vector-mediated delivery of Fas ligand-green fluorescent protein (FasL-GFP) fusion protein, human TRAIL, and both genes simultaneously. We examined a panel of 13 cell lines (eight derived from primary isolates) for susceptibility to Ad5-based vector infection and for sensitivity to FasL- and TRAIL-mediated apoptosis. All cell lines were efficiently transduced, but, as expected, varied in their sensitivity to ligand-induced apoptosis. Generally, sensitivity to FasL-GFP correlated with cell surface FasR levels, but no such correlation was seen for TRAIL and its functional receptors, DR4 and DR5. The vector expressing both FasL-GFP and TRAIL was more effective than either of the single-gene vectors at comparable transduction levels, and it was effective against a broader range of cell lines. In five cell lines, coexpression resulted in apoptosis levels greater than those predicted for strictly additive activity of the two death ligands. We believe that Ad vector-mediated delivery of multiple death ligands may be developed as a potential BT therapy, either alone or in conjunction with surgical resection of the primary tumor.

Oral graft-versus-host disease and programmed cell death: pathogenetic and clinical correlates

Graft-versus-host disease (GVHD) is an untoward complication of bone marrow transplantation. It is characterized by an immune-mediated attack by donor immune cells against various host cells and tissues, a process which may be associated with significant morbidity in affected patients. Oral lesions are a common sequelae and can serve as a highly predictive index to the presence of systemic GVHD. The oral lesions of GVHD are clinically and histologically lichenoid in nature and can be a challenge in terms of management. Ulcerated and painful mucosal lesions may represent a significant impediment to normal eating habits and nutritional intake, necessitating appropriate diagnosis and treatment. Importantly, recent evidence has indicated that programmed cell death, or apoptosis, is the major constituent in the pathogenesis of GVHD. Apoptosis not only plays a major role in normal growth and ontogeny, but has been shown to contribute to a wide spectrum of both inflammatory and neoplastic disorders. Since knowledge of apoptotic molecular pathways is requisite for understanding GVHD, the purpose of this paper is to provide a fundamental overview of the predominant apoptotic mechanisms implicated in the pathogenesis of GVHD and to relate these findings to the oral complications of the disease. Finally, we will discuss management strategies for diagnosing and treating the oral lesions of GVHD. By explicating the molecular events in the apoptotic pathway, unique therapeutic and pharmacologic strategies for regulating apoptosis may be developed in the future, reducing the morbidity associated with conditions like GVHD.

Caspase-1 mediates Fas-induced apoptosis and is up-regulated by interferon-gamma in human astrocytoma cells

Resistance to Fas-mediated apoptosis contributes to tumor evasion from the host immune system and enables tumors to mediate alternative responses such as inflammation and angiogenesis. In this study, we investigated the molecular mechanisms of the resistance to Fas-mediated apoptosis and sensitization to Fas-induced cell death by IFN-gamma in human astrocytoma cells. To address this, we investigated the expression of thirty-three genes related to the Fas signal transduction pathways using RNase protection assay in five different human astrocytoma cells. Patterns of expression of these genes were similar between different cell lines and did not correlate with sensitivity to Fas-mediated cell death. Treatment with IFN-gamma increased the mRNA expression of caspases-1, -4 and -7 in addition to those of Fas and TRAIL in a time- and dose-dependent manner. Studies using specific caspase inhibitors showed that Fas-induced cell death was mediated by caspases-1, -3 and 8 in the Fas-sensitive human astrocytoma cell lines, CRT-J and U87-MG. We further demonstrated that these caspases were proteolytically cleaved upon Fas ligation in these cells. Interestingly, caspase-1 protein expression but not that of caspase-3 nor -8 was up-regulated by IFN-gamma only in Fas-sensitive CRT-J cells but not in Fas-resistant U373-MG cells. These results collectively suggest that caspase-1, along with caspases-3 and -8, mediate Fas-induced cell death in human astrocytoma cells, and post-transcriptional regulation of caspase-1 may determine the responsiveness to IFN-gamma-induced sensitization to Fas-mediated apoptosis.

NuMA and nuclear lamins are cleaved during viral infection--inhibition of caspase activity prevents cleavage and rescues HeLa cells from measles virus-induced but not from rhinovirus 1B-induced cell death

Nuclear matrix is a structural framework of important nuclear processes. We studied the effect of two different types of viral infections on nuclear matrix. HeLa cells were infected with human rhinovirus 1B (HRV 1B) or measles virus (MV), and Nuclear Mitotic Apparatus protein (NuMA) and lamins A/C and B were used as markers for internal nuclear matrix and peripheral nuclear lamina, respectively. We show that NuMA, lamins, and poly(ADP-ribose) polymerase-1 are cleaved during viral infection in a virus family-specific manner suggesting that these viruses activate different sets of proteases. Morphologically, NuMA was excluded from the condensed chromatin, lamins showed a folded distribution, and both proteins finally remained around the nuclear fragments. A general caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (z-VAD-FMK) prevented the nuclear disintegration and the cleavage of the proteins studied. Interestingly, z-VAD-FMK rescued MV-infected but not HRV 1B-infected cells from cell death. These results show for the first time that NuMA and lamins are specific target proteins during virus-induced programmed cell death.

Differential regulation of the mitochondrial and death receptor pathways in neural stem cells

Despite an increasing interest in neural stem cell (NSC) research, relatively little is known about the biochemical regulation of cell death pathways in these cells. We demonstrate here, using murine-derived multipotent C17.2 NSCs, that cells undergo mitochondria-mediated cell death in response to apoptotic stimuli such as oxidative stress induced by 2,3-dimethoxy-1,4-naphthoquinone (DMNQ). In particular, treated cells exhibited apoptotic features, including Bax translocation, cytochrome c release, activation of caspase-9 and -3, chromatin condensation and DNA fragmentation. Although C17.2 cells possess the Fas receptor and express procaspase-8, agonistic Fas mAb treatment failed to induce apoptosis. Fas treatment activated the extracellular signal-regulated protein kinase (ERK) pathway, which may have an antiapoptotic as well as a growth stimulating role. Combined, our findings indicate that while NSCs are sensitive to cytotoxic stimuli that involve an engagement of mitochondria, Fas treatment does not induce death and may have an alternative role.

Enhancement of death-receptor induced caspase-8-activation in the death-inducing signalling complex by uncoupling of oxidative phosphorylation

Signalling through the death receptor CD95 induces apoptosis by formation of a signalling complex at the cell membrane and subsequent caspase-8 and caspase-3-activation. Treatment of Jurkat T cells with protonophores across the mitochondrial membrane such as 2,4-dinitrophenol (DNP) enhances the death-inducing capacity of CD95. In this study, we show that this enhancement is due to the specific acceleration of caspase-8-processing and activation at the CD95-receptor. DNP-treatment did not affect NF-kappaB-induction by CD95. Immunoprecipitation experiments showed that the amounts of the adapter FADD/MORT1 and pro-caspase-8 at the CD95-receptor were not altered by DNP. Subcellular fractionation studies revealed that the amount of mature caspase-8 but not pro-caspase at the membrane was increased following CD95-stimulation in the presence of DNP. As a consequence of caspase-activation, c-FLIP-levels in the cytosol decreased. In Jurkat cells overexpressing c-FLIPS, DNP was still able to enhance caspase-activation. The enhancing capacity of DNP was seen in some cell lines (Jurkat, CEM and HeLa) but not in SKW6 cells and was also found in mitogen-stimulated human T cells. Furthermore, the enhancement extended to TRAIL-induced caspase-activation. Thus, a mechanism exists by which caspase-8-activation can be accelerated at death receptors and this mechanism can be triggered by targeting mitochondrial oxidative phosphorylation.